JP2000281346A - Uv-transparent electric conductor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a UV-transparent electric conductor having a transmission region extended to a UV region by using a material having a perovskite crystal structure or a material having an Na-site-defective perovskite crystal structure. SOLUTION: This transparent electric conductor consists of a material that has a perovskite crystal structure and is represented by the compositional formula RMoO3 (wherein R is Ca, Sr or Ba) or another material that has an Na-site- defective perovskite crystal structure and is represented by the compositional formula NaxWO3 (wherein 0.3<=x<=1). The transparent conductor can be produced by forming such a material on a substrate by using a radio-frequency magnetron sputtering method, vacuum deposition method, or the like. For example, the conditions for production of such a conductor consisting of SrMoO3 by a radio-frequency magnetron sputtering method are as follows: the target consists of an SrO-Mo mixture; the substrate consists of SiO2 glass; the gas pressure is 6×10-3 Torr; the gas composition consists of 95% of argon and 5% of hydrogen; and the radio-frequency power is 50 W. The conditions for production of such a conductor consisting of NaxWO3 by a vacuum deposition method are as follows: the raw material is an Na2CO3-WO3 sintered mixture placed in a tungsten boat; and the substrate consists of SiO2 glass.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultraviolet transparent electric conductor made of an oxide material having a high electric conductivity and capable of transmitting ultraviolet light in a range of 3 to 4 eV.

[0002]

2. Description of the Related Art Conventionally, indium oxide, tin dioxide, zinc oxide and the like have been widely used as transparent conductive thin film materials. Each of these materials has a light transmission region substantially matching the photon energy (1.6-3.2 eV) in the visible region, and a typical value of the electric conductivity is 10 ³ Scm ⁻¹ . However, these materials have a problem that the transmittance of ultraviolet light (3-4 eV) is low.

[0003] In order to shorten the transmission wavelength, tin-substituted indium oxide obtained by introducing a large amount of tin into indium oxide is used. However, also in this material, the upper limit of the transmission region is about 3.5 eV.

[0004]

SUMMARY OF THE INVENTION Accordingly, it is a main object of the present invention to provide a transparent conductive material whose transmission region is extended to an ultraviolet region.

[0005]

Means for Solving the Problems The present inventor has conducted research in view of the state of the art as described above, and as a result, the metal oxide thin film represented by a specific composition formula has been found to be in the ultraviolet region of 3 to 4 eV. They have found that they can transmit light and have high electrical conductivity.

That is, the present invention provides the following ultraviolet light transparent electric conductor: An ultraviolet light transparent electric conductor comprising a perovskite-type crystal structure material represented by a composition formula RMoO ₃ (1) (R is at least one of Ca, Sr and Ba). 2. An ultraviolet-light transparent electric conductor comprising a Na-site-deficient perovskite-type crystal structure material represented by the composition formula Na _x WO ₃ (2) (where 0.3 ≦ x ≦ 1).

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION An ultraviolet transparent electric conductor according to the present invention comprises a perovskite-type crystal structure material represented by a composition formula RMoO ₃ and a Na-site-deficient perovskite-type crystal structure material represented by a composition formula Na _x WO _3. .

In the material of the present invention represented by the composition formula RMoO ₃ (1), R is at least one of Ca, Sr and Ba;
Its crystal structure is perovskite type.

Further, also in the material of the present invention represented by the composition formula Na _x WO ₃ (2), the crystal structure is a Na site-deficient perovskite type.

The method for producing the perovskite-type crystal structure material or the Na-site-deficient perovskite-type crystal structure material represented by the above-mentioned composition formulas (1) and (2) is not particularly limited, and may be selected according to the intended use or form. It can be appropriately manufactured by a known high-frequency magnetron sputtering method, vacuum evaporation method, or the like. Irrespective of the difference in the production conditions, the ultraviolet light transparent electric conductor of the present invention can be obtained as long as it has the above composition and crystal structure.

More specifically, for example, Table 1 below shows an example of conditions for producing the ultraviolet transparent electric conductor of the present invention comprising SrMoO ₃ by a high frequency magnetron sputtering method.

[0012]

[Table 1]

Table 2 below shows an example of conditions for producing the ultraviolet transparent electric conductor of the present invention comprising Na _x WO ₃ by a high-frequency magnetron sputtering method.

[0014]

[Table 2]

Further, an example of the conditions for producing the ultraviolet light transparent electric conductor of the present invention comprising Na _x WO ₃ by a vacuum evaporation method is shown in Table 3 below.

