JP2005322787A - Organic thin-film transistor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an organic thin-film transistor and a switching element, capable of largely modulating the current between the source electrode and the drain electrode by gate voltage, permitting a large current to flow between the source electrode and the drain electrode, and of stably operating in the atmosphere. <P>SOLUTION: The thin-film transistor has a region with a channel between the source electrode and the drain electrode formed, which has a structure consisting of an organic semiconductor compound comprising at least one or more mettalocene skeleton regions, and a five-membered heterocyclic aromatic ring, a six-membered aromatic ring or a condensed aromatic ring thereof. A switching element made of the thin-film transistor is also provided. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a thin film transistor using an organic semiconductor and a switching element including the thin film transistor.

  Thin film transistors (hereinafter referred to as TFTs) with organic active layers and printed electronic components have attracted attention as an inexpensive alternative to silicon-based TFTs in several fields. By using an organic material, such a device can be fabricated without the costly steps required in a process using silicon. Other advantages include improved mechanical flexibility and easy adjustment of the organic base device for the thin film transistor formed on the silicon substrate. The characteristics of organic-based devices do not match the characteristics of silicon-based TFTs under extreme conditions (for example, high and low temperatures) in terms of device density and reliability. However, organic base TFTs are useful when economy is prioritized over density and reliability under extreme conditions.

Various organic materials have been proposed as semiconductor materials for organic-based TFTs. As a TFT using an organic semiconductor material having a particularly high hole mobility, for example, a TFT using pentacene reported in Non-Patent Document 1 can be cited. In this case, carrier mobility of about 1 to ² cm ² / Vs is obtained, and a high value is also obtained for the source-drain current when on. However, as reported in Non-Patent Document 2, since pentacene deteriorates in the atmosphere, stable operation cannot be obtained for a long time, and it is difficult to put it to practical use. In addition, since pentacene film formation is based on a vapor deposition method, a large-scale facility such as a vacuum film forming apparatus is required, which impairs the above-described economic advantages.

As TFTs using other organic semiconductor materials, there are TFTs using a polyregular body of poly (3-hexylthiophene) reported in Non-Patent Document 3. However, the carrier mobility of the TFT reported here is 0.1 cm ² / Vs at the maximum, and the source-drain current at the time of on has not yet obtained a high value. In addition, poly (3-hexylthiophene) regioregular bodies are prominent in doping with oxygen, and the off-current tends to increase, and the current flowing between the source and drain electrodes is modulated by the voltage applied to the gate electrode in the atmosphere. The width is only about 3 digits.

Patent Document 1 discloses a TFT having an active layer made of an organic semiconductor compound having a structure in which two or three six-membered rings and three condensed aromatic rings are condensed with a five-membered heteroaromatic ring. It is disclosed. However, the carrier mobility of this TFT is as low as about 0.1 cm ² / Vs, and the on / off ratio does not satisfy the required four digits.

  As described above, any TFT using a conventional organic semiconductor material has poor stability in the atmosphere, has a small on / off ratio, and has not yet achieved a high value of source-drain current when on. Therefore, in a TFT using an organic semiconductor, flowing a large source-drain current and increasing the modulation width of this current are problems in improving the characteristics of the TFT.

JP-A-11-195790 Appl. Phys. Lett. , Vol. 81, p. 268 (2002) Appl. Phys. Lett. , Vol. 83, p. 1644 (2003) SCIENCE, vol. 280, p. 1741 (1998)

  The present invention has been made in order to solve the above-described problems, in which the current between the source electrode and the drain electrode is more greatly modulated by the gate voltage, and between the source electrode and the drain electrode. It is an object of the present invention to provide an organic thin film transistor capable of flowing a large current in the air and operating stably in the atmosphere.

  In the thin film transistor in which the conductivity of the channel between the source electrode and the drain electrode is controlled by the gate voltage applied to the gate electrode, the region where the channel is formed includes at least one metallocene skeleton site, and 5 The present invention relates to a thin film transistor made of an organic semiconductor compound having a structure composed of a membered heteroaromatic ring, a six-membered aromatic ring, or a condensed aromatic ring thereof.

