Effect of magnesium doping on the structural and piezoelectric properties of sputtered ZnO thin film

Structural and piezoelectric characteristics of magnesium-doped ZnO films were investigated. Magnesium-doped ZnO films with a c-axis preferred orientation were deposited on ST-cut quartz by radio frequency magnetron sputtering. The crystalline structure and surface morphology of films were studied by X-ray diffraction, scanning electron microscopy and atomic force microscopy. The electromechanical coupling coefficient and temperature coefficient of frequency of the filters were then determined using a Love wave filter. A uniform crystalline structure and smooth surface of the ZnO films were obtained when magnesium dopant level was 1.5 mol%. The grain size of the ZnO film increased when magnesium doped. It has been found that the temperature coefficient of frequency declines to +0.44 ppm/°C at 1.5 mol% magnesium-doped ZnO film.