Ⅲ—V族磁半导体材料的研究与发展

Mn、Fe等过渡金属元素的Ⅲ-V族磁半导体（DMS）材料和铁磁/半导体异质结材料由于具备半导体和磁性材料的综合特性，可望广泛应用于未来的磁（自旋）电子器件，从而使传统的电子工业面临一场新的技术革命。本文将对上述研究领域进行评述。     

稀磁半导体异质结构的自旋极化输运性质

采用格林函数方法和群速近似研究在电场、磁场作用下电子渡越稀磁半导体异质结构的自旋过滤及自旋分离的特征。研究表明具有不同自旋指向的极化电子渡越同一稀磁半导体异质结构 ,不仅隧穿几率存在着显著的差异 ,而且渡越时间的差异可达几个数量级。这种差异随着外磁场的增强而加大 ,而随外电场的增强而减小。结果意味着稀磁半导体异质结构具有很好的自旋过滤效果 ,且极化电子渡越此类结构在时间上是分离的     

稀土掺杂GaN基稀磁半导体材料的研究进展

GaN基稀磁半导体材料具有高于室温的铁磁性和优异的光电性能,在半导体电子自旋器件领域有广阔的应用前景。系统地介绍了制备方法对稀土Gd掺杂GaN基稀磁半导体材料铁磁性的影响,讨论了Gd掺杂GaN基稀磁半导体材料中铁磁性的起源,介绍了除Gd以外的稀土离子掺杂GaN基稀磁半导体材料中的铁磁性,以及共掺杂对GaN基稀磁半导体材料的铁磁性能的影响。目前,GaN基稀磁半导体材料的铁磁性仍无法满足半导体电子自旋器件的要求。共掺杂工艺可以有效地解决稀土离子掺杂引入的较大晶格应变,促进自旋电子之间的交互作用,是一种改善GaN基稀磁半导体材料的铁磁性能的有效途径。     

半导体自旋电子学的研究与应用进展

自旋电子学是一门最新发展起来的涉及磁学、电子学以及信息学的交叉学科.自旋电子器件与普通半导体电子器件相比具有不挥发、低功耗和高集成度等优点.本文介绍了半导体自旋电子学的研究对象和内容,主要包括磁性半导体、自旋注入、自旋探测以及自旋输运等.本文综述了半导体自旋电子学目前的研究进展及其在自旋电子器件和量子信息处理中的应用.     

SiC稀磁半导体材料研究进展

稀磁半导体(DMS)材料同时利用了电子的电荷和自旋属性,具有优异的磁、磁光、磁电等性能,在材料科学和未来自旋电子器件领域具有广阔的应用前景。系统地概述了SiC基DMS材料的研究进展,介绍了材料的制备方式、结构、性质、铁磁性起源的机理以及器件潜在的应用前景。结合本实验小组的研究工作,重点阐述了材料的结构以及磁性机制。     

铁磁/半导体异质结材料MnSb/Si的物理气相沉积生长

采用一种新的生长铁磁/半导体异质结材料的方法--物理气相沉积方法生长了一种铁磁/半导体异质结材料MnSb/Si.对所获得的样品进行特征X射线能谱分析表明Mn和Sb在Si衬底上的沉积速率相近,它们的原子百分数之比接近1∶1.X射线衍射分析发现薄膜中形成了MnSb相,样品在室温下测出磁滞回线也从侧面验证了存在MnSb相.用原子力显微镜对样品的表面进行观察,发现MnSb呈有规则形状的小晶粒状,晶粒大小比较均匀,尺寸大多数在500nm左右.     

铁磁/半导体异质结材料MnSb/Si的物理气相沉积生长

采用一种新的生长铁磁/半导体异质结材料的方法——物理气相沉积方法生长了一种铁磁/半导体异质结材料Mn Sb/Si.对所获得的样品进行特征X射线能谱分析表明Mn和Sb在Si衬底上的沉积速率相近,它们的原子百分数之比接近1∶1.X射线衍射分析发现薄膜中形成了Mn Sb相,样品在室温下测出磁滞回线也从侧面验证了存在Mn Sb相.用原子力显微镜对样品的表面进行观察,发现Mn Sb呈有规则形状的小晶粒状,晶粒大小比较均匀,尺寸大多数在5 0 0 nm左右.     

基于4H-SiC衬底的(SiFe)C的稀磁半导体材料制备

研究了基于4H-SiC衬底的(SiFe)C的稀磁半导体材料制备方法,不同于其他人采用的MBE或MOCVD生长的方法,用离子注入的方法进行材料制备,能够与现有的集成电路工艺相兼容,用这种方法所对应的样品的居里温度320K,高于室温,具有潜在应用的价值.在制备过程中,采用了HNH退火工艺,即退火分为三个阶段,每个阶段对应不同的退火气氛、时间和温度,XRD分析表明,每个阶段都对应不同的结晶结果.另外,对应不同的Fe离子浓度,进行了实验对比,结果表明,当x=0.051的情况下对应最高的居里温度.     

