ELS-LEED investigations of dy-silicide nanostructures on silicon

Dysprosium silicide nanostructures have been grown by depositing up to 1ML of Dy on Si(111) and on vicinal Si(001) substrates. Ultra-high vacuum conditions (p≤1 x 10-10 mbar during Dy deposition) are prerequisite to avoid Dy oxidation. The atomic and electronic properties have been investigated using ELS-LEED, which allows the simultaneous study of geometric and electronic properties at the same point in k-space with both high momentum and energy resolution. Deposition of 1ML of Dy on Si(111) at RT followed by annealing at 500 C results in a flat monolayer with DySi2 stoichiometry. The diffraction pattern revealed the typical 1 x 1 structure. A 2D-Plasmon dispersion is reported for the first time with a √(q parallel) behavior up to q parallel =0.08 A-1 in k-space. High quality arrays of parallel nanowires have been grown on 4 -vicinal Si(001) at 500 C for a Dy coverage around 0.4 ML. A n x 2 periodicity has been found, with n shifting from 10 to 7 for increasing coverage up to 0.75 ML. The energy loss disperses only in the direction along the nanowires, whereas in the perpendicular direction the plasmon can not be excited. The plasmon dispersion turned out to be a quasi-1D-plasmon. It has been accurately simulated by explicitely taking into account the finite width of the DySi2 nanowire structures. Interactions between adjacent nanowires play a minor role