JP2005268450A - Organic semiconductor thin film, its manufacturing method, and organic semiconductor element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an organic semiconductor thin film that reveals high mobility, and to provide a method of manufacturing the thin film and an organic semiconductor element having excellent electronic characteristics. <P>SOLUTION: A laminate composed of 2,3,9,10-tetramethylpentacene powder is formed by spreading a dispersion prepared by dispersing the 2,3,9,10-tetramethylpentacene powder in chloroform on a silicon substrate and evaporating the chloroform. Then a thin film is formed by melting the 2,3,9,10-tetramethylpentacene powder on the surface of the silicon substrate, by heating the silicon substrate to a temperature higher than the melting point of the 2,3,9,10-tetramethylpentacene. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an organic semiconductor thin film, a manufacturing method thereof, and an organic semiconductor element.

Devices using organic semiconductors have milder film formation conditions than conventional inorganic semiconductor devices, and it is possible to form semiconductor thin films on various substrates or to form films at room temperature. Costs and flexibility by forming a thin film on a polymer film or the like are expected.
Organic semiconductor materials include polymer materials such as polythiophene, polythienylene vinylene, and polypyrrole, and low molecular weight materials such as polyacene compounds (tetracene, pentacene, etc.) and thiophene oligomers. Field effect transistors, solar cells, lasers (See Non-patent Document 1). In particular, when the above-described organic semiconductor is used as a field effect transistor, a polyacene compound such as pentacene is the most promising material.

An important factor related to the performance of a field effect transistor is carrier mobility, and it is known that carrier mobility is greatly influenced by a thin film structure. Further, the thin film structure greatly depends on the method of manufacturing the thin film. In general, vapor deposition, coating, and precursor heating are typical methods for producing organic semiconductor thin films, but methods such as coating are more convenient and less expensive, and printing. This method is suitable for industrial production because it can be applied to manufacturing methods suitable for mass production and mass production, such as the method and inkjet method.
Jimitrakopouras et al., "Journal of Applied Physics", 1996, Vol. 80, p. 2501 Brown et al., “Synthetic Metals”, 1997, Vol. 88, p. 37

However, since a polyacene compound-based organic semiconductor such as pentacene is hardly soluble in a solvent as it is, film formation has been performed exclusively by an evaporation method.
As a method of forming a polyacene compound thin film by a method other than vapor deposition, a solution of a pentacene ring-crosslinked precursor of a polyacene compound is applied onto a substrate, and the precursor is converted to pentacene by heat treatment. Has been reported (see Non-Patent Document 2). However, the mobility of the thin film obtained by this method has a problem that it is lower than the mobility of the thin film obtained by the vapor deposition method.

On the other hand, polymer-based organic semiconductors can be formed by a coating method because of their high solubility, but the thin film structure is lower in crystallinity than the thin film obtained by the vapor deposition method, and the mobility is such as polyacene compounds. It was known to be inferior to low molecular organic semiconductors. Therefore, in order to further improve the mobility, a thin film having higher crystallinity has been demanded.
Therefore, an object of the present invention is to solve the problems of the conventional techniques as described above, and to provide an organic semiconductor thin film that exhibits high mobility and a method for manufacturing the same. Another object is to provide an organic semiconductor element having excellent electronic characteristics.

In order to solve the above problems, the present invention has the following configuration. That is, the method for producing an organic semiconductor thin film according to claim 1 of the present invention is a method for producing an organic semiconductor thin film comprising a condensed polycyclic aromatic compound having a polycyclic structure in which 2 or more and 15 or less benzene rings are condensed. A dispersion in which the condensed polycyclic aromatic compound is dispersed in a dispersion medium is disposed on a base and heated to a temperature equal to or higher than the melting point of the condensed polycyclic aromatic compound to vaporize the dispersion medium. The condensed polycyclic aromatic compound is melted.
Moreover, the manufacturing method of the organic-semiconductor thin film of Claim 2 which concerns on this invention is a manufacturing method of the organic-semiconductor thin film of Claim 1, The said condensed polycyclic aromatic compound is represented by following Chemical formula (I). It has the following structure.

