KR101311763B1 - Method of manufacturing ZnO nanostructures - Google Patents

Abstract

The present invention relates to a method for producing zinc oxide nanostructures, comprising: preparing a zinc raw material; Injecting the zinc raw material into the crucible; Charging the crucible into a heating furnace; Oxidizing zinc by heating the crucible at a heat treatment temperature for a predetermined time; And cooling the crucible.

Description

Method of manufacturing zinc oxide nanostructures {Method of manufacturing ZnO nanostructures}

The present invention relates to a method for producing a nanostructure, and more particularly to a method for producing a zinc oxide nanostructure using a simple synthesis method.

Zinc oxide (ZnO), a wide bandgap semiconductor, has a bandgap energy of 3.37 eV at room temperature and an exciton (exciton) binding energy of 60 meV. For this reason, ZnO may be used in various ways as optical devices, solar cell windows, bulk acoustic wave devices, and the like. In particular, due to the possibility of application to a light emitting device exhibiting the light emission characteristics of the ultraviolet region has attracted great attention, due to the strong exciton binding energy is possible laser oscillation in the ultraviolet region even at room temperature.

Recently, after the laser oscillation of the ultraviolet region is observed from the nanowires, researches for synthesizing ZnO nanostructures having various forms have been actively conducted due to the expectation of their application to nanoelectronic devices. Until now, various ZnO nanostructures, including wires, tubes, belts, combs, and needle-like structures, have been manufactured according to various synthesis methods.

For example, synthesis methods such as thermal evaporation, chemical vapor deposition, sputtering, and organic chemical vapor deposition are used, but there is a problem that a complicated process is required because a vacuum atmosphere is required to synthesize nanostructures. In addition, such a manufacturing method has a problem that the production cost increases because expensive equipment is required.

The present invention provides a method for producing zinc oxide nanostructures in a simple manner.

The present invention provides a method for producing a zinc oxide nano structure excellent in crystallinity.

The present invention provides a method for producing zinc oxide nanostructures easy to control the crystal shape.

Zinc oxide nanostructure manufacturing method according to an embodiment of the present invention comprises the steps of preparing a zinc raw material; Injecting the zinc raw material into the crucible; Charging the crucible into a heating furnace; Oxidizing zinc by heating the crucible at a heat treatment temperature for a predetermined time; And cooling the crucible.

The heat treatment temperature is a temperature higher than the boiling point temperature of zinc, 910 ℃ to 1200 ℃.

The heating furnace is controlled in an oxidizing atmosphere.

The predetermined time is changed according to the amount of the raw material and is 5 minutes to 180 minutes when the raw material is 0.5g to 1g.

The furnace is heated at a rate of 5 ° C. per minute to 50 ° C. per minute at the heat treatment temperature.

The zinc raw material is a raw material having a purity of 99.9% or more.

As described above, according to the exemplary embodiments of the present invention, the zinc oxide nanostructure may be manufactured by a simple and simple method that does not require a vacuum atmosphere or the like and does not use a catalyst and a substrate.

According to the embodiments of the present invention, since the nanostructures are manufactured using only zinc powder without using a catalyst or other raw materials, zinc oxide nanostructures having high crystallinity and purity can be manufactured. In addition, the zinc oxide nanostructures may be manufactured in various shapes and have excellent light emission characteristics. The zinc oxide structure to be produced can be controlled in shape, thereby controlling the emission wavelength.

1 is a process flow diagram of a method for producing zinc oxide nanostructures according to an embodiment of the present invention.
2 is a crucible photograph after the heat treatment according to the experimental example of the present invention.
Figure 3 is an X-ray diffraction pattern result of the zinc oxide product prepared according to the experimental example of the present invention.
Figure 4 is a SEM image of the zinc oxide white product prepared according to the experimental example of the present invention.
5 is a SEM image photograph of the zinc oxide yellow product prepared according to the experimental example of the present invention.
Figure 6 is an EDX spectrum result of the zinc oxide product prepared according to the experimental example of the present invention.
7 is a CL spectra result of the zinc oxide product prepared according to the experimental example of the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below, but may be implemented in various forms, and only the embodiments are intended to complete the disclosure of the present invention and to those skilled in the art. It is provided for complete information.

