Structural and dielectric properties of Ba(Ti_1-xSn_x)O₃ thin films

Close correlation between the dielectric constant and the degree of preferential (111) orientation is found for Ba(Ti_0.85Sn_0.15)O₃ (BTS₁₅) solid-solution thin films deposited on a Pt/Ti/SiO₂/Si(100) substrate by pulsed laser deposition. It is shown that substrate temperature is the principal factor which determines orientation and crystalline quality of the films. Substrate temperatures higher than 700°C are required to achieve (111) orientation with good crystalline quality. BTS₁₅ films with strong (111) orientation have large dielectric constant which reaches 2500 at 22°C. These films exhibit a D-E hysteresis loop, but small remanent polarization of 0.89 μC/cm² and coercive field of 3.2kV/cm are obtained at 18°C. Films having the composition with lower Sn ratio exhibit larger remanent polarization. Causal relationships among the dominant film orientation, crystalline quality and dielectric constant are discussed.