Structures of 6H-SiC Surfaces

Abstract
We have systematically studied reconstructions of the 6H SiC(0001) and (000-1) surface under both Si rich and C rich condition using field ion-scanning tunneling microscopy (FI-STM). The sample was cleaned by in situ Si beam etching at 900-1000 °C. The Si rich and C rich phases were produced by annealing the sample in a Si flux and C₂H₂, respectively. On the (0001) surface, the as-cleaned surface showed (√3x√3) reconstruction. With increasing Si concentration, (2x2), (2√3x6√3), (3x3), and (7x7) reconstructions were observed. Reaction of the Si rich phases with C₂H₂ molecule at 1050 °C resulted in the formation of C rich surface, which exhibited (2x2)/(6x6) reconstruction. On the (000-1) surface, (2√3x2√3) reconstruction was observed after cleaning. Under Si rich condition, (2x2), (3x3), and (7x7) reconstmctions were observed. Annealing the surface in C₂H₂ beam at 1050 °C led to C rich phase with (1x1) structure. Structure model for (√3x√3) and (2√3x2√3) reconstruction are proposed, and possible applications of using the surface reconstruction to selectively grow the polytype SiC is discussed.