Mn和N共掺ZnO稀磁半导体薄膜的研究

使用对Zn₂N₃:Mn薄膜热氧化的方法成功制备了高含N量的Mn和N共掺ZnO的稀磁半导体薄膜.在没有N离子共掺的情况下,ZnO:Mn薄膜的铁磁性非常微弱;如果进行N离子的共掺杂,就会发现ZnO:Mn薄膜在室温下表现出非常明显的铁磁性,饱和离子磁矩为0.23 μ_B—0.61 μ_B.这说明N的共掺激发了ZnO:Mn薄膜中的室温铁磁性,也就是受主的共掺引起的空穴有利于ZnO中二价Mn离子的铁磁性耦合,这和最近的相关理论研究符合很好. 关键词： 磁性半导体 受主掺杂 空穴媒介的铁磁性     

退火对Mn和N共掺杂的Zno0.88Mn0.12O:N薄膜特性的影响

以NH3为掺N源,采用电子柬反应蒸发技术生长了Mn和N共掺杂的Zno0.88Mn0.12O:N薄膜,生长温度为300℃,然后在02气氛中400℃退火0.5 h.X射线衍射测量表明,Zno0.88Mn0.12O(Mn掺杂)薄膜或Zno0.88Mn0.12O:N(Mn和N共掺杂)薄膜仍具有单一晶相纤锌矿结构,未检测到杂质相.与不掺N的Zno0.88Mn0.12O薄膜相比,Zno0.88Mn0.12O:N薄膜的(002)晶面衍射峰向小角度方向偏移且半高宽变宽.Hall效应测量结果显示,Zno0.88Mn0.12O:N薄膜由退火前的n型导电转变为退火后的P型导电.室温磁特性测量结果表明,虽然原生Zno0.88Mn0.12O:N薄膜呈铁磁性,但其饱和磁化强度M.折算到每个Mn2 仅为约0.20μB,且稳定性不理想,在大气中放置30 d后M.降低到原来的3%左右.退火处理不仅使Zno0.88Mn0.12O:N薄膜的室温M.增大到每个Mn2 约为0.70μB,且在大气中放置30 d后其M.几乎不变.分析了Zno0.88Mn0.12O:N薄膜的铁磁性起源及退火导致其铁磁性增强并稳定的机理.     

硼对氮掺杂的p型ZnO薄膜的影响

利用分子束外延设备在蓝宝石衬底上生长了B/N共掺的p型ZnO薄膜,对比了B/N共掺和N单掺杂样品的物理学性能。通过X射线光电子能谱测试证明了在薄膜中存在有B和B-N键。B/N共掺样品的空穴浓度比单一N掺杂样品高近两个量级。且ZnO：（B,N）薄膜在两年多的时间内一直显示稳定的p型电导。这是由于B-N键的存在提高了N在ZnO薄膜中的固溶度,且B-N键之间强的键能和B占据Zn位所表现的弱施主特性不会带来强的施主补偿效应,说明B是N掺杂ZnO薄膜的一种良好的共掺元素。     

铟磷共掺杂p型氧化锌薄膜形成机理和性质

利用射频磁控溅射在石英衬底上生长出铟磷共掺氧化锌薄膜(ZnO ∶ In,P),所用靶材为掺杂五氧化二磷(P₂O₅)和氧化铟(In₂O₃)的氧化锌(ZnO)陶瓷靶,掺杂质量分数分别为1.5%和0.3%,溅射气体为Ar和O₂的混合气体。原生ZnO薄膜是绝缘的, 600 ℃退火5 min后导电类型为n型,而800 ℃退火5 min后为p型。p型ZnO薄膜的电阻率、载流子浓度和霍尔迁移率分别为12.4 Ω·cm, 1.6×10¹⁷ cm^-3 和3.29 cm²·V^-1·s^-1。X射线衍射测量结果表明所有样品都只有(002)衍射峰,并与相同条件下生长的未掺杂ZnO相比向大角度方向偏移,意味着In和P都占据Zn位。XPS测试结果表明在共掺ZnO薄膜中P不是取代O而是取代Zn。因此,铟磷共掺ZnO薄膜中,In和P都取代Zn,并且P_Zn与2个锌空位(V_Zn)形成P_Zn-2V_Zn复合受主,薄膜表现为p型。     

