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

Abstract

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 LiGa_0.8Sc_0.2O₂/SrRuO₃/(111)SrTiO₃.