On the Origin and Structure of the First Sharp Diffraction Peak of Amorphous Silicon

The structure of the first sharp diffraction peak (FSDP) of amorphous silicon (a-Si) near 2 angstrom(-1) is addressed with particular emphasis on the position, intensity, and width of the diffraction curve. By studying a number of continuous random network (CRN) models of a-Si, it is shown that the position and intensity of the FSDP are primarily determined by radial atomic correlations in the amorphous network on the length scale of 15 angstrom. A shell-by-shell analysis of the contribution from different radial shells reveals that key contributions to the FSDP originate from the second and fourth radial shells in the network, which are accompanied by a background contribution from the first shell and small residual corrections from the distant radial shells. The results from numerical calculations are complemented by a phenomenological discussion of the relationship between the peaks in the structure factor in the wavevector space and the reduced pair-correlation function in the real space. An approximate functional relation between the position of the FSDP and the average radial distance of Si atoms in the second radial shell in the network is derived, which is corroborated by numerical calculations.

Automated summary

The study focuses on the structure of the first sharp diffraction peak (FSDP) in amorphous silicon, showing that the key contributions come from the second and fourth radial shells in the network, with smaller contributions from other distant radial shells.