Synthesis, Structure and Magnetic Properties of III-V Ferromagnetic Semiconductors

III-V族铁磁半导体的合成、结构及磁性能

• 批准号: 0511523
• 负责人: Bruce Wessels
• 金额: --
• 依托单位: Northwestern University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2005
• 资助国家: 美国
• 起止时间: 2005-07-01 至 2008-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0511523&HistoricalAwards=false
• 关键词: Synthesis; Structure; Magnetic; Properties; III

Technical. Intellectual merit: The development of ferromagnetic III-V semiconductors has provided the potential for a new class of multifunctional materials that exhibit magnetic, magneto-optical and semiconducting properties. These materials offer the potential for manipulating both spin and charge. Their utilization, however, has been impeded due to their low transition (Curie) temperatures. Recently there have been reports of ferromagnetic semiconductors with Curie temperatures in excess of 300 K. The PI has shown that InMnAs alloys prepared by metalorganic vapor phase epitaxy (MOVPE) exhibit a Curie temperature of 330 K. His recent research indicates that atomic clusters are responsible for the enhanced Curie temperature. The question arises as to the detailed mechanism for stabilizing the high temperature ferromagnetic phase and what is the nature of the magnetic species. In the proposed program In based III-V ferromagnetic semiconductor thin films will be studied including InMnAs, InMnSb, InMnP and their solid solutions. Of specific interest is what role do transition metal atomic clusters play in stabilizing high temperature ferromagnetism in these semiconductors and what is the nature of the short range order. The role of free carrier concentration on the ferromagnetic phase stability will also be examined. It is planned to determine whether or not other In based III-V compounds can be synthesized by MOVPE with Curie temperature in excess of 400 K as predicted by recent theory. In this project, epitaxial thin alloy films will be synthesized by metalorganic vapor phase epitaxy. Semiconductor alloys with different band gaps will be prepared to determine the role that band mixing, impurity ionization energy and degree of carrier localization play in stabilizing ferromagnetism. Experimental characterization techniques to be used include high resolution transmission electron microscopy, temperature and field dependent magnetization measurements, Hall effect and magnetoresistance. The magneto-optical Kerr effect (MOKE) and its spectral dependence over infra-red to visible region will be used to determine the nature and magnitude of the exchange interaction in the alloys. Extended x-ray fine structure analysis (EXAFS) and a local electrode atom probe with atomic scale resolution will be used to determine cluster size and distribution. X-ray absorption spectroscopy and x-ray magnetic circular dichroism (XMCD) at the Advanced Photon Source will be used to determine the magnetic properties of the elements comprising the alloys. X-ray photo-electron electron microscopy (PEEM) at Argonne will be used in conjunction with temperature dependent magnetic force microscopy to determine magnetic domain structure and stability. Non-Technical. Broader impact: The project will involve the training of graduate and undergraduate students in the synthesis and property measurements on ferromagnetic semiconductors. Students will also be involved in synchrotron studies at Argonne. These materials have potential technological importance for new types of spin devices such as spin valves, magnetic random access memories and quantum computation devices.

技术.智力优点：铁磁III-V族半导体的发展为一类新的多功能材料提供了潜力，这些材料具有磁性，磁光和半导体特性。这些材料提供了操纵自旋和电荷的潜力。然而，由于它们的低转变（居里）温度，它们的利用受到阻碍。最近有报道称铁磁半导体的居里温度超过300 K。PI表明，通过金属有机气相外延（MOVPE）制备的InMnAs合金的居里温度为330 K。他最近的研究表明，原子团簇是提高居里温度的原因。出现的问题，作为稳定的高温铁磁相的详细机制，是什么性质的磁性物种。在所提出的计划中，将研究In基III-V族铁磁半导体薄膜，包括InMnAs，InMnSb，InMnP及其固溶体。特别感兴趣的是过渡金属原子团簇在稳定这些半导体中的高温铁磁性方面起什么作用，以及短程有序的性质是什么。自由载流子浓度对铁磁相稳定性的作用也将被检查。计划确定是否可以通过MOVPE合成居里温度超过400 K的其他In基III-V族化合物，如最近的理论所预测的。在本计画中，将利用金属有机物气相磊晶法来合成磊晶薄合金薄膜。将制备具有不同带隙的半导体合金，以确定能带混合、杂质电离能和载流子局域化程度在稳定铁磁性中的作用。将使用的实验表征技术包括高分辨率透射电子显微镜，温度和磁场相关的磁化测量，霍尔效应和磁阻。磁光克尔效应（MOKE）及其在红外到可见光区域的光谱依赖性将用于确定合金中交换相互作用的性质和大小。扩展的X射线精细结构分析（EXAFS）和原子尺度分辨率的局部电极原子探针将用于确定簇的大小和分布。先进光子源的X射线吸收光谱和X射线磁性圆二色性（XMCD）将用于确定组成合金的元素的磁性。在阿贡的X射线光电子显微镜（PEEM）将与温度相关的磁力显微镜一起使用，以确定磁畴结构和稳定性。非技术性。更广泛的影响：该项目将涉及对研究生和本科生进行铁磁半导体合成和性能测量方面的培训。学生们还将参与在阿贡的同步加速器研究。这些材料对于新型自旋器件如自旋阀、磁性随机存取存储器和量子计算器件具有潜在的技术重要性。