Multiple proton diffusion and film densification in atomic layer deposition modeled by density functional theory

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dc.contributor.author Shirazi, Mahdi
dc.contributor.author Elliott, Simon D.
dc.date.accessioned 2016-03-08T17:27:26Z
dc.date.available 2016-03-08T17:27:26Z
dc.date.issued 2013-02-28
dc.identifier.citation SHIRAZI, M. & ELLIOTT, S. D. 2013. Multiple Proton Diffusion and Film Densification in Atomic Layer Deposition Modeled by Density Functional Theory. Chemistry of Materials, 25, 878-889. http://dx.doi.org/10.1021/cm303630e en
dc.identifier.volume 25 en
dc.identifier.issued 6 en
dc.identifier.startpage 878 en
dc.identifier.endpage 889 en
dc.identifier.issn 0897-4756
dc.identifier.uri http://hdl.handle.net/10468/2422
dc.identifier.doi 10.1021/cm303630e
dc.description.abstract To investigate the atomic layer deposition (ALD) reactions for growth of HfO2 from Hf(NMe2)4 (TDMAHf) andH2O, a density functional theory (DFT) slab model was employed. We inspected all energy steps, from the early stage of adsorption of each ALD precursor to the densification of multiple atoms into bulk-like HfO2 layers. The activation energy calculations show that repeated proton diffusion from the surface to amide ligands and rotation of the protonated amine is more energetically accessible than the simple elimination of the amine in the initial stage. We therefore propose that multiple protons diffuse to the amide ligands of the Hf precursor before desorption of protonated ligands takes place. Loss of a proton from surface oxygen frees it up for bonding to Hf of the precursor. Protonation of ligands, and especially desorption of ligands, frees up Hf for bonding to surface oxygen. These effects are termed “densification”, as they bring Hf−O packing closer to the bulk scenario. Densification is associated with substantial release of energy. During the metal pulse, saturation of the surface by remaining fragments HfX causes adsorption of further metal precursor to stop. The presence of these fragments prevents further chemisorption of HfX4, since this requires the creation of a strong dative bond between Hf and O. Next, during the H2O pulse, Hf exchanges its remaining ligands with OH groups. The exchange occurs due to the decomposition of adsorbed H2O molecules in clusters of HfX. Decomposition of H2O when adsorbed onto a (Hf(NMe2))x (x ≥ 2) cluster (e.g., dimers) also increases the coordination of Hf and O. Simultaneously, low-coordinated oxygen atoms appear at the surface, which are reactive sites for the next metal pulse. With saturation of the surface by OH groups, H2O molecules begin to appear. This detailed description of ALD chemistry allows us to make qualitative predictions about how the process depends on temperature. The data can also be inputted into kinetic simulations for a quantitative view of the complex film growth process. en
dc.description.sponsorship Science Foundation Ireland (SFI strategic research cluster “Functional Oxides and Related Materials for Electronics” (FORME)); Higher Education Authority (SFI/HEA Irish Centre for High-End Computing (ICHEC)) en
dc.format.mimetype application/pdf en
dc.language.iso en en
dc.publisher American Chemical Society en
dc.rights © 2013 American Chemical Society. This document is the Accepted Manuscript version of a Published Work that appeared in final form in Chemistry of Materials, copyright © American Chemical Society after peer review and technical editing by the publisher. To access the final edited and published work see http://dx.doi.org/10.1021/cm303630e en
dc.subject DFT en
dc.subject Density functional theory en
dc.subject ALD en
dc.subject Atomic layer deposition en
dc.subject KMC en
dc.subject Kinetic Monte Carlo en
dc.subject Metal oxide en
dc.subject Metal alkylamide precursor en
dc.subject Multiple proton diffusion en
dc.subject Densification en
dc.subject Activation energy en
dc.subject Dissociation en
dc.subject Adsorption en
dc.title Multiple proton diffusion and film densification in atomic layer deposition modeled by density functional theory en
dc.type Article (peer-reviewed) en
dc.internal.authorcontactother Simon Elliott, Tyndall Theory Modelling & Design Centre, University College Cork, Cork, Ireland. +353-21-490-3000 Email: simon.elliott@tyndall.ie en
dc.internal.availability Full text available en
dc.date.updated 2015-04-13T16:00:02Z
dc.description.version Accepted Version en
dc.internal.rssid 283617558
dc.contributor.funder Higher Education Authority en
dc.contributor.funder Science Foundation Ireland en
dc.description.status Peer reviewed en
dc.identifier.journaltitle Chemistry of Materials en
dc.internal.copyrightchecked Yes embargo period is over. !!CORA!! AV+12 month embargo+set statement. en
dc.internal.licenseacceptance Yes en
dc.internal.IRISemailaddress simon.elliott@tyndall.ie en


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