Nanostructured thin films for thermoelectric and sensing applications

Mikko Ruoho

Nanostructured thin films for thermoelectric and sensing applications

Julkaisun otsikon käännös: Nanorakenteiset ohutkalvot lämpösähkö- ja anturisovelluksiin

Mikko Ruoho

Tutkimustuotos: Doctoral Thesis › Collection of Articles

Abstrakti

Lämpö on arkinen energianlähde, ja lämmön avulla tuotetaankin suurin osa ilmiskunnan kuluttamasta energiasta. Lämpöenergian muuntamisessa työksi ja palveluiksi hyötysuhde jää kuitenkin heikoksi, niinpä ratkaisuille, jotka pystyvät parantamaan energiamuunnoksen hyötysuhdetta on suuri tarve. Lämpösähköiset materiaalit kykenevät parantamaan energiarehokkuutta muuntamalla lämmön sähköksi Seebeckin ilmiön avulla. Lämpösähköisen muunnonshyötysuhteen parantaminen, esimerkiksi materiaalin mikrorakennetta räätälöimällä, muodostaa suuren haasteen materiaalitutkimukselle. Nanotekniikkassa on puolestaan kehitetty menetelmiä, joilla kyetään räätälöimään varauksenkuljetusilmiöitä, jotka määräävät lämpösähköisen teholähteen hyötysuhteen. Tässä väitöskirjassa tutkitaan lämpösähköisiä ohutkalvomateriaaleja sekä niiden sovelluksia. Työ keskittyy lämpösähköisten ominaisuuksien mittamiseen käytettyjen kokeellisten menetelmien kehitykseen, nanorakenteisten ohutkalvojen ominaisuuksien tutkimiseen sekä näihin perustuvien uusien sovelluksien kehittämiseen. Tässä väitöskirjassa esitellään menetelmä, jolla kyetään optisesti mittaamaan ohutkalvojen pinnansuuntainen lämmönjohtavuus. Menetelmä laajentaa näyteenpaksuutta yli kahdella kertaluokalla, mikä kyetään selvittämään käytetyllä mittausperiaatteela. Lisäksi väitöskirjassa tutkitaan alumiiniseostuksen vaikutusta sinkkioksidiohutkalvojen lämpösähköisiin ominaisuuksiin. Työssä myös muokataan ohutkalvojen nanorakennetta kasvattamalla ohutkalvot huokoiselle alustalle. Lopulta ohutkalvoja sovelletaan uudenlaisena läpinäkyvänä ja taipuvana kosketusanturina. Sovelluksessa hyödynnetään Seebeckin ilmiön aikaan saamaa passiivista jännitesignaalia, joka tekee anturista vähän virtaa kuluttavan sekä hyvin soveltuvan suuren pinta-alan sovelluksiin. Esitetyt tulokset mahdollistavat uusia sovelluksia sekä anturoinnissa että energiatehokkuuden parantamisessa. Työ luo pohjaa läpinäkyvien ja lämpösähköisten materiaalien tutkimusalalle sekä niihin perustuville sovelluksille.

Julkaisun otsikon käännös	Nanorakenteiset ohutkalvot lämpösähkö- ja anturisovelluksiin
Alkuperäiskieli	Englanti
Pätevyys	Tohtorintutkinto
Myöntävä instituutio	Aalto-yliopisto
Valvoja/neuvonantaja	Tittonen, Ilkka, Vastuuprofessori
Kustantaja	Aalto University
Painoksen ISBN	978-952-60-7191-6
Sähköinen ISBN	978-952-60-7190-9
Tila	Julkaistu - 2016
OKM-julkaisutyyppi	G5 Artikkeliväitöskirja

Tutkimusalat

lämpösähköinen ilmiö
ohutkalvo
sinkkioksidi
nanorakenteet
atomikerroskasvatus
lämmönjohtavuus