（Ｉ）

(I)

However, at least a part of the functional groups R ₁ , R ₂ , R ₃ and R _{4 in} the chemical formula (I) is a hydrocarbon group such as an alkyl group, an alkenyl group or an alkynyl group, an alkoxyl group, an ether group or a halogen group. , A formyl group, an acyl group, an ester group, a mercapto group, a thioalkyl group, a sulfide group, a disulfide group, a sulfonyl group, or a functional group containing two or more of them, and the other part is a hydrogen atom. In addition, at least one of the functional groups X and Y in the chemical formula (I) is a hydrogen atom or a halogen group, and n is an integer of 2 or more and 7 or less.
Furthermore, the organic semiconductor thin film of Claim 3 which concerns on this invention is manufactured by the manufacturing method of the organic semiconductor thin film of Claim 1 or Claim 2.
Furthermore, an organic semiconductor element according to a fourth aspect of the present invention is characterized in that at least a part of the organic semiconductor thin film according to the third aspect is formed.

  According to the method for producing an organic semiconductor thin film of the present invention, a thin film of a condensed polycyclic aromatic compound having low solubility in a general solvent can be formed at a relatively low temperature by a wet process. The organic semiconductor thin film of the present invention has high mobility. Furthermore, the organic semiconductor element of the present invention has excellent electronic properties.

  The organic semiconductor thin film of the present invention is a thin film made of a condensed polycyclic aromatic compound having a polycyclic structure in which 2 or more and 15 or less benzene rings are condensed, and is manufactured by the following wet process. That is, a dispersion in which a condensed polycyclic aromatic compound is dispersed in a dispersion medium is placed on a base, and heated to a temperature equal to or higher than the melting point of the condensed polycyclic aromatic compound to vaporize the dispersion medium and to form the condensed polycyclic aromatic. It is produced by melting a group compound and solidifying by cooling.

  Below, the manufacturing method of a condensed polycyclic aromatic compound and its thin film is demonstrated in detail. In the present invention, it is necessary to use a condensed polycyclic aromatic compound having a property of melting without sublimation. Conventionally used polyacene compounds (tetracene, pentacene, etc.), which are low molecular organic semiconductor materials, generally have sublimation properties that change directly from the solid phase to the gas phase without passing through the liquid phase. The sublimation temperature is in the temperature range of 200 to 450 ° C. Polyacene compounds have extremely low solubility in common solvents, and it has been difficult to produce a thin film by a wet process. For example, vacuum deposition, molecular beam epitaxy (MBE) is utilized by utilizing the above-described sublimation properties. Thin films were manufactured by dry processes such as sputtering, sputtering, laser deposition, and vapor transport growth. However, in such a dry process, a high temperature is required for film formation and the operation is complicated.

  Therefore, if a condensed polycyclic aromatic compound having a property of melting without sublimation is used, the dispersion is heated to a temperature equal to or higher than the melting point of the condensed polycyclic aromatic compound as described above, and the condensed polycyclic aromatic compound is heated. By melting, a condensed polycyclic aromatic compound thin film can be easily formed. Such a method can produce a thin film at a low temperature and with a simple operation as compared with a conventional dry process such as a vapor deposition method.

  Examples of the condensed polycyclic aromatic compound having the above-described properties include, for example, tetracene, pentacene, obalene, dibenzocoronene, dicolonylene, hexabenzocoronene (among these, pentacene, ovalene, dicolonylene are more preferred, and pentacene is particularly preferred). And a compound having a molecular structure in which a part of hydrogen atoms bonded to the benzene ring is substituted with a functional group. That is, it is a condensed polycyclic aromatic compound having a structure represented by the aforementioned chemical formula (I).

