JP3527438B2 - Polysilane chemically bonded to crystalline silicon surface and method for producing the same - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polysilane, which is a polymer compound having a main chain composed of silicon and chemically bonded to the surface of crystalline silicon at its main chain terminal, and a crystalline silicon-polysilane bond. Further, the present invention relates to a method for producing polysilane chemically bonded to the surface of crystalline silicon at its main chain terminal.

[0002]

2. Description of the Related Art Polysilane, which is a polymer compound whose main chain is composed only of silicon and whose side chain is composed of organic substituents, has a σ electron of a silicon-silicon single bond forming the main chain throughout the main chain. By being delocalized, it has various semiconductor properties. In fact, photoconductivity [M. Fujino (M. Fujin
o), Chemical Physics Letters (Chem. Phys. L
et al., Vol. 136, p. 451 (1987)], high hole mobility [M. M. Abkowitz and others,
Solid State Communication (Solid Stat
e Commun.), Vol. 62, p. 547 (1987)],
Electroluminescence [H. Suzuki, Advanced Materials (Adv. Mat.), Volume 8, p.657 (199)
6)] has been observed using a polysilane thin film. Polysilane as an organic semiconductor material has been actively researched for practical use as a charge transport material and an ultraviolet light source material.

Among the characteristics of polysilane, the most different characteristic from that of crystalline silicon is that polysilane exhibits extremely sharp light emission in the ultraviolet region. This is caused by the direct transition type band structure of polysilane based on the reduction of the silicon skeleton and the exciton confinement effect. Crystalline silicon is a material that forms the center of a semiconductor device that is actually used, but it does not have a light emitting property because it has an indirect transition type band structure. Therefore, if it becomes possible to add a light emitting function to a silicon device, there is a high possibility that a new composite device can be constructed.

In constructing such a composite device composed of silicon and a silicon compound, a method of forming a bond between a plurality of silicon skeleton compounds, for example, crystalline silicon and polysilane is extremely important. Crystalline silicon is the most useful semiconductor material in the industry, and it has extremely high controllability of carrier type and resistance depending on the type and amount of dopant.
The controllability of the surface structure is also extremely high. On the other hand, polysilane has a light emitting property which is lacking in crystalline silicon. Furthermore, silicon is also abundant as a resource amount (the Clark number is second highest), and it is not necessary to take measures against highly toxic elements such as arsenic and phosphorus used in other compound semiconductors. Therefore, it can be said that the composite device containing crystalline silicon and polysilane is a practical and realistic material.

Furthermore, in recent years, the development of molecular elements utilizing the merit of single molecule scale has been activated in place of the device development depending on the silicon semiconductor microfabrication technology, which is approaching the limit. Toward such a goal, we must start by treating individual single molecules individually. However, it is not easy to take out one or several molecules independently of each other among several molecules (about 10 ²³ ) of Avogadro,
One method for independently immobilizing single molecules on a substrate is to use a chemical reaction of one molecule to one molecule. If it becomes possible to selectively chemically bond a semiconductor polymer such as polysilane to another substance at the end of its main chain, it will not only be useful for realizing a molecular device utilizing the single molecule characteristics of polysilane itself. It is considered possible to use polysilane as a molecular wire connecting two or more molecular devices.

As a method for fixing the end of polysilane to a solid surface by a chemical bond, for example, a method of reacting a lithiated polysilane on a solid surface whose surface is modified with a halogenoalkyl group has been reported [Ebata et al. Japanese Patent Application No. 10-25992, K.K. K. Ebata and others, Journal of the American Chemical Society (J. Am. Chem. Soc.), Volume 120, 736
7 (1998)]. This method of providing a modified surface by the silane coupling method utilizes the hydroxyl groups present on the substrate surface. Therefore, the same method can be applied to the surface of crystalline silicon by forming a hydroxyl group on the surface by immersing crystalline silicon in an appropriate acid and subjecting it to hydrophilic treatment. However, when this method is used, it is inevitable that an oxide film of 100 Å or more is simultaneously formed on the surface of crystalline silicon during the hydrophilic treatment.

In constructing a composite device composed of crystalline silicon and polysilane, it is necessary to utilize the electronic interaction between the two. The oxide film existing on the surface of crystalline silicon works to weaken the electronic interaction between the two. Therefore, there is a demand for polysilane that is directly bonded to the surface of crystalline silicon without interposing the oxide film. Furthermore, when developing a molecular device using a single molecule of polysilane, it is a very important technique to bond the polysilane, preferably at both ends, to an electrode such as doped crystalline silicon. , The realization was desired.

[0008]

As described above, the chemical bonding of polysilane to the surface of crystalline silicon at the main chain end thereof is to provide a new and useful group of silicon skeleton materials, but it has been realized. I didn't.

