Optical Properties of Amorphous Si Partially Crystallized by Thermal Annealing

Spectroscopic ellipsometry (SE) has been used to study optical properties of amorphous (a-) Si partially crystallized by thermal annealing. The a-Si samples used were prepared by rf sputtering on (100)Si. A linear regression analysis (LRA) and a Bruggeman effective-medium approximation (EMA) indicate that the annealed layer consists of volume fractions of a-Si and microcrystalline (?c-) Si. Isothermal annealing experiments at 1100?C suggest that the crystallization starts to occur very quickly (?30 min) and then slows with an increase in the annealing time. The complex dielectric functions of ?c-Si deduced here differ appreciably from that of crystalline (c-) Si, especially in the vicinity of the sharp critical-point (CP) features. Analyses are also presented on the dielectric-function spectra of ?c-Si using a simplified model of the interband transitions.