JP2012174805A - Organic transistor, display device, and method of manufacturing organic transistor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an organic transistor having an organic semiconductor layer with an enlarged crystal grain size, an increased high-crystalline region, and an improved carrier mobility, and to provide a display device using the organic transistor, and a method of manufacturing the organic transistor.SOLUTION: An organic transistor is configured by a substrate 1, a gate electrode 2, a gate insulating layer 3, an organic semiconductor layer 5, a source electrode 6, a drain electrode 7, and a crystallization acceleration layer 4 contacting with the organic semiconductor layer 5. The crystallization acceleration layer 4 is configured by at least a second monomolecular film contacting with the organic semiconductor layer 5 and a first monomolecular film contacting with the second monomolecular film. There is a region where an organic molecular skeleton group configuring the second monomolecular film is arranged at a constant inter-centroid distance in at least one direction in a plane. The organic molecular skeleton group configuring the organic semiconductor layer 5 and contacting with at least the region is arranged at a constant inter-centroid distance in at least one direction in a plane.

Description

  The present invention relates to an organic transistor using a thin film made of organic molecules as a component, a display device using the organic transistor, and a method for manufacturing the organic transistor.

  Organic transistors can be used in the production of inorganic semiconductor devices such as silicon without using vacuum processes or high-temperature processes of 200 ° C. or higher, printing techniques such as inkjet and screen methods, spin coating, and casting. The device can be manufactured using a solution process such as the above. Therefore, it is possible to fabricate elements on a large-area substrate or a flexible substrate made of plastic or the like, and has been attracting attention in recent years because it can reduce the manufacturing cost and environmental burden in device fabrication.

However, when the organic semiconductor layer is formed by a solution process, the region where the organic semiconductor molecules are oriented (crystal grains) is small, the film quality of the thin film becomes nonuniform, and it is difficult to improve carrier mobility. As a specific example, in Non-Patent Document 1, an organic semiconductor layer is produced by a solution process using a pentacene thin film that is known to exhibit high mobility among organic semiconductor materials, and used for a field effect transistor. The transistor characteristics in the case of being present are disclosed. However, the mobility is at most about 0.4 cm ² / Vs, which is lower than the mobility (about 1 cm ² / Vs) obtained when an organic semiconductor layer is produced by vacuum deposition using the same material. Inferior in transistor characteristics.

  The reason why the film formed from the solution process shows low mobility is thought to be due to a mixture of multiple factors, but one of them is that it is difficult to control the surface energy of the deposition target substrate. Can be mentioned. When film formation is performed by vacuum deposition, by reducing the surface energy of the substrate, the nucleation density on the initial surface of the substrate decreases, and then molecules that have reached the substrate can easily migrate on the surface of the substrate. Therefore, it is possible to enlarge a region (crystal grain) with uniform orientation. Similar to the inorganic semiconductor material, if the crystal grain is increased, the mobility is improved, so that the mobility of the organic semiconductor can be increased. However, in the case of the solution process, since the factors controlling the surface energy of the organic semiconductor material (solute) and the substrate, or the solution (solvent) and the substrate increase, it becomes difficult to control the crystal grain size.

For example, in the solution process, when the surface energy of the substrate is reduced, the solution repels on the substrate, so that a thin film may be formed only in a local region of the substrate surface. Therefore, it has been difficult to obtain an organic thin film that is wide enough to cover the channel region.
When the surface energy of the substrate is increased, the wettability of the solution is improved, but the nucleation density of the crystal is increased, so that the crystal grain size is small and the thin film has many crystal grain boundaries. As a result, the small crystal grains and crystal grain boundaries become obstacles to carrier movement, leading to a decrease in mobility. In addition, since a polar group exists on the surface of the substrate having a large surface energy, the polar group may function as a trap site for electrons or holes, which also causes a decrease in mobility.
From the above, in order to obtain an organic thin film in which large crystal grains are formed, it is important to appropriately adjust the surface energy of the film formation surface according to the film forming means.

  In addition to controlling the surface energy, it is important to control the crystal state (molecular or atomic arrangement) of the surface (base) on which the organic semiconductor is formed. This is a technique known as epitaxial growth in the field of crystal growth of inorganic semiconductor materials, and a high-quality semiconductor can be obtained by performing crystal growth with the underlying crystal plane aligned with the crystal plane of the semiconductor material to be deposited. The crystal thin film can be obtained. When this technique is applied to a molecular crystal such as an organic semiconductor, it is important that the base has a periodic structure that is the same as or similar to the crystalline state of the organic semiconductor material.

  Based on the above technical background, Patent Document 1 discloses an organic thin film transistor provided with an anchor film in contact with an organic semiconductor layer. This anchor film is composed of a monomolecular film of an organosilane compound having a π-electron conjugated molecule, and has a function of adjusting the surface energy. Further, it is described that the anchor film has crystallinity, and it is disclosed that the crystal grain of the organic semiconductor formed on the surface of the anchor film becomes large and high mobility is expected.

Japanese Patent No. 40658874

Minata et al., “Direct Formation of Pentacene Thin Films by Solution Process”, Synthetic Metals, 2005, Vol. 153, No. 1-3, p. 1-4

However, it is difficult to form the anchor film described in Patent Document 1 so as to have a periodic structure suitable for promoting the crystal growth of the organic semiconductor material, and the crystal grain size of the organic semiconductor layer is increased. There is still room for improvement in expanding the high crystallinity region of the layer and improving the carrier mobility.
The present invention has been made in view of the above circumstances, and an organic transistor having an organic semiconductor layer in which crystal grain size is increased, a region having high crystallinity is increased, and carrier mobility is improved, and the organic transistor is used. It is an object of the present invention to provide a display device and a method for manufacturing the organic transistor.

As a result of diligent research to solve the above-mentioned problems, the inventors of the present invention combined a plurality of organic monomolecular films into a crystal promotion layer, and formed an organic semiconductor layer thereon, thereby forming a crystal grain size of the organic semiconductor layer. It has been found that the carrier mobility can be improved because the region with high crystallinity in the organic semiconductor layer increases, and the present invention has been completed.
That is, the present invention provides an organic transistor, a display device, and an organic transistor manufacturing method having the following characteristics.

(1) An organic transistor comprising a substrate, a gate electrode, a gate insulating layer, an organic semiconductor layer, a source electrode, a drain electrode, and a crystal promotion layer in contact with the organic semiconductor layer,
The crystal promotion layer is composed of at least a second monomolecular film in contact with the organic semiconductor layer and a first monomolecular film in contact with the second monomolecular film,
There is a region where the organic molecular skeleton group constituting the second monomolecular film is arranged at a distance between the centers of gravity equal to at least one direction in the plane,
An organic transistor, wherein organic molecule skeleton groups in contact with at least the region constituting the organic semiconductor layer are arranged at a distance between centers of gravity equal to at least one direction in a plane.
(2) The distance between the center of gravity of the organic molecular skeleton group constituting the first monomolecular film is different from the distance between the center of gravity of the organic molecular skeleton group constituting the second monomolecular film. (1) Organic transistor.
(3) The first monomolecular film includes an organic molecular skeleton connected via a first chemical bond to atoms on a surface on which the first monomolecular film is formed, and the second monomolecular film The film includes an organic molecular skeleton that is connected to the organic molecular skeleton constituting the first monomolecular film via a second chemical bond, and the organic transistor according to (1) or (2) .
(4) The organic transistor according to any one of (1) to (3), wherein at least one of the first monomolecular film and the second monomolecular film is a Langmuir Blodgett film.
(5) The organic transistor according to any one of (1) to (4), wherein the organic molecular skeleton constituting the second monomolecular film is the same as the organic molecular skeleton constituting the organic semiconductor layer.
(6) The organic molecular skeleton constituting the first monomolecular film is aliphatic, and the organic molecular skeleton constituting the second monomolecular film is aromatic (1) to ( 5) The organic transistor in any one of.
(7) The organic molecular skeleton constituting the first monomolecular film is a linear alkane,
(6) The organic transistor according to (6), wherein the organic molecular skeleton constituting the second monomolecular film is fullerene, pentacene or oligothiophene.
(8) A circuit board in which the organic transistor of any one of (1) to (7) is electrically connected, and a liquid crystal or organic electroluminescence in which the organic transistor is electrically connected on the circuit board. A display device comprising: an electrophoretic pixel; and a driver that sends an electric signal to the transistor.
(9) A manufacturing method for manufacturing the organic transistor according to any one of (1) to (7),
A first step of forming the gate electrode and the gate insulating layer on the substrate;
A second step of forming the crystal promotion layer on the surface of the gate insulating layer;
A third step of forming the organic semiconductor layer, the source electrode and the drain electrode on the surface of the crystal promotion layer,
The step of forming the crystal promotion layer in the second step includes the step of forming at least one first monomolecular film in contact with the surface of the gate insulating layer, and the step of forming the first monomolecular film. And a step of forming the second monomolecular film in contact with the surface.
(10) A manufacturing method for manufacturing the organic transistor according to any one of (1) to (7),
A first step of forming the gate electrode and the gate insulating layer on the substrate;
A second step of forming the source electrode and the drain electrode on the surface of the gate insulating layer;
After forming the crystal promotion layer at least on the surface of the gate insulating layer, or on the surface of the gate insulating layer, the source electrode, and the drain electrode, the method further includes a third step of forming the organic semiconductor layer. ,
The step of forming the crystal promotion layer in the third step includes at least the surface of the gate insulating layer, or the first monomolecular film in contact with the surface of the gate insulating layer, the source electrode, and the drain electrode. A method for producing an organic transistor, comprising: forming at least one layer, and forming the second monomolecular film in contact with the surface of the first monomolecular film.
(11) The step of forming the first monomolecular film connects the atoms on the surface of the gate insulating layer and the organic molecular skeleton constituting the first monomolecular film through a first chemical bond. Including steps,
The step of forming the second monomolecular film comprises a second chemical bond between an organic molecular skeleton constituting the first monomolecular film and an organic molecular skeleton constituting the second monomolecular film. (9) The manufacturing method of the organic transistor of (10) characterized by including the process of connecting via.
(12) A manufacturing method for manufacturing the organic transistor according to any one of (1) to (7),
A first step of forming the crystal promotion layer on the substrate;
A second step of forming the organic semiconductor layer, the source electrode and the drain electrode in any order on the surface of the crystal promotion layer;
A third step of forming the gate insulating layer and the gate electrode at least on the surface of the organic semiconductor layer,
The step of forming the crystal promotion layer of the first step includes the step of forming at least one layer of the first monomolecular film in contact with the surface of the substrate, and the surface of the first monomolecular film. And a step of forming the second monomolecular film in contact with the organic transistor.
(13) The step of forming the first monomolecular film includes a step of connecting atoms on the substrate surface and an organic molecular skeleton constituting the first monomolecular film via a first chemical bond. Including
The step of forming the second monomolecular film comprises a second chemical bond between an organic molecular skeleton constituting the first monomolecular film and an organic molecular skeleton constituting the second monomolecular film. (12) The manufacturing method of the organic transistor characterized by including the process of connecting via.
(14) The step of forming the first monomolecular film is a single molecule composed of an organic molecule having a linear alkane as an organic molecular skeleton through a siloxane bond or a phosphate ester bond as the first chemical bond. A step of forming a film,
The step of forming the second monomolecular film is a step of forming fullerene, pentacene, or oligothiophene through the amine bond, imine bond, or triazole ring as the second chemical bond. The manufacturing method of the organic transistor of (11) or (13).
(15) A step of forming a monomolecular film by a Langmuir Blodget method in any one of the step of forming the first monomolecular film and the step of forming the second monomolecular film. (9) The manufacturing method of the organic transistor in any one of (14) characterized by the above-mentioned.
(16) The formation of the organic semiconductor layer includes a step of dissolving an organic semiconductor material in a solvent to form a solution, and a step of applying the solution to the surface of the crystal promotion layer (9) to (9) The method for producing an organic transistor according to any one of 15).
(17) Any one of the step of forming the first chemical bond and the step of forming the second chemical bond is any one of a solution immersion method, a gas phase reaction method, and a spin coating method. The method for producing an organic transistor according to any one of (9) to (16), wherein the method is used.