In view of the above, according to the present invention, at least one end of the main chain that controls the conductivity of polysilane is bonded to the surface of crystalline silicon, which is a semiconductor whose conductivity can be controlled in a wide range, through only a short methylene chain. The purpose is to provide. Another object is to provide a method for producing polysilane chemically bonded to the surface of the crystalline silicon.

[0010]

In the polysilane chemically bonded to the surface of crystalline silicon of the present invention, at least one end of the main chain is chemically bonded to the surface of crystalline silicon through an alkyl chain.

Preferably, the polysilane bonded to the crystalline silicon surface of the present invention has the following formula:

[0012]

[Chemical 5]

[Wherein R ₁ , R ₂ , R ₃ , R ₄ , and R ₅ are each independently an organic group, n is an integer of 2 or more, and m is an integer of 1 or more], or The following formula

[0014]

[Chemical 6]

[Wherein R ₁ , R ₂ , R ₃ and R ₄ each independently represent an organic group, l and n represent an integer of 2 or more, and m represents an integer of 1 or more].

Further, in the crystalline silicon-polysilane conjugate comprising the crystalline silicon of the present invention and polysilane chemically bonded to the surface of the crystalline silicon, the polysilane is chemically bonded to the surface of the crystalline silicon at least one end of the main chain through the alkyl chain. It is combined.

Here, the preferred crystalline silicon of the present invention is
The polysilane conjugate has the following formula

[0018]

[Chemical 7]

[Wherein R ₁ , R ₂ , R ₃ , R ₄ , and R ₅ are each independently an organic group, n is an integer of 2 or more, and m is an integer of 1 or more], or Or the following formula

[0020]

[Chemical 8]

[Wherein, R ₁ , R ₂ , R ₃ and R ₄ are each independently an organic group, l and n are integers of 2 or more, and m is an integer of 1 or more].

Further, the method for producing polysilane chemically bonded to the surface of the crystalline silicon according to the present invention includes Si--H on the surface of the crystalline silicon and X (CH ₂ ) _n-2 CH = CH ₂ (wherein n
Is an integer of 2 or more, and X is a halogen) to form X (CH ₂ ) _n Si on the surface to produce surface-treated crystalline silicon, and the main chain is made of silicon. A step of producing a lithiated polysilane having a structure in which at least one end of the polysilane to be formed is lithiated, and the above-mentioned surface-treated crystalline silicon and the above-mentioned lithiated polysilane are reacted to form a main chain of the lithiated polysilane. The step of chemically bonding at least one end to the surface of the crystalline silicon.

Further, another method for producing polysilane chemically bonded to the surface of crystalline silicon is as follows.
And _{-H, X (CH 2) n} -2 CH = CH 2 ( wherein, n is an integer of 2 or more, X is halogen) and CH
X (CH ₂ ) _n Si and CH ₃ (CH ₂ ) _k Si are reacted with a mixture of ₃ (CH ₂ ) _k-2 CH═CH ₂ (wherein k is an integer of 2 or more). The step of producing a surface-treated crystalline silicon formed on the surface, the step of producing a lithiated polysilane having a structure in which at least one end of a polysilane whose main chain is composed of silicon is lithiated, and the above-mentioned surface-treated Reacting the crystalline silicon with the above-mentioned lithiated polysilane to chemically bond at least one end of the main chain of the lithiated polysilane to the surface of the crystalline silicon.

Here, the step of producing the lithiated polysilane in the above-mentioned two production methods can also be carried out by cleaving the silicon-silicon bond of the main chain of the polysilane polymer using a lithium reagent.

[0025]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below.

The polysilane of the present invention, which is a one-dimensional semiconductor chemically bonded to the surface of crystalline silicon at the main chain terminal, is represented by the following formula.

[0027]

[Chemical 9]

[Wherein R ₁ , R ₂ , R ₃ and R ₄ each independently represent an organic group, l and n represent an integer of 2 or more, and m represents an integer of 1 or more] Polysilane bonded to the crystalline silicon In order to facilitate the description, a method of manufacturing the will be described with reference to FIGS. 1 and 2 by taking the case of 1 = n as an example.

First, the production of polysilane in which one of the main chain ends is covalently bonded to a crystalline silicon substrate will be described. A reaction active point is created on the surface of the crystalline silicon substrate by using a chemical reaction. That is, S existing on the surface of the crystalline silicon substrate (1)
A surface-treated crystalline silicon substrate (3) is prepared by adding 1-alkene (2) having a halogen at the terminal to the i-H bond to halogenoalkylate the surface (FIG. 1).
(A)). Next, the lithiated polysilane (4), which has been made active by lithiating one end of the polysilane whose main chain is composed of silicon, is reacted with the halogenoalkylated crystalline silicon substrate (3). By this reaction, polysilane (6) in which one of the main chain ends is covalently bonded to crystalline silicon (6)
Is manufactured (FIG. 2A).

