JP2018049931A - Organic transistor, operation control method of the same, and operation control method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an organic transistor capable of achieving a various operation by a single unit and an operation control method.SOLUTION: An operation control method of an organic transistor of the present invention is an operation control method of an organic transistor 10 that comprises an optical isomerizaiton molecular film 14 having an opening annular structure as a channel formation semiconductor film. The operation control method includes: a first step of irradiating ultraviolet light to a region as a channel by using a light source 21 of the irradiation light including visible light and the ultraviolet light and an optical system 22 that guides the visible light or the ultraviolet light of the irradiation light to the region as a channel of the optical isomerizaiton molecular film 14 in a state where a drain voltage and a gate voltage are applied to the organic transistor 10; and a second step of irradiating the visible light to at least one part of the region as a channel.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an organic transistor including a photoisomerized molecular film as a semiconductor film for forming a channel, an operation control method thereof, and an operation control apparatus.

  In recent years, the field of organic electronics has attracted attention, and an organic field effect transistor (OFET) using an organic semiconductor film is known as one of representative devices in this field. The organic semiconductor film can be formed on a plastic substrate with low heat resistance because it can be formed at a low temperature. By using this technology, a lightweight and flexible organic field effect transistor can be obtained. Can do. In addition, since an organic semiconductor film can be formed by a coating method or a printing method, a field effect transistor can be obtained easily and at a lower cost than using an inorganic semiconductor film. Can do.

  Non-Patent Document 1 discloses an operation of an organic transistor using a molecule (photoisomerization molecule) film showing a photoisomerization reaction as an organic semiconductor film. The photoisomerized molecule becomes a ring-closed body when irradiated with ultraviolet light and exhibits electrical conductivity peculiar to a semiconductor, and becomes a ring-opened body and exhibits insulating properties when irradiated with visible light. Therefore, when UV light and visible light are irradiated alternately, the photoisomerized molecule shows a reversible ring-opening-closed-ring structural change, and the pi-conjugated system changes significantly accordingly. Insulator-semiconductor transition will occur. The organic transistor of Non-Patent Document 1 performs current control by utilizing such properties of photoisomerized molecules.

  However, the organic transistor of Non-Patent Document 1 causes an insulator-semiconductor transition in the organic semiconductor film by simultaneously irradiating the entire organic semiconductor film with ultraviolet light or visible light. It is configured to form one channel. Therefore, when forming a logic circuit that realizes various operations as a device, it is necessary to use a plurality of organic transistors.

Optically and Electrically Driven Organic Thin Film Transistors with Diarythene Photochromic Channels ACS Appl. Mater. Interfaces, 5 (2013) 3625-3630

  The present invention has been made in view of the above circumstances, and an object thereof is to provide an organic transistor capable of realizing various operations by itself and an operation control method thereof.

The present invention provides the following means.
[1] An operation control method of an organic transistor provided with a photoisomerized molecular film having a ring-opened structure as a semiconductor film for forming a channel, wherein a drain voltage and a gate voltage are applied to the organic transistor, A light source of irradiation light including visible light and ultraviolet light, and an optical system that guides and irradiates a region of the irradiation light with visible light or ultraviolet light as a channel of the photoisomerized molecular film, and the channel An organic transistor operation control method, comprising: a first step of irradiating a region to be irradiated with ultraviolet light; and a second step of irradiating at least a part of the region to be the channel with visible light.
[2] The organic transistor operation control method according to [1], wherein the irradiation intensity of the ultraviolet light in the first step is 5 mW / cm ² or more and 100 mW / cm ² or less.
[3] The photoisomerizable molecule according to any one of [1] or [2], wherein a diarylethene is used as a central skeleton and pi-conjugated substituents are attached to both ends thereof. Method for controlling the operation of organic transistors.
[4] An organic transistor provided with a photoisomerized molecular film as a semiconductor film for channel formation, comprising a plurality of electrodes formed on the photoisomerized molecular film so as to be separated from each other, and the photoisomerized molecule However, in the photoisomerized molecular film, the channel region has a closed ring structure, and the other region has a ring-opened structure, and the channel region connects the electrodes. An organic transistor characterized by comprising:
[5] The organic transistor according to [4], wherein the channel region connects the electrodes to form a logic circuit.
[6] The photoisomerization molecule according to any one of [4] or [5], wherein the photoisomerized molecule has diarylethene as a central skeleton, and pi-conjugated substituents are attached to both ends thereof. Organic transistor.
[7] An operation control device for an organic transistor comprising the organic transistor according to any one of [4] to [6] and an irradiation unit for visible light and ultraviolet light, wherein the irradiation unit includes visible light And an optical system for directing and irradiating visible light or ultraviolet light of the irradiated light to a region of the photoisomerized molecular film as a channel. Transistor operation control device.

