Boson peak in ultrathin alumina layers investigated with neutron spectroscopy

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dc.contributor.authorCortie, DLen_AU
dc.contributor.authorCyster, MJen_AU
dc.contributor.authorAblott, TAen_AU
dc.contributor.authorRichardson, Cen_AU
dc.contributor.authorSmith, JSen_AU
dc.contributor.authorIles, GNen_AU
dc.contributor.authorWang, XLen_AU
dc.contributor.authorMitchell, DRGen_AU
dc.contributor.authorMole, RAen_AU
dc.contributor.authorde Souza, NRen_AU
dc.contributor.authorYu, DHen_AU
dc.contributor.authorCole, JHen_AU
dc.date.accessioned2023-11-08T04:40:08Zen_AU
dc.date.available2023-11-08T04:40:08Zen_AU
dc.date.issued2020-06-11en_AU
dc.date.statistics2023-10-26en_AU
dc.description.abstractBulk glasses exhibit extra vibrational modes at low energies, collectively known as the boson peak. The vibrational dynamics in nanoscale alumina glasses have an impact on the performance of qubits and other superconducting devices; however, the frequency of the boson peak has not been previously measured. Here we report neutron spectroscopy experiments on Al/Al2O3 nanoparticles consisting of spherical metallic cores with a radii from 20 to 1000 nm surrounded by a 3.5-nm-thick alumina glass. A low-energy peak is observed at ωBP = 2.8 ± 0.6 meV for highly oxidized particles, indicating an excess in the density of states. The intensity of the peak scales inversely with particle size and oxide fraction, indicating a surface origin, and is redshifted by 3 meV with respect to the van Hove singularity of γ -phase Al2O3 nanocrystals. Molecular-dynamics simulations of α-Al2O3, γ -Al2O3 and α-Al2O3 show that the observed boson peak is a signature of the ultrathin glass surface and the characteristic frequency is reduced compared to the peak in the bulk glass. © 2020 The Authors. Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license.en_AU
dc.description.sponsorshipJ.H.C. and D.L.C. acknowledge the support of the Australian Research Council (ARC) via Grants No. DP140100375 and No. DE180100314. This work was partly supported by the ARC Centre for Excellence in Future Low-Energy Electronics (Grant No. CE170100039) and the Centre for Excellence in Exciton Science (Grant No. CE170100026). High performance computing was performed on the National Computational Infrastructure. This research used the JEOL JEM-ARM200F funded by an ARC LIEF grant (Grant No. LE120100104). Neutron spectroscopy was performed at the Australian Centre for Neutron Scattering (P7437).en_AU
dc.identifier.articlenumber023320en_AU
dc.identifier.citationCortie, D. L., Cyster, M. J., Ablott, T. A., Richardson, C., Smith, J. S., Iles, G. N., .Wang, X. L., Mitchell, D. R. G., Mole, R. A., de Souza, N. R, Yu, D. H., & Cole, J. H. (2020). Boson peak in ultrathin alumina layers investigated with neutron spectroscopy. Physical Review Research, 2(2), 023320. doi:10.1103/PhysRevResearch.2.023320en_AU
dc.identifier.issn2643-1564en_AU
dc.identifier.issue2en_AU
dc.identifier.journaltitlePhysical Review Researchen_AU
dc.identifier.urihttps://apo.ansto.gov.au/handle/10238/15183en_AU
dc.identifier.volume2en_AU
dc.language.isoenen_AU
dc.publisherAmerican Physical Societyen_AU
dc.relation.urihttps://doi.org/10.1103/PhysRevResearch.2.023320en_AU
dc.subjectBosonsen_AU
dc.subjectLayersen_AU
dc.subjectNeutron spectroscopyen_AU
dc.subjectGlassen_AU
dc.subjectVibrational statesen_AU
dc.subjectQubitsen_AU
dc.subjectNanoparticlesen_AU
dc.subjectMolecular dynamics methoden_AU
dc.titleBoson peak in ultrathin alumina layers investigated with neutron spectroscopyen_AU
dc.typeJournal Articleen_AU
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