Hybrid deposition of piezoelectric (11(2)over-bar-0) Mg(x)Zn(1-x)O (0 <= x <= 0.3) on (01(1)over-bar2) R-sapphire substrates using RF sputtering and MOCVD

Mg(x)Zn(1-x)O (0 = x = 0.3) films are deposited on R-plane (01 (1) over bar2) sapphire substrates using a hybrid deposition technique: metalorganic chemical vapor deposition and radiofrequency (RF) sputtering. Thick piezoelectric Mg(x)Zn(1-x)O films are deposited by RF sputtering on MOCVD grown thin ZnO buffers on R-sapphire substrate. Molar ratio of ZnO and MgO powders are mixed to form Mg(x)Zn(1-x)O (0 = x = 0.3) sputtering targets with NiO (2-3 wt.%) added for compensation doping to achieve piezoelectricity. Field emission scanning electron microscopy shows that the deposited films are dense and uniform. X-ray diffraction indicates that the sputter-deposited Mg(x)Zn(1-x)O (0 = x = 0.3) films retain the wurtzite crystal structure. The crystallinity of the deposited films is further improved by postannealing at 700 degrees C in oxygen. Compositional analysis of the films is carried out using Rutherford back-scattering. High-frequency and low-loss surface acoustic wave (SAW) testing devices fabricated on these films are demonstrated. The SAW properties are tailored to changing Mg compositions. In the ZnO/R-Al(2)O(3) system, two types of wave modes, the Rayleigh-type and the Love-type wave modes, are investigated.