1 is a process flowchart of a method of manufacturing zinc oxide nanostructures according to an embodiment of the present invention.

Referring to FIG. 1, a method for preparing a zinc oxide nanostructure includes preparing a zinc raw material, adding a zinc raw material to a crucible, charging a crucible to a heating furnace, and heating the crucible at a heat treatment temperature for a predetermined time. Oxidizing and cooling the crucible.

First, prepare raw materials. For example, the raw material is a metal zinc powder, and a high purity raw material having a purity of 99.9% or more may be used, and a spherical shape thereof may be used. In addition, the zinc raw material powder can use what is several micrometers in diameter. However, the shape of the raw material may use not only powder but also other shapes such as plate, and raw materials of various sizes may be used. On the other hand, only the raw material to be treated is used as the raw material, and no other raw material is used, thereby preventing the addition of impurities or contaminants. The zinc raw material thus prepared is introduced into the crucible. The crucible can use an alumina crucible.

Then, the crucible which stored the raw material powder is charged to a heating furnace, and a heating furnace is heated. The furnace uses a box-type electric furnace and is heated by applying power. In addition, the atmosphere in a heating furnace is controlled by an oxidizing atmosphere. That is, it is controlled by the atmosphere containing oxygen containing gas, such as oxygen and ozone. For example, it may be controlled to an atmosphere containing oxygen. Power is applied to the heating furnace to increase the temperature to the heat treatment temperature at a rate of 5 ° C./min or more, for example, 5 ° C./min to 50 ° C./min. At this time, the heat treatment temperature is preferably a temperature higher than the boiling point temperature of zinc. Since the boiling point temperature of metal zinc is 907 degreeC, heat processing is performed at higher temperature, for example, 910 degreeC-1200 degreeC. In addition, the heat treatment time at the heat treatment temperature is maintained at a time sufficient to oxidize the zinc powder, the heat treatment time is changed depending on the amount of the raw material powder, it is carried out for a time of 5 minutes or more, for example 5 minutes to 180 minutes . By maintaining a predetermined time at the heat treatment temperature of the oxidizing atmosphere, the metal zinc raw material powder is oxidized to form a zinc oxide nanostructure.

After the heat treatment of the zinc raw powder is completed, the furnace is turned off and the crucible is cooled to room temperature. After unloading the crucible to the outside of the furnace, to obtain a zinc oxide nano structure. As such, the zinc oxide nanostructures can be manufactured by a very simple synthesis method.

In the following, specific experimental examples will be described in detail. First, spherical powder having a purity of 99.9% and 4 µm in diameter was used as the metal zinc powder. No raw material was used except for the metal zinc powder. 0.5 gram and 1 gram of metallic zinc raw material powder were put into an alumina crucible, respectively.

Then, the crucible was placed in a box-type electric furnace controlled by an atmosphere, and power was applied to raise the temperature to 930 ° C at a rate of 10 ° C / min. After maintaining for 1 hour at 930 ℃ heat treatment temperature, the power was turned off and cooled to room temperature.

By this manufacturing process, the metal zinc was oxidized into a zinc oxide nano structure. As shown in FIG. 2, white product (2) and yellow product (3) were observed in the crucible (1), and each product was collected with tweezers to analyze the properties of the crystal structure, composition, microstructure, and cathode light emission of the material. It was.

The crystal structure was analyzed by X-ray diffractometer (XRD), and the shape was observed by scanning electron microscope (SEM). The components were evaluated by an energy dispersive X-ray spectrometer (EDX) attached to the scanning electron microscope, and the cathode emission characteristics were analyzed by a cathode ray spectrometer (CL) attached to the scanning electron microscope. The analysis and observation results are described in detail below.

Figure 3 shows the XRD pattern of the resulting oxide after oxidizing 0.5g and 1.0g of Zn powder in an electric furnace of atmospheric atmosphere in air at 930 ° C for 1 hour, respectively. That is, FIG. 3A shows a case of 0.5 g of zinc (Zn) raw material powder, and FIG. 2B shows a case of 1 g. Regardless of the amount of Zn powder, the peaks of all XRD patterns were in good agreement with the peaks seen in zinc oxide (ZnO) with hexagonal wurtzite structure. Since the boiling point of Zn is 907 ° C, it is thought that ZnO is formed by reacting with oxygen in the air at an oxidation temperature of 930 ° C.

