JPH0638492B2 - Field effect transistor - Google Patents

Description

TECHNICAL FIELD The present invention relates to a field effect transistor (hereinafter abbreviated as FET element) using an organic semiconductor.

[Conventional technology]

A π-conjugated polymer has a chemical structure consisting of conjugated double bonds and conjugated triple bonds, and is a band composed of a valence band and a conduction band formed by overlapping π-electron orbitals and a forbidden band separating them. It is believed to have a structure. The band gap depends on the material, but is in the range of 1.5 to 4 eV for most π-conjugated polymers. For this reason, many π-conjugated polymers are insulators by themselves. However, it is possible to remove electrons from the valence band (oxidation) by chemical methods, electrochemical methods, physical methods, etc.
Alternatively, injecting (reducing) electrons into the conduction band (hereinafter,
It is briefly described that a carrier carrying an electric charge is generated by (called doping). As a result, the conductivity can be varied over a wide range from the insulator region to the metal region by controlling the amount of doping. The polymer obtained when the doping reaction is an oxidation reaction is p-type, and when the doping reaction is a reduction reaction, it is n-type. This is similar to the case of adding impurities in an inorganic semiconductor. Therefore, a semiconductor element using a π-conjugated polymer as a semiconductor material can be manufactured.

Specifically, a Schottky junction device using polyacetylene (Journal of Applied Phys. 52, 869, 1981, JP-A-56-14)
7486), and Schottky type junction devices using polypyrrole-based conjugated polymers (JP-A-59-63760, etc.) are known. Further, a heterojunction device in which n-CdS which is an inorganic semiconductor and p-type polyacetylene are combined has been reported (J. Appl. Phys. 51, 4252, 1980). π
-As a joining element that combines conjugated polymers,
A pn homojunction device using p-type and n-type polyacetylene is known (Appl. Phys. Lett. 33:18, 1978). In addition, a heterojunction device composed of polyacetylene and poly (N-methylpyrrole) has been reported (J. Appl. Phy
s. 58, 1279 1985).

On the other hand, an FET using a π-conjugated polymer as a semiconductor layer
As an element, polyacetylene (J. Appl. 54, 3255
Page, 1983) and poly (N-methylpyrrole) (Polymer Preprints Japan
Japan), Vol. 34, No. 4, 917, 1985).

FIG. 2 is a cross-sectional view of a conventional FET device using polyacetylene.

In the figure, 1 is glass serving as a substrate, 2 is an aluminum film serving as a gate electrode, 3 is a polysiloxane film serving as an insulating film, 4 is a polyacetylene film serving as a semiconductor layer, and 5 and 6 are source and drain electrodes, respectively. It is a gold film.

Next, the operation will be described. When a voltage is applied between the source electrode 5 and the drain electrode 6, a current flows between the source electrode 5 and the drain electrode 6 through the polyacetylene film 4. At this time, if a voltage is applied to the gate electrode 2 provided on the glass substrate 1 and separated from the polyacetylene film 4 by the insulating film 3, the electric conductivity of the polyacetylene film 4 can be changed by the electric field effect, and therefore the source-drain can be changed. Current can be controlled. It is considered that this is because the width of the depletion layer in the polyacetylene film 4 adjacent to the insulating film 3 changes depending on the voltage applied to the gate electrode 2 and the effective channel cross-sectional area of holes changes. However, in this FET device, the stability of the device itself is extremely poor because the polyacetylene itself is rapidly deteriorated by oxygen and moisture in the air rather than the problem of device characteristics.

FIG. 3 shows a cross-sectional view of an FET element having poly (N-methylpyrrole) as a semiconductor layer. In the figure, 3 is silicon oxide which serves as an insulating film, and 4 is poly (N) which functions as a semiconductor layer.
-Methylpyrrole) films 5 and 6 are gold films serving as a source electrode and a drain electrode, respectively, and 7 is a substrate / gate electrode. It is p-type silicon. Also in this case, the current (electric conductivity) flowing between the source electrode 5 and the drain electrode 6 through the semiconductor layer 4 can be controlled by the voltage applied to the gate electrode.

