JP2004299920A - Method for manufacturing tubular single crystal zinc oxide whisker - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing tubular single crystal zinc oxide whiskers which are excellent in electron mobility or light emission intensity in comparison with conventional polycrystalline zinc oxide. <P>SOLUTION: The method for manufacturing tubular single crystal zinc oxide whiskers comprizes heating a zinc sulfide powder and an activated carbon powder at 1,100-1,200°C in a gaseous argon stream for 2-4 h, and heating them at 1,100-1,200°C for 1-3 h after switching from the gaseous argon to gaseous oxygen. By this method, a single crystal of zinc oxide is obtained although only polycrystalline bodies of zinc oxide are obtained by the conventional method. The whiskers are highly expected to be utilized in electronic devices, that is, light emitting diodes, diode laser or the like because the electron mobility or light emission intensity of the single crystal is more excellent than that of the polycrystalline bodies. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for producing a single-crystal tubular zinc oxide whisker useful for application to optical devices such as light-emitting diodes and diode lasers in the blue and ultraviolet regions and as a reinforcing material for composite materials.
[0002]
[Prior art]
Zinc oxide, which is a II-VI group compound semiconductor, is expected to be applied to optical fields in the blue and ultraviolet regions such as light-emitting diodes and diode lasers. Further, zinc oxide whiskers have been attracting attention in the field of reinforcing materials for composite materials and the like because of their excellent high-temperature strength, hardness and chemical stability. Zinc oxide whiskers are usually produced by gas phase oxidation of zinc metal powder. For example, zinc oxide whiskers are manufactured by oxidizing metal zinc particles coated with a mixture of zeolite and zinc oxide as a reaction catalyst (for example, see Non-Patent Document 1). Recently, methods for producing zinc oxide nanotubes and tubular whiskers having a hollow portion have also been reported (for example, see Non-Patent Documents 2 and 3). The crystal structure of nanotubes and tubular whiskers manufactured by these methods is not single crystal but polycrystal.
[0003]
[Non-patent document 1]
T. Yoshida et al., Applied Physics Letters (APP1. Phys. Rett.) 64, 3243, 1994 [Non-Patent Document 2]
J. Zhang, et al., Chemical Communications (Chem. Commun.) No. 3, p. 262, 2002 [Non-Patent Document 3]
J. J. Wu, et al., Applied Physics Letters (Appl. Phys. Rett.) 81, 1312, 2002.
[Problems to be solved by the invention]
An object of the present invention is to provide a method for manufacturing 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 to 1100 to 1200 ° C. for 2 to 4 hours to generate zinc once, and then argon is switched to oxygen to 1100 to 1200. This is a method of producing a single-crystal tubular zinc oxide whisker by heating at 1 ° C. for 1 to 3 hours to cause an oxidation reaction.
[0006]
Most whiskers obtained by the above method are 400 nm in diameter and 15 μm in length, but also include small amounts of whiskers having a diameter of 150 nm and a few micrometers in length. Most whiskers are tubular with hollows. Its wall thickness is 100-150 nm. The single-crystal tubular zinc oxide whiskers obtained by the method of the present invention are expected to be applied to light-emitting diodes and diode lasers in the blue and ultraviolet regions and to be used as reinforcing materials for composite materials.
[0007]
BEST MODE FOR CARRYING OUT THE INVENTION
The conditions in the manufacturing method of the present invention will be described below.
The heating device is not particularly limited as long as the temperature conditions in the method of the present invention such as a resistance heating furnace and a high-frequency induction heating furnace are satisfied.
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 diameter of about 10 microns. Mixing of other rare gases other than argon gas is also possible. The temperature is between 1100 and 1200 ° C. Since the sublimation temperature of zinc sulfide is around 1185 ° C., the reaction activity starts to appear near this temperature. If the temperature is too high, it will escape out of the system. The heating time is 2 to 4 hours. Since the reaction is performed at a temperature near the lower limit of the reaction temperature, there is not much change even when the reaction is performed for 2 hours or 4 hours or more so that the product is sufficiently generated.
[0008]
Subsequently, a thermal oxidation reaction is performed at a high temperature in an oxygen stream. The oxygen gas flow can be mixed with a rare gas without any problem. The temperature is between 1100 and 1200 ° C. At too high a temperature, the product escapes. In the reaction, the liquid zinc produced in the preceding 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: 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 the boat is 42 mm in outer diameter and 80 cm in length. At the center of the quartz tube. The quartz tube was placed horizontally in a resistance heating furnace. The quartz tube was capped and heated at a heating rate of 10 ° C./min to raise the temperature to 1100 ° C. At this time, argon gas was flowed at a flow rate of 80 sccm, and the temperature was maintained at this temperature for 3 hours.
[0010]
A zinc precursor was produced by the above method, and the temperature was maintained at 1100 ° C. for 2 hours while switching the argon gas to oxygen gas at the same flow rate. Then, it was cooled to room temperature at a 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, the peaks well agree with those of the known hexagonal zinc oxide, and the lattice constants are a = 0.325 nm and c = 0.521 nm. Not observed.
[0012]
FIG. 2 (a) shows a photograph of a scanning electron microscope image of the product. Most of the whiskers are linear, and no particles or other shapes are observed. Most whiskers are 400 nm in diameter and 15 μm in length, but also include small amounts of whiskers having a diameter of 150 nm and a few micrometers in length.
[0013]
FIG. 2B shows a scanning electron microscope image at a high magnification, and it was found that most of the whiskers were tubular with a hollow portion. Its wall thickness is 100-150 nm.
[0014]
FIG. 3 shows the X-ray energy diffusion spectrum. Its chemical composition is composed of zinc and oxygen, the element ratio is 1: 1.05, and stoichiometric zinc oxide is produced. I understood. The lattice constants a = 0.32 nm and c = 0.52 nm from the electron diffraction pattern were the same as those of the hexagonal zinc oxide obtained from the above-mentioned X-ray diffraction pattern. A sample taken from another place showed the same value, and it was confirmed that the sample had a single crystal structure.
[0015]
FIG. 4 shows the photoluminescence vector of a tubular zinc oxide whisker at room temperature. There was a strong sharp emission peak at 381 nm and a weak broad peak at 583 nm, and it was confirmed that the peak at 381 nm coincided 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 could be obtained only in a polycrystalline form by the conventional method. As a result, the electron mobility and the emission intensity are better than those of the polycrystalline material, so that they are expected to be greatly applied when applied 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. 2A is a drawing substitute photograph showing a low-magnification scanning electron microscope image of a single-crystal tubular zinc oxide whisker. FIG. 2B is a drawing substitute photograph showing a high-magnification scanning electron microscope image of a single-crystal tubular zinc oxide whisker.
FIG. 3 is 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)

After heating zinc sulfide powder and activated carbon powder to 1100 to 1200 ° C. for 2 to 4 hours in an argon stream, argon is switched to oxygen, and heating is performed 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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