High resolution images of Mo2C(0001)-(root 3 x root 3)R30 degrees structure by scanning tunneling microscopy

A (root 3x root 3)R30 degrees C-terminated structure on Mo2C(0001) was obse rved by scanning tunneling microscopy. The structure was observed as a hone ycomb structure with dark depressions corresponding to C atoms which make u p the (root 3 x root 3)R30 degrees lattice. High resolution imaging was pos sible at low tunneling resistance less than 1 M Ohm. Each C atom appears as a shallow sombrero protrusion predicted by theoretical calculations of C a toms on a metal substrates. It is concluded that the C atoms occupied three fold hollow sites of the (1 x 1) Mo layer of the substrate and a model for the (root 3 x root 3)R30 degrees structure is proposed. (C) 1999 Elsevier S cience B.V. All rights reserved.