  The organic transistor of the present invention includes a photoisomerized molecular film as a semiconductor film for forming a channel. Photoisomerized molecules have the property of becoming ring-closed when irradiated with ultraviolet light and ring-opened when irradiated with visible light. The ring-closed body has electrical conductivity peculiar to semiconductors, and the ring-opened body has insulating properties. Therefore, the photoisomerized molecular film can be made into a semiconductor by irradiation with ultraviolet light, and can be made into an insulator by irradiation with visible light.

  In the organic transistor of the present invention, by utilizing the properties of photoisomerized molecules, only a specific region of the photoisomerized molecular film is irradiated with ultraviolet light, so that only the irradiated portion is made into a semiconductor, and locally. A channel can be formed. The shape of the channel can be arbitrarily designed, and can be a shape constituting a desired logic circuit.

  When a gate voltage and a drain voltage are applied, the region irradiated with ultraviolet light (channel region) is in a conductive state, but by irradiating at least part of the region with visible light, the irradiated region becomes an insulator. Therefore, this region is not conductive. By further irradiating the insulating region with ultraviolet light, this region is made semiconductor again and becomes conductive. As described above, in the organic transistor of the present invention, since the conduction state of the channel region can be switched using ultraviolet light and visible light, the current flowing through the logic circuit can be freely controlled, and as a result As a transistor, various operations can be realized.

It is a perspective view which shows typically the structure of the operation control apparatus of the organic transistor which concerns on embodiment of this invention. (A)-(c) It is a figure which shows the example of the logic circuit which can be formed in the organic transistor which concerns on embodiment of this invention. (A)-(c) It is a figure which shows the example of the logic circuit which can be formed in the organic transistor which concerns on embodiment of this invention. (A)-(c) It is a graph which shows the electrical property of the organic transistor which concerns on Example 1 of this invention. (A), (b) It is a graph which shows the electrical property of the organic transistor which concerns on Example 2 of this invention. It is a graph which shows the electrical property of the organic transistor which concerns on Example 3 of this invention.

  Hereinafter, an organic transistor which is an embodiment to which the present invention is applied and an operation control method thereof will be described in detail with reference to the drawings. In addition, in the drawings used in the following description, in order to make the features easy to understand, there are cases where the portions that become the features are enlarged for the sake of convenience, and the dimensional ratios of the respective components are not always the same as the actual ones. Absent. In addition, the materials, dimensions, and the like exemplified in the following description are examples, and the present invention is not limited to them, and can be appropriately changed and implemented without changing the gist thereof.

<First embodiment>
[Configuration of organic transistor operation control device]
FIG. 1 is a perspective view schematically showing a configuration of an organic transistor operation control apparatus 100 according to the first embodiment of the present invention. The operation control apparatus 100 includes an organic transistor 10 having a photoisomerized molecular film as a semiconductor film for forming a channel, and a visible light and ultraviolet light irradiation means (light irradiation system) 20 used to operate the transistor. doing.

[Configuration of organic transistor]
First, the configuration of the organic transistor 10 will be described. The organic transistor 10 includes a substrate 11, an insulating film 12 formed on one main surface 11 a of the substrate, a resin film 13 formed on the insulating film 12, and a photoisomerized molecule formed on the resin film 13. A film (semiconductor film) 14, and a first electrode 15 and a second electrode 16 formed so that at least one end is in contact with the photoisomerized molecular film 14 are provided.

As the substrate 11, for example, a silicon substrate (highly doped Si substrate) having a resistivity of about 0.02 Ω · cm doped with an impurity such as phosphorus (P) at a high concentration (about 10 ¹⁸ cm ⁻³ ) is used. it can. The substrate 11 functions as a gate electrode when the organic transistor operation control device 100 is operated.

As the insulating film 12, a SiO ₂ film formed by thermal oxidation is used. The thickness of the insulating film 12 is preferably 100 nm or more and 400 nm or less. The insulating film 12 functions as a gate insulating film when the operation control device 100 of the organic transistor is operated.

