磁控溅射法制备钴掺杂氧化锌薄膜室温磁学性质（英文）

钴掺杂氧化锌是室温稀磁半导体的重要候选材料,其磁学特性和钴掺杂浓度、显微结构及光学性质密切相关。磁控溅射具有成本低、易于大面积沉积高质量薄膜等特点,是广受关注的稀磁半导体薄膜制备方法。利用磁控溅射方法制备了不同浓度的钴掺杂氧化锌薄膜,并对其显微结构、光学性质和磁学特性进行了系统分析。结果表明:当掺杂原子分数在8%以内时,钴掺杂氧化锌薄膜保持单一的铅锌矿晶体结构,钴元素完全溶解在氧化锌晶格之中;薄膜在可见光区域有很高的透射率,但在567,615和659nm处有明显吸收峰,这些吸收峰源于Co2+处于O2-形成的四面体晶体场中的特征d-d跃迁。磁学特性测试结果表明钴掺杂氧化锌薄膜具有室温铁磁性,且钴的掺杂浓度对薄膜的磁学特性有重要影响。结合薄膜结构、光学和电学性质分析,实验中观察到的室温铁磁性应源于钴掺杂氧化锌薄膜的本征属性,其铁磁耦合机理可由束缚磁极化子模型进行解释。     

表面活性剂和n型载流子对钴掺杂氧化锌薄膜铁磁性的双重调控

本文提出了一种利用表面活性剂钝化和电子载流子掺杂来调制钴掺杂氧化锌稀磁半导体薄膜固有铁磁性的"双重操纵效应"新方法.第一性原理计算表明,氢表面钝化作为薄膜表面Co-O-Co磁耦合的磁开关,可以控制掺杂钴原子的自旋极化.同时,电子载流子掺杂可以进一步用作类层状铁磁性媒介来调节薄膜内部原子层的铁磁性.该双重操纵效应揭示了n型钴掺杂氧化锌稀磁半导体薄膜的本质铁磁性来源,并且还有可能用作其他n型稀磁半导体氧化物薄膜增强铁磁性的替代策略.     

表面活性剂和n型载流子对钴掺杂氧化锌薄膜铁磁性的双重调控（英文）

本文提出了一种利用表面活性剂钝化和电子载流子掺杂来调制钴掺杂氧化锌稀磁半导体薄膜固有铁磁性的"双重操纵效应"新方法.第一性原理计算表明,氢表面钝化作为薄膜表面Co-O-Co磁耦合的磁开关,可以控制掺杂钴原子的自旋极化.同时,电子载流子掺杂可以进一步用作类层状铁磁性媒介来调节薄膜内部原子层的铁磁性.该双重操纵效应揭示了n型钴掺杂氧化锌稀磁半导体薄膜的本质铁磁性来源,并且还有可能用作其他n型稀磁半导体氧化物薄膜增强铁磁性的替代策略.     

Co掺杂的ZnO室温铁磁半导体材料制备与磁性和光学特性研究

采用溶胶-凝胶法制备出具有室温铁磁性的Co掺杂的ZnO稀磁半导体材料. 通过对样品的结构、磁性和发光特性的研究发现,样品具有室温铁磁性,并发现其铁磁性源于磁性离子对ZnO中Zn离子的取代. 对不同温度制备的样品的磁性以及其发光特性的变化研究发现,样品的铁磁性与样品中锌间隙位（Zn_i）缺陷的密度有关. 关键词： ZnO 稀磁半导体 铁磁性     

结构相变对Fe掺杂TiO2薄膜室温铁磁性的影响

采用直流磁控溅射方法在玻璃基底上制备了不同Fe掺杂浓度的TiO₂薄膜, 并对其晶体结构和磁特性进行了研究.在所有掺杂样品中,均观察到了室温铁磁性, 磁性源于Fe离子与其近邻空间分布的空穴相互作用. 在掺杂量为7%的锐钛矿相薄膜中观察到了最大的磁化强度. 随着Fe掺杂浓度的进一步增加, TiO₂的晶体结构逐渐由锐钛矿相向金红石相转变,并且磁性减弱. 不同结构的TiO₂中Ti–O键长不同,导致替代的磁性Fe离子与空穴的作用强度发生改变, 进而使其磁性发生变化. 关键词： 稀磁半导体 结构相变 铁磁性     

溶胶凝胶合成锰掺杂ZnO的室温磁性行为

通过溶胶凝胶自燃法合成锰掺杂氧化锌纳米晶体, 研究了Mn掺杂ZnO稀磁半导体(简称DMS)的性质．X射线衍射光谱表明,锰掺杂氧化锌保留纤锌矿型状氧化锌六角晶体结构．采用能量色散X射线能谱和扫描电子显微镜分别对成分和形态进行研究．温度依赖的电阻率显示了DMS的半导体材料行为．振动样品磁强计测定的室温磁性行为,揭示了锰掺杂氧化锌的铁磁性和反磁性特性.     

