Diffusion Mechanism of Hydrogen in Amorphous Silicon: <i>Ab Initio</i> Molecular Dynamics Simulation

Y.-S. Su; S. T. Pantelides

doi:10.1103/PhysRevLett.88.165503

Diffusion Mechanism of Hydrogen in Amorphous Silicon: Ab Initio Molecular Dynamics Simulation

Y.-S. Su and S. T. Pantelides

Phys. Rev. Lett. 88, 165503 – Published 8 April 2002

Abstract

The mechanism of H migration in amorphous Si has remained an unresolved problem. The main issue is the small activation energy (1.5 eV) relative to the known strength of Si-H bonds (2–3.5 eV). We report first-principles finite-temperature simulations which demonstrate vividly that H is not released spontaneously, as proposed by most models, but awaits the arrival of a floating bond (FB). The “migrating species” is an FB-H complex, with H jumping from Si to Si and the FB literally floating around it. Migration stops when the FB veers away.