JP2001098373A - Production of titanium oxide thiin film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for depositing titanium oxide thin film onto the surface of an organic material such as plastics at low temperatures without causing no deformation. SOLUTION: Titanium oxide is evaporated onto the surface of a substrate by using a helium ion beam as an assist ion beam. Because acceleration energy can be minimized by the use of the helium ion beam, the rise in the temperature of the substrate at vapor deposition can be prevented and the titanium oxide thin film can be formed even on the substrate made of organic material easily affected by heat.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a method for forming a titanium oxide thin film. More specifically, the present invention relates to a method for producing a titanium oxide thin film by depositing titanium oxide on a substrate surface using a helium ion beam as an assist ion beam.

[0002]

2. Description of the Related Art It is known that titanium oxide is polarized by light and acts as a catalyst. The titanium oxide thin film formed on the surface of glass, metal, or the like acts as an oxidation catalyst film when exposed to light, and decomposes organic substances on the surface, thereby exhibiting excellent antifouling, sterilizing, and deodorizing effects. Attempts have been made to purify the environment and prevent pollution by utilizing the photocatalytic properties of such a titanium oxide thin film. For example, research aimed at purifying the environment by decomposing harmful organic components in the air or water formed on glass, tiles, or metal substrates,
Research has been conducted to decompose organic substances attached to the titanium oxide thin film and to prevent accumulation of dirt.

Further, a titanium oxide thin film has a high refractive index,
By combining with a high reflection film or a low refractive index film,
Useful as a wavelength selective reflection or absorption film.

[0004] Various methods have been studied to produce a titanium oxide thin film having the above-mentioned features and its importance has been recognized. For example, as a method for forming a thin film of titanium oxide on a substrate surface, a dry method such as an evaporation method, a CVD method, and a sputtering method, a sol-gel method, a plating method, and a wet method such as an electrolytic polymerization method are known.

[0005] Among the dry methods, a vapor deposition method or a sputtering method can provide a uniform and dense film. Therefore, these methods are suitable methods for producing a device having excellent electrical characteristics, optical characteristics, and the like. is there.

However, in order to obtain a titanium oxide thin film having photocatalytic properties by a vapor deposition method, it is necessary to heat the substrate to a high temperature of 350 ° C. or higher. Therefore, there is a limitation that the material of the substrate to be used is limited to inorganic materials such as glass, ceramics and metal.

The method of forming a titanium oxide thin film by vapor deposition is not limited to the above-mentioned inorganic materials, and if it can be used for an organic material such as plastic and paper which is light in weight and excellent in moldability, the application field of the titanium oxide thin film Spreads dramatically. However, organic materials are generally decomposed or deteriorated at a high temperature of 350 ° C. or higher, and it is difficult to form a crystalline titanium oxide film on the surface.

As a method for forming a photocatalytic film on an organic material, a method has been developed in which crystalline titanium oxide fine particles are applied to a substrate using an organic polymer as a binder and cured at a relatively low temperature of 100 to 200 ° C. However, the effect cannot be obtained unless the titanium oxide fine particles are exposed on the surface.
Therefore, a processing step for exposing the titanium oxide fine particles to the surface is troublesome, and has not been widely spread. Furthermore, the organic polymer itself used as a binder may be decomposed due to the photocatalytic effect of the titanium oxide fine particles, and there is a problem that durability is not sufficient.

As a method for obtaining a crystalline titanium oxide thin film at a low temperature, a vapor deposition method using an argon ion beam assist method is known (T. IEEE Japan, Vol. 116, No. 80).
4-809 (1996)). According to this method, when titanium is deposited on a substrate in an oxygen atmosphere, an argon ion beam is used as an assist ion beam to promote a deposition reaction of titanium oxide, thereby obtaining crystalline titanium oxide at a lower temperature. However, since this method also uses an argon element as an ion beam source, there is a problem in that acceleration energy is increased, a phenomenon in which the temperature of the substrate is increased, and the plastic is decomposed or deformed.

[0010]

As described above, a crystalline titanium oxide thin film (hereinafter, may be simply referred to as a titanium oxide thin film) at a low temperature without decomposing or deforming an organic material.
Is required to be formed.

The present invention has been made to solve the above problems, and has as its object to provide a method for forming a novel titanium oxide thin film. According to the present invention, there is provided a method for forming a titanium oxide thin film on an organic material such as plastic or paper at a low temperature without decomposing or deforming the plastic or paper.