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     

氧空位对钴掺杂氧化锌半导体磁性能的影响

从实验和理论上阐述了氧空位对Co掺杂ZnO半导体磁性能的影响.采用磁控溅射法在不同的氧分压下制备了Zn_095Co_005O薄膜,研究了氧分压对薄膜磁性能的影响.实验结果表明,高真空条件下制备的Zn_095Co_005O薄膜具有室温铁磁性,提高氧分压后制备的薄膜铁磁性逐渐消失.第一性原理计算表明,在Co掺杂ZnO体系中引入氧空位有利于降低铁磁态的能量,铁磁态的稳定性与氧空位和Co之间的距离密切相关. 关键词： Co掺杂ZnO 稀磁半导体 第一性原理计算 氧空位缺陷     

Zn1-xCoxO稀磁半导体薄膜的结构及其磁性研究

利用X射线吸收精细结构、X射线衍射和磁性测量等技术研究脉冲激光气相沉积法制备的Zn1-zCoxO(x=0.01,0.02)稀磁半导体薄膜的结构和磁性.磁性测量结果表明Zn1-xCoxO样品都具有室温铁磁性.X射线衍射结果显示其薄膜样品具有结晶良好的纤锌矿结构.荧光X射线吸收精细结构测试结果表明,脉冲激光气相沉积法制备的样品中的Co离子全部进入ZnO晶格中替代了部分Zn的格点位置,生成单一相的Zn1-xCoxO稀磁半导体.通过对X射线吸收近边结构谱的分析,确定Zn1-xCoxO薄膜中存在O空位,表明Co离子与O空位的相互作用是诱导Zn1-xCoxO产生室温铁磁性的主要原因.     

钴掺杂二氧化锡纳米粉的光致发光和磁学性质

研究了钴掺杂对二氧化锡纳米粉的光致发光性质和磁学性质的影响,发现钴掺杂对发光带的位置影响很小,但紫外发光带与蓝色发光带的强度之比随掺杂含量的增加而下降.当钴掺杂含量达到0.02时,样品中的铁磁性被完全破坏.讨论了样品中的磁相互作用的机理,认为掺杂离子的不均匀分布、自旋极化子与掺杂离子之间的耦合都可能导致反铁磁性的相互作用,这种反铁磁性的作用破坏了铁磁性. 关键词： 钴掺杂二氧化锡 光致发光 磁学性质     

Study on the ferromagnetism in Co and N doped ZnO thin films

Present investigation reports the structural, optical and magnetic properties of co-doping of Co and N ions in ZnO samples, prepared by two distinct methods. In the first method, samples are synthesized by Sol–gel technique in which the Co and N are co-doped simultaneously during the growth process itself. In the second case, N ions are implanted in the Co doped ZnO thin films grown by Pulsed Laser Deposition (PLD). Structural studies showed that the nitrogen implantation on Co doped ZnO samples developed compressive stress in the films. X-ray photoelectron spectroscopy confirmed the doping of Co and N in ZnO matrix. In the Resonant Raman scattering multiple LO phonons up to fifth order are observed in the (Co, N) co-doped ZnO. Photoluminescence spectra showed that there is reduction in the bandgap due to the presence of Co in the lattice and also the presence of Zn vacancies in the films. All samples showed ferromagnetic behavior at room temperature. The magnetic moment observed in the implanted films is found to be varied with the different dosages of the implanted N ions. First principle calculations have been carried out to study the possible magnetic interaction in the co-doped system. Present study shows that the ferromagnetic interaction is due to the hybridization between N 2p and Co 3d states in the (Co, N) co-doped ZnO and is very sensitive to the geometrical configurations of dopants and the vacancy in the ZnO host lattice.     

