KR100944971B1 - Method of preparing molybdenum dioxide or molybdenum thin film by hydrogen-reduction reaction of molybdenum oxide - Google Patents

Abstract

The present invention relates to a method for forming MoO ₂ or Mo thin film by the hydrogen reduction reaction of MoO ₃ , and more specifically, molybdenum oxide (MoO ₃ ) powder in contact with the metal substrate, and the reduction heat treatment process under a hydrogen atmosphere to control the metal A method of forming a molybdenum dioxide (MoO ₂ ) or molybdenum (Mo) thin film on a substrate.

Through the coating method according to the present invention, it is possible to coat molybdenum dioxide and molybdenum on metal in two-dimensional as well as three-dimensional form, and such a coating is coated with a thin film of molybdenum dioxide such as NH ₃ , CO, NO _x , SO Not only can be applied to a detection sensor for detecting a gas such as _x , but also can be applied to all fields coated with a molybdenum thin film.

Hydrogen reduction reaction, thin film

Description

METHOOD OF PREPARING MOLYBDENUM DIOXIDE OR MOLYBDENUM THIN FILM BY HYDROGEN-REDUCTION REACTION OF MOLYBDENUM OXIDE}

The present invention relates to a method for forming a MoO ₂ or Mo thin film by the hydrogen reduction reaction of MoO ₃ , and more specifically, it is possible to coat molybdenum dioxide and molybdenum on the metal as well as the two-dimensional form, This coating is not only applicable to a detection sensor that detects gases such as NH ₃ , CO, NO _x , SO _x by coating a molybdenum dioxide thin film, but also MoO ₂ or Mo thin film that is applicable to all applications using molybdenum thin films. It relates to a forming method.

When a material becomes a thin film, physical and chemical properties change significantly. Due to this property, a thin film technology plays an important role in the device field of information communication, organic biotechnology, and nanotechnology, which is an important technical task.

As a method of forming a thin film on a substrate, it is largely divided into a physical method and a chemical method. Physical methods include sputtering, ion plating, and thermal spraying, and chemical methods include CVD, sol-gel, and liquid epitaxial.

Physical vapor deposition has the advantage of being able to deposit a relatively simple and uniform coating layer, but not only requires expensive target materials, but also requires the deposition of only two-dimensional coating layers and high vacuum precision equipment. The disadvantage is that.

In addition, the chemical vapor deposition method has the advantage that the uniform coating layer is deposited in three dimensions, but not only the reactants are toxic, but the product causes environmental pollution.

In addition, the thermal spray method has the advantage of being industrially easy to use, but complex and high-risk equipment is required. In addition, since the coating structure contains defects such as pores, post-treatment such as heat treatment is necessary to remove pores, etc., and it is difficult to obtain uniform structure.

Therefore, there is a need for a new method for forming a thin film, which is simple, and for easily controlling physical properties of the formed thin film.

Korean Patent Publication No. 2003-86731 (US Patent Publication No. US2003 / 0211238) discloses a method of forming a tungsten thin film using tungsten oxide (WO ₃ ) powder. Specifically, after the tungsten oxide powder is contacted with the metal substrate, the tungsten oxide powder is subjected to reduction heat treatment under a hydrogen atmosphere, the temperature is reset, and the reduction heat treatment is performed again to form a tungsten thin film on the metal substrate.

The reduction heat treatment proposed in the patent is reduced from tungsten oxide to tungsten thin film by two steps of reduction according to the following scheme.

WO ₃ + H ₂ → WO ₂ + H ₂ O

WO ₂ + 2H ₂ → W + 2H ₂ O

However, in the case of tungsten oxide (WO ₃ ) powder, only the metal tungsten can be deposited because the chemical vapor transport (CVT) takes place in the second step of the reaction and the coating of the thin film is performed. Since deposition by CVT occurs at MoO ₂ and Mo can be selectively deposited, the temperature range should be adjusted according to the desired deposit and the thickness of the deposit.

