纳米固体光发射与吸收

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1、http://www.paper.edu.cnPhotoluminescenceofSinanosolidsnearthelowerendofsizelimit*L.K.Pan,C.Q.Sun,B.K.Tay,T.P.ChenandS.LiSchoolofElectricalandElectronicEngineering,NanyangTechnologicalUniversity,Singapore6397987Interpretationoftheblueshiftinthephotoluminescence(PL)ofthesmallestnanosolid(D~1nm)s

2、eemsdifficultbasedonthecurrentlyavailablemodels.Thischallengesnotsimplyfornumericalconvergencybutimportantlynewphysicshidingbehind.WeexaminedherebythePLblueshiftofSinanosolidssmallerthan3nmbothexperimentallyandtheoretically,leadingtoaconclusionthatarecent‘bondorder-length-strength’(bond-OLS)co

3、rrelationmechanism[J.Phys.Condens.Matter(2002)]isnecessary.AgreementbetweenpredictionsandobservationsrevealsthattheSi-Sisurfacebondcontractsmoresignificantly(by~30%)forthesmallestSinanosolidofwhichthePLblueshiftcorrespondsdirectlytotheriseofsinglebond-energyofthesurfaceatomwithmuchloweredcoord

4、ination.zE-mail:ecqsun@ntu.edu.sg;Fax:6567920415;zLinks:http://www.ntu.edu.sg/home/ecqsun/rtf/si-pl.pdfzOr:http://www.ntu.edu.sg/home/ecqsun/rtf/QC.pdf1http://www.paper.edu.cn1Thediscoveryofefficientphotoluminescence(PL)fromporoussilicon(PS)in1990hasattractedtremendouseffortsonthetunableoptica

5、lpropertiesofsemiconductivenanosolids.Asafirstorderapproximation,thetunablePLpropertyisoftencorrelatedtothesizeofthe2luminescentnanostructures.Simpleparticle-in-a-boxcalculationadoptsthetrappingpotentialofanisolatedatomtothenanosolid,leadingtotheanalogueof‘quantumbox’.Thisconventionderivedthat

6、band-gapwideningoccurswhenreducingthedotsizetotheorderofnm.However,quantitativecorrelationbetweenthebandgapandthedotdimension(D)hasnotyetproducedconvincingresultsforsolidnearthelowerendofsizelimit(<5nm).One−n345oftenexpectsthattheblueshiftfollowsa∆EG(D)/EG(∞)∝Dlaw(n=2,21.16,1.3,1.37).6−nHoweve

7、r,aneffectivemassapproximationconfirmedthattheDdependencesuitsonlyforcrystalliteslargerthanseveralnanometers.Notsurprisingly,seriousconvergenceproblemsarisewhenthesolidisverysmall.Thisisnotsimplyanissueofnumericalbutimportantlyconceptua