Growth and characterization of Pbl_2 thin films by vacuum thermal evaporation

摘要

The aim of this study was to investigate the morphology and optical absorption of Pbl_2 thin films. Pbl_2 films of different thickness were deposited on glass substrate at ambient temperature by thermal evaporation technique. The deposition rate was optimized at 1-2 nm/s to grow uniform good quality films. The structural analysis of the films was carried out by X-ray diffraction (XRD). The morphology of so prepared films was studied by Scanning Electron Microscope (SEM). The absorption spectra were recorded using a UV-Vis fiber optics based spectrophotometer. All the measurements in the present work were carried out at room temperature (～300 K). Pbl_2 seems to have a very strong affinity for the growth of preferred (001) orientation. The d spacing of (001) peaks match quite well with ASTM data for 2H polytype of Pbl_2 which confirms the stoichiometry. A uniform spherical grain size growth is clearly evident from SEM micrographs. Optical absorption analysis indicates that the Lead Iodide is having a direct optical band gap of about 2.45 eV. The variation of band gap with film thickness could be qualitatively understood as due to the quantum confinement effect.