[Problems to be solved by the invention]

However, in the case where the π-conjugated polymer film such as polyacetylene or poly (N-methylpyrrole) is used only for the semiconductor layer of the FET element, the conductivity between the source and the drain is changed depending on the voltage applied from the gate. It cannot be changed greatly, and from the practical point of view, improvement of characteristics has been demanded.

The present invention has been made in order to solve the above problems, and obtains an FET element that operates stably and can greatly change the conductivity between the source and drain by the voltage applied from the gate. The purpose is to

[Means for Solving the Problems] In the FET element according to the present invention, the source is the first π-conjugated polymer film and the drain is the same as or different from the first π-conjugated polymer film. It is composed of a second π-conjugated polymer film, and a semiconductor layer which is a current path is further provided with first and second π-conjugated polymer films.
It is composed of a third π-conjugated polymer film different from the conjugated polymer film.

[Action]

In the present invention, the conventional π-conjugated polymer is used only in the semiconductor layer which is the current passage by using the π-conjugated polymer in the semiconductor layer which is the source, drain and current passage in the FET device. FE compared to the case
It is possible to operate the T element with significantly superior characteristics to the conventional element.

〔Example〕

FIG. 1 shows an example of the structure of the FET element of the present invention. In the figure, 1 is a substrate, 2 is a metal film provided as a gate electrode on the substrate 1, 3 is an insulating film, 4 is a π-conjugated polymer film that serves as a semiconductor layer, and 10 and 11 are respectively A π-conjugated polymer film acting as a source and a drain, and 8 and 9 are metal films acting as lead wires of the source and the drain, respectively.

Here, the materials used in the present invention are as follows.

Any material can be used for the substrate 1 as long as it is an insulating material, and specifically, various insulating plastics such as glass, an alumina sintered body, a polyimide film, and a polyester film can be used. The metal film 2 that functions as a gate electrode and the metal films 8 and 9 that function as lead wires from the source and drain include metals such as gold, platinum, chromium, palladium, aluminum and indium, tin oxide, indium oxide, indium tin. Oxide (ITO)
Etc. are generally used, but the materials are not limited to these materials, and two or more kinds of these materials may be used. Here, as the method of providing the metal film, there are methods such as vapor deposition, sputtering, plating, and CVD growth.

In general, it is practically preferable that the metal films 8 and 9 are in ohmic contact with the π-conjugated polymer films 10 and 11, respectively.

In the FET element of the present invention shown in FIG. 1, p-type silicon or n-type silicon can be used as both the gate electrode 2 and the substrate 1. In this case, the substrate 1 can be omitted. Further, in this case, the volume resistivity of p-type silicon or n-type silicon is π− used as the semiconductor layer.
It is practically preferable that the size is smaller than that of the conjugated polymer. Furthermore, a conductive organic polymer may be used as the gate electrode. It is also possible to use a metal plate such as a stainless steel plate or a copper plate, which doubles as the gate electrode 2 and the substrate 1, depending on the purpose of use.

The insulating film 3 can be made of any inorganic or organic material as long as it is insulative. In general, silicon oxide (SiO ₂ ), silicon nitride, aluminum oxide, polyethylene, polyvinylcarbazole, polyphenylene. Sulfide, polyparaxylene, etc. are used. As a method for forming these insulating films, there are a CVD method, a plasma CVD method, a vapor deposition method, a spin coating method, a cluster ion beam vapor deposition method and the like, and any method can be used. Furthermore, the LB single molecule accumulation method can also be used. When p-type silicon or n-type silicon is used as the gate electrode 2 and the substrate 1, a silicon oxide film obtained by a thermal oxidation method of silicon or the like is preferably used as the insulating film 3.

