The kinetics of lattice distortion introduction and lattice relaxation at the surface of thermally-oxidized 4H-SiC (0001) were investigated. Our results suggested that lattice distortion introduction and lattice relaxation seem to follow zeroth and second order rate laws, respectively. The obtained activation energy of ∼3.9 eV for lattice distortion introduction and ∼1 eV for its relaxation indicate that the lattice distortion is determined by a bond rearrangement or movement process with a relatively low activation energy. Furthermore, the formation of byproducts which remain at the surface region of 4H-SiC was predicted to be a possible origin of the significant lattice distortion.

Local lattice distortions at the surface of 4H-SiC(0001) after various thermal oxidation processes were investigated by in-plane X-ray diffractometry. Our results showed that dry oxidation induced lattice distortion, observed as the increase of ð1 100Þ interplanar spacing, became higher with increasing oxidation time. Lattice constant changes of up to >0.4% were observed by increasing the oxide thickness to 44 nm. This lattice distortion was not recovered after removal of the SiO 2 layer by chemical etching, although it was partially reduced by Ar gas annealing, suggesting that strain relaxation requires removal of oxidation-induced defects in the 4H-SiC surface region.

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.