Synthesis and Electrical Properties of Sputtered (Na_(0.5)Bi_(0.5))TiO_3Thin Films on Silicon Substrate

摘要

The growth and characterizations of polycrystalline (Na_(0.5)Bi_(0.5))TiO_3 (NBT) thin films have been performed. (Na_(0.5)Bi_(0.5))TiO_3 films have been deposited by rf-magnetron sputtering on the unheated Pt/TiO_x/SiO_2/Si structure and postannealed to crystallize the film in the perovskite phase. The optimal sputtering conditions and postannealing treatment to obtain a high degree of NBT crystallinity are reported. The dielectric, ferroelectric, and piezoelectric properties of NBT films were investigated. At 10 kHz, the dielectric constant and losses are 520 and 0.032, respectively. The ferroelectric hysteresis loops are well defined with a remnant polarization of 12 μC/cm~2 and a coercive field of 125 kV/cm, but piezoelectric measurements at the macroscopic level were also performed: a high piezo coefficient (d_(33efmax)) of 80 pm/V was obtained, similar to PZT films. This result demonstrates that NBT thin film is really a promising candidate for lead-free MEMS applications. The local piezoresponse was evaluated by piezoelectric force microscopy.