Adsorption studies of cobalt on tungsten (110), (100) and (111) planes by probe-hole field emission microscopy

Abstract

The changes in the workfunction, Δφ, and in the Fowler-Nordheim pre-exponential factor, ln B, have been investigated for cobalt adsorption on tungsten (110) (100) and (111) planes by probe-hole field emission microscopy. The workfunction variations have been found to be strongly dependent on the temperature in the range 300–580 K on these planes. Δφ decreases with submonolayer coverages of cobalt on the W(110) and W(100) planes. On the W(111) plane, Δφ initially decreases and then exhibits a jump towards positive values at relatively higher does. This abrupt increase in Δφ and the corresponding zero crossover of ln B have been attributed to surface reconstruction. The results are discussed in terms of the electronic structure and the degree of strain produced in the pseudomorphically grown cobalt layers on various crystallographic planes of tungsten.