The shape of the resulting oxide was observed by SEM. 4 (a) and (b) show low and high magnification SEM images of white oxides produced after oxidizing 0.5 g of Zn powder at 930 ° C. for 1 hour, and FIGS. 4 (c) and (d) show 1.0 g of Zn. Low and high magnification SEM images of the white oxide produced after oxidizing the powder at 930 ° C for 1 hour. Regardless of the amount of Zn, the tetrapod shape is shown in which four wires extend from the center of the crystal. In general, the growth of tetrapod structure of ZnO crystals is explained by the octa-twin nucleus model. The octa-twin nucleus of ZnO is composed of eight octahedral octahedral structures and the basic plane is {0001} plane. Four of the eight planes are Zn- (0001) planes (+ c) and the other four planes are O- (0001) planes (-c), alternately having opposite polarities. The + c plane whose surface layer is composed of Zn grows rapidly in the (0001) direction, but the -c surface whose surface layer is composed of O does not grow. Therefore, only the + c plane grows to form a tetrapod consisting of four wires. On the other hand, it can be seen from Figure 4 (c) and (d) that another wire of very large diameters grew on each of the wires constituting the tetrapod. This is thought to have occurred in secondary nucleation and growth. Gong et al. Reported that when nanowires grow beyond a certain threshold, secondary nucleation occurs in terms of growth. In this experimental example, the higher the Zn amount, the higher the vapor pressure.

5 is a SEM photograph showing the shape of a yellow oxide. 5 (a) and 5 (b) show the shape of yellow oxide produced after oxidizing 0.5 g and 1.0 g of Zn powder, respectively. When 0.5g of Zn powder is oxidized, it shows nanowire shape, but when 1.0g of Zn powder is oxidized, it shows a multipod shape composed of many wires. Xie et al. Reported that the density of nuclei produced affects the shape of ZnO nanostructures. The higher the density of the nucleus, the more it changes from a one-dimensional wire to a multipod. When many ZnO nuclei are formed, it is known that some nuclei aggregate and rapid growth in the c-axis direction from each nucleus grows into multipod crystals. Therefore, the yellow oxide composed of multipod-shaped crystals is thought to be generated in the region where ZnO nuclei are generated because of the high vapor pressure of Zn. When synthesizing ZnO nanostructures using Zn metal, Zn metal is rapidly oxidized from the surface of Zn metal, ZnO oxide layer is formed on the surface, and Zn vapor inside the oxide layer is formed through grain boundaries or cracks generated in the oxide layer. It is thought that ZnO nanostructures will be synthesized by evaporation to the surface of and react with oxygen. Therefore, since the Zn vapor pressure on the surface is considered to be greatly influenced by the thickness of the surface oxide layer, the grain boundaries and the crack density, the Zn vapor pressure on the surface is considered to be locally different. As described above, in the present experimental example, the nanowires could be grown without using a metal catalyst. In the case of such catalyst-free nanowire growth, growth is expected to be caused by vapor-solid (VS) growth mechanisms or other growth mechanisms rather than vapor-liquid-solid (VLS) growth theory using metal catalysts.

Fig. 6 (a) shows the white oxide produced after oxidizing 0.5g of Zn powder, Fig. 6 (b) shows the EDX pattern of yellow oxide, and Figs. 6 (c) and (d) show 1.0g of Zn. Oxidized powder shows EDX pattern of white oxide and yellow oxide. As can be seen from FIG. 6, the same pattern is shown, and no other components including Zn were detected except zinc (Zn) and oxygen (O). It can be seen that the resulting oxide is a highly pure ZnO material. Quantitative analysis was performed from EDX spectra. 6 (a), (b), (c), and (d) the constituent ratios (atomic%) of Zn and O are 50.53: 49.47, 57.85: 42.12, 66.57: 33.43, 74.95: 25.05, respectively, in the order of the spectra. Was calculated.

