Scanning tunneling microscopy investigation of the C-terminated beta-SiC(100) c(2 x 2) surface reconstruction: dimer orientation, defects and antiphase boundaries

We investigate beta-SiC(100) c(2 x 2) surface reconstruction by atom-resolv ed scanning tunneling microscopy (filled and empty electronic states). The results indicate that, contrary to previous knowledge, the C=C triple-bond dimers that compose this surface are asymmetric and all tilted in the same direction (i.e. not anticorrelated), which suggests a compressive stress al ong the dimer direction. We also identify two specific defects: double dime r lines that are at the origin of antiphase boundaries, and missing dimers. In the latter case, the two nearest dimer neighbors along the dimer row ar e found to undergo a significant charge redistribution, leading to one of t hem being tilted in the opposite direction. (C) 2000 Elsevier Science B.V. All rights reserved.