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2D phonon thermal transport in thin SiN film

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Authors
Loippo, Teemu
Date
2019
Discipline
FysiikkaPhysics
Copyright
This publication is copyrighted. You may download, display and print it for Your own personal use. Commercial use is prohibited.

 
Tässä tutkielmassa suunnitellaan, valmistetaan ja kokeillaan uudenlaista suprajohde- normaalimetalli-suprajohde (SNS) lämmintintä. Uutta lämmittimessä on sen geometria, jonka on tarkoitus tehdä mittaustulosten analysoinnista helpompaa kuin aiemmin. SNS liitoksen käyttäminen lämmittimenä suprajohde-eriste-normaalimetalli-eriste- suprajohde (SINIS) liitoksen sijaan antaa suuremman tehoalueen tutkittavaksi, sillä SNS liitos on kestävämpi kuin herkkä SINIS liitos. Lisäksi SNS liitoksen etuna on se, että lämpöenergia emittoidaan koko normaalimetallista, kun taas SINIS liitokseen perustuvassa lämmittimessä suurin osa emissiosta tapahtuu tunneliliitoksen alueella. Työssä käytettiin jo aiemmista kokeista tuttua SINIS liitokseen perustuvaa lämpömittaria, mutta liitos oli hieman pienempi kuin aiemmin. SNS ja SINIS liitokset valmistettiin itsekantavan SiN kalvon päälle. Valmistusprosessien optimoinnin jälkeen SiN kalvolle valmisettu näyte mitattiin lämmittämällä kavoa ja samanaikaisesti mitaten kalvon lämpötilaa. Mittauksista saatiin selville SiN kalvon lämmönjohtuvuus, tosin ensimmäinen mitattava näyte ei ollut täydellisen onnistunut ja mittauksessa oli selviä virhelähteitä. Kaikki erot aiempiin mittauksiiin pyrittiin selittämään ja pääosin tulokset olivat samassa linjassa aiempien tulosten kanssa. Kun mittauksiin liittyvät ongelmat saatiin korjattua, olivat uudet mittaustulokset hyviä. Lisäksi lämmöjohtumisen simulaatiomalliin tehtiin muutoksia, jolloin kokeelliset tulokset sopivat lähes täydellisesti yhteen simulaation kanssa. Tulevaisuudessa vastaavanlaiset mittaukset suoritetaan ohuemmille SiN kalvoille ja fononikiderakenteille. ...
 
This thesis contains the design, fabrication and initial tests for a new type of a superconductor-normal metal-superconductor (SNS) heater element. The novel part is the heater geometry, which should make the heating experiment analysis simpler than previously. Also utilizing the SNS junction as a heater instead of a superconductor-insulator-normal metal-insulator-superconductor (SINIS) junction was different compared to the previous experiments. The SNS heater allows greater power range compared to the SINIS heater, beacause SNS junctions are more robust compared to SINIS junctions. Also the heat is emitted from the normal metal, whereas in SINIS heaters most of the heat is emitted from the junction area. In this work the thermometer was a typical SINIS junction with a bit smaller dimensions than in previous experiments. SINIS and SNS junctions were fabricated on top of a suspended SiN membrane. After the fabrication processes were optimized, the thermal conductance of a SiN membrane sample was measured. The first results were promising although the data was aquired by using a non-ideal sample and non-ideal measurement setup. All differences to previously measures samples were explained. Once all issues with the measauremnts were solved the experiments were run again with good results. In addition some modifications to the simulation model were done. The experimental results agreed well with the updated simulation model. Also the heating experiment will be performed for thinner SiN membranes and for a phononic crystal structure in the future. ...
 
Keywords
SINIS thermometry SNS heater ballistic phonons SiN membrane thermal conductivity lämmitys fononit heating (spaces) phonons
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http://urn.fi/URN:NBN:fi:jyu-201904032052

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