Mamoru Mizuhashi

Electrical properties of vacuum-deposited indium oxide and indium tin oxide films

Abstract Indium oxide films were deposited onto soda-lime glass substrates. The lowest resistivity found for indium tin oxide (ITO) films was 2 × 10 −4 Ω cm with a carrier density ne of 1 × 1021 cm−3 and a mobility μH of 30 cm2 V−1 s−1 at the optimized doping level (5 wt.%) and substrate temperature (400 °C), whereas it was 4 × 10 −4 Ω cm with ne = 4 × 1020 cm−3 and μH = 72 cm2 V−1 s−1 for pure indium oxide films. The characteristic features of ITO films are their high carrier density and low mobility in comparison with ordinary electron-beam-deposited ITO films. It was determined from thermal stability tests that the contribution to the carrier density made by the addition of tin was at most (3–4) × 1020 cm−3; i.e. the efficiency of generation of free carriers by the addition of tin is only a few tens of per cent.

Structural, electrical and optical properties of r.f.-magnetron-sputtered SnO2:Sb film

Abstract The effects of gas composition, pressure and substrate temperature on the properties of relatively thick (0.2–0.8 μm) SnO2 films deposited onto fused quartz substrates by r.f. magnetron sputtering are reported. The lowest resistivity of about 2 × 10−3ωcm was attained for high rate deposition conditions of about 1000 A min −1 on substrates at a temperature of 400°C in an atmosphere of 10% O2. This value corresponds to a carrier density of 3 × 1020cm−3 and a mobility of 10 cm2V−1s−1. The crystal structure was found to be sensitive to all the above parameters. Low resistivity films showed a highly preferred orientation of (101) parallel to the substrate.

Electrochromic devices for transmissive and reflective light control

Abstract Fundamental properties of a transmissive electrochromic device are described. The device consists of a semisolid electrolyte and a WO3 film sandwiched by a pair of transparent conductive glass sheets. The transmittance of the device can be arbitrarily controlled within the range from 80% to 10%. The response time was found to be greatly dependent on the device size. The lifetime for repetitive operations is more than 105 cycles. Reasonably good durability has been determined. This device is capable of controlling the reflectance of a mirror, with the reflective layer coated on the either surface of the outer glass sheet. Details of this reflective device are also described. The reflectance of the mirror of the size of 25 cm × 6.5 cm can be changed from 72% to 20% within 4 s at 1.5 VDC. This device is suitable as an antidazzling mirror for motor cars.

Electrical properties of post-oxidized In2O3:Sn films

Abstract In 2 O 3 :Sn (ITO) films were prepared on soda lime glass by evaporating suboxides and oxidizing these in air. The specific resistivity of the films showed a broad minimum of about 2×10 -3 ω cm for a doping level range of 10–30 wt.% SnO 2 and they had decreased mobility (10 cm 2 V -1 s -1 ) and carrier density (2×10 20 cm -3 ) compared with high performance ITO films obtained by reactive evaporation onto a high temperature substrate. Unlike the behaviour of films treated in vacuum or in forming gases, the change in specific resistivity with oxidation for our films exhibited three characteristic stages: a sharp decrease accompanied by increasing transparency in the first stage, a steep increase in the second and a very slow increase in the third. The lowest resistivity was attained at the end of the first stage with a slight absorption. This change in resistivity was explained qualitatively on the basis of the diffusion model. It was also found that the resistivity could be further reduced if the residual gas pressure during the deposition was maintained as low as possible.

Transmissive electrochromic device

Abstract This paper describes the fundamental properties of a transmissive electrochromic device. The device is comprised of a semi-solid electrolyte and a WO3 film sandwiched by a pair of electroconductive sheet glasses. The transmittance of the device can be arbitrarily controlled within the range from 80% to 10%. The response time was found to be greatly dependent on the size of the device and the applied dc voltage. The lifetime for repetitive operation is more than 105 cycles. The devices have fairly good durability against outdoor conditions. Based on a kinetic study of the tungsten bronze and an equivalent circuit analysis, the effects of the rate determining factors are discussed.

