Journal article

Boson peak in ultrathin alumina layers investigated with neutron spectroscopy

DL Cortie, MJ Cyster, TA Ablott, C Richardson, JS Smith, GN Iles, XL Wang, DRG Mitchell, RA Mole, NR de Souza, DH Yu, JH Cole

PHYSICAL REVIEW RESEARCH | AMER PHYSICAL SOC | Published : 2020

Abstract

Bulk 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 ..

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University of Melbourne Researchers

Grants

Awarded by Australian Research Council (ARC)


Awarded by ARC Centre for Excellence in Future Low-Energy Electronics


Awarded by Centre for Excellence in Exciton Science


Awarded by ARC LIEF grant


Funding Acknowledgements

J.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).