Nanometer-scale spatial inhomogeneities of the chemical and electronic properties of an ion implanted Mn–Ge alloy

Abstract

Electron energy loss spectroscopy maps using a transmission electron microscope were used to investigate with nanometer spatial resolution the Mn distribution of a Mn x Ge 1− x ion implanted alloy ( x ≃ 4%). Mn is fully diluted in the Ge matrix in a subsurface implanted layer, showing concentration inhomogeneities at the nm scale. In the deep implanted layers the presence of Mn rich clusters—either amorphous or in the Mn 5Ge 3 phase—is directly evidenced. Scanning Tunneling Microscopy/Spectroscopy directly shows that the Mn 5Ge 3 clusters are metallic, while those smaller and amorphous are semiconducting with 0.45 ± 0.05 eV band gap. The Ge matrix with Mn dilution is semiconducting with 0.60 ± 0.05 eV gap. Electronic structure results are compared with ab-initio calculations.