Next, the production of polysilane in which both ends of the main chain are covalently bonded to the crystalline silicon substrate will be described. Similar to the case where one of the main chain ends of the polysilane is bonded to the crystalline silicon substrate, the surface is halogenoalkylated to prepare a surface-treated crystalline silicon substrate (3) (FIG. 1).
(A)). Then, the lithiated polysilane (5), which is made reactive by lithiating both ends of the polysilane whose main chain is composed of silicon, is reacted with the halogenoalkylated crystalline silicon substrate (3). By this reaction, polysilane (7) having both ends of the main chain covalently bonded to crystalline silicon is produced (FIG. 2 (b)).

Here, as the surface-treated crystalline silicon substrate, a halogenoalkylated crystal from a mixed solution of a 1-alkene (2) having a halogen at a terminal and a 1-alkene (8) having no halogen at a terminal is used. A silicon substrate (9) may be used (FIG. 1 (b)). 1-alkene having a halogen at the terminal and 1-alkene having no halogen at the terminal
By changing the mixing ratio with the alkene, surface-treated crystalline silicon substrates having different reaction active point densities can be obtained.

The reaction active points on the surface of the crystalline silicon substrate shown in FIG. 1 (a) can be generated by the following method, for example. Usually, the surface of crystalline silicon is covered with an oxide film. It has been reported that by etching this in an aqueous solution of ammonium fluoride, the oxide film can be removed and the surface of the crystalline silicon substrate is terminated with Si—H [G. S. GS Higashi et al., Applied Physics Letters (Appl. Phys. Lett.), Volume 56, pp. 656 (1990)]. Si-H and 1-alkene CH ₃ (C on the surface of crystalline silicon terminated with hydrogen)
H ₂ ) _n C═CH ₂ is reported to efficiently add a carbon-carbon double bond of 1-alkene to Si—H by light irradiation [F. Effenbeer (F. Effenbe
rger), and Angewante Chemie International Edition in English (Angew. Che
m. Int. Ed. Engl.), 37, 2462 (19).
98)].

This reaction is applied to a ω-halogeno-1-alkene X (CH ₂ ) _n-2 C = H ₂ having a halogen at one end and a carbon-carbon double bond at the other end. By doing so, the reactive ω-halogenoalkyl group X (CH ₂ ) _n- can be chemically bonded to the surface of the crystalline silicon.

Further, instead of using only the terminal halogenated 1-alkene (2), a mixture of terminal halogenated 1-alkene (2) and non-halogenated 1-alkene (8) is used. By doing so, the density of reaction active points on the surface of the crystalline silicon substrate can be controlled (FIG. 1 (b)).

The polysilane (4) having one end lithiated can be prepared, for example, by "K. Sakamoto" et al., "The anionic polymerization method of masked disilene" reported as a novel polysilane synthesis method, Journal of. The
American Chemical Society (J. Am. Chem.
Soc.), Vol. 111, page 7641 (1989) ". That is, 1-phenyl-7,7,8,8-, which is a biphenyl cross-linked product of disilene having four organic groups (disilene masked with biphenyl).
Tetraalkyl-7,8-disilabicyclo [2.2.
2] Octa-2,5-diene is added to a tetrahydrofuran solvent in an atmosphere of an inert gas such as argon, and a catalytic amount of an organolithium reagent is added to initiate anionic polymerization, thereby rapidly producing a polysilane having a lithiated terminal. To do.

As another method, we have newly developed a method for synthesizing a polysilane having a terminal lithiated by cleaving a polysilane polymer with a lithium reagent. For example, in an atmosphere of an inert gas such as argon, a small amount of methyllithium is added to a tetrahydrofuran solution of poly (methylphenylsilane) to break the silicon-silicon bond in the main chain, thereby producing a polysilane having a lithiated terminal. . In the above-mentioned “anionic polymerization method of masked disilene”, only polysilane (4) having only one end lithiated was produced. However, when this method is used, polysilane having only one end lithiated is produced. (4)
In addition to that, polysilane (5) having both ends lithiated can be obtained at the same time.

Next, the surface of the crystalline silicon surface-treated by halogenoalkylation is immersed in a polysilane solution (4) in which one of these terminals is lithiated in an inert gas atmosphere such as argon. Polysilane (6) chemically bonded to the surface of the crystalline silicon via the group to obtain the polysilane (6) chemically bonded to the surface of the crystalline silicon of the present invention (FIG. 2A).

Similarly, polysilane (7) chemically bonded to the surface of crystalline silicon of the present invention is obtained from a polysilane solution (5) whose both ends are lithiated (FIG. 2 (b)).

Of course, polysilanes (4) and (5) whose main chain ends are lithiated are mixed, and polysilane having one of the main chain ends bonded and polysilane having both main chain ends bonded on the same crystalline silicon. Can also be manufactured.

1 and 2, the case where l = n, that is, the case where there is one kind of 1-alkene (2) having a halogen at the terminal has been described. However, when l ≠ n, that is, 1 having a halogen at the terminal In the case where there are two or more kinds of alkenes (2), polysilane bonded to crystalline silicon can be produced in the same manner.

