Kinetics and thermodynamics of silicon carbide physical vapor transport reactions: A quantum chemistry and kinetic Monte Carlo approach

Abstract

The thermodynamics and chemical kinetics of silicon carbide sublimation and lateral interaction reactions are two vital branches that aid in understanding silicon carbide crystal growth, in the Physical Vapor Transport process (PVT). Whilst the former determines the feasibility of the processes and gives an idea about end products and their stability, kinetics explains the dynamism of the reactions and the contribution of species to crystal growth. The potential energy surfaces of the reactions are first determined via Born Oppenheimer Molecular Dynamics observation of the reaction kinetics. By employing an atomic basis set of split-valence double-zeta coupled with Becke’s three-parameter hybrid method with LYP correction function, the trajectory of different reactant configurations confirming minimum energy molecules, end products, and potential energy surface is established. Various structural possibilities for the reactant, intermediates, and product of each reaction are investigated by means of geometry optimization and utilization of second-order Moller-Plesset level of theory with electron correlation and a basis set of split-valence triple-zeta polarization. Reaction paths are ascertained via QST2 transition state calculation and their mechanism is confirmed by intrinsic reaction coordinate (IRC). Rate constants for forward and reverse processes are estimated using appropriate and applicable theories, adequate to capture the scenarios. Sublimation of silicon carbide source powder is solved thermodynamically at equilibrium using the equation of Gibbs free chemical reaction isotherm, and the equilibrium partial pressures of species in ideal conditions and Kinetic Monte Carlo evolution of the PVT reactions species, were used in determining the most dominant gaseous molecules around the substrate.