掺杂ZnO稀磁半导体磁性的第一性原理计算博士论.doc

华中科技大学博士学位论文掺杂ZnO稀磁半导体磁性的第一性原理计算姓名：梁培申请学位级别：博士专业：微电子学与固体电子学指导教师：江建军20090520ZnOZnOZnO-251439 K-VZnVOVZn3dZnO-ZnOZnOZnOZnOZnOVZnZnOVOI-ZnOCo-AlZnOAlAl-2pCo-3dp-dFe-AlZnOFeZnOAlAlFeZnOAl-2pFe-3dRKKYCu-N-ZnONN-2p Cu-3dO-2pCu-3d4sN-Mn-N(Tc )ZnOZnOIIAbstractSpintronics seek to exploit both spin and charge attributes of information carriers to transfer, process and store data, which has become a focused interdisciplinary field involving electronics, physics, materials science and other disciplines. As a crucial material in this field, ZnO based diluted magnetic semiconductor has received a great deal of attention. Zinc Oxide semiconductors base materials with high doping concentration and the 3-d band of doped ions could generate strong ferromagnetic coupling interaction through the intrinsic defect states of the base material, which led to Zinc Oxide become the most emerging hotspot in this field. Two key scientific problems in spintronics to both look for magnetic semiconductors with high Curie temperature and analyse the origin and mechanism of magnetism in these semiconductors could be sought for solution. Therefore, the electronic structure of diluted magnetic semiconductors through first-principle calculation was firstly carried out, and the results were utilized to analyze and explain the origin of ferromagnetism. Base on the result achieved in first-principles, a new coupling integration algorithm to calculate the Curie temperature of ZnO DMS and discusse the controlling method of it was put forward. Then the effects of interaction mechanism of different single-doping and co-doping diluted magnetic semiconductor systems were extensively discussed in detail.Firstly, the electronic structure of ZnO-based diluted magnetic semiconductor was calculated by first-principles according to the Pseudopotential Plane Wave method (PP-PW) and Full Potential Augmented Plane Wave method (FP-LAPW). The coupling interaction between transition metals in oxide magnetic semiconductors were analysed from perspectives of energy bands theory, which described the origin of magnetism about diluted magnetic semiconductor. Furthermore, the coupling computations of first-principles and Monte Carlo method were developed by calculation code in our study, which was used to estimate Curie temperature of several diluted magnetic semiconductor systems and studied the further controlling method of it.Secondly, the electronic structure of carbon doped ZnO was calculated by the fullIIIpotential linearized augmented plane wave method (FP-LAPW) with general gradual approximation (GGA). The results showed that the single carbon doping led to ferromagnetism both in Oxygen position and in interstitial position, and they both result in half-metallic property, which theoretically had a high rate of spin-polarization. The Curie temperature of carbon doped ZnO was also predicted through a combination of first-principles and Monte Carlo coupling integrated calculation method. The results showed that the Curie temperature of carbon doped ZnO system changed ranges from 251 to 439 K as the concentration variation. As a result, room-temperature ferromagnetism of carbon doped ZnO could be derived in proper preparing conditions.With full potential linearized augmented plane wave method (FP-LAPW) and Coulomb potential amendment, electronic structure and magnetism of neodymium doped