JPH02200688A - Organic complex and electrically conductive ultrathin film - Google Patents

Abstract

NEW MATERIAL:The electrically conductive charge-transfer organic complex having hydrocarbon group and expressed by formula (R<1> to R<3> are long-chain alkyl or aryl; Me is methyl). EXAMPLE:Tri-n-decylmethylumonium-bis[(4,5-dimercapto)-1,3-dithiol-2-on e]gold complex. USE:A display element, information memory device, ultrathin film switching element, wiring material for ultra-high-density LSI. PREPARATION:The organic complex of formula can be produced e.g. by reacting a methanol solution of 4,5-bis(benzoylthio)-1,3-dithiol-2-thione with metallic sodium, adding and reacting sodium tetrachloroaurate(III) dihydrate to the reaction product and reacting the product with tri-n- decylmethylammonium bromide. An electrically conductive ultrathin film is produced by forming an ultrathin film of the complex by Langmuir Blodgett method and oxidizing the film.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to an organic complex that enables the formation of an electrically conductive ultra-thin film and an electrically conductive ultra-thin film containing the same.

(Prior Art) It is a well-known fact that a thin film of an organic compound is formed on a solid substrate using the Langmuir-Prodgett method. Thin films produced in this way are of interest in many applications, especially in the fields of electronics and biology. JP-A-58-141246 describes several examples in which an ultra-thin film formed by the Langmuir-Prodgett method [Langmuir-Prodgett film (LB film)] is applied to devices.

LB film is an ultra-thin film obtained by creating a monomolecular film of organic molecules on a water surface and accumulating this on a solid substrate. It is expected that if various current electronic devices can be made from ultra-thin films of such organic materials, higher functionality will be achieved.

However, when constructing a conductive device using such an organic compound, a material having physical properties as a good conductor is required for the LB film. Past B
The membrane consists of long-chain pyridinium and tetracyanoxydimethane (T
A value of 0.01 siemens per centimeter (S/cm) has been obtained by treating the 1=1 complex of CNQ) with 2 steam (A, Ruaudel-Teixier
etc.: Mo1. Cryst, Liq, Cryet, 12
0319 (1985)).

The present inventors also obtained a conductivity of 0.015/cm without I2 treatment with a 1:2 complex of long-chain pyridinium and TCNQ (M, Nakamura et al.: Chem, Let
t, 709 (1986), M.

Matsumoto et al.: 5ynthetic Meta
ls, 19675 (1987)).

The present inventors also developed a monomolecular film of tetramethyltetrathiafulvalene (TMTTF) and a long-chain TCNQ complex, and L
B film was created and a conductivity of 0.43/cm was obtained (
T. Nakamura et al.: Chem, 1ett, 32
3 (1986), Y. Kavabata et al.: 5ynth
eric Metals, 19663 (1987), T
, Nakaaura et al.: 5ynthetic Meta
ls, 19681 (1987), M, Matsumot
o etc.: 3rd Int'l Conf, LB File
ms, Abstract No OF2, K, Ike
gami etc.: 5ynthetic Metals
, 19 669 (1987)).

Furthermore, the present inventors synthesized a 1:1 complex of dialkyldimethylammonium-Ni(dmit)2, and subjected it to bromine oxidation or electrolytic oxidation. An electric shock rate of IS/cm has been obtained (T, Nakamura et al.: Chem 1
ett, 1667 (1988)).

On the other hand, logs etc. are tetrathiafulvalene (TTF) and T
reported a conductivity of 5.53/cm by spreading the CNQ complex on the water surface and accumulating it on a solid substrate (M.

Fujiki et al.: 5ynthetic Meta
ls, 18 815 (1987)).

In this way, in order to make the LB film a material that can be applied to molecular-level electronics in the field of electronic engineering,
Since the conductivity is still low, an organic complex for charge transfer with even higher conductivity is desired.

(Problem of the Invention) An object of the present invention is to provide a highly conductive LB film and a conductive charge transfer organic complex therefor.

(Means for Solving the Problems) As a result of the inventors' earnest efforts to solve the above problems,
We synthesized molecules with a hydrophilic group in a conductive charge transfer organic complex whose conductivity has been investigated using single crystals and a hydrophobic group in a long-chain hydrocarbon group. We discovered that it is possible to create an ultra-thin film with high conductivity by creating a monomolecular film, accumulating the monomolecular film on a substrate, and then subjecting it to chemical oxidation or electrolytic oxidation in an aqueous electrolyte solution. The present invention has now been completed.

According to the present invention, a conductive charge transfer organic complex represented by the formula (wherein R1, R2, and R3 are long-chain alkyl groups or aryl groups, and Me is a methyl group) is used as a conductive ultra-thin film material. provided.

The cation in the general formula (1) consists of a quaternary ammonium group such as trialkylmethylammonium.

