JP2004292222A - Method for producing silicon carbide nanowire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a simple method for producing a silicon carbide (SiC) nanowire whose length and diameter are large. <P>SOLUTION: Chlorosilane with a carrier gas is heated to 900-1,300°C under reduced pressure of 1-100 Torr. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The invention of this application relates to a method for producing a silicon carbide (SiC) nanowire useful as a device for information communication such as a semiconductor, a photonic material, a member for a nanomachine, or the like.
[0002]
[Prior art and its problems]
Conventionally, as a method for producing silicon carbide nanowires, a plasma method in which hydrogen and hydrocarbon are reacted in plasma, and a method in which carbon (C) and silicon dioxide (SiO ₂ ) are reacted (Reference 1) have been studied. ing.
[0003]
However, each of the silicon carbide (SiC) nanowires produced by the conventionally known methods has a short length, a small diameter, and requires the use of two or more kinds of reactants. Was.
[0004]
[Literature]
Reference 1: H. Dai, E .; W. Wong, Y .; Z. Lu, S.M. Fan, M .; Liebr, Synthesis and Characterization of Carrier nanorods, Nature, 375, 29 (1995) 769-772.
[0005]
Therefore, the invention of this application solves the conventional problems as described above, and provides a new method capable of manufacturing a long, large-diameter silicon carbide (SiC) nanowire by a simple method, It is an object to provide a silicon carbide nanowire obtained by this method.
[0006]
[Means for Solving the Problems]
In order to solve the above-mentioned problems, the invention of this application firstly heats chlorosilane to a temperature range of 900 ° C. or more and 1300 ° C. or less in a carrier gas stream under a reduced pressure atmosphere of 1 to 100 Torr. The second is a method for producing a silicon carbide nanowire, which is heated under a reduced-pressure atmosphere in the range of 1 to 10 Torr. Fourth, a method for producing a silicon carbide nanowire that is at least one of hydrogen and an inert gas is described. Fourth, chlorosilane is represented by the formula: R _n SiCl _4-n (R represents a hydrocarbon group, and n represents 0 And the fifth is a method for producing silicon carbide nanowires, which is one or more of the compounds represented by the following formulas. The present invention provides a method for producing silicon carbide nanowires having a flow rate of 50 to 500 and a flow rate of 1 to 2000 cc / min.
[0007]
The invention of this application sixthly provides a β-type silicon carbide nanowire, and seventhly, a silicon carbide nanowire having a length of 1 μm to 100 μm and a diameter of 10 nm to 300 nm. provide.
[0008]
As described above, in the invention of this application, a method of forming a silicon carbide (SiC) film by thermally decomposing chlorosilane has been known, but silicon carbide (SiC) having a characteristic under a specific environmental condition is known. It has been completed based on a completely unexpected new finding obtained by the inventor that nanowires are generated.
[0009]
That is, silicon carbide (SiC) nanowires are formed on a substrate by thermally decomposing chlorosilanes such as methylchlorosilane and ethylchlorosilane in a temperature range of 900 ° C. to 1300 ° C. in a reduced-pressure atmosphere of 100 Torr or less, preferably 10 Torr or less. In addition, silicon carbide (SiC) nanowires having a length of several μm and a diameter of 40 nm to 300 nm have been realized, and based on the knowledge that they are β-type silicon carbide (SiC) nanowires. I have.
[0010]
BEST MODE FOR CARRYING OUT THE INVENTION
The invention of this application has the features as described above, and embodiments thereof will be described below.
[0011]
In the method for producing silicon carbide nanowires according to the invention of the present application, as described above, chlorosilane gas is thermally decomposed at a temperature of 900 ° C. or more and 1300 ° C. or less under a reduced pressure atmosphere of 1 to 100 Torr, more preferably 1 to 10 Torr. In this case, the chlorosilane gas is preferably subjected to a thermal decomposition reaction under the flow of a carrier gas. As such a carrier gas, various gases may be used as long as the carrier gas is inert or has a reaction promoting property. For example, a rare gas such as argon and helium, a hydrogen gas, or a mixed gas thereof is preferable. As an example.
