Reaction of nitrous oxide and ammonia molecules at 4H-SiC/SiO2 interface: An ab initio study

•The reaction N2O and NH3 molecules at 4H-SiC /SiO2 interface are theoretically investigated.•The desorption of carbon oxide in addition to Si–N bond formation occurs in the N2O reaction.•Various atomic configurations are formed depending on the plane orientation in the NH3 reaction.•The energy barriers for the N2O and NH3 reactions are higher than that of the NO reaction. [Display omitted] The reactions of N2O and NH3 molecules at the interface between 4H-SiC and SiO2 during post oxidation annealing (POA) are theoretically investigated using ab initio calculations. We find that the reactions of N2O molecule at (0001) and (0001¯) interfaces result in the desorption of carbon oxide molecules in addition to Si–N bond formation. For the reaction of NH3 molecule, various atomic configurations are formed depending on the plane orientation. Furthermore, the energy barriers for the N2O and NH3 reactions are found to be higher than that of the NO reaction owing to different atomic configurations at the transition state structure. The calculated results shed some insights for understanding POA process at 4H-SiC/SiO2 interfaces.