JPS6023906A - Method of forming semiconductive organic thin film - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to a method for forming a semiconducting organic thin film, and more specifically, the present invention relates to a method for forming a semiconducting organic thin film, and more specifically, a method for forming a semiconducting organic thin film with good crystallinity and high mobility of charge carriers. It relates to a method for forming organic thin films.

[Technical background of the invention and its problems]

Conventionally, semiconducting thin films were mainly made of inorganic compounds of simple elements such as Si and Ge or complex elements such as GaAs*InP, and were generally formed on solid substrates by liquid phase growth or vapor phase growth. 1. However, unlike homogeneous compounds, organic compounds have advantages such as high light absorption and ease of fabrication into large areas, so in recent years semiconducting thin films made of organic compounds have been developed. has been attracting attention.

Semiconducting organic enzymes HK known up to now include polymer films such as polyacetylene and polyno-42 phenylene sulfide, and pigment films such as β-kaline and merocyanine.

However, in all thin films, the organic compounds forming the layers were amorphous or crystalline with extremely many defects.
Their properties as semiconductors are generally poor, especially the mobility of carriers, which is higher than that of inorganic semiconductors. 8～”/1
It was as low as 0.010. That is, for example, in the case of a semiconductive organic thin film made of polyacetylene, it is usually obtained by polymerizing acetylene monomer using a suitable catalyst, but the material formed by this method is a polyacetylene polymerized in the form of fibers. Because the particles have an irregularly entangled structure, this causes carrier traps, and the carrier mobility is extremely low. Therefore, this defect has been a major problem when applying the I-reacetylene semiconductor to electronic devices such as solar cells.

There are two reasons why the above defects occur.

(13 The acetylene monomer film before polymerization was not necessarily crystalline1゜(2) Because the catalyst was dispersed, the polymerization reaction started everywhere.9 Therefore, a uniform crystalline film could not be obtained. Therefore, even if it is limited to -dimensional order, bond alternation defects will be introduced.

Therefore, in order to eliminate such defects, a method can be considered to form a single crystal of acetylene monomer RW Bek on a substrate and give energy to it to cause homopolymerization, but in this method, nucleation Unless a slow monomer is used, there is a drawback that the resulting breast becomes a N11 polycrystalline body and grain boundary defects increase.

On the other hand, it is known that when single crystals of diacetylene monomers are similarly in-phase polymerized, the monomer single crystals do not undergo distortion due to volume changes due to polymerization and form high-quality polymer crystals. . However, a method for forming a polyacetylene crystal thin film has not yet been known.

For this reason, the open Langmuir-Prodgett method (L, B
law) f! A method of forming the thin film using the method is currently being studied. However, in the L and B methods, a monomolecular film is formed on a solvent, this is spread on a substrate, and then polymerized, so it is difficult to form a film with a thickness of several molecular layers or more.
Furthermore, since a monomolecular film must be formed on a solvent (usually water), it is necessary to introduce hydrophobic and hydrophilic groups at the ends of the molecular chains, which places significant restrictions on the types of monomers that can be used. .

[Purpose of the invention]

An object of the present invention is to provide a semiconducting organic thin Mu'fc having good crystallinity and high carrier mobility, which can be applied as an electronic device.

[Summary of the invention]

The method for forming a semiconducting organic thin film of the present invention involves forming a thin film made of a single crystal of an organic compound monomer on a solid substrate, and then heating the layer at a temperature below its melting point, or heating the layer at a temperature below its melting point. wavelength 1
It is characterized in that the organic compound is solid phase polymerized by irradiation with electromagnetic waves or electron beams of ~10 arms, thereby producing a polymer single crystal of the compound.

The present invention will be explained in more detail below.

In the present invention, first, a thin film made of a single crystal of an organic compound monomer is formed on a solid substrate. The solid substrate on which the thin film is formed may be made of any conventionally used material, including glass substrates such as quartz glass and borosilicate glass, silicon, graphite, and germanium. , a crystalline substrate such as gallium arsenide, and the like. In addition, as an organic compound, it is possible to form a thin film as a single crystal on a substrate, and a polymer single crystal is generated by heating or electromagnetic wave irradiation, and the resulting polymer has semiconductivity. may be of any value, but the following formula: % formula % (wherein Hl and R2 may be the same or different,
(CH2) CH3, (CR2)n OH1(
CR2)n C02H or its salt, (CI42)
n O' CONH@ (CH2) 0-8O2RC) TOCH3, -Cmi c-c
It is preferable to use a diacetylene monomer represented by the following formula: -CmiCC1hO'-CO-NH[); n represents an integer from 1 to 10).

