MORPHOLOGY AND ATOMIC-STRUCTURE OF THE SIC(000(1)OVER-BAR)3X3 SURFACERECONSTRUCTION

The atomic structure of SiC(000 (1) over bar)C surface of the 6H polyt ype has been studied in UHV by scanning tunnelling microscopy, low ene rgy electron diffraction and Auger electron spectroscopy. A number of different reconstructions could be reproducibly prepared in UHV by a c ombination of annealing a sample with and without silicon flux al temp eratures in the range 450-1400 degrees C. One of them has been identif ied as SiC(000 (1) over bar)3 x 3 structure. A geometrical model of th is reconstruction has been proposed. In accordance with that. the unit cell consists of tell atoms bonding to produce six dimers and three a datoms. The six- and nine-atom rings surround unoccupied sites of the outermost carbon atoms of the SiC substrate. Each unit cell contains f ive dangling bonds. three of which are associated with adatoms and are responsible for protrusions in filled-state scanning tunnelling micro scopy images. The other two are associated with carbon atoms of the su bstrate. Furthermore, islands with an unreconstructed SiC(000 (1) over bar)1 x I surface prepared in UHV have been observed with atomic reso lution for the first time by means of STM. (C) 1997 Elsevier Science B .V.