Structural relaxation in ion-damaged amorphous germanium

X-ray and optical studies of ion-damaged amorphous germanium reveal a structural relaxation produced by low-temperature (200 ^∘{}C) annealing. This relaxation appears to be qualitatively different from that observed previously at higher annealing temperatures (250--500 ^∘{}C). Extended x-ray-absorption fine-structure measurements, made in the total-electron-yield mode with a sampling depth of 600--800 {}, indicate a sharpening of the first shell in the radial distribution, but no change in the first-shell distance or coordination number. No higher shells in the radial distribution are observed, before or after annealing, indicating that these shells remain highly disordered. Infrared-reflection and Raman-scattering measurements confirm that a relaxation takes place and that there is no nucleation of microcrystals in the implanted layer within the detection limit of 1.5% volume fraction. In contrast to previous studies, the present results exhibit no evidence of a reduction in bond-angle disorder.