Implantation-induced disorder in amorphous Ge: Production and relaxation

Extended X-ray absorption fine structure and Raman spectroscopy have been u tilised to measure implantation-induced micro-structural modifications in a morphous Ge including increases in bond length, broadening of the bondangle distribution, and non-Gaussian static disorder as functions of ion dose. T he resulting evolution of the interatomic distance distribution, over an io n dose range extending two orders of magnitude beyond that required for amo rphisation, demonstrates the influence of implant conditions on amorphous p hase structure. Results are attributed to increased fractions of three- and fivefold coordinated atoms as a means of accommodating implantation-induce d point defects in the amorphous phase. In contrast, a common, ion-dose-ind ependent structure is apparent following low-temperature, thermally-induced relaxation as consistent with the annealing of point defects in the amorph ous phase. Structural relaxation is manifested by reductions in both bond-l ength and bond-angle distortion and the relaxation enthalpy for each compon ent has been calculated separately. (C) 2001 Elsevier Science B,V. All righ ts reserved.