The π-conjugated polymer used in the present invention can be any π-conjugated polymer, and specifically, polypyrrole, poly (N-substituted pyrrole), poly (3,4-
Disubstituted pyrrole), poly (3-substituted pyrrole), polythiophene, poly (3-substituted thiophene), poly (3,4)
-Disubstituted thiophene), polyaniline, polyazulene,
Polypyrene, polycarbazole, poly (N-substituted carbazole), polyselenophene, polyfuran, polybenzothiophene, poly (phenylene vinylene), polybenzofuran, poly (paraphenylene), polyindole, polyisothionaphthene, polypyridazine, polydiene Examples thereof include acetylenes and graphite polymers, but are not limited to these. However, a π-conjugated polymer having a five-membered heterocyclic ring is preferably used because of the FET characteristics, film-forming property, and easiness of synthesis. (However, X is one of S and O atoms, R ₁ and R ₂ are one of —H, —CH ₃ , —OCH ₃ , —C ₂ H ₅ and —OC ₂ H ₅ groups, and n is Which is an integer) and the general formula (However, R ₁ and R ₂ are —H, —CH ₃ , —OCH.
_{3, -C} 2 one of a _{H 5} and _-OC 2 _{H 5} group, _{R 3}
It is _{-H, -CH 3, -C 2 H} 5, -C 3 H 7, and One of the groups, n is an integer. ) Are particularly preferable, and polythiophene, poly (3-methylthiophene), polypyrrole and poly (N-methylpyrrole) are frequently used from the practical viewpoint. As a method for producing these π-conjugated polymer films, a π-conjugated polymer obtained by an ordinary polymer synthesis method is provided by spin coating, vapor deposition, dipping, etc., or a catalyst is applied in advance. By the way, there are a method of obtaining by introducing a monomer gas, a CVD method, a photo-CVD method, a chemical oxidative polymerization method, an electrochemical polymerization method and the like, but of course the invention is not limited to these. It is also possible to use the LB method in which the monomer is spread on a subphase such as water or glycerin to form a monomolecular film or a cumulative film and deposited on the substrate. At this time, the π-conjugated polymer film can be obtained by a method of polymerizing before being deposited on the substrate or a method of polymerizing after being deposited.
However, the electrochemical polymerization method is preferably used from the viewpoints of film-forming property and ease of production.

π-conjugated polymer, even if not subjected to doping treatment
Although it has a low electric conductivity, it generally has a property as a p-type semiconductor. However, a doping process is often performed to improve the characteristics of the FET device. There are chemical methods and physical methods for this doping (industrial materials, 34, No. 4, p. 55, 1986). The former includes methods such as (i) doping from gas phase, (ii) doping from liquid phase, (iii) electrochemical doping, and (iv) photoinitiated doping, and the latter includes ion implantation method. Both can be used. However, the electrochemical doping method is preferably used from the viewpoint of operability and controllability of the doping amount. Moreover, in electrochemical doping, π−
When the conjugated polymer is obtained by the electrochemical polymerization method, it has an advantage that the doping amount can be controlled by the same device after the polymerization.

As an example, a method of forming a π-conjugated polymer film by an electrochemical polymerization method will be described. In the electrochemical polymerization method, a monomer corresponding to a π-conjugated polymer and a supporting electrolyte are dissolved in an organic solvent or water or a mixed solvent of water and an organic solvent to prepare a reaction solution. In the fabrication of the FET element of the present invention shown in FIG. 1, the metal film 8 acting as a lead wire thereof is used as a working electrode, and a polymerization reaction is caused by passing an electric current between it and a counter electrode such as platinum to act as a source lead wire. A desired π− acting as a source on the metal film 8
The conjugated polymer film 10 is deposited. After that, a reaction solution containing a monomer corresponding to a π-conjugated polymer different from the π-conjugated polymer film 10 and a supporting electrolyte is used, and this time, the metal film 9 serving as a drain lead wire is used as a working electrode.
A desired π-conjugated polymer film 11 acting as a drain is deposited on the metal film 9 by the same method as described above. Further, a π-conjugated polymer film 1 that functions as a source and a drain 1
When 0 and 11 are the same, the metal films 8 and 9 acting as the source and drain lead wires are simultaneously used as the working electrode, so that the metal film 8 and 9 become a source and a drain on one reaction. The same π-conjugated polymer films 10 and 11 can be formed.