  The condensed polycyclic aromatic compound into which the functional group has been introduced melts without showing sublimation properties (there is a melting point). That is, when a functional group is introduced into an unsubstituted condensed polycyclic aromatic compound, sublimation is suppressed (the sublimation temperature is increased), and further in a temperature range lower than the sublimation temperature of the unsubstituted condensed polycyclic aromatic compound. Have a melting point. Then, a thin film of a condensed polycyclic aromatic compound into which a functional group having a chemical structure similar to that of an unsubstituted condensed polycyclic aromatic compound is introduced, and a thin film of an unsubstituted condensed polycyclic aromatic compound are produced by a dry process. Compared with the case where it does, it becomes possible to manufacture more easily at low temperature.

Preferred functional groups (functional groups R ₁ , R ₂ , R ₃ , R ₄ in chemical formula (I)) include hydrocarbon groups such as alkyl groups, alkenyl groups, alkynyl groups, alkoxyl groups, ether groups, halogen groups, formyl Groups, acyl groups, ester groups, mercapto groups, thioalkyl groups, sulfide groups, disulfide groups, and sulfonyl groups. Among these, alkyl groups, alkenyl groups, alkynyl groups, halogen groups, and thioalkyl groups are particularly preferable.

  The reason why the number of benzene rings contained in the condensed polycyclic aromatic compound needs to be 2 or more and 15 or less is as follows. In order to achieve good conductivity or mobility in an organic semiconductor element, in the case of a p-type transistor in which the carrier responsible for electrical conduction is a hole, for each molecule, π in the highest occupied molecular orbital (HOMO) It is desirable that the electron orbit extends over the entire molecule. Generally, the above-mentioned tendency becomes stronger as the number of benzene rings in the molecular structure increases. This makes it easier for carriers to move through the entire organic semiconductor thin film.

  Also, in the case of an n-type transistor in which the carrier responsible for electrical conduction is an electron, it is desirable that the π-electron orbit in the lowest vacant orbit (LUMO) of the molecule spreads throughout the molecule based on the same principle as that of the p-type transistor. In the present invention, the electronic physical properties of the molecule vary greatly depending on how a plurality of benzene rings are connected to form a condensed polycyclic aromatic compound, but in general, the larger the number of benzene rings, There exists a preferable tendency and 5 or more and 15 or less are especially preferable.

  Next, the dispersion medium used when manufacturing the thin film of a condensed polycyclic aromatic compound is demonstrated. The dispersion medium used in the present invention needs to be vaporized at a temperature equal to or higher than the melting point of the condensed polycyclic aromatic compound. For example, water, alcohols, esters, ethers, carbonates, amides, aliphatic compounds, aromatic compounds, and the like are preferable. Among these, trichlorobenzene and dichlorobenzene, which have good dispersibility of condensed polycyclic aromatic compounds, are preferable. , Chloroform and the like are particularly preferable. In addition, you may use these dispersion media in mixture of 2 or more types. Moreover, you may add additives, such as surfactant and a stabilizer, to a dispersion medium.

  A dispersion in which the above-mentioned condensed polycyclic aromatic compound is dispersed in such a dispersion medium is placed on a base such as a substrate and heated to a temperature equal to or higher than the melting point of the condensed polycyclic aromatic compound. Then, the dispersion medium is vaporized and removed from the dispersion, and the condensed polycyclic aromatic compound is melted. When this is cooled below the melting point, the fused condensed polycyclic aromatic compound is solidified to form a thin film. Operations for thin film production, such as preparation of the dispersion, supply onto the base of the dispersion, and heating, can be performed in air, but are preferably performed in an inert gas atmosphere such as nitrogen.

The content of the condensed polycyclic aromatic compound in the dispersion is preferably 0.02% by mass or more and 10% by mass or less. If it is less than 0.02% by mass, a defect portion tends to occur in the formed thin film, and if it exceeds 10% by mass, it is difficult to form a thin film having a uniform film thickness. There is. In order to make such inconvenience less likely to occur, the content of the condensed polycyclic aromatic compound in the dispersion is more preferably 0.03% by mass or more and 5% by mass or less, and 0.05% by mass or more. More preferably, it is 3 mass% or less.
Examples of the method of disposing the dispersion of the condensed polycyclic aromatic compound on the base such as a substrate include a method of bringing the base into contact with the dispersion in addition to coating and spraying. Specific examples include known methods such as spin coating, dip coating, screen printing, ink jet printing, blade coating, printing (lithographic printing, intaglio printing, letterpress printing, etc.).

