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1、=ThevanderPauwTechniqueInordertodetermineboththerelaxationtime(meanfreepath)andthecarrierdensity(Fermiparameters),acombinationofaresistivitymeasurementandaHallmeasurementisneeded.WediscussherethevanderPauwtechniquewhich,duetoitsconvenience,iswidelyusedinresearchandindustrytodeterminetheresi
2、stivityofuniformsamples.AsoriginallydevisedbyvanderPauw[5],oneusesanarbitrarilyshaped(butsimplyconnected,i.e.,noholesornonconductingislandsorinclusions),thin-platesamplecontainingfourverysmallcontactsplacedontheperiphery(preferablyinthecorners)oftheplate.AschematicofarectangularvanderPauwco
3、nfigurationisshowninFig.2.(vanderPauw法為了確定兩個弛豫時間(平均自由路徑)和載流子密度(費米參數(shù)),電阻率測量和霍爾測量的組合是必要的。我們在這里討論的vanderPauw法,由于其方便性,被廣泛用于研究和行業(yè)確定均勻樣品的電阻率。最初設(shè)計由vanderPauw法[5],一個使用一個任意形狀的(但簡單的連接,即無孔或不導(dǎo)電的島嶼或夾雜物),薄板樣品中含有四的非常小的接觸放在外圍(最好在角落)的板。一個長方形的vanderPauw配置示意圖如圖2所示。)Theobjectiveoftheresistivitymeasurementistod
4、eterminethesheetresistance.VanderPauwdemonstratedthatthereareactuallytwocharacteristicresistancesand,associatedwiththecorrespondingterminalsshowninFig.2.andarerelatedtothesheetresistancethroughthevanderPauwequation(電阻率測量的目的是確定薄層電阻。vanderPauw證實其實有兩個特性電阻,如圖2所示,與相應(yīng)的終端相關(guān)的。并通過vanderPauw法方程的薄層電阻有
5、關(guān))(2)whichcanbesolvednumericallyfor(這可以解決數(shù)字。).Thebulkelectricalresistivitycanbecalculatedusing(的體積電阻率可以計算使用。).Toobtainthetwocharacteristicresistances,oneappliesadccurrentintocontact1andoutofcontact2andmeasuresthevoltage(要獲得這2個特性電阻,一個適用于直流電流為接觸1和接觸2和測量電壓從接觸4接觸3如圖2所示。)fromcontact4tocontact3as
6、showninFig.2.Next,oneappliesthecurrentintocontact2andoutofcontact3whilemeasuringthevoltage(接下來,一個適用于電流接觸2和接觸3)fromcontact1tocontact4.(同時測量電壓從接觸1接觸4)andarethenTheobjectiveoftheHallmeasurementinthevanderPauwtechniqueistodeterminethesheetcarrierdensity(在vanderPauw法霍爾測量的目的是確定載流子密度)bymeasuringth
7、eHallvoltage(通過測量霍爾電壓).TheHallvoltagemeasurementconsistsofaseriesofvoltagemeasurementswithaconstantcurrent(霍爾電壓測量由一系列的電壓測量與一個恒定電流)andaconstantmagneticfield(和恒定磁場)appliedperpendiculartotheplaneofthesample.Conveniently,thesamesample,shownagaininFig.3,canal