Ultrathin metal films on W(111): morphology and faceting reconstruction

Abstract

The structure and morphology of Rh, Ir, Ti, Co, Ni, Cu, Ag and Gd ultrathin films on W(111) have been investigated by means of Auger electron spectroscopy (AES), low energy electron diffraction (LEED) and temperature programmed desorption (TPD). Upon annealing to 700 K, Rh and Ir overlayers with a critical coverage of at least one physical monolayer, as well as chemisorbed S, induce reconstruction of the W(111) substrate to form pyramidal facets with {211} orientation. In contrast, for overlayers of Ti, Co, Ni, Cu, Ag and Gd on W(111), no evidence for metal film induced faceting of the substrate has been observed for any coverage or annealing temperature. A comprehensive analysis of the physical, chemical and electronic properties of both metal and non-metal overlayers strongly suggests that the electronic structure plays a dominant role in causing surface instability of W(111).