基于4H-SiC衬底的(SiFe)C的稀磁半导体材料制备

研究了基于4H-SiC衬底的(SiFe)C的稀磁半导体材料制备方法,不同于其他人采用的MBE或MOCVD生长的方法,用离子注入的方法进行材料制备,能够与现有的集成电路工艺相兼容,用这种方法所对应的样品的居里温度320K,高于室温,具有潜在应用的价值.在制备过程中,采用了HNH退火工艺,即退火分为三个阶段,每个阶段对应不同的退火气氛、时间和温度,XRD分析表明,每个阶段都对应不同的结晶结果.另外,对应不同的Fe离子浓度,进行了实验对比,结果表明,当x=0.051的情况下对应最高的居里温度.     

Growth and Characterization of Diluted Magnetic Cr-Doped InAs Self-Organized Quantum Dots

Cr-doped InAs self-organized ferromagnetic quantum dots(QDs)were grown on GaAs(001) substrate by low-temperature molecular·beam epitaxy.High-resolution transmission electron microscopy(HRTEM)analyses show that the I. nAs：Cr quantum。dots layers remain zinc blende structure well.Magnetic measurements demonstrate that the ferromagnetic transition temperature exceeds 400K in InAs：Cr self-organized ODs.     

稀磁半导体ZnX∶Co2+光磁性质的双共价因子和双ξ模型

考虑到d电子t2g轨道与eg轨道局域性的差异,用双共价因子研究了掺Co2+的共价晶体ZnX(X=S,Se)的光学吸收谱.在研究顺磁g因子时,除考虑中心离子的旋-轨耦合贡献外,还计及配体的旋-轨耦合贡献(双ξ模型).研究表明,计算结果与实验值吻合得很好,对于一些共价性较强的化合物晶体,该方法更加有效.     

Progress on microscopic properties of diluted magnetic semiconductors by NMR and μSR

Diluted magnetic semiconductors (DMSs) that possess both properties of semiconductors and ferromagnetism, have attracted a lot of attentions due to its potential applications for spin-sensitive electronic devices. Recently, a series of bulk form DMSs isostructural to iron-based superconductors have been reported, which can be readily investigated by microscopic experimental techniques such as nuclear magnetic resonance (NMR) and muon spin rotation (μSR). The measurements have demonstrated that homogeneous ferromagnetism is achieved in these DMSs. In this review article, we summarize experimental evidences from both NMR and μSR measurements. NMR results have shown that carriers facilitate the interactions between distant Mn atoms, while μSR results indicate that these bulk form DMSs and (Ga,Mn)As share a common mechanism for the ferromagnetic exchange interactions.     

Advances in new generation diluted magnetic semiconductors with independent spin and charge doping

As one branch of spintronics, diluted magnetic semiconductors (DMSs) are extensively investigated due to their fundamental significance and potential application in modern information society. The classical materials (Ga,Mn)As of III–V group based DMSs has been well studied for its high compatibility with the high-mobility semiconductor GaAs. But the Curie temperature in (Ga,Mn)As film is still far below room temperature because the spin &; charge doping is bundled to the same element that makes the fabrication very difficult. Alternatively, the discovery of a new generation DMSs with independent spin and charge doping, such as (Ba,K)(Zn,Mn)₂As₂ (briefly named BZA), attracted considerable attention due to their unique advantages in physical properties and heterojunction fabrication. In this review we focus on this series of new DMSs including (I) materials in terms of three types of new DMSs, i.e. the " 111”, " 122” and " 1111” system; (II) the physical properties of BZA; (III) single crystals &; prototype device based on BZA. The prospective of new type of DMSs with independent spin and charge doping is briefly discussed.     

稀磁半导体(Ga1-xFex)As的磁性及稳定性

运用第一性原理下的LMTO-ASA方法研究稀磁半导体(Ga1-xFe x )As( x ＝1,1/2,1/4和1/8)的电子结构、磁性及其稳定性.计算了Fe掺杂浓度的变化对(Ga1-xFe x )As的磁性及稳定性的影响.     

稀磁半导体(Ga_(1-x)Fe_x)As的磁性及稳定性

运用第一性原理下的LMTO-ASA方法研究稀磁半导体(Ga1-xFex)As(x=1,1/2,1/4和1/8)的电子结构、磁性及其稳定性.计算了Fe掺杂浓度的变化对(Ga1-xFex)As的磁性及稳定性的影响.     

Room Temperature Ferromagnetismin Co-doped ZnO Bulks

Pure single phase of Zn0.95Co0.05O bulks were successfully prepared by solidstate reaction method.The effects of annealing atmosphere and temperature on the room temperature ferromagnetic behavior were investigated. The results show that the airannealed samples has similar weak ferromagnetic behavior with the assintered samples, but the obvious ferromagnetic behavior is observed for the samples annealed in vacuum or Ar/H2 gas, indicating that the strong ferromagnetism is associated with high oxygen vacancies density. High saturation magnetization Ms=0.73 μB/Co and eoercivity Hc=233.8Oe are obtained for the Ar/H2 annealed samples with pure single phase structure when annealing temperature is 600 ℃.