JPH06107498A - TiO2-SnO2 film manufacturing method and TiO2-SnO2 film coating member - Google Patents

Abstract

(57) [Summary] [Structure] A crystalline substrate 1 such as sapphire with a thickness of 10
The first epitaxial film 2 composed of TiO ₂ and SnO ₂ having a thickness of nm or less is formed, and an alkoxide solution of Ti and Sn is applied to the surface of the first epitaxial film 2 and heat-treated to form TiO ₂ —SnO.
Forming a _second solid solution film 3, further changed to the second epitaxial thin film heat treatment at 1350 ° C. or more, and heat-treated in an oxidizing atmosphere above 800 ° C. Supino - is dull decomposed into TiO ₂ on the surface of the crystalline substrate TiO, which is composed of a layered tissue film in which abundant layers and SnO ₂ rich layers are alternately arranged, and the predetermined crystal axis direction of the crystalline substrate is parallel to the array direction of the layered tissue film.
_{A 2-} SnO ₂ film coated member is obtained. [Effect] TiO ₂ —S with excellent crystallinity by the sol-gel method
An nO ₂ film can be formed, and a functional film having a fine structure can be obtained by spinodal decomposition.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a film made of TiO ₂ and SnO ₂ and a member coated with such a thin film. More specifically, the present invention relates to a film made of a solid solution of TiO ₂ and SnO ₂ or TiO _2. -SnO ₂ Supino - preparation of dull decomposed film, and to a member coated with TiO ₂ -SnO ₂ film.

[0002]

_2. Description of the Related Art Conventionally, TiO ₂ —SnO ₂ type oxides have been attracting attention as a material having functionality by controlling the composition ratio and stoichiometric composition ratio, and recently, Ti
Attempts have been made to further improve the functionality by decomposing the O ₂ —SnO ₂ based oxide by spinodal decomposition to form a fine structure.

Conventionally, an oxide thin film made of a solid solution of TiO ₂ —SnO ₂ system and its spinodal decomposed thin film have been produced by, for example, a sputtering method. For example, the present applicant first evaporates an evaporation substance from an evaporation source composed of TiO ₂ and SnO _2, and simultaneously forms a TiO ₂ —SnO ₂ thin film on a predetermined substrate surface heated to about 300 ° C. or higher. A film made of a solid solution of TiO ₂ and SnO ₂ is obtained by supplying oxygen to the film formation region of the substrate, and the solid solution film is heat-treated in an oxidizing atmosphere at 1350 ° C. or higher to form an epitaxial solid solution thin film. It was proposed that a spinodal-decomposed thin film can be obtained by further heating this epitaxial solid solution thin film at 800 ° C. or higher in an oxidizing atmosphere.

[0004]

However, according to the above-mentioned sputtering method, the composition of the evaporation source and the film composition do not always match, and therefore the composition of the evaporation source and the composition of TiO ₂ ,
It was necessary to control the evaporation amount of each SnO ₂ . Further, it is very difficult to keep the film composition constant due to a change in the composition of the evaporated particles accompanying a change in the surface composition of the evaporation source during film formation, or re-evaporation of the film component from the surface. Furthermore, it was almost impossible to uniformly disperse the trace substance of the dopant substance in the film with high quantitative accuracy.

Therefore, according to the present invention, a novel TiO ₂ —SnO ₂ solid solution thin film having excellent crystallinity and a spinodal decomposed TiO ₂ —SnO ₂ thin film can be produced without using the above-mentioned thin film method. It is an object to provide a method and a covering member.

[0006]

As a result of repeated studies on the above problems, the present inventors first selected a substrate having a crystalline surface as a substrate for film formation, An ultra-thin TiO ₂ —SnO film with a thickness of 10 nm or less was previously formed on the substrate.
₂ After producing an epitaxial thin film, a coating solution prepared from a titanium-containing organic compound and a Sn-containing organic compound is applied onto the epitaxial thin film and heat-treated to obtain a TiO ₂ —SnO ₂ solid solution thin film, Further, it was found that by heat-treating this in an oxidizing atmosphere at 1350 ° C. or higher, the solid solution film is rearranged based on the crystal plane of the ultrathin epitaxial thin film previously formed, and an epitaxial solid solution thin film having excellent crystallinity can be obtained. did.

