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[{"key": "dc.contributor.advisor", "value": "Maasilta, Ilari", "language": "", "element": "contributor", "qualifier": "advisor", "schema": "dc"}, {"key": "dc.contributor.author", "value": "Kirjanen, Emmi", "language": "", "element": "contributor", "qualifier": "author", "schema": "dc"}, {"key": "dc.date.accessioned", "value": "2018-12-20T11:17:42Z", "language": null, "element": "date", "qualifier": "accessioned", "schema": "dc"}, {"key": "dc.date.available", "value": "2018-12-20T11:17:42Z", "language": null, "element": "date", "qualifier": "available", "schema": "dc"}, {"key": "dc.date.issued", "value": "2018", "language": "", "element": "date", "qualifier": "issued", "schema": "dc"}, {"key": "dc.identifier.uri", "value": "https://jyx.jyu.fi/handle/123456789/60737", "language": null, "element": "identifier", "qualifier": "uri", "schema": "dc"}, {"key": "dc.description.abstract", "value": "T\u00e4ss\u00e4 ty\u00f6ss\u00e4 on tutkittu kolmiulotteisia periodisia nanorakenteita, tarkemmin sanottuna fononikiteit\u00e4. Fononikiteet voivat muokata kiteess\u00e4 liikkuvia v\u00e4r\u00e4htelyit\u00e4, eli \u00e4\u00e4nt\u00e4 ja l\u00e4mp\u00f6\u00e4, samaan tapaan kuin fotonikiteet vaikuttavat valoon. Riippuen kiteen rakenteesta ja materiaaleista, jotkin taajuudet voivat kulkeutua paremmin tai huonommin, tai jotkin niist\u00e4 voivat olla t\u00e4ysin kiellettyj\u00e4 kiteen sis\u00e4ll\u00e4. J\u00e4lkimm\u00e4ist\u00e4 tapausta kutsutaan energia-aukoksi, sill\u00e4 fononeilla ei voi olla kyseisi\u00e4 energioita. Fononikiteit\u00e4 voidaan soveltaa esimerkiksi hyv\u00e4n tai huonon l\u00e4mm\u00f6njohtavuuden saavuttamiseksi, tiettyjen v\u00e4r\u00e4htelytaajuuksien vahvistamiseksi tai poistamiseksi, tai v\u00e4r\u00e4htelyjen ohjaamiseksi.\n\nMatalissa l\u00e4mp\u00f6tiloissa l\u00e4mm\u00f6njohtumisen kontrolloinnin t\u00e4rkeys korostuu ja termisten fononien taajuusalue on pienempi verrattuna korkeampiin l\u00e4mp\u00f6tiloihin, joten t\u00e4ss\u00e4 ty\u00f6ss\u00e4 ollaankin keskitytty matalissa l\u00e4mp\u00f6tiloissa havaittaviin efekteihin. T\u00e4m\u00e4 asettaa n\u00e4ytteen periodin nano-mikrometrialueelle ja l\u00e4mm\u00f6njohtumiseen k\u00e4ytett\u00e4v\u00e4n mittasysteemin tulisi olla mataliin l\u00e4mp\u00f6tiloihin soveltuva. Mittauksissa nanovalmistetut tunneliliitokset toimisivat lokaalina l\u00e4mmittimen\u00e4 ja l\u00e4mp\u00f6mittarina, joita voitaisiin k\u00e4ytt\u00e4\u00e4 kiteen ominaisuuksien tutkimiseen. Tunneliliitoksien herkk\u00e4 l\u00e4mp\u00f6tilak\u00e4ytt\u00e4ytyminen on hyvin tunnettu ilmi\u00f6 ja niit\u00e4 ollaan k\u00e4ytetty paljon esimerkiksi kalvojen tutkimuksessa. Uutena haasteena kuitenkin on, miten kyseisten herkkien rakenteiden valmistaminen luonnistuu kolmiulotteisen pinnan p\u00e4\u00e4lle.\n\nKaksiulotteisten fononikiteiden osalta on jo tehty huomattavia edistysaskelia, joten t\u00e4ss\u00e4 ty\u00f6ss\u00e4 on keskitytty vain kolmiulotteisten kiteiden valmistamiseen valitulla menetelm\u00e4ll\u00e4. Valmistusprosessissa on yhdistetty useita aiemmin tutkittuja menetelmi\u00e4. Ensin kiteelle tehtiin negatiivisesta fotoresistist\u00e4 sen sijaintia ja kokoa rajoittava rakenne UV-litografian avulla puhdistetun piipalan p\u00e4\u00e4lle. Itse kide valmistettiin itsej\u00e4rjestyvyytt\u00e4 hy\u00f6dynt\u00e4en kolloidikiteytyksell\u00e4 polystyreenipalloista, joiden halkaisija oli satojen nanometrien luokkaa. Kiteytysprosessissa