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1、PHYSICALREVIEWBVOLUME61,NUMBER2015MAY2000-IITheoreticalSTMsignaturesandtransportpropertiesofnativedefectsincarbonnanotubesDanielOrlikowski,MarcoBuongiornoNardelli,J.Bernholc,andChristopherRolandDepartmentofPhysics,NorthCarolinaStateUniversity,Raleigh,NorthCarolina27695~Received29Novembe
2、r1999!WehaveinvestigatedtheoreticallytheSTMimagesandconductancesignaturesofdefectivecarbonnano-tubes.Thedefectsconsideredarethosethatformonnanotubesundertension,bothintheabsenceandpresenceofadditionalcarbonatoms.ThemostprominentfeaturesobservedintheSTMimagesareasetofbrightrings,whosepos
3、itionscorrelatewiththelocationofthepentagonswithinthedefect.Thesefeaturesareuseful,astheyenablethereadyidenti?cationofmanyofthedefects.Bycontrast,mostofthedefectshaveonlyarelativelymodesteffectonthetransportpropertiesofthenanotubes.Whilethereisageneraldecreaseintheconductanceofthenanotu
4、beduetoscatteringeffects,thereappearstobenouniquefeaturethatcanbeassociatedwithanyofthedefectsinvestigated.Thisunfortunatelyprecludestheuseoftransportmeasurementsasameansofdefectidenti?cation.TheSTMimagesandconductancesofnanotubeheterojunctions,aswellastubesunderdifferentbiasvoltages,ha
5、vealsobeenexplored.I.INTRODUCTIONmationas?rstproposedforC60~Ref.15!#,whichleadstotheformationofa~5-7-7-5!defect.DependingonthehelicityofItisinterestingthatcarbonnanotubescanbeeithermetalsthenanotube,therateofstrainandtemperature,thisdefect1±4orsemiconductors,dependingontheirhelicity.Thi
6、sre-canleadtoeitherductileorbrittlebehavior,sothatitdomi-markablepropertysuggeststhatitmaybepossibleinthe16natesthemechanicalresponseofpristinenanotubes.Thefuturetoconstructanall-carbonnanotube-basedmicroelec-secondclassofdefectsisassociatedwiththeactionofad-tronics.Toexplorethisexcitin
7、gpossibility,therehasbeenadimersonstrainednanotubes.Suchaddimersarelikelytobe2±1011±14presentonas-grownnanotubes,ortheymaybeplacedontheconsiderableamountoftheoreticalandexperimentalresearchinvestigatingtheelectronicpropertiesofnanotubes.tubeswitheitheranSTMtiporviadirectdeposit