Evaluation of light refractive index in silica thin films

Light refractive index is an important constant in design of optical thin films and its value vary with variations of film thickness and density, crystal structure and internal defects. Accident electromagnetic waves on surface layer in proportion with various amounts of refractive index, absorb, reflect and or trasmit through the layer and some are diffracted because of surface and internal defects. Silica thin films in pure form or in combination with other oxides have considerable applications for optical properties.In this research, the effects of thickness and porosity in thin films of silica on refractive index and also the degree of light transmission through deposited layers was evaluated. With the aid of Sol-Gel method, silica was deposited on soda- lime glass specimens. Structural examinations of the layers were carried out, using Scanning Electron Microscopy (SEM), Energy Dispersion Analysis of X- ray (EDAX) and X-ray Diffraction technique (XRD). Also, by using light spectrophotometry, the spectrum of transmitted and absorbed rays, from the surface layers were prepared and compared. The results indicate that the layer thickness and porosity, have an effect on the degree of transmitted and absorbed waves. As the layer thickness is reduced, the amount of refractive index is reduced and the ability of transmitted light increase.