Structural characterization of pressure-induced amorphous silicon

B. Haberl*, A. C.Y. Liu, J. E. Bradby, S. Ruffell, J. S. Williams, P. Munroe

*Corresponding author for this work

    Research output: Contribution to journalArticlepeer-review

    33 Citations (Scopus)

    Abstract

    We investigate the structure and mechanical properties of pressure-induced (PI) amorphous silicon (a-Si) and compare this to the more extensively characterized case of a-Si created by ion implantation. To study the effect of thermal history we also examine the structure of both PI and ion-implanted a-Si after a low-temperature "relaxation" anneal (450°C). Indentation testing suggests that structural changes are induced by thermal annealing. As-prepared forms of a-Si deform via plastic flow, while relaxed forms of a-Si transform to high-pressure crystalline phases. These structural changes are confirmed by more explicit measurements. Raman microspectroscopy shows that the short-range order as expressed by the average bond-angle distortion of the as-prepared amorphous phases is the same and reduced by the same amount following the low-temperature anneal. Fluctuation electron microscopy demonstrates that the as-prepared PI a-Si displays a much lower variance of the diffracted intensity, a feature directly correlated with the medium-range order, than the as-prepared ion-implanted a-Si. However, relaxation brings this variance of the two networks to the same intermediate level. The mechanical tests and structural probes indicate that annealing the amorphous silicon network can bring it to a common state with the same structure and properties regardless of the initial state. This final state might be the closest attainable to the continuous random network model.

    Original languageEnglish
    Article number155209
    JournalPhysical Review B - Condensed Matter and Materials Physics
    Volume79
    Issue number15
    DOIs
    Publication statusPublished - 1 Apr 2009

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