Methods for forming an R film made of a single crystal of an organic compound monomer on a solid substrate include, for example, a vacuum thin film formation method and a chemical vapor deposition method (so-called Chemi-cal vapor deposition method).
or deposition), Sufu 9 Tsutaring method,
Examples include a liquid phase growth method, but a vacuum thin film forming method is preferable. Vacuum thin film production methods include, for example, resistance heating method or vacuum evaporation method using electron beam method; ion beam method using direct current method, radio frequency method, cluster ion beam method or hot cathode method, etc. , resistance heating method, cluster ion beam method, and hot cathode method are preferred. In any of the vacuum film forming methods described above, a monomer single crystal thin film can be formed on a fixed substrate by using the same conventional equipment and operating according to a conventional method.

)I heno♀ is usually 10-100OX. When using the vapor deposition method, the organic compound is usually 10-6 to 1O-8.
A thin film consisting of a single crystal of an organic compound monomer can be obtained by heating the solid substrate under a pressure of 60 to 200'' CTC and then cooling it. It is preferable to heat the film in advance to remove the natural oxidation layer on the surface of the plate.

Next, in the present invention, a thin film made of a single crystal of an organic compound monomer is heated or the layer is irradiated with electromagnetic waves to cause in-phase polymerization of the compound to form a semiconducting organic thin film made of a polymer single crystal. # In polymerization, it is also possible to use heating and electromagnetic wave irradiation in combination 1. Usually, this polymerization reaction:
It is carried out under normal pressure in an inert gas (for example, argon gas, etc.) atmosphere. When solid phase polymerization is carried out by heating, it is necessary to carry out the polymerization at a temperature below the melting point of the monomer.
Heat for 30 hours. On the other hand, in the case of solid phase polymerization by electromagnetic wave irradiation, microwaves with a wavelength of 100 to 1 m, visible light,
Energy rays of one or more of ultraviolet light, X-rays, gamma rays, and electron beams are irradiated.
It is preferable to irradiate with a line. Irradiation time is usually several seconds to 30 hours. In general, diacetylene monomer〇 single crystals are colorless or pale pink, but once polymerization is complete, they turn golden yellow. Since it changes into lydiacetylene crystals, heating or magnetic wave irradiation can be stopped using this color change as a guide. In addition, K is added to increase the conductivity of the obtained semiconductive organic thin film.

It is possible to perform the in-phase polymerization in an inert atmosphere containing a dopant such as PF4, PFg, AsF6, etc., or to leave the thin film in an inert atmosphere containing the dopant after polymerization; Furthermore, it is also possible to implant ions such as Ni+, Na+, Li+, etc. into the thin film.

According to the above thin film forming method, since the orientation of the monomer single crystal is maintained as it is and the same phase polymerization is carried out, a semiconducting organic thin film having high quality polymer crystalline gold can be obtained. The conductivity of the organic thin film obtained in the present invention is in the range of 10-16 to 10'' Ω m when diacetylene monomer is used, and the carrier mobility tit is 10 to 10' twr2.
/ V-see.

[Effect of departure]

According to the present invention, a semiconducting organic thin film can be obtained which has excellent properties such as good crystallinity and high carrier mobility. Therefore, by using the thin film, it is possible to provide various electronic devices.

[Embodiments of the invention]

In this example, the diacetylene monomer shown below was used.

R''-C=C-C=C-R2 Example 1 PTSt- was used as a diacetylene monomer, and a thin M of the monomer was formed in the vacuum evaporation apparatus shown in the figure. A PTS is housed in this, 2 is a Wmata Mo heater that heats the evaporation source, and 3 is a PT
A liquid nitrogen shroud is installed around the evaporation source to completely prevent impurities from entering the S.

In this embodiment, first, the inside of the vacuum chamber 4 is set at 10 to 10 Torr.
Exhausted until. Next, the heater 5 for heating the substrate is energized to heat the substrate (S: wafer 1, (100) side) 6 at
The sample was heated to 00° C. to remove the natural oxidation layer on the surface 1. During this time, the shutter 7, which also served as a heat shield, was kept closed. After the substrate temperature decreased to the chamber, the heater 2 was energized to heat the evaporation source 1 to 60°C to 200°C, and the shutter 7 was opened to start evaporating N. During this time, the temperature inside the vacuum chamber was 10-6T.
It was kept below orr. In this way, a film with a thickness of 100 to 10,000 A was formed on the silicon wafer. When this film was analyzed by X-ray diffraction, a sharp dominant orientation was observed. 12 Next, this film was kept at 60°C in an argon atmosphere of 1 atm and left for 12 hours, giving it a golden gold 1'A luster. have 19 A lydiacetylene film was obtained.1 When this film was analyzed by X+tdJ diffraction method, it was clear that the b-axis (main chain axis) of the bulk single crystal was oriented parallel to the film surface. . In addition, the in-plane conductivity of this film was 10-8 to 10-10 Ω-1 crn-'', and no in-plane anisotropy was observed.1 Photoconductivity experiments showed that carrier mobility When measured, 3×10' −/
It was found that V-sec showed extremely high mobility1. When this film was left in argon gas (1 atm) containing 1% AsF5 for 24 hours, the conductivity was 10
It increased to ~1Ω-1ffi-1.

