JP7301340B2 - Manufacturing method of vanadium dioxide thin film - Google Patents

Description

The present invention relates to a method for producing vanadium dioxide thin films.

A vanadium dioxide (VO ₂ ) thin film exhibits a high temperature coefficient of resistance (TCR), and is therefore expected to be applied to bolometers used in infrared thermography and other applications. Methods for forming a thin film of vanadium dioxide in a tetravalent oxidation state include sputtering, chemical vapor deposition (CVD), sol-gel, and organometallic decomposition. Among them, an organic metal decomposition method, a sol-gel method, or a thin film forming technique using these in combination is a simple method of dissolving in an organic solvent, applying, and baking to form a thin film, and includes sputtering and CVD methods. It is widely used because it does not require a large vacuum device.

On the other hand, since vanadium oxide has a stable state of pentavalence, it is difficult to control the valence and to obtain a high-quality VO ₂ thin film. In the organometallic decomposition method, the organometallic material is thermally decomposed by baking it in the air, so vanadium is easily oxidized during baking to form vanadium pentoxide (V ₂ O ₅ ). For this reason, in order to reduce to vanadium dioxide (VO ₂ ) in the organometallic decomposition method, annealing in a reducing atmosphere such as a low oxygen partial pressure or a hydrogen stream is essential after firing.

Examples of reports aimed at improving the quality of VO ₂ thin films include, for example, Non-Patent Document 1, in which a highly oriented vanadium dioxide thin film is grown on a sapphire substrate by a sol-gel method at low pressure in an oxygen atmosphere. is annealed. In this reduction process, a highly oriented VO ₂ phase grows under conditions of 400° C. or higher at 100 mTorr or lower. According to X-ray diffraction (XRD), the films formed _from the solution changed directly to the _VO2 phase without an intermediate phase, and the _Al2O3 ( ₁₀₁₂ ) and _Al2O3 (1010) The surfaces are (100) oriented and (010) oriented, respectively. In both thin films, sudden metal-insulator transition occurs during the process.

Also, a method of growing a VO ₂ thin film on a single crystal silicon substrate by the sol-gel method and performing rapid annealing has been reported (Non-Patent Document 2). Analysis by X-ray photoelectron spectroscopy (XPS), XRD and field-emission scanning electron microscopy (FE-SEM) showed that this _VO thin film had a polycrystalline and dense nanostructure, with a concentration of tetravalent vanadium of is 79.85%. In addition, from the terahertz time domain spectroscopic analysis, the _thin film shows a large transmittance modulation amount of about 81%. Therefore, application to terahertz devices can be expected.

There is also a report that Mo-doped VO ₂ nanowire arrays fabricated by the sol-gel method with melt-quenching exhibit good thermochromic properties (Non-Patent Document 3). The microstructure of such Mo-doped _VO2 nanowire arrays is formed by cleaving lamellar layered oxides along the (001) and (100) orientations with large interplanar spacing. In the method of Non-Patent Document 3, Mo doping collapses the V ⁴⁺ -V ⁴⁺ dimer to destabilize the semiconductor phase and lower the semiconductor-metal transition temperature (Tc) from 62°C to 42°C. . Non-Patent Document 3 discloses that the addition of Mo increases the electron concentration, so that the Fermi level approaches the conduction band, leading to a decrease in the activation energy (Ea) and, in turn, the temperature coefficient of resistance.

4, W- or Ti-doped VO ₂ thin films are grown by a sol-gel method on a sapphire substrate, preferably in the (002) orientation. For the W _- doped VO thin film, its transition behavior is significantly affected, and for the 1.2 atom% W-doped VO _thin film, the insulation resistance is greatly reduced and the transition temperature is lowered to 313 K, whereas the Ti In the doped VO ₂ thin film, even if the doping amount is 20 atom %, the transition temperature changes only slightly at 350K. [4] disclose that the resistance in the metallic state is very high, but shows that the change in resistance at the transition temperature is small.

