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1、NanoStructwedMaterials.Vol.12,pp.101-106,1999PergamonElsevierScienceLtd01999ActaMetallurgicaInc.PrintedintheUSA.Allrightsreserved0965-9773&l/$-seefrontmatterPI1SO9659773(99)00074-4LASERABLATIONDEPOSITIONOFSILICONNANOSTRUCTURESJ.Levoska,M.Tyunina*,andS.LepplvuoriMicroelectronicsandMaterialPhysi
2、csLaboratoriesandEMPARTResearchGroupofInfotechOulu,UniversityofOulu,PL444,FIN-90571Oulu,Finland;*permanentaddress:InstituteofSolidStatePhysics,UniversityofLatvia,Riga,LatviaAbstract-Pulsedlaserdepositionwithanoff-axisgeometryinalow-pressureargonambientwasusedtoproducefilmsofnanosizedsiliconclu
3、stersorcrystallites.Sizeselectionwasachievedbythedistanceofthedepositfromthetarget.Thelocalfilmstructureandthecrystallitesizeofthefilmswerestudiedasafunctionofthedistancefromthetargetusingmi-cro-Ramanspectroscopy.Thenanocrystalsizeontheoff-axisplacedsubstratevariedintherange1....5nm,increasing
4、withincreasingdistancefromthetarget;thismadeitpossibletoachievesizeselectionofthenanocrystals.Thesurfacemorphologyofthedepositswasstudiedusingscanningelectronmicroscopy.Roomtemperaturephotoluminescenceofthesampleswith514.5nmexcitationwasratherweak.Silicon2pcorephotoelectronspectrashowedtheexis
5、-tenceofasilicondioxidelayeronthesurfaceofthenanoparticles.01999ActaMetallurgicaInc.INTRODUCTIONAseriouslimitationofsilicontechnologyinoptoelectronicsisthatbulkcrystallinesili-condoesnotemitlightduetoitsindirectbandgap.Sincethediscoveryofefficientvisiblelightemissionfromporoussilicon(I),consid
6、erableattentionhasbeenpaidtothestudyofphotoluminescentsiliconnanostructuresofdifferenttypes:nanocrystals,clusters,chain-likestructures,etchedbulksurfaces,superlattices,etc.(2),wherequantumsizeeffectsmodifythebandgapandmakeluminescencepossible.Althoughtheimportanceofquantumconfinementforlumines
7、cenceinsiliconnanostructuresisunderdiscussion(3),luminescenceseemstobeconnectedtosmallsizedstructures,wheretheratioofsurfaceorinterfaceatomstobulkSiat-omsislarge.Thesmalldimensionscanbeachievedbyvariousways:either(a)reductionofthesilico