  Various materials can be used as a base material for forming the organic semiconductor thin film. Examples include ceramics such as glass, quartz, aluminum oxide, magnesium oxide, silicon, gallium arsenide, indium tin oxide (ITO), zinc oxide, mica, and metals such as aluminum, gold, stainless steel, iron, and silver. It is done. Polyester (polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, etc.), polycarbonate, norbornene resin, polyether sulfone, polyimide, polyamide, cellulose, silicone resin, epoxy resin, carbon, paper, etc. It is done. Or these composite_body | complexes may be sufficient. However, when the base is swollen or dissolved by the dispersion medium and inconvenience occurs, it is preferable to provide a barrier layer in order to prevent the dispersion medium from diffusing into the base.

The shape of the base is not particularly limited, but a film-like base or a plate-like base (substrate) is usually used. Furthermore, a linear body or a fiber structure can also be used as a base.
Thus, the organic semiconductor thin film of the present invention can be manufactured by a wet process. Therefore, since the thin film can be manufactured at a low temperature, simply and in a short time as compared with the conventional dry process, the productivity is high and the cost is low. According to the present invention, since a thin film of a condensed polycyclic aromatic compound that has been previously insoluble or hardly soluble can be produced by a wet process, the number of materials that can be thinned can be increased.

  The organic semiconductor thin film thus produced has high crystallinity and high carrier mobility. When the organic semiconductor thin film of the present invention is analyzed by the wide angle X-ray diffraction method, a diffraction peak of (00n) plane in which the conjugate planes of the condensed polycyclic aromatic compound are arranged in the direction perpendicular to the base surface is observed (n Is an integer). However, when estimated from the observed inter-plane distance, the conjugated surface of the condensed polycyclic aromatic compound and the surface of the base are not necessarily perpendicular, and may have a structure inclined by 5 to 20 °. Of the diffraction peaks on the (00n) plane, those having a diffraction angle 2θ in the range of 5 to 10 ° can be evaluated for crystallinity by comparing the half widths. Generally, the half width of the diffraction peak of the organic semiconductor thin film by the vapor deposition method is about 0.1 to 0.3 °, but the half width of the diffraction peak of the organic semiconductor thin film obtained by the manufacturing method according to the present invention is It is 0.1-0.4 degree and has the crystallinity equivalent to a vapor deposition method.

By using such an organic semiconductor thin film, a semiconductor element useful in fields such as electronics, photonics, and bioelectronics can be manufactured. Examples of such semiconductor elements include diodes, transistors, thin film transistors, memories, photodiodes, light emitting diodes, light emitting transistors, sensors, and the like.
Transistors and thin film transistors can be used in displays, such as liquid crystal displays (for example, active matrix liquid crystal display devices), dispersive liquid crystal displays, electrophoretic displays, particle rotating display elements, electrochromic displays, organic light emitting displays, It can be used for various display elements such as electronic paper. Transistors and thin film transistors are used in these display elements as display pixel switching transistors, signal driver circuit elements, memory circuit elements, signal processing circuit elements, and the like. For example, when the organic semiconductor thin film of the present invention is used in an active matrix liquid crystal display device, the device can be improved in image quality, power consumption and space saving, and can be made flexible and lightweight.

  When the semiconductor element is a transistor, the element structure includes, for example, a structure of substrate / gate electrode / insulator layer (dielectric layer) / source electrode / drain electrode / semiconductor layer, substrate / semiconductor layer / source electrode. -Structure of drain electrode / insulator layer (dielectric layer) / gate electrode, substrate / source electrode (or drain electrode) / semiconductor layer + insulator layer (dielectric layer) + gate electrode / drain electrode (or source electrode) The structure etc. are mention | raise | lifted. At this time, a plurality of source electrodes, drain electrodes, and gate electrodes may be provided. Further, a plurality of semiconductor layers may be provided in the same plane or may be provided in a stacked manner.

