微波辅助化学气相沉积法合成硅纳米线.

SiliconNanowiresSynthesizedviaMicrowave-AssistedChemicalVaporDeposition组员：蒋振龙王美玲孙建会孙瑞瑞董思宁殷月伟第十七组主要内容IntroductionExperimentExperimentalResultsDiscussionApplicationofSiNWsIntroductionofsiliconnanowiresSiliconnanowireshaveuniqueelectronicandopticalproperties,itcanbewildlyusedinsensorandelectronicindustries.Thesynthesisofsiliconnanowiresarehigh-costorhigh-energyconditions.合成硅纳米线的几种方法激光烧蚀：海绵状的SiNWs水热法：（20nm）分子束取向附生法(MBE）金属催化化学腐蚀方法（单晶性好、轴向可控）AAO模板法热物理蒸发法SiNWsbyLaserAblationTEMimageofas-grownSiNWsbythethermalphysicalevaporation,AnewmethodtosynthesissiliconnanowiresThisisnotanewmethod.Microwavesourceshavepreviouslybeenemployedinthesynthesisofcarbonnanotubes.However,tothebestofourknowledge,applicationofamicrowavefieldhasnotbeenreportedonthegrowthofSiNWsatambientconditionspriortothiswork.ExperimentconditionAnunmodified1100W,2.45GHzEmersondomesticmicrowaveovenTrichlorosilane(99%)fromAldrichSubstratematerials:（i）1×4cmITO-coatedslidesfromHartfordGlassCo.(surfaceresistivity≈15Ω/□)thatwerethinneddownto1mmthicknessbymechanicalpolishing(substrateA).（ii）1mmthickITO-coatedglassslidesfromAldrich(surfaceresistivity≈15Ω/□)thatwerecutintorectanglesof1×4cm(substrateB).ThedifferenceoftwosubstratesSubstrateA:SubstrateB:Experimentsubstratesdegreased（acetone）Rinse(2-propanol；deionizedwater)dryDipping（SnO2colloidalsolution）withdrawndrythermaltreatment(300℃，3h）microwavereactionvialirradiated(0.5min)testSchemeofdepositionScheme1.Schemeofdeposition.HSiCl3(g)+ITO(S)+µwaveradiation→Si(ads)+ITO(S)+HCl(g)+Cl2(g)Results(SEM)Fig.1.SEMimagesofstructuresobtainedondifferentregionsonaconductivesubstrate,substrateA:(a–b)heatedsubstrate(withanaveragelengthof30andaveragediameterof3)(d–f)heatedsubstrate(averagelengthof30)(g--h)unheatedsubstrateResults(SEM)Fig.2.SEMimagesofSiNWs(30–45nmdiameter)interspersedwithSicrystallites(0.3µmdiameter)depositedonconductiveITOsurface(substrateB).Thevariouspicturesaredifferentmagnificationsofthesameregionofthesubstrate.Results(SEM)Fig.3.SEMimagesofporousSi/agglomeratedSinanoparticlesobservedatedgesofdepositionarea:(a)substrateAand(b)substrateB.Results(EDSanalysis)Fig.4.RepresentativeEDSspectraofthevariousmorphologiesobserved,(a)EDSspectrumofSiNWbundle,(b)EDSspectrumofSicrystalliteandporousmatrix,and(c)EDSspectrumofdenseSilayer.Results(XPSanalysis)Fig.5.XPSspectrumofSiNWbundles[oxygen:1002eV(KL1L23),982eV(KL23L23),536eV(1S);carbon:288eV(1S);silicon:153eV(2S),105eV(2P1),101eV(2P3),28eV(2S)].ConclusionsSEManalysisoftheunmodifiedsubstrateAshowedapredominantlycolumnarorientationofitsconductivelayer,whereassubstrateB'sconductivelayerwasfoundtobemadeupofcompactmicrospheres.SubstratesofdifferentITOmicrostructurewerefoundtoresultinSiwiresofdifferentmorphologies.Chemicalanalysisshowedthestructuresobtainedtobeofhighpuritysilicon,comparabletoconventionalSiNWgrowthtechniquescurrentlyinuse.DiscussionAdvantages:Thismethodisasimplebuteffectivesynthesisofhigh-puritySiNWsusinginexpensiveequipment.limitations:limitedcontrolovertheoverallstructureuniformityandcoverageduetothemultimodenatureofthemicrowavefieldandnonuniformSnO2nanoparticlesurfacecoverage.FurtherstudiesFurtherstudiesareinprogresstoimproveupontheseby:useofasingle-modemicrowavesourceforamoreuniformelectricfielduseofalowerenergyprecursor,e.g.,SiH4,thatwouldincreasecoveragepercentageandachieveevensmallerdiametersuseofsurfactantsinnano-SnO2patterningoftheITOsurfaceforgreaterdispersion硅纳米线在纳米电子器件上的应用场效应晶体管(FET)单电子存储元件无源二极管有源双极晶体管传感器单电子探测器双方向电子泵双重门电路单电子探测器SEM双重门电路SEM硅纳米线在太阳能电池上的应用硅纳米太阳能电池Anewmaterialconsistingofclustersofnanocrystallinesiliconembeddedinanamorphousmatrixholdspromiseforanimprovedgenerationofsolarcellsthataremorestableinsunlightthantoday’stechnology.Source:2003INquiry2003硅纳米线在检测PH上的应用,Source:Cui,Y.;Wei,Q.;Park,H.;Lieber,C.M.Science2001,293,SiliconnanowiresthatdetectpH硅纳米线可实现金属-半导体纳米接触Short（0.6nm）wiresarefullymetallizedbymetal-inducedgapstatesresultinginfiniteconductanceSource:UziLandman,1RobertN.Barnett,1AndrewG.Scherbakov,1andPhaedonAvouris2VOLUME85,NUMBER9PHYSICALREVIEWLETTERS28AUGUST2000硅纳米线应用的最新进展madeinthelabofHarvardUniversitychemistCharlesLieberThis300-nanometer-widesiliconwire(left)generateselectricityfromsunlight.Butarraysofmicroscopicwirescouldchangetheeconomicsofsolarpowerbyenablingsolarcellsbuiltfromcheapmaterialssuchaslow-gradesiliconorevenironoxide--rust.Anumberofsuchcheapmaterialsabsorblightandgenerateelectrons,butdefectsinthematerialsusuallytraptheelectronsbeforetheycanbecollected.Microscopicwires,though,canbemadethinenoughtoallowelectronstoslipouteasilyandgeneratecurrent,evenifthematerialhasdefects.Andthewirescanbelongenoughtoabsorbplentyofphotonsfromsunlighthittingthematanangle.Suchnanowiresolarcellswouldinitiallybeusefulintinysensors,orinrobotswhoseelectronicsmightneedbuilt-inpower.Source:January/February2008IssueofTechnologyReview.硅纳米线的应用最新进展Tomakesolarpanels,themicroscopicwirescouldbegrownindensearrays.Theimageshowsacrosssectionofasilicon-wirearrayfabricatedinthelabsofchemistNathanLewisand。physicistHarryAtwateratCal