KR100634098B1 - fabrication method of crystalline metal tungstates thin films - Google Patents

Abstract

The present invention relates to a method for producing a metal tungstate (MWO ₄ (M = Mg, Ca, Sr, Ba, Co, Pb, etc.) crystalline thin film, the metal tungstate using a Nd: YAG pulse laser A method of depositing a thin film of nanometer-sized crystals by depositing metal tungstate molecules ablated from a target, wherein the position of the substrate is on-axis relative to the direction of the target. It is a method of manufacturing a very fast and efficient metal tungstate crystal thin film that uses both) and off-axis, and enables the deposition of crystallized nanoparticles at room temperature without heating the substrate during deposition, and the entire process takes only a few hours. .

Description

Fabrication method of crystalline metal tungstates thin films

1 is a schematic block diagram showing a pulse laser deposition equipment used in the present invention,

FIG. 2 is a detailed view of a portion on which a target is placed in FIG. 1; FIG.

3 is an X-ray diffraction pattern graph of Ar pressure in a chamber of a metal tungstate deposited according to the present invention;

Figure 4 is a transmission electron micrograph of a metal tungstate deposited in accordance with the present invention,

5 is an XPS analysis result of the metal tungstate deposited according to the present invention.

<Description of the symbols for the main parts of the drawings>

10: manufacturing apparatus 12: reaction chamber (chamber)

16: target support 18: target rotation axis

22: off-axis substrate 24: on-axis substrate

30: laser scanning device 32: window

34 laser oscillation means 36 laser condensing lens

42: motor 44: vacuum pump

46: Argon Gas Injection Nozzle

 L: laser light T: target

The present invention relates to a method for producing a metal tungstate crystal thin film, and more particularly, to a method for depositing a metal tungstate crystal thin film at room temperature using a pulse laser.

Metal tungstate, MWO ₄ (divalent cationic metal such as M = Mg, Ca, Sr, Ba, Co, Pb) is a material having MASER (Microwave Amplication by Stimulated Emission of Radiation) and fluorescence (Photoluminescence) It has been applied to devices such as communication, military radar, radio telescope, and X-ray detector. In particular, metal tungstate has been actively researched as a scintillator device or a fluorescent device because of its advantages of low hydroscopicity and low manufacturing cost compared to Bi ₄ Ge ₃ O ₁₂ (BGO).

The metal tungstate is a method of preparing a single crystal by completely melting the metal oxide and tungsten oxide powder in a platinum crucible and reacting for a long time, and the method of producing a metal oxide and sodium tungsten salt powder at a temperature of 1000 ℃ or more by a long time solid phase synthesis method. have. In addition, as disclosed in US Pat. No. 58,740,56, there is a method of wet-mixing a metal oxide and a tungsten compound and then heating at high temperature to synthesize a powder having a micrometer size level.

In order to prepare a thin film of a metal tungstate, an electrochemical dissolution method of growing a film while reacting an alkali solution with a tungsten metal has been mainly used.

However, when manufacturing a metal tungstate thin film using a conventional electrochemical dissolution method, the surface of the thin film is rough, there is a possibility of surface contamination by impurities, it is difficult to control the size of the grown crystal to the nanometer level There was this.

Therefore, the present invention has been made to solve the above problems, an object of the present invention is to uniformly deposit the surface of the metal tungstate thin film, metal tungstate crystals to control the crystal size of the deposited metal tungstate to several tens of nanometers or less It is to provide a method for producing a thin film.

The raw material of the present invention targets a metal tungstate having the same composition as the target substance composition. As a target, a sintered body obtained by synthesizing a powder in a general manner and molding and sintering the same is used. In the present invention, a nanoparticle thin film is deposited on a substrate using a coagulation phenomenon due to collision of metal tungstate atoms and molecules in a densified plasma of the same composition evaporated from the target surface by scanning pulse laser light on the target. In the process of scanning the laser light to the target, the delivery process of the plasma gas to the substrate may be controlled using the pressure of argon (Ar) gas, which is an inert gas. In this case, the target and the substrate are disposed in the horizontal direction (on-axis) or vertical (off-axis), and deposits a metal tungstate thin film composed of nanocrystals at room temperature without heating the substrate during deposition.

As the laser source, an Nd: YAG laser having a wavelength of 355 nm is used.

The atmosphere in the chamber during the process is controlled in the region of 10 Pa to 100 Pa using argon gas (Ar gas).

The scanning time of the laser is 10 minutes to 60 minutes.

Hereinafter, the present invention will be described in detail with examples.

EXAMPLE

First, a target is prepared using the same metal tungstate as the target material composition as a raw material. As a target of the metal tungstate, first, a metal tungstate powder is prepared by a general powder synthesis method, which is uniaxially formed into pellets having a diameter of 15 mm and a thickness of about 5 mm at a pressure of about 100 MPa, and 1000 ° C. in air. The sintered compact obtained by sintering at the temperature of -1200 degreeC for 3 to 5 hours is used.

Using the target of the metal tungstate, the atmosphere in the chamber was subjected to pulse laser deposition in a pressure range of 10 to 100 Pa using argon gas (Ar gas). In the present invention, the indicated manufacturing apparatus 10 as shown in Figs. 1 and 2 is used.

The manufacturing apparatus 10, the target support 16, which is supported by mounting the target T of the metal tungstate inside the reaction chamber 12 is rotatably coupled by the target axis of rotation 18, the target support The upper side of the 16 is provided with a vertical substrate 22 and a horizontal substrate 24 on which metal tungstates are deposited. Outside the reaction chamber 12, a laser scanning device 30, a motor 42, and a vacuum pump ( 44 and the argon gas injection nozzle 46 are combined.