[0016]

[Table 3]

The transparent conductive oxide material capable of transmitting ultraviolet light according to the present invention can control the light transmission region within the range of 2 to 4 eV by adjusting the concentration of injected electrons, and has an electric conductivity of about 1E. It reaches + 4Scm ^-1 .

[0018]

According to the ultraviolet transparent electroconductive material thin film of the present invention, not only the electrical conductivity but also the
The light transmission wavelength region can be controlled. In particular, its electrical conductivity is about 1E + 4Sc compared to conventional transparent conductive materials.
Since it is as large as m- ¹ , practical application with a thinner film thickness is possible.

Therefore, the ultraviolet transparent electric conductive material according to the present invention is useful as a liquid crystal display, a window material such as a solar cell utilizing a photoelectric effect, a photoconductive cell, and an optical bandpass filter.

[0020]

EXAMPLES Examples are shown below to further clarify the features of the present invention. Example 1 A Na _x WO ₃ thin film was formed as an R-site-deficient perovskite structure material on a silica glass substrate by a high-frequency magnetron sputtering method. The conditions for forming the thin film by the high-frequency magnetron sputtering method were as shown in Table 1 above.

With respect to the obtained thin film (0.15-0.25 μm),
The light absorption was measured by a spectrophotometer, and the electric conductivity was measured by a DC four-terminal method. All measurements were performed at room temperature. FIG. 1 shows the measurement results of the light absorption, and FIG. 2 shows the measurement results of the electric conductivity.

As is apparent from FIG. 1, by injecting a large amount of electrons into Na _x WO ₃ , from the visible region to the ultraviolet region,
It exhibits a low absorption coefficient of 10 ³ to 10 ⁴ cm ^{−1 with} a width of about 1 eV.
That is, by controlling the carrier concentration by the amount of added Na, the position of the transmission region can be controlled within a photon energy range of about 2 to 4 eV. For example, when electron injection is performed on a Na _0.9 WO ₃ thin film, the transmissive region moves parallel to about 4 eV.

In addition, the electric conductivity increases almost in proportion to the increase in the amount of added Na, and in the Na _0.9 WO ₃ thin film, 6E + 4 Scm
It has reached ^-1 . Example 2 According to the method of Example 1, as a material having a perovskite structure, CaMoO ₃ ,
SrMoO ₃ and BaMoO ₃ thin films were formed.

With respect to the obtained SrMoO ₃ thin film (about 0.25 μm), light absorption was measured by a spectrophotometer, and electric conductivity was measured by a DC four-terminal method. All measurements were performed at room temperature.

As is apparent from FIG. 3, the obtained SrMoO ₃ thin film has a light transmission region in a photon energy region of 2.1 to 3.5 eV, and has an electric conductivity of 8E + 3 Scm ⁻¹ .

Further, since these thin films are easily dissolved in a nitric acid aqueous solution, they can be subjected to etching depending on the application.

[Brief description of the drawings]

FIG. 1 is a graph showing the influence of the amount of Na on the light absorption spectrum of the Na _x WO ₃ thin film obtained in Example 1.

FIG. 2 is a graph showing the effect of the amount of Na on electric conductivity in the Na _x WO ₃ thin film obtained in Example 1.

FIG. 3 is a graph showing a light absorption spectrum of a SrMoO ₃ thin film obtained in Example 2.

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[Procedure amendment]

[Submission date] April 12, 2000 (2004.1.
2)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Claims

[Correction method] Change

[Correction contents]

[Claims]

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Kohei Fukumi, 1-8-3, Midorioka, Ikeda-shi, Osaka Prefecture Inside the Industrial Technology Research Institute, Osaka Institute of Technology (72) Inventor, Masaki Makihara 1-8 Midorioka, Ikeda-shi, Osaka No. 31 Inside the Osaka Institute of Technology (72) Inventor Junji Hayakawa 1-81-31 Midorioka, Ikeda-shi, Osaka Inside the Institute of Industrial Technology Osaka (72) Junji Nishii Osaka 1-8-3 Midorigaoka, Ikeda-shi F-term in Osaka Institute of Technology (reference) 4G048 AA04 AA05 AB01 AC04 AC08 AD02 AD08 AE05

Claims (2)

[Claims] 1. An ultraviolet transparent electric conductor comprising a perovskite-type crystal structure material represented by a composition formula RMoO ₃ (1) (R is at least one of Ca, Sr and Ba). 2. An ultraviolet light-transparent electric conductor comprising a Na-site-deficient perovskite-type crystal structure material represented by a composition formula of Na _x WO ₃ (2) (where 0.3 ≦ x ≦ 1).