RING FORMATION AND THE STRUCTURAL AND ELECTRONIC-PROPERTIES OF TETRAHEDRAL AMORPHOUS-CARBON SURFACES

In this paper, we report first-principles structural models of surface s of tetrahedral amorphous carbon (ta-C). The topology and defect stru cture of the amorphous surfaces are analyzed at the atomistic level. W e examine the transition of the local bonding environment from the bul k to the surface. Comparing the surface with the bulk, many more surfa ce atoms are threefold coordinated and planar rings or chains are form ed with the sp(2) bonds. This ''graphization'' character of the ta-C s urface also significantly influences its electronic properties. Electr ons are easily delocalized within these surface sp(2) rings/chains and some of the surface electronic eigenstates become extended along the surface through such rings/chains. The implications of surface graphiz ation for the growth and surface conduction are briefly discussed.