Fabrication and characterization of nanometer-sized metal and semiconductor particles and nanometer-sized composites

203 Pages·1996·7.4 MB·English

by  Li, Tuo, 1959-

FABRICATIONANDCHARACTERIZATIONOFNANOMETER-SIZEDMETALAND
SEMICONDUCTORPARTICLESANDNANOMETER-SIZEDCOMPOSITES
By
TUOLI
ADISSERTATIONPRESENTEDTOTHEGRADUATESCHOOL
OFTHEUNIVERSITYOFFLORIDAINPARTIALFULFILLMENT
OFTHEREQUIREMENTSFORTHEDEGREEOF
DOCTOROFPHILOSOPHY
UNIVERSITYOFFLORIDA
1996
Dedicatedto:
myfamily
inappreciationoftheirpatience,supportandencouragement
ACKNOWLEDGMENTS
Firstofall,Iwouldliketoexpressthemostsincerethankstomyadvisor.Dr.
JamesH.Adair,forhisguidance,encouragement,andconstructivecriticismthroughout
myresearch,andmakingmebecomeahands-onengineer. Theexperienceofworking
withhimhasbeenrewardinginmanyways. Secondly,Iwouldliketoexpressmy
gratitudetoDrs.RolfHummel,StephenPearton,andBrijMoudgiloftheDepartmentof
MaterialsScienceandEngineering,andDr.DavidReitzeoftheDepartmentofPhysicsfor
servingonmycommittee. IwouldfurtherliketothankDrRobertParkforwillingnessto
serveascommitteemembersubstitutewithshortnotice. SpecialthanksaredirectedtoDrs.
MatthiasLudwig,JosephH.SimmonsandLiWangfortheirhelpwithexperimentsand
usefuldiscussions.
IthankallofmycolleaguesintheAdairResearchGroupattheDepartmentof
MaterialsScienceandEngineering. Thisworkwouldn'tbepossiblewithouttheirhelp.
SpecialthanksaredirectedtoJoohoMoonandCraigHabegerforresearchassistance. I
sincerelyacknowledgethehelpfromPaulDemkowicz,RobertSabia,CraigHabeger,and
HenrikKrarupforthereviewofthismanuscript. IamgratefultoDrs.StanleyBatesand
AugustoMorrone,thestaffoftheMajorAnalyticalInstrumentationCenterattheUniversity
ofFlorida,fortheirtechnicalhelpandanalyticalsupportinthecharacterizationofthe
specimens. IalsowouldliketotakethisopportunitytothankPamHowellforher
administrativesupportandassistanceinmyresearchandAndrewBenderforassistancein
operatingthecomputersystem. IwouldliketoacknowledgeNASAforpartialfinancial
supportofthiswork(NASAGrantNumber:NAG8-1244).
Finally,Iwanttothankmyparents,mywife,andmydaughterfortheirlove,
support,patience,andencouragement,whichhasalwaysbeenasourceofinspiration.