Non-Patent Document 5 reported that a Si ₃ N ₄ thin film on a Si substrate has a temperature resistance of −2.6% K ⁻¹ by ion beam sputtering at a relatively low growth temperature of 200° C. in an Ar/O ₂ controlled atmosphere. A vanadium oxide thin film with a modulus is formed. According to Non-Patent Document 5, the semiconductor-metal phase transition is not observed in the vanadium oxide thin film until it is heated to 150° C. immediately after growth, and from the results of X-ray diffraction, the main compound of the VO _x thin film is It is vanadium dioxide (VO ₂ (B)) in a stable state and is transformed into a VO _x thin film by post-annealing at 450°C.

Regarding the production of vanadium-titanium oxide thin films by the sol-gel method, Non-Patent Document 6 describes vanadyl isopropoxide (VO(Oi-C ₃ H ₇ ) ₃ ) and titanium isopropoxide (Ti(O- It has been reported that the addition of acetylacetone and acetic acid to a spin-coating solution of iC ₃ H ₇ ) ₄ ) in isopropanol can stabilize the solution. In addition, Non-Patent Document 6 describes that when the vanadium-titanium oxide has a high titanium content, that is, Ti/(V+Ti)=x, when x is 0.60 to 0.67, the thin film becomes blue- It is also disclosed to exhibit a green-yellow two-step electrochromism.

“Highly Oriented VO2 Thin Films Prepared by Sol-Gel Deposition”, Byung-GyuChae, et al., Electrochem. Solid-State Lett. 2006, 9(1), C12-C14 “Giant Phase Transition Properties at Terahertz Range in VO2 Films Deposited by Sol-Gel Method”, Qiwu Shi et al., ACS Appl. Mater. Interfaces 2011, 3(9), 3523-3527 “Electrical Property of Mo-Doped VO2 Nanowire Array Film by Melting-Quenching Sol-GelMethod”, L.Q. Mai et al., J. Phys. Chem. B, 2006, 110(39),19083-19086

“Characteristics of W- and Ti-Doped VO2 Thin Films Prepared by Sol-Gel Method”, B.G. Chae et al., Electrochem. Solid-State Lett. 2008, 11(6), D53-D55 “Low temperature fabrication of vanadium oxide films for uncooled bolometer detectors”, Hongchen Wang et al., Infrared Physics & Technology 2006, 47(3), 273-277 "Preparation of vanadium-titanium oxide thin films by sol-gel method and their electrochromic properties", Nagase et al., Journal of the Ceramic Society of Japan 101 [9] 1032-1037 (1993)

Non-Patent Documents 1 to 4 and 6 all disclose a method of producing a vanadium oxide thin film from a vanadium compound solution using a sol-gel method. However, in these methods, it is necessary to burn excess organic solvents and organic components by heating to remove them from the film. As such, it must be annealed in low-pressure oxygen, low-pressure air, or in the presence of hydrogen to reduce vanadium to tetravalent. Therefore, the methods described in Non-Patent Documents 1 to 4 and 6 require a long number of steps and require a low-pressure atmosphere or a reducing atmosphere, and cannot be said to be industrial.

In particular, in the method of Non-Patent Document 6, in which an alkoxide solution having a small carbon number of about 1 to 3 is applied and baked, vanadyl isopropoxide and titanium isopropoxide have low stability, so that they are oxidized to 5 It is easy to become vanadium valence, and it is difficult to obtain a high-quality vanadium dioxide thin film. Furthermore, when the thin film obtained by the method of Non-Patent Document 6 was retested, it was found that the oxygen content was large and the purity was low. Furthermore, vanadium dioxide has a large resistance value change based on the metal-insulator transition near 65° C., and shows different phase transitions when the temperature is raised and when the temperature is lowered. As a method of canceling the occurrence of such so-called thermal hysteresis, there is a method of partially substituting vanadium dioxide with titanium. It is difficult to obtain a single phase by the organometallic decomposition method in which these metal-containing compounds are mixed.

The present invention has been made in view of such problems in the prior art, and a high-purity vanadium dioxide thin film or a vanadium dioxide thin film doped with a different element such as titanium can be easily and mass-produced by an organometallic decomposition method. It is an object of the present invention to provide a method of manufacturing in a targeted manner.

