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[{"key": "dc.contributor.author", "value": "H\u00e4m\u00e4l\u00e4inen, Joni", "language": null, "element": "contributor", "qualifier": "author", "schema": "dc"}, {"key": "dc.date.accessioned", "value": "2013-06-15T10:00:12Z", "language": "", "element": "date", "qualifier": "accessioned", "schema": "dc"}, {"key": "dc.date.available", "value": "2013-06-15T10:00:12Z", "language": "", "element": "date", "qualifier": "available", "schema": "dc"}, {"key": "dc.date.issued", "value": "2013", "language": null, "element": "date", "qualifier": "issued", "schema": "dc"}, {"key": "dc.identifier.other", "value": "oai:jykdok.linneanet.fi:1270152", "language": null, "element": "identifier", "qualifier": "other", "schema": "dc"}, {"key": "dc.identifier.uri", "value": "https://jyx.jyu.fi/handle/123456789/41779", "language": "", "element": "identifier", "qualifier": "uri", "schema": "dc"}, {"key": "dc.description.abstract", "value": "Gas detection at small concentrations is usually done using transition metal oxides. These\r\nsemiconductors are, however, strongly dependent on parameters and conditions of growth\r\nand processing. Graphene attracts a big interest in science and technology due to its\r\nexceptional electric properties, and this truly 2-dimensional material has a great promise to be used as highly sensitive gas sensor. In this thesis, CVD and epitaxial graphene samples have been investigated in order to improve their sensitivity in gas sensing applications. The response of the sensor to different concentrations of detected gas was observed as a relative change of resistance of the sample. The aim of this study was to find optimal parameters in application of a graphene based gas sensor, and to optimize the contacting area between\r\ngraphene and metal for achieving stable contacts with low resistance. Three different kinds of\r\nmetal-graphene contacts and several different metals for contacting to graphene were studied.\r\nDifferent temperatures and humidity levels as well as irradiation with 370 nm UV-light were\r\nused to find optimal conditions for sensing NO2 gas. The sensitivity to O3 was also studied. An\r\noptimized sensor exhibited response to 20 ppb concentration of O3. In NO2 detection, the\r\nresponse was increased significantly by heating samples above 100 \u00b0C. In a tested epitaxial\r\nSiC sample, the resistive response to 10 ppb concentration of NO2 increased from 0.8 % in\r\nnormal temperature to 1.4 % in elevated temperatures. Increasing of the temperature was also\r\nfound to improve the linearity of response and to increase desorption rate of the molecules\r\nfrom graphene surface, allowing faster recovery after exposure. Annealed contacts with an\r\nadditional graphite layer under the topmost metal layer, and with striped and dot-like\r\ngeometry were found to have lower contact resistance (around 600 \u03a9) than a traditional\r\ncontact with no additional patterning or graphite.", "language": "en", "element": "description", "qualifier": "abstract", "schema": "dc"}, {"key": "dc.description.abstract", "value": "Pienten kaasupitoisuuksien mittaus on perinteisesti suoritettu erilaisilla metalli-oksidiantureilla.\r\nN\u00e4iden puolijohdemateriaalien ominaisuudet ovat kuitenkin vahvasti riippuvia\r\nvalmistusprosessin olosuhteista ja parametreist\u00e4. Grafeeni on t\u00e4ll\u00e4 hetkell\u00e4 tiedeyhteis\u00f6n\r\nmielenkiinnon kohteena erikoisten s\u00e4hk\u00f6isten ominaisuuksiensa vuoksi. T\u00e4m\u00e4 kaksiulotteinen\r\nmateriaali tarjoaa mahdollisuuden eritt\u00e4in pienien kaasupitoisuuksien tarkkaan mittaamiseen.\r\nT\u00e4ss\u00e4 ty\u00f6ss\u00e4 CVD- ja epitaksikasvatettuja grafeenin\u00e4ytteit\u00e4 on tutkittu niiden\r\nkaasuntunnistuskyvyn parantamiseksi. My\u00f6s kolmea erilaista metalli-grafeeni-kontaktia ja\r\nuseita eri metalliyhdistelmi\u00e4 tutkittiin. T\u00e4m\u00e4n ty\u00f6n tavoitteena oli l\u00f6yt\u00e4\u00e4 parhaat mahdolliset\r\nymp\u00e4rist\u00f6olosuhteet grafeeniantureiden resistiivisen vasteen mittaamiseen perustuvia\r\nkaasutunnistussovelluksia varten sek\u00e4 pienent\u00e4\u00e4 kontaktiresistanssia ja parantaa metalligrafeeni-\r\nkontaktien luotettavuutta. Optimaalisten olosuhteiden l\u00f6yt\u00e4miseksi grafeenin\r\nherkkyytt\u00e4 NO2-kaasulle testattiin eri l\u00e4mp\u00f6tiloissa, eri kosteusolosuhteissa ja 370 nm UVs\u00e4teilyn\r\naikana. Grafeenin herkkyytt\u00e4 O3-kaasulle tutkittiin my\u00f6s. 20 miljardisosan (ppb) O3-\r\npitoisuus riitti aiheuttamaan huomattavan muutoksen grafeenin resistanssissa. NO2-\r\nmittauksissa resistiivist\u00e4 vastetta eri kaasupitoisuuksille