Hydrogen dynamics and light-induced structural changes in hydrogenated amorphous silicon

TL;DR

This study employs first principles methods to investigate hydrogen motion and light-induced structural changes in hydrogenated amorphous silicon, revealing formation pathways of dihydride structures and insights into the Staebler-Wronski effect.

Contribution

It introduces a simple procedure to track hydrogen dynamics in light-excited states and provides detailed pathways for structural transformations in hydrogenated amorphous silicon.

Findings

Dihydride structures form under light excitation.

Light induces creation of separated dangling bonds.

Simulations align with experimental observations of the Staebler-Wronski effect.

Abstract

We use accurate first principles methods to study the network dynamics of hydrogenated amorphous silicon, including the motion of hydrogen. In addition to studies of atomic dynamics in the electronic ground state, we also adopt a simple procedure to track the H dynamics in light-excited states. Consistent with recent experiments and computer simulations, we find that dihydride structures are formed for dynamics in the light-excited states, and we give explicit examples of pathways to these states. Our simulations appear to be consistent with aspects of the Staebler-Wronski effect, such as the light-induced creation of well separated dangling bonds.