ZnO, the neodymium doped ZnO with an oxygen vacancy (VO ) and neodymium doped ZnO a Zinc vacancy ( VZn ) were calculated, respectively. The results indicated that neodymium doped ZnO with VZn defects might have high Curie temperature, while those without intrinsic defects are paramagnetic, and those with VO defects get weak anti-ferromagnetism. Furthermore, bound magnetic polaron theory can be employed to explain the origin of magnetism in systems with Zn vacancy.Finally, after the single doped ZnO was presented, the effect of metal-transition metal co-doped ZnO systems were extensively examined to described the mechanism of the inter-exchange and the origin of magnetism. Hence, Al-Co co-doped ZnO systems were also investigated; the calculated results showed that by co-doping with Al, the systems were transferred from anti-ferromagnetism to ferromagnetism. The origin of ferromagnetism mainly attributes to the interaction between Al-2p electron and nearest Co-3d electron modulated by extra electrons, and the inter-exchange effect can be explained by p-d exchange model. Al-Fe co-doped ZnO system is also investigated, and the results indicate that by co-doping with Al the system is transferred from anti-ferromagnetism to ferromagnetism. But the Al-2p and Fe-3d electrons do not have interaction with each other, and the origin of ferromagnetism can be explained by long range Ruderman-Kittel-Kasuya- Yoshida (RKKY) exchange interaction.In order to describe the different interaction mechanism of DMS, the influence ofIVmetal-non metal co-doping system were analyzed. Hence, the Cu-N co-doped ZnO systems were also investigated. By introducing nitrogen, the interaction between N-2p and Cu-3d electrons stabilize the magnetism of the system. In the meanwhile, both before and after co-doping, the VBM is always occupied by O-2p electrons, while in conduction band states are mostly occupied by Cu-3d and 4s electrons. Carrier mediated model was employed to explain the origin of magnetism. As nitrogen co-doping improved the density of charge carriers in system, interaction mediated by free carriers between magnetic ions led to ferromagnetic order as a whole.To obtain the Curie temperature controling method and the interaction mechanism, metal-nonmetal co-doped systems were also studied by co-doping nitrogen the Manganese doped system showed stable ferromagnetism. Based on Heisenberg model and mean field theory, with Monte Carlo and first-principles method, we predict that room-temperature ferromagnetism can achieve in ideal conditions theoretically.As a result, through the combination of first-principles and Monte Carlo method, single-doped and co-doped systems were extensively discussed. The results showed that different doped system has different inter-exchange mechanism. Our calculation can explain the origin of magnetism in some doped systems and the way to increase the Curie temperature. All these can give a guide for the preparation techniques of ZnO diluted magnetic semiconductors.Key words: spintronics, ZnO, diluted magnetic semiconductor, co-doping methodology, First-principles, electronic structure, Monte Carlo, Curie temperatureVAPWAugmented Plane WavesASAAtomic Sphere ApproximationBZBrillouin ZoneDFPTDensity Functional Perturbation TheoryDFTDensity Functional TheoryFFTFast Fourier TransformFPFull-PotentialGGAGeneralized Gradient ApproximationGTOGaussian-Type