Electric-Field Tunability of Dielectric in Polycrystalline Sr 1 −x Mn x TiO 3 Thin Films

The electric-field tunability of dielectric constant (epsilon-E) in Sr1-xMnxTiO3 films (x = 0, 0.005, 0.010, 0.020 and 0.030) prepared by the metal organic decomposition method on Pt/Ti/SiO2/Si substrates is studied in the frequency range from 100 Hz to 1MHz with different Mn contents at different temperatures. The frequency-independent tunability increases strongly with decreasing the temperature from 300 K to 150 K. The tunability (similar to 31%) in thin films (x = 0.005) at 150 K is obtained and the temperature for the same tunability in ceramics is about 60 K lower than the present one. This tunability is comparable with that in one of ferroelectric Sr1-1.5xBixTiO3 thin films. Similarly, the well-defined P(E) hysteresis loop and 2P(r) (1.2 mu C/cm(2)) can be obtained at 300 K in Sr1-xMnxTiO3 films with x = 0.005. Both the existence of electric dipole or poled micro domain introduced by the doped Mn2+ located in the off-center position at Sr sites and the strain between the thin film and the substrate are the origins of the tunable and polar behavior in Sr1-xMnxTiO3 films.