Design of Advanced Functional ZnO Conductive Thin Films with Arc Plasma

Abstract

　We demonstrate the characteristics of dc arc plasma to clarify the advantage of reactive plasma deposition with dc arc plasma over the conventional other deposition methods such as magnetron sputtering. Both carrier concentration and crystallographic orientation distribution of Ga-doped ZnO (GZO) polycrystalline films deposited by the reactive plasma deposition can be controllable. The irradiation of electronegative oxygen ions (O⁻) generated in the afterarc plasma is an effective way for reducing the density of oxygen vacancies (V_O) together with an increase in the density of O⁻ trapped at the grain boundaries. V_O on and in the vicinity of the surface of ingrains exhibits as just hydrogen-gas adsorption sites, whereas O⁻ reacts with hydrogen gas to create carrier electrons. The hydrogen-gas sensors based on 50-nm-thick GZO films having the reactive O⁻ located at the grain boundaries exhibited high response to 0.25% of hydrogen gas at 330℃.