Role of Vacancy-Type Defects during Structural Relaxation of Amorphous Si

Abstract
Structural relaxation processes in amorphous Si (a-Si) have been investigated using Raman spectroscopy and positron lifetime measurements. Bond angle deviation Δθ and sizes of vacancy-type defects were estimated for ion-beam-induced a-Si (IBa-Si) and ECR plasma CVD a-Si (ECRa-Si). During 450° C annealing, Δθ decreased appreciably and only small vacancies with a size less than that of the divacancy were observed in IBa-Si, while in ECRa-Si large vacancy clusters were formed and Δθ was approximately constant indicating that relaxation processes are suppressed in ECRa-Si. These results suggest that large vacancy-type defects can stabilize amorphous structures.

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