That is, the method for producing a TiO ₂ —SnO ₂ film of the present invention comprises the first step of forming a first epitaxial thin film of TiO ₂ and SnO ₂ having a thickness of 10 nm or less on the surface of a crystalline substrate, A solution containing a Ti-containing organic compound and a Sn-containing organic compound is applied to the surface of the first epitaxial thin film to thermally decompose the organic compound, and then heat-treated in an oxidizing atmosphere at 800 ° C. or higher to remove TiO ₂ and SnO _2. And a second step of forming a solid solution film comprising: (1) wherein the crystalline substrate is made of sapphire and the thin film forming surface is (011-2).
It consists of the R surface or the (112-0) A surface.

The method further comprises a third step of heat-treating the substrate obtained by the above method in an oxidizing atmosphere at 1350 ° C. or higher to change the solid solution film into a second epitaxial thin film, The obtained substrate is 800
By heating in an oxidizing atmosphere of ℃ or above,
And a fourth step of spinodal decomposition of the epitaxial thin film of 1., whereby a TiO ₂ -rich layer and a SnO ₂ layer are formed on the surface of the crystalline substrate.
A covering member layer to form a layered tissue membranes arranged in alternating rich, the predetermined crystal axis direction and the lamellar structure layer arrangement direction parallel to TiO ₂ -SnO ₂ film-coated member of the crystalline substrate I will get it.

The present invention will be described in detail below with reference to the drawings. FIG. 1 is a sectional view showing a covering member on which a TiO ₂ —SnO ₂ film according to the present invention is formed. In the figure, 1 is a substrate,
2 consists of TiO ₂ -SnO ₂ first epitaxial layer, 3 is a solid solution film or the second epitaxial layer made of TiO ₂ -SnO _2. First, according to the method of the present invention, a crystalline substrate is selected as the substrate 1 on which the TiO ₂ —SnO ₂ film is formed. Further, the substrate 1 is 1350
There is no reaction with the film components by heating above ℃, or the reaction rate is slow even if it reacts, and the film is formed of TiO ₂ —Sn
A substrate having substantially the same lattice arrangement as the specific crystal plane of the O ₂ film is desirable from the viewpoint of the crystallinity of the film, specifically, it is made of sapphire and its thin film forming surface is (011
2) Substrate composed of R-plane or (112-0) A-plane.

Further, the crystallinity of the TiO ₂ —SnO ₂ thin film formed on the surface of the crystalline substrate 1 is easily affected by the wetting angle of the substrate to water, and the wetting angle of the substrate to water is 60 °. It is desirable that the angle is above 70 °.

Next, the method for preparing the coating liquid used in the first and second steps of the manufacturing method of the present invention will be described with reference to specific examples. FIG. 2 is a diagram showing an apparatus for preparing a coating liquid, where 4 is a reaction solution and 6 is a partial hydrolysis solution. Here, as the reaction solution 4, for example, a solution obtained by mixing metal-containing organic compounds of titanium alkoxide and tin alkoxide and dissolving them in an appropriate organic solvent is used.

Specifically, alkoxides include ethoxide, n-propoxide, i-propoxide, n-butoxide, i-butoxide, sec-butoxide, t-butoxide, 2-methoxyethoxide, 2-ethoxyethoxide. Etc., and mixed alkoxides thereof can be used, and as the organic solvent, i-propanol, n-butano-
, I-butanol, sec-butanol, t-butanol, amyl alcohol, 2-methoxyethanol, 2
-Alcohols such as ethoxyethanol, or a mixed solvent of these alcohols and an aromatic compound such as benzene can be used. Further, in order to prevent the formation of precipitates from the solution, monoethanolamine, dietanolamine, triethanolamine, acetylacetate or the like may be added as a stabilizer.

The composition of each alkoxide in the reaction solution 4 can be controlled to a desired ratio according to the function of the film to be formed, but in the case of finally causing spinodal decomposition,
Titanium alkoxide and tin alkoxide are substantially 3: 7.
It is desirable to be 7: 3.

Reaction solution 4 prepared as described above
Is refluxed in the reflux device 5 for about 10 to 30 hours under a dry nitrogen atmosphere, and then the partial hydrolysis solution 6 is slowly added dropwise from the syringe 7 to the reaction solution 4. The solution 6 for partial hydrolysis used here was 0.
It is prepared by diluting 1 to 2 times the number of moles of distilled water with the same solvent as the reaction solution 4, and the same stabilizer used in the reaction solution 4 may be mixed.

