Effects of deposition temperatures of Nd-doped Bi₄Ti₃O₁₂ thin films prepared by pulsed laser deposition

Recently the deleterious environmental impact of the lead used in many ferroelectric and piezoelectric devices has stimulated research into lead-free alternatives with comparable properties. Bismuth titanate-based materials are considered to be candidates for use as lead-free piezoelectrics. In this study, we prepared the Bi_3.15Nd_0.85Ti₃O₁₂ (BNdT) thin films by using Pulsed Laser Deposition (PLD), which is a relatively easy method for the fabrication of thin films. The samples were grown on Pt/Ti/SiO₂/Si substrates using a KrF laser (248 nm). To find an optimal fabrication condition of this sample, we varied the PLD deposition conditions, including the substrate temperature, oxygen gas pressure, repetition frequency, target-substrate distance and pulse energy density. We found that the deposition temperature is an important parameter which should be optimized to get high-quality BNdT films. The BNdT thin films were studied by X-ray diffraction (XRD), atomic force microscopy (AFM) surface images, measurements of frequency-dependent dielectric constant and dielectric loss, polarization–electric field (P–E) curves, and fatigue tests. With increasing the deposition temperature the (117) peak of XRD increased, and the intensity ratio of (117)/{(117) + (006) + (200)} peak increased and its value was 68.3% at 650 °C and 44.3% at 700 °C. We note that the phase formation was strongly dependent on the deposition temperature in our BNdT films.