Evaluation of ferroelectricity in a distorted wurtzite-type structure of Sc-doped LiGaO2.

Since the discovery of ferroelectricity in a wurtzite-type structure, this structural type has gathered much attention as a next-generation ferroelectric material due to its high polarization value combined with its high breakdown strength. However, the main targets of wurtzite-type ferroelectrics have been limited thus far to simple nitride/oxide compounds. The investigation of new ferroelectric materials with wurtzite-type structures is important for understanding ferroelectricity in such structures. We therefore focus on β-LiGaO2 in this study. Although AlN and ZnO possess well-known wurtzite-type structures (P63mc), β-LiGaO2 has a distorted wurtzite-type structure (Pna21), and there are no reports of ferroelectricity in LiGaO2. In this study, we have revealed that LiGaO2 exhibits relatively high barrier height energy for polarization switching, however, Sc doping effectively reduces that energy. Then, we conducted thin film preparation and evaluation for Sc-doped LiGaO2 to observe its ferroelectric properties. We successfully observed ferroelectric behavior by using piezoresponse force microscopy measurements for LiGa0.8Sc0.2O2/SrRuO3/(111)SrTiO3.