[0012]
Even when a carrier gas is used, the degree of pressure reduction in the reaction system needs to be within the above range.
[0013]
As a reaction raw material, a compound gas called chlorosilane is used, which can be basically considered as one kind of reaction raw material, and a plurality of kinds of essentially different materials as in the prior art are used. Is clearly distinguished from the method using.
[0014]
Chlorosilane is represented by the general formula as described above, and specific examples of the hydrocarbon group denoted by R are lower alkyl groups such as methyl, ethyl and propyl.
[0015]
For example, trichloromethylsilane, trichloroethylsilane, dichlorodimethylsilane, chlorotrimethylsilane, and the like.
[0016]
When the method of the invention of this application is carried out as a reaction of a carrier gas flow system, for example, a system as shown in FIG. 1 can be configured.
[0017]
That is, the pressure in the reaction vessel (1) provided with the substrate (11) made of, for example, silicon carbide (SiC) or silicon (Si) is reduced to about 1 × 10 ⁻³ Torr. Then, after heating the temperature to 1100 to 1300 ° C, the valve (4) on the vacuum pump (8) side is operated to adjust the pressure in the reaction system to a reduced pressure of 100 Torr or less.
[0018]
Then, the chlorosilane (10) is introduced into the reaction vessel (1) while bubbling the hydrogen gas (3) into the chlorosilane (10) solution. At this time, the volume ratio of the chlorosilane (10) to the hydrogen gas (3) is preferably in the range of 1:50 to 500, more preferably in the range of 1: 100 to 300, and the flow rate is 1 The valve (4) is adjusted so as to be 2000 cc / min while watching the pressure gauge (6) and the flow meter (5).
[0019]
If heating is continued at 900 ° C. or higher and 1300 ° C. or lower in this state, silicon carbide (SiC) nanowires are generated on the surface of the substrate (11) in the reaction vessel (1). At this time, excess hydrogen gas (3) used for transferring the chlorosilane (10) and by-products generated by the decomposition of the chlorosilane (10) are sucked together with the argon gas (2) and collected in the trap (12). Is done.
[0020]
For example, in the method of the present invention which can be constituted as the above-mentioned reaction system, generally, when the volume ratio of chlorosilane to the carrier gas increases, the diameter of the silicon carbide (SiC) nanowire increases, and When the heating temperature is lower than 1100 ° C., the length of the silicon carbide (SiC) nanowire becomes shorter. When the heating temperature is lower than 900 ° C., it is difficult to generate silicon carbide (SiC) itself. On the other hand, when the heating temperature is higher than 1300 ° C., the amount of the generated silicon carbide (SiC) nanowires decreases, and most of the silicon carbide (SiC) ) It becomes a film.
[0021]
The invention of this application uses inexpensive chlorosilane, and furthermore, produces silicon carbide (SiC) nanowires by a simple method of heating this chlorosilane in combination with a carrier gas such as hydrogen gas or argon gas. Can be. In the invention of this application, the length of the silicon carbide (SiC) nanowire is controlled in the range of 1 μm to 100 μm and the diameter thereof is controlled in the range of 10 nm to 300 nm by adjusting the reaction conditions. It has the feature that it can be. It has also been confirmed that silicon carbide (SiC) nanowires produced by this method are of the β type.
[0022]
Therefore, an embodiment will be shown below and will be described in more detail. Of course, the invention is not limited by the following examples.
[0023]
【Example】
<Example 1>
In the reaction system illustrated in FIG. 1, the reaction vessel (1) in which the silicon substrate is disposed is evacuated to 1 × ⁻³ Torr. After heating to 1200 ° C., hydrogen gas is bubbled into a 99% pure trichloromethylsilane (CH ₃ SiCl ₃ ) solution and introduced into the reaction vessel. At that time, the pulp and the flow meter are adjusted so that the ratio of trichloromethylsilane to hydrogen gas is 1: 200 and the flow rate is 1000 cc / min. The temperature inside the reaction vessel (1) was heated to 1100 ° C. while maintaining the pressure inside the reaction vessel at 10 Torr by operating a valve on the vacuum pump side. Silicon carbide (SiC) nanowires were generated on a silicon substrate.
