Material Science Forum 457-460 (2004) 415-416

Tailoring the SiC subsurface stacking by thechemical potential

U.Starke1, J.Bernhardt2, J.Schardt2, A.Seubert2 and K.Heinz2

1MaxPlanckInstitutf¨orperforschung,Heisenbergstr.1,D70569Stuttgart,Germany


2Lehrstuhl für Festkörperphysik,Universit Erlangen-Nürnberg,Staudtstr.7,D91058Erlangen,




Keywords: Surface Structure, Reconstruction, Stacking Sequence, Surface Stacking, Polytypes, Heterostructures, LowEnergy Electron Diffraction, Hexagonal Surface,
Surface
, SiC(0001), 6HSiC, 4HSiC, (3×3)R30, SiC(0001)


Abstract: The stacking orientation of bilayers determines the polytype of SiC material. For the development of polytype heterojunctions a controlled switch from one
stacking sequence to another is required. In the present paper it is demonstrated for 4HSiC and 6HSiC, that the chemical environment during preparation of the
(
3×3)R30 reconstruction on SiC(0001) influences the bilayer stacking in the topmost surface region.
A silicon rich growth environment results in three bilayers in identical orientation at the very surface, which in the case of 4HSiC corresponds to breaking the bulk
stacking sequence. Oxygen rich preparation conditions lead to a reduction to two identically oriented bilayers for both polytypes. The reconstruction geometry of the
(3×3)R30 phase is independent of the polytype and the terminating stacking sequence of the underlying material. In consequence, the surface stacking and as
suc
h the starting point of a polytype heterojunction can be taylored by the chemical potential.