Structural and Magnetic Properties of Codoped ZnO based Diluted Magnetic Semiconductors

Zn1-xCoxO （x = 0.01, 0.02, 0.05, 0.10 and 0.20） diluted magnetic semiconductors are prepared by the sol-gel method. The structural and magnetic properties of the samples are studied using x-ray diffraction （XRD）, extended x-ray absorption fine structure （EXAFS） and superconducting quantum interference device （SQUID）. The XRD patterns does not show any signal of precipitates that are different from wurtzite type ZnO when Co content is lower than x = 0.10. An EXAFS technique for the Co K-edge has been employed to probe the local structures around Co atoms doped in ZnO powders by fluorescence mode. The simulation results for the first shell EXAFS signals indicate that Zn sites can be substituted by Co atoms when Co content is lower than x = 0.05. The SQUID results show that the samples （x 〈 0.05） exhibit clear hysteresis loops at 300K, and magnetization versus temperature from 5 K to 350K at H = 100 Oe for the sample x = 0.02 shows that the samples have ferromagnetism above room temperature. A double-exchange mechanism is proposed to explain the ferromagnetic properties of the samples.     

Influence of substrate temperature and Cobalt concentration on structural and optical properties of ZnO thin films prepared by Ultrasonic spray technique

Pure and Cobalt doped zinc oxide were deposited on glass substrate by Ultrasonic spray method. Zinc acetate dehydrate, Cobalt chloride, 4-methoxyethanol and monoethanolamine were used as a starting materials, dopant source, solvent and stabilizer, respectively. The ZnO samples and ZnO:Co with Cobalt concentration of 2 wt.% were deposited at 300, 350 and 400 °C. The effects of substrate temperature and presence of Co as doping element on the structural, electrical and optical properties were examined. Both pure and Co doped ZnO samples are (0 0 2) preferentially oriented. The X-ray diffraction results indicate that the samples have polycrystalline nature and hexagonal wurtzite structure with the maximum average crystallite size of ZnO and ZnO:Co were 33.28 and 55.46 nm. An increase in the substrate temperature and presence doping the crystallinity of the thin films increased. The optical transmittance spectra showed transmittance higher than 80% within the visible wavelength region. The band gap energy of the thin films increased after doping from 3.25 to 3.36 eV at 350 °C.     

Co掺杂ZnO薄膜的结构和磁学性能

研究了用单束脉冲激光沉积法制备的Co掺杂ZnO薄膜的结构和磁学性能。XRD表征结果表明制备的薄膜是具有沿c轴择优取向的纤锌矿点阵结构。然而,进一步的高分辨电子显微镜结果显示整个样品上的晶体取向并不完全相同。很难说明形成了单晶。结果分析表明Co占据了部分Zn的格点,并对电子结构产生了影响。室温下观察到了磁滞回线,显示掺杂Co可以实现ZnO的磁性翻转,但磁性比较小。该薄膜与我们以前用双束脉冲激光沉积法制备的Co掺杂ZnO薄膜具有相似的性能,提示我们其内部的机制可能相似。     

Local structure investigation of (Co,Cu) co-doped ZnO nanocrystals and its correlation with magnetic properties

Pure, Co doped and (Co, Cu) co-doped ZnO nanocrystals have been prepared by wet chemical route at room temperature to investigate the effect of Cu doping in Co doped ZnO nanocrystals . The nanocrystals have initially been characterized by X-ray diffraction, FTIR, Raman, optical absorption and EPR spectroscopy and the results were corroborated with DFT based electronic structure calculations. Magnetic properties of the samples have been investigated by studying their magnetic hysteresis behavior and temperature dependence of susceptibilities. Finally the local structure at the host and dopant sites of the nanocrystals have been investigated by Zn, Co and Cu K edges EXAFS measurements with synchrotron radiation to explain their experimentally observed magnetic properties.     

Synthesis and characterization of ZnO:Co<Superscript>2+</Superscript> nanoparticles

This work investigates cobalt doped ZnO nanoparticles prepared by using wet chemical methods. The nanoparticles have a typical size of 3–8 nm. The electronic structure as well as the optical and magnetic properties of Co²⁺ have been characterized. X-ray diffraction spectra of the powder show wurtzite ZnO with no secondary Co phases. In the energy range below the bandgap, the optical absorption spectra show the internal d–d transitions related to Co²⁺ incorporated on the Zn lattice site in ZnO. Low temperature photoluminescence measurements confirm these results. Based on the analysis of the g-valuesfor bulk ZnO:Co., electron paramagnetic resonance measurements coincide with the simulation of Co-doped ZnO powder. Thus far, no evidence for ferromagnetism has been obtained. PACS 61.46.Df; 76.30.Fc; 78.67.Bf     

退火氛围对掺杂ZnO薄膜磁性的影响

采用直流磁控反应共溅法制备了非磁性元素Al和磁性元素Co掺杂的ZnO薄膜, 样品原位真空退火后再空气退火处理. 利用X射线衍射仪(XRD) 和物理性能测量仪(PPMS) 对薄膜的结构和磁性进行了表征. XRD和PPMS结果表明, 不同的退火氛围对掺杂薄膜的结构和磁性有着很大的影响. 真空退火的Al掺杂ZnO薄膜没有观察到铁磁性, 而空气退火的样品却显示出明显的室温铁磁性, 铁磁性的来源与空气退火后导致Al和ZnO基体间电荷转移增强有关. 而对于Co掺杂ZnO薄膜, 真空退火后再空气退火, 室温铁磁性明显减弱. 其磁性变化与Co离子和ZnO基体间电荷转移导致磁性增强和间隙Co原子被氧化导致磁性减弱有关.     

