脉冲磁场下水热法制备Cr掺杂ZnO稀磁 半导体晶体

本文以ZnCl₂, CrCl₃. 6H₂O和氨水缓冲溶液为原料, 在4T脉冲磁场下水热法制备了Cr掺杂ZnO稀磁半导体晶体, 通过X射线衍射分析、扫描电子显微镜观察及采用振动样品磁强计进行磁性分析等, 探讨了脉冲磁场对其微观结构及磁性能的影响. 结果表明: Cr掺杂ZnO稀磁半导体晶体仍保持ZnO的六方纤锌矿结构, 脉冲磁场具有促进晶粒生长及取向排列的作用, 4T脉冲磁场条件下合成的Cr掺杂ZnO稀磁半导体具有良好的室温铁磁性, 其饱和磁化强度(M_s)为0.068 emu/g, 而无脉冲磁场情况下制备的样品室温下呈顺磁性, 并且, 脉冲磁场下制备将稀磁半导体的居里温度提高了16 K.     

Mn掺杂ZnO稀磁半导体材料的制备和磁性研究

采用共沉淀方法制备了名义组分为Zn_1-xMn_xO(x=0.001,0.005,0.007,0.01)的Mn掺杂的ZnO基稀磁半导体材料,并研究了在大气气氛下经过不同温度退火后样品的结构和磁性的变化.结果表明：样品在600℃的大气条件下退火后, 仍为单一的六方纤锌矿结构的ZnO颗粒材料;当样品经过800℃退火后,Mn掺杂量为0.007,0.01的样品中除了ZnO纤锌矿结构外还观察到ZnMnO₃第二相的存在.磁性测量表明,大气条件下600℃退火后的样品,呈现出室温铁磁性;而800℃退火后的样品,其室温铁磁性显著减弱,并表现为明显的顺磁性.结合对样品的光致发光谱的分析,认为合成样品的室温铁磁性是由于Mn离子对ZnO中的Zn离子的替代形成的. 关键词： ZnO 掺杂 稀磁半导体 铁磁性     

Mn掺杂对ZnO∶Mn薄膜结构特性的影响

利用射频磁控溅射方法在玻璃衬底上室温沉积了一系列不同Mn掺杂的ZnO∶Mn薄膜。结合Raman光谱,XRD谱和SEM分析了ZnO∶Mn薄膜的结构特性。Raman拟合结果显示,在Mn摩尔分数从0增加到5.6%的过程中,ZnO∶Mn薄膜始终保持着六角纤锌矿结构;随着Mn掺杂浓度的增大,437 cm-1和527 cm-1位置上的Raman散射峰出现红移现象,说明Mn掺杂量的增加导致晶格更加无序,缺陷增多;当Mn摩尔分数达到15.8%时,647 cm-1处的Raman散射峰出现,暗示了MnO的产生,同时薄膜结晶质量变差。这一结论也得到了XRD和SEM结果的支持。     

稀磁半导体的制备与性质

报道了稀磁半导体的制备、性质与实验研究进展，介绍了稀磁半导体的应用及发展前景．     

工作气压对ZnO:Mn薄膜结构特性的影响

利用射频磁控溅射方法在玻璃衬底上沉积了一系列ZnO:Mn薄膜,结合Raman光谱、XRD衍射谱和SEM分析了工作气压对ZnO:Mn薄膜结构特性的影响。Raman拟合光谱显示,在工作气压从1 Pa增加至4 Pa的过程中,ZnO:Mn薄膜始终保持着六角纤锌矿结构。但是,随着气压的降低,对应于E2(High)振动模式的Raman散射峰以及与Mn掺杂相关的特征峰左移,说明在低工作气压时,ZnO:Mn薄膜内晶格缺陷更多,晶格更加无序。这一结论也得到了XRD和SEM结果的证实。     