Next, π different from the π-conjugated polymer films 10 and 11
-Π-conjugated polymer films 10 and 11 using a reaction solution containing a monomer corresponding to the conjugated polymer and a supporting electrolyte.
Of at least one of them is subjected to electrochemical polymerization, and the desired π-conjugated polymer film 4 is coated on and between the π-conjugated polymer film serving as the source 10 and the drain 11. Since the anion of the supporting electrolyte is generally doped in the π-conjugated polymer synthesized by the electrochemical polymerization method, the doping amount may be adjusted for the purpose of obtaining excellent characteristics as an FET element. Generally, F
Due to the characteristics of the ET element, the π-conjugated polymer film 4, 10, 11
At least one of them is doped, and the various doping methods described above are used depending on the structure of the device.

Any organic solvent may be used as the organic solvent in the electrochemical polymerization method as long as it can dissolve the supporting electrolyte and the above-mentioned monomer. (DM
A polar solvent such as SO), dichloromethane, tetrahydrofuran, ethyl alcohol and methyl alcohol is used alone or as a mixed solvent of two or more kinds. The supporting electrolyte has a high oxidation potential and a high reduction potential, and does not undergo oxidation or reduction reaction itself during electrolytic polymerization, and is a substance capable of imparting conductivity to a solution by being dissolved in a solvent, for example, Perchloric acid tetraalkylammonium salt, tetraalkylammonium tetrafluoroborate salt, tetraalkylammonium hexafluorophosphate salt, tetraalkylammonium paratoluenesulfonate salt, sodium hydroxide and the like are used, but of course two or more kinds may be used in combination. I do not care.

In the FET element of FIG. 1 which is an embodiment of the present invention, the location where all π-conjugated polymer films are produced by the electrochemical polymerization method has been described above. However, depending on the structure of the FET element, The FET element can be manufactured by using the electrochemical polymerization method in combination with another film forming method or by only using another film forming method. The FET element of the present invention thus obtained is useful as a driving circuit for a switching element or a large area liquid crystal display element.

〔Concrete example〕

Hereinafter, details of the present invention will be described with reference to specific examples, but of course, the present invention is not limited to these specific examples.

Concrete Example 1 An n-type silicon plate (3.0 cm × 3.0 cm) having a conductivity of 6 S / cm and a thickness of 380 μm was provided with a silicon oxide film having a thickness of about 3000 Å on both sides by a thermal oxidation method. Next, using a positive photoresist on one surface, a pattern for forming a metal film (each effective area: 0.2 cm × 0.8 c that functions as a source and drain lead wire).
m; distance between both patterns: 6 μm), and then 200 Å of chromium film is formed by vacuum evaporation method, and gold film is further formed on it.
After providing 300 Å, the resist was removed to form a gold film that acts as the source and drain lead wires. Lead wires were further taken on the both lead wires with silver-silver paste, and the contact portions were fixed with an epoxy resin to obtain an element substrate.

Nitrogen gas was bubbled through a liquid containing tetramethylammonium and p-toluenesulfonate (0.7g) as an electrolyte in 100 ml of acetonitrile for about 40 minutes to completely dissolve the electrolyte, and then 0.4 ml of pyrrole was added. Was used as the reaction solution. Both gold films acting as source and drain lead wires on the silicon plate were used as working electrodes, a platinum plate (1 cm × 2 cm) was used as a counter electrode, and SCE was used as a reference electrode.
They were immersed in the reaction solution using a (saturated calomel electrode). A constant current (60 μA) was passed between the counter electrode and the working electrode as an anode under a nitrogen gas flow for 6 minutes to deposit polypyrrole serving as a source and a drain only on the working electrode. After the synthesis, the substrate was left in an open circuit state for about 15 minutes, then the substrate coated with polypyrrole was taken out from the reaction solution, washed twice with deoxygenated acetonitrile in advance, dried by blowing nitrogen gas, and then in vacuum. Saved in.

