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Lookup NU author(s): Professor Nick Cowern, Dr Sergei Simdyankin, Dr Chihak Ahn, Dr Nick Bennett, Professor Jon Goss
B diffusion measurements are used to probe the basic nature of self-interstitial ‘point’ defects in Ge. We find two distinct self-interstitial forms – a simple one with low entropy and a complex one with entropy ~30 k at the migration saddle point. The latter dominates diffusion at high temperature. We propose that its structure is similar to that of an amorphous pocket – we name it a morph. Computational modelling suggests that morphs exist in both self-interstitial and vacancy-like forms, and are crucial for diffusion and defect dynamics in Ge, Si and probably many other crystalline solids.
Author(s): Cowern NEB, Simdyankin S, Ahn C, Bennett NS, Goss JP, Hartmann JM, Pakfar A, Hamm S, Valentin J, Napolitani E, De Salvador D, Bruno E, Mirabella S
Publication type: Article
Publication status: Published
Journal: Physical Review Letters
Year: 2013
Volume: 110
Issue: 15
Print publication date: 08/04/2013
Date deposited: 28/03/2013
ISSN (print): 0031-9007
ISSN (electronic): 1079-7114
Publisher: American Physical Society
URL: http://dx.doi.org/10.1103/PhysRevLett.110.155501
DOI: 10.1103/PhysRevLett.110.155501
Notes: The paper resolves a decades-long discussion over the nature of point defects - the entities which enable mass transport in crystals such as silicon, germanium, complex crystalline compounds, and even water ice. A novel form of 'delocalised' point defect, consisting of an amorphous-like pocket, is shown to dominate self-interstitial diffusion in germanium at high temperature. The concept is generalised to a very wide range of materials, and atomistic simulations in the diamond structure of silicon and germanium show the detailed structural types involved. This paper may significantly influence future developments in computational modelling of crystalline materials.
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