Classifications

• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
  • H10K10/00—Organic devices specially adapted for rectifying, amplifying, oscillating or switching; Organic capacitors or resistors having potential barriers
  • H10K10/40—Organic transistors
  • H10K10/46—Field-effect transistors, e.g. organic thin-film transistors [OTFT]
  • H10K10/462—Insulated gate field-effect transistors [IGFETs]
  • H10K10/468—Insulated gate field-effect transistors [IGFETs] characterised by the gate dielectrics
• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
  • H10K71/00—Manufacture or treatment specially adapted for the organic devices covered by this subclass
  • H10K71/10—Deposition of organic active material
  • H10K71/16—Deposition of organic active material using physical vapour deposition [PVD], e.g. vacuum deposition or sputtering
  • H10K71/164—Deposition of organic active material using physical vapour deposition [PVD], e.g. vacuum deposition or sputtering using vacuum deposition
• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
  • H10K85/00—Organic materials used in the body or electrodes of devices covered by this subclass
  • H10K85/30—Coordination compounds

Definitions

• the present invention relates to a field effect transistor, and a method of producing the same, which employs monobenzoporphyrin in its active layer.
• H05-55568 such as pentacene and tetracene
• the low-molecular-weight compounds disclosed in Japanese Patent Application Laid-Open No H05-190877 such as phthalocyanines including lead phthalocyanine, perylene and tetracarboxylic acid derivatives thereof
• Many of these compounds are also disclosed in Advanced Materials, Vol.
• the present invention provides a field effect transistor comprising an organic semiconductor layer comprising a compound having a monobenzoporphyrin skeleton represented by the general formula (1) :
• Ri and R 2 are independently selected from the group consisting of a hydrogen atom, a halogen atom, a hydroxyl group, and alkyl, alkenyl, oxyalkyl, thioalkyl, alkyl ester and aryl groups each having 1 to 12 carbon atoms with the proviso that adjacent Ri may be the same or different and adjacent R 2 may be the same or different and that at least two of R 2 are not hydrogen atoms;
• R 3 is a hydrogen atom or an aryl group; and M denotes two hydrogen atoms, a metal atom or a metal oxide.
• the present invention also provides a field effect transistor comprising an organic semiconductor layer comprising a compound having a monobenzoporphyrin skeleton, wherein the organic semiconductor layer has at least one peak at Bragg angle (2 ⁇ ) 7.8° ⁇ 0.2° in terms of Cu K-alpha X-ray diffraction.
• the present invention further provides a field effect transistor characterized in that R x and R 3 of the monobenzoporphyrin compound represented by the general formula (1) are hydrogen atoms and at least two of R2 are alkyl groups having 1 to 12 carbon atoms .
• the present invention also provides a field effect transistor characterized in that M of the monobenzoporphyrin compound represented by the general formula (1) is two hydrogen atoms or one copper atom.
• the present invention further provides a method of producing a field effect transistor, which comprises the step of heating a monobicycloporphyrin compound represented by the general formula (2) :
• Ri, R 2 and R 4 are independently selected from the group consisting of a hydrogen atom, a halogen atom, a hydroxyl group, and alkyl, alkenyl, oxyalkyl, thioalkyl, alkyl ester, and aryl groups each having 1 to 12 carbon atoms with the proviso that adjacent Ri may be the same or different and adjacent R 2 may be the same or different and that at least two of R 2 are not hydrogen atoms;
• R 3 is a hydrogen atom or an aryl group; and M denotes two hydrogen atoms, a metal atom or a metal oxide, to effect conversion to a monobenzoporphyrin compound represented by the general formula (1):
• the present invention also provides a method of producing a field effect transistor characterized in that the monobicycloporphyrin compound represented by the general formula (2) is heated at a temperature between 130°C to 250°C to be converted to the monobenzoporphyrin compound represented by the general formula (1) .
• an organic semiconductor layer having high crystallinity and orientation can stably be formed at a broad range of calcination temperature including a low temperature, not only heat-resistant substrates such as a glass substrate, but also various kinds of plastic substrates can be employed. Further, this makes it possible to provide a field effect transistor that can be produced easily and shows a high field-effect mobility, and a method of producing the field effect transistor.
