Effect of microstructure and surface morphology evolution on optical properties of Nd-modified Pb(Zr xTi 1 − x)O 3 thin films

Abstract

Optical properties of nanocrystalline Nd-modified lead–zirconate–titanate thin films were studied. Pulsed laser deposition was used for thin-film fabrication at room temperature. Thin films were deposited on single-crystal MgO (100) substrates and post-annealed between temperatures 400 °C–1000 °C. The crystal structure and thin film morphology were studied using x-ray diffraction technique and atomic force microscopy, respectively. The optical transmission spectra of the films were measured at UV–vis–IR wavelengths and the results were utilized to obtain the refraction index n, extinction coefficient k, and the value of the band gap E g. Thin films annealed at different temperatures had a different crystal structure and morphology. Film thickness and annealing temperature also had an effect on the crystal orientation of the films. Trigonal and tetragonal phases co-existed in analyzed films so that films with thickness of 150 nm had strong tetragonal orientation with increasing post-annealing temperature. Trigonal and tetragonal phase co-existence was present in films with thickness of 300 nm post-annealed at low temperatures. Optical absorption edge shifted to shorter wavelengths with decreasing film thickness and post-annealing temperature which led to increase in band gap energies. Atomic force microscopy studies showed a clear dependence of films root mean square roughness on post-annealing temperature and crystal structure.