In addition, in the case of tungsten oxide (WO ₃ ) powder has a variety of reduction parameters in the reduction process, because the reduction reaction proceeds through a complex process, it is necessary to consider many variables in order to secure the proper physical properties of the tungsten thin film.

Therefore, the present inventors have proposed a method of forming a tungsten thin film through reduction heat treatment [Kim et al , Effect of pre-reduced Cu particles on hydrogen-reduction of W-oxide In WO ₃ -CuO powder mixtures, Materials Science and Engineering A399 (2005) 326-331; Kim et al , The behavior of tungsten oxides in the presence of copper during hydrogen reduction, Journal of Alloys and Compounds , 419 (2006), 262-266.]. Through these documents, the present inventors have studied the effect of Cu on the hydrogen reduction process of tungsten oxide (WO ₃ ) powder and suggested that a tungsten thin film can be formed at a lower temperature.

On the other hand, molybdenum is similar to tungsten and its physical properties are excellent, and it is widely used in various fields. For example, molybdenum is used for incandescent lamps, electric discharge tubes, halogen lamp parts, other lighting components, materials for heat treatment jig, electron tubes, and magnetrons. It is widely used for parts, vacuum deposition heaters and boats, semiconductor electronic parts, semiconductor processing fixtures and TIG welding rods, electrode plasma-arc parts, electron beams and laser beam parts.

As described above, the production of molybdenum thin films is mainly based on physical and chemical vapor deposition.

Therefore, the inventors have studied the method of forming a molybdenum thin film by reduction heat treatment, considering that molybdenum has similar characteristics to that of tungsten. As a result, the molybdenum dioxide thin film or molybdenum on the metal substrate is changed by changing the heat treatment conditions. It was confirmed that the thin film can be selectively formed to complete the present invention.

It is an object of the present invention to provide a method for coating a molybdenum dioxide (MoO ₂ ) or molybdenum (Mo) thin film on the surface of a metal having a two-dimensional as well as a three-dimensional form by a simple process such as reduction heat treatment. .

In order to achieve the above object, the present invention

Molybdenum oxide (MoO ₃ ) powder is in contact with the metal substrate,

Reduction heat treatment at a temperature of 600 ° C. or higher under hydrogen atmosphere (H ₂ O / H ₂ ) to form a MoO ₂ thin film on a metal substrate.

Provided is a method of forming a MoO ₂ thin film.

In addition, the present invention

Molybdenum oxide (MoO ₃ ) powder is in contact with the metal substrate,

A primary reduction heat treatment at a temperature of 600 ° C. or higher under hydrogen atmosphere (H ₂ O / H ₂ ) to form a MoO ₂ thin film on a metal substrate,

Reducing the MoO ₂ thin film to a Mo thin film through a secondary reduction heat treatment at a temperature of 700 ° C. or higher under a hydrogen atmosphere.

Provided is a method for forming a Mo thin film.

Through the coating method according to the present invention, it is possible to coat molybdenum dioxide and molybdenum on metal in two-dimensional as well as three-dimensional form, and such a coating coats a molybdenum dioxide thin film to NH ₃ , CO, NOx, SOx, etc. It is expected to be applied to a detection sensor that detects a gas of, and is expected to be applied to all fields coated with molybdenum thin film.

In the present invention, the molybdenum dioxide (MoO ₂ ) and molybdenum (Mo) thin film is easily formed on the metal substrate through a reduction heat treatment process of MoO ₃ .

As shown in Scheme 1, the molybdenum thin film is reacted with a reducing gas such as hydrogen to reduce MoO ₂ when molybdenum oxide (MoO ₃ ) powder is heat-treated as hydrogen (H ₂ O / H ₂ ) atmosphere as a raw material. It is manufactured through a process called chemical vapor transport (CVT). That is, MoO ₃ powder used as a raw material is deposited as MoO ₂ on the substrate by CVT, and the MoO ₂ thin film thus deposited is reduced to the molybdenum thin film through a further reduction process.