In the organic transistor of the present invention, it is possible to realize a crystal promotion layer having a periodic structure similar to the periodic structure of a single crystal of an organic semiconductor material because the crystal promotion layer is composed of a plurality of monomolecular films. The crystal grain size of the organic semiconductor layer formed in contact therewith increases, and the region having high crystallinity increases in the organic semiconductor layer, so that carrier mobility can be improved. Because it is composed of a monomolecular film, a complex molecular structure and complicated synthesis are required when a single molecule has crystal accelerating ability by selecting simple molecular structures and combining them easily on a substrate. Thus, a crystal promotion layer having a desired structure can be obtained.

Specific examples of the organic transistor of the present invention ((a) bottom gate, top contact type, (b) bottom gate, bottom contact type, (c) top gate, top contact type, (d) top gate, bottom contact type) It is the schematic shown respectively. It is a schematic diagram which shows adsorption | suction of a molecule | numerator. It is a schematic diagram which shows the specific example of the crystal promotion layer of this invention, Comprising: When the (a) 1st monomolecular film is comprised from one layer, (b) The 1st monomolecular film has multiple layers (n layer) The crystal promotion layers in the case of being composed of It is a schematic diagram which shows the formation method of the crystal promotion layer of this invention. It is the (a) schematic diagram of an organic transistor of a 1st aspect, (b) The schematic diagram of a crystal promotion layer, (c) Sectional drawing of a crystal promotion layer, and (d) The schematic diagram which shows molecular arrangement | positioning. It is the (a) schematic diagram of a 2nd aspect, (b) The schematic diagram of a crystal promotion layer, and (c) The schematic diagram which shows molecular arrangement | positioning. It is the schematic diagram of (a) organic transistor of 3rd aspect, and (b) crystal | crystallization promotion layer. It is the (a) schematic diagram of a 4th aspect, (b) The schematic diagram of a crystal acceleration layer, and (c) The schematic diagram which shows molecular arrangement | positioning. It is the (a) schematic diagram of a liquid crystal display device of a 5th aspect, and (b) It is sectional drawing of a pixel. It is the photograph (a) and optical microscope photograph (b) of the glass substrate in which the organic-semiconductor layer was formed in Example 1. FIG. It is the photograph (a) and optical microscope photograph (b) of the glass substrate in which the organic-semiconductor layer was formed in the comparative example 1.

<Organic transistor>
The organic transistor of the present invention includes a substrate, a gate electrode, a gate insulating layer, an organic semiconductor layer, a source electrode, a drain electrode, and a crystal promotion layer in contact with the organic semiconductor layer.
Hereinafter, specific examples of the organic transistor having the above structure will be described with reference to the drawings. The organic transistor of the present invention is not limited to the following specific examples.
The organic transistor shown in FIG. 1A is a bottom-gate and top-contact type organic transistor, which is formed on a substrate 1 with a gate electrode 2, a gate insulating layer 3, a crystal promotion layer 4, and a crystal promotion layer 4. The organic semiconductor layer 5, the source electrode 6 and the drain electrode 7 which are in contact with each other are provided in this order.
The organic transistor shown in FIG. 1B is a bottom-gate and bottom-contact type organic transistor, which has a gate electrode 2, a gate insulating layer 3, a source electrode 6, a drain electrode 7, and crystal promotion on a substrate 1. The organic semiconductor layer 5 in contact with the layer 4 and the crystal promotion layer 4 is provided in this order.
The organic transistor shown in FIG. 1C is a top-gate type and top-contact type organic transistor, and includes a crystal promotion layer 4, an organic semiconductor layer 5 in contact with the crystal promotion layer 4, and a source electrode on the substrate 1. 6, the drain electrode 7, the gate insulating layer 3, and the gate electrode 2 are provided in this order.
The organic transistor shown in FIG. 1D is a top-gate and bottom-contact type organic transistor that is in contact with the crystal promotion layer 4, the source electrode 6, the drain electrode 7, and the crystal promotion layer 4 on the substrate 1. The organic semiconductor layer 5, the gate insulating layer 3, and the gate electrode 2 are provided in this order.
The organic transistor according to the present invention is a bottom gate type in which the gate electrode 2 is on the substrate 1 (for example, FIGS. 1A and 1B), but the top electrode in which the gate electrode 2 is on the gate insulating layer 3. It may be a mold (for example, FIGS. 1C and 1D). Even in the top contact type in which the source electrode 6 and the drain electrode 7 are formed on the organic semiconductor layer 5 (for example, FIGS. 1A and 1C), the source electrode 6 and the drain electrode 7 are the organic semiconductor layer. 5 may be a bottom contact type (for example, FIGS. 1B and 1D) formed in the lower portion, or may be another type of organic transistor.
Hereinafter, each component will be described in detail.

In this invention, the board | substrate 1 is not specifically limited, What is normally used as a board | substrate of organic devices, such as an organic transistor, can be used. Specifically, for example, a metal substrate such as aluminum or iron; an inorganic material substrate other than a metal such as silicon, quartz, or glass; an organic resin material substrate such as polycarbonate, polyetheretherketone, polyimide, polyester, or polyethersulfone; Can be mentioned. Among these, an organic resin material substrate is preferable in consideration of application to a flexible device.
The substrate 1 may be formed by forming an electrode such as ITO, gold, silver, copper, platinum, or chromium on the surface, and another thin film is formed on the surface of the substrate or the electrode formed on the substrate. It may be what you did. Examples of the other thin film include a gate insulating film made of silicon dioxide or the like.

In the present invention, the gate electrode 2, the source electrode 6, and the drain electrode 7 are not particularly limited, and those usually used for these electrodes of a transistor can be used. Specifically, for example, gold (Au), silver (Ag), copper (Cu), platinum (Pt), palladium (Pd), iron (Fe), aluminum (Al), tantalum (Ta), chromium (Cr) Metal materials such as indium tin oxide (ITO), zinc oxide (ZnO), tin oxide (SnO ₂ ) and other oxide conductors; transparent conductive material composed of indium oxide and zinc oxide, which are a kind of oxide conductors Etc. Further, an electrode made of an organic material such as polyaniline or polythiophene, or an electrode formed by applying a conductive ink can also be used.

In the present invention, the gate insulating layer 3 is not particularly limited, and a material usually used for a gate insulating layer of a transistor can be used. Specifically, for example, inorganic oxides such as silicon dioxide (SiO ₂ ), aluminum oxide (Al ₂ O ₃ ), and tantalum oxide (Ta ₂ O ₅ ); polyimide, polyethylene, polyethylene naphthalate, polyvinylphenol and the like And polymer materials.
In particular, when the crystal promotion layer 4 is formed in contact with the gate insulating layer 3 (for example, in the case of FIGS. 1A and 1B), the gate insulating layer 3 includes silicon dioxide (SiO ₂ ), It is preferable to use a material in which a hydroxyl group is exposed on the surface, such as aluminum oxide (Al ₂ O ₃ ), polyvinyl alcohol, and polyvinylphenol.

  In the present invention, the crystal promotion layer 4 is composed of at least a second monomolecular film in contact with the organic semiconductor layer 5 and a first monomolecular film in contact with the second monomolecular film.

As described above, in order to increase the crystal grain size of the organic semiconductor layer, increase the highly crystalline region in the organic semiconductor layer, and improve the carrier mobility, the crystal promotion that promotes the crystal growth of the organic semiconductor layer. Providing a layer (anchor film) is considered effective. As such a crystal promotion layer, as shown in FIG. 2A, a monomolecular film made of a single molecule in which organic molecular skeleton groups constituting the monomolecular film are arranged at equal distances between the centers of gravity can be considered.
More specifically, for example, the organic molecular skeletons are spontaneously aggregated by van der Waal forces in the organic molecular skeleton group constituting the monomolecular film, whereby the distance between the centers of gravity can be made equal. In this case, the distance between the centers of gravity is determined by the size of the organic molecular skeleton constituting the monomolecular film. In such a monomolecular film, the organic molecular skeleton in the monomolecular film has a desired periodic structure (the distance between the centers of gravity of the organic molecular skeleton groups constituting the monomolecular film adjacent in the monomolecular film is regular. Structure). However, when a monomolecular film made of a single molecule is used for the crystal promotion layer, it is difficult to control the periodic structure, and it is difficult to produce a periodic structure close to the periodic structure of a single crystal of an organic semiconductor material. It was.

In addition, when using the monomolecular film as described above as a crystal promotion layer of an organic transistor, it is necessary to form a crystal promotion layer that does not peel off even under the solution coating process and vacuum conditions when forming the organic semiconductor layer. The layer needs to be securely bonded or adsorbed on the lower layer (hereinafter referred to as “lower layer”) that forms the crystal promotion layer.
That is, when the monomolecular film is bonded or adsorbed to the lower layer, the periodic structure of the organic molecular skeleton in the monomolecular film includes not only the size of the organic molecular skeleton but also the position and number of bonding or adsorption sites on the lower layer surface. Also involved.
However, it is difficult to control the position or number of bonding or adsorption sites on the lower surface, and these actual sites are considered to be random as shown by the black circles in the left diagram of FIG. Therefore, as shown in the right diagram of FIG. 2B, even if the size of the organic molecular skeleton in the monomolecular film is appropriate, the organic molecular skeleton cannot be arranged at an appropriate position, and the organic semiconductor It was difficult to produce a periodic structure close to that of a single crystal material.

  Therefore, in the present invention, the above problem is solved by assuming that the crystal promotion layer 4 is composed of at least a plurality of monomolecular films including a first monomolecular film and a second monomolecular film. As shown in FIG. 2 (c), even if the binding sites on the lower layer surface (black circles in FIG. 2 (c)) are random, the first monomolecular film bound to the random binding sites It is possible to adjust the position and number of the binding sites of the second monomolecular film, and the second monomolecular film directly in contact with the organic semiconductor layer 5 is made of an organic semiconductor material suitable for crystal growth of the organic semiconductor layer. A periodic structure close to that of a single crystal can be retained. This makes it possible to increase the crystal grain size of the organic semiconductor layer, increase the highly crystalline region in the organic semiconductor layer, and improve carrier mobility.

Hereinafter, a specific example of the crystal promotion layer 4 will be described with reference to the drawings. The crystal promotion layer 4 of the present invention is not limited to the following specific examples.
FIG. 3A is a schematic diagram showing an example of the crystal promotion layer 4, and the crystal promotion layer 4 in FIG. 3A includes a first monomolecular film 42 and a second monomolecular film 44. And the substrate 1 or the gate insulating layer 3 and the first organic molecular skeleton constituting the first monomolecular film 42 are connected via the first chemical bond 41, and the first monomolecular film is formed. The first organic molecular skeleton constituting the second organic molecular skeleton constituting the second monomolecular film 44 is connected through the second chemical bond 43. Note that the first organic molecular skeleton is connected through the first chemical bond 41 is not limited to the substrate 1 or the gate insulating layer 3, but is a layer located under the crystal promotion layer 4, A film, a support, etc. (crystal promotion layer underlayer) may be used and can be appropriately determined according to the configuration of the organic transistor.

  In the present invention, the first monomolecular film 42 is a monomolecular film in contact with the second monomolecular film 44. The organic molecular skeleton constituting the first monomolecular film 42 is not particularly limited, and the organic molecular skeleton normally used for forming the organic monomolecular film has characteristics required for the first monomolecular film 42. The organic molecular skeleton may be aliphatic or aromatic.