In this case, R1, R2, R2 are long-chain alkyl groups or aryl groups, but they can be the same or different. As a long chain alkyl group, carbon number is 10
Of the above, linear ones with 10 to 24 atoms are particularly preferable, specifically decyl, randecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, hexadecyl, heptadecyl,
Examples include octadecyl, nonadecyl, eicosyl, oreicosyl, doeicosyl, trieicosyl, and tetraeicosyl groups. Examples of the aryl group include phenyl, tolyl, xylyl, and biphenyl groups. Specific examples of quaternary ammonium groups that form cations include systems mixed with long-chain fatty acids and/or long-chain aliphatic hydrocarbons, which will be described later. From the point of view of providing a conductive LB film, tridecylmethylammonium, triundecylmethylammonium,
Examples include tridodecylmethylammonium, ditetradecylmethylphenylammonium, and dihexadecylmethylbiphenylammonium groups.

The conductive charge transfer organic complex represented by the general formula (1) of the present invention is dissolved in a mixed solvent of acetonitrile and benzene and spread as a monomolecular film on a Langmuir trough. In order to create a more stable monomolecular film on the water surface, it is preferable to use a system mixed with long-chain fatty acids and/or long-chain aliphatic hydrocarbons, especially long-chain fatty acids and/or long-chain aliphatic hydrocarbons. 0.0 of the conductive compound (1).
It is desirable to add 3 to 5.0 moles. Note that the long-chain fatty acids and long-chain aliphatic hydrocarbons used here are such that when mixed with the conductive charge transfer organic complex of the present invention, a stable monomolecular film can be developed on the water surface and high conductivity can be obtained. It is important to have characteristics such as having appropriate strength and long-chain fatty acids. Long chain fatty acids are good. in particular,
Caprylic acid, undecylic acid, tridecylic acid, myristic acid, pentadecylic acid, palmitic acid, heptadecylic acid,
Examples include stearic acid, nonadecanoic acid and arachidic acid. As long-chain aliphatic hydrocarbons, linear ones having 8 or more carbon atoms are desirable. Specifically, octane, nonane, decane, undecane, dodecane, tridecane, tetradecane, pentadecane, hexadecane, heptadecane,
Examples include octadecane, nonadecane, eicosane, heneicosane, and tocosane. As mentioned above, the mixing ratio of long-chain fatty acids and/or long-chain aliphatic hydrocarbons is preferably 0.3 to 5.0 times the amount of the conductive charge transfer organic complex. Fatty acids or long-chain aliphatic hydrocarbons may be added singly or as a mixture, but in order to obtain sufficient stability and strength, it is preferable to use them alone. The optimal addition ratio is not clear as it varies depending on the type of conductive compound and the type of long-chain compound, but - around 1:1 is good for boat fishing. −
The optimal ratio when using Au(dmit)2(1:1) complex and arachidic acid as the long chain fatty acid was 2:1 to 4:1.

A general method for forming a thin film of an organic compound on the surface of an aqueous solution is described in prior literature such as Japanese Patent Application Laid-open No. 58-141246. It is carried out by spreading an appropriate amount of a solution of the compound on the water surface and evaporating the solvent. Furthermore, since conductive charge transfer organic complexes may decompose in organic solvents such as chloroform, preferred solvents include:
Acetonitrile and the like are commonly used as a solvent when preparing an organic complex for charge transfer. In this case, since acetonitrile is soluble in water, acetonitrile is used in the form of a mixed solvent with benzene.

Other water-insoluble organic solvents may be used instead of benzene.

The LB film of a conductive charge transfer organic complex accumulated by the Langmuir-Prodgett method is an insulator as it is, but it can be made to have high conductivity by chemical oxidation or electrolytic oxidation.
It can be obtained as a B film.

Among chemical oxidation methods, the method using halogen gas (chlorine, bromine, and iodine) is particularly simple, and involves fixing a substrate to which electrodes have been attached using gold paste in a nitrogen atmosphere.
A conductive ultra-thin film can be created by doping by injecting halogen gas in small quantities using a syringe. Electrolytic oxidation is an electrolytic oxidation reaction using the LB film accumulation substrate as an anode, and is carried out in an aqueous solution containing an electrolyte. The electrolyte may be any material as long as it dissolves in water, has the effect of conducting electricity, and does not react with the LB film accumulated on the substrate, especially LiCQO.
R'4NCQO4, R'4NBF4 and R'4NCF
, SO, (R' being methyl, ethyl, propyl and butyl groups) are preferred. The electrolyte concentration is not particularly limited as long as the electrolytic reaction is sufficiently carried out at room temperature. Electrolytic oxidation uses a constant current power supply to carry out the reaction, and
．． When a 1M #l electrolyte was used, the oxidation of the LB film was sufficient for 2 to 5 hours of reaction at a constant current of 0.5 μA. The current value used here is not particularly limited, and may be any current value that allows the oxidation reaction of the LB film on the solid substrate to proceed smoothly.

(Effects of the Invention) Devices to which the conductive ultra-thin film obtained by the present invention can be applied include display elements, information storage devices, chemically sensitive semiconductor devices, semiconductors including Schottky barriers, etc. The structural requirements for new ultra-thin film switching elements are based on their physical characteristics, and because they are ultra-thin films whose thickness is controlled at the molecular level, ultra-high density L can be fabricated using lithography.
As can be easily estimated from the fine wiring material used in SI and the structure of ultra-thin films, the extremely large anisotropy of conductivity in the plane and vertical directions makes it possible to increase the density of the wiring by making it three-dimensional. . Moreover, since it is made of organic matter, it can also be provided with an interface function with bio-elements.