This partial hydrolysis is for forming an intermediate having a metal-oxygen-metal metalloxane bond in the coating liquid, and the presence of this intermediate causes TiO _{2 in} the heat treatment process after coating on the substrate. it is aimed at effect of promoting crystallization into -SnO ₂ based oxide.

After the partial hydrolysis solution 6 was dropped, the reaction solution 4 was further refluxed for 10 to 30 hours, cooled to room temperature, and an appropriate amount of the solvent used in the reaction solution 4 was added to adjust the concentration. , A coating solution for forming the TiO ₂ —SnO ₂ solid solution film 3 can be obtained.

The coating solution for forming the first epitaxial film 2 (hereinafter referred to as the pretreatment solution) is
It should be a solution that is diluted 5 to 30 times as much as the above-mentioned coating solution, and that allows a uniform gel film to be distributed over the entire surface of the substrate 1 after coating. As the diluting liquid, methanol, ethanol, benzene, etc., which are compatible with the coating liquid and have a relatively low boiling point, are useful.

According to the present invention, first, as a first step, the above-mentioned pretreatment solution is applied to the surface of the substrate 1 by a dip coating method or a spin coating method so that the thickness after heat treatment is 10 nm or less. To form a gel film. After coating, it is sufficiently dried and heat-treated in an oxidizing atmosphere such as air at 500 to 700 ° C. By this heat treatment, the organic compound in the coating liquid is thermally decomposed to form TiO ₂ and SnO ₂ , and these are solid-solved with each other to form a TiO ₂ —SnO ₂ solid solution film. Since it is very thin, it grows epitaxially based on the crystal plane of the substrate and a film with high crystallinity is formed. The thickness of the film formed in this first step is limited to 10 nm or less because if it is thicker than 10 nm, epitaxial growth based on the crystal plane of the substrate becomes difficult and a film with high crystallinity cannot be obtained.

Next, as a second step, the coating solution prepared as described above is applied to the surface of the first epitaxial film 2 formed in the first step by dip coating method or spin coating method. And the coating is dried by a well-known method. Then, this film is heat-treated in an oxidizing atmosphere at 500 to 700 ° C. to thermally decompose the organic compound in the gel film to form TiO ₂
Forming a -SnO ₂ solid solution film 3. The thickness of the coating liquid at this time is not particularly limited, and in order to increase the thickness, coating-drying-heat treatment may be repeated. The solid solution film thus obtained has very low crystallinity. Therefore, the solid solution film after the thermal decomposition treatment is heated to 800 ° C.
By performing the heat treatment in the above oxidizing atmosphere, it is possible to form a uniform solid solution film 3 having excellent crystallinity.

Next, the Ti obtained by the second step described above
The O ₂ —SnO ₂ solid solution film 3 is uniform and has excellent crystallinity, but the crystal orientation directions are not sufficiently aligned. Therefore, according to the present invention, as the third step, the first epitaxial film 2 obtained by the second step and TiO ₂ —S are obtained.
Crystal rearrangement can be performed by heat-treating the substrate 1 on which the nO ₂ solid solution film 3 is laminated in an oxidizing atmosphere at 1350 ° C. or higher, particularly 1400 to 1500 ° C.

FIG. 3 is an X-ray diffraction measurement chart when a TiO ₂ —SnO ₂ solid solution film formed on a sapphire substrate having an R surface with a surface of (012) is heat-treated in an oxygen stream at 800 ° C. or higher. 4 is an X-ray diffraction measurement chart when the solid solution film was heat-treated at 1350 ° C. or higher. As is clear from the comparison between the two charts, the crystallinity and orientation of the solid solution film are improved due to the rearrangement of crystals. Further, when sapphire having a (011-2) R-plane or a (112-0) A-plane as the substrate is used, as is clear from FIG. 7 which illustrates the crystal axis of the film, the solid solution film 3 It is confirmed that the a-axis direction is parallel to the a-axis direction of the substrate.

Incidentally, TiO ₂ is usually mixed with Al ₂ O ₃ and 120
Since the reaction easily occurs at about 0 ° C., it is necessary for this heat treatment to rearrange the crystals while suppressing the reaction of TiO _{2 with} the sapphire substrate. For that purpose, the heat treatment within the above temperature range is required. It is desirable that the time is 10 seconds to 5 minutes. If the heat treatment temperature in this third step is lower than 1350 ° C., rearrangement of crystals does not occur, and it is impossible to obtain a solid solution epitaxial film.

