Optical characterization of non-uniform thin films using imaging spectrophotometry

Abstract

In this paper the method of imaging spectrophotometry enabling us to characterize non-absorbing thin films non-uniform in the optical parameters is described. This method is based on interpreting the spectral dependences of the local absolute reflectances measured at the normal incidence of light. It is shown how to determine the area distribution of thickness and refractive index of the non-absorbing non-uniform thin films by treating these reflectances. Moreover, the generalization of the method for the optical characterization of slightly absorbing non-uniform thin films is also indicated. Furthermore, the two-channel imaging spectrophotometer enabling us to apply the method of imaging reflectometry is described. The procedure for determining the spectral dependences of the local absolute reflectance in the points aligned in a matrix situated on the illuminated area of the non-uniform thin film by means of the spectrophotometer is also presented. The practical advantages of the method are specified. The method is illustrated by means of the optical characterization of a selected epitaxial ZnSe thin film prepared using molecular beam epitaxy onto gallium arsenide single-crystal substrate.