A first principles analysis of the effect of hydrogen concentration in hydrogenated amorphous silicon on the formation of strained Si-Si bonds and the optical and mobility gaps

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dc.contributor.author Legesse, Merid
dc.contributor.author Nolan, Michael
dc.contributor.author Fagas, Gíorgos
dc.date.accessioned 2016-07-21T14:49:33Z
dc.date.available 2016-07-21T14:49:33Z
dc.date.issued 2014-05-28
dc.identifier.citation Legesse, M., Nolan, M. and Fagas, G. (2014) 'A first principles analysis of the effect of hydrogen concentration in hydrogenated amorphous silicon on the formation of strained Si-Si bonds and the optical and mobility gaps', Journal of Applied Physics, 115, 203711. http://scitation.aip.org/content/aip/journal/jap/115/20/10.1063/1.4880395 en
dc.identifier.volume 115 en
dc.identifier.startpage 203711 (1) en
dc.identifier.endpage 203711 (10) en
dc.identifier.issn 0021-8979
dc.identifier.issn 1089-7550
dc.identifier.uri http://hdl.handle.net/10468/2917
dc.identifier.doi 10.1063/1.4880395
dc.description.abstract In this paper, we use a model of hydrogenated amorphous silicon generated from molecular dynamics with density functional theory calculations to examine how the atomic geometry and the optical and mobility gaps are influenced by mild hydrogen oversaturation. The optical and mobility gaps show a volcano curve as the hydrogen content varies from undersaturation to mild oversaturation, with largest gaps obtained at the saturation hydrogen concentration. At the same time, mid-gap states associated with dangling bonds and strained Si-Si bonds disappear at saturation but reappear at mild oversaturation, which is consistent with the evolution of optical gap. The distribution of Si-Si bond distances provides the key to the change in electronic properties. In the undersaturation regime, the new electronic states in the gap arise from the presence of dangling bonds and strained Si-Si bonds, which are longer than the equilibrium Si-Si distance. Increasing hydrogen concentration up to saturation reduces the strained bonds and removes dangling bonds. In the case of mild oversaturation, the mid-gap states arise exclusively from an increase in the density of strained Si-Si bonds. Analysis of our structure shows that the extra hydrogen atoms form a bridge between neighbouring silicon atoms, thus increasing the Si-Si distance and increasing disorder in the sample. en
dc.description.sponsorship European Commission (7th Framework ICT-FET-Proactive program, Project: SiNAPS (Contract No 257856)); Science Foundation Ireland (SFI Starting Investigator Research Grant Program, project “EMOIN” grant number SFI 09/SIRG/I1620) en
dc.format.mimetype application/pdf en
dc.language.iso en en
dc.publisher AIP Publishing en
dc.rights © 2014 AIP Publishing LLC. This article may be downloaded for personal use only. Any other use requires prior permission of the author and AIP Publishing. The following article appeared in M. Legesse et al., J. Appl. Phys. 115, 203711 (2014) and may be found at http://dx.doi.org/10.1063/1.4880395 en
dc.subject Amorphous silicon en
dc.subject Atoms en
dc.subject Chemical bonds en
dc.subject Crystal atomic structure en
dc.subject Dangling bonds en
dc.subject Electronic properties en
dc.subject Hydrogen en
dc.subject Hydrogenation en
dc.subject Molecular dynamics en
dc.subject Undersaturation en
dc.subject Dangling bonds en
dc.subject Amorphous semiconductors en
dc.subject Optical saturation en
dc.subject Carrier mobility en
dc.subject Bond formation en
dc.title A first principles analysis of the effect of hydrogen concentration in hydrogenated amorphous silicon on the formation of strained Si-Si bonds and the optical and mobility gaps en
dc.type Article (peer-reviewed) en
dc.internal.authorcontactother Michael Nolan, Tyndall Theory Modelling & Design Centre, University College Cork, Cork, Ireland. +353-21-490-3000 Email: michael.nolan@tyndall.ie en
dc.internal.availability Full text available en
dc.date.updated 2014-09-04T11:10:46Z
dc.description.version Accepted Version en
dc.internal.rssid 269698985
dc.contributor.funder Science Foundation Ireland en
dc.contributor.funder European Commission en
dc.description.status Peer reviewed en
dc.identifier.journaltitle Journal of Applied Physics en
dc.internal.copyrightchecked No. !!CORA!! en
dc.internal.licenseacceptance Yes en
dc.internal.IRISemailaddress michael.nolan@tyndall.ie en
dc.identifier.articleid 203711


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