JP2735147B2 - Manufacturing method of thermochromic material - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a material technology for controlling sunlight energy and infrared transmittance, and more particularly, to a novel production of a thermochromic thin film material which automatically adjusts light according to environmental temperature. It is about the method.

[0002]

2. Description of the Related Art A thermochromic (TC) phenomenon is a phenomenon in which optical characteristics such as transmittance and reflectance are reversibly changed by a change in temperature. If a TC material having such thermochromic properties is used, for example, as a window coating material, incident solar energy can be automatically controlled according to the environmental temperature, and a comfortable living space can be secured, and at the same time, the cooling load can be reduced. In recent years,
Various studies on such “smart window coating materials” have been conducted [eg, 1) CG Granqvist:
Materials Science for Solar Energy Conversion Sys
tems, ed. Granqvist (Pergamon Press. (1991), 2)
CG Granqvist: Thin Solid Films 193/194 (1990) 73
0, 3) GV Jorgenson and JC Lee: Sol. Energy Mat
er. 14 (1986) 205, 4) SM Babulanam, TS Eriksso
n, GA Niklasson and CG Granqvist: Sol. Energy
Mater. 16 (1987) 347, 5) KA Khan, GA Niklasso
n and CG Granqvist: J. Appl. Phys. 64 (1988) 332
7, 6) KA Khan and CG Granqvist: Appl. Phys. Le
tt. 55 (1989) 4, 7) SJ Jiang, CB Ye, MSR Kh
an and CG Granqvist: Appl. Opt. 30 (1991) 84
7].

[0003] Also, some transition metal oxides are known to exhibit thermochromic properties. In particular, vanadium dioxide is well known to exhibit thermochromic properties. In the crystal of vanadium dioxide, a semiconductor-metal phase transition occurs reversibly at 68 ° C., and the infrared transmittance greatly decreases as the temperature rises. Further, vanadium of vanadium dioxide is replaced with another metal (W, Mo, Nb, Ta, Re, etc.)
Since the transition temperature can be lowered by substituting with oxygen or by substituting oxygen with fluorine, etc., apply a vanadium dioxide thin film having a transition temperature near room temperature as a dimmer for automatic control of solar energy. (E.g., CG Granqvist; Thin Solid Fil
ms 193/194 (1990) 730].

However, there is very little knowledge about the formation of a vanadium dioxide thin film for controlling solar energy that can be put to practical use, and an effective metal addition method for lowering the transition temperature has not yet been established. is there.
Regarding conventional metal addition methods, for example, examples of addition by ion beam sputtering and [G. Jorgenson et al, Solar Ener
gy Materials 14 (1986) 205], sputtering with a tungsten plate placed on a vanadium target (M. Fukum
a et al, Applied Optics 22 (1983) 265), there were examples of tungsten addition, but the addition amount range was very narrow, and uniformity of the composition of the thin film and precise control of the addition amount were not possible. There was a problem.

[0005]

Under such circumstances, the present inventors have been able to precisely set the transition temperature and to add a new metal additive capable of reliably solving the above problems. As a result of intensive research with the aim of establishing a method, it was found that the intended purpose could be achieved by producing a tungsten-doped vanadium dioxide thin film by reactive binary simultaneous sputtering, etc., and completed the present invention. I came to.

An object of the present invention is to establish an effective metal addition method for lowering the transition temperature.

Another object of the present invention is to provide a method for producing a thermochromic material whose transition temperature can be precisely set by such a metal addition method.

[0008]

According to the present invention, a vanadium target and a tungsten target are subjected to reactive dual-target sputtering.
V _1-x W _x O ₂ (x = _x) showing a phase transition between −81 ° C. and 67 ° C. and having a freely and precisely set transition temperature.
(0.0004 to 0.066) to achieve the production of a thermochromic material having a composition, or -81 by reactively sputtering a vanadium tungsten alloy target containing 0.04 to 10 atomic% of tungsten. V _1-x W _x O ₂ (x = 0.0004 to 0.04) which shows a phase transition between 0 ° C. and 67 ° C. and has a specific transition temperature.
66) To achieve the production of a thermochromic material having a composition.

In the present invention, with regard to the reactive binary simultaneous sputtering method, a vanadium target is reactively sputtered in an argon gas containing oxygen using a multi-component simultaneous sputtering apparatus to produce a vanadium dioxide thin film. In addition, a method of adding tungsten by sputtering tungsten metal as another target is used. The atoms of the additive metal sputtered in this way substitute for some of the vanadium atoms and enter the crystal lattice of the vanadium dioxide thin film deposited on the substrate. In this case, in order to form a single crystal phase of vanadium dioxide, the total pressure is 0.5 to 5 Pa,
Substrate temperature 250-500 ° C, applied power 2.5-15W /
cm ² , and in particular, it is important to precisely control the oxygen gas ratio according to the electric power. The amount of tungsten added is controlled by adjusting the power applied to the tungsten target in the range of 0 to 15% of that of vanadium.