  As the structure of the transistor, either a MOS (metal-oxide (insulator layer) -semiconductor) type or a bipolar type can be employed. Since the condensed polycyclic aromatic compound is usually a p-type semiconductor, it may be combined with a condensed polycyclic aromatic compound that has been donor-doped to form an n-type semiconductor, or may be combined with an n-type semiconductor other than the condensed polycyclic aromatic compound. By doing so, an element can be constituted.

When the semiconductor element is a diode, the element structure includes, for example, a structure of electrode / n-type semiconductor layer / p-type semiconductor layer / electrode. And the organic-semiconductor thin film of this invention is used for a p-type semiconductor layer, and the above-mentioned n-type semiconductor is used for an n-type semiconductor layer.
At least a part of the interface between the organic semiconductor thin film in the semiconductor element or the surface of the organic semiconductor thin film and the electrode can be a Schottky junction and / or a tunnel junction. An organic semiconductor element having such a junction structure is preferable because a diode or a transistor can be manufactured with a simple structure. Furthermore, a plurality of organic semiconductor elements having such a junction structure can be joined to form elements such as an inverter, an oscillator, a memory, and a sensor.

  Further, when the organic semiconductor element of the present invention is used as a display element, it can be used as a transistor element (display TFT) that is arranged in each pixel of the display element and switches display of each pixel. Since such an active drive display element does not require patterning of an opposing conductive substrate, depending on the circuit configuration, pixel wiring can be simplified compared to a passive drive display element that does not have a transistor for switching pixels. Usually, one to several switching transistors are arranged per pixel. Such a display element has a structure in which a data line and a gate line which are two-dimensionally formed on a substrate surface cross each other, and the data line and the gate line are respectively joined to the gate electrode, the source electrode and the drain electrode of the transistor. ing. It is possible to divide the data line and the gate line, and to add a current supply line and a signal line.

In addition to the pixel wiring and the transistor, a capacitor can be provided in addition to the pixel of the display element to provide a signal recording function. Furthermore, a data line and gate line driver, a pixel signal memory, a pulse generator, a signal divider, a controller, and the like can be mounted on the substrate on which the display element is formed.
The organic semiconductor element of the present invention can also be used as an arithmetic element and a storage element in an IC card, a smart card, and an electronic tag. In that case, even if these are a contact type or a non-contact type, they can be applied without any problem. The IC card, smart card, and electronic tag are composed of a memory, a pulse generator, a signal divider, a controller, a capacitor, and the like, and may further include an antenna and a battery.

  Furthermore, if the organic semiconductor element of the present invention is configured as a diode, an element having a Schottky junction structure, or an element having a tunnel junction structure, the element can be used as a light receiving element such as a photoelectric conversion element, a solar cell, an infrared sensor, or a photodiode. It can be used as a light emitting element. In addition, when a transistor is constituted by the organic semiconductor element of the present invention, the transistor can be used as a light emitting transistor. A known organic material or inorganic material can be used for the light emitting layer of these light emitting elements.

  Furthermore, the organic semiconductor element of the present invention can be used as a sensor, and can be applied to various sensors such as a gas sensor, a biosensor, a blood sensor, an immune sensor, an artificial retina, and a taste sensor. Usually, the measurement object can be analyzed by a change in the resistance value of the organic semiconductor thin film that occurs when the measurement object is brought into contact with or adjacent to the organic semiconductor thin film constituting the organic semiconductor element.

Hereinafter, the present invention will be described more specifically with reference to examples.
[Example 1]
A dispersion in which 2,3,9,10-tetramethylpentacene powder (10 mg) and chloroform (1 ml) are mixed and 2,3,9,10-tetramethylpentacene powder is uniformly dispersed (dispersion which is a constituent of the present invention) Corresponding to). This dispersion was spread on a silicon substrate having an oxide film on the surface, and chloroform was evaporated to form a laminate of 2,3,9,10-tetramethylpentacene powder. When this silicon substrate was held at 280 ° C. for 10 minutes under a nitrogen atmosphere, the 2,3,9,10-tetramethylpentacene powder on the surface of the silicon substrate was melted to form a uniform thin film.