Electrochromic Devices For Transmissive And Reflective Light Control

Fundamental properties of the transmissive electrochromic device are described. The device comprises of a semi-solid electrolyte and a WO3 film sandwiched by a pair of transparent electroconductive sheet glasses. The transmittance of the device can be arbitrarily controlled within the range from 80% to 10%. The response time was found to be greatly depended on the size. The life time for the repetitive operations is more than 105 cycles. Fairly good durability against the outdoor conditions has been clarified. This device is capable of controlling reflectance of mirror when a reflective layer is coated on the either surface of outer glass. Outline of this reflective device is also described. The reflectance of the mirror of the size of 25cm x 6.5cm can be changed from 72% to 20% within 4sec at 1.5VDC. This device is suitable for anti-dazzling mirror of motor cars.

Transmissive Electrochromic Device

This paper describes the fundamental properties of the transmissive electrochromic device. The device comprises of a semi-solid electrolyte and a WO3 film sandwiched by a pair of electroconductive sheet glasses. The transmittance of the device can be arbitrarily controlled within the range from 80% to 10%. The response time was found to be greatly dependent on the size of device and the applied DC voltage. The life time for the repetitive operations is more than 105 cycles. The devices have fairly good durability against the outdoor conditions. Based on the kinetic study on tungsten bronze and the analysis of equivalent circuit, the effects of the rate determining factors are discussed.

Transport of Li+ Ions In Amorphous Tungsten Oxide Films

Coloring / bleaching processes of LixWO3 electrochrothismwere examined by means of emf, chronoamperometry, voltammetry and ac impedance measurements. Current-potential relation was found to be ohmic in the short time region and expressed by i=(Eapp-emf(x))/ R. Satisfactory fittings were obtained for chronoamperometry and voltammetry measurements on the basis of the assumption of diffusion-limited process with above i-E relation. It was elucidated from the detailed analysis of impedance that R was given by the summation of the resistances of solution, electrode, charge transfer and material transfer. It was newly found that diffusion coefficients for several WO3 films were in the range of 1.5 X 10-9 to 3 x 10-12 cm2,sec at 20°C and they were strongly dependent on water content in the electrolyte solution.

Electrochromism in amorphous lithium tungsten oxide films

Abstract A small ac-signal impedance analysis was utilized to characterize the surface property of an ITO electrode and Li transport in an Li x WO 3 electrode. The as-deposited ITO film has a surface layer with extremely high carrier density, which could be easily removed by mechanical polishing. Based on the kinetic model of Li x WO 3 , the diffusion coefficient of Li transport was obtained. It depends on the various deposition conditions of WO 3 films and the composition of the electrolyte used. The response of Li x WO 3 film showed a gradual decrease and reached a certain equilibrium after repeated cycling (more than 10 4 times). The examination of such a degradation phenomenon leads to the conclusion that there are two active sites in the WO 3 structure, which are available for the Li ion; one for coloration ( x Li + + WO 3 + x e − ↔ Li x WO 3 ), and the other for an ion exchange reaction expressed by WO-H+Li + ↔ WO-Li+H + . The mechanism of these phenomena are further discussed. Impedance analysis has been proved to be very sensitive and applicable enough to the quantitative characterization of ITO and Li x WO 3 electrodes involved in the electrochromic device.

Photochromic coating by vacuum deposition

Abstract Photochronic thin films have been obtained by the simultaneous deposition of silicon monoxide, lead silicate, aluminum chloride and copper-sensitized silver halide, followed by a heat treatment in the dark and in air at 100°–200°C for several hours. The growth of silver halide microcrystals in the film is explained by a simple diffusion-limited process. The fading process can be described by a second order chemical reaction, which has been applied to a type of photochromic glass containing silver halide microcrystals in the glass matrix. The half-fading and half-darkening time of typical films were 10–20 min and 5–20 min, respectively.