Investigation of Mo Doping Effects on the Properties of AlN-Based Piezoelectric Films Using a Sputtering Technique

In this study, AlN-based films are deposited using a sputtering deposition method, and Mo dopants with different concentrations are added in the proposed system by controlling the sputtering power in order to improve the crystallinity and piezoelectric properties of AlN films. Through a detailed material analysis including energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM), piezoresponse force microscopy (PFM), and nano-indentation, the piezoelectric property optimization mechanism of proposed films was explored and the best process parameters were determined. The piezoelectric coefficient d(33) of AlN:Mo (3.46%) films reached 7.33 pm V-1, which is 82.79% higher than that of undoped AlN. As compared with the reported data about the dopants in AlN system, our proposed films have the better d(33) values with those dopants in AlN-based films except Sc dopants. However, Sc is known as an expensive metal, our proposed films could be applied to low-cost piezoelectric MEMS applications.