Specific examples of the first monomolecular film 42 whose organic molecular skeleton is aliphatic include those containing an aliphatic hydrocarbon group as a main chain skeleton. In the present invention, “aliphatic” is a relative concept with respect to aromatics, and means a group or a compound having no aromaticity.
The aliphatic hydrocarbon group may be saturated or unsaturated, but is usually preferably saturated. Further, the aliphatic hydrocarbon group may be chain-like or cyclic.
The chain aliphatic saturated hydrocarbon group may be linear or branched.
Examples of the linear aliphatic saturated hydrocarbon group include methylene group, ethylene group, trimethylene group, tetramethylene group, pentamethylene group, heptamethylene group, octamethylene group, nonamethylene group, decamethylene group, undecamethylene group, dodecamethylene group. A linear hydrocarbon group represented by — (CH ₂ ) _p — such as a methylene group (wherein p is an integer of 1 to 20) is preferable.
As the branched aliphatic saturated hydrocarbon _{group, - [C (CH 3)} 2] q -, - [C (CH 3) (CH 2 CH 3)] q -, - [C (CH 3) ( CH ₂ CH ₂ CH ₃ )] _q -,-[C (CH ₂ CH ₃ ) ₂ ] _q- (wherein q is an integer of 1 to 20), alkylmethylene groups, alkylethylene Group, alkyltrimethylene group, alkyltetramethylene group and the like are preferable.

Examples of the cyclic aliphatic hydrocarbon group include a group obtained by removing two hydrogen atoms from a monocycloalkane such as cyclopentane, cyclohexane, cycloheptane, and cyclooctane, and a polycycloalkane such as decalin, adamantane, and norbornane. Examples include groups in which two atoms have been removed.
In the aliphatic hydrocarbon group, part or all of the hydrogen atoms thereof may be substituted with a substituent. Examples of the substituent include a halogen atom such as a fluorine atom and a chlorine atom; a halogenated alkyl group in which part or all of the hydrogen atom is substituted with the halogen atom; an oxygen atom and the like. Further, when the aliphatic hydrocarbon group is cyclic, it may have a chain alkyl group as a substituent. Examples of the chain alkyl group include a methyl group, an ethyl group, a propyl group, and a t-butyl group.
In addition, in the aliphatic hydrocarbon group, a part of the carbon atoms constituting the skeleton and the ring are —O—, —C (═O) —, —C (═O) —O—, —O—C ( ═O) —O— or the like may be substituted.

Specifically, the first monomolecular film 42 having an aliphatic organic molecular skeleton preferably includes an aromatic hydrocarbon ring or an aromatic heterocycle (aromatic heterocycle) as a main skeleton.
As those containing an aromatic hydrocarbon ring, hydrogen atoms bonded to two different carbon atoms constituting benzene, toluene, xylene, mesitylene, indene, naphthalene, anthracene, phenanthrene, naphthacene, pentacene, hexacene, C60 fullerene, etc. Examples thereof include a group obtained by removing two groups, or a group formed by repeating these groups.
Aromatic heterocycles include, for example, furan, thiophene, pyrrole, imidazole, pyran, pyridine, pyrimidine, pyrazine, indole, purine, quinoline, isoquinoline, hydrogen atoms bonded to two different carbon atoms And a group formed by repeating these groups.
Among the aromatic hydrocarbon rings and aromatic heterocycles mentioned above, it is preferable to have a group in which two hydrogen atoms bonded to two different carbon atoms constituting the ring of benzene or pyridine are removed.

In the present invention, the first monomolecular film 42 preferably has an aliphatic organic molecular skeleton. Even when the first monomolecular film 42 is arranged on the lower layer at random binding sites by using an aliphatic organic molecule having a higher flexibility as compared with an aromatic group as the organic molecular skeleton, The organic molecular skeleton constituting the molecular film 44 can be freely arranged. Especially, since it is more excellent in a softness | flexibility, it is more preferable that linear alkane (Preferably C6-C20, More preferably C10-C20) is included as an organic molecular skeleton.
Further, the distance between the centers of gravity of the organic molecular skeleton group constituting the first monomolecular film 42 of the present invention is preferably different from the distance between the centers of gravity of the organic molecular skeleton group constituting the second monomolecular film 44. Details will be described later.

In the present invention, the first monomolecular film 42 may be laminated in a plurality of layers. The plurality of first monomolecular films 42 may be the same or different.
When two or more layers of the first monomolecular film 42 are laminated, the first chemistry described later is provided between the plurality of first organic molecular skeletons constituting the plurality of first monomolecular layers 42. It is preferably connected by a bond 41.
FIG. 3B is a schematic view showing an example of the crystal promotion layer 4 in which a plurality of (n layers) first monomolecular films 42 are stacked, and the crystal promotion layer 4 in FIG. Except that the first organic molecular skeleton constituting the first monomolecular film 42 is connected via the first chemical bond 41, the first monomolecular film 42 of the layer. This is the same as FIG.

In the present invention, the first monomolecular film 42 is in contact with the second monomolecular film at one end thereof. As shown in FIG. 3A, the contact point between the first monomolecular film 42 and the second monomolecular film 44 is formed through a chemical bond (second chemical bond 43 in FIG. 3). The organic molecular skeleton constituting one monomolecular film 42 and the organic molecular skeleton constituting the second monomolecular film 44 may be connected. The second chemical bond 44 will be described later.
Further, the other end of the first monomolecular film 42 has atoms on the surface (lower surface) on which the first monomolecular film is formed via the first chemical bond 41 as shown in FIG. And the organic molecular skeleton constituting the first monomolecular film 42 are preferably connected.
In addition, when there are a plurality of first monomolecular films 42 as shown in FIG. 3B, “the other end of the first monomolecular film 42” refers to the plurality of first monomolecular films 42. , The end of the first monomolecular film 42 that is farthest from the second monomolecular film 44.

  The first monomolecular film 42 of the present invention may be a Langmuir Blodgett film. When the first monomolecular film 42 is a Langmuir Blodgett film, the first monomolecular film may be formed on the lower layer without the first chemical bond 41 (this form is not shown). )

In the present invention, the first chemical bond 41 is not particularly limited, and can be appropriately determined according to the lower layer member and type. Specifically, a thiol group (—SH), a silane coupling group (—SiR ′ ₃ ), a phosphonic acid group (—POR ″ ₂ ), a carboxylic acid group (—COR ″), or a sulfonic acid group (—SO _3). R ″) (wherein R is —OCH ₃ , —OCH ₂ —CH ₃ , —Cl, R ″ is —OH, —Cl), and the like. preferable. Among them, the siloxane bond obtained from the silane coupling group and the hydroxyl group, and the phosphate ester bond obtained from the phosphonic acid group and the hydroxyl group can be firmly bonded to the underlying member, and are obtained by the second monomolecular film. Since the periodic structure to be stabilized is preferable. Further, if a metal-thiol bond obtained from a thiol group and a metal atom (for example, gold, silver, platinum, copper) is used, the lower layer can be applied to an electrode material.

  In the present invention, the second monomolecular film 44 is a monomolecular film in contact with the organic semiconductor layer 5 and the first monomolecular film 42. The organic molecular skeleton constituting the second monomolecular film 44 is not particularly limited, and an organic molecular skeleton normally used as the organic monomolecular film is selected according to the characteristics required for the second monomolecular film 44. The organic molecular skeleton may be aliphatic or aromatic.

Specific examples of the second monomolecular film 44 whose organic molecular skeleton is aliphatic or aromatic include those similar to the first monomolecular film 42 whose organic molecular skeleton is aliphatic or aromatic.
In the present invention, the second monomolecular film 44 preferably has an aromatic main chain skeleton. By using an aromatic main chain skeleton having π electrons, the cohesive force due to π-π interaction works between adjacent organic molecular skeletons in the second monomolecular film 44, and the molecules spontaneously aggregate, Arrangement is preferable because a periodic structure can be easily obtained. In particular, when the first monomolecular film 42 has an aliphatic main chain skeleton and the second monomolecular film 44 has an aromatic main chain skeleton, the above-described aliphatic flexibility and aromaticity can be obtained. Due to the two effects of the group π-π interaction, a periodic structure is more easily formed in the second monomolecular film 44.

  Further, in the present invention, the second monomolecular film 44 is arranged with the distance between the centers of gravity equal to at least one direction in the plane in the horizontal direction with respect to the substrate in which the organic molecular skeleton group constituting the second monomolecular film 44 is arranged The region has a grain. As described above, by arranging the organic molecular skeleton groups constituting the second monomolecular film 44 at the same distance between the centers of gravity, the organic semiconductor layer 5 as an upper layer thereof has the periodic structure of the second monomolecular film. To form a periodic structure. Further, since crystal growth is promoted in the region where the second monomolecular film is arranged, a large grain is generated at least in the upper layer of the region where the second monomolecular film is arranged. As a result, a region with high crystallinity in the organic semiconductor layer is increased, and good carrier mobility can be obtained. That is, it is necessary that the organic molecular skeleton groups constituting the second monomolecular film 44 are arranged at equal center-to-center distances to form a periodic structure that promotes good crystal growth of the organic semiconductor layer 5. Note that the arrangement of the organic molecular skeleton group constituting the second monomolecular film 44 does not have to exist over the entire surface of the second monomolecular layer 44, and is a region that needs to have high crystallinity in the organic transistor. Only a channel region or a partial region of the channel region may be arranged. Even if the arranged region is a part of the channel region, the crystal grain size of the organic semiconductor layer in contact with the arranged region becomes large. As a result, the carrier mobility is improved.

Here, in order to arrange the organic molecular skeleton groups constituting the second monomolecular film 44 at a distance between the centroids equal to at least one direction, the centroids of the organic molecular skeleton groups constituting the first monomolecular film 42 are arranged. It is preferable that the distance and the distance between the centers of gravity of the organic molecular skeleton group constituting the second monomolecular film 44 are different.
In the present invention, the distance between the centers of gravity of two organic molecular skeleton groups is different when the two organic molecular skeleton groups are subjected to the same conditions (for example, van der Waals between organic molecular skeletons constituting a monomolecular film). The distance between the centroids of the organic molecular skeleton group when aligned in the most densely aligned condition according to the force, or when aligned on the water surface by the Langmuir-Blodget method and transferred to the substrate under the same surface pressure. Means different. The distance between the centers of gravity of the organic molecular skeleton group can be measured using a known apparatus by an X-ray diffraction (XRD in-plane) method in the in-plane direction of the film, as shown in an embodiment described later. Further, the distance between the centers of gravity can be predicted in advance by estimating the most stable structure of the organic molecular skeleton by a density functional method or the like (for example, B3LYP 6-31G d, p level).

The distance between the centroids of the organic molecular skeleton group constituting the first monomolecular film 42 is different from the distance between the centroids of the organic molecular skeleton group constituting the second monomolecular film 44, whereby the first monomolecular film The position and number of binding sites are controlled between 42 and the second monomolecular film 44, the arrangement of the organic molecular skeleton group constituting the second monomolecular film 44 is optimized, and the second monomolecular film 44 can obtain a desired periodic structure.
Specifically, the organic molecular skeleton constituting the first monomolecular film 42 is an aliphatic hydrocarbon group, and the organic molecular skeleton constituting the second monomolecular film 44 is an aromatic hydrocarbon group. Preferably, the organic molecular skeleton constituting the first monomolecular film 42 is a linear alkane (preferably having 6 to 20 carbon atoms, more preferably 10 to 20 carbon atoms), and the second monomolecular film 44 is It is more preferable that the organic molecular skeleton to be formed is fullerene, pentacene, oligothiophene, or naphthalene (more preferably fullerene, pentacene, or oligothiophene). By using the above combination, the distance between the centers of gravity of the organic molecular skeleton groups constituting the first monomolecular film 42 and the second monomolecular film 44 is different, so that the second monomolecular film 44 is constructed. The organic molecular skeleton group to be formed has a region arranged with a distance between the centers of gravity equal to at least one direction in the plane.

