JP2002030416A - Fabrication method of visible light responsive titanium oxide thin film - Google Patents

Abstract

(57) Abstract: it relates to a method of making a photocatalytic film is intended to improve the photocatalytic reaction efficiency by changing the optical response wavelength region of TiO _2. SOLUTION: This method is for producing a visible light responsive type titanium oxide thin film by thermally diffusing a transition metal into a titanium dioxide (TiO ₂ ) thin film formed by a laser vapor deposition method. 250 nm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a method of making a photocatalytic film is intended to improve the photocatalytic reaction efficiency by changing the optical response wavelength region of TiO _2.

[0002]

_2. Description of the Related Art The photocatalytic effect of TiO.sub.2 is an action of causing a photochemical reaction on the surface by irradiation with ultraviolet rays (wavelength of 400 nm or less) to decompose and remove organic substances and bacteria in contact with the surface. However, since most of sunlight is visible light (wavelength of 400 nm or more), the titanium oxide photocatalyst that requires ultraviolet light has a disadvantage that sufficient decomposition efficiency cannot be obtained, and the efficiency is high even under natural light or indoor lighting. A method for forming a photocatalyst is desired.

[0003]

The present invention is to challenge it to solve the above-by adding a transition metal to TiO _2, by extending to a more visible side photoresponsive region of TiO _2, high efficiency under natural light and indoor lighting under It is intended to provide a method for producing a photocatalytic thin film.

[0004]

According to the present invention, a visible light responsive TiO ₂ thin film is produced by a transition metal (Ta, Nb, Cr, Ta, Nb, Cr,
A Zr, W) layer is further deposited with a TiO ₂ thin film having a thickness of about several hundred nm, and is interdiffused by heat treatment to form a mixed phase having visible light responsiveness.

That is, according to the present invention, a transition metal target is evaporated in a vacuum by a laser beam to deposit a transition metal thin film on a substrate, and then a titanium dioxide (TiO ₂ ) target is irradiated by a laser beam in a low-pressure oxygen atmosphere. Evaporating and depositing titanium dioxide thin films on the transition metal thin film, and then heating these deposited film layers to a temperature of 500-800 ° C. to thermally diffuse the transition metal into the titanium dioxide thin film,
This is a method for producing a visible light responsive titanium oxide thin film. The visible light responsive titanium oxide thin film obtained in the present invention had a light response wavelength range of 600 to 250 nm.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION For the purpose of imparting visible light responsiveness to the photocatalytic reaction of TiO ₂ , various (V, Cr, Ni, Cu,
Zr, Nb, Mo, Ag, Ta, W)
A sample was prepared by adding it to the O ₂ film by heat treatment.

First, a metal thin film having a thickness of several tens nm is deposited on a smooth single crystal substrate such as Al ₂ O ₃ in a high vacuum (10 ^-6 Torr or more) by a laser vapor deposition method. (10m-100mTorr) at TiO ₂
A thin film is deposited for several hundred nm. Then 500-800
The lower metal layer is diffused into the upper TiO ₂ layer by a heat treatment at about ° C.

[0008] TiO thus diffused various metals
_{2 When} the photoconductive properties of the thin film were measured, Ta, Nb, Cr,
The sample to which Zr and W were added showed a visible light response. Less than,
The present invention will be described based on examples.

FIG. 1 shows that a TiO ₂ film is made of Ta, Nb, Cr,
This is the wavelength dependence of the photoconductive properties of the sample when Zr and W are diffused and the sample containing only TiO ₂ . The sample containing only TiO ₂ has a sharp decrease in photoconductivity from around 400 nm, whereas the sample in which these metals are diffused has a wavelength of 410 nm.
It can be seen that the photoconductor exhibits extremely high photoconductivity even in a long wavelength region around -600 nm.

[0010]

Example 1 A YAG laser (wavelength: 532 nm) having a repetition frequency of 10 Hz and a pulse width of 100 mJ was applied to a metal tantalum (Ta) target placed in a vacuum with a diameter of 1 mJ.
m. 5c from metal Ta target
α-AL ₂ O ₃ (0001) substrate (10
mm × 10 mm).

[0011] Ta of about 10 nm thickness is deposited on the substrate by laser irradiation for 5 minutes, then the target is changed to a titanium oxide target, and the laser irradiation of 1 hour is applied to a thickness of 20 nm.
A TiO ₂ film of about 0 nm was deposited on the Ta film. Further, heat treatment was performed in the air at 800 ° C. for 6 hours to diffuse Ta into the TiO ₂ film.

The wavelength dependence of the photoconductivity of this sample was investigated. As a result, shows an optical response to the vicinity of the incident light 600 nm (figure _{1 "TiO 2 / Ta")} , this region has a band gap is more than 30eV In "TiO ₂ only", in the region where the normal optical response is not observed is there.

[0013]

Example 2 A sample was prepared in the same manner as in Example 1 except that Cr, Ni, Cu, Zr, Nb, Mo, Ag and W were used as the lower metal layer, and the dependency of the photoconductivity on the incident light was measured. It was measured. TiO ₂ thin film having no metal layer at the bottom (“Ti
O ₂ only ") as compared to, of which Nb, Cr, Zr,
In the thin film in which W is diffused, particularly on the long wavelength side (410 to
(600 nm), the photoconductivity increased significantly.

FIG. 1 shows the results. The increase in the photoconductivity is greater than that of TiO ₂ with no added metal at a wavelength of 50 nm.
In nm, they were Nb (about 120,000 times), Cr (about 160,000 times), Zr (2,500 times), and W (880 times).

[0015]

According to the present invention, TiO ₂ which responds to visible light can be expected to have an activity in a visible light region (〜600 nm) in a photocatalytic reaction which originally required ultraviolet light (wavelength of 400 nm or less). This means that, assuming the solar spectrum as the light source, the amount of light available for the reaction will increase dramatically (several tens times or more), meaning that the catalyst efficiency will increase significantly. I have.

[Brief description of the drawings]

BRIEF DESCRIPTION OF DRAWINGS FIG. 1 shows that TiO ₂ film has Ta, Nb, Cr, Z
This is the wavelength dependence of the photoconductive characteristics of the sample when r and W are diffused and the sample containing only TiO ₂ .

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Tetsuya Yamaki 1233 Watanukicho, Takasaki City, Gunma Prefecture Inside the Japan Atomic Energy Research Institute Takasaki Research Institute (72) Inventor Atsumi Miyashita 1233 Watanukicho Takasaki City, Gunma Prefecture Japan Atomic Energy Research Institute Takasaki Research In-house F-term (reference) 4G047 CA05 CA08 CB04 CB09 CC03 CD02 4K029 AA02 BA16 BA48 BB02 BD00 CA01 DB20 GA01

Claims (2)

[Claims] 1. A method for producing a visible light responsive titanium oxide thin film by thermally diffusing a transition metal into a titanium dioxide (TiO ₂ ) thin film formed by a laser vapor deposition method. 2. The method for producing a visible light responsive titanium oxide thin film according to claim 1, wherein said light response wavelength is from 600 to 250 nm.