  The organic semiconductor compound preferably has a structure in which the number of aromatic rings is 2 to 4 and ferrocene is bonded to both ends. The organic semiconductor compound has the formula (1):

{Wherein, R ^{1 to} R ⁶ are a hydrogen atom, an alkyl group (—C _n H _{2n + 1} , n is an integer of 1 to 10) or an alkoxy group (—OC _n H _{2n + 1} , n is 1 to 10 Integer). } Is more preferable.

  The organic semiconductor compound has the formula (2):

More preferably, the structure is as shown in FIG.

  The thin film transistor having the organic semiconductor compound can be advantageously used for manufacturing various devices such as a switching element, and particularly, when used as a switching element material, the thin film transistor is favorably switched.

  ADVANTAGE OF THE INVENTION According to this invention, the organic thin-film transistor which has a high field effect mobility and high on / off ratio, and operate | moves stably in air | atmosphere can be provided.

Embodiment 1
The thin film transistor of the present invention is a thin film transistor in which the conductivity of a channel between a source electrode and a drain electrode is controlled by a gate voltage applied to the gate electrode, and the region where the channel is formed has at least one metallocene skeleton site , And a 5-membered heteroaromatic ring, a 6-membered aromatic ring, or an organic semiconductor compound having a structure composed of a condensed aromatic ring thereof.

  The thin film transistor of the present invention will be described with reference to FIG. FIG. 1 is a cross-sectional view of a thin film transistor of the present invention, wherein 1 is an organic semiconductor thin film that becomes an active layer, 2 is a source electrode, 3 is a drain electrode, 4 is a gate insulating film, 5 is a gate electrode, and 6 is a substrate. It is. Note that the thin film transistor of the present invention may be of any type such as a junction type or an insulated gate type. Here, a case where the thin film transistor is applied to an insulated gate type will be described.

  The organic semiconductor thin film 1 forming a channel between the source electrode 2 and the drain electrode 3 includes at least one metallocene skeleton site, a 5-membered heteroaromatic ring, a 6-membered aromatic ring, or a condensed fragrance thereof. It consists of an organic semiconductor compound having a structure composed of a group ring.

  The organic semiconductor compound used in the present invention has at least one, preferably two metallocene skeleton sites. By having one or more metallocene skeleton sites, the organic semiconductor compound includes a redox (oxidation-reduction) active site as a constituent element, and this redox active site can easily generate a polaron by applying an external voltage. Therefore, field effect mobility and on / off ratio can be improved. Examples of the metallocene skeleton site include ferrocene, ruthenocene, osmocene, and manganocene. Among these, ferrocene is preferable from the viewpoints of heat resistance, stability in the atmosphere, and easy generation of polaron by application of an external voltage.

  Examples of the 5-membered heteroaromatic ring include thiophene and selenophene. Among these, thiophene is preferable from the viewpoint of particularly high carrier conductivity.

  Examples of the 6-membered aromatic ring include phenylene.

  Examples of the condensed aromatic ring composed of a 5-membered heteroaromatic ring or a 6-membered aromatic ring include fluorene, naphthalene, anthracene, tetracene, and pentacene.

  The organic semiconductor compound used in the present invention may be composed of any one of the 5-membered heteroaromatic ring, the 6-membered aromatic ring, and the condensed aromatic ring. Like the organic semiconductor compound comprised from a 6-membered aromatic ring and a 6-membered aromatic ring, you may be comprised from 2 or more types of a different aromatic ring. The number of aromatic rings in the organic semiconductor compound is preferably 2 to 4, more preferably 3. When the number of aromatic rings is 1, polaron is hardly generated, and when the number is 5 or more, field effect mobility tends to be small.

