D-STATE CONTRIBUTION TO STM - STRUCTURE OF VAN-DER-WAALS SURFACE (TASE2, MO0.5W0.5SE2) AND RELEVANCE FOR CATALYSIS

Scanning tunneling microscopy studies of 2H-TaSe2 in air show both the chalcogen surface atoms and the second-layer tantalum atoms. The char ge-density peaks of the latter are shifted from their supposed atom co re positions by approximately 0.8 angstrom in the [110] direction away from the nearest Se atom. The appearance of the metal atom charge den sity near the surface on van der Waals surfaces explains why photocata lysis is possible with transition metal layer dichalcogenides despite the apparently saturated surfaces. Buckling of the surface layer of Mo 0.5W0.5Se2 is observed.