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Extended point defects in crystalline materials: Ge and Si

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.

Publication metadata

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


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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Funder referenceFunder name
258547European Union