The electronic structure of gadolinium grown on Mo(112)

Abstract

The electronic structure of strained ultra-thin and thin films of Gd grown on a corrugated Mo(112) surface are described. Gadolinium overlayers order at a coverage of monolayers forming a LEED pattern. At this coverage an interface state of symmetry is formed at a binding energy of at the surface Brillouin zone centre . The effective mass of this interface state was determined to be , in both orthogonal directions along the nearly square reduced Brillouin zone. For thicker Gd films of approximately 3 to 10 ML thickness, the corresponding gadolinium state switches symmetry to the representation (Gd or 6s character) and has a much larger effective mass. The overlayer forms a rectangular surface Brillouin zone resembling the hcp surface. Gadolinium films thicker than approximately 10 ML form strained hexagonal ordered films also with substantial misfit dislocations. The strain of the thin hexagonal ordered Gd films is reflected by a reduced Brillouin zone size along by approximately 4% with respect to the less strained Gd overlayers on W(110) and Gd(0001) single crystals. The induced strain severely alters the band structure of the Gd 5d/6s bulk bands, which disperse in the opposite direction relative to the corresponding bands of the relaxed Gd(0001) structure. The surface of the strained hexagonal fcc (111) or hcp (0001) Gd films forms a localized state of symmetry (Gd or 6s character) at approximately 0.7 eV binding energy. There is little observed strain relief within the Gd films up to approximately 150 Å film thickness.