MoO ₃ + H ₂ → MoO ₂ + H ₂ O... … … (One)

MoO ₂ + 2H ₂ → Mo + 2H ₂ O... … … (2)

Looking at the reaction scheme 1, MoO ₃ is reacted with hydrogen is reduced to MoO ₂ ((1) reaction), the reduced MoO ₂ is reduced to Mo again ((2) reaction) proceeds.

The reaction of (1) and (2) can be adjusted according to the treatment temperature.

If the tungsten thin film using a tungsten oxide (WO ₃₎ powder referred to in the prior art due to occur as the second step of chemical vapor transport is reduced can be formed only of metal tungsten film. However, in the case of the present invention, the raw material powder is MoO ₃ powder Chemical vapor transport takes place in the first stage of reduction. Accordingly, the coating of the MoO ₂ thin film and the Mo thin film can be selectively deposited through simple process parameter control of reduction heat treatment.

1 is a graph of humidity change in which the amount of H ₂ O is measured in a gas discharged while heating up at a temperature increase rate of 10 ° C. per minute from room temperature to 800 ° C. at the time of reduction using MoO ₃ powder.

Referring to FIG. 1, the reduction of MoO ₃ powder occurs in two stages as in the case of tungsten oxide powder, and deposition of MoO ₂ occurs by chemical vapor transport (CVT). At this time the deposition of MoO ₂ takes place at 400-700 ° C., and a peak is observed near 600 ° C. showing that the MoO ₃ powder is reduced to MoO ₂ . This means that the reduction to MoO ₂ by CVT reaction occurs most actively above 600 ^° C.

In addition, the peak according to the reduction reaction of MoO ₂ also occurs around 700 ℃, due to this graph is necessary to heat treatment at 700 ℃ or more in order to actively perform the reduction reaction to Mo.

Therefore, only the tungsten oxide powder can be deposited in the coating of the thin film using CVT. However, in the case of using the MoO ₃ powder, the MoO ₂ thin film and the Mo thin film can be selectively deposited in a simple manner through appropriate process control. There are advantages to it.

Thus, by controlling the temperature of the heat treatment according to the invention it is possible to selectively coat MoO ₂ or Mo on the surface of the metal substrate.

Figure 2 is a schematic diagram of the coating preparation of the MoO ₂ / Mo thin film according to an embodiment of the present invention.

After mounting a metal substrate inside a heat treatment apparatus such as a crucible, as shown in FIG. 2, molybdenum oxide (MoO ₃ ) powder is placed around it to form a hydrogen atmosphere (H ₂ O / H ₂ ) to perform heat treatment.

Specifically, according to the first embodiment of the present invention, the coating method of the MoO ₂ thin film is

Molybdenum oxide (MoO ₃ ) powder is in contact with the metal substrate,

Under a hydrogen atmosphere (H ₂ O / H ₂ ) is carried out through a step of reducing heat treatment at a temperature of 600 ℃ or more.

At this time, the material of the metal substrate is not limited in the present invention, all metal substrates are possible. Typically, the substrate may be Cu, Ni, Au, Pt, Co, Pd, Al, Si, Ge, C, Ga, As, P, B, Zn, Se, Cd, Sn, In, SiGe, GaAs, AlGaAs One substrate selected from the group consisting of GaAsP, InAs, Sn, InAsP, InGaAs, AlAs, InP, GaP, ZnSe, CdS, ZnCdS, CdSe, stainless steel, carbon steel and other metal mixed materials is possible.

The reduction heat treatment is carried out by adjusting the time according to the thickness of the desired deposit at least 600 ℃, preferably from 600 to 800 ℃. If the temperature is less than the above range, a sufficient reduction reaction is not performed so that the thin film formed on the surface of the metal substrate contains MoO ₃ as a raw material in addition to MoO ₂ . On the contrary, if the amount exceeds the above range, MoO ₂ and Mo are deposited together.

