Dielectric and ferroelectric properties of pulsed laser deposited strontium barium niobate thin films

The dielectric and ferroelectric properties of pulsed laser deposited strontium barium niobate (SBN) thin films were investigated. The samples were prepared using a Q-switched Nd:YAG laser with a wavelength of 355 nm and a fluence of 8 J cm-2. The oxygen ambient pressure and substrate temperature were set at 50 mTorr and 700 °C, respectively. The measurements of x-ray diffraction show that the films have tungsten-bronze- type structure. Pt/SBN/Pt capacitor structure was made on (111) silicon wafer to perform the ferroelectric and dielectric measurements. From the observations of the P-E loops, the saturation polarization, remanent polarization and coercive field at 25 °C are equal to 40.7 μC cm-2, 32.5 μC cm-2 and 3.8 kV cm-1. The shape of the P-E loop becomes slimmer at temperatures above 150 °C, indicating that a ferroelectric-to-paraelectric transition occurs. The dielectric constant and loss tangent of the films at 10 kHz were found to be equal to 240 and 0.4, respectively. The saturation and remanent polarization remain almost unchanged after 109 switching cycles, indicating that pulsed laser deposited SBN films have good fatigue endurance.