  The resin film 13 is made of an insulating polymer, and PMMA (acrylic resin) can be used as the material thereof. Although the resin film 13 is not an essential component, the presence of the resin film 13 eliminates the influence of defects on the insulating film 12, and promotes the n-type operation (electronic current) of the operation control device 100 of the organic transistor. Is done.

  As a material for the first electrode 105 and the second electrode 106, for example, a metal such as Au, Pt, or Pd is used. When the organic transistor operation control apparatus 100 is operated, one of the first electrode 105 and the second electrode 106 functions as a source electrode, and the other functions as a drain electrode.

  The photoisomerized molecule constituting the photoisomerized molecular film 14 has a central skeleton that exhibits a photoisomerization reaction, and has a structure in which pi-conjugated substituents are appropriately attached to both ends thereof. The photoisomerized molecule becomes a closed ring having conductivity specific to a semiconductor when irradiated with ultraviolet light, and becomes a ring-opened having insulating property when irradiated with visible light. That is, the photoisomerized molecule has a property that the molecular structure is reversibly changed between irradiation with visible light and irradiation with ultraviolet light.

  Photoisomerized molecules include diarylethene-based molecules exhibiting a ring-opening-ring-closing change, azobenzene-based molecules exhibiting a cis-trans change, and spiropyran exhibiting a polar-nonpolar change. Diarylethene, which undergoes ring-opening-closed-ring change, has a significant change in the pi-conjugated system, so that the electronic level and electrical properties change greatly, and the repeated resistance of photoisomerization reaction is higher than others. Since it is extremely excellent, it is particularly preferable as the photoisomerization molecule of this embodiment.

  Examples of the pi-conjugated substituent include a biphenyl group, a phenyl group, a thiophene ring, and a condensed ring thereof. Examples of molecular structures in which a photoisomerization molecule having a biphenyl group, a phenyl group, and a thiophene ring as a substituent in association with the photoisomerization actually showed a semiconductor-insulator transition are represented by the following chemical formulas (1) to ( Shown in 3). In each chemical formula, the left side shows a ring-opened body (insulator), and the right side shows a ring-closed body (semiconductor).

  Examples of other molecular structures that can be candidates for the photoisomerization molecule according to the present embodiment are shown in the following chemical formulas (4) to (9).

  Any of the molecular structures represented by the chemical formulas (1) to (9) has a structure in which pi-conjugated substituents are attached to both ends of the diarylethene central skeleton or a structure in which they are connected.

  The photoisomerized molecular film may be a film composed only of photoisomerized molecules, or various photoisomerized molecules may be applied to a polymer semiconductor film or a gate insulating film (matrix) composed of other than photoisomerized molecules. An added film may be used. The photoisomerized molecule may be inserted at the interface between the conventionally used organic semiconductor film and the insulating film. Photoisomerized molecules are known to induce reversible changes in the amount of current by capturing or scattering charge by a photoisomerization reaction, regardless of the configuration. It is considered that the present invention can be applied to the channel formation technology according to the above. Structural examples of molecules constituting the polymer semiconductor film are shown in the following chemical formulas (10) and (11), and structural examples of photoisomerized molecules added to the polymer semiconductor film are shown in the following chemical formulas (12) and (13 ).

  The organic transistor 10 according to the present embodiment has a bottom-gate / top-contact transistor structure using a Si substrate as a gate electrode. However, any structure can be used as long as the transistor operates and can be irradiated with light. A gate / bottom contact transistor structure may be used.

[Method of manufacturing organic transistor]
The organic transistor 10 according to the present embodiment can be manufactured mainly through the following steps 1 to 3.
[Step 1]
Thermal oxidation is performed to form an insulating film (SiO ₂ film or the like) 12 on one main surface 11a of the substrate.
[Step 2]
The photoisomerized molecular film 14 having a ring-opened body (insulator) structure is formed directly or via the resin film 13 only in a certain region on the insulating film 12 formed in Step 1 through a shadow mask by vacuum deposition. To do.
[Step 3]
A film formation process by a vacuum evaporation method, a sputtering method, or the like is performed through a shadow mask for the electrode, and the metal film for the electrode (the first electrode 15, the first electrode 15, A second electrode 16) is formed.

  Note that the photoisomerizable molecular film and the metal electrode can also be formed by a wet process such as a spin coating method, a spray method, or a micro contact printing method when the material has a meltability. In this case, it can be formed by a low-temperature process, and the technology according to the present embodiment can be developed as a technology in the field of flexible electronics by using a plastic substrate such as polyacrylate.

