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[{"key": "dc.contributor.advisor", "value": "Maasilta, Ilari", "language": "", "element": "contributor", "qualifier": "advisor", "schema": "dc"}, {"key": "dc.contributor.author", "value": "Korkiam\u00e4ki, Tatu", "language": "", "element": "contributor", "qualifier": "author", "schema": "dc"}, {"key": "dc.date.accessioned", "value": "2020-12-03T08:43:09Z", "language": null, "element": "date", "qualifier": "accessioned", "schema": "dc"}, {"key": "dc.date.available", "value": "2020-12-03T08:43:09Z", "language": null, "element": "date", "qualifier": "available", "schema": "dc"}, {"key": "dc.date.issued", "value": "2020", "language": "", "element": "date", "qualifier": "issued", "schema": "dc"}, {"key": "dc.identifier.uri", "value": "https://jyx.jyu.fi/handle/123456789/72941", "language": null, "element": "identifier", "qualifier": "uri", "schema": "dc"}, {"key": "dc.description.abstract", "value": "Fononikide on keinotekoinen periodinen rakenne yhdess\u00e4, kahdessa tai kolmessa\nulottuvuudessa, joka vaikuttaa fononien eli elastisten aaltojen kvanttien etenemiseen.\nKoska l\u00e4mm\u00f6n johtuminen eristeiss\u00e4 ja puolijohteissa tapahtuu p\u00e4\u00e4asiassa fononien\nv\u00e4lityksell\u00e4, voidaan fononikiteill\u00e4 vaikuttaa l\u00e4mm\u00f6n kulkeutumiseen kyseisiss\u00e4\nmateriaaleissa. Fononikiteiden toimintamekanismit voidaan karkeasti jakaa kahteen\neri kategoriaan: ep\u00e4koherenttiin, jossa hiukkasmainen diffusiivinen sironta hallitsee,\nja koherenttiin, jossa fononit etenev\u00e4t aaltomaisesti. Verrattuna reik\u00e4rakenteisiin\nperustuviin kiteisiin, l\u00e4mm\u00f6njohtumiseen vaikuttavien fononikiteiden joukossa huomattavasti\nv\u00e4hemm\u00e4n tutkittuja 2D-kiteit\u00e4 ovat niin kutsutut pilaripohjaiset fononikiteet,\njoissa hila muodostuu periodisesti j\u00e4rjestyneist\u00e4 pilareista ohuella kalvolla.\nN\u00e4iden fononikiteiden spektri voi sis\u00e4lt\u00e4\u00e4 niin kutsuttuja lokaaleja resonansseja,\njotka est\u00e4v\u00e4t l\u00e4mm\u00f6n kulkeutumisen.\nT\u00e4ss\u00e4 pro gradu -tutkielmassa valmistettiin kaksi pilaripohjaista fononikidett\u00e4 eri\nhilavakiolla, joiden l\u00e4mm\u00f6njohtavuudet mitattiin. Pilareiden materiaali oli alumiini,\nja niiden korkeus oli 300 nm, t\u00e4ytt\u00f6suhde oli 0.65, hilavakiot olivat 5 um ja 1 um, ja\nne olivat 300 nm paksun piinitridikalvon pinnalla. Mittaukset suoritettiin suprajohtaviin\nliitoksiin perustuvalla l\u00e4mmitin-l\u00e4mp\u00f6mittari-laitteella, joka valmistettiin\nn\u00e4ytteelle. Mittaukset tehtiin alle Kelvinin l\u00e4mp\u00f6tilassa, joka saavutettiin 3He/4Helaimennusj\u00e4\u00e4hdyttimell\u00e4.\nTuloksina saatiin 85 %:n l\u00e4mm\u00f6njohtavuuden aleneminen\nverrattuna puhtaaseen kalvoon, joka kuitenkin vaikuttaisi olevan per\u00e4isin ep\u00e4koherentista\nsironnasta. Mahdollisia syit\u00e4 koherenssin katoamiselle ovat pilareiden pinnan\nep\u00e4tasaisuus, pilareiden ja kalvon v\u00e4linen rajapinta sek\u00e4 pilareiden sis\u00e4iset raerajat.", "language": "fi", "element": "description", "qualifier": "abstract", "schema": "dc"}, {"key": "dc.description.abstract", "value": "A phononic crystal (PnC) is an artificial periodic structure in one, two or three\ndimensions that affects the propagation of phonons, the quanta of elastic waves. As\nheat is mostly carried by phonons in insulators and