Hereinafter, the present invention will be described in detail with reference to Examples, but the present invention is not limited to these Examples.

[0042]

EXAMPLES Example 1 In this example, three of R _{1 to} R _{4 in} (4) of FIG. 2A are methyl groups, one is an n-propyl group, and R ₅ is n-. 6 shows immobilization of poly (n-propyltrimethyldisilene), which is a butyl group, on the surface of crystalline silicon.

[1] The 11-bromide-1-undecyl group is bonded.
Preparation of combined crystalline silicon substrate 3 silicon (111) wafers cut into 10 mm square
It was immersed in 0% hydrogen peroxide: sulfuric acid = 1: 4 mixed acid for 30 minutes for cleaning, and further washed with pure water.
Then, this is further added with an ammonium fluoride aqueous solution (40
%) For 3 minutes, followed by washing with pure water to obtain a substrate (FIG. 1 (1)) having a silicon surface with the oxide film removed and terminated with hydrogen. This board is 1
1-bromide-1-undecene _{(Br (CH 2) 9 C} = C
H ₂ ) (Fig. 1 (2)) and was irradiated with a high pressure mercury lamp for 12 hours. Subsequently, the substrate was washed successively with tetrahydrofuran and acetone and air dried. Thus, a crystalline silicon substrate whose surface was halogenoalkylated (FIG. 1C) was obtained.

[2] Poly (n-propyltrimethyldisi)
Immobilization of poly (n-propyltrimethyldisilene) on the surface of crystalline silicon using a reactor 11 as shown in FIG. The reaction between (n-propyltrimethyldisilene) and the surface of the crystalline silicon substrate obtained in [1] was performed as follows.

The reaction device 11 comprises a reaction container (A) 12 and a reaction device (B) 13. The reaction vessel 12 is made of Pyrex (registered trademark) glass, has a glass stopper 14, and has two lines from the side wall. One is connected to the vacuum line and the other is connected to the reaction vessel 13. The reaction container 12 and the reaction container 13 are connected by a rotatable joint 15. The reaction vessel 13 is made of Pyrex glass and has a septum rubber stopper 16.
A magnetic stirrer 17 is provided inside.

First, the surface-treated substrate 18 obtained in [1] was placed in the reaction vessel 12, and 1-phenyl-7-n-propyl-7,8,8-trimethyl- was placed in the reaction vessel 13.
7,8-Disilabicyclo [2.2.2] octa-2,5
-Diene and 1-phenyl-8-n-propyl-7,
7,8-Trimethyl-7,8-disilabicyclo [2.
2.2] Octa-2,5-diene mixture (750 m
g) was added and the whole was evacuated. Then, the reaction vessel 13
Was cooled with liquid nitrogen, and dry tetrahydrofuran (8 mL) was introduced into the reaction vessel 13 through a vacuum line. After returning this to room temperature and dissolving the compound in the reaction vessel 13 with stirring to form a uniform solution,
Freezing and deaeration were repeated again to remove dissolved air, and then an argon atmosphere was created. Here, at room temperature, a hexane solution of n-butyllithium (1.54 mol / L, 0.1 mL)
Was added all at once and the polymerization was started by stirring,
A deep red tetrahydrofuran solution of lithiated poly (n-propyltrimethyldisilene) (FIG. 2 (4)) was prepared in the reaction vessel 13.

After 1 minute from the initiation of the polymerization, the solution in the reaction vessel 13 was poured into the reaction vessel 12 through the rotatable joint 15 without being exposed to the air, and the surface-treated substrate obtained with the lithiated polysilane and [1] was used. 18 surfaces were reacted. 1 minute after pouring the solution, the reaction vessel 1
A drop of ethanol was added to 2 to deactivate the lithiated polysilane that was present in a large excess. The obtained crystalline silicon substrate was washed by immersing it in toluene having a very strong dissolving power for polysilane for 16 hours or more. As a result, poly (n-propyltrimethylsilene) not chemically bonded to the substrate surface could be completely removed from the substrate.

Thus, poly (n-propyltrimethyldisilene) having one end chemically bonded to the surface of crystalline silicon (FIG. 2 (6)) was obtained.

FIG. 4 shows the emission spectrum of the obtained substrate. When the excitation wavelength was 325 nm, an emission spectrum having a peak at 345 nm was observed. This is the emission spectrum characteristic of poly (n-propyltrimethyldisilene). Therefore, it is shown that poly (n-propyltrimethyldisilene) having one end bonded is present on the surface of the crystalline silicon substrate.

Further, FIG. 5 shows the surface of the obtained crystalline silicon substrate observed by an atomic force microscope. Figure 5
Medium, diameter of approximately 20 observed uniformly on the surface of the silicon substrate
nm and a height of about 3 nm correspond to the poly (n-propyltrimethyldisilene) single chain, and polysilane could be confirmed on the substrate surface.