111
TABLEOFCONTENTS
ACKNOWLEDGMENTS
iii
LIST OF TABLES
vi
LISTOFFIGURES
vii
ABSTRACT
xjjj
CHAPTERS
INTRODUCTION
1 1
2 INTRODUCTIONTOQUANTUMDOTSANDTHEIRAPPLICATIONSIN
MICROELECTRONICSANDPHOTONICS 6
2.1.Overview 6
2.2.ApplicationsandPotentialImpacts 12
2.2.1.ExamplesinMicroelectronics 12
2.2.2.ExamplesinPhotonics 17
2.3.QuantumStructuresandAtomAssemblies 24
2.3.1.PhysicalApproachingtoNanometer-SizedStructures 25
2.3.2,ChemicalApproachingtoNanometer-sizedStructures 27
2.3.2.1.Synthesisofnanosizedclustersinorganicandinorganic3-
dimensionalhosts 29
2.3.2.2.Synthesisofnanometer-sizedclustersonlayerhosts 32
2.3.2.3.Synthesisofnanometer-sizedclustersinopen-frameworks 35
2.4.FutureDevelopmentandOutlook 41
3 PREPARATIONOFNANOMETER-SIZEANISOTROPICPARTICLES
USINGSELF-ASSEMBLYMOLECULES AS TEMPLATES 43
3.1.Introduction 43
3.2.SynthesisofCdSPlateletsfromLamellar-BilayerTemplates 49
3.3.ResultsandDiscussion 53
3.3.1.CharacteristicsoftheCdSPlatelets 53
3.3.2.TemplateEffects
3.3.3.InfluenceoftheMetalSaltandConcentrationontheParticle
Formation and Morphology 66
3.3.4.InfluenceoftheOtherProcessingParameterontheParticle
3.4.ConcluFsoiraomntsion 771j
IV
4 PREPARATIONOFNANOMETER-SIZEDCdS/OXIDECOMPOSITE
PARTICLESUSINGREVERSEMICELLESINCONJUNCTIONWITH
METALALKOXIDEHYDROLYSISANDCONDENSATION 74
4.1.4I.n2.t1r.oduction 74
4.2.Background 75
GenearlRemark 75
4.2.2. Reverse Micelles as Microreactors 78
4.3.PreparationofCdS/OxidesSphericalNano-Composites 82
4.3.1.SynthesisofCdS/Si02Nano-Composites 82
4.3.2.SynthesisofCdS/Ti02Nano-Composites 85
4.4.ResultsandDiscussion 88
4.4.1.NucleationandGrowthoftheNanosizeCdSClusters 88
4.4.2.CharacteristicsoftheResultingParticles 91
4.4.3.FormationoftheNano-compositesinMicroemulsionMatrix 95
4.4.3.1.Influenceoftheprocessingparameters 95
4.4.3.2.Mechamismofthenano-compositesformation 97
4.4.3.3.Chemicalmodificationoftitaniumalkoxide 102
4.4.5.OpticalCharacterizationandSize-QuantizationEffects 104
4.5.Conclusions 114
5 SYNTHESISOFAg/Si02NANOMETER-SIZEDCOMPOSITEPARTICLES 117
5.1.Introduction 117
5.2.MaterialsandExperiment 120
5.3.ResultsandDiscussion 123
5.3.1.FormationofAgcolloids 123
5.3.1.1.Effectofratioofthewatertosurfactantonparticlesize 123
5.3.1.2.Effectofthereagent 124
5.3.1.3.Effectofthesolvent 128
5.3.2. Formation of the Nano-composites 129
5.3.2.1.Particlecharacteristics 129
5.3.2.2.Mechanismofthenano-compositeformation 136
5.4.Conclusions j39
6 OPTICALPROPERTIESOFNANO-COMPOSITEAG/Si02PARTICLES 140
6.1.Introduction 140
6.2.GeneralTreatment 141
6.3.LinearandNonlinearOpticalEffectsinMetalClusters 145
6.3.1.SurfacePlasmonModeandLinearOpticalPropertes 145
6.3.2.LinearAbsorptionOpticalSpectraofAgandAg/Si02Clusters 152
6.3.3.NonlinearOpticalPropertiesofAg/Si02Nano-Composites 155
66..33..33..21..LDoecgaelnefriaeltdeefnohuarn-cweamveenmtiaxnidngef(feDcFtiWveMd)ielectriconstant 116596
6.3.3.3.Degenerate-four-wavemixingexperiment 162
6.4.ResultsandDiscussions 166
6.5.Conclusions I74
v
7 CONCLUSIONSANDSUGGESTIONSFORFUTUREWORK 175
7.1.OverallConclusions 175
7.2. Future Work 177
LISTOFREFERENCES 180
BIOGRAPHICAL SKETCH
187
vi
1
LISTOFTABLES
Table page