The organic semiconductor compound used in the present invention has a structure composed of at least one metallocene skeleton site and a 5-membered heteroaromatic ring, a 6-membered aromatic ring, or a condensed aromatic ring thereof. However, the hydrogen atom of the metallocene skeleton site or the aromatic ring may be substituted with an alkyl group (—C _n H _{2n + 1} ), an alkoxy group (—OC _n H _{2n + 1} ) or the like. By substituting with these groups, the organic semiconductor compound is preferable because it becomes soluble in various solvents, can improve the film-forming property, and can optimize the intermolecular arrangement. Here, n represents an integer of 1 to 10. When n is 11 or more, there is a tendency that the steric hindrance of the molecule is caused and the charge transfer between the molecules is prevented.

  The organic semiconductor compound used in the present invention is preferably a compound represented by the formula (1) from the viewpoint of carrier conductivity.

In the formula, R ^{1 to} R ^{6 each} represents a hydrogen atom, an alkyl group (—C _n H _{2n + 1} ) or an alkoxyalkyl group (—OC _n H _{2n + 1} ). n represents an integer of 1 to 10.

  The organic semiconductor compound used in the present invention is particularly preferably a compound represented by the formula (2) from the viewpoint of carrier conductivity.

The method for producing the organic semiconductor compound used in the present invention is not particularly limited. For example, in the compound represented by the formula (1), when R ^{1 to} R ⁶ are hydrogen atoms, a pentane solution of tertiary butyl lithium is added to a THF solution of ferrocene under an inert argon atmosphere, 5 ″ -dibromo-2,2 ′: 5 ′, 2 ″ -terthiophene in THF can be added and reacted. 5,5 ″ -Dibromo-2,2 ′: 5 ′, 2 ″ -terthiophene added solid N-bromosuccinimide to a dichloromethane solution of 5-bromo-2,2 ′: 5 ′, 2 ″ -terthiophene And can be obtained by reacting.

  In addition, the organic semiconductor compounds represented by the formula (2), the formula (3), the formula (4), and the formula (5) are described in Jpn. J. et al. Appl. Phys. , Vol. 39, p. It can be produced with reference to the method described in L939 (2000). For example, the organic semiconductor compound represented by the formula (2) is 5,5 ″ -diiodo-3,3 ″ -dimethoxy-2,2 ′: 5 ′, 2 in the presence of dichloro (bistriphenylphosphine) as a catalyst. It can be obtained by coupling -terthiophene and ferrocenyl zinc chloride in a THF solvent. The organic semiconductor compound represented by the formula (3) is also described in Jpn.J.Appl.Phys., Vol. 38, p.L1073 (1999).

  The thin film transistor of the present invention is manufactured by, for example, forming the gate insulating film 4 on the gate electrode 5 on the substrate 6, forming the source electrode 2 and the drain electrode 3, and finally forming the organic semiconductor thin film 1. can do.

  As a material for forming the substrate 6, an insulating material can be used. Specifically, various inorganic insulating materials such as quartz, glass, and alumina sintered body, various insulating plastics such as polyimide film, polycarbonate film, polyester film, polyethylene film, polyphenylene sulfide film, polyparaxylylene film, etc. It can be used.

  As a material for forming the source electrode 2, the drain electrode 3, and the gate electrode 5, any material having conductivity can be used. Specifically, gold, silver, copper, platinum, chromium, palladium, aluminum, indium, chromium, molybdenum, tungsten, nickel and other metals, platinum silicide, palladium silicide, low resistance polysilicon, low resistance amorphous silicon, carbon, In general, conductive inorganic materials such as tin oxide, indium oxide, and indium tin oxide (ITO), organic low-molecular compounds having conductivity, and conductive π-conjugated polymers are used. Of course, it is not limited to these materials, and two or more of these materials can be used. Among these, as the source electrode 2 and the drain electrode 3, those having a low electric resistance particularly on the contact surface with the semiconductor layer are preferable.

  The method for forming the gate electrode 5 is not particularly limited, and examples thereof include a vacuum deposition method, a sputtering method, a plating method, a chemical vapor deposition (CVD) method, a Langmuir-Blodget (LB) method, a spin coating method, and an electrolytic polymerization method. It can be used.

