Effect of sputtering oxygen partial pressures on structure and physical properties of high resistivity ZnO films

High quality piezoelectric ZnO thin films were deposited on Si substrates by dc reactive magnetron sputtering. A detailed study of these films has been carried out using X-ray diffraction, scanning electron microscopy, reflection electron diffraction, electrical measurement, and mechanical measurement. These films are highly c-axis oriented with super surface flatness and high resistivity above 10(6) Omega cm. The experimental results indicated that there was an optimum oxygen partial pressure where the film shows relative stronger texture, better nano-crystallite and lower surface roughness. On the other hand, with the increasing oxygen partial pressure (Ar-to-O-2 ratio decreased from 1: 1 to 1:3), the resistivity increased, while the hardness and modulus of the films have little variation. We have successfully fabricated a surface acoustic wave filter (SAWF) using these ZnO films and found that these films can excite effective surface acoustic wave. (C) 2003 Elsevier B.V. All rights reserved.