Piezoelectric properties of ZnO films on a sapphire substrate deposited by an RF-magnetron-mode ECR sputtering system

Compared to conventional RF magnetron sputtering systems, electron cyclotron resonance (ECR) sputtering systems are characterized by the ability to generate high-density plasma under low gas pressure. (<11(2)over bar 0>)-plane oriented epitaxial ZnO films were deposited on an R plane sapphire substrate using the RF-magnetron-mode ECR sputtering equipment. As the results of the measurement, the films showed a good orientation and excellent effective electromechanical coupling factors (k(eff)) for the Rayleigh surface acoustic wave (SAW) and its high-order SAW waves. These coupling factors were equal to or higher than the theoretical values k(eff) obtained by the finite element method (FEM) analysis using a single crystal material constant.