Adsorption and compound formation of Yb on Ni(100)

Abstract

The adsorption and compound formation of Yb on Ni(100) is studied by AES, ISS, LEED and XPS. The deposition of Yb is followed at two substrate temperatures, room temperatures and 670 K. Yb deposition at 670 K results in the formation of ordered structures. An incommensurate structure is attributed to adsorbed Yb, a c(10 × 2) and a slightly distorted hexagonal structure result from the formation of ordered Yb Ni compound layers. Intermixing between Yb and Ni occurs only above a certain Yb threshold coverage. Different valence states of the Yb atoms are revealed by XPS. Divalent Yb is found at the surface for all Yb depositions. Trivalent Yb is located in the bulk of the compound and, in certain coverage regions, also at the surface. Room temperature deposition of Yb does not lead to any ordered structures. At low coverages the room temperature structures can in many respects be considered as disordered versions of the 670 K structures. At higher Yb deposition no strong intermixing with the Ni occurs. Instead an Yb film starts growing.