Epitaxial growth technique for single-crystalline PbTiO3 thin film on Si substrate using an HfO2 buffer layer

We have succeeded in obtaining thin-film single crystals of PbTiO3 (PT) piezoelectrics on a Si single crystal with a few defects in the film at the extremely low temperature of 450 degrees C, which was considered difficult in the past. We confirmed that the obtained thin film demonstrates dielectric characteristics (lattice constant: a = 0.3904 nm, c = 0.4159 nm; relative dielectric constant: 120), along with an extremely high residual polarization value (Pr = 85 mu C cm(-2)). A martensitic transformation in the HfO2 buffer layer plays an important role in the c-domain formation of the epitaxial PT film by an elastic lattice matching. This discovery will demonstrate a new function of HfO2 film and indicates that the system can be applied in a broad range of scenarios seeking to obtain single crystals for various functional oxide layer thin films on Si wafer substrates. (C) 2021 The Japan Society of Applied Physics