Growth and Characterization of PbI2 Thin Films by Vacuum Thermal Evaporation

The aim of this study was to investigate the morphology and optical absorption of PbI2thin films. PbI2films 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). PbI2seems to have a very strong affinity for the growth of preferred (001) orientation. The d spacing of (00l) peaks match quite well with ASTM data for 2H polytype of PbI2which 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.