Regensburg 2013 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 65: Surface and Interface Magnetism II (jointly with MA)
O 65.1: Vortrag
Donnerstag, 14. März 2013, 10:30–10:45, H33
Deviation from Coulombic behavior in short-range interactions of atoms on the GaAs(110) surface — •David Gohlke1,2 and Jay Gupta1 — 1Ohio State University, Columbus, OH USA — 2Universität Regensburg, Regensburg, Germany
Mn-doped GaAs is a prototypical dilute magnetic semiconductor where substitutional Mn act as electron acceptors while their magnetic moment allows for long-range magnetic interactions. By using low-temperature (5K) scanning tunneling microscopy (STM), we examine the electronic properties of individual Mn dopants in GaAs. We have previously shown that the binding energy of the Mn electron acceptor state can be tuned by controlled atomic-scale placement of a nearby charged defect, and that the shift of the binding energy due to repulsion between the bound hole and these charged defects follows a 1/r Coulombic behavior [Lee and Gupta, Science (2010), Gohlke et al., submitted]. Here we will discuss our observations of deviations from the 1/r behavior. First, our data show that the anisotropy of the GaAs(110) surface affects the interaction between Mn acceptors and charged adatoms. Second, for charged defects brought within 2nm of the acceptor, we observe defect-induced band bending that changes the occupancy of a hybridized Mn state located in the valence band, resulting in a turnaround behavior of the measured resonance energy. This research has implications in studying the interactions between atoms in Mn-doped GaAs, a material for which the mechanisms for magnetism are still debated.