Production and nature of highly luminescent spark-processed porous oxides of silicon and other elements

450 Pages·2000·15.1 MB·English

by  Stora, Michael Emery,

PRODUCTIONANDNATUREOFHIGHLYLUMINESCENTSPARK-PROCESSED
POROUSOXIDESOFSILICONANDOTHERELEMENTS
By
MICHAELEMERYSTORA
ADISSERTATIONPRESENTEDTOTHEGRADUATESCHOOL
OFTHEUNIVERSITYOFFLORIDAINPARTIALFULFILLMENT
OFTHEREQUIREMENTSFORTHEDEGREEOF
DOCTOROFPHILOSOPHY
UNIVERSITYOFFLORIDA
2000
Copyright2000
by
MichaelEmeryStora
Dedicatedtomyparents,MichelleMoniqueandEmeryLesterStora
ACKNOWLEDGEMENTS
Firstandforemost,Iwouldliketoexpressmyappreciationandheartfelt
thankstoDr.Hummelwhohasservedasmyresearchadvisor,graduateadvisor,
supervisor,supervisorycommitteechairman,andmentor. Hisenthusiasm,support,
interest,andhumorhavebeeninvaluabletome. IalsowishtothankDr.Ludwigfor
hisfriendship,creativity,andtechnicalcontributions.
IthankDrs.HollowayandDeHoffforbothservingonmysupervisory
committeeandfortheirinfluenceasprofessors. Itwasapleasuretolearnfromboth
ofthemastheirclasseswereamongthemostinterestingandproductiveIhavetaken.
IgraciouslythankDrs.SigmundandSrivastavafortheirserviceonmy
supervisorycommittee.
IamgratefultomycurrentandformercoworkersincludingNigelShepherd,
William"Grif"Wise,JeliazkoPolihronov,DavidBurton,Damien"Cross"Reardon,
JonHack,Dr.Sung-SikChang,andDr.DavidMaloneforboththeirtechnical
contributionsandvaluedfriendship. IalsowishtothankDr.PhilipRack.Dr.
JonathanGorrell,JayLewis,andLorenReith,fortheirfriendshipandconstant
willingnesstohelp.
Dr.Holloway'ssecretary,Ludie,deservesspecialrecognitionforbeingthede
facto"secretary"forallofusgraduatestudents.
IamgratefultothestaffandgraduatestudentsoftheUniversityof
Rochester'sCenterforPhoto-InducedChargeTransfer,particularlySteveAtherton
andChrisCollison,fortheequipment-timeandtrainingtheysograciouslyprovided.
IV
Dr.RobertWalkoatSandiaNationalLaboratoriesandDr.Sey-ShingSunatPlanar
Systemsfortheirhelpwithconstructingelectroluminescentdevices,andDr.Regina
Muller-MachatAgilentTechnologyforhelpwithphotoluminescenceexcitation
measurements. IalsowishtothankDrs.GerdMiillerandB.C.Blassefortheir
interestandhelpfuladviceandDr.HerbertRueferatWacker-Chemitronicfor
supplyingthelargequantitiesofsiliconwafersusedinthisstudy.
MythanksgotoallmyfriendsintheUFKodenkanJiu-JitsuClubandUF
JudoClubwhoaretoonumeroustolist. IoweagreatdealtoProfessorsAlex
Limbaugh,DonaldCox,andBillBeach,andSenseisMargaretLimbaugh,Kevin
Book(deceased),andJohnNelsonwhoselessonsofhardwork,discipline,and
dedicationwereasimportantasanyacademiclesson.
Thankstomycollegeroommatesandlong-timefriendsDr.DmitryGolovko
and"soon-to-beDr."DavidHarrisonforthefriendshipandencouragementtheyhave
givenmeovertheyears.
Last,butcertainlynotleast,Iwishtothankmyparents,towhomthisstudyis
dedicated,andmyfianceeHeatherRosefortheundyingloveandsupporttheyhave
givenme.
TABLEOFCONTENTS
page
ACKNOWLEDGEMENTS iv
ABSTRACT viii
CHAPTERS
1 INTRODUCTION l
2 CONVENTIONSANDORGANIZATION 5
UnitsofMeasure *
DefinitionsandRules "*
OrganizationofExperimentalResults 13
3 BACKGROUNDANDLITERATUREREVIEW 14
ReviewofSpark-ProcessedSiliconLiterature 14
OtherLiteratureonSpark-ProcessingandSparksinGeneral 57
ReviewofQuantumSize-EffectLiterature 61
ReviewofDefectsinSilicaandSiliconOxynitrides 71
ReviewofanImportantTransientDefectinSilica 75
GeneralReviewofLuminescenceProcesses 93
4 MATERIALS,METHODS,ANDEQUIPMENT 107
5 RESULTS:PROCESSINGPARAMETERSOFSPARK-PROCESSED
SILICON H9
Electrical,Temporal,andPhysicalProcessingParameters 119
ChemicalProcessingParameters 180
6 RESULTS:MICROSCOPYANDCHEMICALSPECTROSCOPIES
OFSPARK-PROCESSEDSILICON 209
ScanningElectronMicroscopy(SEM) 209
FourierTransformInfraredSpectroscopy(FTIR) 215
Secondary-IonMassSpectroscopy(SIMS) 220
vi
1
7 RESULTS:OTHERSPARK-PROCESSEDELEMENTS 235
PreliminaryExploration 235
AdditionalWorkwithSelectedElements 258
ChemicalProcessingParameters 265
8 RESULTS:OTHERLUMINESCENTSPECTROSCOPIES 300
VariableExcitationPower 300
High-TemperaturePhotoluminescentSpectroscopy 306
PhotoluminescentExcitationSpectroscopy(PLE) 326
Time-ResolvedPhotoluminescentSpectroscopy(TRPL) 336
9 RESULTS:MISCELLANEOUS 367
UsefulResults 367
InterestingResults 371
UninterestingResults 372
