Surface Driven Mn-Doping of Ge Quantum Dots - Mn-Interaction with the Ge QD{105} Facet and the Wetting Layer

The interaction of Mn with Ge quantum dots (QD), which are bounded by {105} facets, and the strained Ge wetting layer (WL), terminated by a (001) surface, is investigated with scanning tunneling microscopy (STM). Mn is deposited on the Ge QD and WL surface in sub-monolayer concentrations, and subsequently annealed up to temperature of 400 C. Bonding and surface topography were measured with STM during the annealing process. Mn forms flat islands on the Ge {105} facet, whose shape and position is guided by the rebonded step reconstruction. The images show a hybridization of Mn-d band and empty states of the Ge{105} facet. A statistical analysis of Mn-islands on the QD yields a slight preference for edge positions, whereas the QD strain field does not impact Mn-islands. The formation of ultra-small Mn-clusters dominates on the Ge(001) WL, which contrasts the Mn-interaction with unstrained Ge(001) surfaces. Annealing (