Kunihiko Adachi

Texture morphology of SnO2:F films and cell reflectance

The texture formation on the surface of SnO2:F films was carried out using a four component CVD reaction system with tin tetrachloride as a main source. The texture up to about 30% in terms of the haze value could be formed by selecting CVD parameters. It was found in the transmission measurement of hazy SnO2:F films that a part of incident light escaped from the cut edges of the glass substrate even if the integration sphere was used. A nondestructive immersion method is proposed. This enables more exact evaluation of light quantity effectively transmitted to the active part of the a-Si solar cell when it is combined with the reflectance measurement of a pseudocell. It was also found that the reflectance of pseudocells decreased as the haze value increased, and as the shape of grains became sharper when the haze values were similar.

Development of Silver-Based Multilayer Coating Electrodes with Low Resistance for Use in Flat Panel Displays

Multilayer coatings consisting of thin silver layers sandwiched between layers of transparent conducting metal oxides were investigated from the view-point of low-resistance electrodes for use in flat panel displays. Optimization of the multilayer coatings resulted in a five-layer coating composed of indium and zinc oxide composite material (IZO) and silver containing 1 wt% of palladium (Ag–Pd). The coatings had satisfactory properties of low resistance, high transmittance, high moisture and alkali resistance, and good patterning.

Surface microstructures of ZnO coated SnO2: F films

Abstract ZnO films of 100 A thick were coated on textured SnO 2 : F films using DC magnetron sputtering to improve hydrogen plasma durability. The surface microstructure and the plasma durability of the films were investigated using a scanning electron microscope (SEM), reflection high energy electron diffraction (RHEED) and optical measurements. It was found that the ZnO coated films exhibited high durability against hydrogen plasma. The well ordered microstructure of ZnO was considered to act as a good barrier against hydrogen diffusion into the SnO 2 : F films.

Improvement of Alkali Durability of Silver-Based Multilayer Coatings for Use in Flat Panel Displays

Silver-based multilayer coatings are well known to be transparent films with low electrical resistivity. In particular, indium and zinc composite oxide (IZO)/silver containing palladium (AgPd) multilayer coatings have good pattering properties and durability. However, the IZO/AgPd multilayer coatings do not have sufficient alkali durability as transparent electrodes of flat panel displays (FPDs). In order to solve this problem, coatings covered with a protective layer of tin-doped indium oxide (ITO) were investigated. Over-coating of an ITO layer degraded the patterning properties of the multilayer coatings because the etching rates of ITO, IZO and AgPd layer were very different. From the viewpoint of controlling the etching rate of each layer independently, the etching solution composed of hydrobromic acid and iron chloride was adjusted, so that the ITO/IZO/AgPd/IZO/AgPd/IZO/substrate multilayer coatings could be fabricated into fine patterns for electrodes. The multilayer coatings thus prepared are more tolerable for alkali detergents used in the production process of FPDs.

Development of tempered-glass substrates with TCO films for a-Si solar cells

Abstract Tempered-glass substrates with transparent conductive oxide (TCO) films were developed for a-Si solar cells using an air blasting method. The mechanism of thermal deflection arising from the difference of thermal properties between glass and TCO films was investigated using in situ X-ray diffraction method during heating and cooling processes. It was found that the deflection was caused by tensile stress induced in the films at a high temperature above 600°C as well as the difference of thermal expansion coefficient between glass and TCO films. In addition, the stress was found to be closely correlated to the deposition temperature of the TCO films. Tempered glass with TCO films with small deflection, which passed strength test using a steel ball (227 g, 2.5 m height), was obtained by increasing the deposition temperature of the TCO films.

Hydrogen plasma treatment of ZnO-coated TCO films

Hydrogen plasma treatment of textured SnO/sub 2/:F TCO (transparent conductive oxide) films coated with ZnO layer of 100 /spl Aring/ in thickness was investigated for high efficiency a-Si solar cells. It was found that a ZnO over-layered structure was effective in improving the hydrogen plasma durability. Furthermore, it was shown that the resistivity of over-layered TCO films decreased dramatically after the hydrogen plasma treatment at a temperature of 300/spl deg/C without any change in optical transmission. The decrease in resistivity was due to the sufficient increase in Hall mobility, which was caused by the elimination of chemical reduction. After the hydrogen plasma treatment under the optimized condition, the highest Hall mobility of 70 cm/sup 2V/spl middot/sec, sheet resistance below 5 /spl Omegasq,. and optical transmission above 85% were attained.<<ETX>>

ZnO films deposited by APCVD

The deposition kinetics and impurity doping on ZnO films are studied. The film was prepared by atmospheric pressure CVD using zinc acetylacetonate. The rate determining reaction for film growing seems to be the reaction between the raw material and oxygen. Aluminum doping decreased the resistivity to 3.5*10/sup -2/ Omega -cm. Fluorine doping is found to be more effective. A resistivity of 2.0*10/sup -3/ Omega -cm was obtained.<<ETX>>

Hydrogen plasma durability of SnO/sub 2/:F films for use in a-Si solar cells

The hydrogen plasma durability of textured SnO/sub 2/:F films was investigated at 220 degrees C. It was found that during the initial stage of exposure, TCO films with a carrier concentration less than 4*10/sup 20/ cm/sup -3/ show a decrease in resistivity. A Hall-effect measurement revealed that the decrease in resistivity was due mostly to a mobility increase. This increase could be explained by the reduction of potential barrier height due to the proton passivation of grain boundaries. The results suggest that SnO/sub 2/:F films with low carrier concentration pretreated by hydrogen plasma can possess the conflicting properties of low absorption and low resistivity.<<ETX>>