The method for producing a vanadium dioxide thin film of the present invention comprises a vanadium oxide precursor, at least one stabilizer selected from the group consisting of carboxylic acids having 2 to 10 carbon atoms and β-diketones having 5 to 11 carbon atoms, and , Step 1 of adding a solvent to prepare a raw material solution for forming a vanadium dioxide thin film; and step 3 of performing main firing at 550 to 750° C. in an inert gas atmosphere following step 2.
In step 3, the inert gas is argon, nitrogen, helium or a mixture thereof, and the pressure of the inert gas is preferably 0.2 to 2 atmospheres.
In step 1, it is preferable to further add a titanium compound in an amount of 0.1 to 35 mol % in terms of titanium atoms to the vanadium oxide precursor to the raw material solution for forming a vanadium dioxide thin film.

The raw material for forming a titanium-doped vanadium dioxide thin film of the present invention comprises a vanadium oxide precursor and at least one stabilizer selected from the group consisting of carboxylic acids having 2 to 10 carbon atoms and β-diketones having 5 to 11 carbon atoms. and a titanium compound, and the content of the titanium compound is 0.1 to 35 mol % in terms of titanium atoms with respect to the vanadium oxide precursor.

According to the present invention, in an organometallic decomposition method using a raw material solution containing a specific vanadium oxide precursor as a main component, calcination is performed at 250 to 350 ° C. in an inert atmosphere, and then main calcination is performed in an inert atmosphere. By conducting the treatment at 550 to 650° C. in an atmosphere, the oxidation of vanadium can be suppressed, and a high-purity vanadium dioxide thin film or titanium-doped vanadium dioxide thin film can be produced easily and mass-produced.
According to the present invention, it is possible to provide a raw material for forming a titanium-doped vanadium dioxide thin film that is suitable for the production method described above.

FIG. 1 is an X-ray diffraction measurement chart showing that the vanadium dioxide (VO ₂ ) thin film of Example 1 is a single phase. FIG. 2 is an X-ray diffraction measurement chart showing that the titanium-doped vanadium dioxide thin film of Example 3 is in the V _0.75 Ti _0.25 O ₂ phase. FIG. 3 shows the results of measuring the resistance-temperature characteristics of the thin films of Examples 1-3. FIG. 4 is a diagram showing resistance-temperature characteristics of the thermistor for the thin film of Comparative Example 2. FIG. FIG. 5 shows that when the main sintering in Comparative Example 3 is performed at a pressure of 1.0 Pa, a VO ₂ single-phase thin film is obtained, but when the pressure is higher than that, V ₂ O ₅ , V ₃ O ₇ and V 2 is an X-ray diffraction measurement chart showing that ₆ O ₁₃ is mixed.

The method for producing a vanadium dioxide thin film of the present invention comprises a vanadium oxide precursor, at least one stabilizer selected from the group consisting of carboxylic acids having 2 to 10 carbon atoms and β-diketones having 5 to 11 carbon atoms, and , Step 1 of adding a solvent to prepare a raw material solution for forming a vanadium dioxide thin film (hereinafter also simply referred to as "raw material solution"); It has a step 2 of preliminary firing at 250 to 350° C. and a step 3 of performing main firing at 550 to 750° C. in an inert gas atmosphere following step 2. Hereinafter, embodiments of the present invention will be described in order of manufacturing steps.

In step 1, a stabilizer and a solvent are added to a vanadium oxide precursor to prepare a raw material solution for forming a vanadium dioxide thin film.
Vanadium oxide precursors include, for example, vanadyl methoxide (VO(OCH ₃ ) ₃ ), vanadyl ethoxide (VO(OC ₂ H ₅ ) ₃ ), vanadyl n-propoxide (VO(OC ₃ H ₇ ) ₃ ). , vanadyl isopropoxide (VO(OCH(CH ₃ ) ₂ ) ₃ ), and vanadyl n-butoxide (VO(OC ₄ H ₉ ) ₃ ). Among these, vanadyl n-butoxide (VO(OC ₄ H ₉ ) ₃ ) and vanadyl isopropoxide (VO(OCH(CH ₃ ) ₂ ) ₃ ) are preferred.
These vanadium oxide precursors were used as vanadium dioxide (VO ₂ ) precursors, and in steps 2 and 3, the conditions were adjusted so that the organic components in the raw material solution remained in the thin film without being thermally decomposed. If adjusted, a vanadium dioxide (VO ₂ ) thin film can be crystallized without using low-pressure oxygen, low-pressure atmosphere, or the like. That is, a highly pure _VO2 thin film can be obtained without oxidizing vanadium to pentavalence. Vanadium can exist in different oxidation states of -1, 0, +2, +3, +4 and +5, but the most common compound is vanadium pentoxide (V ₂ O ₅ ). In vanadium pentoxide ( _V2O5 ), vanadium itself exists in _the +5 oxidation state.

