Optical properties of self-ion-implanted Si(100) studied by spectroscopic ellipsometry

Microstructural and optical properties of self-ion-implanted Si(100) have been studied using atomic force microscopy (AFM) and spectroscopic ellipsometry. The Si+ ions are implanted at 150 keV with fluences ranging from 2x10(14) to 2x10(15) cm(-2). The AFM image indicates that the Si(100) surface is shiny flat before and after Si+-ion implantation (rms roughness of similar to0.3 nm). An effective-medium approximation and a linear regression analysis suggest that the ion-implanted surface can be explained by a physical mixture of microcrystalline (muc-) and amorphous silicon (a-Si). It has been shown that the complex dielectric function epsilon (E) of muc-Si differs appreciably from that of c-Si, especially in the vicinity of the sharp critical-point features. This difference in epsilon (E) can be successfully explained by increasing the broadening value at each critical point. The volume fraction of a-Si is found to be simply expressed as f(a)=([Si+]/A)(alpha), where [Si+] is the ion fluence in cm-2, A (=1.4x10(15) cm(-2)) is an amorphization-threshold fluence, and alpha(=1.42) is an amorphization-rate factor of the Si+ ions. (C) 2001 American Institute of Physics.