Significant Structural Distortion in the Surface Region of 4H-SiC Induced by Thermal Oxidation and Recovered by Ar Annealing

The impacts of O2-oxidation and Ar-annealing processes on the local lattice distortion at surface of thermally-oxidized 4H-SiC (0001) were investigated by using in-plane XRD. The surface oxidation induces a significant increase of the lattice constant, whereas Ar-annealing results in a gradual relaxation of it. From the x-ray penetration depth dependence of the observed lattice constant, those anomalous changes of lattice constants occur only in the surface region of SiC substrate.