Mn掺杂ZnSe前驱体纳米带的制备及其磁光性质

采用了改进的水热途径制备稀磁半导体Mn掺杂ZnSe前驱体纳米带MnxZn1-xSe?en3 (en=ethylenediamine). 与先前方法相比， 具有省时高效的优势. 并通过电子能谱仪、热重分析仪、场发射扫描电子显微镜表征这种前聚体的形态与组成. 在有关电子顺磁共振波谱(ESR)和发光光谱(PL)的实验中，ESR和PL用来研究和表征Mn2+掺杂效率及ZnSe前驱体纳米带中Mn2+-Mn2+的相互作用.Mn掺杂ZnSe前驱体纳米带的ESR谱出现Mn2+特征超精细分裂六重峰，表明了Mn2+-Mn2+的     

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     

掺钴氧化锌稀磁半导体的SEM及X射线能谱微分析研究

采用水热法,以CoCl₂·6H₂O为前驱物,KOH作为矿化剂合成了掺钴氧化锌稀磁半导体晶体。利用扫描电子显微镜(SEM)及X射线能谱仪(XREDS)对合成晶体的微观形貌、表面及内部掺杂元素Co的相对含量和分布的均匀性进行了研究。研究结果表明：水热法合成的掺Co氧化锌晶体具有多种微观形貌,较大的晶体具有极性生长特性。随晶体形貌不同,显露面也发生了相应改变。不同微观形貌的晶体其Co含量有所差异,较大的晶体掺杂Co元素相对含量大于较小的晶体,+c(1011)显露面Co元素的含量比+c(1010)面高,锥柱状晶体其区别尤为明显。大的晶体内部存在着少量的氧化钴团簇,晶体表面与晶体内部Co元素分布相对均匀。由于Co2+具有磁性,因此,氧化钴团簇的存在将对氧化锌稀磁半导体晶体的磁性产生一定的影响。     

稀磁半导体Zn1-xFexO纳米颗粒的光谱研究

利用水热法制备了Zn1-xFexO(x=0,0.01,0.05,0.10和0.20)纳米稀磁半导体材料。由X射线衍射图谱的结果表明,制备的Zn1-xFexO样品为纤锌矿结构,没有金属铁等第二相出现;高分辨透射电子显微镜的结果表明,形貌为分散性良好的纳米颗粒,晶格清晰;拉曼光谱结果表明(E2High)峰位向高频移动,半高宽宽化,峰强减弱;光致发光光谱结果表明,随着Fe离子的掺入,紫外峰向低能移动,光致发光光谱发生了猝灭现象;UV-Vis光谱可看出,光学带隙减小,发生了红移现象。这些结果表明Fe3+成功替代Zn2+进入到ZnO晶格。     

H掺杂对ZnCoO稀磁半导体薄膜结构及磁性能的影响

利用磁控溅射法,采用亚分子分层掺杂技术交替溅射Co靶和ZnO靶,在Si衬底上制备了不同氢氩流量比的H:ZCO薄膜样品,研究了氢氩流量比对薄膜结构特性和磁学性能的影响。所制备的薄膜样品具有c轴择优取向。由于H对表面和界面处悬挂键的钝化作用,随H₂流量比的增加,薄膜的择优取向变差。磁性测量结果显示,薄膜样品的铁磁性随着氢氩流量比的增大而增强。XPS结果表明,随着H含量的增大,金属态Co团簇的相对含量逐渐增加,而氧化态Co离子的相对含量逐渐减小。H:ZCO样品中的铁磁性可能来源于Co金属团簇,H的掺入促使ZnO中的Co离子还原成Co金属团簇,从而增强了薄膜样品的室温铁磁性。     

Magnetic properties of Mn-doped ZnO diluted magnetic semiconductors

A series of Mn-doped ZnO films have been prepared in different sputtering plasmas by using the inductively coupled plasma enhanced physical vapour deposition. The films show paramagnetic behaviour when they are deposited in an argon plasma. The Hall measurement indicates that ferromagnetism cannot be realized by increasing the electron concentration. However, the room-temperature ferromagnetism is obtained when the films are deposited in a mixed argon-nitrogen plasma. The first-principles calculations reveal that antiferromagnetic ordering is favoured in the case of the substitution of Mn^2＋ for Zn^2＋ without additional acceptor doping. The substitution of N for O （NO^-） is necessary to induce ferromagnetic couplings in the Zn-Mn-O system. The hybridization between N 2p and Mn 3d provides an empty orbit around the Fermi level. The hopping of Mn 3d electrons through the empty orbit can induce the ferromagnetic coupling. The ferromagnetism in the N-doped Zn-Mn-O system possibly originates from the charge transfer between Mn^2＋ and Mn^3＋ via NO^-, The key factor is the empty orbit provided by substituting N for O, rather than the conductivity type or the carrier concentration.     