Ag-N共掺p型ZnO的第一性原理研究

采用基于密度泛函理论的第一性原理赝势法对Ag-N共掺杂ZnO体 系以及间隙N和间隙H掺杂p型ZnO: (Ag, N)体系的缺陷形成能和离化能进行了研究. 结果表明, 在Ag_Zn和N_O所形成的众多受主复合体中, Ag_Zn-N_O受主对不仅具有较低的缺陷形成能同时其离化能也相对较小, 因此, Ag_Zn-N_O受主对的形成是Ag-N共掺ZnO体系实现p型导电的主要原因. 研究发现, 当ZnO: (Ag, N)体系有额外间隙N原子存在时, Ag_Zn-N_O受主对容易与N_i形成Ag_Zn-(N₂)_{m O}施主型缺陷, 该施主缺陷的形成降低了Ag-N共掺ZnO的掺杂效率因而不利于p型导电. 当间隙H引入到ZnO: (Ag, N)体系时, H_i易与Ag_Zn-N_O受主对形成 受主-施主-受主复合结构(Ag_Zn-H_i-N_O), 此复合体的形成不仅提高了Ag_Zn-N_O受主对在ZnO中的固溶度, 同时还能使其受主能级变得更浅而有利于p型导电. 因此, H辅助Ag-N共掺ZnO可能是一种有效的p型掺杂手段. 关键词： p型ZnO 缺陷形成能 受主离化能 第一性原理     

Al-N共掺杂ZnO电子结构和光学性质

基于密度泛函理论的第一性原理,分析了Al-N共掺杂ZnO的电子结构和光学性质。计算了Al-N复合体共掺ZnO的结合能,发现Al-N复合体可以在ZnO中稳定存在,因此Al-N共掺可以提高N在ZnO的固溶度。研究表明:N掺杂ZnO体系,由于N-2p和Zn-3d态电子轨道杂化作用,在费米能级附近引入深受主能级,价带顶和导带底发生位移,导致禁带宽带变窄。而Al-N共掺杂体系,适当控制Al和N的比例,克服了N单掺杂时受主间的相互排斥,降低了受主能级,对改善ZnO的p型掺杂有重要意义。在Al-N共掺ZnO中,Al的引入,导致共掺体系的禁带宽度减小,吸收带边红移,实验现象证实了这一结果。     

过渡金属与氮共掺杂ZnO电子结构和光学性质的第一性原理研究

采用基于密度泛函理论框架下的第一性原理平面波超软赝势方法,结合广义梯度近似(GGA)研究了过渡族金属(Mn,Fe,Co,Cu)与N共掺杂ZnO的能带结构、电子态密度分布、差分电荷密度和光学性质.计算表明Mn，Fe，Co与N共掺ZnO的光学性质与Mn，Fe，Co单掺杂相近，但是过渡族金属与N共掺杂有利于获得p型ZnO. 关键词： ZnO 第一性原理 电子结构 光学性质     

Li掺杂ZnO纳米棒的导电和发光特性(英文)

利用气相输运方法,在(111)面硅衬底上制备了名义上原子数分数为2%的Li掺杂的ZnO纳米棒(样品A)。作为比较,我们在相同的生长条件下制备了没有任何掺杂的ZnO纳米棒(样品B)。XRD分析测试表明:样品A和样品B中的ZnO纳米棒具有纤锌矿六边形结构,没有其他氧化物,例如Li2O。Hall效应测量表明:样品A导电类型为p型,空穴载流子浓度为6.72×1016cm-3,空穴载流子迁移率为2.46 cm2.V-1.s-1。样品B为n型,电子载流子浓度为7.16×1018cm-3,电子载流子迁移率为4.73 cm2.V-1.s-1。低温光致发光光谱测试表明,样品A和样品B发光峰明显的区别是位于3.351 eV(样品B)和3.364 eV(样品A)处。根据文献报道,在没有掺杂的ZnO中,3.364 eV发光峰源于施主束缚激子发光。通过变温光致发光光谱的测试,证明了在样品A中,位于3.351 eV的发光峰源于受主束缚激子发光,其光学受主能级位于价带顶142meV处。     

退火温度对N+注入ZnO:Mn薄膜结构及室温铁磁性的影响

采用射频磁控溅射法在石英玻璃衬底上制备了ZnO:Mn薄膜, 结合N⁺ 注入获得Mn-N共掺ZnO薄膜, 进而研究了退火温度对其结构及室温铁磁性的影响. 结果表明, 退火后ZnO:(Mn, N) 薄膜中Mn²⁺和N^3-均处于ZnO晶格位, 没有杂质相生成. 退火温度的升高 有助于修复N⁺注入引起的晶格损伤, 同时也会让N逸出薄膜, 导致受主(N_O)浓度降低. 室温铁磁性存在于ZnO:(Mn, N)薄膜中, 其强弱受N_O浓度的影响, 铁磁性起源可采用束缚磁极化子模型进行解释.     

