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

PI route for the regeneration of smooth root3 x root3 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-tenninated root3 x root3 R30 surface could be obtained after hydrogen-plasma beam treatment at 800 degreesC. Annealing the root3 x root3 R30 face to 900 degreesC 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 degrees with respect to the bulk SiC, Further arnealing to temperatures between 1000 and 1200 degreesC resulted in the coalescence of the graphite islands to form an epitaxial layer, which adopted an incommensurate 6 root3 x 6 root3 R30-C structure with respect to the bulk. The epitaxial 6 root3 x 6 root3 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 root3 x root3 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.