Origin of Chemical Order in a-SixCyHz: Density-Functional Tight-Binding Molecular Dynamics and Statistical Thermodynamics Calculations

Abstract

We investigate the growth mechanisms and structures of hydrogenated amorphous silicon carbide (a-SixCyHz) during chemical vapor deposition (CVD) by using density-functional tight-binding molecular dynamics (DFTB MD) and statistical thermodynamics (ST) calculations. Our multiscale modeling from an atomic to an experimental scale allows us to bridge the gap between micro- and macroscopic knowledge. As in any compound, the degree of chemical order in a-SixCyHz is of practical importance. However, the origin of chemical order and effects of composition on the degree of chemical order remain unknown. First, CVD simulations are performed by the impingement of CH3 and SiH3 radicals on a Si(001)-(2 × 1):H surface with DFTB MD. The initial growth process consists of an abstraction-adsorption mechanism, where a CH3 or SiH3 radical abstracts a H atom and forms a dangling bond (DB) on the surface, and a subsequent CH3 or SiH3 radical is adsorbed on the DB. A surface-adsorbed CH2 species with a DB is inserted into a n...