Observation of room-temperature ferroelectricity in tetragonal strontium titanate thin films on SrTiO3 (001) substrates

The authors investigated the ferroelectric properties of strontium titanate (STO) thin films deposited on SrTiO3 (001) substrates with SrRuO3 electrodes. The STO layer was grown coherently on the SrTiO3 substrate without in-plane lattice relaxation, but its out-of-plane lattice constant increased with a decrease in the oxygen pressure during deposition. Using piezoresponse force microscopy and P-V measurements, the authors showed that the tetragonal STO films possess room-temperature ferroelectricity. The authors discuss the possible origins of the observed ferroelectricity.