It should be noted that poly (n
The molecular weight distribution of -propyltrimethyldisilene) could be estimated by measuring the gel permeation chromatography of the polymer reprecipitated from ethanol. Number average molecular weight M _n = 3200 in terms of polystyrene
0, weight average molecular weight M _w = 48,000, dispersity M _w / M _n
Was 1.5.

[Examples 2 to 4] The immobilization of poly (di-n-hexylsilane) at one end and both ends using silicon substrates having different active site densities is shown.

[1] Crystal lines having different active site densities
Preparation of Recon Substrate In the same manner as in [1] of Example 1, a substrate having a silicon surface with an oxide film removed and terminated with hydrogen (FIG. 1 (1)).
Was obtained. Each of these substrates was immersed in a mixed solvent of 11-bromide-1-undecene (Fig. 1 (2)) and 1-dodecene (Fig. 1 (8)) of various mixing ratios, and a high pressure mercury lamp was used for 12 hours. Irradiated. Where 11-bromide-1
-The mixing ratio of undecene and 1-dodecene is 100: 0.
(Reactive active point density 100%) crystalline silicon substrate (Fig. 1
Example 3 is for (3)) and a crystalline silicon substrate of 10:90 (reaction active point density 10%) (FIG. 1).
Example 3 was for (9)), and Example 3 was for a crystalline silicon substrate of 1:99 (reaction active point density 1%) (FIG. 1 (9)). Subsequently, these substrates were sequentially washed with tetrahydrofuran and acetone and air dried. In this way, surface-treated substrates having different density of reactive sites were obtained.

[2] Di-t-butylbiphenyllithium
Preparation of a cylindrical flask equipped with a magnetic stir bar and connected to a vacuum line was charged with 50 mg of di-t-butylbiphenyl and 1 mg of lithium metal, and the whole was evacuated. Next, this cylindrical flask was cooled with liquid nitrogen, and 3 mL of dry tetrahydrofuran was introduced into the cylindrical flask through a vacuum line. Freezing and degassing were repeated twice to remove dissolved oxygen, and then the whole was placed in an argon atmosphere. This was stirred while maintaining it at 0 ° C., and reaction between metallic lithium and di-t-butylbiphenyl was performed. In this way, di-t-butylbiphenyllithium was obtained as a dark green tetrahydrofuran solution.

[3] of poly (di-n-hexylsilane)
Immobilization on the surface of crystalline silicon A reactor 11 was used to immobilize poly (di-n-hexylsilane) on the surface of crystalline silicon.

The surface-treated substrate 18 obtained in [1] is placed in the reaction vessel 12, and poly (di-n-
Hexylsilane) (M _n = 523000, M _w = 2520)
000, polystyrene standard) 50 mg was put and the whole was evacuated. Then, the reaction vessel 13 was cooled with liquid nitrogen, and dried tetrahydrofuran 10 m through a vacuum line.
L was introduced into the reaction vessel 13. This is returned to room temperature, and the compound in the reaction vessel 13 is stirred to dissolve poly (di-n-hexylsilane) to form a uniform solution,
Freezing and deaeration were repeated again to remove dissolved air, and then an argon atmosphere was created. The catalyst di-prepared in [2]
A few drops of a tetrahydrofuran solution of t-butylbiphenyllithium was added, and the silicon-silicon bond in the main chain of poly (di-n-hexylsilane) was cleaved while stirring to prepare a lithiated polysilane.

Here, while the lithiated polysilane obtained by living anionic polymerization described in Example 1 is reactive because only one of the main chain ends is lithiated, it is obtained in Examples 2-4. Since the lithiated polysilane contains the possibility that the raw material is cleaved and lithiated at multiple points of one molecule of the polysilane, it is possible to obtain a polysilane in which one and both ends of the main chain are lithiated.

As soon as the solution in the reaction vessel 13 became yellowish and formation of the lithiated polysilane was confirmed, it was immediately poured into the reaction vessel 12 through the rotatable joint 15 without exposure to air, and the lithiated polysilane and [1] were added. The prepared substrate surface of each active concentration was reacted. Three minutes after the completion of pouring the solution, one drop of n-butanol was added to the reaction vessel 12 to deactivate the lithiated polysilane that was present in a large excess. The crystalline silicon substrate was washed by immersing it in isooctane, which has a very strong dissolving power for poly (di-n-hexylsilane), at 40 ° C. for 16 hours or more. As a result, the polysilane that was not chemically bonded to the substrate surface could be completely removed from the substrate.

In this manner, poly (di-n-hexylsilane) having its one end and both ends chemically bonded to the surface of crystalline silicon was obtained.

