Network Rebonding Model for Metastability in Amorphous Silicon

Abstract

ABSTRACTWe propose a new network rebonding model to describe light-induced metastability in hydrogenated amorphous silicon. This model involves global changes in both the silicon and hydrogen bonding sites. The first step in the process is the breaking of a weak silicon bond generating a dangling bond and floating bond pair. The mobile floating bond diffuses away leaving behind an isolated dangling bond in agreement with ESR measurements. Tight-binding molecular dynamics simulations show clear evidence for each of these processes. Floating bonds are an intermediate transient species that do not remain in the light-soaked steady state. Floating bonds annihilate by reacting with SiH bonds and locally displacing hydrogen atoms. This model provides a new explanation for several major experimental features of the Staebler-Wronski effect, including the t1/3 kinetics for the growth of defects, and the anticorrelation of dangling bonds with H. This new model provides a new platform for understanding the atomistic origins of light-induced degradation.