  As a material for forming the gate insulating film 4, any of an inorganic material and an organic material can be used as long as it is insulative. Generally, silicon oxide, silicon nitride, aluminum oxide, aluminum nitride, titanium oxide, polyethylene, polyester, polyimide, polymethyl methacrylate, polyvinyl phenol, polyphenylene sulfide, polyparaxylylene, polyacrylonitrile, various insulating LB films, etc. Is used. Two or more of these materials may be used in combination. There is no restriction | limiting in particular as a preparation method of the gate insulating film 4, For example, a sputtering method, CVD method, plasma CVD method, plasma polymerization method, vapor deposition method, spin coating method, dipping method, cluster ion beam vapor deposition method, LB method etc. Can be given. When a silicon wafer is used as both the gate electrode 5 and the substrate 6, a silicon oxide film obtained by a silicon thermal oxidation method or the like is preferable as the gate insulating film 4.

  The source electrode 2 and the drain electrode 3 can be formed by, for example, a vacuum deposition method, a sputtering method, a plating method, a CVD method, an LB method, a spin coating method, an electrolytic polymerization method, and the like. Absent.

  The organic semiconductor thin film 1 can be produced by vacuum deposition, molecular beam epitaxial growth, ion cluster beam method, low energy ion beam method, ion plating method, CVD method, sputtering method, plasma polymerization method, electrolytic polymerization method, chemical method. Examples include a polymerization method, a spin coating method, a casting method, a dipping method, a roll coating method, a bar coating method, and an LB method, which can be used according to the purpose. However, among these, a spin coating method, a casting method, a dipping method, a roll coating method, a bar coating method and the like that can easily form a thin film are preferred in terms of productivity. Although there is no restriction | limiting in particular as the film thickness of the organic-semiconductor thin film 1 which consists of organic-semiconductor compounds, Since the characteristic of the transistor obtained is largely influenced by the film thickness of the active layer which consists of an organic-semiconductor compound in many cases, film thickness Is preferably 3000 angstroms or less.

  Further, the gate electrode 5 and the substrate 6 may be replaced with one p-type silicon substrate or n-type silicon substrate. In this case, the substrate 6 can be omitted. The volume specific resistivity of the p-type silicon substrate or the n-type silicon substrate is not particularly limited, but is practically preferably smaller than the volume specific resistivity of the organic semiconductor thin film 1. Furthermore, depending on the purpose of use of the TFT shown in FIG. 1, the gate electrode 5 and the substrate 6 can be replaced with a conductive plate or film such as a stainless plate, a copper plate, or a conductive polymer.

The carrier mobility of the thin film transistor of the present invention is preferably 0.1 cm ² / Vs or more, more preferably 0.3 cm ² / Vs or more. When the carrier mobility is less than 0.1 cm ² / Vs, the amount of current that can be driven by the transistor becomes small. For example, when used as a switching element of an image display device such as a liquid crystal, the transistor size must be increased, and the pixel aperture ratio Lead to a decline.

Further, the on / off ratio is preferably 10 ⁴ or more, and more preferably 10 ⁵ or more. When the on / off ratio is less than 10 ⁴ , the off resistance of the transistor is not sufficiently high. For example, when used as a switching element of an image display device such as a liquid crystal, the charged pixel charge cannot be held.

  The thin film transistor of the present invention can be used in a switching element that controls driving of an image display device such as a liquid crystal, or an IC circuit in which an inverter is integrated and integrated.

Embodiment 2
One embodiment of a thin film transistor of the present invention will be described with reference to FIG. FIG. 2 is a cross-sectional view of a liquid crystal display device using the thin film transistor of the present invention as a switching element.