The addition of tungsten changes the conditions for forming a single-phase vanadium dioxide thin film, but it is possible to produce a single-phase thin film by precisely adjusting the oxygen ratio and the like. According to the results of repeated experiments by the present inventors, the formation of a monoclinic vanadium dioxide single phase can be achieved only in an extremely narrow oxygen flow rate region of about 2.7% at an applied power of 10 W / cm ^2. It turned out to be impossible (Fig. 1). In addition, the rotation of the substrate makes it possible to guarantee the uniformity of the formed film.

In the present invention, tungsten is used in an amount of 0.04.
When using a vanadium alloy target containing 10 to 10 atomic%, the total pressure is 0.5 to 5 Pa by reactive sputtering of the vanadium alloy target.
Substrate temperature 250-500 ° C, applied power 2.5-15W /
cm ^2, in particular, by precisely controlling the oxygen gas ratio corresponding to the power, having a specific transition temperature between -81 ° C. to 67 ° C., a homogeneous V which corresponds well with the target composition
_{A 1-x} W _x O ₂ (x = 0.0004 to 0.066) thin film is produced.

In the present invention, the crystal phase of the thin film produced as described above was identified by thin film X-ray diffraction (XRD). The composition and the amount of addition were precisely measured by Rutherford backscattering spectroscopy (RBS). Then, by using a spectrophotometer, the transmittance at a certain wavelength within a wavelength region in which the thin film shows relatively sharp dimming property when the temperature is raised is obtained.
The temperature change curve was recorded, and the temperature at the midpoint of the temperature change curve was defined as the transition temperature. The transition temperature can also be defined as the temperature at the midpoint of the electric conductivity-temperature change curve at the time of temperature rise.

The above V _{1 -x} W _x O ₂ (x = 0.0004-
0.066) With respect to the thin film, the relationship between the amount of tungsten added and the temperature drop was precisely determined.
It has been found that a linear temperature drop occurs at a rate of about 24 ° C. with respect to the amount of tungsten added to zero. -81 ° C
The transition temperature is arbitrarily set at a ratio of about 24 ° C./atomic% tungsten by controlling the amount of tungsten added between ６７67 ° C.

With respect to the composition V _{1 -x} W _x O ₂ , when the amount of tungsten added is x ≦ 0.066, dimming is observed together with phase transition, but when x> 0.066, no phase transition is observed. No dimming property is shown.

V _{1 -x} W _x O ₂ (x = 0.004 to 0.06) for use as a dimmer for automatic control of solar energy
6) For the thin film, the optimal thickness is 50 nm to 100 n
m. It goes without saying that the thermochromic material produced by the present invention can be appropriately changed to an optimum film thickness depending on the purpose.

V _{1 -x} W _x O ₂ (x = 0.0004 to
0.066) The thermochromic material can be further coated with a protective film for protecting the thermochromic material having the composition or a thin film for improving the light control performance, for example, an antireflection film.

As described above, in the present invention, by precisely controlling the sputtering conditions, in particular, the oxygen ratio,
It has been found that a monoclinic vanadium dioxide single phase film can be formed. In addition, by adjusting the power applied to the tungsten target, an addition amount corresponding to the power can be obtained, or by using a target of a vanadium tungsten alloy containing a specific amount of tungsten, an addition amount corresponding to the composition of the alloy target can be obtained. It was found that the amount was obtained. Further, by adding tungsten, about 2
It has been found that a transition temperature of 4 ° C./atomic% tungsten can be reduced.

As described above, the material produced by the production method of the present invention exhibits excellent thermochromic properties. In addition, by precisely controlling the applied power and the flow rate of oxygen, the transition temperature can be reduced. Since it is possible to arbitrarily adjust and set between -81 ° C and 67 ° C,
For example, it can be applied in an extremely wide range as a dimmer for automatic control of various types of solar energy, such as window coating materials, which has been difficult to put into practical use in the past. .

[0019]

Next, the present invention will be specifically described based on examples. Example 1 Sputter deposition was performed by a reactive binary simultaneous sputtering method using a reactive magnetron sputtering apparatus. The apparatus is provided with two targets, and each of the targets can be arbitrarily controlled with a high-frequency power supply or a DC power supply. The water-cooled target has a purity of 9
A 9.9% metal plate having a diameter of 50 mm was used, and the distance from the substrate was kept at 100 mm. Glass and silicon single crystal were used for the substrate according to the purpose. For heating the substrate, S
By using an iC heater, heating to 800 ° C. was possible even in an atmosphere containing oxygen. 1 × 10 ^-4 vacuum system
After evacuation to below Pa and pre-sputtering with argon gas, argon and oxygen are introduced at a predetermined ratio by an independent mass flow controller, and the main sputtering conditions such as total pressure, oxygen flow rate ratio, substrate temperature and applied power While controlling
Reactive sputtering was performed.

