JP5170609B2 - Method for producing silicon carbide nanowire - Google Patents

Description

  The present invention relates to a method for producing silicon carbide nanowires having a bamboo-like morphology with excellent semiconductor characteristics and field electron emission characteristics at high temperatures.

  Silicon carbide is a semiconductor material having a wide band gap energy that can maintain high thermal conductivity and hardness even at high temperatures. As a one-dimensional silicon carbide nanostructure, for example, Non-Patent Document 1 reports nanowires.

  Non-Patent Documents 2 and 3 report nanorods. Nanotubes are reported in Non-Patent Document 4 and the like. Non-patent documents 5 to 7 report nanocables, and further, hollow spherical nanoparticles (see, for example, non-patent document 8) and nanoboxes (see, for example, non-patent document 9) are known. ing.

Z. W. Pan et al., Adv. Mater. Vol. 12, 1186, 2000 H. J. Dai et al., Nature 375, 769, 1995 X. T. Zhou et al., Chem. Phys. Lett. 318, 58, 2000 X. H. Sun et al., J. Am. Chem. Soc. 124, 14464, 2002 C. C. Tang et al., Adv. Mater. 14, 1046, 2002 Y. B. Li et al., Adv. Mater. 17, 545, 2005 Y. B. Li et al., Adv. Mater. 16, 93, 2004 G. Z. Shen et al., Chem. Phys. Lett. 375, 177, 2003 C. H. Wang et al., Adv. Mater. 17, 419, 2005

  As described above, various nanowires, nanotubes, nanorods, nanocables, nanoboxes, and the like are known, but to date, cubic silicon carbide nanowires having a bamboo-like form have not been obtained.

  In view of the above problems, an object of the present invention is to provide a novel method for producing cubic silicon carbide nanowires having excellent semiconductor characteristics and field electron emission characteristics at high temperatures and having a bamboo-like form.

In order to achieve the above object, the present invention synthesizes silicon carbide nanowires by heating a mixture of silicon monoxide powder, graphite powder and gallium nitride powder in an inert gas stream at a predetermined temperature for a predetermined time. Features.
In the above configuration, the molar ratio between the silicon monoxide powder and the graphite powder is preferably in the range of 1: 0.5 to 1: 0.6. In this case, it is more preferable that the gallium nitride powder is in the range of 0.02 to 0.07 mol with respect to 1 mol of the silicon monoxide powder.
The heating temperature is preferably in the range of 1300 to 1400 ° C., and the heating time at this time is preferably in the range of 40 minutes to 2 hours.
The inert gas is preferably argon gas, and the flow rate of the inert gas is preferably in the range of 150 to 400 sccm.
According to the above configuration, silicon carbide nanowires having a diameter of 80 to 300 nm and a length of several hundreds of μm dark green can be produced.

  ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method of the silicon carbide nanowire which has a cubic crystal structure of the bamboo-like form which has a trunk | trunk and a node thicker than it can be provided.

Hereinafter, preferred embodiments of the method for producing silicon carbide nanowires of the present invention will be described in detail.
First, a mixture of silicon monoxide powder, graphite powder and gallium nitride powder is placed in a graphite vessel, and this vessel is placed in the center of a vertical high-frequency induction heating furnace.
Next, after depressurizing the inside of the heating furnace, an inert gas is flowed, and the contents of the container are heated in the inert gas stream, whereby silicon carbide nanowires can be synthesized.

  Among the raw material powders, the molar ratio of the silicon monoxide powder and the graphite powder is preferably in the range of 1: 0.5 to 1: 0.6. When the molar ratio of the silicon monoxide powder is larger than this range, silicon nanowires are obtained, and the intended silicon carbide nanowires cannot be obtained, which is not preferable. Conversely, if the molar ratio of the silicon monoxide powder is less than this range, a large amount of graphite powder remains in the heating furnace, which is not preferable.

  The gallium nitride powder is preferably in the range of 0.02 to 0.07 mol with respect to 1 mol of silicon monoxide powder. If the gallium nitride powder is more than 0.07 mol, metal gallium is present in the final product, which is not preferable. Conversely, when the gallium nitride powder is less than 0.02 mol, a silicon carbide nanorod having a larger diameter is obtained, and a silicon carbide nanowire cannot be obtained, which is not preferable.

  The heating temperature is preferably in the range of 1300 to 1400 ° C. A heating temperature higher than 1400 ° C. is not preferable because a thick nanorod having a diameter of approximately 1 μm can be obtained. Conversely, when the heating temperature is lower than 1300 ° C., silicon monoxide is not decomposed and silicon carbide nanowires cannot be obtained, which is not preferable.

  The heating time is preferably in the range of 40 minutes to 2 hours. Since the reaction is completed within 2 hours of heating, it is not necessary to spend more time. On the contrary, if the heating time is shorter than 40 minutes, the yield decreases, which is not preferable.

Argon gas etc. can be used as an inert gas. The flow rate is preferably in the range of 150 to 400 sccm (cm ³ / min). If the flow rate of the inert gas is higher than 400 sccm, the product will be scattered outside the reaction system, which is not preferable. On the other hand, if the flow rate of the inert gas is less than 150 sccm, the reactive vapor is not sufficiently transferred, so that silicon carbide nanowires cannot be obtained and become particulate matter, which is not preferable.

