STM-STUDY OF GD W(110) AT SUBMONOLAYER COVERAGES/

We have studied the growth of Gd on a W(110) substrate at submonolayer coverages by means of scanning tunneling microscopy (STM). Gd forms d omains of equidistant chains along the [1(1) over bar0$] direction of the substrate. The distance between the chains decreases in discrete s teps with increasing coverage. These chain-like superstructures coinci de with the appearance of (n x 2) LEED-patterns (n = 10, 8, 7, 6, 5). Atomically resolved STM images support an earlier model which explains the chains by periodic adsorption in on-top and non-top sites. The ap parent corrugation of the chains exhibits a strong bias dependence whi ch can be explained by adsorption-site-dependent local electronic prop erties. Spatially resolved spectroscopy of the local barrier height is in excellent qualitative agreement with earlier spatially averaging e xperiments. (C) 1997 Elsevier Science B.V.