Synthesis and Electrical Properties of Sputtered (Na0.5Bi0.5)TiO3 Thin Films on Silicon Substrate

The growth and characterizations of polycrystalline (Na0.5Bi0.5)TiO3 (NBT) thin films have been performed. (Na0.5Bi0.5)TiO3 films have been deposited by rf-magnetron sputtering on the unheated Pt/TiOx/SiO2/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 similar to 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 similar to mu C/cm2 and a coercive field of 125 similar to kV/cm, but piezoelectric measurements at the macroscopic level were also performed: a high piezo coefficient (d33effmax) of 80 similar to 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.