semiconductors, PnC can be\nutilised in controlling thermal transport in such materials. The mechanisms how\nPnCs can work can be generally divided into two categories: one where incoherent,\ndiffusive particle-like scattering dominates, and another where coherent wave-like\nscattering is operational. Compared to hole-based PnCs, much less studied 2D\ncrystals in thermal conductance manipulation are the pillar-based PnCs, where the\nlattice is formed by a periodic array of pillars on a thin membrane. For such PnCs,\nthe phonon spectrum can also include localised resonances which cannot carry heat.\nIn this thesis we have fabricated and measured the thermal conductance of two\npillar-based PnC with a different lattice constant, where aluminium pillars with\na height of 300 nm, a 0.65 filling factor and lattice constants of 5 um and 1 um\nwere deposited on a 300 nm thick silicon nitride film. The measurements were\nconducted at sub-Kelvin temperatures with a superconducting junction-based heaterthermometer\nsetup fabricated onto the sample. Low temperatures were achieved\nvia a 3He/4He dilution refrigerator. The results showed up to an 85 % reduction\nin thermal conductance compared to an unaltered film. Initially, it appears that\nthe mechanism responsible for the reduction was incoherent scattering. Possible\ncauses for the breakdown of the coherence include the pillar surface roughness, the\npillar-film-interface, or grain boundaries within the pillars.", "language": "en", "element": "description", "qualifier": "abstract", "schema": "dc"}, {"key": "dc.description.provenance", "value": "Submitted by Paivi Vuorio (paelvuor@jyu.fi) on 2020-12-03T08:43:09Z\nNo. of bitstreams: 0", "language": "en", "element": "description", "qualifier": "provenance", "schema": "dc"}, {"key": "dc.description.provenance", "value": "Made available in DSpace on 2020-12-03T08:43:09Z (GMT). No. of bitstreams: 0\n Previous issue date: 2020", "language": "en", "element": "description", "qualifier": "provenance", "schema": "dc"}, {"key": "dc.format.extent", "value": "99", "language": "", "element": "format", "qualifier": "extent", "schema": "dc"}, {"key": "dc.format.mimetype", "value": "application/pdf", "language": null, "element": "format", "qualifier": "mimetype", "schema": "dc"}, {"key": "dc.language.iso", "value": "eng", "language": null, "element": "language", "qualifier": "iso", "schema": "dc"}, {"key": "dc.rights", "value": "In Copyright", "language": "en", "element": "rights", "qualifier": null, "schema": "dc"}, {"key": "dc.subject.other", "value": "phononic crystal", "language": "", "element": "subject", "qualifier": "other", "schema": "dc"}, {"key": "dc.title", "value": "Thermal conductance of pillar-based phononic crystals at sub-Kelvin temperatures", "language": "", "element": "title", "qualifier": null, "schema": "dc"}, {"key": "dc.type", "value": "master thesis", "language": null, "element": "type", "qualifier": null, "schema": "dc"}, {"key": "dc.identifier.urn", "value": "URN:NBN:fi:jyu-202012036898", "language": "", "element": "identifier", "qualifier": "urn", "schema": "dc"}, {"key": "dc.type.ontasot", "value": "Pro gradu -tutkielma", "language": "fi", "element": "type", "qualifier": "ontasot", "schema": "dc"}, {"key": "dc.type.ontasot", "value": "Master\u2019s thesis", "language": "en", "element": "type", "qualifier": "ontasot", "schema": "dc"}, {"key": "dc.contributor.faculty", "value": "Matemaattis-luonnontieteellinen