A carboxylic acid having 2 to 10 carbon atoms or a β-diketone having 5 to 11 carbon atoms is used as the stabilizer.
As the carboxylic acid having 2 to 10 carbon atoms, either a linear hydrocarbon-based carboxylic acid or a hydrocarbon-based carboxylic acid having a side chain may be used. Examples of linear carboxylic acids include monocarboxylic acids such as acetic acid, propionic acid, butyric acid, pentanoic acid, caproic acid, heptanoic acid, octanoic acid, nonanoic acid and decanoic acid; ethanedioic acid, malonic acid, succinic acid, Dicarboxylic acids such as glutaric acid, adipic acid, heptanedioic acid, octanedioic acid, nonanedioic acid; 1,2,3-propanetricarboxylic acid, 1,3,5-cyclohexanetricarboxylic acid, 1,3,5-benzenetricarboxylic acid tricarboxylic acids such as acids; and tetracarboxylic acids such as ethylenetetracarboxylic acid and 1,2,3,4-butanetetracarboxylic acid. Carboxylic acids with side chains include, for example, octylic acid, isononanoic acid, 4-ethyloctanoic acid, and isocaproic acid.

β-diketones having 5 to 11 carbon atoms include acetylacetone, trifluoroacetylacetone, hexafluoroacetylacetone, benzoylacetone, and dipivaloylmethane. Of these, acetylacetone is preferred.
In the present invention, the carboxylic acid and β-diketone described above may be used alone or in combination of two or more as the vanadium oxide precursor and the stabilizer for the titanium compound described below.
The amount of the stabilizer added is usually 0.5 to 1.5 times the molar amount of the vanadium oxide precursor multiplied by the valence of the metal, preferably 0.5 to 1 It is a double mole.

Solvents include, for example, acetone, isobutyl alcohol, isopropyl alcohol, isopentyl alcohol, ethanol, ethyl ether, ethylene glycol monoethyl ether, ethylene glycol monoethyl ether acetate, ethylene glycol mono-n-butyl ether, ethylene glycol monomethyl ether, n -octane, o-dichlorobenzene, xylene, cresol, chlorobenzene, isobutyl acetate, isopropyl acetate, isopentyl acetate, ethyl acetate, n-butyl acetate, n-propyl acetate, n-pentyl acetate, methyl acetate, cyclohexanol, cyclohexanone, N , N'-dimethylformamide, tetrahydrofuran, 1,1,1-trichloroethane, turpentine oil, toluene, n-hexane, n-heptane, 1-butanol, 2-butanol, mineral spirits, methanol, methyl ethyl ketone, methylcyclohexanol, methyl Organic solvents such as cyclohexanone and methyl-n-butyl ketone are used. Of these, isopropyl alcohol, n-butyl alcohol, ethylene glycol monomethyl ether, n-butyl acetate, and the like are preferred because of their industrial availability, solubility, boiling point, vapor pressure, and the like.

It is preferable to add a titanium compound as a dopant to the raw material solution in addition to the vanadium oxide precursor and the stabilizer. The titanium element has the effect of canceling the thermal hysteresis due to the metal-insulator transition around 65° C. of the vanadium dioxide thin film. In the organometallic decomposition method, in general, when a compound containing a different metal such as titanium is added, it is difficult to obtain a single phase because metal-containing compounds with different thermal stability are mixed, but in the present invention, titanium doping are effective in forming high-purity vanadium dioxide thin films. Therefore, the raw material comprising the vanadium oxide precursor, stabilizer and titanium compound of the present invention is suitable for forming a titanium-doped vanadium dioxide thin film.