pystyttiin parantamaan huomattavasti\r\nl\u00e4mmitt\u00e4m\u00e4ll\u00e4 n\u00e4ytteit\u00e4 yli 100 \u00b0C l\u00e4mp\u00f6tilaan. Resistanssin muutos huoneenl\u00e4mm\u00f6ss\u00e4 oli\r\nnoin 0.8 % ja l\u00e4mmityksen j\u00e4lkeen noin 1.4 % epitaksikasvatetulle n\u00e4ytteelle 10 ppb:n NO2-\r\nkonsentraatiota mitattaessa. Korkeat l\u00e4mp\u00f6tilat my\u00f6s paransivat vasteen lineaarisuutta ja\r\nnopeuttivat grafeenipinnalle adsorpoituneiden molekyylien desorptiota, puhdistaen grafeenin\r\npintaa ja mahdollistaen nopean palautumisen altistuksesta kaasulle. L\u00e4mp\u00f6k\u00e4sitellyt kontaktit\r\nja grafiittikerros ylimm\u00e4n metallikerroksen alla pienensiv\u00e4t kontaktiresistanssia. Pistem\u00e4isill\u00e4\r\nja sormimaisilla kontaktityypeill\u00e4 saatiin kontaktiresistanssia pienennetty\u00e4 verrattuna\r\nperinteiseen suoraan kontaktipintaan. Sormimaisella, kahdesti l\u00e4mp\u00f6k\u00e4sitellyll\u00e4 kontaktilla,\r\njossa oli grafiittikerros ylimm\u00e4n metallikerroksen alla, kontaktiresistanssi oli pienimmill\u00e4\u00e4n\r\nnoin 600 \u03a9.", "language": "fi", "element": "description", "qualifier": "abstract", "schema": "dc"}, {"key": "dc.description.provenance", "value": "Submitted using Plone Publishing form by Joni H\u00e4m\u00e4l\u00e4inen (jojuhama) on 2013-06-15 10:00:10.062142. Form: Pro gradu -lomake (1 tekij\u00e4) (https://kirjasto.jyu.fi/julkaisut/julkaisulomakkeet/pro-gradu-lomake-1-tekijae). JyX data:", "language": "en", "element": "description", "qualifier": "provenance", "schema": "dc"}, {"key": "dc.description.provenance", "value": "Submitted by jyx lomake-julkaisija (jyx-julkaisija@noreply.fi) on 2013-06-15T10:00:12Z\r\nNo. of bitstreams: 2\r\nURN:NBN:fi:jyu-201306151982.pdf: 15341966 bytes, checksum: b365b2ee016efdb2d05284bfd868502f (MD5)\r\nlicense.html: 107 bytes, checksum: a7d86e598caa500b1b433bbb9dc8ef1c (MD5)", "language": "en", "element": "description", "qualifier": "provenance", "schema": "dc"}, {"key": "dc.description.provenance", "value": "Made available in DSpace on 2013-06-15T10:00:12Z (GMT). No. of bitstreams: 2\r\nURN:NBN:fi:jyu-201306151982.pdf: 15341966 bytes, checksum: b365b2ee016efdb2d05284bfd868502f (MD5)\r\nlicense.html: 107 bytes, checksum: a7d86e598caa500b1b433bbb9dc8ef1c (MD5)\r\n Previous issue date: 2013", "language": "en", "element": "description", "qualifier": "provenance", "schema": "dc"}, {"key": "dc.format.extent", "value": "1 verkkoaineisto.", "language": null, "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": "grafeeni", "language": "", "element": "subject", "qualifier": "other", "schema": "dc"}, {"key": "dc.subject.other", "value": "graphene", "language": "", "element": "subject", "qualifier": "other", "schema": "dc"}, {"key": "dc.subject.other", "value": "gas sensing", "language": "", "element": "subject", "qualifier": "other", "schema": "dc"}, {"key": "dc.subject.other", "value": "NO2", "language": "", "element": "subject", "qualifier": "other", "schema": "dc"}, {"key": "dc.subject.other", "value": "O3", "language": "", "element": "subject", "qualifier": "other", "schema": "dc"}, {"key": "dc.title", "value": "Graphene films for gas sensing applications", "language": null, "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-201306151982", "language": null, "element": "identifier", "qualifier": "urn", "schema": "dc"}, {"key": "dc.type.dcmitype", "value": "Text", "language": "en", "element": "type", "qualifier": "dcmitype", "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": "University of Jyv\u00e4skyl\u00e4", "language": "en", "element": "contributor", "qualifier": "organization", "schema": "dc"}, {"key": "dc.contributor.organization", "value": "Jyv\u00e4skyl\u00e4n yliopisto", "language": "fi", "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": "dc.date.updated", "value": "2013-06-15T10:00:12Z", "language": "", "element": "date", "qualifier": "updated", "schema": "dc"}, {"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": "fi", "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": null, "element": "subject", "qualifier": "oppiainekoodi", "schema": "dc"}, {"key": "dc.subject.yso", "value": "grafeeni", "language": null, "element": "subject", "qualifier": "yso", "schema": "dc"}, {"key": "dc.subject.yso", "value": "kaasut", "language": null, "element": "subject", "qualifier": "yso", "schema": "dc"}, {"key": "dc.subject.yso", "value": "mittaus", "language": null, "element": "subject", "qualifier": "yso", "schema": "dc"}, {"key": "dc.subject.yso", "value": "mittausmenetelm\u00e4t", "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": 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