  As shown in FIG. 2, the gate electrode 5 is formed on the upper surface of the left half of the substrate 6, and the gate insulating film 4 is formed on the entire upper surface of the substrate 6 and on the gate electrode 5. A source electrode 2 and a drain electrode 3 are formed on the upper surface of the left half of the gate insulating film 4, and an electrode 7 is formed on the upper surface of the right half of the gate insulating film 4. The electrode 7 is connected to the drain electrode 3. Furthermore, the organic semiconductor thin film 1 made of the organic semiconductor material according to the present invention is formed on the source electrode 2 and the drain electrode 3 and on the gate insulating film 4 around them. The organic semiconductor thin film 1 forms a channel formation region between the source electrode 2 and the drain electrode 3. From the substrate 6, the gate electrode 5, the gate insulating film 4, the source electrode 2, the drain electrode 3, and the organic semiconductor thin film 1. A driving unit 11A having a TFT is configured.

  A liquid crystal layer 8 is formed on the electrode 7 and the organic semiconductor thin film 1, and a transparent electrode 9 is formed on the upper surface of the liquid crystal layer 8 above the electrode 7. A glass plate 10 with a polarizing plate is formed on the liquid crystal layer 8 and the transparent electrode 9, and the electrode 7 and the transparent electrode 9 are subjected to alignment treatment. The electrode 7, the liquid crystal layer 8, the transparent electrode 9, and the glass plate 10 constitute a liquid crystal display unit 11 </ b> B, and the liquid crystal display unit 11 </ b> B is driven by turning on and off the TFT by controlling the gate voltage to the gate electrode 5.

  In the TFT in FIG. 2, the material for forming the organic semiconductor thin film 1, the source electrode 2, the drain electrode 3, the gate insulating film 4, the gate electrode 5, and the substrate 6 is the same material as the thin film transistor described in the first embodiment. It can be used, and the formation method is the same.

  The material of the electrode 7 connected to the drain electrode 3 of the TFT is not particularly limited as long as it has sufficient conductivity and is insoluble in the liquid crystal. For example, a metal such as gold, platinum, chromium, aluminum or tin A transparent conductive material such as an oxide, indium tin oxide (ITO), or an organic polymer having conductivity may be used. Of course, two or more of these materials may be combined. However, the electrode 7 needs to be subjected to orientation treatment such as oblique deposition of SiO or rubbing.

  The electrode 7 can be formed by sputtering or the like when using ITO, and spin coating or the like when using a conductive polymer.

  As the liquid crystal layer 8, a well-known guest-host (GH) type liquid crystal, twisted nematic (TN) type liquid crystal, smectic C phase liquid crystal or the like is used. When glass is used for the substrate 6 and a transparent conductive material is used for the electrode 7, the contrast ratio can be increased by attaching a polarizing plate to the substrate 6.

  The liquid crystal layer 8 can be formed, for example, by injecting into a space formed by sandwiching a spacer between the upper and lower substrates using a capillary phenomenon.

  Moreover, as a material of the transparent electrode 9, it is common to use a transparent conductive material such as tin oxide, indium oxide, ITO, and a conductive organic polymer having appropriate transparency may be used. Two or more of these materials may be combined. However, the transparent electrode 9 needs to be subjected to orientation treatment such as oblique deposition of SiO or rubbing.

  The transparent electrode 9 can be formed by sputtering if ITO is used, or by spin coating if conductive polymer is used.

  As a polarizing plate used for the glass plate 10 with a polarizing plate, any polarizing plate can be used without particular limitation.

  Further, a protective film for the purpose of protecting the entire element may be provided on the organic semiconductor thin film 1, and in this case, an organic and / or inorganic insulating material is used for the protective film.

  Further, when the substrate 6 and the gate electrode 5 are formed of silicon, a silicon oxide film obtained by a silicon thermal oxidation method or the like can be used as the gate insulating film 4.

  The operation of the liquid crystal display device shown in FIG. 2 will be described.

