The structural and electrical properties modulated by excessive Ti substitution in SrTiO3 films

Ti-rich nonstoichiometric SrTiO3 (STO) films are fabricated on (111) Pt/Ti/SiO2/Si substrates by metal organic deposition. X-ray diffraction reveals the structure of the samples. The effect of nonstoichiometry on the electrical properties of the STO films is investigated by leakage current measurements and dielectric and ferroelectric characterizations. They reveal that the direct current (dc) leakage behavior is greatly improved with increasing Ti content, while the Ti = 1.1 and 1.2 samples show an obvious dielectric relaxation behavior related to the variable valence of the excess Ti ions. More importantly, the nonstoichiometric STO exhibits the room temperature ferroelectric polarization that can be explained mainly by the Ti antisitelike defects and the change of crystal lattice structure of the sample.