Examples of the titanium compound include titanium isopropoxide, titanium tetra-n-butoxide and titanium tetra-n-pentoxide. The titanium compound has the property of forming a Ti ion in the raw material solution and coordinating with a carboxylic acid having 2 to 10 carbon atoms to form a metal-containing chelate ring. The Ti ion can also form a stable chelate compound with a β-diketone having 5 to 11 carbon atoms.
The amount of the titanium compound added is preferably 0.1 to 35 mol %, more preferably 20 to 30 mol %, relative to the vanadium oxide precursor. The amount of addition is the amount in terms of titanium atoms.

In step 2, the raw material solution is applied onto the substrate to form a liquid film, dried, and then calcined at 250 to 350° C. in an inert atmosphere.
The substrate is insoluble in organic solvents and the like and can withstand the temperature of the final baking. Specifically, a glass substrate, a silicon substrate, a sapphire substrate, or the like is used.
Application methods include spin coating, inkjet, casting, dip coating, bar coating, blade coating, roll coating, gravure coating, and spray coating.

After coating the raw material solution on the substrate, the substrate on which the liquid film is formed is dried at room temperature or under heating to volatilize the organic solvent. When drying is performed under heating, the substrate on which the liquid film is formed may be placed on, for example, a hot plate and dried at about 120°C.

Next, the substrate on which the liquid film has been dried is placed in a sintering apparatus equipped with an inert gas supply source for creating an inert atmosphere, and calcined under the conditions of atmospheric pressure and inert atmosphere. The sintering apparatus may be any apparatus that can withstand heating at about 800° C., such as an electric furnace, a tubular furnace, or a heat treatment apparatus.

The inert gas is preferably argon, nitrogen, helium or mixtures thereof.
The calcination temperature is 250 to 350°C, preferably 300°C or less. If the temperature is higher than 350° C., vanadium in the metal organic compound is likely to be oxidized to pentavalence. In that case, in order to reduce vanadium pentoxide (V ₂ O ₅ ), conditions of a reduced-pressure oxygen atmosphere and a reducing atmosphere are required in the main firing of step 3 described later, which cannot be said to be industrial.
The calcination time is usually 5 to 60 minutes, approximately 15 minutes.
By setting the calcination temperature and time within the above ranges, it is possible to suppress the oxidation of vanadium and to allow the organic components in the metal organic compound to remain in the thin film without being thermally decomposed. Therefore, in the main firing of step 3, the vanadium dioxide thin film can be crystallized under atmospheric pressure using an inert atmosphere such as nitrogen and argon without using low-pressure oxygen, low-pressure air, or the like. It is believed that this calcination forms a precursor thin film containing a metal organic compound as a main component.

The thin film formed on the substrate after calcination is usually 0.05 to 0.5 μm thick, preferably 0.1 to 0.2 μm thick. The film thickness may be obtained by applying a required amount of solution and performing temporary baking once, or applying the solution to the substrate, drying, and performing temporary baking until the desired film thickness is obtained. It may be obtained by repeating the process several times. When repeated, it is easy to form a dense thin film with a small crystal grain size, and finally a uniform VO ₂ thin film is easily obtained.

In step 3, following the calcination in step 2, main calcination is performed at 550 to 750° C., preferably 550 to 600° C., in an inert gas atmosphere. If the firing temperature is lower than 550° C., thermal decomposition may not proceed sufficiently. On the other hand, if the main firing temperature exceeds 750° C., the manufacturing cost increases and cannot be said to be industrial. The main firing time is usually 15 minutes to 2 hours.

The same gas as in step 2 is used as the inert gas. However, in step 3, the pressure of the inert gas is preferably 0.2 to 2 atmospheres. By controlling the pressure of the inert gas within the above range, the formation of vanadium pentoxide is suppressed and the remaining organic components are completely thermally decomposed to form a thin film of high-purity vanadium dioxide or titanium-doped vanadium dioxide. can do.

The obtained vanadium dioxide thin film has a temperature coefficient of resistance (TCR) of -4.1%/K at room temperature. The temperature coefficient of resistance (TCR) is the degree of change in resistance value due to temperature expressed in parts per million per 1K. The temperature coefficient of resistance (TCR) of the vanadium dioxide thin film described in Non-Patent Document 5, which reports that it is useful as a heat sensor, is −2.6%/K at room temperature, so the vanadium dioxide thin film according to the present invention is a good quality thin film and is useful for bolometers and heat sensor members.