Confirmed by an atomic force microscope in FIG.
The polysilane bonded to the surface of the obtained crystalline silicon substrate is shown. FIG. 6A is a second embodiment, FIG. 6B is a third embodiment,
And FIG. 6 (c) shows the surface of the crystalline silicon substrate obtained in Example 4. As can be seen from FIG. 6, the density of the spot-like image with a radius of 100 nm and a height of 1 nm, which is uniformly observed on the surface of the silicon substrate, changes corresponding to the reaction active point density. This indicates that the density of polysilane bonded to the surface of crystalline silicon can be controlled by controlling the reaction activity density of the substrate used.

The molecular weight distribution of poly (di-n-hexylsilane) chemically bonded to the surface of the substrate can be estimated by measuring the gel permeation chromatography of the tetrahydrofuran solution at the end of the reaction. At the end of the reaction, poly (di-n-hexylsilane) had a number average molecular weight _{Mn of} 96000, a weight average molecular weight _{Mw of} 629000, and a dispersion _Mw / _{Mn of} 6.55 in terms of polystyrene.

[Examples 5 and 6] The immobilization of poly [n-decyl {(S) -2-methylbutyl} silane] at one end and both ends thereof using tetrahydrofuran solutions of lithiated polysilane having different concentrations is shown. . Further, in order to analyze the ultraviolet-visible absorption spectrum of the polysilane bonded to the substrate, a quartz substrate was used instead of the crystalline silicon substrate (Reference Examples 1 and 2) as a reference example.

[1] 11-Undecyldimethylsilyl bromide
Production of Crystalline Silicon Substrate with Rubbed Surface In the same manner as in Example 2, a silicon substrate having a 11-undecyldimethylsilyl bromide-treated surface (FIG. 1 (3)) was produced.

[2] 11-Undecyldimethylsilyl bromide
Preparation of Quartz Substrate with Roughened Surface 3 pieces of quartz substrate (length 18 mm, width 25 mm, thickness 1 mm)
It was dipped in 0% hydrogen peroxide: sulfuric acid = 1: 4 mixed acid for 12 hours and further washed with pure water. Then at 110 ° C for 2
Allowed to dry for hours. This was made into a mixed solution of 11-undecyldimethylchlorosilane (1 mL) and tetrahydrofuran (20 mL) under an argon atmosphere, and the above substrate was immersed in this and heated under reflux for 2 hours, and then washed with tetrahydrofuran and then acetone. After that, air-dry and the surface 11-
A quartz substrate undecyldimethylsilyl bromide was obtained.

[3] Poly [n-decyl {(S) -2-me
[Cyl-butyl} silane] crystal silicon surface and quartz surface
Immobilization on Surface A reactor 11 was used for immobilization of poly [n-decyl {(S) -2-methylbutyl} silane] on the surface of crystalline silicon and the surface of quartz. The surface-treated crystalline silicon obtained in [1] and the surface-treated quartz substrate obtained in [2] were placed in the reaction vessel 12, and the whole was evacuated.

In Example 5 (crystalline silicon substrate) and Reference Example 1 (quartz substrate), poly [n-decyl {(S) -2-methylbutyl} silane] (M _n = 15) was placed in the reaction vessel 13.
20000, _Mw = 7770000, _Mw / _Mn = 5.1
2, polystyrene standard) in isooctane (5 g /
2 mL of L) was injected. Then, the reaction vessel 13 was cooled with liquid nitrogen, and dry tetrahydrofuran (8 mL) was introduced into the reaction vessel 13 through a vacuum line. This was returned to room temperature, the compound in the reaction vessel 13 was dissolved with stirring to form a uniform solution, and freeze deaeration was repeated again to remove dissolved air, and then an argon atmosphere was created. To this, 50 μL of a tetrahydrofuran solution of di-t-butylbiphenyllithium prepared in Example 2 [2] was added all at once, and poly [n-decyl {(S)-was added while stirring.
2-Methylbutyl} silane] was cleaved at the silicon-silicon bond to prepare a lithiated lithiated polysilane.

As soon as the solution in the reaction vessel 13 became yellowish and formation of the lithiated polysilane was confirmed, it was immediately poured into the reaction vessel 12 through the rotatable joint 15 without being exposed to air, and the lithiated polysilane and [1] were added. The surface-treated crystalline silicon substrate surface obtained in [2] and the surface-treated quartz substrate surface obtained in [2] were reacted. 3 minutes after pouring the solution, the reaction container 12
One drop of n-butanol was added to deactivate the lithiated polysilane which was present in a large excess. Cleaning was performed by immersing the crystalline silicon substrate and the quartz substrate in isooctane, which has a very strong dissolving power for poly [n-decyl {(S) -2-methylbutyl} silane], for 16 hours or more.
As a result, polysilane that is not chemically bonded to the substrate surface can be completely removed from the substrate.

In this way, poly [n-decyl {(S) -2-methylbutyl} silane (Example 5) having one end and both ends chemically bonded to the surface of crystalline silicon was prepared.
Poly [n-decyl {(S) -2-methylbutyl} silane (Reference Example 1) was obtained by chemically bonding one end and both ends to a quartz surface.