The target support 16 is generally located in the center of the reaction chamber 12, the vertical substrate 22 is installed perpendicular to the target support 16 above the edge of the target support 16, the horizontal substrate 24 is installed in parallel with the target support 16 on the upper side of the target support 16, so that the target support 16, the vertical substrate 22 and the horizontal substrate 24 generally form a c-shape. Located. The laser light L incident on the target T in the laser scanning device 30 enters into a c-shaped open portion formed by the target support 16, the vertical substrate 22, and the horizontal substrate 24. In this case, the laser light (L) is incident to the target (T) plane at an angle of approximately 45 degrees.

The laser scanning device 30 is a Nd: YAG laser having a wavelength of 355 nm, is installed on the outer circumferential surface of the reaction chamber 12 to generate a window 32 through which the laser light L passes, and to generate laser light. The laser oscillation means 34 and the laser light generated by the region oscillation means 34 are collected to scan the laser light L through the window 32 to the target T inside the reaction chamber 12. And a laser condenser lens 36 provided between the laser oscillation means 34 and the window 32.

The motor 42 is a control motor that rotates the target support 16 so that the target T rotates at a constant speed while uniformly scanning the surface of the target T during laser scanning.

The vacuum pump 44 is a pump that vacuums the inside of the reaction chamber 12 before injecting the argon gas into the reaction chamber 12, and the argon gas injection nozzle 46 is connected to a connection pipe (not shown). Through the argon storage tank.

According to the present invention, nanoparticles are formed using agglomeration phenomena due to collision of metal tungstate atoms and molecules in a densified plasma (evaporation material) of the same composition vaporized on the target surface by scanning pulse laser light L on the target T. The particulate thin film is deposited on the substrates 22 and 24. Therefore, a metal tungstate thin film composed of nanocrystals can be deposited at room temperature without heating the substrate during deposition.

In the process of scanning the laser light L to the target T, the transfer process of the plasma gas (evaporation material) to the substrates 22 and 24 is controlled by using the pressure of argon (Ar) gas, which is an inert gas. Inert gas other than this can also be used.

Laser ablation of the present invention scans the laser light L of high energy density (pulse energy (pulse energy, 1J / cm ² or more)) onto the target T and evaporates to the substrate site while the target surface is evaporated. In the Nd: YAG laser used in the present invention, conditions of a typical repetition frequency of about 10 Hz, a pulse width of 17 ns, and a pulse number of about 20000 are used. Reference numerals 22 and 24 use quartz or Si substrates, and the positions of the substrates are used by installing both on-axis and off-axis directions with the direction of the target.

The scanning time of the said laser is 10 minutes-60 minutes.

After the deposition process was completed, it was confirmed that a thin film made of fine particles of 10 nm or less was formed on the vertical substrate 22 perpendicular to the direction of the target T, and on the horizontal substrate 24 horizontal to the target T. It was confirmed that a denser film made of particles grown compared to the vertical substrate 22 was formed.

Figure 3 shows the X-ray diffraction pattern of PbWO ₄ synthesized by the above method according to the pressure of argon gas (Ar gas). As shown in FIG. 2, the characteristic patterns of PbWO ₄ appeared within a pressure range of 10 Pa to 100 Pa, and no oxides or other reactants such as PbO or WO ₃ were found.

4 is a transmission electron microscope (TEM) image of a PbWO ₄ thin film synthesized by the above-described method. As a result, the microstructure of the composite was scanned, and the thin film was formed of extremely fine nano-sized crystals having a particle size of 10 nm or less. .

FIG. 5 shows the results of X-ray photoelectron spectroscopy (XPS) of a thin film of PbWO ₄ synthesized by the above-described method. As shown, pure PbWO containing no impurities or other oxides as a result of scanning the binding state and binding energy of the composite is shown. _{4 It} was confirmed that the crystal thin film.

The metal tungstate thin film produced by the synthesis method according to the present invention can be used for fabricating field emission display (FED) and Scintillator devices.

 According to the method for manufacturing a metal tungstate crystal thin film according to the present invention, in the process of depositing a metal tungstate thin film using a metal tungstate target having the same composition, a thin film made of nanoparticle-level crystal grains is not heated. In terms of growth, the whole process takes place within a few hours, which is very fast, efficient and superior to the conventional metal tungstate thin film manufacturing method.

Claims (6)

delete A target was prepared by sintering a powder having a metal tungstate composition as a starting material, The prepared target and the substrate to be deposited are installed in the chamber, and the vaporized material generated by scanning laser light on the target is transferred to the substrate to be deposited to prepare a metal tungstate thin film having the same composition. The substrate is a method of manufacturing a metal tungstate crystal thin film, characterized in that installed in the direction of the target (on-axis) and vertical (off-axis) direction. A target was prepared by sintering a powder having a metal tungstate composition as a starting material, The prepared target and the substrate to be deposited are installed in the chamber, and the vaporized material generated by scanning laser light on the target is transferred to the substrate to be deposited to prepare a metal tungstate thin film having the same composition. The method of manufacturing a metal tungstate crystal thin film, characterized in that for the transfer of the evaporation material generated in the process of scanning the laser light to the target using an inert gas. The method of claim 3, The inert gas is a manufacturing method of the metal tungstate crystal thin film, characterized in that the use of argon gas. The method according to claim 3 or 4, The pressure of the inert gas is a method for producing a metal tungstate crystal thin film, characterized in that the deposition is performed at 10 Pa ~ 100 Pa. The metal tungstate crystal thin film formed by the manufacturing method of any one of claims 2 to 4.

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