• FIG. 1 is an expanded cross-sectional view schematically illustrating a part of a top electrode type field effect transistor in accrdance with the present invention
• FIG. 2 is an expanded cross-sectional view schematically illustrating a part of a bottom electrode type field effect transistor in accrdance with the present invention
• FIG. 3 illustrates the configuration of Example 1 in accordance with the present invention, and is an expanded cross-sectional view schematically illustrating a part of a top electrode type field effect transistor
• FIG. 4 is a diagram illustrating the electrical characteristics of the field effect transistor of Example 1 of the present invention
• FIG. 5 is an X-ray diffraction pattern obtained in Example 1 of the present invention
• FIG. 6 illustrates the results of differential thermal analysis obtained in Example 1 of the present invention
• FIG. 7 illustrates the results of the ultraviolet-visible light absorption spectrum obtained in Example 1
• FIG. 8 illustrates the results of differential thermal analysis obtained in Example 5
• FIG. 9 is an X-ray diffraction pattern obtained in Example 5 of the present invention.
• the field effect transistor (FET) in accordance with one embodiment of the present invention is a device having at least an organic semiconductor, an insulator and a conductor.
• the insulator is an insulating film (layer) for covering the conductor, which serves as an electrode.
• the organic semiconductor is an organic semiconductor layer which responds to stimulus (electric field) generated by the conductor (electrode) .
• the organic semiconductor layer is a layer the electrical characteristics of which vary depending on an electric field, and more specifically is a layer in whcih the electrical conductivity, or in other words a current flowing throguh the organic semiconductor layer, varies in response a change in the electric field.
• the FET in accordance with the present invention may also have a source electrode and a drain electrode.
• the above- mentioned conductor can be used as a gate electrode.
• the above-mentioned insulating layer can be used as a gate insulating layer for covering the gate electrode to insulate the gate electrode from the organic semiconductor layer, source electrode and drain electrode.
• FIG. 1 is a schematic cross-sectional view illustrating a top electrode type organic semiconductor -device in accordance with the present embodiment.
• Reference numeral 1 denotes a substrate
• 2 denotes a gate electrode
• 3 denotes a gate inssulating layer
• 4 denotes a source electrode
• 5 denotes a drain electrode
• 6 denotes an organic semiconductor layer.
• the gate electrode 2 is provided on the surface of the substrate 1 and the gate insulating layer 3 is provided thereon; and the source electrode 4 and the drain electrode 5 are arranged above the surface of the insulating layer 3 with a gap therebetween.
• the organic semiconductor layer 6 is provided on the source electrode 4 and the drain electrode 5 and on the insulating layer 3, which serves as a separating region therefor, so as to be in contact with the electrodes 4 and 5.
• the insulating layer 3 is provided so as to cover the gate electrode 2.
• FIG. 2 is a schematic cross-sectional view illustrating a bottom electrode type organic semiconductor device in accordance with the present embodiment.
• Reference numeral 1 denotes a substrate
• 2 denotes a gate electrode
• 3 denotes a gate inssulating layer
• 4 denotes a source electrode
• 5 denotes a drain electrode
• 6 denotes an organic semiconductor layer.
• the gate electrode 2 is provided on the surface of the substrate 1 and the gate insulating layer 3 is provided thereon; and the source electrode 4 and the drain electrode 5 are arranged above the surface of the insulating layer 3 with a gap therebetween.
• the organic semiconductor layer 6 is provided on the source electrode 4 and the drain electrode 5 and on the insulating layer 3, whichserves as a separating region therefor, so as to be in contact with the electrodes 4 and 5.
• the insulating layer 3 is provided so as to cover the gate electrode 2.
• the material of the organic semiconductor layer 6 is required to show a high mobility. Accordingly, as a result of • continued investigation to find an organic semiconductor material that can stably form an organic semiconductor layer having high crystallinity and orientation at a broad range of calcination temperature, the present inventors have discovered that a compound having the specific monobenzoporphyrin skeleton represented by the general formula (1):
• the present inventors have made the findings that a simple field effect transistor showing a high field-effect mobility can be attained by employing as the organic semiconductor layer 6 a compound having the monobenzoporphyrin skeleton represented by the general formula (1) .
