The surface structure of the 〈110〉 zone of tungsten: A LEED and work function study

Abstract

The surface structure of a cylindrical tungsten single crystal with its axis parallel to a 〈110〉 direction is examined by LEED and for work function change. Three kinds of surfaces are distinguished: the atomically smooth low index planes, their stepped vicinal regions and what are termed the atomically rough planes, far from any low index orientation. For low index planes, LEED patterns and work function values in agreement with those from plane crystals are observed. For all surface orientations, a good correlation between calculated and measured LEED reflection splitting is found. Dipole moments per step edge atom are given and compared with values found in the literature. The atomically rough surfaces are found to be stable with respect to facetting into low index planes and dipole interactions between the outermost surface atoms appear to govern the work function. It is shown that any surface orientation can be unambiguously determined by LEED measurements alone.