Properties of Sc_xAl_1-xN (x = 0.27) thin films on sapphire and silicon substrates upon high temperature loading

Scandium Aluminum Nitride thin films (Sc_xAl_1-xN) are attracting more and more attention for micro-electromechanical systems (MEMS) because of significantly increased piezoelectric constants compared to pure AlN. This work provides a comprehensive study of thermal annealing effects on Sc_xAl_1-xN (x = 27 %) films synthesized via DC magnetron sputter deposition at nominally unheated Silicon and Sapphire substrates. Compared to the “as deposited” state increasing c-axis orientation and crystalline quality upon annealing up to 1000 °C of films with mixed crystallographic orientation is observed via X-ray diffraction and transmission electron microscopy based analyses. Also the piezoelectric coefficient d ₃₃ of Sc_xAl_1-xN on Si shows increasing values at enhanced annealing temperatures. However, the improved piezoelectric properties are accompanied by both increased leakage currents and loss tangent values.