According to a second embodiment of the present invention, the coating method of the Mo thin film

Molybdenum oxide (MoO ₃ ) powder is in contact with the metal substrate,

A primary reduction heat treatment at a temperature of 600 ° C. or higher under hydrogen atmosphere (H ₂ O / H ₂ ) to form a MoO ₂ thin film on a metal substrate,

The secondary reduction heat treatment is performed at a temperature of 700 ° C. or higher under a hydrogen atmosphere (H ₂ O / H ₂ ) to reduce MoO ₂ to a Mo thin film.

As described in the first embodiment, the MoO ₂ thin film is formed on the surface of the metal substrate by the first reduction heat treatment.

Subsequently, a secondary reduction heat treatment is performed to reduce the MoO ₂ thin film to form a Mo thin film.

The secondary reduction heat treatment is carried out by adjusting the time according to the thickness of the desired deposit at least 700 ℃, preferably 700 ~ 900 ℃. If the temperature is less than the above range, a sufficient reduction reaction does not occur, so the thin film formed on the surface of the metal substrate includes MoO ₂ formed after the primary reduction heat treatment in addition to Mo. On the contrary, if the thickness exceeds the above range, the thickness of the thin film continues to be adjusted, and thus it must be adjusted.

Through the method described above, it is possible to form a MoO ₂ / Mo thin film on a metal substrate. As a result, as shown in FIG. 4, a uniform MoO ₂ thin film and a Mo thin film can be deposited.

This method has the following advantages.

First, it is a relatively simple method of reducing the metal substrate by raising the temperature in the hydrogen atmosphere in a state in which the powder and the substrate in contact with the three-dimensional in the molybdenum oxide powder.

Second, unlike conventional methods, water is produced as a product rather than a toxic reactant generated during the chemical vapor deposition process, which is quite environmentally friendly.

Third, furnaces that operate in a reducing atmosphere without the need for expensive target materials or high vacuum equipment in physical vapor deposition, and can only be heated up without the need for complex and high-risk equipment, such as for thermal spray coatings ) Alone has the advantage of coating a relatively uniform MoO ₂ and Mo thin film.

Hereinafter, preferred examples are provided to aid in understanding the present invention. However, the following examples are merely provided to more easily understand the present invention, and the contents of the present invention are not limited by the examples.

Example 1 MoO on a Cu Substrate ₂  Thin film coating

After the MoO ₃ powder was applied to the crucible at 2 mm, a 3 mm thick copper substrate was placed on top of the crucible, and again the MoO ₃ powder was applied at 2 mm onto the substrate. At this time, the copper substrate was washed with acetone for 10 minutes before use.

Next, hydrogen having a dew point of −76 ° C. was supplied into the crucible, and the temperature of the crucible was heated to 620 ° C. to reduce heat treatment at a temperature rising rate of 10 ° C./min to form a MoO ₂ thin film on the copper substrate.

3 is a scanning electron micrograph of a MoO ₂ thin film. Referring to FIG. 3, it can be seen that the MoO ₂ thin film is uniformly formed with particles having a size of about ₂ to 3 μm.

Figure 4 is a cross-sectional scanning electron micrograph of the copper substrate / MoO ₂ thin film prepared in Example 1. Referring to FIG. 4, it can be seen that the MoO ₂ thin film forms a uniform thin film having a thickness of about 14.5 μm on the copper substrate.

(Example 2) MoO on SUS substrate ₂  Thin film coating

In the same manner as in Example 1, but using a stainless steel substrate as a substrate to form a MoO ₂ thin film.

5 is a scanning electron micrograph of the MoO ₂ thin film prepared in Example 3; Referring to FIG. 5, it can be seen that particles having a size of 400 to 500 nm are uniformly deposited.

Example 3 MoO on a Ni Substrate ₂  Thin film coating

In the same manner as in Example 1, but using a nickel substrate as a substrate to form a MoO ₂ thin film.

6 is a scanning electron micrograph of the MoO ₂ thin film prepared in Example 3; Referring to FIG. 6, it can be seen that particles of about 500 nm size are uniformly coated while forming a MoO ₂ thin film.