• Ri and R 2 are independently selected from the group consisting of a hydrogen atom, a halogen atom, a hydroxyl group, and alkyl, alkenyl, oxyalkyl, thioalkyl, alkyl ester and aryl groups each having 1 to 12 carbon atoms with the proviso that adjacent Ri may be the same or different and adjacent R 2 may be the same or different and that at least two of R 2 are not hydrogen atoms; R 3 is a hydrogen atom or an aryl group; and M denotes two hydrogen atoms, a metal atom or a metal oxide.
• R 2 are alkyl groups. This increases the orientation of the porphyrins, which improves the mobility.
• a method of vapor-depositing monobenzoporphyrin a method of carrying out vapor- deposition while converting a precursor to monobenzoporphyrin, and a method of applying a precursor and then effecting heating
• the method of applying a precursor then effecting heating is preferred. Next, the precursor will be described.
• R 4 may independently be selected from the group consisting of a hydrogen atom, a halogen atom, a hydroxyl group, and alkyl, alkenyl, oxyalkyl, thioalkyl, alkyl ester, and aryl groups each having 1 to 12 carbon atoms, or may be a combination of two or more thereof. If the number of carbon atoms exceeds 12, the molecular weight of a eliminated component increases to leave the eliminated component in a benzoporphyrin compound film, so that sufficient semiconductor characteristics are not obtained. It is most preferable that R 4 is a hydrogen atom.
• General Formula (2) is a hydrogen atom.
• the substituent R x of the porphyrin compound remains as a substituent in the monobenzoporphyrin compound obtained after the heat treatment. Therefore, the substituent Ri affects the orientation of the monobenzoporphyrin.
• Ri may ⁇ independently be selected from the group consisting of a hydrogen atom, a halogen atom, a hydroxyl group, and alkyl, alkenyl, oxyalkyl, thioalkyl, alkyl ester and aryl groups each having 1 to 12 carbon atoms, or may be a combination of two or more thereof.
• Ri is a hydrogen atom, whereby the stacking of porphyrin rings occurs more easily, which enhances the crystallinity of a film.
• the substituent R 2 of the porphyrin compound influences the solubility and crystallinity.
• R 2 may independently be selected from the group consisting of a hydrogen atom, a halogen atom, a hydroxyl group, and alkyl, alkenyl, oxyalkyl, thioalkyl, alkyl ester, and aryl groups each having 1 to 12 carbon atoms, or may be a combination of two or more thereof. If the number of carbon atoms of R 2 exceeds 12, the existence ratio of the porphyrin ring to the whole molecule decreases, which makes difficult the orientation of the porphyrin rings, so that sufficient semiconductor characteristics are not obtained. However, in general, the porphyrins have extremely poor solubility to common solvents due to the problem of stacking caused by the large planeness thereof.
• R 2 are substituents having from 2 to 12 carbon atoms. It is more preferable that 2 or more of R 2 are alkyl groups having 2 to 12 carbon atoms .
• the M of the porphyrin compound is not particularly limited, provided that M is two hydrogens, or a metal or metal oxide. Examples of the metal include copper, gold, silver, zinc, nickel, chromium, magnesium, lithium, and the like. Examples of the metal oxide include TiO, VO and the like. Most preferably, M is two hydrogen atoms or one copper atom.
• Preferable examples of the method of forming the organic semiconductor layer include a method in which a monobicycloporphyrin compound represented by the general formula (2) is dissolved in an organic solvent, coated on a substrate and then heated to obtain a crystallized film of a monobenzoporphyrin compound represented by the general formula (1) .
• the organic solvent to be used for dissolving the monobicycloporphyrin compound is not particularly limited, provided that it does not react with the porphyrin compound nor precipitate the compound. Further, two or more solvents may be used as a mixture.
• solvents that include halogenated- organic solvents such as chloroform, methylene chloride, dichloroethane, chlorobenzene, 1, 2-dichloroethylene, etc. and aromatic solvents such as xylene, toluene, etc.
• concentration of the solution may be arbitrarily adjusted depending on the desired film thickness, it is preferably from 0.01 to 5% by weight
• the coating method include a spin casting method, a dipping method, a dropping method, a printing method such as an offset or screen printing or an ink jet method.
• a coating film of the monobicycloporphyrin may also be preliminarily dried at a temperature of 100°C or lower.
• the preferable heating temperature for obtaining a higher field-effect mobility is from 130 to 250°C.
