N空位对Cu掺杂AlN电磁性质的影响的第一性原理研究

利用基于密度泛函理论的平面波超软赝势法研究了N空位对Cu掺杂AlN的电子结构和磁学性质的影响。结果表明,与Cu最近邻的N原子更易失去形成N空位。N空位的引入减小了Cu掺杂AlN体系的半金属能隙;减弱了Cu及其近邻N原子的自旋极化的强度以及Cu3d与N2p轨道间的杂化,因而减小了体系的半金属铁磁性。因此,制备Cu掺杂AlN稀磁半导体时应尽可能地避免产生N空位。     

N空位对Cu掺杂AlN电磁性质的影响的第一性原理研究

利用基于密度泛函理论的平面波超软赝势法研究了N空位对Cu掺杂AlN的电子结构和磁学性质的影响.结果表明,与Cu最近邻的N原子更易失去形成N空位.N空位的引入减小了Cu掺杂AlN体系的半金属能隙;减弱了Cu及其近邻N原子的自旋极化的强度以及Cu3d与N2p轨道间的杂化,因而减小了体系的半金属铁磁性.因此,制备Cu掺杂AlN稀磁半导体时应尽可能地避免N空位的产生.     

不同浓度Cu掺杂AlN的电子结构和光学性质研究

采用基于密度泛函理论的平面波超软赝势和广义梯度近似的第一性原理计算方法,对理想纤锌矿AlN及不同浓度的Cu掺AlN的超晶胞结构进行了几何优化,计算并分析了它们的电子结构、磁电性质和光学性质.结果表明,掺杂后Cu3d态电子与其近邻的N2p态电子发生杂化,在带隙中引入杂质带,6.25%和12.5%的Cu掺杂体系表现出半金属铁磁性,体系总磁矩分别为2.56μв和2.42μв,25%的Cu掺杂体系表现出金属性.随着Cu浓度的增加,体系铁磁性反而减弱.Cu掺杂后体系介电函数虚部和复折射率函数在低能区发生明显变化,增强了体系对低频电磁波的吸收.当Cu浓度增加时体系对高频电磁波的吸收也随之加强.     

C掺杂AlN的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(DFT)的平面波超软赝势法,研究了C掺杂铅锌矿AlN的电子结构、磁性和光学性质.结果表明,C掺杂AlN产生了自旋极化,在带隙中引入杂质带形成受主能级,实现p型掺杂,同时表现出较强的半金属铁磁性,半金属能隙为0.315eV,理论上可实现100%的自旋载流子注入.掺杂后体系的介电函数虚部和光吸收系数在低能区出现新的峰值,吸收边向低能方向延展,能量损失明显减少.     

Cu掺杂的AlN铁磁性和光学性质的第一性原理研究

采用基于密度泛函理论（DFT）的总体能量平面波超软赝势方法,结合广义梯度近似（GGA）,对Cu掺杂AlN 32原子超原胞体系进行了几何结构优化,计算了Cu掺杂AlN的晶格常数,能带结构,电子态密度和光学性质.结果表明,Cu掺杂AlN会产生自旋极化状态,能带结构显示半金属性质,掺杂后带隙变窄,长波吸收加强,能量损失明显减小.同传统的稀磁半导体（DMS）相比,Cu掺杂AlN不会有铁磁性沉淀物的问题,因为Cu本身不具有磁性.因而,Cu掺杂的AlN也许是一种非常有前途的稀磁半导体. 关键词： AlN 第一性原理 铁磁性 光学性质     

C掺杂AlN的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(DFT)的平面波超软赝势法,研究了C掺杂铅锌矿AlN的电子结构、磁性和光学性质.结果表明,C掺杂AlN产生了自旋极化,在带隙中引入杂质带形成受主能级,实现p型掺杂,同时表现出较强的半金属铁磁性,半金属能隙为0.315eV,理论上可实现100%的自旋载流子注入.掺杂后体系的介电函数虚部和光吸收系数在低能区出现新的峰值,吸收边向低能方向延展,能量损失明显减少.     

C掺杂AlN的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(DFT)的平面波超软赝势法,研究了C掺杂铅锌矿AlN的电子结构、磁性和光学性质.结果表明,C掺杂AlN产生了自旋极化,在带隙中引入杂质带形成受主能级,实现p型掺杂,同时表现出较强的半金属铁磁性,半金属能隙为0.315eV,理论上可实现100%的自旋载流子注入.掺杂后体系的介电函数虚部和光吸收系数在低能区出现新的峰值,吸收边向低能方向延展,能量损失明显减少.     