Also, a titanium-doped vanadium dioxide thin film generally exhibits a large change in resistance at around 65° C. due to metal-insulator transition. On the other hand, in the vanadium dioxide thin film according to the present invention, as shown in FIG. 3, as the amount of titanium doping increases from 10% to 25%, the change in resistance value is suppressed, and thermal hysteresis is eliminated while maintaining large resistance-temperature characteristics. , has excellent linearity. Therefore, using the vanadium dioxide thin film according to the present invention, a sensor useful in a wide temperature range can be produced.

EXAMPLES The present invention will be more specifically described below based on examples, but the present invention is not limited to the following examples.
[Example 1]
7.5 g of octylic acid and 40 g of n-octane were added to 5.0 g of vanadyl normal butoxide, reacted at 120° C. for 2 hours, the by-product was distilled off, and 20.0 g of n-butyl acetate was added to oxidize the mixture. A precursor solution having a concentration of 2% was obtained.
The precursor solution was applied to the substrate by spin coating, dried on a hot plate at 120° C., and then calcined at 300° C. for 15 minutes under 1 atm of nitrogen. The operation of applying the precursor solution on the substrate by spin coating and calcining was repeated to stack 6 calcined layers, and then calcining was performed at 580° C. for 15 minutes under nitrogen.
The obtained thin film was analyzed by an X-ray diffraction method, and a vanadium dioxide single phase was confirmed. The results are shown in FIG.

[Example 2]
7.5 g of octylic acid and 40 g of n-octane were added to 5.0 g of vanadyl normal butoxide and 1.1 g of titanium isopropoxide, and after reacting at 120° C. for 2 hours, the by-product was distilled off, and n-butyl acetate was obtained. 20.0 g was added to obtain a precursor solution doped with 10% titanium (Xm=10%) and having a concentration of 2% in terms of oxide.
The precursor solution was applied to the substrate by spin coating, dried on a hot plate at 120° C., and then calcined at 300° C. for 15 minutes under 1 atm of nitrogen. The operation of coating the precursor solution on the substrate by spin coating and calcining was repeated to stack 6 calcined layers, and then the laminate was calcined at 600° C. for 15 minutes under nitrogen.
The obtained thin film was analyzed by the X-ray diffraction method, and a V _0.9 Ti _0.1 O ₂ phase doped with Ti was confirmed.

[Example 3]
7.5 g of octylic acid and 40 g of n-octane were added to 5.0 g of vanadyl normal butoxide and 2.0 g of titanium isopropoxide, and after reacting at 120° C. for 2 hours, the by-product was distilled off, and n-butyl acetate was obtained. 20.0 g was added to obtain a precursor solution doped with 25% titanium (Xm=25%) and having a concentration of 2% in terms of oxide.
The precursor solution was applied to the substrate by spin coating, dried on a hot plate at 120° C., and then calcined at 300° C. for 15 minutes under 1 atm of nitrogen. The operation of coating the precursor solution on the substrate by spin coating and calcining was repeated to stack 6 calcined layers, and then the laminate was calcined at 600° C. for 15 minutes under nitrogen.
The obtained thin film was analyzed by the X-ray diffraction method, and a V _0.75 Ti _0.25 O ₂ phase doped with Ti was confirmed. The results are shown in FIG.

[Example 4]
The resistance-temperature characteristics of the thin films obtained in Examples 1 to 3 were measured, and the temperature coefficient of resistance (TCR) was calculated. The results are shown in FIG.
As shown in FIG. 3, the temperature coefficient of resistance (TCR) at room temperature (300 K) is -4.1%/K when the titanium doping amount is 0%, -5.2%/K when the titanium doping amount is 10%, and 25 %, it was -5.0%/K. From room temperature to around 40° C., the resistance value does not change significantly with temperature changes, showing a stable resistance-temperature coefficient both when the temperature is increased and when the temperature is decreased. It was also found that when the titanium doping amount is 25%, the thermal hysteresis disappears, the thin film has a substantially linear resistance temperature coefficient, and can be applied from room temperature to 80° C. or higher.

