Structural-relaxation-induced bond length and bond angle changes in amorphized Ge

Low-temperature structural relaxation in amorphized Ge has been characterized by extended x-ray-absorption fine-structure spectroscopy and Raman spectroscopy. A relaxation-temperature-dependent decrease in the mean value and asymmetry of the interatomic distance distribution has been shown to accompany the well-documented reduction in bond angle distribution. While the initial, as-implanted state of amorphous Ge was ion-dose dependent, relaxation at 200 �C yielded a common ion-dose-independent interatomic distance distribution. The heat release upon structural relaxation due to reductions in both bond length and bond angle distortion was calculated separately and the former exhibited an ion-dose dependence. The results provide compelling support for the defect annihilation model of structural relaxation and imply that the heat release upon structural relaxation should be implant-condition dependent.