[0024]
FIG. 2 is a scanning electron micrograph of a silicon carbide (SiC) nanowire formed at a temperature of 1100 ° C. FIG. 3 is a transmission electron microscope photograph, and FIG. 4 is an enlarged photograph thereof. FIG. 5 is an electron diffraction image. From these results, the generated silicon carbide (SiC) nanowires mainly have a length of about 100 μm at the maximum and a diameter of about 10 nm to 80 nm, and FIG. 5 shows that β has a growth direction of <111>. It was confirmed to be silicon carbide (SiC).
[0025]
Then, as a result of analyzing the generated silicon carbide (SiC) by energy dispersive X-ray spectroscopy (EDS), it was confirmed that the ratio of carbon (C) to silicon (Si) was almost 1: 1.
[0026]
<Example 2>
In Example 1, the volume ratio of trichloromethylsilane to hydrogen gas was set to 1: 100. When the ratio of trichloromethylsilane was doubled in this way, it was confirmed that the diameter of the generated silicon carbide (SiC) nanowires was increased to 300 nm.
[0027]
<Example 3>
In Example 1, the heating temperature was 960 ° C. It was confirmed that the length of the generated silicon carbide (SiC) nanowire was up to 30 μm, which was shorter.
[0028]
<Comparative example>
In Example 1, the heating temperature was 1350 ° C. In this case, it was confirmed that the number density of the nanowires decreased, and most of the nanowires became SiC films.
[0029]
【The invention's effect】
As described in detail above, according to the invention of this application, it is possible to manufacture longer and larger-diameter silicon carbide (SiC) nanowires by using inexpensive chlorosilane and thermally decomposing it. In addition, a silicon carbide nanowire characterized by being β-type SiC grown in the <111> direction is provided as the nanowire.
[Brief description of the drawings]
FIG. 1 is a diagram illustrating a system of a reaction system.
FIG. 2 is a scanning electron micrograph of a silicon carbide nanowire.
FIG. 3 is a transmission electron micrograph of a silicon carbide nanowire.
FIG. 4 is an enlarged photograph of a silicon carbide nanowire with a transmission electron microscope and an electron diffraction image of the silicon carbide nanowire.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Reaction container 2 Argon gas 3 Hydrogen gas 4 Valve 5 Flowmeter 6 Pressure gauge 7 Cooling water 8 Vacuum pump 9 Heating control device 10 Chlorosilane 11 Substrate 12 Trap

Claims (7)

A method for producing silicon carbide nanowires, comprising heating chlorosilane to a temperature range of 900 ° C. to 1300 ° C. in a carrier gas stream under a reduced pressure atmosphere of 1 to 100 Torr. The method for producing a silicon carbide nanowire according to claim 1, wherein the heating is performed under a reduced pressure atmosphere in a range of 1 to 10 Torr. 3. The method for producing silicon carbide nanowires according to claim 1, wherein the carrier gas is at least one of hydrogen and an inert gas. Chlorosilane formula: R _n SiCl _4-n (the _R represents a hydrocarbon radical, n is an integer of 0 to 3) of claims 1 to 3, characterized in that at least one compound represented by A method for producing any of the silicon carbide nanowires. The method for producing silicon carbide nanowires according to any one of claims 1 to 4, wherein the flow rates of the chlorosilane and the carrier gas are in the range of 1:50 to 500, and the flow rate is 1 to 2000 cc / min. Silicon carbide nanowires characterized by being of beta type. The silicon carbide nanowire according to claim 6, wherein the length is in a range of 1 m to 100 m and the diameter is in a range of 10 nm to 300 nm.

Images