[Configuration of irradiation means]
Next, the configuration of the irradiation unit 20 will be described. The irradiation unit 20 includes a light source 21 of irradiation light including visible light and ultraviolet light, and an optical system 22 that guides and irradiates the region of the semiconductor film 16 where visible light or ultraviolet light is used as a channel. .

  The light source 21 includes an ultraviolet light source 21A that emits ultraviolet light and a visible light source 21B that emits visible light. The ultraviolet light source 21A and the visible light source 21B may be separate from each other or may be integrated. FIG. 1 shows an example in which two light sources are separate from each other.

  As the ultraviolet light source 21A, a light source that induces a photoisomerization reaction and that emits ultraviolet light with a wavelength of 200 to 350 nm can be used. As an example, a He—Cd laser light source that emits ultraviolet light with a wavelength of 325 nm is given. be able to. As the visible light source 21B, a light source that induces a photoisomerization reaction and that emits visible light with a wavelength of 500 to 650 nm can be used. As an example, a He—Ne laser light source that emits visible light with a wavelength of 633 nm is given. be able to.

  Examples of the case where the two light sources are integrated include a case where the light source emits light in a wavelength range including 200 to 350 nm and 500 to 650 nm (for example, an Xe lamp). In this case, for example, by using a band-pass filter to block light outside the wavelength range of the ultraviolet light or visible light, irradiation equivalent to that when the light source is a separate body can be performed. However, in this case, since it is difficult to minimize the irradiation spot diameter as in the case of using a laser light source, the resolution of optical processing performed by inducing a photoisomerization reaction is inferior.

  The optical system 22 has a shutter, a mirror, a mirror, so that visible light or ultraviolet light out of light (irradiated light) emitted from the light source 21 can be guided and irradiated to a region serving as a channel of the photoisomerized molecular film. A filter (beam splitter), a lens, and the like are appropriately arranged.

  FIG. 1 shows an example in which the optical system 22 is configured to guide irradiation light in the following procedure. First, in the shutter 23, one of the lights emitted from the two light sources 21A and 21B is selected. Next, the selected light is reflected by the mirror 24 in the direction in which the organic transistor 10 is disposed. Next, unnecessary components of the reflected light are removed by the filter 25. Then, the light from which unnecessary components have been removed is converged by a lens (objective lens) 26 and applied to the photoisomerized molecular film 14 in the organic transistor 10.

  The irradiation spot diameter can be controlled in the range of 2 to 100 μm depending on the magnification of the lens 26 and the core system of an optical fiber (not shown) for introducing laser light. Is preferred.

  The light irradiation position is controlled by relatively moving one or both of the optical system and the organic transistor. This movement can be performed using, for example, a moving stage such as an actuator type moving mechanism or a piezo mechanism.

  The actuator type moving mechanism is a drive device that induces mechanical movement such as rotational movement or translational movement by hydraulic pressure or voltage. For example, a hydraulic cylinder, an electric motor, etc. are mentioned. The piezo mechanism is a phenomenon in which when a substance is deformed by applying pressure, the substance is polarized to generate a voltage (piezoelectric effect), and a substance is deformed (expanded / contracted) by applying a voltage (inverse voltage effect). ). In particular, an element that can be slightly positioned by inducing a slight expansion and contraction in a substance by applying a voltage by utilizing a reverse voltage effect is called a piezoelectric element.

  If the moving stage uses a piezo mechanism, the positional accuracy can be further improved. However, in this case, the movable distance is limited to about 100 μm. Therefore, by performing coarse movement with a mechanical movement mechanism such as a stepping motor, fine movement with a piezo mechanism, and precise movement with a combination of multiple movement mechanisms such as a piezo mechanism, a wide range of position control and high resolution can be achieved. Processing can be compatible.

[Operation control method of organic transistor]
A method for controlling the operation of the organic transistor 10 using the above-described organic transistor operation control apparatus 100 will be described.

  First, a drain voltage and a gate voltage are applied to the organic transistor 10, and in this state, an ultraviolet region is applied to a region (channel region) serving as a channel of the photoisomerized molecular film 14 having an open ring (insulator) structure. Irradiate light (first step). Irradiation with ultraviolet light is performed using the optical system 20 described above. As a result, only the irradiated portion is transferred to the closed ring (semiconductor) structure, and the channel region is in a conductive state (ON state). At this time, the channel region functions as a transistor channel capable of modulating the drain current with the gate voltage.

