Small-angle X-ray scattering in amorphous silicon: A computational study

TL;DR

This computational study investigates how small-angle X-ray scattering (SAXS) reveals the morphology and microstructure of voids in amorphous silicon, highlighting the sensitivity of scattering intensity to void size and volume fraction.

Contribution

The paper introduces a large-scale computational model of amorphous silicon with voids, linking SAXS intensity to void characteristics and comparing different methods to estimate void size.

Findings

SAXS intensity is highly sensitive to void size and volume fraction.

Void shape has a less significant impact on scattering profiles.

Simulated void sizes agree with those from experimental methods.

Abstract

We present a computational study of small-angle X-ray scattering (SAXS) in amorphous silicon ($a$-Si) with particular emphasis on the morphology and microstructure of voids. The relationship between the scattering intensity in SAXS and the three-dimensional structure of nanoscale inhomogeneities or voids is addressed by generating ultra-large high-quality $a$-Si networks with 0.1-0.3% volume concentration of voids, as observed in experiments using SAXS and positron annihilation spectroscopy. A systematic study of the variation of the scattering intensity in the small-angle scattering region with the size, shape, number density, and the spatial distribution of the voids in the networks is presented. Our results suggest that the scattering intensity in the small-angle region is particularly sensitive to the size and the total volume-fraction of the voids, but the effect of the geometry or shape of the voids is less pronounced in the intensity profiles. A comparison of the average size of the voids obtained from the simulated values of the intensity, using the Guinier approximation and Kratky plots, with those from the spatial distribution of the atoms in the vicinity of void surfaces is presented.