Furthermore, in the present invention, it is preferable that the organic molecular skeleton group constituting the second monomolecular film 44 and the organic molecular skeleton group constituting the organic semiconductor layer 5 have the same or similar center-to-center distance.
With this configuration, the organic molecular skeleton group of the organic semiconductor layer 5 can easily follow the arrangement of the organic molecular skeleton group of the second monomolecular film 44, and crystal growth is promoted. The grain size is increased, and the region having high crystallinity of the organic semiconductor layer 5 is increased, and the carrier mobility is improved.

More preferably, in addition to the above structure, the second monomolecular film 44 and the organic semiconductor layer 5 preferably have the same or similar surface energy.
By having this configuration, the wettability of the organic semiconductor layer 5 is improved, and a layered crystal is formed in the organic semiconductor layer 5, so that the crystal grain size of the organic semiconductor layer 5 can be further increased. (As for the relationship between surface energy, crystal grain size, and mobility, Kamada et al., “Effect of Interface on Characteristics of Organic Field Effect Transistor”, Surface Science, 2003, Vol. 24, No. No. 2, pages 69-76).
A preferred combination of the organic molecular skeleton of the second monomolecular film 44 and the organic molecular skeleton of the organic semiconductor layer 5 for producing the above configuration will be described later.

In the present invention, the second chemical bond 43 is not particularly limited, and is used for film formation, the terminal functional group of the organic molecule having the organic molecular skeleton of the second monomolecular film 44, and the film formation. It can be appropriately determined according to the terminal functional group of the organic molecule having the organic molecular skeleton of the first monomolecular film 42. For example, if an organic molecule having an azide group (—N ₃ ) at the end is used for forming the first monomolecular film 42, ethenyl contained in fullerene or the like is used for forming the second monomolecular film 44. When an organic molecule having a group (—C═C) at the terminal is used, an amine bond (—N <) is formed as the second chemical bond 43. Specific examples of combinations of terminal functional groups and bonds to be formed are shown in Table 1. In addition, it is also possible to use an ether bond, an ester bond, an imide bond, a urethane bond, a urea bond, a siloxane bond, or a phosphate ester bond. Among these, the triazole ring is preferable because it has a high bonding force because it is structurally stable. Note that either functional group 1 or functional group 2 in the table may be bonded to the organic molecule on the first monomolecular film 42 side.

In this invention, the organic-semiconductor layer 5 is not specifically limited, Usually, the material used for the organic-semiconductor layer of an organic transistor can be used.
Specifically, for example, when the organic semiconductor layer 5 is a p-type semiconductor layer, the organic semiconductor layer 5 is composed of pentacene, rubrene, oligothiophene, polythiophene, dinaphthothiophene, and alkyl substitution products thereof. It can be used as an organic molecular skeleton. If the organic semiconductor layer 5 is an n-type semiconductor layer, it is preferable to use C60 fullerene, fluorinated pentacene, or a perylene imide compound as the organic molecular skeleton constituting the organic semiconductor layer 5.
Among these, pentacene and C60 fullerene are preferable because they have high carrier mobility and can realize high-speed operation of the organic transistor.

Further, as described above, in the present invention, the organic molecular skeleton group constituting the organic semiconductor layer 5 and the organic molecular skeleton group constituting the second monomolecular film 44 have the same or similar distance between the centers of gravity. It is preferable that the second monomolecular film 44 and the organic semiconductor layer 5 have the same or similar surface energy.
First, the distance between the centroids of the organic molecular skeleton that can constitute the organic semiconductor layer 5 is shown in Table 2, and the distance between the centroids of the organic molecular skeleton that can constitute the second monomolecular film 44 (the first monomolecular film 42 is directly Table 3 shows the case of a chain alkane. The distance between the centers of gravity of the organic molecular skeletons shown in Table 2 is a lattice constant in the three axis directions of the a-axis, b-axis, and c-axis when each organic semiconductor material forms a single crystal. Referenced (the unit of the numerical value is nm). The distance between the centers of gravity shown in Table 3 was calculated from the following method.
First, the most stable structure of the organic molecular skeleton constituting the first monomolecular film and the second monomolecular film was estimated using calculation software Gaussian 09 (density functional method B3LYP 6-31G d, p level). Next, a model was constructed in which the organic molecular skeleton constituting the first monomolecular film having the most stable structure was oriented in the direction perpendicular to the substrate and arranged in a hexagonal close-packed manner on the substrate surface. Further, the organic molecular skeleton constituting the second monomolecular film is oriented in the direction perpendicular to the substrate at the binding site on the modeled first monomolecular film, and the organic molecular skeletons overlap each other. A model arranged in close-packing was assembled, and the distance between centroids of the organic molecular skeleton constituting the second monomolecular film at that time was defined as the distance between centroids in Table 3 (the unit of numerical values is nm).

Non-Patent Document 2: Acta Crystallographica Section C C57 (2001) 939 Matthues et al. (Single Crystal Structure of Pentacene)
Non-Patent Document 3: Applied Physics Letters 91 (2007) 063514 Park et al. (Single Crystal Structure of Tips-Pentacene)
Non-Patent Document 4: Science 303 (2004) 1644 Sunder et al. (Single crystal structure of rubrene)
Non-Patent Document 5: Journal of The American Chemical Society 129 (2007) 2224 Takimiya et al. (Single Crystal Structure of Dinaphthothienothiophene)
Non-Patent Document 6: Physical Review Letters 66 (1991) 2911 Heiney et al. (Single crystal structure of fullerene)
Non-Patent Document 7: Journal of The American Chemical Society 126 (2004) 8138 Sakamoto et al. (Single Crystal Structure of Fluoropentacene)
Non-Patent Document 8: Acta Cryst. C42 (1986) 189 Hadicke et al. (Crystal Structure of Peryleneimide Derivative)

Of the three distances between the centers of gravity shown in Table 2, the underlined one has the shortest distance, and the carrier transport efficiency is high (the transfer integral is large). Therefore, the distance between the centers of gravity of the second monomolecular film 44 in contact with the organic semiconductor layer 5 is preferably the same as or close to (similar to) the underline value in Table 2, and the underline value in Table 2 and More preferably, the distance between the centroids is the same as or close to the other one value (in two axial directions in total).
From the values in Tables 2 to 3, when the organic molecular skeleton constituting the second monomolecular film 44 and the organic molecular skeleton constituting the organic semiconductor layer 5 are the same (for example, 2 in Table 2 and B in Table 3; It can be seen that it is preferable because the distance between the centers of gravity of both of 5 in Table 2 and A) in Table 3 is very close. Further, according to Tables 2 and 3, even if the organic molecular skeleton constituting the second monomolecular film 44 and the organic molecular skeleton constituting the organic semiconductor layer 5 are different, for example, 1 in Table 2 a, b axes and C in Table 3; b and c axes in Table 2 and E in Table 3; 4 a and b axes in Table 2 and C in Table 4; 6 b and c axes in Table 2 There are cases where the distance between the centers of gravity is short, as shown in Table 3, D; Even in such a case, since the distance between the centers of gravity is short, crystal growth of the organic molecular skeleton group constituting the organic semiconductor layer can be promoted. Combinations having the same or close distance between the centers of gravity are not limited to those in the above table, and the distance between the centers of gravity can be measured or predicted by the above-described method, and the same or close combination of the distances between the centers of gravity can be appropriately selected.

  In terms of the second monomolecular film 44 and the organic semiconductor layer 5 having the same or similar surface energy, the organic molecular skeleton and the organic semiconductor 5 constituting the second monomolecular film 44 are configured. Since the surface energy is the same or approximate when the organic molecular skeleton is the same, it is preferable. In addition to the same skeleton, the surface energy can be approximated if the organic molecular skeleton constituting the second monomolecular film has π electrons. Furthermore, the surface energy can also be controlled by controlling the density of the organic molecular skeleton that constitutes the second monomolecular film, so the density can be controlled even for organic molecular skeletons that do not have π electrons. Can be approximated.

  In the present invention, the method for forming the crystal promotion layer 4 is not particularly limited as long as the first monomolecular film 42 and the second monomolecular film 44 are suitably formed. As shown in FIG. 4, a solution dipping method, a gas phase reaction method, a spin coating method, a dip method using the first monomolecular film 42 forming material on the lower layer (the substrate 1 or the gate insulating layer 3 in the figure). After the first monomolecular film 42 is formed by the coating method, the Langmuir Blodget method, etc., the second monomolecular film is formed on the first monomolecular film 42 using the second monomolecular film 44 forming material. By forming, the crystal promotion layer 4 of the present invention is obtained.

  In the case of the solution immersion method, specifically, for example, a functional group used for the first chemical bond is bonded to one end of the organic molecular skeleton forming the first monomolecular film 42 and the second chemical bond is bonded to the other end. An organic molecule (first organic molecule) to which a functional group to be used is bonded is prepared in advance. After dissolving the first organic molecule in a solvent and making it into a solution, the substrate having the lower layer on the surface is immersed in the dissolved solution, and left standing or stirring at a temperature of about 0 to 100 ° C. After the bond is formed, the first monomolecular film 42 is formed on the lower layer by washing away the excess material with a solvent. This method has an effect that a monomolecular film can be easily formed without requiring a special apparatus. In addition, the obtained monomolecular film is a film having high intermolecular interaction and high orientation.

  In the case of the gas phase reaction method, specifically, for example, a solution in which the same first organic molecule as described above is dissolved and a substrate having a lower layer on the surface are sealed in a sealed container so as not to be in direct contact with each other. By heating the sealed container to about 50 to 150 ° C. to volatilize the first organic molecules, adhere to the lower layer surface, and form the first chemical bond, the excess material is washed away with a solvent. The first monomolecular film 42 is formed on the lower layer surface. According to this method, since the heating is performed, the reaction proceeds rapidly and the formation time can be shortened. In addition, since the first organic molecules are attached to the substrate by volatilization in this method, a self-polymerizable material such as a silane coupling agent that starts self-polymerization in the reaction system at the same time as the formation of the monomolecular film is usually used. Even in this case, the self-polymerized material having a large molecular weight and a high boiling point does not volatilize and does not adhere to the substrate, so that a uniform monomolecular film can be obtained on the substrate.

  In the case of the spin coating method / dip coating method, specifically, for example, a solution in which the same first organic molecule as described above is dissolved is applied to the lower layer surface by spin coating or dip coating. Thereafter, the base is heated to about 50 to 150 ° C. or exposed to the vapor of a dehydration condensation accelerator such as hydrochloric acid or ammonia, thereby chemically bonding the lower layer and the first organic molecule, and extra material. Is removed by washing with a solvent, whereby the first monomolecular film 42 is formed on the lower layer. This method has an advantage that it is economical because the material for forming the first monomolecular film 42 may be small. Further, since the heating is performed, the reaction proceeds rapidly, and the formation time can be shortened.

In the case of the Langmuir Blodgett method, for example, the first organic molecule similar to the above, which is amphiphilic, is developed on the water surface and aggregated to a surface pressure expected to be a monomolecular film, and then the surface of the crystallization promoting layer The first monomolecular film 42 can be formed by transferring the film.
In addition, after forming a monomolecular film by the Langmuir Blodget method, by applying heat, light or chemical stimulation, the end of the Langmuir Blodget film, the lower layer surface, the surface of the first monomolecular film 42, or the second The surface of the second monomolecular film 44 may be bonded. By doing so, the stability at the time of forming the organic semiconductor layer 5 by improving the bonding between the Langmuir blowet film and the layer in contact with the film surface, and the periodicity of the Langmuir blowet film are increased. It can be compatible.