When the structure of this thin film was analyzed by the wide-angle X-ray diffraction method, a diffraction peak on the (00n) plane (n is an integer of 1 to 3) corresponding to the inter-plane distance of 16.8 nm was observed. And the half-value width of this diffraction peak was 0.2 degree, and it was confirmed that a thin film is highly crystalline.
Next, a silicon substrate made of n-type silicon and provided with an oxide film having a thickness of 200 nm on its surface was prepared, and a gold electrode pattern was formed on the surface by photolithography. A laminated body of 2,3,9,10-tetramethylpentacene powder is formed on the silicon substrate on which such an electrode pattern is formed in the same manner as described above, and heat treatment is performed in the same manner as described above to form an organic semiconductor thin film. Then, a field effect transistor was manufactured. The field effect transistor characteristics were evaluated using the silicon substrate of the field effect transistor as the gate electrode and the gold electrode on the surface as the source / drain electrodes. As a result, the field effect mobility was 1.2 cm ² / V · s, and the on / off current ratio was 1 × 10 ⁴ .

[Example 2]
10 mg of hexadodecyl hexabenzocoronene powder and 1 ml of isopropyl alcohol were mixed to prepare a dispersion in which the hexadodecyl hexabenzocoronene powder was uniformly dispersed. This dispersion was developed on a silicon substrate having an oxide film on the surface, and isopropyl alcohol was evaporated to form a laminate of hexadodecyl hexabenzocoronene powder. When this silicon substrate was held at 150 ° C. for 10 minutes in a nitrogen atmosphere, the hexadodecyl hexabenzocoronene powder on the surface of the silicon substrate was melted to form a uniform thin film.
When the structure of this thin film was analyzed by the wide-angle X-ray diffraction method, a diffraction peak on the (00n) plane (n is an integer of 1 to 3) corresponding to the inter-plane distance of 20.8 nm was observed. And the half width of this diffraction peak was 0.24 °, and it was confirmed that the thin film was highly crystalline.

Next, a silicon substrate made of n-type silicon and provided with an oxide film having a thickness of 200 nm on its surface was prepared, and a gold electrode pattern was formed on the surface by photolithography. On the silicon substrate on which such an electrode pattern is formed, a laminate of hexadodecyl hexabenzocoronene powder is formed in the same manner as described above, and an organic semiconductor thin film is formed by heat treatment in the same manner as described above. Was made. The field effect transistor characteristics were evaluated using the silicon substrate of the field effect transistor as the gate electrode and the gold electrode on the surface as the source / drain electrodes. As a result, the field effect mobility was 0.05 cm ² / V · s, and the on / off current ratio was 1 × 10 ⁴ .

Example 3
A laminate of tetradodecylhexabenzocoronene powder was formed on a silicon substrate in the same manner as in Example 2 except that tetradodecylhexabenzocoronene powder was used. When this silicon substrate was held at 190 ° C. for 10 minutes in a nitrogen atmosphere, the tetradodecylhexabenzocoronene powder on the surface of the silicon substrate was melted to form a uniform thin film.
When the structure of the obtained thin film was analyzed by the wide-angle X-ray diffraction method, a diffraction peak of (00n) plane (n is an integer of 1 to 4) corresponding to the inter-plane distance of 39.4 nm was observed. The half width of this diffraction peak was 0.10 °, and it was confirmed that the thin film was highly crystalline.
Next, the characteristics of the field effect transistor produced in the same manner as in Example 2 were evaluated. As a result, the field effect mobility was 0.08 cm ² / V · s, and the on / off current ratio was 1 × 10 ⁵ .

