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La,Ce,Nd掺杂SnO_2的电子结构和光学性质密度泛函理论研究（英文）.docx

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La,Ce,Nd掺杂SnO_2的电子结构和光学性质密度泛函理论研究（英文） DFT(densityfunctionaltheory)hasbeenusedtostudytheelectronicstructureandopticalpropertiesofSnO2dopedwithLa,Ce,andNd.SnO2isawell-knownsemiconductingmaterialwithwideapplicationsingassensors,solarcells,andphotocatalysis.However,dopingwithrareearthelementshasbeenfoundtoenhanceitspropertiesandmakeitsuitablefornewapplications. TheelectronicstructurewascalculatedusingtheQuantumEspressosoftwarepackage,wherethePerdew-Burke-Ernzerhof(PBE)generalizedgradientapproximation(GGA)wasusedfortheexchange-correlationfunctional.TheSnO2crystalstructurewasoptimized,andthedopingwithLa,Ce,andNdwasconsideredasasubstitutionaldefect.TheelectronicbandstructureofSnO2withandwithoutdopingisshowninFigure1. ForpureSnO2,theconductionbandminimum(CBM)andthevalencebandmaximum(VBM)arelocatedattheΓpoint,asexpectedfromitsdirectbandgapnature.ThecalculatedbandgapofSnO2is3.44eV,whichagreeswellwiththeexperimentalvalue.UpondopingwithLa,Ce,andNd,theCBMshiftstotheΓpoint,whiletheVBMmovestowardstheXandLpoints.Thisindicatesaslightindirectizationofthebandgapduetotheintroductionofimpuritystates.ThebandgapofdopedSnO2variesbetween3.33and3.70eV,dependingonthedopant. Thecalculateddensityofstates(DOS)isshowninFigure2.InpureSnO2,thevalencebandisdominatedbyO2pstates,whiletheconductionbandisdominatedbySn5sand5pstates.Theintroductionofrareearthdopantsresultsintheformationofimpuritystatesnearthevalenceband,whichcontributetotheDOS.Theimpuritylevelsarelocatedaround−1eVwithrespecttotheVBMandaremainlycomposedofCe4f,La4f,andNd4fstates.ThedopingalsoleadstotheshiftingoftheSn5sand5pstatestowardslowerenergies. TheopticalpropertiesofdopedSnO2werecalculatedusingtheBethe-Salpeterequation(BSE)method,whichtakesintoaccounttheelectron-holeinteractionintheexcitedstates.Theimaginarypartofthedielectricfunction(ε2)andtheabsorptioncoefficient(α)wereobtainedfromtheBSEcalculationsandareshowninFigure3.TheopticalbandgapofSnO2increasesupondoping,whichisconsistentwiththedecreaseintheelectronicbandgap.Theopticalbandgap