JP3837540B2 - Method for producing single crystal tubular zinc oxide whisker - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for producing a single crystal tubular zinc oxide whisker that is useful as an optical device such as a light emitting diode or diode laser in a blue or ultraviolet region and as a reinforcing material for a composite material.
[0002]
[Prior art]
Zinc oxide, a II-VI group compound semiconductor, is expected to be applied to the optical field in the blue and ultraviolet regions such as light-emitting diodes and diode lasers. Furthermore, since zinc oxide whiskers are excellent in high-temperature strength, hardness, and chemical stability, they are also attracting attention in the field of composite material reinforcements and the like. Zinc oxide whiskers are usually made by vapor phase oxidation of metallic zinc powder. For example, zinc oxide whiskers are produced by oxidizing metal zinc particles coated with a mixture of zeolite and zinc oxide as a reaction catalyst (see, for example, Non-Patent Document 1). Recently, a method for producing a zinc oxide nanotube having a hollow portion or a tubular whisker has also been reported (see, for example, Non-Patent Documents 2 and 3). The crystal structures of nanotubes and tube-like whiskers manufactured by these methods are not single crystals but polycrystalline.
[0003]
[Non-Patent Document 1]
T. Yoshida, et al., Applied Physics Letters (APPl. Phys. Rett.), 64, 3243, 1994 [Non-patent Document 2]
J. Zhang, et al., Chemical Communications (Chem. Commun.) 3, 262, 2002 [Non-Patent Document 3]
JJWu, et al., Applied Physics Letters (Appl. Phys. Rett.) 81, 1312, 2002 [0004]
[Problems to be solved by the invention]
An object of the present invention is to solve the production of a single crystal tubular zinc oxide whisker having excellent electron mobility and emission intensity as compared with conventional polycrystalline zinc oxide.
[0005]
[Means for Solving the Problems]
In the present invention, zinc sulfide powder and activated carbon powder are heated in an argon stream at 1100 to 1200 ° C. for 2 to 4 hours to once generate zinc, and subsequently, argon is switched to oxygen and 1100 to 1200 This is a method for producing a single crystal tubular zinc oxide whisker by heating at 1 ° C. for 1 to 3 hours to carry out an oxidation reaction.
[0006]
Most whiskers obtained by the above method have a diameter of 400 nm and a length of 15 μm, but a small amount of whiskers having a diameter of 150 nm and a length of several micrometers is also included. Most whiskers are tube-shaped with hollow portions. The wall thickness is 100-150 nm. The single crystal tubular zinc oxide whisker obtained by the method of the present invention is expected to be applied to light emitting diodes and diode lasers in the blue and ultraviolet regions, and as a reinforcing material for composite materials.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
The conditions in the production method of the present invention will be described below.
A heating apparatus will not be specifically limited if the temperature conditions in the method of this invention, such as a resistance heating furnace and a high frequency induction heating furnace, are satisfy | filled.
First, zinc sulfide powder and activated carbon powder are heated to 1100 to 1200 ° C. in an argon stream for 2 to 4 hours to once generate zinc. The raw material powder has a particle size of about 10 microns. Mixing of noble gases other than argon gas is also possible. The temperature is 1100-1200 ° C. Since the sublimation temperature of zinc sulfide is around 1185 ° C, the reaction activity starts to appear in this vicinity. If the temperature is too high, it will dissipate out of the system. The heating time is 2 to 4 hours. Since it is carried out near the lower limit of the reaction temperature, there is not much change even if the reaction is carried out for 2 hours or 4 hours or more for sufficient product formation.
[0008]
Subsequently, a thermal oxidation reaction is performed at a high temperature in an oxygen stream. The oxygen stream can be mixed with a rare gas without any problem. The temperature is 1100-1200 ° C. At too high a temperature, the product will dissipate. In the reaction, the liquid zinc produced in the previous stage reacts with oxygen to produce zinc oxide crystals.