Among the above-mentioned operations, in Example 6 (crystalline silicon substrate) and Reference Example 2 (quartz substrate), the reaction vessel 1 was used.
A solution of poly [n-decyl {(S) -2-methylbutyl} silane] in isooctane (5 g / L) was added to 0.3%.
The volume was reduced to 2 mL, and dried tetrahydrofuran (9.
8 mL) was introduced by vacuum transfer, and the amount of the tetrahydrofuran solution of di-t-butylbiphenyllithium used in the reaction to obtain lithiated polysilane was adjusted to 5 μL, which was 1/10 of that in Example 5, to carry out the lithiated polysilane concentration. It was set to 1/10 equivalent of Example 5. Other operations are performed in the same manner as in Example 5, and poly [n-decyl {(S) -2-methylbutyl} silane (Example 6) having one end and both ends chemically bonded to the surface of the crystalline silicon,
Poly [n-decyl {(S) -2-methylbutyl} silane (Reference Example 2) having one and both ends chemically bonded to the surface of quartz was obtained.

By measuring the ultraviolet-visible absorption spectra of the obtained quartz substrates (Reference Examples 1 and 2), poly [n-decyl {(S) chemically bonded to the surface of the crystalline silicon substrate corresponding to each quartz substrate was obtained. -2-methylbutyl}
The relative amount of [silane] can be estimated.

FIG. 7 shows an ultraviolet-visible absorption spectrum of the obtained quartz substrate. A very sharp peak characteristic of poly [n-decyl {(S) -2-methylbutyl} silane] was observed, which confirms the presence of chemically bonded polysilane on the quartz substrate surface. Since the absorption intensity is proportional to the absolute amount of polysilane to be measured, the total amount of polysilane can be obtained from the absorption peak intensity.
In this case, on the substrate of Reference Example 1 corresponding to Example 5,
It is shown that about 10 times more polysilane than the polysilane on the substrate of Reference Example 2 corresponding to Example 6 is chemically bonded.

From this, it was considered that about 10 times as much polysilane as the polysilane on the crystalline silicon substrate of Example 6 was chemically bonded onto the crystalline silicon substrate of Example 5.

Confirmed by an atomic force microscope in FIG.
The polysilane chemically bonded to the surface of the crystalline silicon substrate obtained in Examples 5 and 6 is shown. 8A shows the polysilane on the surface of the crystalline silicon substrate obtained in Example 5, and FIG. 8B shows the polysilane on the surface of the crystalline silicon substrate obtained in Example 6. In FIG. 8, a string-like image having a height of about 1 nm, which is uniformly observed on the surface of the crystalline silicon substrate, corresponds to the poly [n-decyl {(S) -2-methylbutyl} silane] single chain. The density of the string-like image changes depending on the concentration of lithiated polysilane used in the reaction. This indicates that by controlling the concentration of lithiated polysilane used in the reaction, the density of polysilane bonded to the surface of crystalline silicon can be controlled.

[0074]

As described above, the polysilane of the present invention is chemically bonded to the surface of crystalline silicon at one or both ends of the main chain via only short methylene chains. Since the semiconductor properties of polysilane are mainly borne by the main chain, electronic interaction occurs with the crystalline silicon substrate. Construction of a new silicon composite device is expected by the present invention.

Further, according to the present invention, polysilane can be taken out as a single molecule. Polysilane can have various side chains, and the rigidity of the main chain is widely changed by their steric effects, which is a characteristic not found in other semiconductor polymers. Therefore, the polysilane of the present invention can be used as a single molecular element and a molecular conducting wire in future molecular element construction.

[Brief description of drawings]

FIG. 1 is a schematic view showing a manufacturing process of a halogenoalkylated crystalline silicon substrate in the reaction process of the present invention, FIG.
FIG. 3B is a diagram illustrating a manufacturing process of a crystalline silicon substrate that is wholly halogenoalkylated, and FIG. 7B is a diagram illustrating a manufacturing process of a crystalline silicon substrate that is partially halogenoalkylated.

FIG. 2 is a diagram showing a reaction between a halogenoalkylated crystalline silicon substrate surface and a lithiated polysilane having a structure in which at least one of main chain ends is lithiated in the reaction process of the present invention, and (a) is a main diagram. In the case of a lithiated polysilane having a structure in which one of the chain ends is lithiated, (b)
FIG. 3 is a diagram showing a case of lithiated polysilane having a structure in which both main chain terminals are lithiated.

FIG. 3 is a diagram showing a reactor used for synthesizing polysilane in which one end or both ends of a main chain is chemically bonded to the surface of crystalline silicon.

FIG. 4 is a diagram showing an emission spectrum (excitation light wavelength = 325 nm) of a crystalline silicon substrate in which poly (n-propyltrimethyldisilene) prepared in Example 1 is chemically bonded to the surface at one end of the main chain. .

