Potential of reactively RF sputtered ZnO thin films for the fabrication of microwave filters

The piezoelectric properties of reactively sputtered ZnO thin films deposited on glass and silicon substrates were studied in order to assess their potential for the construction of RF overmoded filters. Films of high crystallographic orientation {002}, as shown by XRD measurements and SEM observations, and high value of keff2, calculated with the aid of the BVD model, were obtained after the optimization of the deposition conditions, with highly repetitive properties. Simple devices were designed and constructed on silicon substrates which showed a quality factor of 1000 without the use of a Bragg acoustic reflector, and a temperature drift of -30 ppm/°C.