[Comparative Example 1]
5.0 g of vanadyl isopropoxide was dissolved in n-butanol to obtain a precursor solution with a concentration of 2% in terms of oxide.
The precursor solution was applied to the substrate by spin coating, dried on a hot plate at 120° C., and then calcined at 300° C. for 15 minutes under 1 atm of nitrogen. The operation of applying the precursor solution on the substrate by spin coating and calcining was repeated to stack 6 calcined layers, and then calcining was performed at 580° C. for 15 minutes under nitrogen.
When the obtained thin film was analyzed by the X-ray diffraction method, diffraction peaks due to V ₃ O ₇ and V ₆ O ₁₃ were confirmed in addition to VO ₂ .

[Comparative Example 2]
7.5 g of octylic acid and 40 g of n-octane were added to 5.0 g of vanadyl normal butoxide and 1.1 g of titanium isopropoxide, and after reacting at 120° C. for 2 hours, the by-product was distilled off, and n-butyl acetate was obtained. 20.0 g was added to obtain a precursor solution having a concentration of 2% in terms of oxide.
The precursor solution was applied to the substrate by spin coating, dried on a hot plate at 120° C., and then calcined at 400 to 450° C. for 15 minutes under 1 atmosphere of oxygen. The operation of coating the precursor solution on the substrate by spin coating and calcining was repeated to stack 6 calcined layers, and then the laminate was calcined at 600° C. for 15 minutes under nitrogen.
When the obtained thin film was analyzed by the X-ray diffraction method, only V ₂ O ₅ was obtained as shown in FIG. The reason for this is thought to be that the calcination was performed at a high temperature of 400 to 450°C.

[Comparative Example 3]
7.5 g of octylic acid and 40 g of n-octane were added to 5.0 g of vanadyl normal butoxide, reacted at 120° C. for 2 hours, the by-product was distilled off, and 20.0 g of n-butyl acetate was added to oxidize the mixture. A precursor solution having a concentration of 2% was obtained.
The precursor solution was applied to the substrate by a spin coating method, and calcined at 450° C. for 15 minutes under 1 atmosphere of oxygen. After repeating the operation of applying the precursor solution on the substrate by a spin coating method and calcining, and laminating 6 calcined layers, the pressure is changed in the atmosphere, and the main calcination is performed at 600 ° C. for 15 minutes. rice field.
When the obtained thin film was analyzed by the X-ray diffraction method, a VO ₂ single phase was obtained at a pressure of 1.0 Pa, and V ₂ O ₅ , V ₃ O ₇ and V ₆ O ₁₃ were mixed at higher pressures. was The results are shown in FIG.

The vanadium dioxide thin film of the present invention has a temperature coefficient of resistance (TCR) of −4.1%/K when not doped with titanium, and is useful as a bolometer or heat sensor.

Claims (3)

vanadyl methoxide (VO(OCH ₃ ) ₃ ), vanadyl ethoxide (VO(OC ₂ H ₅ ) ₃ ), vanadyl n-propoxide (VO(OC ₃ H ₇ ) ₃ ), vanadyl isopropoxy as vanadium oxide precursors; (VO(OCH(CH ₃ ) ₂ ) ₃ ) or vanadyl n-butoxide (VO(OC ₄ H ₉ ) ₃ ) , a carboxylic acid having 2 to 10 carbon atoms and a β-diketone having 5 to 11 carbon atoms Step 1 of preparing a raw material solution for forming a vanadium dioxide thin film by adding at least one stabilizer and a solvent selected from the group consisting of; Step 2 of forming a film and calcining at 250 to 350° C. under an inert atmosphere; , a method for producing a vanadium dioxide thin film by an organometallic decomposition method . The production of vanadium dioxide thin film according to claim 1, wherein in the step 3, the inert gas is argon, nitrogen, helium or a mixture thereof, and the pressure of the inert gas is 0.2 to 2 atm. Method. 3. The vanadium oxide thin film forming raw material solution in the step 1 further comprises adding a titanium compound in an amount of 0.1 to 35 mol % in terms of titanium atoms with respect to the vanadium oxide precursor. A method for producing a vanadium dioxide thin film according to 1.

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