raman spectroscopy of thin films - kenyon collegebiology.kenyon.edu/hhmi/posters_2017/lewisv.pdf ·...
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Raman Spectroscopy of Thin FilmsVincent Lewis ’20, Frank Peiris
Kenyon College Summer Science 2017
AbstractRamanSpectroscopyisapowerfulexperimentaltechniquetoanalyzethevibrationalmodesofthinfilms.UsingRamanSpectroscopy,wehaveinvestigatedzirconiainordertodeciphertheirvibrationalmodesandtoexplorethequalityofsample.Thezirconiawasdepositedonsiliconsubstrates,treatedwitheitherOleicAcidorTrioctylphosphine oxide(TOPO),andthencalcinedatspecifictemperatures.Usingacombinationofresultsfrom632nmand532nmlaserspectroscopy,wefoundthatthezirconiaunderwentcrystalphasetransformationaround700to900degreesCelsius.ThespectraofthezirconiatreatedwithTOPOshowedstrongsignsofbothmonoclinicandtetragonalcrystalstructure,resultswhichwereverifiedbyX-raydiffractionaswell.
WealsousedAtomicForceMicroscopytoexplorethetopographyofthezirconiasamples.Fromtheseimageswewereabletocalculatetherootmeansquare,whichistheaverageroughnessofthesurface.
Raman Spectroscopy
Background
Zirconia Samples
Raman Spectra AFM
Conclusions
References1. https://images.nature.com/full/nature-assets/nprot/journal/v11/n4/images_article/nprot.2016.036-F1.jpg2. https://pharm.virginia.edu/files/2014/01/AFM2.jpg3. A. Muñoz Tabares, José & J. Anglada, Marc. (2010). Quantitative Analysis of Monoclinic Phase in 3Y-TZP by Raman Spectroscopy. Journal of the American Ceramic Society. 93. 1790 -1795
AcknowledgmentsThis work was funded by NIH R15 ES011130 to WHP and by the Kenyon College Summer Science Scholars program.
• TheRamanEffect,otherwiseknownasRamanScattering,istheinelasticscatteringofaphotonduetoexcitedvibrationalmodesofamaterial.
• Byshootingalaseratathinfilm,wecanexcitenewvibrationalmodesofamaterial.Sincetheexcitinglaserisinfluencedbythevibrationalmodes,thephotonscanloseorgainenergy.
• WhiletheRayleighScatteringisbyfarthedominantphenomena,RamanScatteringstilloccurs.Thisshiftonlyoccurswithinonepermillionsofthereflectedphotons,andisthusunobservabletothenakedeye.
• ARamanSpectrometerisabletofilteroutalotofthosereflectedphotons,andgraphaspectrumoftheshifts.Thisisonlypossiblethroughexcitationwithasinglewavelength,asnotchfilterscanbeoptimized.
TOPOZirconia• FromourdatawefoundthatTOPOzirconiabeganto
undergoaphasetransformationaround700C.• At900C,theTOPOzirconiahasbothmonoclinicand
tetragonalstructure.• ThisresultswereconfirmedbyX-raydiffraction.OAZirconia• TheOleicAcidzirconiaonlyshowedatetragonal
crystalstructureathighertemperatures.• Theseresultswerealsoconfirmedbyx-raydiffraction.
Analyzing Spectra
• ZirconiumDioxide(zirconia)isacompoundwithmanyemergingusesinindustry
• ZirconiawasspincoatedonSiliconsubstrates,andthentreatedwitheithertrioctylphosphine oxide(TOPO)oroleicacid(OA).
• Thesechemicalsaffectthecrystalphasesofthezirconia.Zirconiacanforminamorphous,monoclinic,tetragonal,andcubicstructures.Thesephasesarereachedthroughexposuretotemperature.Oursampleswereannealedfor168hoursatdifferenttemperaturesrangingfrom300Cto900C.
300COA
AtomicForceMicroscopy• AtomicForceMicroscopy(AFM)usesa
cantilevertomeasureforceonthesurfaceofamaterial.
• Asthecantileverrunsacrossthetopofthematerial,fluctuationsinthesurfaceheightwillapplydifferentforces.
• Piezoelectronics areabletomovethesampleatfinelytunedincrements,whilealaserisreflectedoffofthecantilever.Thepositionofthethelaserisrecordedbyaphotodiode.
• Bycomparingthedisplacementofthelaserwiththedisplacementofthesamplebythepiezoelectronics,weareabletocreateatopographyofthesample.
TOPO
OleicAcid
Vibrationmodesofmonoclinicandtetragonalzirconia[3]
Astheannealingtemperatureincreases,shownintheAFMimages,theindividualcrystallinesizesdecrease.Athightemperatures,thecrystallinesizescorrespondedtotheexpectedzirconiananoparticlesizes
600COA
700COA
TOPO OleicAcid
300CTOPO
900COA
400CTOPO
600CTOPO 800CTOPO
• PicturedaboveareportionsoftheRamanspectraforbothTOPOandOleicAcid
• PicturedtotheupperrightisagraphofgeneralRamanspectraforzirconia,bothmonoclinic,zirconia,andmixedcrystalstructures
• Colorcodedarespecificpeaksatwavenumberscorrespondingtovibrationalenergylevelsofspecificcrystallinestructures
• At146and260𝑐𝑚#$, tetragonalpeaksexist.
• Ataround180and190𝑐𝑚#$,adoublemonoclinicpeakexists.
• Theremainingpeaksinthespectra(suchastheonearound300)arefromthesiliconsubstrate.
• PicturedinthelowerrightisaspectrumofSiliconobtainedinourlab.Thesepeaksalsoappearintheabovespectrabecauseofthesubstrate.
DiagramofAFM[2]
DiagramofRaman[1]
AFM• Thecrystalsizesinimagesweobtained
correspondedtothenanocrystalsizesofzirconia.
300℃ 400℃ 600℃ 700℃ 800℃ 900℃
RamanSpectrumofSiliconin𝑐𝑚#$