  When there are a plurality of layers of the first monomolecular film 42, an organic molecule (first molecule) in which functional groups used for the first chemical bond are bonded to both ends of the organic molecular skeleton forming the first monomolecular film 42. The first monomolecular film 42 having one or more layers is formed in advance using an organic molecule), and then a functional group used for the first chemical bond is formed on one end of the organic molecular skeleton forming the first monomolecular film 42. Using the organic molecule (first organic molecule) to which the functional group used for the second chemical bond is bonded at the other end, the functional group used for the second chemical bond is exposed on the outermost surface. One monomolecular film 42 is formed.

After the formation of the first monomolecular film 42 as described above, an organic molecule (first molecule) in which a functional group used for the second chemical bond is bonded to one end of the organic molecular skeleton forming the second monomolecular film 44. As described above, the second monomolecular film 44 can be formed using the second organic molecule.
Further, the method for forming the organic semiconductor layer 5 on the formed second monomolecular film 44 is not particularly limited, and a general solution immersion method, a gas phase reaction method, a spin coating method, a dip coating method, and the like. In addition to the Langmuir Blodget method and the like, known methods such as a casting method, a pulling method, an ink jet printing method, a screen printing method, a gravure printing method, and a vacuum deposition method can be used.
In the organic transistor of the present invention, the method of disposing the gate electrode 2, the gate insulating layer 3, the source electrode 6, and the drain electrode 7 on the substrate is not particularly limited, and can be performed by a known method.

<Display device>
The display device of the present invention includes a circuit board in which the organic transistor of the present invention is electrically connected, and a liquid crystal, organic electroluminescence, or electricity electrically connected to the organic transistor on the circuit board. The display device includes an electrophoretic pixel and a driver that sends an electric signal to the transistor. Except for using the organic transistor of the present invention, it can be the same configuration as the conventional display device, circuit board, liquid crystal, organic electroluminescence, electrophoresis pixel, driver is not particularly limited, A well-known and usual thing can be used.

<< Method for Manufacturing Organic Transistor >>
The manufacturing method of the organic transistor of the present invention is a manufacturing method of manufacturing the organic transistor of the present invention.
If a bottom gate type and top contact type organic transistor as shown in FIG. 1A is manufactured, the organic transistor manufacturing method of the present invention includes a gate electrode and a gate insulating layer on a substrate. A first step of forming, a second step of forming a crystal promotion layer on the surface of the gate insulating layer, and a third step of forming an organic semiconductor layer, a source electrode and a drain electrode on the surface of the crystal promotion layer, The step of forming the crystal promotion layer in the second step includes the step of forming at least one first monomolecular film in contact with the surface of the gate insulating layer, and the step of forming the first monolayer. Forming a second monomolecular film in contact with the surface of the molecular film.

The substrate, gate electrode, gate insulating layer, crystal promotion layer, organic semiconductor layer, source electrode, and drain electrode in the above method are the same as described above.
The method for forming the gate electrode and the gate insulating layer on the substrate in the first step is not particularly limited. Specifically, for example, after forming the gate electrode by sputtering through a mask, the gate insulating layer is formed. A gate insulating layer can be formed by sputtering material from above.
The method for forming the crystal promotion layer in the second step is the same as described above.
The method for forming the organic semiconductor layer in the third step is the same as described above.
The method for forming the source electrode and the drain electrode in the third step is not particularly limited. Specifically, for example, the source / drain electrodes are formed on the organic semiconductor layer by vacuum deposition through a mask. Can be formed.

  Further, in the case of manufacturing a bottom gate type and bottom contact type organic transistor as shown in FIG. 1B, the organic transistor manufacturing method of the present invention includes a gate electrode and a gate insulation on a substrate. A first step of forming a layer, a second step of forming a source electrode and a drain electrode on the surface of the gate insulating layer, and at least the surface of the gate insulating layer, or the surface of the gate insulating layer, the source electrode And a third step of further forming an organic semiconductor layer after forming the crystal promotion layer on the drain electrode surface, and the step of forming the crystal promotion layer of the third step includes the step of forming the gate insulating layer. Forming at least one first monomolecular film in contact with the surface; and forming the second monomolecular film in contact with the surface of the first monomolecular film. Including the.

The substrate, gate electrode, gate insulating layer, crystal promotion layer, organic semiconductor layer, source electrode, and drain electrode in the above method are the same as described above.
The method for forming the gate electrode and the gate insulating layer on the substrate in the first step is not particularly limited. Specifically, for example, after forming the gate electrode by sputtering through a mask, the gate insulating layer is formed. A gate insulating layer can be formed by sputtering a material from above.
The method for forming the source electrode and the drain electrode in the second step is not particularly limited. Specifically, for example, the source / drain electrodes are formed on the organic semiconductor layer by vacuum deposition or lithography through a mask. Can be formed.
The method for forming the crystal promotion layer and the method for forming the organic semiconductor layer in the third step are the same as described above. In addition, by forming the crystal promotion layer not only on the gate insulating layer but also on the source / drain electrode, the crystal grain size on the surface of the source / drain electrode also increases, and the crystal acceleration layer extends from the source / drain electrode. It is preferable because carrier transport to the organic semiconductor layer, which is an upper layer, is efficiently performed and contact resistance is reduced.

  Furthermore, in the case of manufacturing a top gate type and top contact type organic transistor as shown in FIG. 1 (c), the organic transistor manufacturing method of the present invention forms a crystal promotion layer on a substrate. A first step, a second step of sequentially forming an organic semiconductor layer, a source electrode and a drain electrode on the surface of the crystal promotion layer; and a first step of forming a gate insulating layer and a gate electrode on at least the surface of the organic semiconductor layer. And the step of forming the crystal promotion layer of the first step includes the step of forming at least one first monomolecular film in contact with the surface of the substrate, and the first step Forming the second monomolecular film in contact with the surface of the monomolecular film.

The substrate, gate electrode, gate insulating layer, crystal promotion layer, organic semiconductor layer, source electrode, and drain electrode in the above method are the same as described above.
The method for forming the crystal promotion layer on the substrate in the first step is the same as described above.
The method for forming the organic semiconductor layer in the second step is the same as described above. In addition, the method for forming the source electrode and the drain electrode in the second step is not particularly limited. Specifically, for example, the source / drain electrode may be formed on the organic semiconductor layer by vacuum deposition or lithography via a mask. A drain electrode can be formed.
The method of forming the gate electrode and the gate insulating layer in the third step is not particularly limited. Specifically, for example, after forming the gate electrode by sputtering through a mask, the gate insulating layer material A gate insulating layer can be formed by sputtering from above.

  In the case of manufacturing a top gate type and bottom contact type organic transistor as shown in FIG. 1 (d), the organic transistor manufacturing method of the present invention forms a crystal promotion layer on a substrate. A first step, a second step of sequentially forming a source electrode and a drain electrode and an organic semiconductor layer on the surface of the crystal promotion layer, and a third step of forming a gate insulating layer and a gate electrode on the surface of the organic semiconductor layer. And the step of forming the crystal promotion layer of the first step is in contact with the surface of the substrate and forming at least one first monomolecular film, and the first step Forming a second monomolecular film in contact with the surface of the monomolecular film. Further, after forming a crystal promotion layer on the substrate, the first step of forming the source electrode and the drain electrode and at least the substrate surface, or the substrate surface, the source electrode and the drain electrode surface, Further, a step of forming the organic semiconductor layer and a third step of forming a gate insulating layer and a gate electrode on the surface of the organic semiconductor layer, and forming the crystal promotion layer of the second step Forming at least one layer of the first monomolecular film at least on the surface of the substrate or in contact with the surface of the substrate, the source electrode and the drain electrode, and the first monomolecule It can also be produced from the step of forming the second monomolecular film in contact with the surface of the film.

The substrate, gate electrode, gate insulating layer, crystal promotion layer, organic semiconductor layer, source electrode, and drain electrode in the above method are the same as described above.
The method for forming the source electrode and the drain electrode on the organic semiconductor layer or the substrate is the same as described above.
The method for forming the crystal promotion layer and the method for forming the organic semiconductor layer are the same as described above. In addition, by forming the crystal promotion layer not only on the substrate but also on the source / drain electrode, the crystal grain size on the surface of the source / drain electrode also increases, and from the source / drain electrode to the upper layer of the crystal promotion layer. It is preferable because carrier transport to the organic semiconductor layer is efficiently performed and contact resistance is reduced.
The method for forming the gate electrode and the gate insulating layer in the third step is the same as described above.

  Hereinafter, embodiments of the present invention will be described using specific examples, but the present invention is not limited to the following embodiments.

[First embodiment / Organic transistor]
The first embodiment is a bottom gate type and top contact type organic transistor.
Below, the specific example of the organic transistor of a 1st aspect is demonstrated using the schematic diagram of FIG.
The organic transistor of the first aspect shown in FIG. 5A includes a glass substrate 1 (20 mm × 20 mm), a gate electrode 2 made of aluminum, a gate insulating layer 3 made of silicon dioxide, a crystal promotion layer 4, The organic semiconductor layer 5 is made of fullerene, and the source electrode 6 and the drain electrode 7 are made of aluminum and stacked on the lithium fluoride layer. As shown in FIG. 5B, the crystal promotion layer 4 of the first aspect includes a first monomolecular film 42 laminated on the gate insulating layer 3 via a first chemical bond 41, and , And a second monomolecular film 44 stacked via the second chemical bond 43.
In the crystal promotion layer 4 of the first embodiment, the first chemical bond 41 is a siloxane bond, the organic molecular skeleton of the first monomolecular film 42 is undecane, and the second chemical bond 43 is an amine bond. The organic molecular skeleton of the second monomolecular film 44 is fullerene.

In the first aspect, since the organic molecular skeletons of the second monomolecular film 44 and the organic semiconductor layer 5 are the same fullerene, the surface energy of the crystal promotion layer 4 and the organic semiconductor layer 5 can be made equal. it can. When the surface energy is equal, the semiconductor material is well wetted, so that the fullerene crystals constituting the organic semiconductor layer grow in layers, and the crystal grains of the organic semiconductor layer 5 can be increased.
In the first embodiment, the skeleton of the first monomolecular film 42 is a linear alkane and the skeleton of the second monomolecular film 44 is a fullerene that is an aromatic molecule. The molecules in the film 44 can be freely arranged, and a periodic structure is formed in the second monomolecular film 44 by the cohesive force of the π-π interaction by the aromatic π electrons.

Further, FIG. 5C is a schematic cross-sectional view assuming a case where the crystal promotion layer is cut in a direction parallel to the substrate at the center of the second monomolecular film 44 at the vertical position of the fullerene, and FIG. ) Is a schematic diagram when fullerenes described in Non-Patent Document 6 are arranged in a single crystal state. As shown in FIG. 5C, the organic molecular skeleton group (fullerene) constituting the second monomolecular film 44 on the organic molecular skeleton group (straight chain alkane) constituting the first monomolecular film 42. ) Is arranged, the arrangement has the same distance between the centers of gravity as in the single crystal state of fullerene as shown in FIG. As a result, the fullerene of the organic semiconductor layer 5 applied on the fullerene of the second monomolecular film 44 is arranged according to the crystal lattice of the second monomolecular film 44, and an organic semiconductor layer having a large crystal grain is obtained.
The organic transistor of the first aspect can be manufactured as follows, for example.

1. Formation of gate electrode and gate insulating layer on substrate A glass substrate (for example, a substrate size of 20 mm × 20 mm) is prepared. A gate electrode is formed on the substrate by sputtering aluminum with a thickness of about 60 nm through a metal mask. Further, as a gate insulating layer, silicon dioxide is formed on the entire surface of the substrate by sputtering to a thickness of about 200 nm.