  The case where the organic semiconductor compound forming the organic semiconductor thin film 1 exhibits p-type characteristics will be described. A negative voltage is applied to the transparent electrode 9 with the source electrode 2 as a reference, and a negative gate voltage is applied to the gate electrode 5. As a result, the resistance between the source electrode 2 and the drain electrode 3 decreases, the TFT is turned on, and the drain electrode 3 and the electrode 7 are connected in series. A predetermined display is performed on the display unit 11B.

  Next, when the application of the gate voltage is stopped, the resistance between the source electrode 2 and the drain electrode 3 is increased, the TFT is turned off, no voltage is applied to the liquid crystal layer 8, and the display on the liquid crystal display unit 11B is turned off. In this way, the driving of the liquid crystal display unit 11B can be controlled by turning on and off the TFT of the driving unit 11A by controlling the gate voltage.

  Even when the organic semiconductor thin film 1 exhibits n-type characteristics, the driving of the liquid crystal display unit 11B can be controlled by controlling the gate voltage in the same manner.

  Therefore, by using the thin film transistor of the present invention as a switching element, a low-cost liquid crystal display device having excellent performance can be obtained.

  Examples of the present invention will be described below, but the present invention is not limited thereto.

  In the examples, carrier mobility and on / off ratio were measured as follows.

Method for Measuring Carrier Mobility The carrier mobility (μ) of the thin film transistor is measured by measuring the drain current I _SD in the saturation region (gate voltage V _G <source-drain voltage V _SD ) in a dark box. It was decided according to.
I _SD = C _i μ (W / 2L) (V _G −V _T ) ²

Here, W and L are each channel width and length of the semiconductor, C _i is the capacitance per unit area of the gate dielectric layer, V _G is the gate voltage, the V _T indicates a threshold voltage. The threshold voltage V _T of the device used in the measurement, with respect to any gate voltage V _G, plotting the square root of I _SD at the saturated regime, extrapolating the straight line obtained by the plotting to I _SD = 0, I _SD It is obtained from the value of V _G when = 0.

on / off ratio of the measurement method a thin film transistor for on / off ratio, and drain current when the saturation drain current and the gate voltage V _G is zero when the gate voltage V _G is greater than or equal to the drain voltage V _D Ratio.

Example 1
A chromium thin film pattern having a thickness of 1000 angstroms was formed on a non-alkali glass wafer having a diameter of 2 inches and a thickness of 0.7 mm as a substrate by using an ordinary vapor deposition method, a photolithographic method, and an etching method. A SiO _x insulating film having a thickness of 5000 angstroms was formed thereon using a normal vapor deposition method and a mask method. Next, an indium tin oxide (ITO) thin film pattern having a thickness of 1000 angstroms was formed on the insulating film by using a normal vapor deposition method and a photolithographic method. An organic semiconductor material thin film was formed on the substrate thus prepared by spin coating using a solution obtained by dissolving the organic semiconductor compound represented by the formula (2) in chloroform to obtain the thin film transistor of the present invention.

The obtained thin film transistor is formed of an insulated gate field effect transistor and has a cross section as shown in FIG. In this case, 1 is an organic semiconductor thin film serving as an active layer, 2 is an ITO film serving as a source electrode, 3 is an ITO film serving as a drain electrode, 4 is a SiO ₂ vapor deposition film serving as a gate insulating film, and 5 is a gate electrode. A chromium film 6 is a glass wafer element substrate. The channel width (W) and channel length (L) of the thin film transistor were 2 mm and 5 μm, respectively.

Regarding the electrical characteristics of the manufactured thin film transistor, the carrier mobility was 0.1 cm ² / Vs, and the on / off ratio was 2 × 10 ⁵ . Even after the thin film transistor was stored in the atmosphere for 5 days, no deterioration in performance was observed.

Example 2
A SiO ₂ film having a thickness of about 300 nm was formed on the surface of the n-doped silicon wafer by thermal oxidation. In this substrate, a silicon wafer functions as a gate electrode, while the SiO ₂ film functions as a gate insulating film. A gold thin film pattern having a thickness of 500 angstroms was formed thereon by using a normal vapor deposition method and a photolithographic method, and used as source and drain electrodes. On top of this, the same organic semiconductor thin film as in Example 1 was formed by a vacuum deposition method and a spin coating method to obtain a thin film transistor of the present invention. The transistor had a channel width (W) and a channel length (L) of 2 mm and 9 μm, respectively.