Example 4
25 mg of 2,3,9,10-tetrapropylpentacene powder and 3 ml of mesitylene were mixed to prepare a dispersion in which 2,3,9,10-tetrapropylpentacene powder was uniformly dispersed. This dispersion was spread on a silicon substrate having an oxide film on the surface, and mesitylene was evaporated to form a laminate of 2,3,9,10-tetrapropylpentacene powder. When this silicon substrate was held at 220 ° C. for 10 minutes under a nitrogen atmosphere, the 2,3,9,10-tetrapropylpentacene powder on the surface of the silicon substrate was melted to form a uniform thin film.
When the structure of this thin film was analyzed by the wide-angle X-ray diffraction method, a diffraction peak on the (00n) plane (n is an integer of 1 to 4) corresponding to an interplane distance of 18.0 nm was observed, and the thin film was highly crystalline. It was confirmed that there was.

Next, a silicon substrate made of n-type silicon and provided with an oxide film having a thickness of 200 nm on its surface was prepared, and a gold electrode pattern was formed on the surface by photolithography. A laminated body of 2,3,9,10-tetrapropylpentacene powder is formed on the silicon substrate on which such an electrode pattern is formed in the same manner as described above, and heat treatment is performed in the same manner as described above to form an organic semiconductor thin film. Then, a field effect transistor was manufactured. The field effect transistor characteristics were evaluated using the silicon substrate of the field effect transistor as the gate electrode and the gold electrode on the surface as the source / drain electrodes. As a result, the field effect mobility was 0.85 cm ² / V · s, and the on / off current ratio was 1 × 10 ⁴ .

[Comparative example]
A laminate of hexabenzocoronene powder was formed on a silicon substrate in the same manner as in Example 2 except that unsubstituted hexabenzocoronene powder was used. This silicon substrate was held at 300 ° C. for 30 minutes under a nitrogen atmosphere, but the hexabenzocoronene powder on the surface of the silicon substrate did not melt while the powder form was maintained, and a thin film was not formed. Therefore, when the silicon substrate was held at 400 ° C. for 30 minutes in a nitrogen atmosphere, the hexabenzocoronene powder on the silicon substrate surface sublimated and disappeared from the silicon substrate.

  Next, a silicon substrate made of n-type silicon and provided with an oxide film having a thickness of 200 nm on its surface was prepared, and a gold electrode pattern was formed on the surface by photolithography. On the silicon substrate on which such an electrode pattern was formed, a hexabenzocoronene powder laminate was formed in the same manner as described above, and held at 300 ° C. for 30 minutes in a nitrogen atmosphere. The field effect transistor operation of this laminate was investigated, but no current modulation between the source and drain due to a change in gate voltage was observed. Further, the resistance between the source and the drain was extremely high, and it was found that the contact between the electrodes was poor.

  The present invention is suitable for electronics, photonics, bioelectronics and the like.

Claims (4)

A method for producing an organic semiconductor thin film comprising a condensed polycyclic aromatic compound having a polycyclic structure in which 2 or more and 15 or less benzene rings are condensed,
A dispersion in which the condensed polycyclic aromatic compound is dispersed in a dispersion medium is disposed on a base, and heated to a temperature equal to or higher than the melting point of the condensed polycyclic aromatic compound to vaporize the dispersion medium and the condensed polycyclic aromatic compound. A method for producing an organic semiconductor thin film, comprising melting a ring aromatic compound. The method for producing an organic semiconductor thin film according to claim 1, wherein the condensed polycyclic aromatic compound has a structure represented by the following chemical formula (I).

(I)
However, at least a part of the functional groups R ₁ , R ₂ , R ₃ and R _{4 in} the chemical formula (I) is a hydrocarbon group such as an alkyl group, an alkenyl group or an alkynyl group, an alkoxyl group, an ether group or a halogen group. , A formyl group, an acyl group, an ester group, a mercapto group, a thioalkyl group, a sulfide group, a disulfide group, a sulfonyl group, or a functional group containing two or more of them, and the other part is a hydrogen atom. In addition, at least one of the functional groups X and Y in the chemical formula (I) is a hydrogen atom or a halogen group, and n is an integer of 2 or more and 7 or less.   An organic semiconductor thin film manufactured by the method for manufacturing an organic semiconductor thin film according to claim 1.   An organic semiconductor element comprising at least a part of the organic semiconductor thin film according to claim 3.