MgxZn1-xO:: A new piezoelectric material

Piezoelectric ZnO thin films have been successfully used for multilayer surface acoustic wave (SAW) and bulk acoustic wave (BAW) devices. Magnesium zinc oxide (MgxZn(1-x)O) is a new piezoelectric material, which is formed by alloying ZnO and MgO. MgxZn1-xO allows for flexibility in thin film SAW device design, as its piezoelectric properties can be tailored by controlling the Mg composition, as well as by using MgxZn1-xOZnO multilayer structures. We report the metal-organic chemical vapor deposition (MOCVD) growth, structural characterization and SAW evaluation of piezoelectric MgxZn1-xO (x less than or equal to 0.35) thin films grown on (01 (1) over bar 2) r-plane sapphire substrates. The primary axis of symmetry, the c-axis, lies on the MgxZn1-xO growth plane, resulting in the in-plane anisotropy of piezoelectric properties. SAW test devices for Rayleigh and Love wave modes, propagating parallel and perpendicular to the c-axis, were designed and fabricated. Their SAW properties, including velocity dispersion and piezoelectric coupling, were characterized. It has been found that the acoustic velocity increases, whereas the piezoelectric coupling decreases with increasing Mg composition in piezoelectric MgxZn1-xO films.