Ti,Cu和Zn掺杂AlN纳米片电磁性质的第一性原理研究

采用基于密度泛函理论(DFT)的全势线性缀加平面波法(FP-LAPW)研究了过渡金属Ti,Cu,Zn掺杂Al N纳米片的电子结构、磁性和稳定性.结果表明,Ti,Cu,Zn单掺杂均表现出半金属铁磁性,磁性主要是由于杂质原子的3d态与近邻N原子的2p态的轨道杂化.形成能的计算结果表明Ti掺杂Al N体系相对Cu和Zn掺杂结构更稳定.因此,相比于Cu和Zn,Ti掺杂Al N纳米片更适合用来制作稀磁半导体.     

Mn掺杂GaN稀磁半导体的电磁特性研究

采用基于密度泛函理论的第一性原理平面波超软赝势法计算了不同浓度Mn掺杂GaN（Ga1-xMnxN, x=0.0625和0.1250）的晶格常数、能带结构和态密度,分析比较了掺杂前后GaN的电子结构和磁性。结果表明：Mn掺入后体系仍为直接带隙半导体,带隙宽度随Mn含量的增加逐步增大。Mn掺杂GaN均使得N 2p与Mn 3d轨道杂化,产生自旋极化杂质带,自旋向上的能带占据费米面,掺杂后的Ga1-xMnxN表现为半金属铁磁性,适合自旋注入;随着Mn掺杂浓度的增加,体系的半金属性有所增强。     

Mn掺杂GaN稀磁半导体的电磁特性研究

采用基于密度泛函理论的第一性原理平面波超软赝势法计算了不同浓度Mn掺杂GaN(Ga1-xMnxN,x=0.0625和0.1250)的晶格常数、能带结构和态密度,分析比较了掺杂前后GaN的电子结构和磁性.结果表明:Mn掺入后体系仍为直接带隙半导体,带隙宽度随Mn含量的增加逐步增大.Mn掺杂GaN均使得N2p与Mn3d轨道杂化,产生自旋极化杂质带,自旋向上的能带占据费米面,掺杂后的Ga1-xMnxN表现为半金属铁磁性,适合自旋注入;随着Mn掺杂浓度的增加,体系的半金属性有所增强.     

First-principles study on the origin of ferromagnetism in n-type Cu-doped ZnO

Based on the density functional calculations with the GGA+U correction, we elucidate the origin of the experimentally reported ferromagnetism in n-type Cu-doped ZnO. Pure Cu-doped ZnO shows the unoccupied 3d states in the gap introduced by Cu, resulting in the insulating ground state and weak magnetic exchange interactions, in contrast to the half-metallic ground state and high ferromagnetic stability predicted by the calculations without U correction. However, the electron traps induced by Cu in n-type Cu-doped ZnO may lead to the partial occupancy of the Cu gap states, which stabilize the ferromagnetic ordering between two Cu atoms.     

Half-metallic ferromagnetism in Cu-doped zinc-blende ZnO from first principles study

Electronic structures and magnetism of Cu-doped zinc-blende ZnO have been investigated by the first-principle method based on density functional theory (DFT). The results show that Cu can induce stable ferromagnetic ground state. The magnetic moment of supercell including single Cu atom is 1.0 μ_B. Electronic structure shows that Cu-doped zinc-blende ZnO is a p-type half-metallic ferromagnet. The half-metal property is mainly attribute to the crystal field splitting of Cu 3d orbital, and the ferromagnetism is dominated by the hole-mediated double exchange mechanism. Therefore, Cu-doped zinc-blende ZnO should be useful in semiconductor spintronics and other applications.     

First-principles study of electronic structures and optical properties of Cu, Ag, and Au-doped anatase TiO2

We perform first-principles calculations to investigate the band structure, density of states, optical absorption, and the imaginary part of dielectric function of Cu, Ag, and Au-doped anatase TiO₂ in 72 atoms systems. The electronic structure results show that the Cu incorporation can lead to the enhancement of d states near the uppermost of valence band, while the Ag and Au doping cause some new electronic states in band gap of TiO₂. Meanwhile, it is found that the visible optical absorptions of Cu, Ag, and Au-doped TiO₂, are observed by analyzing the results of optical properties, which locate in the region of 400-1000 nm. The absorption band edges of Cu, Ag, and Au-doped TiO₂ shift to the long wavelength region compared with the pure TiO₂. Furthermore, according to the calculated results, we propose the optical transition mechanisms of Cu, Ag, and Au-doped TiO₂. Our results show that the visible light response of TiO₂ can be modulated by substitutional doping of Cu, Ag, and Au.     