After dissolving tetraethylammonium perchlorate (0.7 g) and 2,2'-dithiophene (0.4 g) as an electrolyte in 100 ml of acetonitrile, nitrogen gas was bubbled for about 30 minutes to prepare a reaction solution. In this solution, the polypyrrole film serving as the source and drain on the substrate coated with the polypyrrole was used as a working electrode, a platinum plate (1 cm × 2 cm) was used as a counter electrode, and SCE was used as a reference electrode. Soaked Under a nitrogen gas stream, first, 1 V was applied to the working electrode with a potentiostat to the SCE for 1 minute, and then a constant current (3
0 μA) was flowed for 5 minutes to deposit a polythiophene film serving as a semiconductor layer on the polypyrrole film serving as the source and drain which is the working electrode and on the silicon oxide between the polypyrrole films.

Next, the potential of the working electrode was set to 0 V with respect to SCE by a potentiostat for 4 hours to adjust the doping amount of the polypyrrole film and the polythiophene film. Then, it was washed twice with acetonitrile that had been deoxygenated in advance, dried by blowing nitrogen gas, and then completely dried in vacuum.

The silicon oxide on the other surface of the silicon plate not covered by the polypyrrole film and the polythiophene film, which are π-conjugated polymers provided as described above, was partially (about 0.5.
cm ² ), make an ohmic contact with n-type silicon with an indium-gallium alloy, take out a lead wire from this, fix the contact part with epoxy resin, and n-type silicon acts as a gate electrode through this lead wire I decided to do it.

As described above, the FET device of the embodiment of the present invention having the structure shown in FIG. 1 was manufactured as a prototype. In this specific example, 1 in FIG.
And 2 are n-type silicon, a substrate / gate electrode, 3 is a silicon oxide serving as an insulating film, 4 is a semiconductor layer, a polythiophene film, 10 and 11 are polypyrrole films serving as a source and a drain, 8 and 9
Is a chromium film covered with a gold film that serves as lead wires from the source and drain, respectively.

Example 2 A solution prepared by dissolving tetraethylammonium perchlorate (0.7 g) as an electrolyte in 100 ml of acetonitrile was bubbled with nitrogen gas for 30 minutes, and 0.4 ml of 3-methylthiophene was added thereto to obtain a reaction solution. Using an element substrate manufactured in the same manner as described in Example 1, using both gold films acting as lead wires of the source and drain on the silicon plate as working electrodes and using a platinum plate (1 cm × 2 cm) as a counter electrode, Using SCE as a reference electrode, immersing them in a reaction solution and then applying a constant current (60 μA) between the counter electrode and the working electrode as an anode under a nitrogen gas flow for 6 minutes to form a source and a drain only on the working electrode. Then, a poly (3-methylthiophene) film was deposited. Then, the substrate on which the poly (3-methylthiophene) film was adhered was taken out from the reaction solution,
After washing twice with deoxygenated acetonitrile in advance, it was dried by blowing nitrogen gas, and further stored in vacuum.

Tetraethylammonium perchlorate (0.7g) and 2,
Nitrogen gas was bubbled through a 100 ml acetonitrile solution in which 2'-dithiophene (0.4 g) was dissolved for 30 minutes to obtain a reaction solution. Poly (3-methylthiophene) on both gold films acting as source and drain leads on the silicon plate
The membrane is used as the working electrode and the platinum plate (1 cm x 2 cm) is used as the counter electrode.
These were immersed in the reaction solution using SCE as a reference electrode. SC with potentiostat on working electrode under nitrogen gas flow
After 0.9 V was applied to E for 1 minute, a constant current (30 μA) was applied between the counter electrode and the working electrode for 7 minutes,
A polythiophene film serving as a semiconductor layer was deposited on the poly (3-methylthiophene) film serving as the source and the drain, which is the working electrode, and on the silicon oxide between the source and the drain.

