空位缺陷对CdS电子结构和光学性质的影响

305Vol.30,No.520105ACTAOPTICASINICAMay,2010:025322239(2010)0521406207CdS112(1,408003;2,030024)(DFT),,,CdS(),,S,Cd,,,;SCd;;CdS;;O641;O649Adoi:10.3788/AOS20103005.1406VacanciesEffectsonElectronicStructureandOpticalPropertiesofCdSLiChunxia1DangSuihu1HanPeide21CollegeofPhysicsandElectronicEngineering,YangtzeNormalUniversity,Chongqing408003,China2CollegeofMaterialsScienceandEngineering,TaiyuanUniversityofTechnology,Taiyuan,Shanxi030024,ChinaAbstractGeometricalstructureofCdSwithvacancywasoptimizedbyusingdensityfunctionaltheory(DFT)basedonfirst2principleultrasoftpseudopotentialmethod.Optimizedresultsshowedthatthevacancyresultedinlocallatticedistortionandtherelaxationofneighboringatoms.Thenvacancyeffectsonelectronicstructure(energy2bandstructureandelectron2statedensity)ofCdSwereanalyzed.TheresultsrevealedthatSvacancymadethebandgapnarrowerandCdvacancymadeitwider,butCdSwithSandCdvacancyweredirectbandgapsemiconductor.TheopticalpropertiesofCdSwithvacancieswereinvestigated.Theresultsindicatedthatchangesonopticalpropertiesmainlyfocusedonlow2energyregionbecauseofthechangeofelectronicstructureofatomneighborvacancy.Keywordsopticalmaterials;SandCdvacancy;Zincblendstructure;CdScrystal;electronicstructure;firstprinciple:2009205231;:2009207213:(KJ081307,KJ091312)(2003148):(1979),,,,E2mail:[e-mail]1CdS2,,[1,2],,,,CdS[310],HfO2[11]CaO[12],Kazume[13]CdSCu,SCuCdSpCdS,CdS,CdS,CdS35SCd,,S,Cd5:CdS,CdS22.1CdSF43m,a=b=c=0.58304nm[14],Cd(0,0,0)S(0.25,0.25,0.25),CdS,,CdS222,1CdSCd-S0.2525nm,Cd-S10947(0.125,0.125,0.125)S,(0.5,0.5,0.5)Cd222,S,Cd1/16,6.25%1CdSFig.1SupercellofCdS2.2CASTEP[15](DFT)[16],,,,2(GGA2PBE)[17],,,,[18],Cd,SCd:4d105s2,S:3s23p4k,(Ecut)350eV(Brillouin)Monkohorst2Pack[19]K442,,Pulay,210-6eV,BFGS,4,0.5eV/nm;210-5eV;0.1GPa;210-4nm,CdSS,Cd33.1CdSS,Cd1,CdS[14]5.910-3nm,(GGA),(LDA),GGALDA,LDA1,S,Cd,SCdSCd-S,Cd-S,S10-5nm,Cd1.5210-3nmCdS,3,1,,SCd,S2-S(VS)CdSCd2+Cd(VCd),CdSCdS1CdSS,CdTable1ThelatticeconstantofCdSandCdS(S,Cd)vacancyLatticeconstantCdSCdS:SvacancyCdS:CdvacancyCalculatedvalue/mm0.418100.410610.41238Experimentvalue/mm[14]0.41220--------Cd-Saveragebondlength/mm0.255530.255540.25401Bindingenergy/eV-0.23128-0.21458-0.21056,SCd4,SCd7041304,CdS4,,2CdS(110)2(b),2(c)2(a),,,,,2(110)Fig.2Chargedensitycontouroftypical(110)crystalplane3.23.2.1CdSCdSS,Cd,3CdS,Ef3,CdS-11.5-6eV-4.5eV0,3,24CdS(PDOS),34,3CdSFig.3EnergybandstructureanddensityofstatesofCdS4CdSCd(a)CdSS(b)Fig.4PartialdensityofstatesforCd(a),S(b)ofCdS80415:CdSS3pCd5s;Cd4dS3pCdSS3s3pCd5sCdSEg=1.18eV,E.Deligoz[20]1.07eV2.42eV,,Cd5sS3s3p,GGALDAEg[21,22],,CdS3CdS,G3.2.2S,Cd,S,CdCdS,5SCd5,S,Cd,,BrillouinQGSCdS0.8eV,;Cd1.8eV,,,5CdS:S(a)CdS:Cd(b)Fig.5EnergybandstructureofCdS:Svacancy(a)andCdS:Cdvacancy(b)6S[6(a)]CdS(3),06eV,-5eV0,,6(b),6(c)6(d),06eVCd5sS3s,CdsSs-5eV0S3pSS,,S3s-5eV0,3p,S7Cd[7(a)][7(b),7(c)7(d)]S,,,p,02.5eV6CdS:SFig.6DensityofstatesforCdS:Svacancy904130,S3p,2.57.5eV,S3pCd5s,S3pCd5s,Cd5s-2.55eVS3p,CdCd5s,7CdS:CdFig.7DensityofstatesforCdS:Cdvacancy3.3,()=1()+i2(),,,2():2()=42m22V,CBZd3K2(2)3eMCV(K)2EC(K)-EV(K)-…h,C,V,BZ,K,eMCV(K)2,,EC(K),EV(K)1()Kramers2Kronig1()2(),R(),I(),(),[23],8CdSS,CdCdSBieniewsk[24]S,Cd,S,CdCdS8(a),CdSS,Cd3,CdS1.2,5.711.7eV,ZhouHuang[25]1.2eV,S3p;5.7eVS3pCd5s;11.7eVCd4dS3p,S,Cd(E7.0eV)CdS,S1.8eV,SCd,,S3pCd5sCd0.6eVCdS,S3p,Cd8(b),,CdSS,Cd8(c),CdSS,CdCdS1.18eV,,,CdSS,Cd,S,Cd,Cd,SCdS,1.35eV,S,S,Cd5s01415:CdS;CdCdS3p8(d),3,8CdSSCd(a),(b),(c),(d)Fig.8(a)imaginaryparts,realparts(b)ofdielectricfunction,absorptionspectrum(c),reflectionspectrum(d)ofCdS,CdS:Svacancy,CdS:Cdvacancy4,CdSS,Cd,S,Cd,;S,Cd,S;Cd,CdS;S,CdCdS,,1ShenJie,MaGuohong,ZhangZhuangjianetal..Researchontwo2photonabsorptionenhancementofCdSinone2dimensionalphotonicbandgapstructures[J].ActaOpticaSinica,2005,25(8):11211125,,.[J].,2005,25(8):112111252P.P.Sahay,R.K.Nath,S.Tewari.OpticalpropertiesofthermallyevaporatedCdSthinfilms[J].Cryst.Res.Technol.,2007,42(3):2752803DangSuihu,LiChunxia,HanPeide.First2principlescalculationofCdSelectronicstructuredopedewithMgandCu[J].ActaPhysicaSinica,2009,58(6):41374143,,.Mg,CuCdS[J].,2009,58(6):413741434M.Rohlfing,P.Krger,J.Pollmann.QuasiparticlebandstructureofCdS[J].Phys.Rev.Lett.,1995,75:348934925D.Vogel,P.Krger,J.Pollmann.Structuralandelectronicpropertiesofgroup2IIInitrides[J].Phys.Rev.B,1997,55:12836128396L.C.LewYanVoon,M.Willatzen,M.Cardonaetal..Termslinearinkinthebandstructureofwurtzite2typesemiconductors[J].Phys.Rev.B,1996,53:10703107147U.V.Desnica,I.D.Desnica2Frankovi’c,R.Magerleetal..CompensatingdefectsandelectricalactivationofdonorsinCdS[J].PhysicaB:CondensedMatter,1999,273:9079108XiongZhihua,RaoJianping,JiangFengyi.DensityfunctionalcalculationsofelectionicstructureandopticalpropertiesonMgandni2dopedCdS[J].ActaOpticaSinica,2007,27(12):22252228,,.CdSMgNi[J].,2007,27(12):222522289XuRonghui,WangYongxian,JiaGuangqiangetal..SynthesisofzincblendeCdSnanocrystallitesusing32Mercaptopropionicacidasprecursorbyhydrothermalmethod[J].ChemicalJ.ChineseUniversities,2007,28(2):217219,,.CdS[J].,2007,28(2):21721910DingLiyun,JiangDesheng,HuangJun.Photoref