Long-time relaxation of photo-induced influence on BiFeO_3 thin films

摘要

An intuitively persistent enhancement of the local surface potential of BiFeO_3 layers in both heterostructures of BiFeO_3/SrRuO_3/SrTiO_3 and BiFeO_3/Sr_(0.09)Nb_(0.01)TiO_3 was observed by the Kelvin probe force microscopy technique after the illumination of 375 nm laser. This photo-induced enhanced surface potential can maintain as long as 15 h after the illumination. We attributed this super-long-time relaxation of photo-induced influence to a photo-induced depolarization in the BiFeO_3 thin films, and our first-principles calculation of double-potential well further provides an instinct understanding on this depolarization process. Our findings provide a peculiar understanding into the photo-induced phenomena on the widely researched ferroelectric systems and offer an approach to tune their multifunctionality of the magnetization and polarization not only by applied magnetic and electric fields but also by optical filed.