FIG. 5 is a diagram showing an atomic force micrograph of a crystalline silicon substrate having poly (n-propyltrimethyldisilene) prepared in Example 1 chemically bonded to the surface at one end of the main chain.

6 (a) is a second embodiment, and FIG. 6 (b) is a third embodiment.
2C is a diagram showing an atomic force micrograph of a crystalline silicon substrate having poly (di-n-hexylsilane) prepared in Example 4 chemically bonded to the surface at one or both ends of the main chain. is there.

FIG. 7 shows poly [n produced in Reference Examples 1 and 2;
FIG. 3 is a diagram showing an ultraviolet-visible absorption spectrum of a quartz substrate in which -decyl {(S) -2-methylbutyl} silane] is chemically bonded to the surface at one or both ends of the main chain.

8A is a fifth embodiment, and FIG. 8B is a sixth embodiment.
Poly [n-decyl {(S)
2-methylbutyl} silane] is a diagram showing an atomic force micrograph of a crystalline silicon substrate chemically bonded to the surface at one or both ends of the main chain.

[Explanation of symbols]

11 reactor 12, 13 Reaction vessel 14 Glass stopper 15 Rotatable joint 16 Septum rubber stopper 17 Magnetic stirrer 18 Surface-treated substrate

─────────────────────────────────────────────────── ─── Continuation of front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) C08G 77/00-77/62

Claims (9)

(57) [Claims] 1. A polysilane chemically bonded to the surface of crystalline silicon, wherein the polysilane chemically bonds at least one end of a main chain to the surface of crystalline silicon through an alkyl chain. 2. The polysilane according to claim 1, wherein the polysilane is represented by the following formula. [Chemical 1] [In the formula, R ₁ , R ₂ , R ₃ , R ₄ , and R ₅ are each independently an organic group, n is an integer of 2 or more, and m is an integer of 1 or more] 3. The polysilane according to claim 1, wherein the polysilane is represented by the following formula. [Chemical 2] [Wherein R ₁ , R ₂ , R ₃ and R ₄ are each independently an organic group,
l and n are integers of 2 or more, m is an integer of 1 or more] 4. A crystalline silicon-polysilane conjugate comprising crystalline silicon and polysilane chemically bonded to the crystalline silicon surface, wherein the polysilane chemically bonds at least one end of a main chain to the crystalline silicon surface via an alkyl chain. A crystalline silicon-polysilane conjugate characterized by being bonded. 5. The crystalline silicon-polysilane bond according to claim 4, which is represented by the following formula. [Chemical 3] [In the formula, R ₁ , R ₂ , R ₃ , R ₄ , and R ₅ are each independently an organic group, n is an integer of 2 or more, and m is an integer of 1 or more] 6. The crystalline silicon-polysilane bond according to claim 4, which is represented by the following formula. [Chemical 4] [Wherein R ₁ , R ₂ , R ₃ and R ₄ are each independently an organic group,
l and n are integers of 2 or more, m is an integer of 1 or more] 7. A method for producing polysilane chemically bonded to the surface of crystalline silicon, comprising: Si—H on the surface of crystalline silicon; and X (CH ₂ ) _n-2 CH.
= CH ₂ (wherein n is an integer of 2 or more and X is halogen) to form X (CH ₂ ) _n Si on the surface to produce surface-treated crystalline silicon. A step, a step of producing a lithiated polysilane having a structure in which at least one end of a polysilane whose main chain is composed of silicon is lithiated, the surface-treated crystalline silicon, and the lithiated polysilane are reacted, And a step of chemically bonding at least one end of a main chain of lithiated polysilane to the surface of crystalline silicon, the method for producing polysilane chemically bonded to the surface of crystalline silicon. 8. A method for producing polysilane chemically bonded to the surface of crystalline silicon, comprising: Si—H on the surface of crystalline silicon and X (CH ₂ ) _n-2 CH.
= CH ₂ (wherein n is an integer of 2 or more and X is a halogen) and CH ₃ (CH ₂ ) _k-2 CH = CH ₂ (wherein k is an integer of 2 or more) A step of reacting with a mixture to form X (CH ₂ ) _n Si and CH ₃ (CH ₂ ) _k Si on the surface to produce surface-treated crystalline silicon; and a polysilane whose main chain is composed of silicon. A step of producing a lithiated polysilane having a structure in which at least one end thereof is lithiated, the surface-treated crystalline silicon is reacted with the lithiated polysilane, and at least one end of a main chain of the lithiated polysilane is crystalline silicon And a step of chemically bonding to the surface, the method for producing polysilane chemically bonded to the surface of crystalline silicon. 9. The method according to claim 7, wherein the step of producing the lithiated polysilane is performed by cleaving the silicon-silicon bond of the main chain of the polysilane polymer using a lithium reagent. The method for producing a polysilane according to 1.