2. Formation of first monolayer A solution of 11-azidoundecyltrimethoxysilane (AzUDTMS) in 2 mM trichlorethylene is prepared. Spin coat on the substrate. Then, after exposing to hydrochloric acid vapor, the substrate is ultrasonically cleaned to form a monomolecular film of the molecule. When the film thickness of the obtained monomolecular film is obtained from X-ray reflectivity measurement (GIXR) and shows a value close to the molecular length (1.7 nm) of AzUDTMS, it is confirmed that the monomolecular film is obtained. it can.

3. Formation of second monomolecular film A 1 mM toluene solution of fullerene (C60) was prepared, and 2. Are immersed and stirred at 100 ° C. for 3 days in a nitrogen atmosphere. After completion of the reaction, the substrate is ultrasonically cleaned in toluene to remove the excessively attached fullerene. By the above processing, a second monomolecular film made of C60 is formed. When the film thickness is obtained from GIXR and shows an increase in a value close to the molecular size of C60 (1.10 nm), it can be confirmed that a monomolecular fullerene film is obtained. In addition, when the intermolecular distance in the in-plane direction is obtained from the X-ray diffraction method (XRD in-plane), and shows a value that matches or approximates the intermolecular distance (1.1 nm and 1.4 nm) of C60 single crystal. It can be confirmed that a periodic structure suitable for crystallization promotion of fullerene which is an organic semiconductor layer is obtained.

4). Formation of Organic Semiconductor Layer A dichlorobenzene solution (1 wt%) of C60 is prepared as an organic semiconductor layer, 0.1 ml drop-cast on 3 substrates, left overnight at room temperature, and waits for the solvent to evaporate. About the size of the crystal grain of the obtained organic-semiconductor layer, it can evaluate from an optical microscope or a scanning electron microscope (SEM).
5. Formation of Source / Drain Electrode On the organic semiconductor layer, lithium fluoride (1 nm) and aluminum (60 nm) are sequentially vacuum-deposited through a metal mask to form a source / drain electrode. The channel length and channel width are preferably 50 m and 100 μm.

  The organic transistor (n-type) according to the first aspect obtained as described above includes the crystal promotion layer 4 to increase the crystal grain size of the organic semiconductor layer 5, and as a result, excellent transistor characteristics (for example, , Mobility). The mobility can be measured by a known method.

Moreover, it can be judged from the following method that the first monomolecular film 42 or the second monomolecular film 44 is formed in the crystal promotion layer 4 obtained as described above.
1. Film thickness measurement The film thickness of an organic film is measured by measuring X-ray reflectivity. If the film thickness is about the same as the molecular length in the major axis direction of the molecule for forming the first monomolecular film and the second monomolecular film, the major axis of the molecule is oriented in the direction perpendicular to the substrate. You can see that In addition to measuring the film thickness by the X-ray reflectivity measurement method, the film thickness can also be evaluated from a spectroscopic ellipsometer.

2. FT-IR measurement The light is incident on the substrate on which the film is formed from an oblique direction (for example, 5 ° with respect to the substrate surface), and the reflection absorption spectrum is measured. Can be evaluated. This method can be applied to many monomolecular films, but when a monomolecular film is formed using molecules having a long-chain aliphatic hydrocarbon group, molecular identification and orientation evaluation are performed simultaneously. Since it can be performed, it is preferable. Specific examples of the monomolecular film having a long-chain aliphatic hydrocarbon group include the first monomolecular film AzUDTMS of the first aspect and the third aspect described later, and the first of the second aspect described later. Monomolecular film AzUDP and AmUDC of the 4th aspect mentioned later are mentioned. Peaks observed, AzUDTMS in and ^AzUDP, 2919cm ^-1, a peak attributed to CH ₂ stretching of aliphatic hydrocarbon chains in 2850 cm ^-1 (alkylene chain), observed peaks due to azide group to 2096cm ^-1 Is done. Further, the ^AmUDC, 2919cm ^-1, a peak attributed to CH ₂ stretching of aliphatic hydrocarbon chains in 2850 cm ^-1, a peak attributable to the amino group near 3400 cm ^-1 is observed.
Further, the orientation can be evaluated from the peak position resulting from CH ₂ stretching of the aliphatic hydrocarbon chain. Specifically, aliphatic hydrocarbon chains when densely packed ^orientation, 2919Cm -1, peak 2850 cm ^-1 is observed. On the other hand, in a state like that in a solution in which aliphatic hydrocarbon chains are randomly oriented, peaks are observed at 2924 cm ⁻¹ and 2854 cm ^−1, and the peak shifts to the higher wavenumber side as the orientation is disturbed. (For example, Non-Patent Document 9: Journal of The American Chemistry 130 (2008) 10556 Lee et al.). That is, the orientation state of molecules in the monomolecular film can be evaluated from the peak position of the obtained spectrum.
The above evaluation method is called a reflection absorption method, and is suitable when the substrate surface is provided with a layer that reflects infrared light such as metal. On the other hand, the transmission absorption method is suitable when using a substrate that transmits a part of infrared light, such as glass or a lightly doped silicon substrate. In addition, the absorption spectrum may be evaluated by an attenuated total reflection (ATR) method by pressing a substrate on which a film is formed on a prism such as Ge or ZnSe.

3. UV-vis spectrum With respect to the substrate on which the film is formed, light is incident in a vertical direction or an oblique direction (for example, 45 °), a transmission absorption spectrum is measured, and molecular identification, orientation and crystal state on the substrate surface are measured. Can be evaluated. This method includes the second monomolecular film C60 of the first embodiment and the third embodiment described later, the second monomolecular film EtPen of the second embodiment described later, and the second monolayer of the fourth embodiment described later. It is suitable for a molecule that exhibits strong absorption in the wavelength region of ultraviolet-visible light, such as the monomolecular film T3-Ald. Compared to the above FT-IR, the measurement can be performed in an air atmosphere without considering the absorption of air, so that the measurement is simple. The formation of the monomolecular film is measured in a solution of the formed molecule and compared with an absorption spectrum, whereby the material can be identified.
In addition, when polarized light is incident on the substrate from an oblique direction, the orientation state and packing (crystal state) of molecules in the film can be evaluated. More specifically, the absorption of molecules occurs depending on the direction of the transition dipole moment that the molecules have. When molecules are arranged on the substrate, the transition dipole moment is also arranged, so that anisotropy occurs in absorption. In other words, by entering appropriate polarized light from an appropriate direction, a specific transition dipole moment can be absorbed, and thus the orientation can be evaluated. On the other hand, the crystal state evaluation method will be described. It is known that when a plurality of transition dipole moments approach and meet, a dipole-dipole interaction occurs and the absorption wavelength peak shifts (for example, Non-Patent Document 10: Thin Solid Films 160 (1988) 87 Nakaoka. Et.) The amount of shift depends on the distance between molecules, and the shift direction is determined by the relative positional relationship of the molecules. That is, by comparing the random wavelength and the absorption wavelength position of the monomolecular film, the positional relationship of the molecules in the film can be understood, so the lattice constant can be estimated.
As a specific example, an example in which the orientation and crystal state of T3-Ald of the fourth aspect described later is evaluated from the UV-vis spectrum will be shown. T3-Ald has a transition dipole moment that absorbs at about 400 nm in the long axis direction of the molecule. Therefore, when T3-Ald is vertically oriented with respect to the substrate as shown in a process diagram 3) of the fourth mode described later, incident light from the vertical direction is not excited and is very weakly absorbed. Indicates. On the other hand, when p-polarized light is incident on the substrate at an angle of 45 °, absorption is observed because the transition dipole moment arranged in the direction perpendicular to the substrate is excited. Further, the absorption peak position is observed in the vicinity of 330 nm shifted to a wavelength shorter than 400 nm due to the interaction between molecules. From such an evaluation result, the molecules are arranged in a direction perpendicular to the substrate, and the intermolecular distance, that is, the distance between the centers of gravity of T3-Ald is shorter than the random state in the solution (the intermolecular distance is 2 nm Hereinafter, it can be determined that it is close to the single crystal state of T3-Ald.
Next, a method for confirming the formation of the first chemical bond and the second chemical bond will be described. The formation of the chemical bond can be judged by evaluating XPS, FT-IR, and solid-state NMR and identifying the structure of the formed chemical bond. Specifically, the evaluation result of the substrate before the chemical bond is formed is compared with the evaluation result of the substrate after the chemical bond is formed, and it is confirmed that the structure of the bond is formed after the chemical bond is formed. .
As a specific example, a method for confirming the formation of the second chemical bond (amine bond) of the first aspect and the third aspect described later is shown. First, when XPS measurement of the first monomolecular film is performed before the second chemical bond is formed, N 1s derived from the terminal azide group at an intensity ratio of 1: 2 in 400 eV and 404 eV. The peak is observed. Next, when measured after the formation of the second chemical bond, the peak intensity of 404 eV decreases, and the peak position of the amine bond N 1s appears at 400 eV, so the intensity of 400 eV increases. From such a change in peak intensity, the formation of an amine bond can be confirmed. Similarly, it can be determined from FT-IR. Although it is observed at 2096 cm ⁻¹ derived from an azide group on the substrate before amine bond formation, a peak at 1250 cm ⁻¹ derived from amine bond appears after amine bond formation. The formation of the second chemical bond can also be confirmed from the appearance of the peak of the amine bond and the comparison of the peak intensity. In addition, since the distance between the centers of gravity of the organic molecular skeletons constituting the first monomolecular film and the second monomolecular film shown in this example is different, the first monomolecular film shown in FIGS. 5B and 5C is used. The organic molecular skeleton constituting the second monomolecular film is not bonded 1: 1 with respect to the organic molecular skeleton constituting the monomolecular film. Therefore, when the above measurement is performed after forming the second monomolecular film, the peak derived from the unreacted functional group (azide group) on the first monomolecular film and the second chemical bond (amine bond) Both are detected. From the detection of both peaks, the crystal promotion layer of the present invention is composed of a plurality of monomolecular films composed of the first monomolecular film and the second monomolecular film, and the first monomolecular film and the second monomolecular film It can be confirmed that the distance between the centers of gravity of the organic molecular skeletons constituting the film is different.
In addition, in order to confirm that the crystal promotion layer of the present invention is formed on the substrate after the layer constituting the organic transistor other than the crystal promotion layer (for example, organic semiconductor layer) is formed, It is preferable to analyze the crystal promotion layer after removing and peeling off the layer formed on the crystal promotion layer by exposing to a cleaning or vacuum heating condition.

[Second embodiment / Organic transistor]
The second aspect is a bottom gate type and bottom contact type organic transistor. By using the bottom contact type, photolithography which is an existing technique can be used for forming the source electrode 6 and the drain electrode 7, so that the distance (channel length) between the source electrode 6 and the drain electrode 7 is shortened. Can do.
Below, the specific example of the organic transistor of a 2nd aspect is demonstrated using the schematic diagram of FIG.
The organic transistor of the second embodiment shown in FIG. 6A includes a glass substrate 1 (20 mm × 20 mm), a gate electrode 2 made of aluminum, a gate insulating layer 3 made of aluminum oxide, a crystal promotion layer 4, The organic semiconductor layer 5 is made of 6,13-bis (triisopropylsilylethynyl) pentacene (Tips-pentacene), and the source electrode 6 and the drain electrode 7 are made of gold. As shown in FIG. 6B, the crystal promotion layer 4 of the second embodiment includes a first monomolecular film 42 laminated on the gate insulating layer 3 via the first chemical bond 41, and , And a second monomolecular film 44 stacked via the second chemical bond 43.
In the crystal promotion layer 4 of the second embodiment, the first chemical bond 41 is a phosphate ester bond, the organic molecular skeleton of the first monomolecular film 42 is undecane (C11), and the second chemical bond 43 Is a triazole ring, and the organic molecular skeleton of the second monomolecular film 44 is pentacene.
Further, in this embodiment, crystal promotion layers 46 and 47 are also formed on the surfaces of the source / drain electrodes 6 and 7. The crystal promotion layers 46 and 47 have the same configuration as the crystal promotion layer 4 except that the first chemical bond is a gold-thiol bond.