tiedekunta", "language": "fi", "element": "contributor", "qualifier": "faculty", "schema": "dc"}, {"key": "dc.contributor.faculty", "value": "Faculty of Sciences", "language": "en", "element": "contributor", "qualifier": "faculty", "schema": "dc"}, {"key": "dc.contributor.department", "value": "Fysiikan laitos", "language": "fi", "element": "contributor", "qualifier": "department", "schema": "dc"}, {"key": "dc.contributor.department", "value": "Department of Physics", "language": "en", "element": "contributor", "qualifier": "department", "schema": "dc"}, {"key": "dc.contributor.organization", "value": "Jyv\u00e4skyl\u00e4n yliopisto", "language": "fi", "element": "contributor", "qualifier": "organization", "schema": "dc"}, {"key": "dc.contributor.organization", "value": "University of Jyv\u00e4skyl\u00e4", "language": "en", "element": "contributor", "qualifier": "organization", "schema": "dc"}, {"key": "dc.subject.discipline", "value": "Fysiikka", "language": "fi", "element": "subject", "qualifier": "discipline", "schema": "dc"}, {"key": "dc.subject.discipline", "value": "Physics", "language": "en", "element": "subject", "qualifier": "discipline", "schema": "dc"}, {"key": "yvv.contractresearch.funding", "value": "0", "language": "", "element": "contractresearch", "qualifier": "funding", "schema": "yvv"}, {"key": "dc.type.coar", "value": "http://purl.org/coar/resource_type/c_bdcc", "language": null, "element": "type", "qualifier": "coar", "schema": "dc"}, {"key": "dc.rights.accesslevel", "value": "openAccess", "language": null, "element": "rights", "qualifier": "accesslevel", "schema": "dc"}, {"key": "dc.type.publication", "value": "masterThesis", "language": null, "element": "type", "qualifier": "publication", "schema": "dc"}, {"key": "dc.subject.oppiainekoodi", "value": "4021", "language": "", "element": "subject", "qualifier": "oppiainekoodi", "schema": "dc"}, {"key": "dc.subject.yso", "value": "koherenssi", "language": null, "element": "subject", "qualifier": "yso", "schema": "dc"}, {"key": "dc.subject.yso", "value": "l\u00e4mm\u00f6n johtuminen", "language": null, "element": "subject", "qualifier": "yso", "schema": "dc"}, {"key": "dc.subject.yso", "value": "fononit", "language": null, "element": "subject", "qualifier": "yso", "schema": "dc"}, {"key": "dc.subject.yso", "value": "pilarit", "language": null, "element": "subject", "qualifier": "yso", "schema": "dc"}, {"key": "dc.subject.yso", "value": "coherence", "language": null, "element": "subject", "qualifier": "yso", "schema": "dc"}, {"key": "dc.subject.yso", "value": "heat conduction", "language": null, "element": "subject", "qualifier": "yso", "schema": "dc"}, {"key": "dc.subject.yso", "value": "phonons", "language": null, "element": "subject", "qualifier": "yso", "schema": "dc"}, {"key": "dc.subject.yso", "value": "pillars", "language": null, "element": "subject", "qualifier": "yso", "schema": "dc"}, {"key": "dc.format.content", "value": "fulltext", "language": null, "element": "format", "qualifier": "content", "schema": "dc"}, {"key": "dc.rights.url", "value": "https://rightsstatements.org/page/InC/1.0/", "language": null, "element": "rights", "qualifier": "url", "schema": "dc"}, {"key": "dc.type.okm", "value": "G2", "language": null, "element": "type", "qualifier": "okm", "schema": "dc"}]
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