The irradiation intensity and irradiation time of the ultraviolet light in the first step are preferably 5 mW / cm ² or more and 50 mW / cm ² or less and 10 seconds or more and 200 seconds or less, respectively.

  Next, visible light is irradiated to at least a part of the channel region having a closed ring structure (second step). Irradiation with visible light is also performed using the optical system 20 described above. As a result, only the irradiated portion is transferred to the ring-opened structure, and the channel region is in a state of loss of conductivity (off state). At this time, the drain current does not flow even when the gate voltage and the drain voltage are applied.

Irradiation intensity of the visible light of the second step, the irradiation time, respectively, 100 mW / cm ² or more 700 mW / cm ² or less, it is preferably not more than 600 seconds 60 seconds.

  In the first step, the channel region to which the ultraviolet light is irradiated connects the source electrode and the drain electrode, but its shape can be freely designed according to the application. For example, one or a plurality of linear shapes may be used, or a shape branched in the middle may be used. Moreover, the shape of the channel region may constitute a logic circuit as shown in FIGS.

  FIG. 2A shows a circuit diagram (left side) and a truth table (right side) when the channel region constitutes an OR circuit. Here, two source electrodes S1, S2 and one drain electrode D are connected by a transistor wire. The transistor wire extending from the drain electrode D is branched into two, and each of the branched two is marked with a circle. The position of this circle mark indicates the irradiation position of spot light (ultraviolet light, visible light). (The same applies to the circles below.)

  Since the position of the mark ○ is irradiated with visible light to form an insulator and the current path is interrupted, the path including the mark ○ is in an off state. The OR circuit here is configured such that drain current flows when the path extending from at least one of the source electrodes S1 and S2 is irradiated with ultraviolet light and the path is turned on. ing.

  FIG. 2B shows a circuit diagram (left side) and a truth table (right side) when the channel region constitutes an AND circuit. Again, the two source electrodes S1, S2 and one drain electrode D are connected by a transistor wire. The transistor wire extending from the drain electrode D is branched into two, and a circle mark is given to the branch before the branch point and the one branched toward the source electrode S1.

  Since the position of the mark ○ is irradiated with visible light to form an insulator and the current path is interrupted, the path including the mark ○ is in an off state. The AND circuit here irradiates ultraviolet light at the position marked with ○ in both the path extending to the source electrode S1 and the path extending to the drain electrode at the branch point, and these paths are turned on. Only when this occurs, the drain current flows.

  FIG. 2C shows a circuit diagram (left side) and a truth table (right side) when the channel region constitutes a NOT circuit. Here, one source electrode S and one drain electrode D are connected by a transistor wire. A circle is given in one transistor wire connecting the source electrode S and the drain electrode D.

  Since the position of the circle mark is irradiated with ultraviolet light to form a semiconductor and a current path is formed, the path including the circle mark is in an ON state. Since the NOT circuit here is in an off state when visible light is irradiated to the position of the circle, the drain current does not flow and is in an on state when no visible light is irradiated. A drain current is configured to flow.

  Since the organic semiconductor itself has no carriers, the polarity of the transistor can be controlled by the work function of the material used for the source / drain electrodes. For example, when an electrode such as gold having a work function close to the highest occupied orbit (HOMO) of the photoisomerized molecule is used as the source / drain electrode, it operates as a p-type transistor. Further, when an electrode such as magnesium or calcium having a work function close to the lowest empty orbit (LUMO) of the photoisomerization molecule is used as the source / drain electrode, it operates as an n-type transistor.

  A CMOS logic circuit that can be reconfigured by light irradiation can be realized by applying the above-described channel configuration to a transistor formed by appropriately selecting an electrode material so as to have a desired polarity.

  First, as shown in FIG. 3A, a plurality of p-type transistors T1 and n-type transistors T2 are provided. Each transistor shares a substrate and a semiconductor film (photoisomerized molecular film) but is electrically separated.

  Next, by performing local ultraviolet light irradiation as described above, the source / drain electrodes of each transistor are connected to the source / drain electrodes of the other transistors, the external power supply circuit Vdd, the ground circuit (by the optical wiring). GND) or the like to construct a logic circuit.

  As an example, FIG. 3B shows a NAND circuit constructed by connecting with an optical wiring (indicated by a wavy line). By irradiating the NAND circuit with visible light to eliminate unnecessary optical wiring, a NOR circuit can be constructed again as shown in FIG. In this way, an erasable / rewritable logic circuit can be realized by irradiating light without changing the electrode arrangement.

