LEEM investigation of the faceting of the Pt covered W(111) surface

A low energy electron microscope has been used to investigate the faceting of W(111) as induced by Pt. The atomically rough W(111) surface, when fully covered with a monolayer film of Pt and annealed to temperatures higher th an similar to 750 K, experiences a significant morphological restructuring: the initially planar surface undergoes a faceting transition and forms thr ee-sided pyramids with {211} faces. The experiments demonstrate the capabil ity of low energy electron microscopy for imaging both the fully and the pa rtially faceted surface. In addition, we have observed the formation of the facets in real time, when Pt is dosed onto the heated surface. We find tha t the transition from planar surface, to partially faceted surface, and to fully faceted surface proceeds through the nucleation and growth of spatial ly separated faceted regions. (C) 1999 Elsevier Science B.V. All rights res erved.