Substrate dependent structure and in-plane dielectric properties of Ba(Sn0.15Ti0.85)O3 thin films

The structure, microstructure and in-plane dielectric properties of Barium tin titanate Ba(Sn_0.15Ti_0.85)O₃ (BTS) thin films grown on (100) LaAlO₃ (LAO) and (100) MgO single crystal substrates through sol–gel process were investigated. The films deposited on (100) LAO substrate exhibited a strong (100) preferred orientation while the film deposited on (100) MgO substrate showed polycrystalline structure. The in-plane ɛ–T measurements reveal that the films grown on (100) LAO substrate exhibited an obvious room-temperature ferroelectric state, while the film grown on MgO substrate showed paraelectric state in the temperature range of 10–130 °C. A high tunability of 52.11% was observed for the BTS films deposited on (100) LAO substrate at the frequency of 1 MHz with an applied electric field of 80 kV/cm, which is about two times larger than that of the BTS films deposited on (100) MgO substrate. The obvious differences in the dielectric properties could be attributed to the stress in the films, which come from lattice mismatch and difference in the thermal expansion coefficients between the film and substrates. This work clearly reveals the highly promising potential of BTS films for application in tunable devices.