7 shows the CL spectrum measured at room temperature of oxidation products. Fig. 7 (a) shows the CL spectrum of a white ZnO oxide having a tetrapod shape after oxidizing 0.5 g of Zn powder, and Fig. 7 (b) shows the nanowire shape after oxidizing 0.5 g of Zn powder. CL spectrum of yellow ZnO oxide is shown. 7 (c) and (d) show CL spectra of white oxide having a tetrapod shape and a yellow product showing a multipod shape after oxidation of 1.0 g of Zn powder. 7 (a) and 7 (b) show light emission peaks in a strong ultraviolet region having a center wavelength at about 380 nm. 7 (c) and (d), the emission peak of the green region having a center wavelength of 510 nm is also observed in addition to the strong ultraviolet emission peak. Ultraviolet region emission at around 380 nm is known to be due to exciton bonding, and therefore, higher emission intensity indicates ZnO having excellent crystallinity. Since light emission in the green region near 510 nm is known to be caused by oxygen defects present in the ZnO crystals, a higher emission intensity in the green region indicates that more oxygen defects exist in the ZnO crystals. As can be seen from FIG. 7, the crystallinity of ZnO produced by oxidizing 0.5 g of Zn was 1 g from the fact that green light emission of 510 nm was not observed in the CL spectrum measured from ZnO produced by oxidizing 0.5 g of Zn. It can be seen that it is superior to the crystallinity of ZnO formed by oxidizing Zn. In the CL spectrum of ZnO produced by oxidizing 1 g of Zn powder, green light emission near 510 nm was observed, indicating that a significant concentration of oxygen defects existed in the crystal. This is in good agreement with the result of the component ratios of Zn and O of ZnO calculated from the EDX spectrum. On the other hand, it can be seen from the spectral results of FIGS. 7C and 7D that the crystallinity of the white oxide is superior to that of the yellow oxide. The relative ratio of the intensity of the ultraviolet light emission to the intensity of the green light emission is higher in that the white oxide is higher than the yellow product. This means that the concentration of oxygen defects present in the yellow oxide is higher. As described above, it is thought that the zone where yellow oxide was formed was locally high in the vapor pressure of Zn. Because of this, the concentration of Zn atoms combined with the defined oxygen concentration in the electric furnace was thought to be the result of ZnO crystals with high oxygen defects. .

As described above, ZnO nanocrystals having various shapes such as tetrapod, needle, and multipod shape could be generated through oxidation of Zn powder in an atmospheric pressure atmosphere in air. In addition, the amount of Zn raw material powder and the shape of crystals were controlled, and the CL characteristics could be adjusted. In other words, increasing the amount of the raw material powder ZnO crystals can exhibit the emission characteristics of the strong green region, and when controlled to a multipod shape rather than tetrapod and needle shape may cause the emission of strong green region. From the results of CL, various shapes are thought to be caused by the difference of Zn vapor pressure, and the higher the Zn vapor pressure, the more likely that multipod-shaped ZnO crystals are produced.

As mentioned above, although this invention was demonstrated with reference to the above-mentioned embodiment and an accompanying drawing, this invention is not limited to this, It is limited by the following claims. Therefore, it will be apparent to those skilled in the art that the present invention may be variously modified and modified without departing from the technical spirit of the following claims.

1: Crucible
2: white product
3: yellow product

Claims (7)

As a method for producing zinc oxide nanostructures,
The process of preparing zinc raw materials;
Injecting the zinc raw material into the crucible;
Charging the crucible into a heating furnace controlled by an oxidative atmosphere;
Heating the crucible at a heat treatment temperature for a predetermined time to oxidize zinc in the crucible; And
Cooling the crucible to obtain a zinc oxide nanostructure,
The zinc oxide nano structure is a zinc oxide nano structure manufacturing method having a multi-port shape consisting of a plurality of wires.
The method according to claim 1,
The heat treatment temperature is higher than the boiling point temperature of zinc zinc oxide nano structure manufacturing method.
delete The method according to claim 2,
The heat treatment temperature is 910 ℃ to 1200 ℃ zinc oxide nano structure manufacturing method.
The method according to claim 1,
The predetermined time is changed according to the amount of the raw material and when the raw material is 0.5g to 1g 5 minutes to 180 minutes manufacturing method of zinc oxide nanostructures.
The method according to claim 1,
The heating furnace is a method for producing zinc oxide nanostructures are heated to a rate of 5 ℃ / min to 50 ℃ / minute at the heat treatment temperature.
The method according to any one of claims 1, 2, 4 to 6,
The zinc raw material is a raw material of zinc oxide nano structure of 99.9% or more purity raw material.

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