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

Electron energy loss spectroscopy maps using a transmission electron microscope were used to investigate with nanometer spatial resolution the Mn distribution of a MnxGe1−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 Mn5Ge3 phase—is directly evidenced. Scanning Tunneling Microscopy/Spectroscopy directly shows that the Mn5Ge3 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.