[0012]

According to the present invention, there is provided a method for producing a titanium oxide thin film by an ion beam assisted reaction, wherein titanium oxide is deposited on a substrate surface using a helium ion beam as an assist ion beam. The present invention relates to a method for producing a titanium oxide thin film.

[0013] In a preferred embodiment, the substrate is an organic material.

[0014] In a preferred embodiment, the titanium oxide thin film has an anatase crystal structure.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The ion beam assist method is a method of controlling the crystallinity of a titanium oxide thin film being formed by irradiating an electron beam or an ion beam during sputter deposition. According to this method, even if the energy of the ion beam is low, the characteristics of the film can be controlled over a wide range in the depth direction.

The present inventor has proposed a method of forming a titanium oxide thin film at a lower temperature than when using a conventional argon ion beam by using helium ions as an assist beam when titanium is deposited on a substrate in an oxygen atmosphere. succeeded in. Helium ions have a mass about one-tenth that of argon ions, and can promote the bond between titanium and oxygen with low acceleration energy. Therefore, the temperature rise of the substrate can be extremely low. A thin film can be formed.

The formation of a titanium oxide thin film by the ion beam assist method can be performed, for example, using a thin film forming apparatus as shown in FIG. Oxygen is introduced into the chamber 1 from the rotary substrate holder 5, the substrate 6 fixed to the substrate holder 5, the crystal oscillator film thickness monitor 4, and the oxygen cylinder 12 through the valve 13 into the chamber 1 of the thin film forming apparatus. An oxygen introducing pipe 14, a Faraday cup 9 for adjusting a current density, an electron beam evaporation apparatus 8, and a shutter 7 for controlling a film forming speed are provided. The chamber 1 is further provided with an oil rotary pump 2 and an oil diffusion pump 3 for exhausting air in the chamber 1, and a bucket type ion source 11 for ionizing helium and a substrate 6 for ionizing helium as a beam. And a strong electrolytic electrode plate 10 for irradiating the substrate. A helium introduction pipe 17 for introducing helium from a helium cylinder 15 via a valve 16 is connected to the bucket type ion source 11.

This device is used as follows. First, the pressure in the chamber 1 is reduced to a predetermined pressure by the vacuum pumps 2 and 3, and then oxygen gas is supplied into the reduced pressure chamber 1 from the oxygen cylinder 12 through the valve 13 to a predetermined partial pressure. Is introduced. On the other hand, titanium vapor generated from the electron beam evaporation device 8 is filled with a predetermined partial pressure. Helium gas introduced from the helium cylinder 15 through the bulb 16 is ionized by the hot filament discharge type bucket ion source 11, and the generated helium ions are extracted from the electrode plate 10, and the extracted helium ion beam rotates. The substrate mounted on the substrate holder 5 is irradiated vertically with a predetermined acceleration energy. The current density of the ion beam is adjusted by the Faraday cup 9. This helium ion beam
The bonding between titanium and oxygen, that is, the generation of titanium oxide is promoted, and the generated titanium oxide is deposited on the substrate 6. The deposition rate of the titanium oxide thin film is monitored by a quartz crystal resonator film thickness monitor 4 and is adjusted by opening and closing a shutter 7.

In the process of forming the titanium oxide thin film,
By controlling the energy of the irradiation ions, the adhesion, hardness, crystallinity, magnetic properties,
Optical characteristics and the like can be variously changed.

[0020] In a helium ion beam assisted method, the pressure of the chamber ^{4 × 10 - 4 ~8 × 10} -4 P
a, and more preferably 6 × 10 ⁻⁴ Pa or less.

The helium gas pressure may be a pressure at which the helium ion current density can secure about ²⁰ μA / cm ^2, preferably 1 × 10 ^{−3 to} 6 × 10 ⁻³ Pa, and preferably 2 × 10 ⁻³ Pa. It is more preferable that it is 4 × 10 ⁻³ Pa.

The oxygen gas pressure after the introduction of helium gas may be any gas pressure at which the acceleration of the reaction by the ion beam is ensured, and is preferably 8 × 10 ⁻³ to 4 × 10 ⁻² Pa, and preferably 1 × 10 ⁻³ Pa. ^{-2 to} 2 × 10 ⁻² Pa is more preferable.

It is desirable that the deposition rate of titanium be 0.1 nm / s or less. If the deposition rate is higher than this, titanium cannot react with oxygen, resulting in an oxygen deficiency state.