Synthesis of Mn-doped ZnO diluted magnetic semiconductors in the presence of ethyl acetoacetate under solvothermal conditions

Mn-doped ZnO samples with 5%, 20% and 40% nominal Mn concentrations were prepared in the presence of ethyl acetoacetate under solvothermal conditions. UV absorption spectroscopic analysis discloses that chemical modification was achieved by reaction of Zn or Mn precursor with ethyl acetoacetate in ethanol medium. XRD and HRTEM characterizations indicate that ZnMnO₃ impurity phase was formed in the 20% and 40% Mn-doped ZnO samples while no secondary phase was present in the 5% Mn-doped sample. The 5% Mn-doped sample consists of spheroid-like particles with size of 10-50 nm and has a real Mn concentration of 3.2%. Ferromagnetism and paramagnetism coexist in the 5% Mn-doped ZnO sample at room-temperature, which may arise from ferromagnetic exchange interaction as well as small secondary phases. The 20% and 40% Mn-doped samples show large paramagnetic effects at room temperature. Small paramagnetic secondary phases and clustering of Mn are probably responsible for this.     

ZnCoO稀磁半导体的室温磁性

采用固相反应法，将ZnO和Co₂O₃粉末按不同的成分配比混合，制备了稀磁半导体Zn_1-xCo_xO (x=0.02,0.06,0.10)材料.并使用H₂气氛退火技术对样品进行了处理，得到了具有室温铁磁性的掺Co氧化锌稀磁半导体.利用全自动X射线衍射仪、X射线光电子能谱仪、高分辨透射电子显微镜和超导量子干涉器件磁强计对样品的结构、晶粒的尺寸、微观形貌以及磁性等进行了测量和标度. 关键词： 稀磁半导体 氧化锌 掺杂 固相反应法     

Structural and magnetic studies on Zr doped ZnO diluted magnetic semiconductor

In this study, Zirconium doped Zn_1−xZr_xO (with x = 0.00–0.10) samples have been prepared by formal solid-state reaction technique. The Zr doped ZnO samples annealed at 1100 °C and characterized by different characterization techniques, such as X-ray diffraction (XRD), Scanning electron microscope (SEM), Vibrating sample magnetometer (VSM) and Fourier transform infrared spectroscopy (FTIR). The X-ray diffraction (XRD) used to study the structural properties. XRD pattern showed that lattice parameters, “a”, “c”, unit cell volume and Zn–O bond length increase with doping content (x ≤ 0.04) where as these decrease with x > 0.04. On the other hand, reverse trend observed with lattice distortion. The crystallite size decreases with increasing doping content of Zr. FTIR employed to investigate functional chemical bonding properties of different elements and compounds present in materials. The low, medium and high frequency absorption bands observed at 630, 1500 and 3435 cm⁻¹, which were the common features of Zn–O, H–O–H and O–H bond respectively. SEM used to study surface morphology and measured grain size of specimen. The surface becomes dense and grain size decreases with increasing degree of Zr contents. The SEM micrograph also shows the presence of spherical micro size particles and formation of pores in samples. Magnetic properties were obtained using VSM. The samples exhibit room temperature ferromagnetism. The magnetic hysteresis loops show variation in the value of magnetic parameter. The saturation magnetization (M_s) and coercivity (H_c) decrease, while remanence magnetization (M_r) shows gradually increasing trend with Zr content. VSM measurement reveals that sample Zn_0.96Zr_0.4O show better result as compared to x = 0.06–0.10.     