Example 5 Mo thin film coating

After the MoO ₃ powder was applied to the crucible at 2 mm, a 3 mm thick copper substrate was placed on top of the crucible, and again the MoO ₃ powder was applied at 2 mm onto the substrate. At this time, the copper substrate was washed with acetone for 10 minutes before use.

Next, hydrogen having a dew point of −76 ° C. was supplied into the crucible, and the temperature of the crucible was heated to 620 ° C. and subjected to primary reduction heat treatment at a temperature rising rate of 10 ° C./min to form a MoO ₂ thin film on the copper substrate. .

Subsequently, the temperature of the crucible was heated at 900 ° C. for 1 hour and subjected to secondary reduction heat treatment to reduce the MoO ₂ thin film to a Mo thin film.

7 is a scanning electron micrograph of the Mo thin film, Figure 8 is a cross-sectional scanning electron micrograph thereof.

Referring to FIGS. 7 and 8, it can be seen that the Mo thin film forms a uniform thin film having a thickness of about 9.3 μm on the substrate.

The coating method according to the present invention is applicable to all fields using the coating of molybdenum thin film including various detection sensors by coating the molybdenum dioxide thin film.

1 is a graph of humidity change in which the amount of H ₂ O is measured in a gas discharged while heating up at a temperature increase rate of 10 ° C. per minute from room temperature to 800 ° C. at the time of reduction using MoO ₃ powder.

Figure 2 is a schematic diagram showing a device used in the coating of the MoO ₂ / Mo thin film according to an embodiment of the present invention.

3 is a scanning electron micrograph of a MoO ₂ thin film deposited on a copper substrate.

Figure 4 is a cross-sectional scanning electron micrograph of the copper substrate / MoO ₂ thin film prepared in Example 2.

FIG. 5 is a scanning electron micrograph of a MoO ₂ thin film deposited on a stainless steel substrate prepared in Example 3. FIG.

6 is a scanning electron micrograph of a MoO ₂ thin film deposited on a nickel substrate prepared in Example 3.

7 is a scanning electron micrograph of a Mo thin film deposited on a copper substrate.

8 is a cross-sectional scanning electron micrograph of a Mo thin film deposited on a copper substrate.

Claims (7)

Molybdenum oxide (MoO ₃ ) powder is in contact with the metal substrate, Reduction heat treatment at 600 to 800 ° C. under hydrogen atmosphere (H ₂ O / H ₂ ) to form a MoO ₂ thin film on a metal substrate. Method of forming MoO ₂ thin film. The method of claim 1, The metal substrate may be Cu, Ni, Au, Pt, Co, Pd, Al, Si, Ge, C, Ga, As, P, B, Zn, Se, Cd, Sn, In, SiGe, GaAs, AlGaAs, GaAsP, InAs, Sn, InAsP, InGaAs, AlAs, InP, GaP, ZnSe, CdS, ZnCdS, CdSe, stainless steel, carbon steel and a mixed material thereof. The method of claim 1, The reduction heat treatment is performed by adjusting the time according to the thickness of the deposit. Molybdenum oxide (MoO ₃ ) powder is in contact with the metal substrate, A primary reduction heat treatment at 600 to 800 ° C. under hydrogen atmosphere (H ₂ O / H ₂ ) to form a MoO ₂ thin film on a metal substrate, Reducing the MoO ₂ thin film to a Mo thin film through a secondary reduction heat treatment at 700 to 900 ° C. under a hydrogen atmosphere. Method of forming Mo thin film. The method of claim 4, wherein The metal substrate may be Cu, Ni, Au, Pt, Co, Pd, Al, Si, Ge, C, Ga, As, P, B, Zn, Se, Cd, Sn, In, SiGe, GaAs, AlGaAs, GaAsP, InAs, Sn, InAsP, InGaAs, AlAs, InP, GaP, ZnSe, CdS, ZnCdS, CdSe, stainless steel, carbon steel and a mixed material thereof. The method of claim 4, wherein The first reduction heat treatment is performed by adjusting the time according to the thickness of the deposit. The method of claim 4, wherein The secondary reduction heat treatment is performed by adjusting the time according to the thickness of the deposit.

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