2-1. Approximateexcitonbindingenergies,Bohrradiiandotherphysical
paremeters for some selected bulk semiconductors 1
4-1. Comparisonofsizeandexcitonictransitionenergy 95
4-2. Productobtainedaccordingtotherelativeratesofhydrolysisandcondensation..103
6-1. Comparisonoftheexperimentalresultswiththetheoreticalcalculations 173
vii
LISTOFFIGURES
Figure page
2-1. Quantumconfinementintheidealsystems,evolutionoftheenergyviadensityof
statesfrombulktozerodimension 8
2-2. BanddiagramoftheInGaAs-In(AlGa)Asresonant-tunnelinghot-electron
transistors(RHET) 13
2-3. QquuaannttuummcCaassccaaddeellaasesre,rsthdeifwfaerveilneangftuhn,daemnteinrtealyldweatyerfmrionmeddiboydqeulaansetrusm. In
confinement,canbetailoredfromthemid-infraredtothesubmillimeterwaveregion
inthesameheterostructurematerials 14
2-4. Ilustrationofpossibleoperatingprincipleofaquantumdotsdataregister 17
2-5. Examplesofanisotropicnonlinearfilterservingasall-opticalswitching,directional
couplercontrolledbytheopticalKerreffect 20
2-6. Quantumconfinementeffectsonopticalabsorption. AsthephotonintensityIis
increased,asmallblueshift(A,i—>^2)isfirstobservedthatisduetohotoinduced
2- cI2haarnegeasbsionrtbheedcarrierconcentrations. Atsaturation,onlyphotonswithwavelengt2h2
3-2-7. NanophysicsfabricationofaGaAsquantumdotarrary 26
2-8. IllustrationoftheinteractionofthestabilizingmediawithQ-CdSclusters, (a)
reversemicelle/hexametaphosphate-stabilizedQ-CdS(b)p-
[(Dimethylamino)methyl]-calix[6]arene-stabilizedQ-CdS 28
2-9. ThehyperlatticearrengementofCdSClustersinadjacentsolaliteunitsofthe
zeoliteY.(hatched=Cd;open=S) 31
2-10.UseofLangmuirfilmcontainingfunctionalgroupstocauseandcontrolnucleation
andgrowthofinorganicmaterials 34
2-1LThedealamphiphilicaggregatesformedinamphiphilicsystemcontaining
amphiphilicmolecules-oil-water 35
12.Synthesisofnanoscaleparticlesinreversemicelles;(a)Twomicroemulsions;(b)
Microemulsionplustrigger;(c)Microemulsionplussecondreactant 38
1. Phasestructuresforanidealself-assemblysystem 47
3-2. PdhiaasgeradmiaogfrSamDsSoMflAamellarbilaye"rs-tructure:(a)partialp•e"s'udotemarv- phase
binary system
51
viii
3-3. ProcessingprocedureusedtosynthesizeCdSplateletsinlamellarbilayerphase..52
3-4. Schematicallyillustratedamphiphilicbilayersactingasatemplateintheformationof
anisotropically-shapednanoscaleinorganicparticles 50
3-5. Micrographsoftheneatphasebilayer(L2)phaseintheSDS/AA-toluene-water
sSyEstMemm:ic(ra)ogorptaipchalofphpoarttoimaillcyrodgrireadphSAofstyhsetseymstemundercrossPolarizer;and(b)54
3-6. TEMmicrographsofCdSplateletspreparedthroughlamellarbilayerphase:(a)CdS
particlesobtainedfromSDS/AA-toluene-aqueoussystem;and(b)CdSparticles
preparedfromoctylamine-aqueoussystem 55
3-7. TEMmicrgraphsofCdSparticlesobtainedfrom(a)conventionalco-precipitation
and(b)highsaltconcentration(0.1M) 57
3-8. DiffrentialabsorptionspectraofCdSplateletsasafunctionofweightratioofwater
to surfactant, W. (a) W=0.8; (b) W=1.0; (c) W=1.2 59
3-9. XRDpatternsoftheprecipitates:(a)beforeposttreatment;(b)afterposttreatment;
(c)conventionalcoprecipitation 60
3-10.TEMmicrographanddiffractionpatternofCdSplatelets 61
3-11.CdSparticlesresultingfromtheternarysystemofSDS/AA-toluene-water,
