Faceting induced by ultrathin metal films on W(111): Structure reactivity, and electronic properties
- Rutgers Univ., Piscataway, NJ (United States)
We have studied ultrathin films of transition and noble metals on W(111) using Auger spectroscopy, LEED, thermal desorption spectroscopy (TDS), catalytic reactivity measurements, and scanning tunneling microscopy (STM). The atomically rough, open W(111) surface is morphologically unstable when covered by films {>=}1 monolayer thick of certain metals; upon annealing to T > 750K, pyramidal faceted structures (average dimensions {approximately}2 to 15 nm) completely cover the surface. Formation of pyramidal facets with (211) orientations occurs when W(111) is dosed with Pd, Rh, Ir, Pt, Au, oxygen or sulfur. In contrast, monolayer films of Ti, Co, Ni, Cu, Ag and Gd do not induce faceting on W(111). The faceting appears to be thermodynamically driven but kinetically limited: faceting is caused by an increased anisotropy in surface free energy that occurs for the film-covered surfaces. Structure sensitivity in a model catalytic reaction, n-butane hydrogenolysis, is observed over planar and faceted Pt/W(111) and is compared with Pt/W(211).
- OSTI ID:
- 370779
- Report Number(s):
- CONF-960376--
- Country of Publication:
- United States
- Language:
- English
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