YK:n kestävän kehityksen tavoitteet

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Pääsy asiakirjaan

http://urn.fi/URN:ISBN:978-952-60-7190-9Lisenssi: Määrittelemätön

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Aalto-yliopisto
Laitteistot/tilat: Facility
OtaNano Nanofab
Repo, P. (Manager) & Rissanen, A. (Other)
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@phdthesis{a8ec739c8ff4474da48d336c11c75d0d,

title = "Nanostructured thin films for thermoelectric and sensing applications",

abstract = "Thermal energy constitutes a natural source of energy and most energy consumed is finally converted to heat. However, the overall energy conversion process remains inefficient creating the need for solutions that may be used to improve the efficiency. Thermoelectric materials offer an opportunity to improve the energy efficiency in thermal processes by converting the waste heat directly into electricity in a solid state material via the Seebeck effect. Since the achieved conversion efficiency remains still relatively low, a great challenge for materials research is to improve thermoelectric performance for example by microscopic tailoring of materials. Finally, nanotechnology has brought along many methods for tailoring the underlying conduction mechanisms that determine the performance of thermoelectric generators. Novel thermoelectric thin film materials and their applications are studied in this thesis. The presented research focuses on the development of metrology for the characterization of thermoelectric material properties, studies the thermoelectric properties of nanostructured materials and presents novel application of transparent thermoelectric thin films. In this thesis a method to measure the in-plane thermal conductivity of thin films using laser flash apparatus is presented. With this method one can expand the thickness range of samples that can be measured with laser flash analysis by more than two orders of magnitude. In addition, Al-doping of zinc oxide (ZnO) thin films is studied and the effect of the doping on thermoelectric performance of the films is determined. Nanostructuring of ZnO films is demonstrated by large-area conformal coatings by ALD. The work demonstrates the use of geometrical effects for the reduction the resistance of thermocouples fabricated in such a fashion. Accordingly, this work reports on the opportunity to double the generated power of any planar thermoelectric generator. Finally, the ZnO material is applied in a novel transparent thermal touch panel. The proposed concept takes advantage of the thermoelectric voltage generation allowing passive sensing and making the concept very interesting for large-area and low-power applications. The results presented in this thesis enable novel applications and solutions both for energy conversion and sensing. Consequently, the outcomes are forming the basis for a novel field of transparent and flexible thermoelectrics.",

keywords = "thermoelectric, thin film, zinc oxide, atomic layer deposition, nanostructure, thermal conductivity, l{\"a}mp{\"o}s{\"a}hk{\"o}inen ilmi{\"o}, ohutkalvo, sinkkioksidi, nanorakenteet, atomikerroskasvatus, l{\"a}mm{\"o}njohtavuus, thermoelectric, thin film, zinc oxide, atomic layer deposition, nanostructure, thermal conductivity",

