6H-SiC{0001} X-ray photoelectron diffraction characterization used for polarity determination

Both (0001) and (000 (1) over bar) polar faces of a 6H-SiC monocrystal have been probed by X-ray photoelectron diffraction (XPD) for the first time. Thus, Mg K alpha excited C Is and Si 2p peak amplitude polar scans are compared for both faces in the high symmetry (10 (1) over bar 0) azimuth plane. Very different C Is and Si 2p patterns are observed. Their main angular features are explainable on the basis of forward focusing directions along atomic rows and according to scattering strength differences between C and Si scatterers. We also demonstrate that the A(C 1s)/A(Si 2p) peak amplitude or intensity ratios at specific analysis angles are mainly determined by the forward scattering phenomenon depending on particular C and Si atomic geometrical positions and scattering strengths and not obligatorily on the chemical surface termination (Si or C) of the face. Nevertheless, at normal electron emission angle (theta=theta') this ratio is effectively higher for the (000 (1) over bar) face and may be used as a quick polarity determination. The presence of a structure at theta= 58.5 degrees either in the C Is or Si 2p XPD pattern according to the polar face, confirm the assignments. Moreover, great care must be taken when surface stoichiometry has to be derived from similar C Is and Si 2p intensity ratios without considering the XPD phenomenon. (C) 1998 Elsevier Science B.V. All rights reserved.