• a crystallized film with sufficient crystal growth cannot be obtained at a temperature of lower than 130°, while cracks will be generated due to an abrupt shrinkage of the film when the temperature exceeds 250°C.
• Means for the heating include, but are not limited to, a hot plate, a hot air-circulating oven or a vacuum oven.
• a coating film of the bicyclo compound solution on an insulating layer in order to improve the uniformity of a coating film of the bicyclo compound solution on an insulating layer, and to make the benzo compound film have a uniform orientation by heating, it is also possible to modify only the insulating film surface.
• Examples of such a method include a dry treatment using ozone, plasma or a hexamethyldisilane gas and a wet treatment using a solution prepared by dissolving tetraalkoxysilane, trichlorosilane, a surfactant and the like in an organic solvent.
• a rubbing treatment in which the film is lightly rubbed with a cloth or the like.
• the cloth for use in the rubbing treatment includes, but is not limited to, rayon, cotton, silk, or the like. It is preferable that the film thickness of the organic semiconductor layer using the oriented film of the benzoporphyrin compound obtained by this procedure is within the range of 30 to 150 n . When the film thickness is less than 30 nm, the uniformity of the film thickness will be impaired. On the other hand, when- exceeding 150 nm, the mobility will be lowered due to the impairment of the smoothness of the film surface. The growth of the crystal can be confirmed by X-ray diffraction, film surface observation using an optical microscopy, a laser microscopy, a scanning electron microscopy or the like and ultraviolet- visible light absorption spectra of the film.
• the maximum diameter of crystal grains in the organic semiconductor layer is 1 ⁇ m or more. If it is less than 1 ⁇ m, sufficient field- effect mobility cannot be obtained. Further, it is preferable that an intense peak is characteristically observed at Bragg angle (2 ⁇ ) 7.8° + 0.2° in terms of
• the X-ray diffraction measurement in the present invention is carried out using Cu K-alpha ray under the following conditions.
• Measuring apparatus RAD-RX wide angle X-ray diffraction apparatus manufactured by Rigakudenki
• Tube current 150 mA Scan method: 2 ⁇ / ⁇ scan
• the shape of the X- ray diffraction peak may slightly differ depending on the conditions during production. In some cases the peak tip may be split.
• a substrate worked into a plate shape or sheet shape may be employed which consists of an inorganic material such as Si, glass, metal and the like, or a resin material such as polyethylene terephthalate (PET) , polyethylene naphthalate (PEN), polyimide (PI), polyetherimide (PEI), polyethersulfone (PES) , polysulfone (PSF) , polyphenylenesulfide (PPS) , polyetheretherketone (PEEK), polyarylate (PAR), polyamideimide (PAI) and the like.
• PET polyethylene terephthalate
• PEN polyethylene naphthalate
• PI polyimide
• PEI polyetherimide
• PES polyethersulfone
• PSF polysulfone
• PES polyphenylenesulfide
• PEEK poly
• a resin material is preferably employed.
• Materials for the gate electrode 2, source electrode 4 and drain electrode 5 are not particularly limited, provided that they are electrically conductive materials, and include platinum, gold, silver, nickel, chromium, copper, iron, tin, antimony, lead, tantalum, indium, aluminum, zinc, magnesium and alloys thereof; conductive metal oxides such as indium-tin oxide; and inorganic and organic semiconductors whose conductivity is increased by doping or the like, for example, monocrystalline silicon, polycrystalline silicon, amorphous silicon, germanium, graphite, polyacetylene, polyparaphenylene, polythiophene, polypyrrole, polyaniline, polythienylenevinylene, polyparaphenylenevinylene, and the like.
• Electrodes include sputtering, vapor deposition, a printing method using a solution or paste or an ink-jet method. Further, preferable electrode materials of the above-mentioned are those having a low electrical resistance at a contact surface with the semiconductor layer.
• the insulating film 3 any material may be used, provided that a solution of the compound represented by the general formula (2) can be uniformly coated thereon, but those having a high dielectric constant and a low conductivity are preferred.
• Examples of such material include inorganic oxides and nitrides such as silicon oxide, silicon nitride, aluminum oxide, titanium oxide and tantalum oxide; and organic polymers such as polyacrylates, polymethacrylates, polyethylene terephthalate, polyimides, polyethers and siloxane- containing polymers.
