Temperature-induced nanostructural evolution of hydrogen-rich voids in amorphous silicon: A first-principles study

TL;DR

This study uses first-principles simulations to investigate how temperature affects the nanostructure of hydrogen-rich voids in amorphous silicon, providing insights into atomic dynamics and structural evolution.

Contribution

It introduces a combined approach of classical molecular dynamics and ab initio density-functional simulations to analyze void evolution in amorphous silicon at different temperatures.

Findings

Temperature influences void shape and size in amorphous silicon.

Hydrogen dynamics near void surfaces are characterized.

Results align with small-angle X-ray scattering data.

Abstract

The paper presents an $ab$ $initio$ study of temperature-induced nanostructural evolution of hydrogen-rich voids in amorphous silicon. By using large $a$-Si models, obtained from classical molecular-dynamics simulations, with a realistic void-volume density of 0.2%, the dynamics of Si and H atoms on the surface of the nanometer-size cavities were studied and their effects on the shape and size of the voids were examined using first-principles density-functional simulations. The results from $ab$ $initio$ calculations were compared with those obtained from using the modified Stillinger-Weber potential. The temperature-induced nanostructural evolution of the voids was examined by analyzing the three-dimensional distribution of Si and H atoms on/near void surfaces using the convex-hull approximation, and computing the radius of gyration of the corresponding convex hulls. A comparison of the results with those from the simulated values of the intensity in small-angle X-ray scattering of $a$-Si/$a$-Si:H in the Guinier approximation is also provided, along with a discussion on the dynamics of bonded and non-bonded hydrogen in the vicinity of voids.