Crystallization and electrical characteristics of ferroelectric Bi3.15Nd0.85Ti3O12 thin films prepared by a sol–gel process

Ferroelectric Bi3.15Nd0.85Ti3O12 (BNdT) thin films were deposited on Pt/Ti/SiO2/Si substrates using a sol–gel process and Bi(NO3)3 was used as one of starting materials. Upon heating the major weight loss of the wet films occurred below 320 °C and nitrogen was almost completely removed at 650 °C. The films began to crystallize around 520 °C. The films annealed at 750 °C contain grains of 50–100 nm in diameter. The BNdT film capacitors with Pt top electrodes exhibited well-saturated hysteresis loops with a remanent polarization (2Pr) of 57.4 μC/cm2 and a coercive field of 108.3 kV/cm. The Pt/BNdT/Pt capacitors did not show any significant fatigue up to 6×1010 read/write switching cycles, and the retained charges remained nearly constant up to 104 s after applying a writing pulse. The leakage current density of the BNdT films is less than 5×10−8 A/cm2 under a low external field below 73 kV/cm.