The etched surface of sputtered zinc oxide and its relationship to fractal growth and surface wave properties

The etch characteristics of sputtered zinc oxide are used as a measure of the microstructural integrity of the films and are related to acoustical and optical surface wave propagation properties. Examination of the etched surface of thin-film ZnO reveals a defect structure which points to a fractal growth mechanism. The observed fractal dimension of the film surface is in the 1.5 to 1.6 range for high-quality zinc oxide grown on oxidized silicon. By controlled etching to produce surface roughness, changes in the loss and frequency of surface acoustic waves and in the loss of guided optical waves are observed and are related to theoretical models