Helium ion energy is about 2 KeV
Desirably, it is ５5 KeV. If it is lower than 2 KeV, energy for promoting a bonding reaction between titanium and oxygen is insufficient, and titanium oxide does not crystallize. On the other hand, 5K
If it exceeds eV, the film forming temperature will increase, and the range of influence of the ion beam will be extended to the inside of the film, which is not preferable.

When crystallizing titanium oxide, the product of the acceleration voltage of helium ion and the current density must be 40 to 100 mW /, in order to keep the substrate surface temperature at 100 ° C. or less at which no deformation or decomposition of the organic material occurs. cm ² is preferred.

[0026]

EXAMPLES The present invention will be described below with reference to examples.
The present invention is not limited to this embodiment.

(Example 1) Using a thin film forming apparatus according to the ion beam assist method shown in FIG.
Titanium oxide was deposited on a 50 × 3 mm polypropylene test piece. The chamber was evacuated using an oil diffusion pump and an oil rotary pump until the degree of vacuum reached 6 × 10 ⁻⁴ Pa. After introducing helium gas and setting the helium gas pressure to 4.0 × ^10-3 Pa, oxygen gas was introduced,
The total pressure of helium and oxygen is 2.0 × 10 ⁻² Pa
And The helium gas introduced from the gas introduction tube was ionized using a hot filament discharge type bucket type ion source. The ionized helium ions are extracted by the strong electric field electrode plate, and the extracted helium ion beam is vertically incident on the polypropylene substrate fixed to the substrate holder placed 50 cm from the ion source at an acceleration energy of 2 KeV. Designed to be.
The current density of the ion beam (about 100 mm in diameter) was measured by a Faraday cup placed in front of the substrate holder.
μA / cm ² .

Titanium was deposited using an electron beam deposition apparatus (EB gun: 3 Kw) placed 20 cm below the substrate holder. The substrate holder was rotated at a rotation speed of 10 rpm to make the film thickness distribution uniform. When evaporating titanium using an electron beam evaporator, a shutter is opened and closed so that the evaporating speed becomes constant at 0.05 nm / s while monitoring with a quartz oscillator film thickness monitor arranged near the substrate holder. Was.

After 30 minutes, the polypropylene piece substrate was taken out and its shape was visually observed, but no deformation of the substrate was observed.

Example 2 Instead of polypropylene, 50
Using a stainless piece of × 50 × 3 mm as a substrate, a titanium oxide thin film was formed on the stainless substrate under the same conditions as in Example 1. The result of the XRD measurement is shown in FIG. From FIG. 2, it was confirmed that this titanium oxide had an anatase type crystal structure (2θ = 23.5 degrees). From this, it is considered that also in Example 1, a titanium oxide thin film having an anatase crystal structure was formed.
By having this anatase type crystal structure, a more efficient photocatalysis than the rutile type is expected.

[0031]

According to the present invention, the use of a helium ion beam as an assist ion requires a small acceleration energy, so that the temperature rise of the substrate can be suppressed during the deposition of titanium oxide. That is, a crystalline titanium oxide thin film can be formed on an organic material substrate that is weak against heat.

Conventionally, an organic binder required for forming a titanium oxide thin film on an organic material is not required, so that the life of the organic material having the titanium oxide thin film is greatly extended.

[Brief description of the drawings]

FIG. 1 is a schematic view of an apparatus used for a method for forming a titanium oxide thin film of the present invention.

FIG. 2 is a view showing an anatase structure of a titanium oxide thin film.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Chamber 2 Oil rotary pump 3 Oil diffusion pump 4 Quartz crystal film thickness monitor 5 Rotary substrate holder 6 Substrate 7 Shutter 8 Electron beam evaporation device 9 Faraday cup 10 Strong electric field electrode plate 11 Bucket type ion source 12 Oxygen cylinder 13 Valve 14 Oxygen introduction tube 15 Helium cylinder 16 Valve 17 Helium introduction tube

Claims (3)

[Claims] 1. A method for producing a titanium oxide thin film by an ion beam assisted reaction, comprising: depositing titanium oxide on a substrate surface using a helium ion beam as an assist ion beam. 2. The method according to claim 1, wherein said substrate is an organic material. 3. The method according to claim 1, wherein the titanium oxide thin film has an anatase-type crystal structure.