X射线吸收谱测算锂氮共掺杂氧化锌薄膜局域电子结构

为了实现对Li—N共掺杂p型ZnO薄膜的形成机制以及其稳定p型导电原因的揭示,利用X射线光电子谱及基于同步辐射光源的X射线吸收精细结构谱测试对薄膜的局域电子结构进行了测算分析.获得了Li—N成键及Li—N复合型受主形成的信号,利用光致发光测量计算其受主能级为122 mV.证实了薄膜中Li—N复合型受主的形成,而Li—N...     

First-principles study on nonlocal ferromagnetism in （Cu, N）-codoped ZnO

First-principles calculations based on spin density functional theory are performed to study the spin-resolved electronic properties of ZnO codoped with Cu and N. (Cu, N)-codoped ZnO exhibits magnetism, and the total magnetic moment mainly originates from the p-d hybridization of Cu-N and Cu-O as well as p-p coupling interaction between N and O at the Fermi level. The Zn34Cu2O35N1 favors energetically a ferromagnetic ground state due to the existence of stable Cu-N-Cu complex. These results imply that the (Cu, N)-codoped ZnO is a promising dilute magnetic semiconductor free of magnetic precipitates, which could broaden the horizon of currently known magnetic systems.     

过渡金属掺杂氧化锌团簇的物性研究

本文采用第一性原理密度泛函理论研究了过渡金属（TM）原子Cr和Fe单掺杂和双掺杂(ZnO)12团簇的结构和磁性质。我们考虑了替代掺杂和间隙掺杂。结果表明Cr 和 Fe间隙掺杂团簇结构最稳定。团簇磁矩主要来自TM原子3d态的贡献,4s 和4p 态也贡献了一小部分磁矩。由于轨道杂化,相邻的Zn和O原子上也产生少量自旋。最近邻TM原子间的磁性耦合,主要由两个TM原子之间的直接短程铁磁耦合和TM和O原子之间通过p-d杂化产生的反铁磁耦合这两种相互作用的竞争来决定。不同TM原子掺杂团簇的总磁矩与TM原子种类以及掺杂位置有关,说明在(ZnO)12团簇中掺杂不同TM原子在可调磁矩的磁性材料的领域有潜在应用价值。     

基于XPS与XAS的稀磁半导体GaMnN电子结构研究

采用基于同步辐射技术的X射线光电子能谱(XPS)与X射线吸收谱(XAS)测试由金属有机化学气相沉积(MOCVD)技术制备的不同Mn掺杂浓度的稀磁半导体GaMnN薄膜的电子结构,探究Mn掺杂浓度对磁性原子Mn周围的局域环境和电子态等方面的影响,并阐述材料铁磁性变化的机理. XPS和XAS图谱分析表明：Mn²⁺和Mn³⁺共存于薄膜样品内,样品D中Mn²⁺占比高达70%-80%,N空位随Mn掺杂浓度增加而增多且N空位能够使空穴浓度降低,导致Mn 3d和N 2p轨道间的相互交换作用减小,从而减弱体系铁磁性.此外,Mn不同的掺杂浓度会影响GaMnN薄膜p-d耦合杂化能力的强弱,当掺Mn 1.8%时具有较强的p-d耦合杂化能力.     

The electronic and magnetic properties of （Mn,C）-codoped ZnO diluted magnetic semiconductor

The electronic and magnetic properties of (Mn,C)-codoped ZnO are studied in the Perdew-Burke-Ernzerhof form of generalized gradient approximation of the density functional theory. By investigating five geometrical configurations, we find that Mn doped ZnO exhibits anti-ferromagnetic or spin-glass behaviour, and there are no carriers to mediate the long range ferromagnetic (FM) interaction without acceptor co-doping. We observe that the FM interaction for (Mn,C)-codoped ZnO is due to the hybridization between C 2p and Mn 3d states, which is strong enough to lead to hole-mediated ferromagnetism at room temperature. Meanwhile, we demonstrate that ZnO co-doped with Mn and C has a stable FM ground state and show that the (Mn,C)-codoped ZnO is FM semiconductor with super-high Curie temperature (T C = 5475 K). These results are conducive to the design of dilute magnetic semiconductors with codopants for spintronics applications.     

