Growth Mechanism of ZnO Film by Reactive Sputtering Method –Significance of Thermodynamics in a Plasma System–

Zinc oxide films are prepared on a glass substrate by sputtering a zinc target in the rf glow discharge plasma of an argon/oxygen mixture. Growth rate, crystallographic structure, optical absorption, and the electrical conductivity of the films prepared are correlated experimentally with the conditions of the film growth process. The escape rate of zinc atoms from the growing surface, which depends solely on temperature, predominantly affects the chemical composition of the prepared film which includes Zn/ZnO mixture, Zn1+x O, and ZnO. The role of thermodynamic equilibrium in a glow discharge plasma system that is likely to be far from equilibrium and is kinetically controlled is pointed out for the first time.