That is, a diameter of 50 mm and a purity of 99.9%
Tungsten target of the same standard as the vanadium target of above, in argon gas containing 2.7% oxygen,
Sputtering was performed at a substrate temperature of 400 ° C. and a total pressure of 1.5 Pa. By applying RF power of 200 W to the vanadium target and 4.0 W to the tungsten target, a thickness of 58 nm deposited on glass and silicon substrates
A thermochromic material having a composition of V _0.986 W _0.014 O ₂ and a transition temperature of 37 ° C. was obtained.

FIG. 2 shows the transmittance and reflectance spectra of the obtained V _0.986 W _0.014 O ₂ thermochromic material.
The transition temperature of the thin film became 37 ° C. by adding 1.4 atomic% of tungsten. At a temperature lower than the transition temperature (20 ° C.), the semiconductor characteristics such as a high transmittance, particularly an infrared transmittance, were exhibited.
° C), showing metallic properties, and the infrared transmittance was greatly reduced.
Further, the visible light transmittance hardly changed during the transition, that is, a very useful characteristic was exhibited from a practical viewpoint that the color did not change visually.

Example 2 Preparation of Thermochromic Material by Reactive Sputtering of Alloy Target By a reactive sputtering method of an alloy target, a vanadium tungsten alloy target containing 1.7 atomic% of tungsten was subjected to RF power 200 W, total pressure 1.
Sputtering was performed under the conditions of 5 Pa, a substrate temperature of 400 ° C., and an oxygen ratio of 2.7%. It consists of an 80 nm thick film deposited on glass and silicon substrates and has a composition of V _0.984 W
_A thermochromic material having a property of _0.016 O ₂ and a transition temperature of 30 ° C. was obtained.

COMPARATIVE EXAMPLE 1 In Example 1, the reactive sputtering method was performed using only the vanadium target.
W, total pressure 1.5 Pa, substrate temperature 400 ° C., oxygen ratio 2.
Under a condition of 7%, a single-phase vanadium dioxide film having a thickness of 65 nm was deposited on a glass and silicon substrate. The resulting vanadium dioxide single phase film has a transition temperature of 68 ° C.
Met.

Comparative Example 2 In the above Comparative Example 1, when the substrate temperature was set to 200 ° C. or the total pressure was set to 6 Pa, a mixed phase of oxides was observed in the formation of the single-phase vanadium dioxide thin film. No formation of a single phase of vanadium dioxide was observed.

As described above, the present invention has been described based on the embodiments. However, the present invention is not limited to the above-described embodiments, and may be implemented in any way unless the configuration described in the claims is changed. It goes without saying that it can be done.

[0026]

As described above, according to the present invention, a target of vanadium and tungsten is sputtered by a reactive binary simultaneous sputtering method, and a target of vanadium tungsten alloy is sputtered by a reactive sputtering method. The present invention relates to a method for producing a thermochromic material, and according to the present invention, a vanadium dioxide thermochromic light control material to which tungsten is added has a transition temperature of -81 to 67 by a reliable metal addition method.
It can be freely adjusted and set between ° C. In addition, because the solar energy transmittance and infrared transmittance can be automatically controlled according to the environmental temperature, the infrared transmittance can be controlled in addition to coatings for building windows, automotive windows, and greenhouse windows. For various applications that need to be controlled automatically by temperature changes,
It is expected to be used in a wide range of fields.

[Brief description of the drawings]

FIG. 1 shows main crystal phases of a thin film formed on a silicon substrate by changing a substrate temperature and an oxygen flow rate.

FIG. 2 shows V _{1 -x} W _x O ₂ produced according to an embodiment of the present invention.
(X = 0.014) shows the transmittance and reflectance spectra of the thin film.

Claims (4)

(57) [Claims] 1. A vanadium target and a tungsten target
Get, Substrate temperature 250 ~ 500 ℃, total pressure 0.5 ~
5Pa, applied power 2.5-15W / cm ² And the oxygen ratio
With precise controlSpecially for reactive binary simultaneous sputtering
SignShows a phase transition between −81 ° C. to 67 ° C. and transition temperature
V whose degree can be set arbitrarily and precisely _1-x W _x O
₂ (X = 0.0004 to 0.066) with compositionThermo
A method for producing a chromic material. 2. The method for producing a thermochromic material according to claim 1, wherein the power applied to the tungsten target is in the range of 0 to 15% of the power applied to the vanadium target. Wherein the target vanadium tungsten alloy containing 0.04 to 10 atomic% tungsten, group
Plate temperature 250-500 ° C, total pressure 0.5-5Pa, applied voltage
With a power of 2.5 to 15 W / cm ² , the oxygen ratio is precisely controlled.
Characterized by reactive sputtering Te -81 ° C. to 67
Shows a phase transition between ℃ and arbitrarily and precisely
V _1−x W _x O _{2 that} can be set (x = 0.004 to 0.
066) A method for producing a thermochromic material having a composition . 4. The method for producing a thermochromic material according to claim 1 , wherein the total sputtering pressure during the reactive sputtering is about 1.5 Pa, and the oxygen ratio is about 2.7. .