Valence state manipulation of single Fe impurities in GaAs by STM

TL;DR

This paper demonstrates how scanning tunneling microscopy can manipulate and observe the valence and spin states of individual Fe impurities in GaAs, revealing charge state-dependent electronic contrast and state transitions.

Contribution

It introduces a method to control the valence and spin states of single Fe impurities in GaAs using STM tip voltage, a novel approach for impurity state manipulation.

Findings

Fe charge state affects local electronic contrast

Tip voltage can induce Fe valence and spin state transitions

Fe impurities produce anisotropic features in STM images

Abstract

The incorporation of Fe in GaAs was studied by cross-sectional scanning tunneling microscopy (X-STM). The observed local electronic contrast of a single Fe atom is found to depend strongly on its charge state. We demonstrate that an applied tip voltage can be used to manipulate the valence and spin state of single Fe impurities in GaAs. In particular we can induce a transition from the Fe{3+)- 3d5 - isoelectronic state to the Fe{2+} - 3d6 - ionized acceptor state with an associated change of the spin moment. Fe atoms sometimes produce dark anisotropic features in topographic maps, which is consistent with an interference between different tunneling paths.