Measurements of optical properties for thin amorphous silicon films using spectroscopic ellipsometry

Optical and structural properties of amorphous silicon thin films have been characterized using spectroscopic ellipsometry. Second derivatives of imaginary dielectric functions with respect to energy are compared to obtain the film thickness and dielectric functions. Etching-off the surface oxide is effective in determining the correct film thickness and dielectric functions. Complex dielectric functions are found to decrease with film thickness at a lower photon energy. The decrease is explained by the existence of a low-density amorphous silicon layer on silicon substrate. For thick films, the structure is found to consist of a low-density interface layer, an amorphous layer, and a low-density surface layer