Example 2 A polydiacetylene single crystal obtained by solid phase polymerization of P and TS single crystals was used as the substrate, but in the same manner as in Example 1. PTS monomer was deposited on the Ul'+ surface of the polydiacetylene single crystal. did. However, the substrate was not heat-treated. Note that the arm opening plane is a plane parallel to the main chain of the polydiacetylene crystal. The obtained monomer film has a thickness of 100~1oooo'A
As a result of X-ray crystal analysis, it was found that the film was grown in a lattice-matched manner to the underlying polydiacetylene single crystal. ) to polymerize by heating to 70°C. When a gold electrode was placed on top of this theory and the conductivity was measured using the four-terminal method, it was found that
It was 10-4 to 10-1Ω-1 sub-1. On the other hand, when we attached a gold electrode to the underlying polydiacetylene (PTS) single crystal and measured the electrical conductivity, we found that it was 10'-150-" crn
-''. From this, it was found that only the polydiacetylene single crystal film grown on the underlayer had high conductivity due to PFa dosing. Also, this case was different from Example 1. On the other hand, in-plane anisotropy was found for electrical conductivity, and when the electrical conductivity in the direction parallel and perpendicular to the main chain axis is expressed as a/ and -, respectively, a//6 is approximately 103 to 104. there were.

When the Hall mobility was evaluated by measuring the Hall effect, an extremely high value of LO4 to 1O56/I/V-8ec was actually measured.

Example 3 HDU was used as a monomer, and the open plane of a PTS polydiacetylene single crystal was used as a base. The arm opening plane is parallel to the main chain. Using the vapor deposition apparatus shown in the figure, HDU was charged into an evaporation source and heated to 100 to 200°C. Using a liquid nitrogen shroud, polymerized components with low vapor pressure were removed so that only the monomers reached the substrate, and a monomer film containing 100 to 1000 monomers was formed on the substrate. Next, this film was irradiated with ultraviolet light of about 10 eV to polymerize the monomer. This is then added to 1“ accelerated to about 100 KeV.
Ion implantation. When a gold electrode was provided on the surface and the electrical conductivity was measured using a four-terminal method, it was found to be 10-4 to 10 Ωf. In-plane anisotropy is seen in the electrical conductivity, and σ/σ
was about lO5~10'.Evaluating the mobility in the main chain direction of the conductivity, it was about 10t.
yl/V*sec.・Example 4 Using GaAs ((100) plane) as the substrate and using TCDU as the monomer, Ga was prepared in the same manner as in Example 1.
A thin film of TCDU was deposited on the As (100) surface.

However, the GaAs substrate was cleaned not by heat treatment but by glow discharge under an argon gas atmosphere at 10<-2 >Torr in a vacuum chamber prior to vapor deposition. Then 10
-' Exhaust to below Torr, evaporation source fc60℃~20
After heating to 0°C, the shutter was opened to perform vapor deposition.

During this time, the inside of the vacuum chamber was maintained at 10-6 Tor'r or less.

In this way, GaAs! -77-100-1 on top
A film containing 0,000 layers was formed. When this film was analyzed by X-ray diffraction, a sharp dominant orientation was observed. When this film was kept at 100° C. in an argon atmosphere of 1 atm and left for 12 hours, a polydiacetylene film having a golden luster was obtained. When this was analyzed by X-ray diffraction, it was found that the b-axis (main chain Ill) of the bulk single crystal was oriented parallel to the film surface. Electrical conductivity in the in-plane direction of B'J a 10"
6') at ~10"Ω-1cnl-", and there was no in-plane anisotropy. When the total carrier mobility was measured in a photo-dissipation experiment, it was found to be 3 x 10' cnV V' sec, which is an extremely high mobility. This fishing is 1 piece PF
When left for 24 hours in an argon gas atmosphere (1 atm) containing S, the conductivity increased to 10-1 Ω cm.

[Brief explanation of drawings]

The drawing is a schematic diagram of the vacuum evaporation equipment used in this example. l... Evaporation source, 2... Heater, 3... Liquid nitrogen shroud, 4... Vacuum chamber, 5... Substrate heater,
6... Board, 7... Shutter, 8... Exhaust system.

Claims (1)

[Claims] A thin film made of a single crystal of an organic compound monomer is formed on a solid substrate, and then the layer is heated at a temperature below the melting point, or the layer is coated with a material having a wavelength of 1 to 10"-" 1. A method for forming a semiconducting organic thin film, which comprises irradiating the organic compound with electromagnetic waves or electron beams to in-phase polymerize the organic compound, thereby producing a t5 reamer single crystal of the compound. (2) MA (semiconducting organic enzyme) according to claim 1, wherein the organic compound is a diacetylene compound. (3) A method for forming a semiconducting organic thin film according to claim 1, wherein a thin film made of crystals of an organic compound monomer is formed on a solid substrate using a vacuum thin film forming method. (4) The method for forming a semiconductive organic H film according to claim 3, wherein the vacuum thin film forming method is a vacuum evaporation method or an ion blating method.