Structure and electrical properties of La and Nb co-modified Sr0.8Bi2.2Ta2O9 thin films

Polycrystalline Sr0.8La0.1Bi2.1Ta2O9 (SLBT), Sr0.8Bi2.2Ta1.5Nb0.5O9 (SBTN), Sr0.8La0.1Bi2.1Ta1.5Nb0.5O9 (SLBTN) were fabricated on Pt/Ti/SiO2/Si substrates by metalorganic decomposition. Well-saturated hysteresis loops with remanent polarization (2Pr) around 24 μC/cm2 and coercive field (2Ec) around 112 kV/cm are obtained on Pt/SLBTN/Pt capacitors. Imprints, shifts of hysteresis loops along the voltage axis, are observed after heat treatment of poled Pt/SLBTN/Pt capacitors. Pt/SLBTN/Pt capacitors show excellent fatigue resistance with no polarization reduction up to 109 switches. The dc leakage current density of Pt/SLBTN/Pt capacitors is in the order of 10−8 A/cm2 below 100 kV/cm. These results indicate that the La3+ and Nb5+ co-modification is an effective way to improve the ferroelectric properties of Sr0.8Bi2.2Ta2O9 (SBT) thin films.