Effect of low-temperature annealing on the void-induced microstructure in amorphous silicon: A computational study

TL;DR

This computational study investigates how low-temperature annealing affects the microstructure and morphology of voids in amorphous silicon, revealing significant surface restructuring without necessarily changing scattering intensity profiles.

Contribution

It provides new insights into the atomic-level effects of annealing on void surfaces and their microstructural evolution in amorphous silicon.

Findings

Void surface restructuring occurs at low temperatures

Void shape changes are visible in 3D but not in scattering plots

Annealing influences the microstructure without altering scattering intensity

Abstract

We present a computational study of the void-induced microstructure in amorphous silicon ($\it a$-Si) by generating ultra-large models of $\it a$-Si with a void-volume fraction of 0.3$\%$, as observed in small-angle x-ray scattering (SAXS) experiments. The relationship between the morphology of voids and the intensity of scattering in SAXS has been studied by computing the latter from the Fourier transform of the reduced pair-correlation function and the atomic-form factor of amorphous silicon. The effect of low-temperature ($\le$ 600 K) annealing on the scattering intensities and the microstructure of voids has been addressed, with particular emphasis on the shape and size of the voids, by studying atomic rearrangements on the void surfaces and computing the average radius of gyration of the voids from the spatial distribution of surface atoms and the intensity plots in the Guinier approximation. The study suggests that low-temperature annealing can lead to considerable restructuring of void surfaces, which is clearly visible from the three-dimensional shape of the voids but it may not necessarily reflect in one-dimensional scattering-intensity plots.