Implantation-induced disorder in amorphous Ge: Production and relaxation

Extended X-ray absorption fine structure and Raman spectroscopy have been utilised to measure implantation-induced micro-structural modifications in amorphous Ge including increases in bond length, broadening of the bond-angle distribution, and non-Gaussian static disorder as functions of ion dose. The resulting evolution of the inter-atomic distance distribution, over an ion dose range extending two orders of magnitude beyond that required for amorphisation, demonstrates the influence of implant conditions on amorphous phase structure. Results are attributed to increased fractions of three- and fivefold coordinated atoms as a means of accommodating implantation-induced point defects in the amorphous phase. In contrast, a common, ion-dose-independent structure is apparent following low-temperature, thermally-induced relaxation as consistent with the annealing of point defects in the amorphous phase. Structural relaxation is manifested by reductions in both bond-length and bond-angle distortion and the relaxation enthalpy for each component has been calculated separately.