A transmission electron microscopy study of the interaction between defects in amorphous silicon and a moving crystalline/amorphous interface

Gandy, AS 2008, A transmission electron microscopy study of the interaction between defects in amorphous silicon and a moving crystalline/amorphous interface , PhD thesis, University of Salford, UK/Universite de Poitiers, France.

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Abstract

Transmission electron microscopy (TEM) has been used to investigate the damage produced following high temperature (350°C) Xe implantation into (100) Si at fluence (>lx!0 16 Xe ions/cm 2 ) and energy (250keV) which produce a buried amorphous layer; and the defect structures produced following thermal anneals of 400°C, 600°C or 800°C for 30 minutes. Analysis of these samples yielded results which suggested that the Xe gas contained within the amorphous layers was swept by the amorphous/crystalline interfaces during solid phase epitaxial re-crystallisation (SPEG) into large bubbles elongated along a direction perpendicular to the interfaces. In order to further investigate this sweeping effect, buried amorphous layers were produced in Si by implanting Li at liquid nitrogen temperature and post implanting the layers with IxlO 16 He ions/cm 2 . Contrary to the spherical bubbles produced under similar conditions in crystalline Si, irregular shaped bubbles were formed in the amorphous layer. Results from in-situ TEM studies showed that these bubbles are mobile at temperatures lower than expected in crystalline Si. Thus, upon reaching the moving interfaces between amorphous and crystalline Si, the bubbles are forced back into the amorphous material which ultimately results in coalescence of the gas into larger bubbles once the two interfaces combine. In addition, microtwins have been shown to form in regions of the re-crystallising layer where there exists an excess of interstitial-type defects. This is contrary to previous microtwin nucleation models which suggested that microtwins are either formed on [111] planes or on bubbles.

Item Type: Thesis (PhD)
Contributors: Donnelly, S (Supervisor) and Beaufort, M-F (Supervisor)
Schools: Schools > School of Computing, Science and Engineering
Depositing User: Institutional Repository
Date Deposited: 17 Aug 2021 09:45
Last Modified: 27 Aug 2021 21:57
URI: http://usir.salford.ac.uk/id/eprint/61589

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