LEEM study of high-temperature oxygen structures on W(110) and their transformations

High-temperature reorganization of the adsorbed oxygen on the W(110) surface was investigated using low-energy electron diffraction (LEED) and low-energy electron microscopy (LEEM). Using these two techniques, we have resolved two out of three high-temperature tungsten oxide phases reported in the literature. We verified the structural properties of oxygen adsorbed on tungsten by comparing bright- and dark-field LEEM images. In particular, we determined the relationship between atomic steps and the occurrence of a specific structural domain in different phases. Finally, we described the temperature-induced structural transformation that was directly observed, both in real and reciprocal space, for two oxygen surface phases formed on W(110). By careful examination, it was proven that under specific circumstances, this transition can be conducted in both directions, and it is possible to halt it at any stage.