Example 3
The same substrate and electrode as in Example 2 were prepared, and an organic semiconductor material thin film represented by the formula (3) was formed thereon by a vacuum vapor deposition method and a spin coating method to obtain the thin film transistor of the present invention.

Example 4
A substrate and an electrode similar to those in Example 2 were prepared, and an organic semiconductor material thin film made of an organic semiconductor compound represented by the formula (4) was formed thereon by a vacuum deposition method and a spin coating method to obtain the thin film transistor of the present invention. It was.

Example 5
A substrate and an electrode similar to those in Example 2 were prepared, and an organic semiconductor material thin film made of an organic semiconductor compound represented by the formula (5) was formed thereon by a vacuum vapor deposition method and a spin coating method to obtain the thin film transistor of the present invention. It was.

  In Examples 2 to 5, Table 1 shows electrical characteristics of the thin film transistors manufactured by the vacuum evaporation method and the spin coating method.

  In addition, the thin film transistors manufactured in Examples 2 to 5 were not deteriorated in performance after being stored in the atmosphere for 5 days.

Example 6
The same substrate and electrode as in Experimental Example 2 were prepared, and an organic semiconductor material thin film made of an organic semiconductor compound represented by the formula (6) was formed thereon by a vacuum deposition method, to obtain the thin film transistor of the present invention.

Example 7
A substrate and electrodes similar to those of Experimental Example 2 were prepared, and an organic semiconductor material thin film made of an organic semiconductor compound represented by the formula (7) was formed thereon by a vacuum deposition method to obtain the thin film transistor of the present invention.

Example 8
The same substrate and electrode as those of Experimental Example 2 were produced, and an organic semiconductor material thin film made of an organic semiconductor compound represented by the formula (8) was formed thereon by a vacuum deposition method to obtain the thin film transistor of the present invention.

Example 9
The same substrate and electrode as in Experimental Example 2 were prepared, and an organic semiconductor material thin film made of an organic semiconductor compound represented by the formula (9) was formed thereon by a vacuum deposition method, to obtain the thin film transistor of the present invention.

  In Examples 6 to 9, electrical characteristics of the thin film transistors manufactured by the vacuum evaporation method are shown in Table 2.

It is the figure which showed sectional drawing of the organic thin-film transistor of this invention. It is sectional drawing of the liquid crystal display device which used the organic thin-film transistor of this invention as a switching element.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Organic-semiconductor thin film 2 Source electrode 3 Drain electrode 4 Gate insulating film 5 Gate electrode 6 Substrate 7 Electrode 8 Liquid crystal layer 9 Transparent electrode 10 Glass plate with a polarizing plate 11A Drive part 11B Liquid crystal display part

Claims (5)

In a thin film transistor in which the conductivity of a channel between a source electrode and a drain electrode is controlled by a gate voltage applied to a gate electrode, a region where the channel is formed includes at least one metallocene skeleton portion and a five-membered ring complex. A thin film transistor comprising an organic semiconductor compound having a structure composed of an aromatic ring, a 6-membered aromatic ring, or a condensed aromatic ring thereof. 2. The thin film transistor according to claim 1, wherein the metallocene skeleton is ferrocene. The organic semiconductor compound has the formula (1):

{Wherein R ^{1 to} R ^{6 each} represents a hydrogen atom, an alkyl group (—C _n H _{2n + 1} ) or an alkoxy group (—OC _n H _{2n + 1} ). n represents an integer of 1 to 10. The thin film transistor according to claim 2, wherein The organic semiconductor compound has the formula (2):

The thin film transistor according to claim 3, which is a compound represented by the formula: A switching element comprising the thin film transistor according to claim 1.

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