  As described above, the organic transistor 10 according to this embodiment includes the photoisomerized molecular film 14 as a semiconductor film for forming a channel. Photoisomerized molecules have the property of becoming ring-closed when irradiated with ultraviolet light and ring-opened when irradiated with visible light. The ring-closed body has electrical conductivity peculiar to semiconductors, and the ring-opened body has insulating properties. Therefore, the photoisomerizable molecular film 14 can be made into a semiconductor by irradiation with ultraviolet rays, and can be made into an insulator by irradiation with visible light.

  In the organic transistor according to the present embodiment, by utilizing the property of the photoisomerized molecule, by irradiating only a specific region of the photoisomerized molecular film 14 with ultraviolet light, only the irradiated portion is made into a semiconductor, A channel can be formed locally. The shape of the channel can be arbitrarily designed, and can be a shape constituting a desired logic circuit.

  When a gate voltage and a drain voltage are applied, the region irradiated with ultraviolet light (channel region) is in a conductive state, but by irradiating at least part of the region with visible light, the irradiated region becomes an insulator. Therefore, this region is not conductive. By further irradiating the insulating region with ultraviolet light, this region is made semiconductor again and becomes conductive. Thus, according to the organic transistor 10 according to the present embodiment, the conduction state of the channel region can be switched using ultraviolet light and visible light, so that the current flowing through the logic circuit can be freely controlled. As a result, a single transistor can realize various operations as a transistor.

<Second embodiment>
The structure of the operation control apparatus of the organic transistor which has an organic transistor and irradiation means based on 2nd embodiment of this invention is demonstrated. The organic transistor according to this embodiment is different from the organic transistor according to the first embodiment in that a logic circuit is formed in advance in a photoisomerizable molecular film constituting the organic transistor. Other points are the same as those of the organic transistor according to the first embodiment.

  Also in this case, the channel region constituting the logic circuit can be brought into a state in which the conductivity is lost (off state) by irradiating at least a part of the channel region with visible light. By irradiating the portion with ultraviolet light, a conductive state (on state) can be obtained. That is, the organic transistor according to the present embodiment also repeats the step of irradiating ultraviolet light (first step) and the step of irradiating visible light (second step), similarly to the organic transistor according to the first embodiment. Therefore, the operation can be controlled.

  Hereinafter, the effects of the present invention will be made clearer by examples. In addition, this invention is not limited to a following example, In the range which does not change the summary, it can change suitably and can implement.

Example 1
The basic operation of the organic transistor of the present invention will be described with reference to FIGS. The following two steps were alternately repeated for the organic transistor 10 according to the first embodiment.
(First step)
A drain voltage of −60 V (constant) and a gate voltage of 0 to 80 V are applied to the organic transistor, and in this state, a constant region serving as a channel of a photoisomerized molecular film having a ring-opened (insulator) structure is applied. The lens is scanned and irradiated with ultraviolet light having a wavelength of 325 nm. Here, the irradiation intensity of ultraviolet light was 25 mW / cm ² and the irradiation time was 180 seconds.
(Second step)
With the voltage applied, visible light having a wavelength of 633 nm is irradiated onto at least a part of the channel region having a closed ring structure by irradiation with ultraviolet light. Here, the irradiation intensity of visible light was 700 mW / cm ² and the irradiation time was 180 seconds.

As the substrate 11, a silicon substrate (highly doped Si substrate) having a resistivity of 0.02 Ω · cm doped with an impurity such as phosphorus (P) at a high concentration (about 10 ¹⁸ cm ⁻³ ) was used. As the insulating film 12, a SiO ₂ film formed by thermal oxidation was used. The thickness of the insulating film 12 was 300 nm.

  As a material for the photoisomerized molecular film 14, a material having the molecular structure of the chemical formula (1) was used. As the material for the first electrode 105 and the second electrode 106, gold was used.

  The electrical characteristics obtained with the organic transistor 10 of Example 1 will be described with reference to FIGS. FIG. 4A is a graph showing the gate voltage dependence of the drain current flowing in the organic transistor 10. The horizontal axis of the graph indicates the gate voltage [V], and the vertical axis indicates the drain current [pA]. In this graph, initial, first ultraviolet light irradiation, second ultraviolet light irradiation, third ultraviolet light irradiation,... Are displayed as 0, 2, 4, 6,. In the first visible light irradiation, the second visible light irradiation, the third visible light irradiation,... Are displayed as 1, 3, and 5, respectively. The same applies to the graph of FIG.

