纳米发电机-nanogenerator

PotentialofNanogeneratorAdv.FuncMater.,2008(18)1-15.OutlineProofofprincipleofZnOnanowirespowergenerationtriggeredbyanAFMtip(Wangetal,Science2006)Nanoscalegenerator(Wangetal,Science2007)andpotentialapplicationsControversyregardingthepowergenerationmechanism-n-typeZnOnanowiregrownonAl2O3substrate-generatingelectricitybydeformingNWwithAFMtipAlignedZnONWsgrownonAl2O3Science,312(2006)242-246.OutputvoltagefromalignedZnOnanowiresScience,312(2006)242-246.-Sharpoutputvoltage-PeakcorrespondstomaximumdeflectionofNWDischargeoccurswhentipcontactswithcompressedsideElectronaffinityofZnO:4.5eVWorkfunctionofAg:4.2eVWorkfunctionofPt:6.1eVVL=Vm-VSMechanismofZnONanogeneratorTransportisgovernedbymetal-semiconductorSchottkybarrierforPZZnONWScience,312(2006)242-246.ThedifferenceofOhmicandSchottky-NooutputsignalformAl-In-coatedSitip(ohmiccontactwithZnONW)Adv.FuncMater.,2008(18)1-15.ZnONanogeneratorstructureZig-ZagPtcoatedSielectrodeplaystheroleofanarrayofAFMtipsDeviceembeddedinapolymerprotectinglayerSchematicviewandSEMimagesofthenanogeneratorNanogeneratorimmersedinanultrasonicbathDirect-CurrentNanogeneratorDrivenbyUltrasonicWavesWangetalScience2007,316p102PowergenerationmechanismsSchematicviewofthedischargingmechanismsEquivalentcircuitSEMcross-sectionviewofthenanogeneratorPowergenerationDevicesize:2mm2Powergenerated:1pWCurrent,biasandresistanceofthegeneratorasafunctionoftimeCurrentgeneratedasafunctionoftimeEstimatedpowerperNW:1-4fWPowerdensityafteroptimization(109activeNWpercm2):1-4µW/cm2Applications:transistorsandLEDAgeneratorproviding10to50nWisrequiredtopowersuchacrossNWFETa.GatedependentIVcharacteristicsofacrossNWFETb.SEMimageofacrossNWjunction,scalebaris1µmHuangY.etal,Science2001284p1313Currentandemissionintensityofacarbonnanotubesfilmasafunctionofgatevoltage(Vdwas1V)ChenJ.etal,Science2005,310,p1171µWpowerlevelneededforaCNTLEDApplications:wirelesssensorsEnergyHarvestingFromHumanandMachineMotionforWirelessElectronicDevicesMitchesonetal,proceedingsoftheIEEE,Vol96,N.9,2008Sensornodes(motes)applications:•Structuralmonitoringofbuildings•Militarytracking•Personaltrackingandrecordsystem(Health)Poweringmotes:•Sensor12µWquiescentpower•ADC1µWfor8bitsampling•Transmitter0.65µWfor1kbpsMEMSaccelerometersalreadyusedforvariousapplicationsBasicwirelesssensorarrangementPiezoelectrictransducerforenergyharvestingMitchesonetal,proceedingsoftheIEEE,Vol96,N.9,2008Test:608Hzresonantoperation1gacceleration0.89VACpeak–peakgenerated2.16µWpoweroutputFangHBetal,MicroelectronicsJournal37(2006)1280–1284ElectrostatictransducerforenergyharvestingAssembledJFETGenerates100µW/cm3fromavibrationsourceof2.25m/s2at120Hzelectret:permanentchargeburiedinthedielectriclayerSEMimagesofthegeneratorintegratedwithaFETschematicviewofaconstantchargeelectrostatictransducerMitchesonetal,proceedingsoftheIEEE,Vol96,N.9,2008S.Roundy,P.K.Wright,andJ.M.Rabaey,EnergyScavengingforWirelessSensorNetworks,1sted.Boston,MA:KluwerAcademic,2003.ArgumentagainstWangAdvancedMaterials20,4021(2008)OriginofthepiezoelectricvoltageStraindisplacivechargeDisplacivechargevoltageForidealinsulator:GenerationofpiezoelectricchargecanbeconsideredequivalenttothegenerationofapotentialGoseleetal.Adv.Mater.20,4021(2008)ModelofZnOPiezoelectricGeneratorForsemiconductingZnO:Goseleetal.Adv.Mater.20,4021(2008)LoadtimeconstantRL=500MΩCL5pFτL~1sIntrinsictimeconstantτL~10-2psRectificationofaSchottkydiodeGoseleetal.Adv.Mater.20,4021(2008)V~kBT/q~25meVquasi-ohmicTogetrectification:VVbi~0.3-0.8VWang’sdata:output~10mVVoltageargumentWangetal’spreviousopinion:Piezoelectricvoltageis0.3V(calculation)Highcontactresistanceleadstolowoutputof10mV(experiment)GoseleetalruledoutthepossibilityofahighcontactresistanceLoadresistoris500MΩnowayforacontactresistancehigherthan500MΩWangetal.NanoLett.7,2499(2007)Goseleetal.Adv.Mater.20,4021(2008)VoltageargumentWangetal’snewmodel:10mV:differenceofFermilevels0.3V:realSchottkydiodedrivingvoltageIfWang’snewmodelistrue,0.3Visstillasmallvoltagetorectifythepiezoelectricsignal…Wangetal.Adv.Mater.20,1(2008)Wangetal.NanoLett.8,328(2008)UnknownsbehindthenanogeneratorThereisalotofmoreworktobedone…I.TimeconstantII.RectificationThenanogeneratormodel?