Optical Properties of Cadmium Sulfide and Zinc Sulfide from 06 Micron to 14 Microns

Abstract

The index of refraction and the absorption of evaporated films of CdS and ZnS in the spectral region from 0.6 micron to 14 microns were determined from spectrophotometric reflectance and transmittance measurements. The index of refraction of CdS ranged from 2.52 at 0.6μ to 2.26 at 14μ and was independent of deposition rate. The index of ZnS varied from 2.34 at 0.6μ to 2.15 at 14μ and was independent of deposition rate. The absorption coefficient of CdS depended upon the deposition rate from 0.6μ to 6μ and increased beyond 6μ independently of deposition rate. The absorption coefficient of ZnS was approximately 0.001 in the region of investigation. Approximate formulas are given for calculating the index of refraction and absorption from the reflectance and transmittance when the absorption is small. A method is given for preparing the phosphors that yields films for which the index of refraction is independent of the deposition rate. The crystalline structure was investigated by means of x-ray diffraction.