Growth of ultrathin In layers on W(1 1 0) studied by high-resolution electron spectroscopies

We have studied the growth of In on W(1 1 0) at room temperature using low-energy electron diffraction, photoemission from core-levels and valence states, and thermal desorption. At submonolayer coverage three ordered phases can be clearly resolved. Between 0.2 and 0.3 ML LEED observes a c(3 × 2) structure rotated by 90° with respect to a c(1 × 1) substrate unit mesh. With increasing coverage a striped phase develops around 0.6 ML, characterized by a (1 × 1) lattice within the stripes and furrows oriented along the [0 0 1] substrate bulk direction. The width of the stripes along [1 1 0] is six atomic rows. At 0.8 ML the stripes increase their width to eight atomic rows without changing their orientation. This interpretation of the LEED data is based on the observed work-function change and, in particular, high-resolution studies of the In 3d, In 4d, W 4p and W 4f core-levels. Using different techniques we analyze their binding energy, intensity and width in their dependence on the average thickness of the In overlayer.