In the second embodiment, since the main chain skeletons of the organic molecular skeletons of the second monomolecular film 44 and the organic semiconductor layer 5 are the same pentacene, the surface energy of the crystallization promoting layer 4 and the organic semiconductor layer 5 is reduced. Can be equal. Since the surface energy is equal, the semiconductor material is well wetted, so that the crystal of the semiconductor material grows in layers and the crystal grain of the organic semiconductor layer 5 can be increased.
In the second embodiment, the skeleton of the first monomolecular film 42 is a linear alkane, and the skeleton of the second monomolecular film 44 is pentacene, which is an aromatic molecule. The molecules in the film 44 can be freely arranged, and a periodic structure is formed in the second monomolecular film 44 by the cohesive force of the π-π interaction by the aromatic π electrons.

Further, FIG. 6C is a schematic view when Tips-pentacene is arranged in a single crystal state. As shown in FIG. 6B, the organic molecular skeleton group (pentacene) constituting the second monomolecular film 44 on the organic molecular skeleton group (linear alkane) constituting the first monomolecular film 42. As shown in FIG. 6C, an arrangement having a distance between the centers of gravity similar to the single crystal state of Tips-pentacene, which is an organic semiconductor layer, can be obtained. As a result, the Tips-pentacene of the organic semiconductor layer 5 coated on the pentacene of the second monomolecular film 44 is arranged according to the crystal lattice of the second monomolecular film 44, and an organic semiconductor layer having a large crystal grain is obtained. It is done.
Further, since the crystal promotion layer 4 is formed also on the source / drain electrodes 6, 7, the crystal grain size on the surface of the source / drain electrodes 6, 7 is increased. Is efficiently transported to the organic semiconductor layer 5, and the effect of reducing the contact resistance is also produced.
The organic transistor of the second aspect can be manufactured, for example, as follows.

1. Formation of Gate Electrode and Gate Insulating Layer on Substrate Up to the gate insulating layer is formed on the substrate by the same material and method as in Example 1.

2. Formation of Source / Drain Electrodes After forming a photoresist pattern using existing photolithography, chromium and gold are vacuum-deposited by 5 nm and 60 nm respectively, and lift-off is performed. Thus, source / drain electrodes having a channel length of 5 μm and a channel width of 1000 μm are formed. A drain electrode is formed.

3. Formation of first monomolecular film A 1 mM anhydrous toluene solution of 11-azidoundecylphosphonic acid (AzUDP) was prepared, and 2. The substrate is immersed and left under a nitrogen atmosphere for 24 hours. Thereafter, the substrate is ultrasonically cleaned in toluene to form a monomolecular film of the molecule on the surface of the gate insulating layer.
Furthermore, a 1 mM anhydrous acetonitrile solution of 11-azidoundecylthiol (AzUDT) is prepared, and the substrate is immersed in the solution and left under a nitrogen atmosphere for 24 hours. The phosphonic acid group of AzUDP selectively forms a phosphonic acid bond with aluminum oxide on the gate insulating layer, and the thiol group of AzUDT selectively forms a gold and gold-thiol bond on the source and drain electrodes.

4). Formation of Second Monomolecular Film A 1 mM dimethylformamide (DMF) solution of 6,13-bisethynylpentacene (EtPen) is prepared. In a nitrogen atmosphere, 1 mol% of ascorbic acid and copper sulfate were added as a catalyst with respect to EtPen, followed by stirring at 70 ° C. for 24 hours. After completion of the reaction, the substrate was ultrasonically washed in DMF to remove excessively attached EtPen. By the above treatment, a second monomolecular film having a pentacene skeleton is formed. EtPen is obtained by dissolving Tips-pentacene in a 5 mM DMF solution of potassium hydroxide and reacting at room temperature for 12 hours.
When the intermolecular distance in the in-plane direction is obtained from the X-ray diffraction method (XRD in-plane), and shows a value that matches or approximates the intermolecular distance (0.78 nm and 0.77 nm) of the single crystal of Tips pentacene. It can be confirmed that a periodic structure suitable for crystal growth of Tips-pentacene, which is an organic semiconductor layer, is obtained.

5. Formation of Organic Semiconductor Layer A toluene solution of Tips-pentacene (1 wt%) is prepared as an organic semiconductor layer, 0.1 ml drop-cast on 3 substrates, left at room temperature for 3 hours, and waits for the solvent to evaporate. The crystal grain size of the formed organic semiconductor layer can be evaluated from an optical microscope or a scanning electron microscope.

  The organic transistor (p-type) of the second aspect obtained as described above includes the crystal promotion layer 4 so that the organic semiconductor layer 5 is formed on the gate insulating layer (channel region) and on the source and drain electrode surfaces. The crystal grain size is increased, and as a result, good transistor characteristics (eg, mobility) can be exhibited. The mobility can be measured by a known method. Further, as compared with the conventional case (for example, in the case where the anchor layer of Patent Document 1 is provided), a transistor having favorable characteristics can be obtained by simply providing a crystal promotion layer without complicated synthesis.

[Third Aspect / Organic Transistor]
The third embodiment is a top gate type and top contact type organic transistor.
Below, the specific example of the organic transistor of a 3rd aspect is demonstrated using the schematic diagram of FIG.
The organic transistor of the third embodiment shown in FIG. 7 (a) includes a glass substrate 1 (20 mm × 20 mm), a gate electrode 2 made of aluminum, a gate insulating layer 3 made of polyvinylphenol, a crystal promotion layer 4, The organic semiconductor layer 5 is made of fullerene (C60), and the source electrode 6 and the drain electrode 7 are made of aluminum laminated on the lithium fluoride layer. As shown in FIG. 7B, the crystal promotion layer 4 of the third aspect includes a first monomolecular film 42 laminated on the substrate 1 via a first chemical bond 41, And a second monomolecular film 44 laminated through two chemical bonds 43.
In the crystal promotion layer 4 of the third embodiment, the first chemical bond 41 is a siloxane bond, the organic molecular skeleton of the first monomolecular film 42 is undecane, and the second chemical bond 43 is an amine bond. The organic molecular skeleton of the second monomolecular film 44 is fullerene.

In the third aspect, since the organic molecular skeletons of the second monomolecular film 44 and the organic semiconductor layer 5 are the same fullerene, the surface energy of the crystal promotion layer 4 and the organic semiconductor layer 5 can be made equal. it can. Since the surface energy is equal, the semiconductor material is well wetted, so that the crystal of the semiconductor material grows in layers and the crystal grain of the organic semiconductor layer 5 can be increased.
In the third embodiment, the skeleton of the first monomolecular film 42 is a linear alkane, and the skeleton of the second monomolecular film 44 is a fullerene that is an aromatic molecule. The molecules in the film 44 can be freely arranged, and a periodic structure is formed in the second monomolecular film 44 by the cohesive force of the π-π interaction by the aromatic π electrons.
The organic transistor of the third aspect can be manufactured as follows, for example.

1. Formation of a gate electrode and a gate insulating layer on a substrate A glass substrate having a substrate size of 20 mm × 20 mm is prepared.
2. Formation of the first monomolecular film and the second monomolecular film After the glass substrate is cleaned by ultrasonic cleaning, the first monomolecule composed of AzUSTMS is used on the substrate under the same conditions as in the first embodiment 2. A film is formed. Further, a second monomolecular film made of C60 is formed using the same conditions as in 3 of the first aspect. When the intermolecular distance in the in-plane direction is determined from the X-ray diffraction method (XRD in-plane) and shows a value that matches or approximates the intermolecular distance (1.1 nm and 1.4 nm) of the C60 single crystal, It can be confirmed that a periodic structure suitable for fullerene crystal growth of the organic semiconductor layer is obtained.
3. Formation of Organic Semiconductor Layer Fullerene (60 nm) is formed as an organic semiconductor layer by vacuum evaporation (deposition rate 0.05 nm / s). The crystal grain size of fullerene of the formed organic semiconductor layer can be evaluated from an optical microscope or a scanning electron microscope.
4). Formation of Source / Drain Electrode A source / drain electrode made of lithium fluoride (1 nm) and aluminum (60 nm) is formed using the same conditions as in 5 of the first embodiment.
5. Formation of Gate Insulating Layer and Gate Electrode A gate insulating layer made of polyvinylphenol (300 nm) is formed on the organic semiconductor layer and the source / drain electrodes. As a forming method, a chloroform solution of polyvinylphenol is prepared, and the solution is formed on a substrate by spin coating (for example, 500 rpm for 10 seconds and then 3000 rpm for 1 minute). Finally, aluminum (60 nm) is formed as a gate electrode on the gate insulating layer by sputtering.

  The organic transistor (n-type) of the third aspect obtained as described above is a top gate type organic transistor, but the crystal grain size of the organic semiconductor layer 5 is increased by providing the crystal promotion layer 4. As a result, good transistor characteristics (for example, mobility) can be exhibited. The mobility can be measured by a known method.

[Fourth Aspect / Organic Transistor]
The fourth embodiment is a bottom gate type and top contact type organic transistor.
Below, the specific example of the organic transistor of a 4th aspect is demonstrated using the schematic diagram of FIG.
The organic transistor of the fourth embodiment shown in FIG. 8A includes a glass substrate 1 (20 mm × 20 mm), a gate electrode 2 made of aluminum, a gate insulating layer 3 made of polyimide, a crystal promotion layer 4, a pentacene. An organic semiconductor layer 5 made of gold, and a source electrode 6 and a drain electrode 7 made of gold. As shown in FIG. 8B, the crystal promotion layer 4 of the fourth aspect includes a first monomolecular film 42 that is a Langmuir Blodget film and a first monomolecular film 42 on the gate insulating layer 3. And a second monomolecular film 44 laminated on the second chemical bond 43.
In the crystal promotion layer 4 of the fourth aspect, the organic molecular skeleton of the first monomolecular film 42 is undecane (C11), the second chemical bond 43 is an imine bond, and the second monomolecular film 44 The organic molecular skeleton is terthiophene.

In the fourth aspect, since the first monomolecular film is a Langmuir Blodgett film, the first monomolecular film 42 having a periodic structure is formed regardless of the material and the binding site of the crystal-promoting layer forming surface. can do. In addition, since the distance between the centers of gravity of the organic molecular skeleton constituting the first monomolecular film 42 can be appropriately adjusted by adjusting the surface pressure during the production of the Langmuir Blodgett film, the first monomolecular film 42 is desired. The periodic structure having a distance between the centers of gravity of the second monomolecular film 44 can be appropriately determined, and the crystal grains of the organic semiconductor layer 5 can be increased. Even when a Langmuir Blodgett film is applied to the second monomolecular film 44, the same effect can be obtained more directly.
In the fourth aspect, since the organic molecular skeletons of the second monomolecular film 44 and the organic semiconductor layer 5 are the same fullerene, the surface energy of the crystal promotion layer 4 and the organic semiconductor layer 5 can be made equal. it can. Since the surface energy is equal, the semiconductor material is well wetted, so that the crystal of the semiconductor material grows in layers and the crystal grain of the organic semiconductor layer 5 can be increased.
In the fourth embodiment, the skeleton of the first monomolecular film 42 is a linear alkane and the skeleton of the second monomolecular film 44 is a terthiophene that is an aromatic molecule. The molecules in the molecular film 44 can be freely arranged, and a periodic structure is formed in the second monomolecular film 44 by the cohesive force of the π-π interaction by the aromatic π electrons.
Further, FIG. 8C is a schematic diagram when pentacene is arranged in a single crystal state. As shown in FIG. 8B, the organic molecular skeleton group (terthiophene) constituting the second monomolecular film 44 on the organic molecular skeleton group (straight chain alkane) constituting the first monomolecular film 42. ) Is arranged, an arrangement having a distance between the centers of gravity similar to the single crystal state of pentacene, which is an organic semiconductor layer, as shown in FIG. 8C can be obtained. As a result, the pentacene of the organic semiconductor layer 5 coated on the pentacene of the second monomolecular film 44 is arranged according to the crystal lattice of the second monomolecular film 44, and an organic semiconductor layer having a large crystal grain is obtained. In addition, the organic molecular skeleton group constituting the second monomolecular film and the skeleton group of the organic semiconductor layer are different, but both have π electrons, so the surface energy is similar and the crystal grain size is reduced. Produces an effect of enlarging.
The organic transistor of the fourth aspect can be manufactured, for example, as follows.

