Optical properties of lead iodide between 0.4946 and 6.185 eV

The optical and dielectric constants of Pbl(2) thin films have been determined from transmittance and reflectance measurements, for photon energies between 0.4946 and 6.185 eV. The absorption coefficient, bandcap energy, and dielectric constants were determined at room temperature by the normal incidence method. The first three lines of the hydrogenic exciton series associated with the absorption edge are well resolved in reflectivity measurements. The transmittance measurements enable the evaluation of the value of bandgap energy E-g. The bandgap energy of Pbl(2) at room temperature was found to be 2.55 eV. A careful analysis of the absorption coefficients indicated the crystalline character of the sample studied; a similar diagnosis was obtained from X-ray evidence. SEM analysis revealed that as the thickness of the films increases the material becomes amorphous. (C) 2003 Kluwer Academic Publishers.