Charge-induced effects on the structure and properties of silane and disilane derivatives

TL;DR

This study uses ab-initio methods to analyze how charging affects the structure, bonding, and vibrational properties of silicon hydride clusters relevant to plasma-enhanced chemical vapor deposition of hydrogenated amorphous silicon.

Contribution

It provides new insights into the structural distortions, bond formations, and vibrational shifts in charged silicon hydride clusters, advancing understanding of their role in film deposition processes.

Findings

Charging distorts cluster structures via Si-H bond orientation.

Hydrogen forms Si-H-H and Si-H-Si bonds in some charged clusters.

Vibrational frequencies shift significantly upon charging, correlating with bond length changes.

Abstract

Using ab-initio electronic structure methods we have investigated the ground state structures and properties of neutral and charged SiH$_{m}$(m=1-4) and Si$_{2}$H$_{n}$(n=1-6) clusters which are produced in the plasma enhanced chemical vapor deposition process used in the preparation of hydrogenated amorphous silicon({\it{a}}-Si:H). Our results show that charging a neutral cluster distorts it and the distortion mainly occurs through the orientation of Si-H bond. We attribute structural changes in the charged clusters to electrostatic repulsion between the bonded and non-bonded electrons. We find that in addition to the usual Si-H bond, hydrogen atoms form Si-H-H and Si-H-Si bonds in some clusters. The vibrations of Si-H, Si-Si, Si-H-Si bond stretching modes show that the frequencies are shifted significantly upon charging. The frequency shifts in the charged clusters are consistent with their bond length variations. We discuss the fragmentation pathways of silane into binary products and the role of fragmented silane radicals in the cluster formation and {\it{a}}-Si:H film deposition process.