1. Formation of Gate Electrode and Gate Insulating Layer on Substrate After a gate electrode is formed on the substrate by the same method as in the first embodiment, polyimide is formed as a gate insulating layer by spin coating.
2. Formation of first monomolecular film A 1 mM hexane solution of 11-aminoundecylcarboxylic acid (AmUDC) is prepared and developed in the trough of the LB film production apparatus. The molecules on the water surface are compressed to a surface pressure (20 mN / m) expected to be a monomolecular film, and then transferred to a substrate to obtain an LB film made of 11-aminoundecylcarboxylic acid. When the thickness of the obtained monomolecular film is obtained from X-ray reflectivity measurement (GIXR) and shows a value that matches or approximates the molecular length of AmUDC (1.7 nm), there is no bonding group in the gate insulating layer. It can be confirmed that a monomolecular film can also be formed on polyimide.
3. Formation of Second Monomolecular Film A 1 mM tetrahydrofuran (THF) solution of terthiophene aldehyde (T3-Ald) is prepared, the solution is dip-coated on a substrate, and heated at 120 ° C. for 5 hours in a nitrogen atmosphere. After completion of the reaction, the substrate is ultrasonically cleaned in THF to remove excessively attached T3-Ald. By the above treatment, a second monomolecular film connected to the first monomolecular film by an imine bond can be formed.
In addition, when the intermolecular distance in the in-plane direction is obtained from an X-ray diffraction method (XRD in-plane) and shows a value that matches or approximates the intermolecular distance (0.63 nm and 0.77 nm) of a pentacene single crystal. It can be confirmed that a periodic structure suitable for crystal growth of pentacene in the organic semiconductor layer is obtained.
4). Formation of Organic Semiconductor Layer Pentacene (60 nm) is formed as an organic semiconductor layer on the three substrates by vacuum deposition.
5. Formation of Source / Drain Electrode Gold (60 nm) is vacuum-deposited on the organic semiconductor layer through a metal mask to form a source / drain electrode. The channel length and channel width are preferably 50 m and 100 μm.

  The organic transistor (p-type) according to the fourth aspect obtained as described above includes the crystal promotion layer 4 to increase the crystal grain size of the organic semiconductor layer 5, and as a result, excellent transistor characteristics (for example, , Mobility). The mobility can be measured by a known method.

[Fifth Aspect / Liquid Crystal Display Device]
The fifth aspect is a liquid crystal display device using the organic transistor of the first aspect.
Below, the specific example of the liquid crystal display device of a 5th aspect is demonstrated using the schematic diagram of FIG.
The liquid crystal display device of the fifth aspect shown in FIG. 9B includes the organic transistor and a pixel electrode made of ITO on the substrate of the organic transistor of the first aspect, and a drain electrode of the organic transistor, The pixel electrode is electrically connected. A counter substrate having a counter electrode made of ITO is provided via a spacer (not shown) so as to face the circuit substrate on which the organic transistor and the pixel electrode are provided, and between the circuit substrate and the counter substrate. Is a liquid crystal layer.
As shown in FIG. 9A, the gate electrode and the source electrode of the organic transistor are electrically connected to the gate bus line and the source bus line, respectively, and each bus line supplies a video signal driver for supplying a display signal. It is connected to the.
The liquid crystal display device of the fifth aspect obtained as described above is driven satisfactorily as a liquid crystal display device because the organic transistor of the present invention sufficiently satisfies the performance as a pixel driving transistor.

[Example 1]
In the same manner as in the first aspect, a gate electrode and a gate insulating layer were formed on a substrate, and an organic semiconductor layer made of a crystal promotion layer and fullerene was further formed. When the substrate on which the organic semiconductor layer was formed was observed with the naked eye, as shown in FIG. 10A, a fullerene thin film was formed over the entire substrate. Further, when the central portion of the substrate on which the organic semiconductor layer was formed was observed with an optical microscope, almost the entire surface was covered with a thin film made of fullerene crystals, as shown in FIG.

[Comparative Example 1]
After forming a gate electrode and a gate insulating layer on the substrate in the same manner as in the first aspect, an organic semiconductor layer made of fullerene was formed in the same manner as in the first aspect without forming a crystal promotion layer. . When the substrate on which the organic semiconductor layer was formed was observed with the naked eye, as shown in FIG. 11 (a), fullerene crystals were in balance at the edge of the substrate, and no fullerene thin film was formed at the center of the substrate. Further, when the central portion of the substrate on which the organic semiconductor layer was formed was observed with an optical microscope, as shown in FIG. 11B, small crystals having a short side of about 5 μm and a long side of about 10 μm were scattered, A thin film was not formed.

  From the above results, it was confirmed that the crystal grain size can be increased by providing a crystal promotion layer having the same periodic structure as that of the fullerene single crystal.

  The organic transistor of the present invention can be suitably used in the field of organic device production.

DESCRIPTION OF SYMBOLS 1 ... Substrate 2 ... Gate electrode 3 ... Gate insulating layer 4 ... Crystal promotion layer 5 ... Organic semiconductor layer 6 ... Source electrode 7 ... Drain electrode 41 ... First chemical bond 42 ... First monomolecular film 43 ... Second chemical bond 44 ... Second monomolecular film 46 ... Crystal accelerating layer 47 ... Crystal accelerating layer

Claims (17)

An organic transistor comprising a substrate, a gate electrode, a gate insulating layer, an organic semiconductor layer, a source electrode, a drain electrode, and a crystal promotion layer in contact with the organic semiconductor layer,
The crystal promotion layer is composed of at least a second monomolecular film in contact with the organic semiconductor layer and a first monomolecular film in contact with the second monomolecular film,
There is a region where the organic molecular skeleton group constituting the second monomolecular film is arranged at a distance between the centers of gravity equal to at least one direction in the plane,
An organic transistor, wherein organic molecule skeleton groups in contact with at least the region constituting the organic semiconductor layer are arranged at a distance between centers of gravity equal to at least one direction in a plane.   The distance between centroids of the organic molecular skeleton group constituting the first monomolecular film is different from the distance between centroids of the organic molecular skeleton group constituting the second monomolecular film. The organic transistor as described.   The first monomolecular film includes an organic molecular skeleton connected via a first chemical bond with atoms on a surface on which the first monomolecular film is formed, and the second monomolecular film includes: 3. The organic transistor according to claim 1, further comprising an organic molecular skeleton that is connected to the organic molecular skeleton constituting the first monomolecular film via a second chemical bond.   4. The organic transistor according to claim 1, wherein at least one layer of the first monomolecular film and the second monomolecular film is a Langmuir Blodgett film. 5.   The organic transistor according to any one of claims 1 to 4, wherein the organic molecular skeleton constituting the second monomolecular film is the same as the organic molecular skeleton constituting the organic semiconductor layer.   6. The organic molecular skeleton constituting the first monomolecular film is aliphatic, and the organic molecular skeleton constituting the second monomolecular film is aromatic. The organic transistor according to one item. The organic molecular skeleton constituting the first monomolecular film is a linear alkane,
7. The organic transistor according to claim 6, wherein the organic molecular skeleton constituting the second monomolecular film is fullerene, pentacene or oligothiophene.   The organic transistor according to claim 1 is electrically connected to a circuit board, and the liquid crystal, organic electroluminescence, or electrically connected to the organic transistor on the circuit board, or A display device comprising: an electrophoretic pixel; and a driver that sends an electric signal to the transistor. A manufacturing method for manufacturing the organic transistor according to any one of claims 1 to 7,
A first step of forming the gate electrode and the gate insulating layer on the substrate;
A second step of forming the crystal promotion layer on the surface of the gate insulating layer;
A third step of forming the organic semiconductor layer, the source electrode and the drain electrode on the surface of the crystal promotion layer,
The step of forming the crystal promotion layer in the second step includes the step of forming at least one first monomolecular film in contact with the surface of the gate insulating layer, and the step of forming the first monomolecular film. And a step of forming the second monomolecular film in contact with the surface. A manufacturing method for manufacturing the organic transistor according to any one of claims 1 to 7,
A first step of forming the gate electrode and the gate insulating layer on the substrate;
A second step of forming the source electrode and the drain electrode on the surface of the gate insulating layer;
After forming the crystal promotion layer at least on the surface of the gate insulating layer, or on the surface of the gate insulating layer, the source electrode, and the drain electrode, the method further includes a third step of forming the organic semiconductor layer. ,
The step of forming the crystal promotion layer in the third step includes at least the surface of the gate insulating layer, or the first monomolecular film in contact with the surface of the gate insulating layer, the source electrode, and the drain electrode. A method for producing an organic transistor, comprising: forming at least one layer, and forming the second monomolecular film in contact with the surface of the first monomolecular film. The step of forming the first monomolecular film includes the step of connecting the atoms on the surface of the gate insulating layer and the organic molecular skeleton constituting the first monomolecular film through a first chemical bond. ,
The step of forming the second monomolecular film comprises a second chemical bond between an organic molecular skeleton constituting the first monomolecular film and an organic molecular skeleton constituting the second monomolecular film. The method for producing an organic transistor according to claim 9, further comprising a step of connecting through the organic transistor. A manufacturing method for manufacturing the organic transistor according to any one of claims 1 to 7,
A first step of forming the crystal promotion layer on the substrate;
A second step of forming the organic semiconductor layer, the source electrode and the drain electrode in any order on the surface of the crystal promotion layer;
A third step of forming the gate insulating layer and the gate electrode at least on the surface of the organic semiconductor layer,
The step of forming the crystal promotion layer of the first step includes the step of forming at least one layer of the first monomolecular film in contact with the surface of the substrate, and the surface of the first monomolecular film. And a step of forming the second monomolecular film in contact with the organic transistor. The step of forming the first monomolecular film includes a step of connecting atoms on the substrate surface and an organic molecular skeleton constituting the first monomolecular film via a first chemical bond,
The step of forming the second monomolecular film comprises a second chemical bond between an organic molecular skeleton constituting the first monomolecular film and an organic molecular skeleton constituting the second monomolecular film. The method for producing an organic transistor according to claim 12, further comprising a step of connecting through the organic transistor. The step of forming the first monomolecular film forms a monomolecular film composed of organic molecules having a linear alkane as an organic molecular skeleton through a siloxane bond or a phosphate ester bond as the first chemical bond. Process
The step of forming the second monomolecular film is a step of forming fullerene, pentacene or oligothiophene through the amine bond, imine bond or triazole ring as the second chemical bond. The method for producing an organic transistor according to claim 11 or 13.   Any of the step of forming the first monomolecular film and the step of forming the second monomolecular film includes a step of forming a monomolecular film by the Langmuir Blodget method. The method for producing an organic transistor according to any one of claims 9 to 14, wherein:   The formation of the organic semiconductor layer includes a step of dissolving an organic semiconductor material in a solvent to form a solution, and a step of applying the solution to the surface of the crystal promotion layer. A method for producing an organic transistor according to one item.   Any one of the step of forming the first chemical bond and the step of forming the second chemical bond is performed by any one of a solution immersion method, a gas phase reaction method, and a spin coating method. The method for producing an organic transistor according to claim 9, wherein the organic transistor is used.