In devices such as those described above, the conductive charge-transfer organic complex of the present invention can be produced by accumulating a monomolecular layer one layer at a time, compared to other compounds with similar properties; It has the advantage of being able to accurately control the film thickness, and also has higher conductivity compared to conventional products, making it possible to form detailed and fine patterns, as well as high reproducibility and stability. Particularly noteworthy.

(Example) Next, the present invention will be explained in more detail with reference to Examples, but the present invention is not limited thereto.

Reference Example 1 Synthesis of tri-rhodecylmethylammonium bromide tri-n-decylamine 16.7 g (0,038 mol)
and 5.4 g (0,057 mol) of methyl bromide were dissolved in 200 IIIll (158 g) of ethanol,
The mixture was charged into a glass autoclave (No. Q) and stirred well for 80 hours to react while maintaining the temperature at 19 to 20°C (pressure 0, 3 kg/rre). After the reaction was completed, ethanol was distilled off using a rotary evaporator, and recrystallization was performed with 10-ethyl acetate. - 1 g and 2 g of white crystals of tri-rhodecylmethylammonium bromide (purity 99.02%) are obtained in a yield of 89.47% by filtering and drying after leaving overnight.
I got it.

Example 1 Tri-rhodecylmethylammonium-Au (dmit
) Synthesis of 2 920 mg of 4,5-bis(benzoylthio)-1,3-dithiol-2-thione (2
, 25mmoQ) in -1,1 methanol solution 7, and metallic sodium 11
A methanol solution containing 5mg (5mmoQ) of 2o-
When gradually added dropwise, the solution becomes uniform and a reddish-purple 4,5-
Bis(sodiumthio)-1,3-dithiol-2-thione was produced. Furthermore, when 20 mQ of a methanol solution containing 398 mg (1,0 mmoQ) of sodium dihydrate was added to the tetrachrome cap (m), a black sodium-Au (
dmit) 2 [platinum compound of 4,5 bis(mercapto)-1,3-dithiol-2-thione] is formed, and then tri-n-decylmethylammonium bromide 639
When 22 methanol solutions containing mg (1.2 mmon) were gradually added dropwise, ocher-colored crystals of tri-rhodecylmethylammonium=Au (dmit) were precipitated. The reaction was allowed to proceed for an additional 2 hours and then filtered to obtain tri-n-
0.99 g of ocher crystals of decylmethylammonium-Au (dmit)2 were obtained in a yield of 95.0%.

Example 2 The tri-n-decylmethylammonium-Au(dmit)2 (1:1) complex synthesized in Example 1 and arachidic acid were mixed in acetonitrile-benzene (1:1) in a molar ratio of 1=1.
) was dissolved in a mixed solvent of It was found that a stable monomolecular film was formed at a temperature of about 3.5°C m2.This monomolecular film was preliminarily treated with hexamethyldisilazane to make it hydrophobic on a glass plate, and then 20 layers were formed at a surface pressure of 25 mNm-2. This cumulative film was found to form a sufficiently stable monolayer.

Example 3 Electrodes were made using gold paste on the LB film accumulated in Example 2, fixed on a support in a wide mouth bottle at 1° C. equipped with a nitrogen inlet and outlet, and stored while flowing nitrogen. After doping with bromine by injecting a syringe containing bromine vapor into a wide mouth bottle with a fixed substrate in small quantities along with a nitrogen stream,
When the conductivity was measured by the terminal method, a conductivity of 13.05/cm was obtained.

Example 4 Electrodes were made using gold paste on the LB film accumulated by the method of Example 2, and a constant current of 0.5 μ was applied using a platinum wire as the cathode in a 0.1 M/Q lithium perchlorate aqueous solution. When anodized for 5 hours and measured by the 4-probe method, the conductivity was approximately 25
A value of 5/Cm was obtained. This value is the highest value of conductivity ever reported. Moreover, when we investigated the temperature dependence of electrical conductivity, we obtained the results shown in Figure 1.
It was found that near zero, it exhibits metallic behavior, albeit weakly. This macroscopic metallic behavior was observed for the first time in a conductive LB film (Figure 2).
.

[Brief explanation of the drawing]

FIG. 1 is a graph showing the temperature dependence of conductivity. Patent applicant Kozo Iizuka, Director of the Agency of Industrial Science and Technology Sub-Agent Patent Attorney Toshiaki Ikeura

Claims (3)

[Claims] (1) Hydrocarbon represented by the general formula ▲ There are mathematical formulas, chemical formulas, tables, etc. A conductive charge transfer organic complex having a group. (2) An ultra-thin film formed by chemically oxidizing or electrolytically oxidizing an ultra-thin film made of the organic complex of claim (1) formed on a solid substrate. (3) The ultra-thin film according to claim 2, wherein the organic complex contains a long-chain fatty acid and/or a long-chain aliphatic hydrocarbon.