Effects of Annealing Temperature on the Structural, Surface, and Optical Properties of PZT Thin Films Deposited by Sputtering on Al2O3 Substrates

This study investigates the structural, morphological, and optical properties of PZT (lead zirconate titanate) thin films deposited on Al2O3 substrates via RF sputtering, with a particular focus on the effects of annealing temperature. The films were annealed at 500°C, 600°C, and 700°C, and characterized using XRD, SEM (including cross-sectional imaging), AFM, EDX, and UV–VIS spectroscopy. SEM and AFM images were additionally analyzed using MATLAB-based image processing techniques. XRD analysis revealed a dominant pyrochlore phase at 500°C, whereas the perovskite phase became prominent at higher temperatures. Grain sizes were estimated using the Scherrer equation and further validated through quantitative image analysis. Grain size evaluations based on three complementary techniques—XRD (via the Scherrer equation), MATLAB-assisted SEM image analysis, and AFM topography—consistently demonstrated a particle growth trend with increasing annealing temperature. While XRD yielded average crystallite sizes from diffraction peak broadening, image-based particle analysis and surface profiling provided direct morphological confirmation. The agreement among these independent methods reinforces the conclusion that higher annealing temperatures promote grain coarsening, likely driven by enhanced atomic mobility and crystallization dynamics. SEM images confirmed the formation of homogeneous and crack-free films, while cross-sectional SEM indicated a decrease in film thickness with increasing temperature. EDX analysis verified the elemental composition with only minor deviations. Tauc plots, based on a direct allowed transition, showed that the optical band gap decreased from 3.5 eV in the pyrochlore phase (500°C) to approximately 3.35 eV in the perovskite phase (600°C and 700°C), reflecting improved crystallinity and reduced structural disorder. Overall, the results highlight the critical role of annealing temperature in tailoring the crystallinity, surface morphology, and optical properties of PZT thin films, offering valuable insights for their application in high-performance electronic and optoelectronic devices. © 2013 IEEE.