Coordination defects in a-Si and a-Si:H : a characterization from first principles calculations

TL;DR

This study uses first-principles calculations to analyze coordination defects in amorphous silicon and hydrogenated amorphous silicon, revealing how hydrogen interaction influences defect states and electronic properties.

Contribution

It provides a detailed first-principles characterization of T_3 and T_5 defects and their evolution with hydrogen, clarifying their role in electronic gap states.

Findings

Hydrogen reduces defect-related states in the electronic gap.

Three-fold and five-fold coordinated defects are clearly identified.

Hydrogen interaction can mitigate electronic gap states associated with defects.

Abstract

We study by means of first-principles pseudopotential method the coordination defects in a-Si and a-Si:H, also in their formation and their evolution upon hydrogen interaction. An accurate analysis of the valence charge distribution and of the ``electron localization function'' (ELF) allows to resolve possible ambiguities in the bonding configuration, and in particular to identify clearly three-fold (T_3) and five-fold (T_5) coordinated defects. We found that electronic states in the gap can be associated to both kind of defects, and that in both cases the interaction with hydrogen can reduce the density of states in the gap.