• inorganic oxides and nitrides such as silicon oxide, silicon nitride, aluminum oxide, titanium oxide and tantalum oxide
• organic polymers such as polyacrylates, polymethacrylates, polyethylene terephthalate, polyimides, polyethers and siloxane- containing polymers.
• those having high surface smoothness are preferred.
• Examples of such a method include a dry treatment using ozone, plasma or a hexamethyldisilane gas and a wet treatment using a solution prepared by dissolving tetraalkoxysilane, octadecyltrichlorosilane, trichlorosilane, a surfactant and the like in an organic solvent.
• the structure of the field effect transistor in accordance with the present invention is not limited to a thin film type but may be a beam-channel type. [Examples]
• the present invention will be described with reference to synthesis examples and examples. However, the present invention is not limited to these examples.
• Step 4 A reaction vessel was charged with benzyl acetoacetate (97 ml, 560 mmol) and acetic acid (81 ml), and an aqueous solution of sodium nitrite (37.8 g) and water (115 ml) was added dropwise at 10°C or lower. After dropping, stirring was performed for 3 hours at room temperature. A mixture of zinc powder (36.6 g) , sodium acetate (25.9 g) and the above- described solution were added at lower than 60°C into a separate vessel with a solution of the 3-n-butyl- 2, 4-pentanedione (43.16 g, 280 mmol) in acetic acid (45 ml) obtained in Step 3.
• Step 7 A reaction vessel was charged with 4-hydroxy-3- nitrohexane (14.7 g, 100 mmol), acetic anhydride (14.8 ml, 157.3 mmol), chloroform (50 ml) and a few drops of concentrated sulfuric acid, then stirred for 10 hours at room temperature. After the reaction was finished, chloroform (50 ml) was added, and the resulting solution was washed with water, 5% aqueous sodium bicarbonate solution and saturated saline.
• Step 9 A light-resistant reaction vessel equipped with a reflux condenser was charged with the ethyl-4,7- dihydro-4, 7-ethano-2H-isoindole-l-carboxylate (1.95 g, 9.6 mmol) obtained in Step 2, 100 ml of ethylene glycol and 2.0 g of potassium hydroxide.
• the vessel was then purged with nitrogen, and the mixture was stirred for 2 hours at 175°C.
• the reaction mixture was then cooled to room temperature, and poured into ice water.
• the resulting solution was extracted with chloroform, the extract was washed with saturated saline and the obtained organic layer was dried over anhydrous sodium sulfate. Concentration of the solution under reduced pressure then gave 4,7- dihydro-4,7-etano-2H-isoindole (0.98 g, yield 70.4%).
• Step 10 A light-resistant reaction vessel equipped with a reflux condenser was charged with the ethyl 3, - diethylpyrolle-2-carboxylate (2.056 g, 10.53 mmol) obtained in Step 8, ethylene glycol (100 ml) and potassium hydroxide (3.5 g) , purged with nitrogen, and stirred for 2.5 hours at 160°C. The reaction vessel was then cooled to room temperature, and poured into ice water. The resulting product was extracted with ethyl acetate, the extract was washed with aqueous sodium bicarbonate solution, water and saturated saline and the obtained organic layer was dried over anhydrous sodium sulfate and concentrated under reduced pressure.
• the light-resistant reaction vessel equipped with a reflux condenser was further charged with the 3, 4-diethylpyrrole obtained in the present step, benzyl-5-acetoxymethyl-4-n-butyl-3- methylpyrrole-2-carboxylate (7.21 g, 21 mmol) obtained in Step 5, acetic acid (10 ml) and ethanol (150 ml), and refluxed for 18 hours. After refluxing, the reaction vessel was cooled to room temperature, charged with ethanol (50 ml) and left for 5 hours at 0°C.
• Step 11> A three-neck flask was charged with 0.5 g of palladium carbon (Pd/C) and 20 ml of dry THF, purged with hydrogen, stirred for 30 minutes and a solution of 2, 5-bis (5-benzylcarbonyl-3-n-butyl-4-methyl-2- pyrroylmethyl) -3, 4-dimethyl-lH-pyrrole (2.09 g, 3.03 mmol) dissolved in dry THF (30 ml) was slowly added dropwise into the flask. This solution was stirred as such overnight at room temperature. After stirring, the solution was subjected to celite filtration. The filtrate was concentrated under reduced pressure, shielded from light, purged with nitrogen, then cooled using an ice bath.
