Transition metal impurities on the bond-centered site in germanium

Phys Rev Lett. 2009 Feb 13;102(6):065502. doi: 10.1103/PhysRevLett.102.065502. Epub 2009 Feb 10.

Abstract

We report on the lattice location of ion implanted Fe, Cu, and Ag impurities in germanium from a combined approach of emission channeling experiments and ab initio total energy calculations. Following common expectation, a fraction of these transition metals (TMs) was found on the substitutional Ge position. Less expected is the observation of a second fraction on the sixfold coordinated bond-centered site. Ab initio calculated heats of formation suggest this is the result of the trapping of a vacancy by a substitutional TM impurity, spontaneously forming an impurity-vacancy complex in the split-vacancy configuration. We also present an approach to displace the TM impurities from the electrically active substitutional site to the bond-centered site.