[0009]
【Example】
Example 1
A mixture of 3.0 g of zinc sulfide powder (particle size of 10 μm or less; manufactured by Aldrich) and 0.2 g of activated carbon powder (100 mesh; manufactured by Aldrich) is placed in an alumina boat, and this boat is quartz with an outer diameter of 42 mm and a length of 80 cm. Located in the center of the tube. The quartz tube was placed horizontally in a resistance heating furnace. The quartz tube was covered and heated at a rate of temperature increase of 10 ° C / min to raise the temperature to 1100 ° C. At this time, argon gas was allowed to flow at a flow rate of 80 sccm and maintained at this temperature for 3 hours.
[0010]
The zinc precursor was produced by the above method, and the argon gas was subsequently switched to oxygen gas at the same flow rate, and the temperature was maintained at 1100 ° C. for 2 hours. Thereafter, it was cooled to room temperature at a descending rate of 10 ° C / min. A white product was deposited on the inner wall of the quartz tube. The product yield was 20-30% based on zinc sulfide.
[0011]
The X-ray diffraction pattern of the product is shown in FIG. Looking at the obtained diffraction peaks, they are in good agreement with the known hexagonal zinc oxide peaks, the lattice constants are a = 0.325 nm, c = 0.521 nm, and peaks based on zinc sulfide and metallic zinc are observed. There wasn't.
[0012]
FIG. 2 (a) is a photograph of a scanning electron microscope image of the product. Most of the whiskers are linear, and no particles or other shapes are seen. Most whiskers are 400 nm in diameter and 15 μm in length, but a small amount of whiskers having a diameter of 150 nm and a length of several micrometers is also included.
[0013]
FIG. 2 (b) shows a high-power scanning electron microscope image, and it has been found that most whiskers have a tube shape having a hollow portion. The wall thickness is 100-150 nm.
[0014]
Fig. 3 shows the X-ray energy diffusion spectrum. Its chemical composition consists of zinc and oxygen, and its element ratio is 1: 1.05. It is found that stoichiometric zinc oxide is produced. It was. From the electron diffraction pattern, the lattice constants were a = 0.32 nm and c = 0.52 nm, which were the same as the values of the hexagonal zinc oxide obtained from the X-ray diffraction pattern. Samples taken from different locations also showed the same value, confirming a single crystal structure.
[0015]
FIG. 4 shows a photoluminescence vector at room temperature of the tubular zinc oxide whisker. There was a strong sharp emission peak at 381 nm and a weak broad peak at 583 nm, and the 381 nm peak was confirmed to coincide with the band gap of bulk zinc oxide.
[0016]
【The invention's effect】
According to the method of the present invention, a single crystal can be obtained from zinc oxide, which can be obtained only by a polycrystal in the conventional method. As a result, the electron mobility and the emission intensity are superior to those of the polycrystalline body, and therefore, it is highly expected in application to electronic devices.
[Brief description of the drawings]
FIG. 1 is an X-ray diffraction pattern of a single crystal tubular zinc oxide whisker.
FIG. 2 (a) is a drawing-substituting photograph showing a low-magnification scanning electron microscope image of a single crystal tubular zinc oxide whisker. FIG. 2 (b) is a drawing-substituting photograph showing a high-magnification scanning electron microscope image of a single crystal tubular zinc oxide whisker.
FIG. 3 is a diagram of an X-ray energy diffusion spectrum of a single crystal tubular zinc oxide whisker.
FIG. 4 is a diagram of a photoluminescence spectrum of a single crystal tubular zinc oxide whisker at room temperature.

Claims (1)

Zinc sulfide powder and activated carbon powder are heated to 1100 to 1200 ° C for 2 to 4 hours in an argon stream, and then argon is switched to oxygen and heated at 1100 to 1200 ° C for 1 to 3 hours. A method for producing a single crystal tubular zinc oxide whisker.

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