  In the voltage range (-30V to -60V) used as a device, the drain current when irradiated with visible light (2, 4, 6) hardly flows regardless of the gate voltage, whereas ultraviolet light is applied. In the case of irradiation (1, 3, 5), the drain current increases in proportion to the gate voltage.

  From the above results, only the portion irradiated with ultraviolet light in the photoisomerized molecular film is transferred to a closed ring, and the closed ring functions as a semiconductor material. It can be seen that it functions as a transistor channel that can modulate. From the above results, it can be seen that when visible light is scanned at the same position, a transition is made to an open ring body, that is, an insulator, so that a drain current does not flow even when a gate voltage and a drain voltage are applied.

  FIG. 4B is a graph showing how the drain current changes due to light irradiation in a state where a constant gate voltage and drain voltage are applied. The horizontal axis of the graph represents time [min], and the vertical axis represents the drain current [pA]. From this graph, by alternately irradiating visible light and ultraviolet light, the insulator-semiconductor transition occurs repeatedly, and the switching operation can be confirmed.

  FIG. 4C is a graph showing an optical switching operation in a state where a constant gate voltage and drain voltage are applied. The horizontal axis of the graph indicates the number of cycles (Drawing Cycle), and the vertical axis indicates the drain current [pA]. From this graph, it can be seen that the ON state by ultraviolet light irradiation and the OFF state by visible light irradiation can be repeatedly switched reversibly.

(Example 2)
Changes in the operation of the organic transistor due to the increase or decrease in the number of channels will be described with reference to FIGS. As a sample of the organic transistor, one having the same configuration as the organic transistor of Example 1 was used.

(Step A)
First, a drain voltage of −60 V (constant) and a gate voltage of 0 to 60 V are applied to a sample photoisomerization molecular film in a state where a channel is not formed (not written), and a current flowing at this time (drain current) ) Was measured.

(Steps B, C, D)
Next, the above voltage is applied to the photoisomerized molecular film of the same sample by irradiating ultraviolet light having a wavelength of 325 nm with one channel formed in the photoisomerized molecular film. It was measured. Similarly, by applying ultraviolet light, the above voltages were applied in the state where two channels were formed in the photoisomerized molecular film and the state where three channels were formed, and the drain current flowing at this time was measured. . Here, the irradiation intensity of ultraviolet light was 25 mW / cm ² and the sweep rate was 0.2 μm / s.

(Step E)
Next, by irradiating the photoisomerized molecular film of the same sample with visible light having a wavelength of 633 nm, one of the three channels in the photoisomerized molecular film is erased, and the above voltage is maintained with two channels remaining. The drain current flowing at this time was measured. Here, the irradiation intensity of visible light was 700 mW / cm ² and the sweep rate was 0.2 μm / s.

(Steps F and G)
Similarly, the channels in the photoisomerization molecular film are erased one by one by irradiation with visible light, and the above voltage is applied in a state where one channel remains and one channel does not remain. Each drain current was measured.

  The measurement results of Steps A to D and the measurement results of Steps D to G are shown in the graphs of FIGS. 5A and 5B, respectively. The horizontal axis of the graph indicates the gate voltage [V], and the vertical axis indicates the drain current [pA]. Steps A to G correspond to cases where the number of channels is 0, 1, 2, 3, 2, 1, 1, and 0, respectively.

  From the graph of FIG. 5A, it can be seen that in the voltage range (−30 V to −60 V) used as the device, the sum of the drain currents increases as the number of channels increases. Further, from the graph of FIG. 5B, it can be seen that in the voltage range used as the device, the total drain current decreases as the number of channels decreases.

(Example 3)
The operation of the organic transistor having a branched structure in the channel will be described with reference to FIG. As a sample of the organic transistor, one having the same configuration as the organic transistor of Example 1 was used.

  FIG. 6 shows the correspondence between nine types of states (a) to (i) of the channel region constituting the organic transistor and the drain current value obtained when the organic transistor is operated in each state. FIG. (A) to (i) will be described below.

  (A) corresponds to the initial state consisting only of the ring-opened body (insulator), and no channel is formed.

(B) corresponds to a state in which one channel is written by ultraviolet light having a wavelength of 325 nm. The irradiation intensity of ultraviolet light was 5 mW / cm ² and the sweep rate was 0.2 μm / s.

