Thickness dependence of ferroelectricity in GaFeO3-type epitaxial films

Abstract

GaFeO3-type oxide films are promising multiferroic materials due to their coexistence of ferroelectricity and ferrimagnetism at room temperature. For device applications, understanding the thickness dependence of their ferroelectric properties is crucial. In this study, we investigated the ferroelectric behavior of GaFeO3-type oxide films as a function of thickness. Notably, the GaFeO3-type structure is not perovskite but consists of three octahedral and one tetrahedral cation sites. Clear ferroelectric switching was observed down to a thickness of 14 nm. However, the remanent polarization decreased significantly below 8 nm and nearly vanished at 3 nm. Despite this reduction, partial polarization switching was still retained at 3 nm, and a voltage-dependent change in resistance was detected, suggesting the presence of a ferroelectric tunnel effect. These findings highlight the potential of GaFeO3-type oxides as scalable candidates for multifunctional nanoscale electronics.