Influence of low energy Ar-ion bombardment on monolayer Ni/W(1 0 0)

The changes in the morphological and structural properties of monolayer nickel thin films on tungsten induced by low energy Ar+ ion bombardment at varying fluencies have been explored using scanning tunneling microscopy and low energy electron diffraction, respectively, in this work. ~1 monolayer (ML) nickel films were grown on W(1 0 0) by electron beam evaporation under ultra high vacuum conditions at room temperature. It was found that the pseudomorphic growth observed in as-grown films was disrupted by the ion bombardment process with additional phases of Ni appearing in the ion bombarded samples. Increase in bombardment time lead to a pronounced phase transition to the hcp phase of Ni. Also, the ion bombardment induced the formation of larger nanostructures (with increasing particulate sizes) from the epitaxial monolayer in the as-deposited sample. Further, the magnetization and magnetic orientation were studied and it was observed that the bombardment induced a weak ferromagnetism in as-grown paramagnetic Ni film.