Preferred Orientation in RF–Sputtered ZnO Films

Abstract

The influence of substrate material and sputter deposition parameters on the degree of preferred perpendicular orientation of ZnO films is studies and compared to earlier results on ZnO films having a preferred parallel orientation. Films sputtered onto a very thin (200 Å) film of SiO2 on top of the counterelectrode have the largest degree of preferred orientation. A relatively high sputter rate of the order of 400 Å/min which results in a strong substrate heating has a beneficial effect on both preferred orientations. A negative substrate bias voltage leads to an increase in the degree of preferred orientation whereas it results in a loss of orientation in perpendicular oriented ZnO films. There exists a good correlation between the degree of preferred orientation as determined by X-ray diffractometry and electromechanical coupling coefficient as determined by ultrasonic pulse echo measurements.