PNNL

Abstract

A model has been created based on scattering from internal surfaces of different refractive index that describes the ?-2 dependence of the extinction in bulk samples of CVD ZnS. The model hinges on the lamellar nanostructure composed of alternating layers of thickness on the order of 10 to 100 nm. A family of solutions is generated which depend on both the difference in refractive index (?n) and the layer thickness. Reasonable layer thicknesses require ?n for CVD ZnS with higher values than can be explained solely by the ?n between sphalerite and wurtzite phases of ZnS. Other evidence suggests a substantial oxygen component in CVD ZnS that could result in the lower refractive index Zn(O,S) necessary for the model. Differences in transmission for CVD ZnS, elemental ZnS, and multispectral ZnS can be explained simply by a different magnitude of ?n between the layers. Absolute transmission is modeled satisfactorily from the band edge to 10 µm using this approach.