Mn掺杂的ZnS(001)表面的电子态特性

利用第一性原理计算Mn在ZnS(001)表面上几种掺杂位置的形成能、局域分波态密度和磁矩.对Mn在ZnS(001)表面上的三种位置的形成能进行比较,得到两种填隙位置是非常稳定的掺杂位置.分析ZnS(001):Mn各种再构表面的电子态密度和电荷密度分布.结果表明,三种表面模型中,自旋向上的Mn原子的3d态和近邻S原子的3p态都有一定的杂化,并且替代掺杂的Mn和邻近S原子的p-d杂化最明显,形成的共价键最强.而自旋向下的Mn原子的3d态比较局域,受S原子的3p态影响较小.计算了三种掺杂表面的磁矩,并分析计算结果.     

First-principles prediction of the electronic and magnetic properties of nitrogen-doped ZnO nanosheets

The electronic and magnetic properties of N-doped ZnO nanosheets are investigated by density functional theory using local spin density approximation. The results show that in an isolated N-doped ZnO nanosheet, there is a clear spontaneous polarization of N 2p state with a magnetic moment 1.0 μ_B/N. We also find that the doped nitrogen atoms in ZnO nanosheets have a clustering tendency with ferromagnetic coupling between them, and thus a high room-temperature ferromagnetic nature is expected. The ferromagnetic coupling in N-doped ZnO nanosheets can be attributed to the hole-mediated double-exchange mechanism through strong p–d interaction between nitrogen and zinc atoms.     

Electronic Structure and Magnetic Properties of Cu[C(CN)3]2 and Mn[C(CN)3]2 Based on First Principles

The electronic structure and the magnetic properties of the molecule-based ferromagnets Cu[C(CN)₃]₂ and Mn[C(CN)₃]₂ are studied accordingto first principles within density-functional theory (DFT) and the full potential linearized augmented plane wave (FP-LAPW) method. The total energy, atomic spin magnetic moments, and density of states (DOS) of Cu[C(CN)₃]₂ and Mn[C(CN)₃]₂ are all calculated. The calculations reveal that the compounds have a stable ferromagnetic ground state and half-metallic properties. The total spin magnetic moment is 1.0 μ_B for Cu[C(CN)₃]₂ and 5.0 μ_B for Mn[C(CN)₃]₂ per molecule, the magnetic moment mainly comes from metal atoms, although there is a slight contribution from N and C atoms.     

Electronic structure and magnetic properties of Cr monodoped and (Cr, Al) codoped ZnO

Using first-principles calculations based on density functional theory, we investigated systematically the electronic structures and magnetic properties of Cr monodoped and (Cr, Al) codoped in ZnO. The results indicate that Cr monodoped in ZnO favors a spin-polarized state with a total magnetic moment of 7.50μ_B per supercell and the magnetic moment mainly comes from the unpaired 3d electrons of Cr atoms. In addition, it was found that the ferromagnetic exchange interaction between Cr atoms is short-ranged in Cr monodoped ZnO. Interestingly, the ferromagnetic stability can be enhanced significantly by codoping Al_Zn. We think that the enhancement of ferromagnetic stability should be attributed to the additional electrons introduced by Al_Zn codoping.     

Structural,electronic,and magnetic properties of transition-metal atom adsorbed two-dimensional GaAs nanosheet

By using first-principles calculations within the framework of density functional theory,the electronic and magnetic properties of 3d transitional metal(TM) atoms(from Sc to Zn) adsorbed monolayer Ga As nanosheets(Ga As NSs) are systematically investigated.Upon TM atom adsorption,Ga As NS,which is a nonmagnetic semiconductor,can be tuned into a magnetic semiconductor(Sc,V,and Fe adsorption),a half-metal(Mn adsorption),or a metal(Co and Cu adsorption).Our calculations show that the strong p–d hybridization between the 3d orbit of TM atoms and the 4p orbit of neighboring As atoms is responsible for the formation of chemical bonds and the origin of magnetism in the Ga As NSs with Sc,V,and Fe adsorption.However,the Mn 3d orbit with more unpaired electrons hybridizes not only with the As 4p orbit but also with the Ga 4p orbit,resulting in a stronger exchange interaction.Our results may be useful for electronic and magnetic applications of Ga As NS-based materials.