Next, the potential of the working electrode was set to 0 V with respect to SCE by a potentiostat for 4 hours to adjust the doping amount of the poly (3-methylthiophene) film and the polythiophene film. Then, it was washed twice with deoxygenated acetonitrile in advance, dried by blowing nitrogen gas, and then completely dried in vacuum.

The silicon oxide on the other side of the silicon plate not covered with the poly (3-methylthiophene) film and the polythiophene film, which are π-conjugated polymers provided as described above, was partially (about 0.5 cm ² ) Removed and made ohmic contact with n-type silicon with an indium-gallium alloy, took out the lead wire from this, fixed the contact part with epoxy resin,
Through this lead wire, n-type silicon was made to act as a gate electrode.

As described above, the FET device of the embodiment of the present invention having the structure shown in FIG. 1 was manufactured as a prototype. In this specific example, 1 in FIG.
And 2 are composed of n-type silicon, silicon oxide which serves as a substrate and gate electrode, 3 acts as an insulating film, 4 is a polythiophene film which is a semiconductor layer, and 10 and 11 are poly (3-methyl) acting as a source and a drain, respectively. The thiophene) films, 8 and 9, are chromium films coated with a gold film that serves as lead wires from the source and drain, respectively.

Comparative Example An element substrate was manufactured in the same manner as in Specific Example 1. However, in the specific example 1, the gold film serving as the source and drain lead wires is
Here, they were used as the source and the drain themselves.

Tetraethylammonium perchlorate (0.7g) and 2,
2'-Dithiophene (0.4g) in acetonitrile (100
The reaction solution was prepared by bubbling nitrogen gas for 30 minutes. Both the gold films serving as the source and drain of the element substrate are used as working electrodes, and the platinum plate (1 cm × 2 cm) is used as the counter electrode.
These were immersed in the reaction solution using SCE as a reference electrode.
A constant current (30 μA) was applied between the working electrode and the platinum plate, which was the counter electrode, for 5 minutes to coat both gold films to be the source and drain and the silicon oxide between the source and drain with the polythiophene film. Next, the potential of the working electrode was set to 0 V with respect to SCE by a potentiostat for 4 hours to adjust the doping amount of the polythiophene film. After that, 2 times with deoxygenated acetonitrile
After washing once, it was dried by blowing nitrogen gas and then completely dried in a vacuum. After that, in the same manner as in Examples 1 and 2, n-type silicon was made to act as a gate electrode.

As described above, a comparative FET device having the same structure as that shown in FIG. In this comparative example, 7 in FIG. 3 is a substrate / gate electrode made of n-type silicon.
Is a silicon oxide that functions as an insulating film, 4 is a polythiophene film that is a semiconductor layer, and 5 and 6 are chromium films covered with a gold film that functions as a source and a drain, respectively.

FIG. 4 is a characteristic diagram with respect to the gate voltage of the current flowing between the source and the drain when 30 V is applied between the source and the drain in the FET devices manufactured in the first specific example, the second specific example, and the comparative example. It is the gate voltage and the vertical axis is the source-drain current. As is apparent from FIG. 4, in the two types of elements according to the specific example of the present embodiment, the source-drain current was significantly modulated by the voltage applied from the gate, and the characteristics were remarkably improved as compared with the comparative example. . Further, the elements of Examples 1 and 2 were not deteriorated even after being left in the air for 1 month.

〔The invention's effect〕

As described above, according to the FET element of the present invention, the source is the first π-conjugated polymer film and the drain is the first π-conjugated polymer film.
It is composed of a second π-conjugated polymer film which is the same as or different from the conjugated polymer film, and the semiconductor layer which is a current path is different from the first and second π-conjugated polymer films. Third π
By using a conjugated polymer film, it is possible to obtain a device that is stable and has excellent electrical characteristics.