havaittiin, ett\u00e4 polystyreenipallot hakeutuvat mieluiten niille varattuihin kohtiin ja resistin pinta j\u00e4\u00e4 useimmiten hyvinkin puhtaaksi, mik\u00e4 mahdollistaa metalloinnin tekemisen n\u00e4ytteen p\u00e4\u00e4lle. Metallisten liitosten tekemist\u00e4 varten n\u00e4ytteen p\u00e4\u00e4lle levitettiin uusi, my\u00f6hemmin poistettava resistikerros, mihin valotettiin laser-litografialla haluttu kuvio. Kuvioidun resistin ja kahden kulman h\u00f6yrystyksen avulla pyrittiin valmistamaan pari SINIS tunneliliitoksia. Liitoksessa alumiini toimi suprajohteena (S) ja kupari normaalimetallina (N), ja h\u00f6yrystyksien v\u00e4liss\u00e4 alumiinin pintaan muodostettu alumiinioksidi toimi eristeen\u00e4 (I). H\u00f6yrystyksist\u00e4 havaittiin, ett\u00e4 johtimet onnistuivat suoraan kiteen p\u00e4\u00e4lle, mik\u00e4li ne olivat tarpeeksi leveit\u00e4 ja jos metallia h\u00f6yrystettiin tarpeeksi paksulti.\n\nMatalissa l\u00e4mp\u00f6tiloissa suoritetut mittaukset vahvistivat valmistetut metalloinnit tunneliliitoksiksi niiden tunnusomaisten virta-j\u00e4nnite-k\u00e4yrien perusteella. Liitokset olisivat siis soveltuvia k\u00e4ytett\u00e4viksi l\u00e4mp\u00f6tilan mittaamiseen. Ensimm\u00e4isiss\u00e4 mittauksissa havaittiin kuitenkin my\u00f6s poikkeuksellista k\u00e4ytt\u00e4ytymist\u00e4, mink\u00e4 l\u00e4hteit\u00e4 ei valitettavasti viel\u00e4 ymm\u00e4rret\u00e4. Efekti\u00e4 ei kuitenkaan saatu toistettua toisissa mittauksissa, mitk\u00e4 puolestaan noudattivat teoriaa huomattavan hyvin koko j\u00e4nnitealueella. L\u00e4mm\u00f6njohtumismittauksia ei valitettavasti ehditty viel\u00e4 tehd\u00e4, mutta kaikki v\u00e4lineet sit\u00e4 varten on nyt toteutettavissa. My\u00f6s mahdollisuuksia referenssin\u00e4ytteen valmistamiseksi on tutkittu.", "language": "fi", "element": "description", "qualifier": "abstract", "schema": "dc"}, {"key": "dc.description.abstract", "value": "In this work three-dimensional periodic nanostructures, phononic crystals to be more exact, have been studied. Phononic crystals are analogous to photonic crystals. They can modify lattice vibrations such as sound and heat in a similar manner like photonic crystals affect light. Depending on the structure and the materials some frequencies can travel faster or slower, and some frequency ranges can be completely blocked. Blocked frequency ranges are called energy gaps as vibrations are not allowed to have those energies. Phononic crystals have a wide range in applications such as thermal insulation or contact, or selecting or guiding specific frequencies.\n\nAt low temperatures, the importance of thermal management is even more essential compared to room temperature. In addition, the frequency range of thermal phonons is modified. Because of this, this work focused on effects that are present at low temperatures. This in turn restricts the phononic crystal sample period close to nano- and micrometer range, and in addition, the measurement system for thermal conduction should be suitable for low temperatures. As planned for the measurements, nanofabricated tunnel junctions could serve as a local thermometer and a heater. Tunnel junctions are highly sensitive to temperature and their theory is well known and thermometry applications are widely used. A new challenge in this work is how to fabricate such a delicate system on top of a rough crystal surface.