  By performing the above operation, a dark green wool-like substance having a diameter of 80 to 300 nm and a length of several hundreds of μm is deposited on the reaction tube in the furnace.

Next, an Example is shown and this invention is demonstrated further more concretely.
First, 0.8 g of silicon monoxide powder (manufactured by Wako Pure Chemical Industries, Ltd., purity 99.9%), 0.1 g of graphite powder (manufactured by Wako Pure Chemical Industries, Ltd., purity 98%), nitriding A mixture of 0.04 g of gallium powder (manufactured by Sigma-Aldrich, purity 99.99%) is placed in a graphite crucible, and the crucible is a vertical pipe having a graphite induction heating cylindrical tube covered with a carbon fiber as a heat insulating material. It was installed in the center of the type high frequency induction heating furnace.
Next, after the vertical high frequency induction heating furnace was depressurized to a pressure of 0.2 Torr (26.7 Pa), it was heated at 1350 ° C. for 1 hour while flowing argon gas at a flow rate of 200 sccm.
Finally, when the vertical high-frequency induction heating furnace was cooled to room temperature, 34.6 mg of dark green wool-like material was deposited on the portion of the heat insulating material that had been approximately 1250 ° C. during heating.

Next, the wool-like material synthesized in the examples will be described in more detail.
FIG. 1 is a diagram showing an X-ray diffraction image of the wool-like material synthesized in the example. In FIG. 1, the vertical axis represents the X-ray diffraction intensity (arbitrary scale), and the horizontal axis represents the angle (°), that is, an angle corresponding to twice the incident angle θ of the X-ray to the atomic plane.
As is clear from FIG. 1, the wool-like material synthesized in the example was found to be cubic silicon carbide (3C—SiC). In addition, the diffraction peak with weak intensity | strength shown by s in a figure is based on a stacking fault.

  FIG. 2 is a diagram showing a medium magnification scanning electron microscope image of the wool-like material synthesized in the example. As is clear from FIG. 2, the wool-like material obtained in the examples was found to be silicon carbide nanowires having an average diameter of 80 to 300 nm and a length of several hundred μm.

  FIG. 3 is a diagram showing a high-magnification scanning electron microscope image of the silicon carbide nanowire synthesized in the example. As apparent from FIG. 3, it was found that the silicon carbide nanowires synthesized in the examples were bamboo-like nanowires having periodic nodes. That is, the silicon carbide nanowire synthesized in the example is a nanowire composed of a trunk and a thicker node.

  FIG. 4 is a view showing a high-magnification scanning electron microscope image of a cross section of the silicon carbide nanowire synthesized in the example. As is clear from FIG. 4, it was found that the cross section of the silicon carbide nanowire synthesized in the example had a hexagonal shape.

FIG. 5 is a diagram showing the measurement results of the field electron emission characteristics of the silicon carbide nanowires synthesized in the example. In FIG. 5, the vertical axis indicates the current density (μA / cm ² ), and the horizontal axis indicates the applied DC voltage (V).
The distance between the silicon carbide nanowire sample and the anode was 100 μm, and the voltage was measured by applying a direct current of 0 to 1000V. The degree of vacuum at this time was about 5 × 10 ⁻⁷ Torr (6.7 × 10 ⁻⁵ Pa). Assuming that the voltage when the current density is 10 μA / cm ² is the starting voltage and the voltage when the current density is 10 mA / cm ² is the threshold voltage, the starting electric field strength (E _to ) at turn-on is 10.1 V / It was μm.
The inset in FIG. 5 is a Fowler-Nordheim plot and shows that the current-voltage characteristic is composed of two linear portions.

  The present invention is not limited to the above-described embodiments, and various modifications can be made within the scope of the invention described in the claims, and the dimensions of the silicon carbide nanowires can be obtained as desired. Of course, the synthesis conditions may be appropriately selected.

  Since the silicon carbide nanowire having a bamboo shape is obtained by the manufacturing method of the present invention, it is expected to be used in the field of microelectronics including field electron emission devices.

It is a figure which shows the X-ray-diffraction image of the wool-like substance synthesize | combined in the Example. It is a figure which shows the medium magnification scanning electron microscope image of the wool-like substance synthesize | combined in the Example. It is a figure which shows the high magnification scanning electron microscope image of the silicon carbide nanowire synthesize | combined in the Example. It is a figure which shows the high magnification scanning electron microscope image of the cross section of the silicon carbide nanowire synthesize | combined in the Example. It is a figure which shows the measurement result of the field electron emission characteristic of the silicon carbide nanowire synthesize | combined in the Example.

Claims (2)

The molar ratio of the silicon monoxide powder and the graphite powder is in the range of 1: 0.5 to 1: 0.6, and the molar ratio of the silicon monoxide powder and the gallium nitride powder is 1: 0.02 to 0.07. It ranged, silicon powder monoxide, a graphite powder and a mixture of gallium nitride powder flow in the range of 150~400sccm inert gas flow, in the range of 40 minutes to 2 hours at a temperature in the range of 1300-1400 ° C. A method for producing silicon carbide nanowires, characterized in that the silicon carbide nanowires are synthesized by heating for a period of time. The method for producing silicon carbide nanowires according to claim 1, wherein the inert gas is an argon gas.