(C) corresponds to a state in which another channel is written by ultraviolet light having a wavelength of 325 nm with respect to (b). As a result, a branched structure was formed and the current path increased. The irradiation intensity of ultraviolet light was 10 mW / cm ² and the sweep rate was 0.2 μm / s. Here, by setting the irradiation intensity to about twice the irradiation intensity when forming (b), the photoisomerization rate of the added channel was increased. The resulting drain current increased due to the increased photoisomerization rate of some of the channels and increased current paths.

(D) corresponds to a state in which visible light having a wavelength of 633 nm is irradiated to one point on the channel formed first to be locally insulated. The drain current decreased as the channel formed first was insulated. The irradiation intensity of visible light was 700 mW / cm ² and the sweep rate was 0.2 μm / s. The same applies to visible light irradiation.

(E) corresponds to a state in which the portion irradiated with visible light in (d) is irradiated with ultraviolet light again. The drain current reduced by the irradiation with visible light was recovered by the irradiation with ultraviolet light. The irradiation intensity of ultraviolet light was 5 mW / cm ² and the sweep rate was 0.2 μm / s.

  (F) corresponds to the state in which the portion irradiated with visible light in (d) is irradiated with visible light again, and is in the same state as (d). Reproducibility was confirmed for the effect of irradiation with visible light.

  (G) corresponds to a state in which visible light having a wavelength of 633 nm is irradiated to one point on the channel formed in (c) and locally insulated with respect to (f). In this case, since there is no conducting current path, the configuration is the same as in the initial state (a).

  (H) corresponds to a state in which the portion irradiated with visible light in (g) is made into a semiconductor by irradiation with ultraviolet light. This state is similar to (d) and (f), and the obtained drain current is recovered to the same extent as obtained in (d) and (f).

  (I) corresponds to a state in which the portion irradiated with visible light in (f) is made into a semiconductor by irradiation with ultraviolet light. This state is similar to (c) and (e), and the obtained drain current is recovered to the same extent as obtained in (c) and (e).

  These series of data demonstrate that the organic transistor of the present invention can operate as a “light valve” type transistor capable of turning on and off a current value with light.

  The organic transistor of the present invention can be widely used in recent LSIs that are required to be downsized and multifunctional.

100 Organic Transistor Operation Control Device 10 Organic Transistor 11 Substrate 11a One Main Surface 12 of Substrate Insulating Film 13 Resin Film 14 Photoisomerization Molecular Film 15 First Electrode 16 Second Electrode 20 Irradiation Means 21 Light Source 21A Ultraviolet Light Source 21B Visible Light Source 22 Optical system 23 Shutter 24 Mirror 25 Filter 26 Lens

Claims (7)

An organic transistor operation control method comprising a photoisomerized molecular film having a ring-opened structure as a semiconductor film for channel formation,
In a state where a drain voltage and a gate voltage are applied to the organic transistor, a light source of irradiation light including visible light and ultraviolet light, and a region where visible light or ultraviolet light of the irradiation light is used as a channel of the photoisomerization molecular film An optical system that guides and irradiates
A first step of irradiating the region to be the channel with ultraviolet light;
And a second step of irradiating at least part of the region to be the channel with visible light. ^{2. The} method for controlling the operation of an organic transistor according to claim 1, wherein the irradiation intensity of the ultraviolet light in the first step is 5 mW / cm ² or more and 100 mW / cm ² or less.   The operation of the organic transistor according to claim 1 or 2, wherein the photoisomerized molecule is one having diarylethene as a central skeleton and having pi-conjugated substituents attached to both ends thereof. Control method. An organic transistor provided with a photoisomerized molecular film as a semiconductor film for channel formation,
A plurality of electrodes formed on the photoisomerized molecular film so as to be spaced apart from each other;
The photoisomerizable molecule has a ring-closed structure in the channel region and a ring-opened structure in the other region of the photoisomerized molecular film,
An organic transistor, wherein the channel region connects the electrodes.   The organic transistor according to claim 4, wherein the channel region connects the electrodes to form a logic circuit.   6. The organic transistor according to claim 4, wherein the photoisomerized molecule has diarylethene as a central skeleton, and pi-conjugated substituents are attached to both ends thereof. An organic transistor operation control device comprising: the organic transistor according to any one of claims 4 to 6; and irradiation means for visible light and ultraviolet light.
The irradiation means includes a light source of irradiation light including visible light and ultraviolet light, and an optical system that guides and irradiates visible light or ultraviolet light of the irradiation light to a region of the photoisomerized molecular film. An operation control apparatus for an organic transistor, comprising:

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