Next, the Ti obtained by the above third step
800 to 1200 ° C. for the O ₂ —SnO ₂ solid solution film
By heat treatment for 5 minutes to 100 hours in an oxidizing atmosphere such as the atmosphere, spinodal decomposition is caused in the epitaxial film of TiO ₂ —SnO ₂ . If the temperature of this heat treatment is lower than 800 ° C., spinodal decomposition does not substantially occur. On the contrary, if the temperature is higher than 1200 ° C., the TiO ₂ —SnO ₂ film causes a solid phase reaction with the substrate, which is not desirable.

This spinodal decomposition occurs preferentially in the c-axis direction of the crystal, and as a result, for example, the (011-2) R-plane or (112-0) of sapphire is used as the substrate.
In the case of using the A surface of Ti, as shown in the schematic view of FIG.
A layered tissue film 10 in which O ₂ -rich layers 8 and SnO ₂ -rich layers 9 are alternately arranged is formed. Thereby, the board 1
It is possible to produce a TiO ₂ —SnO ₂ film having a fine structure that is substantially parallel to the arrangement direction of the a-axis and the layered tissue film, that is, the a-axis direction of the film. The arrangement direction of the layered tissue membrane is
It is in the same direction as the a-axis of the crystal of the spinodal decomposition film.

TiO ₂ --Sn obtained as described above
Since the O ₂ spinodal decomposition film has a fine layered structure, it can be expected to have various uses as a functional film for various sensors.

[0026]

According to the present invention, an organic solution containing a titanium-containing organic compound such as titanium alkoxide and tin alkoxide and a tin-containing organic compound is used to produce TiO ₂ --S.
In forming the nO ₂ film, even if a large amount of TiO ₂ —SnO ₂ film is directly formed on the surface of the substrate by applying a large amount of the above organic solution to the substrate and performing heat treatment, a film having high crystallinity and orientation is obtained. Hard to get. This is because when the lattice shift between the substrate and the thin film is relatively large, even if the thick film is crystallized at one time, the atomic arrangement information on the substrate surface cannot be transmitted to the entire film.

The present inventors have found that TiO ₂ --S having high crystallinity is used.
The nO ₂ film is formed by focusing on the fact that a crystalline substrate is used, an extremely thin film is formed on the surface of the crystalline substrate, and heat treatment is performed, and an extremely thin TiO ₂ —SnO ₂ film is previously formed on the surface of the crystalline substrate.
After the epitaxial film is formed, a thick TiO ₂ —SnO ₂ film is formed by a normal method and heat-treated to improve the crystallinity of the thick TiO ₂ —SnO ₂ film, resulting in a uniform and crystalline film. A high film can be obtained.
Further, by selecting a specific surface of sapphire as the substrate and forming it on the surface, an epitaxial thin film having (101) preferential orientation can be formed.

Further, by heat-treating such a film to cause spinodal decomposition, a layer rich in TiO ₂ and SnO _{2 are formed.}
It is possible to form a film having a layered structure in which rich layers are alternately arranged and in which the predetermined crystal axis direction of the crystalline substrate is parallel to the array direction of the layered structure film.

The film obtained by the present invention reflects the crystal plane of the substrate and is a film having excellent regularity, and therefore the application of the spinodal decomposition film as a functional film to a sensor or the like is further promoted.

[0030]

Example: In a dry glove box, 10 mmol of tetraisopropoxytitanium and 10 mmol of tetraisopropoxytin were added to 400 mmol of 2-methoxyethanol.
1 was added to prepare a uniform reaction solution 4. Then, this solution 4 was taken out from the glove box, put into a flask equipped with a reflux condenser 5 as shown in FIG. 2, and refluxed in a dry air stream for 24 hours. Then, 40 mmol of diethylamine prepared in advance and 40 mmol of distilled water
A solution for partial hydrolysis 6 consisting of 100 mmol of 2-methoxyethanol and 100 mmol of 2-methoxyethanol was slowly dropped into the above-mentioned solution 4 using a syringe 7, and then refluxed for 20 hours. After cooling to room temperature, the concentration was adjusted by adding 2-methoxyethanol in an amount corresponding to the volatilized solvent,
A coating solution was prepared.

