TEMPERATURE-INDUCED SEMICONDUCTING C(4X2) DOUBLE-LEFT-RIGHT-ARROW METALLIC (2X1) REVERSIBLE PHASE-TRANSITION ON THE BETA-SIC(100) SURFACE

We use combined variable temperature scanning tunneling microscopy and spectroscopy, and angle-resolved photoemission spectroscopy experimen ts to study transition between two beta-SiC(100) surface structures. W e observe a reversible temperature-dependent phase transition from a s emiconducting c(4 X 2) surface at 25 degrees C to a metallic 2 X 1 str ucture at 400 degrees C. This transition results from temperature-indu ced disruption df the c(4 X 2) structure composed of alternately up an d down dimers into a structure having all dimers at the same height gi ving a 2 X 1 symmetry. This arrangement favors electronic orbital over lap between Si top surface atoms leading to surface metallization. [S0 031-9007(97)04495-5].