Copper-doped AlN polycrystalline powders: A class of room-temperature ferromagnetic materials

Cu-doped AlN polycrystalline samples were synthesized by a solid-state reaction. X-ray diffraction analysis revealed the hexagonal structure of the doped samples. Photoluminescence measurements reveal the substitution of Cu for Al in the AlN lattice. Clear hysteresis loops are observed in the M-H curves for the samples at 300 K, revealing room temperature ferromagnetism of the samples. Our experimental results verify that room temperature ferromagnetism is an intrinsic property of Cu-doped AlN.     

First-principles study on electronic and magnetic properties of Cu-doped CdS

Based on the full-potential linearized augmented plane wave (FLAPW) method, the electronic structures and magnetic properties in Cu-doped CdS diluted magnetic semiconductors (DMSs) have been investigated. The results indicate that Cu-doped CdS systems show half-metallic character with a total magnetic moment of 1.0 μ_B per supercell. In the case of two Cu atoms substituting for Cd atoms, the long-range ferromagnetism is observed, which results from Cu(3d)-S(3p)-Cd-S(3p)-Cu(3d) coupling chain. The estimated Curie temperature of Cu-doped CdS is predicted to be 400 K, higher than room temperature. These results suggest that Cu-doped CdS may be a promising half-metallic ferromagnetic material for practical applications in electronics and spintronics.     

Electronic Structure and Magnetic Properties of Cr-Doped AlN

To understand the electronic and magnetic properties, we have studied Cr-doped zinc-blende AlN system in detail by applying a first-principle plane wave pseudopotential method based on the density functional theory within the local spin density approximation. The analyses of the band structures, density of states, exchange interactions, and magnetic moments show that Al1-xCrxN alloys may exhibit a half-metallic ferromagnetism character, that Cr in the diluted doping limit forms near-midgap deep levels, and that the total magnetization of the cell is 3μB per Cr atom, which does not change with Cr concentration. Moreover, we have succeeded in predicting that Al1-xCrzN alloys in x = 0.0625 has a very high Curie temperature, and lind that ferromagnetic exchange interaction between magnetic dopants is short-ranged.     

The magnetic phase transition in Cu-doped ZnO: From bulk to nanocluster

Using the first-principles calculations based on the density functional theory, we have investigated the magnetic properties of Cu-doped ZnO both in bulk and nanocluster. The calculated results show that the substitutional Cu ions are spin polarized and have a tendency to assemble. It is found that the ground state has shown a change from ferromagnetic phase to antiferromagnetic phase as the size for the doping system decreases from bulk to nanocluster. In bulk ZnO, the ferromagnetism is attributed to the strong hybridization between Cu 3d and O 2p states. In ZnO nanocluster, however, the antiferromagnetic exchange interaction is dominant because of the very close Cu–Cu distance.     

Synthesis,structural, optical and magnetic properties of Cu-doped ZnO nanorods prepared by a simple direct thermal decomposition route

Cu-doped ZnO nanorods (i.e. Cu = 1.75, 3.55, 5.17 and 6.39 at.%) have been successfully synthesized by simple, direct, thermal decomposition of zinc and copper acetates in air at 300 °C for 6 h. The prepared samples were characterized by X-ray diffraction (XRD) and transmission electron microscopy. The XRD results indicate that the 1.75 at.% Cu-doped ZnO sample has a pure phase with the ZnO wurtzite structure, while the impurity phases are detected with increasing Cu concentrations. It was found that the doping of Cu results in a reduction of the preparation temperature. The optical properties of the samples were also investigated by UV–visible spectroscopy and photoluminescence measurements. The results show that the Cu doping causes the change in energy-band structures and effectively adjusts the intensity of the luminescence properties of ZnO nanorods. X-ray photoelectron spectroscopy analysis implies that there are some oxygen vacancies in the samples and also indicates that all the doped samples are associated with the mixture of Cu ion states (Cu²⁺ and Cu¹⁺/Cu⁰). Magnetic measurements by vibrating sample magnetometry indicate that undoped ZnO is diamagnetic, whereas all of the Cu-doped ZnO samples exhibit room temperature ferromagnetic behavior. We suggest that Cu substitution and density of oxygen vacancies (V _o) may play a major role in the room temperature magnetism of the Cu-doped ZnO samples.