Optical and electrical properties of undoped and (Mn, Co) co-doped ZnO nanoparticles synthesized by DC thermal plasma method

The undoped and (Mn, Co) co-doped ZnO nanopowders were synthesized through DC thermal plasma method. The pellets of this powder were annealed at 450, 550 and 650 °C for 1 h. Structural, chemical and optical properties of the samples were studied by XRD, SEM, EDX, UV–Vis and PL analysis. XRD spectra showed that all the samples were hexagonal wurtzite structure and as the annealing temperature increases the material becomes purer and more crystalline. It is seen that the optical band gap decreases when the ZnO is doped with manganese and cobalt. Photoluminescence intensity varies with doping because of the increment of oxygen vacancies. DC conductivity studies of the pellets were carried out at different temperatures (25–100 °C) and it was found that the activation energy for the electrical transport is high for (Mn, Co) co-doped ZnO than undoped ZnO.     

Influence of Ag doping on structural and optical properties of ZnO thin films synthesized by the sol–gel technique

Thin films of Ag–ZnO samples deposited on glass substrates with a different percentage of Ag content (1, 2, and 3 at%) were synthesized, at room temperature, by a dip-coating sol-gel method. The obtained samples are hexagonal wurtzite structure. The average grain size of deposits is about 5 nm. Up to 3 at%, c-axis lattice parameter shifts toward a higher value, which indicates that silver atoms replace Zn atoms in the crystal lattice. As shown by the DRX spectra, growth rate in the (101) direction is favored by the presence of silver ions in the ZnO. The layers present a homogeneous crystallites distribution, as we can remark it on SEM micrographs and exhibit a very low roughness according to AFM images. The entire samples exhibit a transmission value greater than 80 %, in the visible region, while the maximum is obtained for those doped at 2 at%. Energy band varies between 3.15 eV and 3.25 eV. The wider gap obtained is that of the ZnO layer doped with 2 at%. It is worth noting a strong UV emission observed on PL spectrum, performed at very low temperature (liquid nitrogen temperature), for silver doped ZnO compared to that of pure ZnO.     

过渡金属与F共掺杂ZnO薄膜结构及磁、光特性

采用溶胶-凝胶法在玻璃衬底上制备了过渡金属元素与F共掺杂Zn_0.98-xTM_xF_0.02O (TM_x=Cu_0.02, Ni_0.01, Mn_0.05, Fe_0.02, Co_0.05)薄膜, 进而利用X射线衍射仪、扫描电子显微镜、紫外-可见透过谱、光致发光及振动样品磁强计等研究了薄膜的表面形貌、微结构、禁带宽度及光致发光(PL)和室温磁学特性. 研究表明: 掺杂离子都以替位的方式进入了ZnO晶格, 掺杂不会破坏ZnO的纤锌矿结构. 其中Zn_0.93Co_0.05F_0.02O薄膜样品的颗粒尺寸最大, 薄膜的结晶度最好且c轴择优取向明显; Zn_0.93Mn_0.05F_0.02O薄膜样品的颗粒尺寸最小, 薄膜结晶度最差且无明显的c轴择优取; Cu, Ni, Fe与F共掺杂样品的颗粒尺寸大小几乎相同. TM掺杂样品均表现出很高的透过率, 同时掺杂后的薄膜样品的禁带宽度都有不同程度的红移. PL谱观察到Zn_0.98-xTM_xF_0.02O薄膜的发射峰主要由较强的紫外发射峰和较弱的蓝光发射峰组成. Zn_0.93Mn_0.05F_0.02O薄膜样品的紫外发光峰最弱, 蓝光发射最强, 饱和磁化强度最大; 与之相反的是Zn_0.96Cu_0.02F_0.02O薄膜, 其紫外发光峰最强, 蓝光发射最弱, 饱和磁化强度最小. 结合微结构和光学性质对Zn_0.98-xTM_xF_0.02O薄膜的磁学性质进行了讨论.