Atomic hydrogen beam etching of carbon superstructures on 6H-SiC (0001) studied by reflection high-energy election diffration

Abstract

A route for the regeneration of smooth √3 × √3 R30 face on 6H-SiC(0001) by atomic hydrogen beam etching following the carbonization of the SiC surface at high temperatures had been investigated. The various stages during the segregation of carbonaceous super-structures at high temperatures as well as the layer-by-layer restructuring of the 6H-SiC(0001) surface by atomic H beam were studied by reflection high energy electron diffraction (RHEED). A smooth silicate-terminated √3 × √3 R30 surface could be obtained after hydrogen-plasma beam treatment at 800°C. Annealing the √3 × √3 R30 face to 900°C readily resulted in the segregation of 1 x 1 graphite islands on the surface, with the basis vectors of the graphite unit cell rotated 30° with respect to the bulk SiC. Further annealing to temperatures between 1000 and 1200°C resulted in the coalescence of the graphite islands to form an epitaxial layer, which adopted an incommensurate 6√3 × 6√3 R30-C structure with respect to the bulk. The epitaxial 6√3 × 6√3 R30-C layer acted as a template for the further growth of smooth single-crystalline graphite multilayers upon prolonged annealing. Atomic force microscopic (AFM) analysis revealed that the epitaxial graphite formed by this method was atomically smooth. Re-exposing the graphite-covered surface to a second hydrogen-plasma treatment readily converted the carbonized surface to a silicate-terminated √3 × √3 R30 face. The layer-by-layer etching mechanism of the carbonized SiC by the atomic-H beam source constituted an effective route for the regeneration of the smooth silicon face. © 2001 Elsevier Science B.V. All rights reserved.