OrbitalHFHartree-Fock-HOMOHighest Occupied Molecular OrbitalKSKohn-Sham-LAPWLinearised Augmented Plane WaveLCAOLinear Combination Of Atomic OrbitalLDALocal Density ApproximationLMTOLinearised Muffin Tin Orbital-MTLSDALocal Spin Density ApproximationLUMOLowest Unoccupied Molecular OrbitalMCMonte CarloMKMonkhorst-PackMPMOMolecular OrbitalMTOMuffin-Tin OrbitalMuffin-TinNLCCNon-Linear Core CorrectionsOPWOrthogonalized Plane WavesPAWProjected Augmented WavesPBCPeriodic Boundary ConditionsVIPSPseudopotentialPWPlane WavesQMDQuantum Molecular DynamicsQM-MMQuantum Mechanics-Molecular Mechanics-RPARandom Phase ApproximationSCFSelf-Consistent FieldSTOSlater-Type OrbitalTBTight-BindingUSUltrasoftVMCVariational Monte CarloXCExchange-CorrelationDMSDiluted Magnetic SemiconductorsTCCurie TemperatureFM/AFMFerro-magnetism/anti-ferromagnetism/VII_ _(“”)11.11.1.1SpintronicsSpin Electronics119(e=1.602210-19)202021.1.23(Diluted MagneticSemiconductors,)(Semi-magnetic Semiconductors)DMSSMSCDMS-4-6MnMn2+Mn2+3d5FeCo11-11-1(a)(b)() (c)71.1.3 ZnO1997ZnO8ZnOZnOZnOZnOp63mc5.67 g/cm3a=3.249 c=5.206 ZnO1-39, 10ZnO3.37eV2p4sZnOnZnO60 meVZnSe(22 meV)ZnS(40 meV)GaN (25 meV)ZnOZnOGaN21-3 ZnO10ZnOZnO1.2dfBlombergen-RowlandRuderman-Kittel-Kasuya -Yoshida11-141.2.13H ex = J ij S i Sj(1-1)ijJijJijJijJijd1.2.2Jij- -TMdGKA151.2.3ZenerAndersonHasegawaII-VI(HgSeHgS )Fe+2+3MnZnOCdGeP2Mn2+Mn+1.2.4 Blombergen-RowlandBlombergen-Rowland(BR)p1-5NdN+1N dBRZnOBR4BKC12ADK1-51.2.5 RKKYRuderman-Kittel-Kasuya-Yoshida(RKKY)13, 14Jk ,k RudermannR = Rj RiH ex = 2 J k ,k .e i (k k )Rl k ,k SLRKKYH= (Ns d )(rR0ikittelJ ij=( )k 3(N)2F F02Hex S L .Skk LR ) S i . SJijF3 (2k F R)Jij Fermi(1-2)Skk s-d(1-3)(1-4)(F ) s-d N0 R 0) F3 (x ) = cos(x ) / x 3 RKKYx (5RKKYRKKY1.2.6(BMP, bound magnetopolaron)EuO-16Coey17(BMP)ZnO(OZn)()1-761-1BMP(1)(2)n nc(3)(4)18TcZnO1.37ZnO(LDA)(LDA)(LSDA)LDA(LDA)(GGA)LDAPei19 NiZnO(GGA)NiGGA+URebecca20Mufintin(LMTO)(LCAO)1.3.1ZnOZnOCo Fe Mn1-2 Detil7MnC ZnO81-2ZenerMn1Sato21,22-V CrMn Co Ni(LDA)(GGA)SatoLDASato2350%Tc1-3ZnOZnSZnSe ZnTe(TM)5%25%0MnV CrFeCoNiZnO91-3231.3.2(LM)ZnO24-26(TM)ZnOShen24(LM)ZnOLMTM()2p3d2p-3d3d3d4f2pShenGGAPAWNZnOShenNZnOp-pBe-N10ZnOPan26,27CZnOPLDCZnOCZnO400 KCZnOOZnPanZn-Cp-pCO-2pPanC N1.4ZnO(PLD)ZnO1.4.1 MnZnOMnZnO28-313234MnMnZnOFukumura35Al2O3Zn0.64Mn0.36O10-5 TorrXRDMnSQUID13 K-MnZnO13%36Mn35%(31, 3360037112.2%30%MnZnO38, 39MnZnOMn3923.2%30%Mn4.8 B0.02 BMn10% 20%0.710.25emu.cm-35%Mn1.4.2 CoZnOCoZnOUeda28Al2O3Zn1-xCoxO(x=0.050.25)XRDCo1-41-53506002410-5 Torr1%Al(Zn0.95Co0.05O Zn0.85Co0.15O)1.82.0 B1.210182.91020 cm-3.10%CoZnOPLD40-474849351-4 Zn0.85Co0.05OXRD1-5(Zn, Co)Od(002)CoCoZnO10%34Prellier43PLDCoZnO10%Park5012%Co12Lee4925%Co3O4Jin29Co20%Ueda28Kim42PLDCo50%25%1.4.3CoMnZnOV29, 51 Cr28, 52 Fe29Ni28, 29, 52, 53ZnOVZnO0.5 BPLD Al2O3NiZnO300 KVenkatesan52FeZnO0.8 B28, 29, 54FeZnOYe55CuZnOCuCuCuZnOCuZnOCuZnOCu-3dO-2pCuZnOCuZnOZhou56PLDCZnOCGeNeZnOCZnOZnO1.5(50371029 50771047)(NCET04-0702)(132005ABB002)DFTZnOLAPWLAPWAl-FeAl-CoAlMn-N Cu-NLAPW1-6141-615257ZnO2.12.1.158 59 19298016Hartree-Fock (HF)60(density functional theory, DFT)Hartree-FockHartree-Fock1964 Hohenberg, KohnSham(LDA)Kohn-ShamDFTDFT2.1.2(ab-initio)(first-principles)DFTHF2.1.3171023/cm3Harrtee-Fock2-12-12.1.4 Hohenberg-KohnHH = E 0E001E1E0 E1ENri(ri )3N“”O(e3N)18NKohn“”1964Hohenberg Kohn61(r )EE HohenbergKohn(r )E (r )(r )“”(r )TUVH = T + U +V(2-1)Hohenberg-KohnE = T + V + (r )(r )dr(2-2)2.1.5 Kohn-ShamHohe