Effect Of Microstructure And Surface Morphology Evolution On Optical Properties Of Nd-modified Pb(zr_xti_(1-x))o_3 Thin Films

摘要

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 ℃-1000 ℃. 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.