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Experiments on thermal relaxation of copper films for nano-calorimetry

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dc.contributor Aalto-yliopisto fi
dc.contributor Aalto University en
dc.contributor.advisor Saira, Olli-Pentti, Dr., Brookhaven National Laboratory, USA
dc.contributor.author Wang, Libin
dc.date.accessioned 2020-01-08T10:01:11Z
dc.date.available 2020-01-08T10:01:11Z
dc.date.issued 2020
dc.identifier.isbn 978-952-60-8906-5 (electronic)
dc.identifier.isbn 978-952-60-8905-8 (printed)
dc.identifier.issn 1799-4942 (electronic)
dc.identifier.issn 1799-4934 (printed)
dc.identifier.issn 1799-4934 (ISSN-L)
dc.identifier.uri https://aaltodoc.aalto.fi/handle/123456789/42350
dc.description.abstract Hot-electron calorimeter is a device used to detect a small package of energy utilizing thermal effect. For detection, the incoming energy is converted to temperature changes by the absorber of the calorimeter and then it is detected by a thermometer. Normal metal is one of the candidates to function as the absorber of hot-electron calorimeter due to the decoupling of electrons from its phonons at low temperatures, which provides the natural thermal isolation for electrons in the normal metal. To improve the performance of a normal-metal based calorimeter, one needs to understand the thermal relaxation mechanism in the device. In this dissertation, we experimentally investigate thermal relaxation in evaporated copper films at sub-kelvin temperatures. We characterize the thermal transport properties of the copper film in both steady-state and dynamic regime.  First, we give a short introduction to the nano-calorimeter and theoretically describe the relevant thermal properties explored in the dissertation. We describe the working principle of proximity Josephson junction thermometer used in the experiments to measure the electron temperature of copper films.  Next, we show the steady-state measurement results where then thermal conductance between film electrons and the environment is measured. Electron-phonon and thermal boundary conductance limit to thermal relaxation are identified in the experiments. We report the crossover of the thermal relaxation mechanism as changing film thickness and temperature. The impact of reduced phonon dimensionality on thermal conductance is discussed.  Finally, we show the dynamic thermal relaxation of copper films. In contrary to what is expected, we find that the process shows several relaxation times for copper films. Experiments are explained with a thermal model considering an additional thermal reservoir coupled to the film electrons. One possible origin of the thermal reservoir is the electrically isolated grains in the film with a different texture, and the electron-phonon coupling strength varies for grains with different orientations. en
dc.format.extent 71 + app. 46
dc.format.mimetype application/pdf en
dc.language.iso en en
dc.publisher Aalto University en
dc.publisher Aalto-yliopisto fi
dc.relation.ispartofseries Aalto University publication series DOCTORAL DISSERTATIONS en
dc.relation.ispartofseries 4/2020
dc.relation.haspart [Publication 1]: L. B. Wang, O.-P. Saira, and J. P. Pekola. Fast thermometry with aproximity Josephson junction. Appl. Phys. Lett., Volume 112, Issue 1, 013105 (5 pages), January 2018. DOI: 10.1063/1.5010236
dc.relation.haspart [Publication 2]: L.B. Wang, O.-P. Saira, D. S. Golubev, and J. P. Pekola. Crossover between Electron-Phonon and Boundary-Resistance Limits to Thermal Relaxation in Copper Films. Phys. Rev. Applied, Volume 12, Issue 2, 024051 (6 pages), August 2019. DOI: 10.1103/PhysRevApplied.12.024051
dc.relation.haspart [Publication 3]: O.-P. Saira, M. H. Matheny, L. B. Wang, J. P. Pekola, and M. Roukes. Modification of electron-phonon coupling by micromachining and suspension. Submitted to J. Appl. Phys., October 2109.
dc.relation.haspart [Publication 4]: L. B. Wang, D. S. Golubev, Y. Galperin, and J. P. Pekola. Dynamic thermal relaxation in copper films. Submitted to Phys. Rev. Lett., October 2019.
dc.subject.other Physics en
dc.title Experiments on thermal relaxation of copper films for nano-calorimetry en
dc.type G5 Artikkeliväitöskirja fi
dc.contributor.school Perustieteiden korkeakoulu fi
dc.contributor.school School of Science en
dc.contributor.department Teknillisen fysiikan laitos fi
dc.contributor.department Department of Applied Physics en
dc.subject.keyword thermal relaxation en
dc.subject.keyword thermal conductance en
dc.subject.keyword calorimeter en
dc.subject.keyword proximity Josephson junction en
dc.identifier.urn URN:ISBN:978-952-60-8906-5
dc.type.dcmitype text en
dc.type.ontasot Doctoral dissertation (article-based) en
dc.type.ontasot Väitöskirja (artikkeli) fi
dc.contributor.supervisor Pekola, Jukka P., Aalto University, Department of Applied Physics, Finland
dc.opn Il'ichev, Evgeni, Prof., Institute of Photonic Technology, Germany
dc.contributor.lab PICO group en
dc.rev Beckmann, Detlef, Prof., Karlsruhe Institute of Technology, Germany
dc.rev Bourgeois, Olivier, Dr., Institut Néel, France
dc.date.defence 2020-01-21
local.aalto.acrisexportstatus checked 2020-03-14_1256
local.aalto.infra OtaNano
local.aalto.infra OtaNano - Aalto Nanofab / Micronova
local.aalto.infra OtaNano - Low Temperature Laboratory
local.aalto.formfolder 2020_01_08_klo_10_47
local.aalto.archive yes

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