[Brief description of drawings]

FIG. 1 is a sectional view of an FET device according to an embodiment of the present invention, FIGS. 2 and 3 are sectional views of a conventional FET device, and FIG.
The figure shows 3 points between the source and drain of the embodiment of the present invention and the comparative example.
It is a characteristic view with respect to the gate voltage of the source-drain current when 0V is applied. In the figure, 1 is a substrate, 2 is a gate electrode, 3 is an insulating film,
4 is a π-conjugated polymer film serving as a semiconductor layer, 5 and 6 are source electrodes and drain electrodes, 7 is a substrate / gate electrode, 8 and 9 are metal films which are source and drain lead wires, 10 and Reference numeral 11 is a π-conjugated polymer film that functions as a source and a drain, respectively. The same reference numerals in the drawings indicate the same or corresponding parts.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-60-261175 (JP, A) JP-A-55-130161 (JP, A) JP-A-58-12370 (JP, A) JP-A-61- 163658 (JP, A)

Claims (15)

[Claims] 1. An insulated gate field effect transistor in which the electric conductivity of a semiconductor layer, which is a current path between a source and a drain, is controlled by a gate voltage via an insulating thin film, wherein the source is a first π-conjugated polymer. A third π different from the first and second π-conjugated polymer films in that the drain is formed of the second π-conjugated polymer film and the semiconductor layer is in the drain.
-A field effect transistor characterized by comprising a conjugated polymer film. 2. The field effect transistor according to claim 1, wherein the first π-conjugated polymer film and the second π-conjugated polymer film are different from each other. 3. The field effect transistor according to claim 1, wherein the first π-conjugated polymer film is the same as the second π-conjugated polymer film. 4. The π-conjugated polymer having at least one heterocyclic five-membered ring in at least one of the first, second and third π-conjugated polymer films. The field effect transistor according to any one of items 1 to 3. 5. A first, second, and third π having a five-membered heterocyclic ring.
-The conjugated polymer has the general formula (However, X is one of S and O atoms, R ₁ and R ₂ are one of —H, —CH ₃ , —OCH ₃ , —C ₂ H ₅ , and —OC ₂ H ₅ groups, n Is an integer.) The fourth aspect of the present invention is characterized in that
Field-effect transistor according to the item. 6. A first, second, and third π having a heterocyclic five-membered ring.
-The conjugated polymer has the general formula (However, R ₁ and R ₂ are —H, —CH ₃ , —OCH.
_{3, -C} 2 one of a _{H 5} and _-OC 2 _{H 5} group, _{R 3}
One _{H, -CH 3, -C 2 H} 5, -C 3 H 7 , the and , N is an integer. ) The field effect transistor according to claim 4, characterized in that 7. A first, second, and third π having a five-membered heterocyclic ring.
The field effect transistor according to claim 5, wherein the conjugated polymer is polythiophene or poly (3-methylthiophene). 8. A first, second, and third π having a five-membered heterocyclic ring.
-The conjugated polymer is polypyrrole or poly (N-methylpyrrole).
Field-effect transistor according to the item. 9. The first and second π-conjugated polymer films are polypyrrole, and the third π-conjugated polymer film is polythiophene. The field effect transistor described. 10. The first and second π-conjugated polymer films are poly (3-methylthiophene), and the third π-conjugated polymer film is polythiophene. A field effect transistor according to the fourth item. 11. The first, second and third π-conjugated polymer films, at least one of which is obtained by an electrochemical polymerization method. 11. A field effect transistor according to any one of items 10 to 10. 12. The first, second, and third π-conjugated polymer films, at least one of which is doped, and claims 1 to 1.
The field effect transistor according to any one of item 1. 13. The field-effect transistor according to claim 12, wherein the at least one π-conjugated polymer film is electrochemically doped. 14. The polythiophene is obtained by an electrochemical polymerization method of 2,2′-dithiophene, as claimed in claim 7, or 9 to 10.
A field effect transistor according to any one of items. 15. A field effect transistor according to claim 1, wherein the gate electrode is composed of one of p-type silicon and n-type silicon. .