\n\nThere has already been notable breakthroughs with two-dimensional phononic crystals. In turn, in this project the scope is three-dimensional phononic crystals with selected fabrication techniques. The techniques are a combination of multiple previously studied methods. First, a negative photoresist and UV-lithography are used to make a template structure which in turn is used to control the crystal size and position. The crystal itself was made by utilizing colloidal crystallization from sub-micron sized polystyrene spheres. It was noticed that crystals formed mostly in the patterned sites leaving the photoresist surface clean. This makes the following metal deposition steps easier, as misplaced spheres could hinder the process. For the tunnel junction fabrication, a new positive photoresist layer was deposited and then patterned with laser lithography. SINIS tunnel junctions were evaporated by using two-angle deposition. In the junction aluminum served as the superconductor (S), copper as the normal metal (N), and aluminum oxide between them as the insulator (I). The junction deposition was found to be successful even directly on top of the crystals when using wide and thick enough wiring.\n\nMeasurements that were carried out at low temperatures confirmed that the tunnel junction fabrication was successful, by the study of the characteristic current-voltage curves. The junctions would thus be suitable to be used as thermometers. In the first measurement, there was some nonideal behavior present. However, such effects were not repeated, and unfortunately, their cause is still not fully known. Nevertheless, the second measurement was in good agreement with theory in the whole voltage range. Thermal conduction measurements were unfortunately not yet carried out, but the advancements in this thesis should make them possible in the near future. Also, possibilities for a control sample have been investigated.", "language": "en", "element": "description", "qualifier": "abstract", "schema": "dc"}, {"key": "dc.description.provenance", "value": "Submitted by Paivi Vuorio (paelvuor@jyu.fi) on 2018-12-20T11:17:42Z\nNo. of bitstreams: 0", "language": "en", "element": "description", "qualifier": "provenance", "schema": "dc"}, {"key": "dc.description.provenance", "value": "Made available in DSpace on 2018-12-20T11:17:42Z (GMT). No. of bitstreams: 0\n Previous issue date: 2018", "language": "en", "element": "description", "qualifier": "provenance", "schema": "dc"}, {"key": "dc.format.extent", "value": "80", "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": "SINIS tunnel junction", "language": "", "element": "subject", "qualifier": "other", "schema": "dc"}, {"key": "dc.title", "value": "Tunnel junction thermometry on three-dimensional phononic crystals", "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-201812205271", "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": "polystyreeni", "language": null, "element": "subject", "qualifier": "yso", "schema": "dc"}, {"key": "dc.subject.yso", "value": "kiteet", "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": "l\u00e4mp\u00f6tila", "language": null, "element": "subject", "qualifier": "yso", "schema": "dc"}, {"key": "dc.subject.yso", "value": "polystyrene", "language": null, "element": "subject", "qualifier": "yso", "schema": "dc"}, {"key": "dc.subject.yso", "value": "crystals", "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": "temperature", "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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