templatingeffectfromorganicligandofamphiphilicmolecule 64
3-12.Schemeofplateletformationinsidelamellarbilayerstructure 65
3-13.TheeffectofthestartingmaterialsontheformationofCdSparticles:(a)CdS
particlessynthesizedwithCdCl2asastartingmaterialsinSDS/AA-toluene-water
syntem;(b)CdSparticlessynthesizedwithCdCl2asastartingmaterialsin
octylamine-watersystem 67
3-14.C0o.n0c2enMt;ra(tbi)on0.e0f5feMct;s(ocn)0th.e00f5orMamtionofplatelteCdSinlamellarbilayerphase-(a6)9
3-15.Schematicillustrationofthechangeofsolutionbehaviorofsurfactantwiththe
hydrophileandlipophilebalanceinwater-surfactant-hydrocarbonsystem 70
3-16.Theeffectsofequilibrationtimeoflamellarbilayerphaseandagingtimeonthe
formationofCdSplatelets:(a)theeffectofphaseequilibrationtime;and(b)the
effectofagingtime 72
4-1. Shapeofsurfactantmoleculesformingreversemicelles 78
4-2. (a)TheternarydiagramforAerosolOT-isooctane-water,T=15°,(b)quamary
diagramforsodiumdodeso/amylamine-toluene-watersystem 80
4-3. Thedynamicprocessofmicroemulsion 81
4-4. SccohmepmoastiitcesdiagramofthesynthesisproceduresusedtoprepareCdS/Si02nano-
31
4-5. SchematicdiagramofthesynthesisprocedureusedtoprepareCdS/Ti02nano-
compositeandtransparentmonolithicgel 86
4-6. Schematicdiagramofthemodificationprocedureusedfortitaniumisopropoxide.87
4-7. AbsorptionspectraofCdSclusterspreparedthroughtwodifferentsynthesisrouts
inmicroemulsionmatrix, (a)fromtemporalnucleationandgrowth;(b)from
corprecipitation at ambient temperature 90
4-8. X-raydiffractionpatternsoftheCdSclusters,therevolutionofthecrystallinityas
increase the cluster size 92
4-9. TEMmicrographanddiffractionpatternoftheCdSclusterpreparedfrom
microemulsionmatrix 93
4-10.AgalleryofhighresolutionTEM(HRTEM)imagesoftheCdSclusters
havingdifferentsize 94
4-11.(a)CdS/Si02nano-compositessynthesizedfromnonionicsurfactantsystemwith
R=4,H=100,andX=l. (b)XPSspectraofthenano-composites 96
4-12.Mechanismsoftheparticleformationinmicroemulsionreactionmatrix:particle
formationinreversemicelles 98
4-13.Schemeofthecompositeparticleformationinmicroemulsionmatrix 99
4-14.TEMmicrophotographoftheCdS/Ti02nano-compositesynthesizedfromIgepal-
4- cyclohexane-watersystemwithmodifiedtitaniumisopropoxideprecursors(R=5
H=200,X=l) 105
5-
4-15.(a)AbsorptionspectraofCdSclustershavingdifferentsizes,and(b)Comparison
ofabsorptionspectrabetweenCdSclustersanditsnano-composites 106
4-16.(a)Schemiticcorrelationdiagramrelatingclusterstatestobulkcrystalstates.(b)
E(k)diagram:curve1,caseforparabolicband;curve2,trueenergybandwhichis
paraboliconlyneark=0;(•),twoeigenvaluesforthefirstexcitedstate 110
4-17.PXa(rt1i0a0l)barenfdersttorudcitfufreerednitadgirracmtioofnscuwbiitchicnrytshtealulniintecCeldlS. ThelinelabeledL(111)a1n1d
4-18.Sizedependenceofthefirstexcitonictransition,comparedtheexperimentalresults
withthetheoreticalcalculations 11
19.PhotoluminescencespectraoftheCdSclusteranditsnano-composites, (a)PL
spectraasafunctionofthesize,and(b)PLspectraatdifferenttemperature 115
1. Schematicdiagramoftheproceduceusedtopreparenano-compositeAg/Si02...122
5-2. ARbsorptionspectraofAgclustersasafunctionofratioofthewatertosurfactant,
x