10 FURTHERDISCUSSION 374
FinalWordonQuantumDots 374
IntegratingResultsfromMultipleChapters 376
SUMMARYANDCONCLUSIONS 389
1
12 FUTUREWORK 393
APPENDICES
A ELECTROLUMINESCENCEANDPHOTOCONDUCTIVITY 395
B CALIBRATIONOFTHEPLSYSTEM 402
C COMPUTERPROGRAMS 416
REFERENCES 429
BIOGRAPHICALSKETCH 438
VII
AbstractofDissertationPresentedtotheGraduateSchool
oftheUniversityofFloridainPartialFulfillmentofthe
RequirementsfortheDegreeofDoctorofPhilosophy
PRODUCTIONANDNATUREOFHIGHLYLUMINESCENTSPARK-
PROCESSEDPOROUSOXIDESOFSILICONANDOTHERELEMENTS
By
MichaelEmeryStora
December,2000
Chairman:ProfessorRolfE.Hummel
MajorDepartment:MaterialsScienceandEngineering
Spark-processedsilicon(sp-Si)isanovelnano-porousmaterialwithunique
opticalandmagneticproperties. Sp-Siexhibitstwobroad,intense,room-temperature
photoluminescence(PL)bands,whicharelocatednear370nmand530nmwhen
excitedby325nmUVlight. TheseareknownastheUV/bluebandandthegreen
band,respectively. Inaddition,anumberofotherelementshavebeenshowto
exhibitsignificantPLwhenspark-processed.
SeveralPLspectroscopicmethodswereusedtocharacterizesp-Siandother
spark-processedmaterials. Theseincludedcontinuous-wavePL(CWPL).time-
resolvedPL(TRPL),PLexcitationspectroscopy(PLE),andtemperature-dependent
PLmeasurements. Inadditionscanningelectronmicroscopy(SEM),Fourier
transforminfraredspectroscopy(FTIR),andsecondary-ionmassspectroscopy
(SIMS)wereutilized.
viii
Theinfluencesofthechemical,physical,electrical,andtemporalprocessing
parametersonthePLofsp-Siandotherspark-processedelementswereextensively
exploredandcharacterized. BothPLbandsofsp-Siaswellassimilarbandsinsp-
Ge,sp-Al,andsp-Tawerefoundtobestronglydependentonthepresenceofnitrogen
intheprocessingambient. ThePLofsp-Siandseveralotherspark-processed
materialswasfoundtoexhibitextremelyfastsub-10pslifetimes. Longer-lived
componentsattributedtotrappingandevidenceofcompetitionbetweenthetwoPL
bandsofsp-Siindicatechargetransferbetweenseparateabsorptionandemission
mechanisms.
AmodelforthePLmechanismsofsp-Siisproposed. Thismodelexplains
theobservedpropertiesofbothPLbandsofsp-Siandmaybeextendedtoother
spark-processedmaterials. AbsorptionofUVlightisattributedtoastableversionof
anormallymetastabledefectfoundinsilica,andmanyothermaterials,knownasthe
self-trappedexciton(STE). Therapidmeltingandsolidificationduringspark-
processingisbelievedto"quench-in"thisdefect. PLemissionistheresultofcharge
transferofcarriersfromSTEstonitrogen-relateddeepdefectstateswithinthesilica
band-gap. TheUV/bluebandisattributedtodefectscontainingnitrogenandthe
greenbandisattributedtomorecomplicateddefectscontainingtwoormorenitrogen
atoms,similarinnaturetotheN-Nnearest-neighborcenterinGaP.
IX
CHAPTER
1
INTRODUCTION
Siliconhasdominatedthesemiconductorindustryformorethanhalfand
century. Whileothermaterialsareoftenusedforhighpowerswitchingand
rectification,theroleofsiliconinthemicroelectronicsindustryisofparamount
importance. Thevastmajorityofintegratedcircuittechnologyisbasedonsilicon
[Pea88]. Siliconiseconomical(costingaboutatenthasmuchasgalliumarsenide,its
nearestcompetitor)andeasytomanufacture. Thetechnologytodopesiliconwitha
numberofdonorandacceptorelementsismatureandwellbehaved. Themost
significantadvantageofsiliconisthatithasastable,adherent,andeasilygrown
oxidethatisepitaxialandself-passivating(especiallyforthe(100)crystal
orientation)[May901. Thisoxidemaybeselectivelypatternedandetchedby
hydroflouric(HF)acid,whichcrystallinesiliconresists. Finally,siliconisnon-toxic
andsiliconproductionandprocessinghasaminimalimpactontheenvironment.
Thisisnottrueofgalliumarsenide. Thesetechnicaladvantages,combinedwiththe
maturityof,andinvestmentin,silicon-basedtechnologymakeitlikelythatsilicon
willremainthedominantsemiconductormaterialfortheforeseeablefuture.
Despiteitsadvantages,siliconhasmajorlimitations. Itisbothalowband-
gapandindirectband-gapmaterial. Itislimitedtoveryinefficientopticalemission
inthenear-infrared(IR)regionoftheelectromagneticspectrum. Itispoorlysuitedto
bothelectro-opticalcommunicationanddisplaytechnology. Forthesereasons,
galliumarsenideandotherIII-V(orII-VI)semiconductorsandtheiralloysare
typicallyusedinapplicationswherelightemissionisnecessary,whileothernon-