A pretreatment solution was prepared in the same manner as the above coating solution. That is, in a dry glove box, to 1 mmol of tetraisopropoxy titanium and 1 mmol of tetraisopropoxy tin, 2-methoxyethanol-
80 mmol was added to prepare a uniform reaction solution 4, and the mixture was refluxed in a dry air stream for 24 hours. Then, the solution 6 for partial hydrolysis, which was prepared in advance and consisted of 1 mmol of distilled water and 20 mmol of 2-methoxyethanol, was slowly added dropwise to the above-mentioned solution, and then refluxed for 20 hours. After cooling to room temperature, 2-methoxyethanol in an amount corresponding to the volatilized solvent was added to adjust the concentration, and then 9 times the total weight of methanol was added to prepare a pretreatment solution.

On the other hand, the substrate has a wetting angle of 75 on water.
(011 ￣
2) The R surface was immersed in benzene, ultrasonically cleaned at 30 ° C. for 10 minutes, and dried.

(First step) This substrate is 15 mm × 1
It was cut into 5 mm, immersed in the above-mentioned pretreatment solution in a dry glove box, pulled up at a constant speed of 1.5 mm / sec, and then dried for 30 minutes. Continuously 700 ° C in oxygen stream
In and baked for one hour, the thickness of 10nm or less of the very thin TiO ₂ -
A SnO ₂ thin film was prepared. From the RHEED analysis of the obtained thin film, it was found that a (101) epitaxial thin film was produced.

(Second Step) Next, this substrate was immersed in a coating solution, pulled up at a constant rate of 1.5 mm / sec, dried for 30 minutes, and then heat-treated in an oxygen stream at 600 ° C. for 1 hour,
A TiO ₂ —SnO ₂ thin film was prepared. Immersion-drying-heat treatment was repeated 3 times to increase the film thickness. The obtained thin film is baked at 900 ° C. for 1 hour, and X-ray diffraction measurement (XRD analysis) is performed.
The results of the above are shown in FIG. XRD analysis showed that this thin film was a solid solution in which (101) was preferentially oriented, but RHEED analysis showed that its crystallinity and orientation were very low. From SEM observation, it was also found that the film was a dense thin film having a film thickness of 120 nm and having a smooth surface and no columnar structure or cracks.

(Third Step) Further, this thin film was heat-treated in an oxygen stream at 1450 ° C. for 1 minute and quenched in the atmosphere, and then XRD analysis was performed. The results are shown in Fig. 4. XR
From the results of D analysis, it was found that this heat treatment causes rearrangement of crystals, resulting in extremely high crystallinity and orientation of the film. Further, from the result of RHEED analysis, it was confirmed that the solid solution film was an epitaxial film in which the a-axis and the a-axis of the substrate were in the same direction.

(Fourth step) Next, when the obtained epitaxial film is heated at 900 ° C., as shown in FIG. 5, the satellite peak peculiar to the spinodal decomposition is shown in the (101) XRD analysis chart as time passes. -Ku appeared. Furthermore, FIG.
From the copy of the TEM photograph of the thin film after heating for 50 minutes, the layered structure (lamellar structure) at intervals of approximately 6 nm was
It was observed that the films were formed in the same direction all over the thin film. As a result of electron beam diffraction, as shown in the schematic view of FIG. 8, it was confirmed that the arrangement direction of the layered structure was parallel to the a-axis of the substrate. When each layer was analyzed by EDS (energy-dispersive X-ray analysis), it was found that the white portion in FIG. 6 was rich in TiO ₂ and the black portion was rich in SnO ₂ . . From the results of these XRD analysis and TEM observation, the TiO ₂ —SnO ₂ epitaxial thin film prepared according to the present invention is rich in TiO ₂ in parallel with the a-axis of the sapphire substrate by spinodal decomposition as shown in FIG. Layer and S
It was found that the film was a fine structure having a layered structure in which nO ₂ -rich layers were alternately arranged.

[0037]

As described in detail above, according to the method of the present invention, a solid solution film of TiO ₂ —SnO ₂ having excellent crystallinity can be formed by a so-called sol-gel method, and further, an epitaxial film can be formed by a specific heat treatment. Can be formed. Moreover, by spinodal decomposition of this, it is composed of a fine layered structure and reflects the crystal plane of the substrate, and it is a film with excellent regularity, so its practical application as a sensor element or other functional oxide film should be promoted. You can

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing the structure of a TiO ₂ —SnO ₂ film according to the present invention.

