Predicting Raman line shapes from amorphous silicon clusters for estimating short-range order

A theoretical model obtained based on direct matrix method and bond polarization model (DMM-BPM) has been used to predict Raman scattering line shape for amorphous silicon (a-Si). These line shapes can describe the observed nonunique peak position from these a-Si crystallites, unlike crystalline Si, that varies between 470 and 485 cm(-1). The model has been validated using three different sets of Raman scattering data by fitting it with the proposed model. The Raman spectra are obtained from a-Si samples prepared by three different methods by three different research groups reported earlier. Clear consonance with the experimentally observed and theoretical Raman line shape was obtained. The model has also been used to estimate the distance up to which the crystallinity remains intact in a-Si. The used model has been compared with the existing phonon confinement model, and a discrepancy (in the latter) therein has been discussed. Rationale behind adopting this model has been explained using the constraints related to the Raman selection rule, their relaxation, or breakdown in appropriate materials' regimes. A handy empirical relation between Raman peak position and amorphous cluster size has been proposed.

Automated summary

A theoretical model using direct matrix method and bond polarization model has been developed to predict Raman scattering line shape for amorphous silicon, successfully capturing the nonunique peak position observed between a-Si crystallites. The model has been validated using three different sets of Raman scattering data and proposes an empirical relation between Raman peak position and amorphous cluster size.