author = "Mikko Ruoho",

year = "2016",

language = "English",

isbn = "978-952-60-7191-6",

series = "Aalto University publication series DOCTORAL DISSERTATIONS",

publisher = "Aalto University",

number = "263",

address = "Finland",

school = "Aalto University",

}

TY - BOOK

T1 - Nanostructured thin films for thermoelectric and sensing applications

AU - Ruoho, Mikko

PY - 2016

Y1 - 2016

N2 - Thermal energy constitutes a natural source of energy and most energy consumed is finally converted to heat. However, the overall energy conversion process remains inefficient creating the need for solutions that may be used to improve the efficiency. Thermoelectric materials offer an opportunity to improve the energy efficiency in thermal processes by converting the waste heat directly into electricity in a solid state material via the Seebeck effect. Since the achieved conversion efficiency remains still relatively low, a great challenge for materials research is to improve thermoelectric performance for example by microscopic tailoring of materials. Finally, nanotechnology has brought along many methods for tailoring the underlying conduction mechanisms that determine the performance of thermoelectric generators. Novel thermoelectric thin film materials and their applications are studied in this thesis. The presented research focuses on the development of metrology for the characterization of thermoelectric material properties, studies the thermoelectric properties of nanostructured materials and presents novel application of transparent thermoelectric thin films. In this thesis a method to measure the in-plane thermal conductivity of thin films using laser flash apparatus is presented. With this method one can expand the thickness range of samples that can be measured with laser flash analysis by more than two orders of magnitude. In addition, Al-doping of zinc oxide (ZnO) thin films is studied and the effect of the doping on thermoelectric performance of the films is determined. Nanostructuring of ZnO films is demonstrated by large-area conformal coatings by ALD. The work demonstrates the use of geometrical effects for the reduction the resistance of thermocouples fabricated in such a fashion. Accordingly, this work reports on the opportunity to double the generated power of any planar thermoelectric generator. Finally, the ZnO material is applied in a novel transparent thermal touch panel. The proposed concept takes advantage of the thermoelectric voltage generation allowing passive sensing and making the concept very interesting for large-area and low-power applications. The results presented in this thesis enable novel applications and solutions both for energy conversion and sensing. Consequently, the outcomes are forming the basis for a novel field of transparent and flexible thermoelectrics.

AB - Thermal energy constitutes a natural source of energy and most energy consumed is finally converted to heat. However, the overall energy conversion process remains inefficient creating the need for solutions that may be used to improve the efficiency. Thermoelectric materials offer an opportunity to improve the energy efficiency in thermal processes by converting the waste heat directly into electricity in a solid state material via the Seebeck effect. Since the achieved conversion efficiency remains still relatively low, a great challenge for materials research is to improve thermoelectric performance for example by microscopic tailoring of materials. Finally, nanotechnology has brought along many methods for tailoring the underlying conduction mechanisms that determine the performance of thermoelectric generators. Novel thermoelectric thin film materials and their applications are studied in this thesis. The presented research focuses on the development of metrology for the characterization of thermoelectric material properties, studies the thermoelectric properties of nanostructured materials and presents novel application of transparent thermoelectric thin films. In this thesis a method to measure the in-plane thermal conductivity of thin films using laser flash apparatus is presented. With this method one can expand the thickness range of samples that can be measured with laser flash analysis by more than two orders of magnitude. In addition, Al-doping of zinc oxide (ZnO) thin films is studied and the effect of the doping on thermoelectric performance of the films is determined. Nanostructuring of ZnO films is demonstrated by large-area conformal coatings by ALD. The work demonstrates the use of geometrical effects for the reduction the resistance of thermocouples fabricated in such a fashion. Accordingly, this work reports on the opportunity to double the generated power of any planar thermoelectric generator. Finally, the ZnO material is applied in a novel transparent thermal touch panel. The proposed concept takes advantage of the thermoelectric voltage generation allowing passive sensing and making the concept very interesting for large-area and low-power applications. The results presented in this thesis enable novel applications and solutions both for energy conversion and sensing. Consequently, the outcomes are forming the basis for a novel field of transparent and flexible thermoelectrics.

KW - thermoelectric

KW - thin film

KW - zinc oxide

KW - atomic layer deposition

KW - nanostructure

KW - thermal conductivity

KW - lämpösähköinen ilmiö

KW - ohutkalvo

KW - sinkkioksidi

KW - nanorakenteet

KW - atomikerroskasvatus

KW - lämmönjohtavuus

KW - thermoelectric

KW - thin film

KW - zinc oxide

KW - atomic layer deposition

KW - nanostructure

KW - thermal conductivity

M3 - Doctoral Thesis

SN - 978-952-60-7191-6

T3 - Aalto University publication series DOCTORAL DISSERTATIONS

PB - Aalto University

ER -

Nanostructured thin films for thermoelectric and sensing applications

Abstrakti

Tutkimusalat

YK:n kestävän kehityksen tavoitteet

Pääsy asiakirjaan

Sormenjälki

Laitteet

OtaNano

OtaNano Nanofab

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