FIG. 2 is a schematic view of an apparatus for preparing a coating liquid used in the present invention.

FIG. 3 is an X-ray diffraction chart of a TiO ₂ —SnO ₂ solid solution film after the second step.

FIG. 4 is an X-ray diffraction chart of a TiO ₂ —SnO ₂ solid solution film after the third step.

FIG. 5 is a diagram showing changes in an X-ray diffraction chart with respect to time during spinodal decomposition treatment at 900 ° C.

FIG. 6 is a copy of a TEM photograph of a TiO ₂ —SnO ₂ film after spinodal decomposition.

FIG. 7 is a diagram for explaining crystal axes of a solid solution film.

FIG. 8 is a diagram for explaining the structure of a TiO ₂ —SnO ₂ film after spinodal decomposition.

[Explanation of symbols]

1 substrate 2 first epitaxial layer 3 TiO ₂ -SnO ₂ solid solution film 8 rich layer to layer 9 SnO ₂ rich TiO ₂

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification number Reference number within the agency FI technical display location C30B 29/16 7821-4G (72) Inventor Naoken Nagaka 3 Kyo, 999, Hayato-cho, Aira-gun, Kagoshima Cera Co., Ltd. Hayato factory (72) Inventor Shinichi Hirano 3-2 Maruikedai, Morokawa, Higashiura-machi, Chita-gun, Aichi

Claims (6)

[Claims] 1. A Ti substrate having a thickness of 10 nm or less on the surface of a crystalline substrate.
A first step of forming a first epitaxial thin film composed of O ₂ and SnO ₂ ; and applying a solution containing a Ti-containing organic compound and a Sn-containing organic compound on the surface of the first epitaxial thin film to form the organic compound. A second step of forming a solid solution film composed of TiO ₂ and SnO ₂ by heat treatment in an oxidizing atmosphere at 800 ° C. or higher after thermal decomposition, TiO ₂ —SnO ₂
Membrane manufacturing method. 2. The crystalline substrate is made of sapphire, and its thin film formation surface is a (011_2) R plane or a (112) plane.
0) TiO ₂ —SnO _{2 according} to claim 1, which is composed of the A surface.
Membrane manufacturing method. 3. A Ti substrate having a thickness of 10 nm or less on the surface of the crystalline substrate.
A first step of forming a first epitaxial thin film composed of O ₂ and SnO ₂ ; and applying a solution containing a Ti-containing organic compound and a Sn-containing organic compound to the surface of the first epitaxial thin film to form the organic compound. After thermal decomposition, heat treatment is performed in an oxidizing atmosphere at 800 ° C. or higher to form a solid solution film of TiO ₂ and SnO _2, and the substrate obtained by the second process is oxidized at 1350 ° C. or higher. A third step of converting the solid solution film into a second epitaxial thin film by heat treatment in a strong atmosphere.
Manufacturing method of iO ₂ -SnO ₂ film. 4. A Ti substrate having a thickness of 10 nm or less on the surface of the crystalline substrate.
A first step of forming a first epitaxial thin film composed of O ₂ and SnO ₂ ; and applying a solution containing a Ti-containing organic compound and a Sn-containing organic compound to the surface of the first epitaxial thin film to form the organic compound. After thermal decomposition, heat treatment is performed in an oxidizing atmosphere at 800 ° C. or higher to form a solid solution film of TiO ₂ and SnO _2, and the substrate obtained by the second process is oxidized at 1350 ° C. or higher. A third step of converting the solid solution film into a second epitaxial thin film by heat treatment in an oxidizing atmosphere, and heating the substrate obtained in the third step at 800 ° C. or higher in an oxidizing atmosphere,
TiO ₂ —S comprising a fourth step of decomposing the first and second epitaxial thin films by spinodal decomposition.
Manufacturing method of nO ₂ film. 5. A TiO ₂ -rich layer on the surface of a crystalline substrate,
A covering member having a layered tissue film in which SnO ₂ -rich layers are alternately arranged, wherein a predetermined crystal axis direction of the crystalline substrate and an array direction of the layered tissue film are substantially parallel to each other. TiO ₂ —SnO ₂ film coated member. 6. The TiO ₂ —SnO ₂ film coating member according to claim 6, wherein the crystalline substrate is made of sapphire, and the a-axis direction of the sapphire and the arrangement direction of the layered texture film are parallel to each other.