• FIG. 3 shows the structure of a top electrode type field effect transistor in accordance with the present example.
• a highly-doped N-type silicon substrate was prepared as the gate electrode 2.
• a silicon oxide film with a thickness of 5,000 A obtained by thermally oxidizing the surface layer of the silicon substrate was used as the gate insulating layer 3.
• a 1% by weight solution of the monobicycloporphyrin copper complex synthesized in Synthesis Example 1 in chloroform (the monobicycloporphyrin copper complex was completely dissolved in the chloroform) was spin- cast on the substrate to form a coating.
• the substrate was heated to 220° to form an organic semiconductor layer 6 composed of the monobenzoporphyrin copper complex.
• the organic semiconductor layer had a film thickness of 120 nm.
• Gold was vapor-deposited thereon using a mask to form the source electrode 4 and drain electrode 5.
• the electrode preparation conditions were as follows .
• the degree of vacuum in the vapor-deposition apparatus chamber was 1.33 x 10 ⁇ 4 Pa (1 x 10 ⁇ 6 Torr)
• the substrate temperature was room temperature and the film thickness was 100 nm.
• a field effect transistor with a channel length of 50 ⁇ m and a channel width of 3 mm was prepared according to the above procedure.
• Vd-Id and Vg- Id curves of the prepared transistor were measured using a Parameter Analyzer 4156C (trade name) manufactured by Agilent Technologies.
• the mobility ⁇ (cm 2 /Vs) was calculated according to the following equation (1) .
• Id ⁇ (CiW/2L) (Vg-Vth) 2 (Equation 1) wherein Ci denotes electrostatic capacity (F/cm 2 ) per unit area of the gate insulating film; W and L respectively denote a channel width (mm) and a channel length ( ⁇ m) shown in the example; and Id, Vg and Vth respectively denote a drain current (A) , a gate voltage (V) and a threshold voltage (V) .
• a Vd-Id curve as shown in FIG. 4 was obtained from the measurement.
• the obtained results showed that the transistor had a field-effect mobility of 1.3 x 10 ⁇ 3 cm 2 /V-s and an ON/OFF ratio of 1.0 x 10 3 to 6.1 x 10 6 .
• Cu K-alpha X-ray diffraction of the transistor substrate prepared under the above mentioned conditions showed an extremely strong peak at Bragg angle (2 ⁇ ) 7.8° ⁇ 0.2°. The results are shown in FIG. 5.
• Example 2 A field effect transistor was prepared by following the same procedure as in Example 1 with the exception that the heating temperature 220°C used in Example 1 was changed to 180°C. It was confirmed that the conversion to the benzo compound was completed in
• Example 3 A field effect transistor was prepared by following the same procedure as in Example 1 with the exception that the heating temperature 220°C used in Example 1 was changed to 160°C. It was confirmed that the conversion to the benzo compound was completed in
• Example 4 A field effect transistor was prepared by following the same procedure as in Example 1 with the exception that the organic semiconductor layer was formed according to the following procedure. The monobicycloporphyrin copper complex was converted to a monobenzoporphyrin copper complex by heating to
• the vacuum deposition conditions were such that the substrate was fixed on an upper part of a vapor-deposition boat, the substrate temperature was set at 220°C and the degree of vacuum was lowered to 1.33 x 10 ⁇ 4 Pa (1.0 x 10 ⁇ 6 Torr) . Then, vacuum deposition was performed to a thickness of 100 n at a rate of 0.05 to 0.15 nm per minute .
• a field effect transistor with a channel length of 50 ⁇ m and a channel width of 3 mm was prepared according to the above procedure.
• the transistor had a field-effect mobility of 1.0 x 10 ⁇ 3 cm 2 /V-s and an ON/OFF ratio of 1.0 x 10 3 to 1.5 x 10 5 .
• Example 5 A field effect transistor was prepared by following the same procedure as in Example 1 with the exception that the metal-free monobicycloporphyrin synthesized in Synthesis Example 1 was used in place of the monobicycloporphyrin copper complex used in Example 1. The transistor had a field-effect mobility of 8.0 x 10 "4 cm 2 /V-s and an ON/OFF ratio of 1.0 x 10 2 to 1.0 x 10 3 .

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