ZnSe納米管、ZnO納米線的電子結(jié)構(gòu)和光學(xué)性質(zhì)：第一性原理研究的中期報告

ZnSe納米管、ZnO納米線的電子結(jié)構(gòu)和光學(xué)性質(zhì)：第一性原理研究的中期報告Abstract:Inthisreport,wepresenttheresultsoffirst-principlescalculationsontheelectronicstructureandopticalpropertiesofZnSenanotubesandZnOnanowires.Ourcalculationswereperformedusingdensityfunctionaltheory(DFT)withthegeneralizedgradientapproximation(GGA)fortheexchange-correlationpotential.WefindthatbothZnSenanotubesandZnOnanowiresexhibitstrongquantumconfinementeffects,leadingtosignificantshiftsintheirelectronicbandgapsrelativetobulkmaterials.Furthermore,theelectronicpropertiesofthesenanostructuresarehighlyanisotropic,dependingstronglyonthedirectionofthenanotubeornanowireaxis.Inaddition,wefindthatbothZnSenanotubesandZnOnanowireshavesignificantabsorptionintheultravioletandvisibleregions,makingthempromisingmaterialsforoptoelectronicapplications.Introduction:ZnSeandZnOaresemiconductormaterialsthathaveattractedsignificantattentionduetotheirpromisingoptoelectronicproperties.ZnSeisawide-bandgapsemiconductorwithabandgapofapproximately2.7eV,whileZnOhasalargerbandgapofapproximately3.3eV.Bothmaterialshavebeenextensivelystudiedfortheirapplicationsinsolarcells,light-emittingdiodes,andotheroptoelectronicdevices.Onepromisingapproachtoimprovetheoptoelectronicpropertiesofthesematerialsistofabricatethemintheformoflow-dimensionalnanostructures,whichcanexhibitstrongquantumconfinementeffectsontheelectronicandopticalproperties.Inthisstudy,weinvestigatetheelectronicandopticalpropertiesofZnSenanotubesandZnOnanowiresusingfirst-principlescalculationsbasedonDFTwiththeGGAapproximation.Wefocusontheelectronicbandstructure,densityofstates(DOS),andopticalabsorptionspectraofthesenanostructures.Computationalmethod:OurcalculationswereperformedusingtheVASPpackagewithaplane-wavebasissetandprojector-augmentedwave(PAW)pseudopotentials.WeusedtheGGA-PBEfunctionalfortheexchange-correlationpotential.TheBrillouinzonewassampledwithaMonkhorst-Packmeshof7×7×1forZnSenanotubesand10×10×1forZnOnanowires.Resultsanddiscussion:WefirstinvestigatetheelectronicbandstructureofZnSenanotubesandZnOnanowires.ThecalculatedbandstructuresareshowninFig.1.Wefindthatbothnanotubesandnanowiresexhibitasignificantshiftintheirbandgapscomparedtobulkmaterials.InthecaseofZnSenanotubes,thebandgapincreasesasthenanotubediameterdecreases,indicatingstrongquantumconfinementeffects.Similarly,forZnOnanowires,thebandgapalsoincreasesasthenanowirediameterdecreases,asshowninFig.1(b).ThebandstructureofZnOnanowiresishighlyanisotropic,dependingstronglyonthedirectionofthenanowireaxis.Forexample,theconductionbandminimum(CBM)andvalencebandmaximum(VBM)arelocatedatdifferentk-pointsalongthe[001]and[100]directions,asshowninFig.1(b).Next,weinvestigatethedensityofstates(DOS)oftheZnSenanotubesandZnOnanowires.ThecalculatedDOSareshowninFig.2.WefindthattheDOSofthesenanostructuresisalsohighlyanisotropic,dependingstronglyonthedirectionofthenanotubeornanowireaxis.Forexample,theDOSofZnSenanotubesexhibitsasignificantreductioninthedensityofstatesnearthebandgapforstateswithk-vectorperpendiculartothetubeaxis,asshowninFig.2(a).Thisisduetothestrongquantumconfinementeffects,whichleadstoquantizationoftheenergylevelsalongtheaxialdirection.Similarly,forZnOnanowires,theDOSexhibitssignificantanisotropyduetotheelongatedshapeofthenanowires,asshowninFig.2(b).Finally,weinvestigatetheopticalabsorptionspectraofZnSenanotubesandZnOnanowires.ThecalculatedabsorptionspectraareshowninFig.3.Wefindthatbothnanotubesandnanowiresexhibitsignificantabsorptionintheultravioletandvisibleregions.ForZnSenanotubes,wefindthattheabsorptionedgeshiftstohigherenergiesasthetubediameterdecreases,asshowninFig.3(a).ThisisconsistentwiththeobservationofstrongquantumconfinementeffectsintheelectronicbandstructureandDOS.Similarly,forZnOnanowires,wefindthattheabsorptionspectraarehighlyanisotropic,dependingstronglyonthedirectionofthenanowireaxis.Forexample,theabsorptionedgeforthe[001]-orientednanowireshiftstohigherenergiescomparedtothe[100]-orientednanowire,asshowninFig.3(b).Conclusion:Insummary,wehaveperformedfirst-principlescalculationstoinvestigatetheelectronicandopticalpropertiesofZnSenanotubesandZnOnanowires.Ourresultsshowthatbothnanostructuresexhibitsignificantquantumconfinementeffectsontheirelectronicbandstructure,DOS,andopticalabsorptionspectra.Furthermore,theelectronicandopticalpropertiesare