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     

新型稀磁半导体Mn掺杂LiZnAs的第一性原理研究

采用基于密度泛函理论的第一性原理平面波超软赝势方法, 对纯LiZnAs, Mn掺杂的LiZnAs, Li过量和不足下Mn掺杂的LiZnAs体系进行几何结构优化, 计算并对比分析了体系的电子结构、半金属性、光学性质及形成能.结果表明新型稀磁半导体Li (Zn_0.875Mn_0.125) As, Li_1.1 (Zn_0.875Mn_0.125) As和Li_0.9 (Zn_0.875Mn_0.125) As均表现为100%自旋注入, 材料均具有半金属性, Li过量和不足下体系的半金属性明显增强. Li过量可以提高体系的居里温度, 改善材料的导电性, 使体系的形成能降低. 说明LiZnAs半导体可以实现自旋和电荷注入机理的分离, 磁性和电性可以分别通过Mn的掺入和Li的含量进行调控. 进一步对比分析光学性质发现, 低能区的介电函数虚部和复折射率函数明显受到Li的化学计量数的影响. 关键词： Mn掺杂LiZnAs 电子结构 光学性质 第一性原理     

Structural and magnetic properties of Mn-doped ZnO powders

A mixture of bi(acetylacetonato) zinc(II)hydrate and tris(acetylacetonato) manganese(III) complexes was thermally co-dissociated to synthesize Mn-doped ZnO powders. In order to examine the effect of oxygen vacancies on the ferromagnetic coupling of Mn ions, two preparation routes were used: in route (I) the preparation was done in an open environment, whereas in route (II) the preparation was done in a closed environment. The X-ray diffraction (XRD) and the X-ray fluorescence (XRF) measurements indicate that the Mn content in the three samples are 3.9% (I), 3.3% (II) and 4.2% (II). The XRD results showed that the Mn ions were incorporated in the ZnO crystal and that a Zn_1−xMn_xO solid solution has formed. The magnetic characterization indicated that only samples prepared via route (II) exhibited a room temperature ferromagnetic component of magnetization. Furthermore, magnetic analysis showed that the magnetic moment per dopant ion in the samples examined was in the range of 4.2-6.1 μ_B/Mn. The percentages of coupled Mn atoms to the total number of Mn atoms were found to be extremely small (less than 0.1%), which by itself cannot explain the observed RT hysteresis loops. Thus, in order to produce long-range ferromagnetic order in these samples, the FM coupling has to be mediated via defects. The observed FM in this study may be attributed to the presence of oxygen vacancies, which mediate the ferromagnetic exchange between the coupled Mn ions. This is consistent with the bound magnetic polarons (BMP) model where defects like oxygen vacancies cause the polarons to overlap and give rise to a long-range ferromagnetic order in dilute magnetic semiconductors (DMS).     

The structure and magnetic properties of Cu-doped ZnO prepared by sol-gel method

The Cu-doped ZnO and pure ZnO powders were synthesized by sol-gel method. The structural properties of the samples were investigated by X-ray diffraction, Raman spectroscopy, X-ray photoelectron spectroscopy and X-ray absorption spectroscopy. All the results confirmed that copper ions were well incorporated into the ZnO lattices by substituting Zn sites without changing the wurtzite structure and no secondary phase existed in Cu-doped ZnO nanoparticles. The Zn_0.97Cu_0.03O nanoparticles exhibited ferromagnetism at room temperature, as established by the vibrating sample magnetometer analysis.     

微型计算机在脉冲磁场作用下的效应试验

介绍了脉冲强磁场模拟器的工作原理, 将微型计算机置于脉冲磁场模拟器中,通过改变脉冲磁场的幅度和上升时间,研究脉冲磁场对微电子设备的干扰途径、干扰阈值与脉冲上升时间、脉冲宽度的关系。试验结果表明,微电子设备的连接电缆是脉冲磁场干扰引入的主要途径;简单的屏蔽措施对于脉冲磁场干扰有一定的抑制作用;脉冲磁场的时间变化率越大,对微电子设备的干扰作用越强。