Characteristics of strontium-doped ZnO films on love wave filter applications

The effect of dopant concentrations in strontium-doped ZnO films on Love wave filter characteristics was investigated. Strontium-doped ZnO films with a c-axis preferred orientation were grown on ST-cut quartz by radio frequency magnetron sputtering. The crystalline structures and surface morphology of films were studied by X-ray diffraction, scanning electron microscopy and atomic force microscopy. The electromechanical coupling coefficient, dielectric constant, and temperature coefficient of frequency of filters were then determined using a network analyzer. A uniform crystalline structure and smooth surface of the ZnO films were obtained at the 1-2 mol% strontium dopant level. The electromechanical coupling coefficient of the I mol% strontium-doped ZnO film reaches a maximum of 0.6 1 %, and the temperature coefficient of frequency declines to +12.87 ppm/'C at a 1.5 mol% strontium dopant level. (C) 2007 Elsevier B.V. All rights reserved.