Synthesis, Structure and Properties of III-V Ferromagnetic Semiconductor Thin Films

III-V族铁磁半导体薄膜的合成、结构与性能

• 批准号: 0804479
• 负责人: Bruce Wessels
• 金额: $ 44.6万
• 依托单位: Northwestern University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2008
• 资助国家: 美国
• 起止时间: 2008-07-01 至 2012-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0804479&HistoricalAwards=false
• 关键词: Synthesis; Structure; Properties; III; Ferromagnetic

Technical: The development of ferromagnetic, group III-V semiconductors has provided the potential for a 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. There is growing evidence that disorder plays an essential role in stabilizing ferromagnetism in certain ferromagnetic semiconductors. The question arises as to the detailed mechanism for stabilizing the high temperature ferromagnetic phase and the nature of the magnetic species. In this project, narrow bandgap indium based III-V ferromagnetic semiconductor thin films will be developed, including InMnAs and InMnSb and their solid solutions. Of specific interest is what role transition metal atomic clusters play in stabilizing high temperature ferromagnetism in these semiconductors and the nature of the short range order. Furthermore the role of free carrier concentration on the ferromagnetic phase stability will be examined. During the project, epitaxial thin alloy films will be synthesized by metalorganic vapor phase epitaxy (MOVPE). Semiconductor alloys with different manganese concentrations will be prepared to determine the role disorder plays in stabilizing ferromagnetism. Recent models based on spinodal decomposition forming ferromagnetic clusters will be tested. Experimental characterization techniques to be used include temperature and field dependent magnetization measurements, Hall effect, and magnetoresistance. The magneto-optical Kerr effect (MOKE) and its spectral dependence over the mid infrared to visible region will be used to determine the nature and magnitude of the exchange interaction in the alloys. 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. Extended x-ray fine structure analysis (EXAFS), analytical electron microscopy, and an electrode atom probe with atomic scale resolution will be used to determine cluster size and distribution. Comparisons will be made between cluster sizes determined by structural and magnetic measurements.Non-technical: The project addresses basic research issues in a topical area of materials science with high technological relevance, and is expected to provide scientific understanding of ferromagnetic semiconductor materials with potential applications for spin based devices such as spin valves, magnetic random access memories, and quantum computation. The project provides training of graduate and undergraduate students in an interdisciplinary topic, consisting of semiconductor physics and magnetism. The project also includes educational outreach activities to local schools and collaboration with national laboratories, which provide enhanced learning opportunities to students.

技术：铁磁 III-V 族半导体的发展为一类具有磁性、磁光和半导体特性的多功能材料提供了潜力。这些材料提供了操纵自旋和电荷的潜力。然而，由于转变（居里）温度较低，它们的利用受到了阻碍。最近有报道称铁磁半导体的居里温度超过 300 K。越来越多的证据表明，无序在稳定某些铁磁半导体的铁磁性方面发挥着重要作用。问题在于稳定高温铁磁相的详细机制和磁性物质的性质。该项目将开发窄带隙铟基III-V铁磁半导体薄膜，包括InMnAs和InMnSb及其固溶体。特别令人感兴趣的是过渡金属原子团簇在稳定这些半导体的高温铁磁性方面发挥的作用以及短程有序的性质。此外，还将研究自由载流子浓度对铁磁相稳定性的作用。该项目期间，将通过金属有机气相外延（MOVPE）合成外延合金薄膜。将制备具有不同锰浓度的半导体合金，以确定无序在稳定铁磁性中所起的作用。将测试基于形成铁磁簇的旋节线分解的最新模型。所使用的实验表征技术包括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）及其对中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幅度。先进光子源的 X 射线吸收光谱和 X 射线磁圆二色性 (XMCD) 将用于确定合金元素的磁性。扩展 X 射线精细结构分析 (EXAFS)、分析电子显微镜和具有原子级分辨率的电极原子探针将用于确定簇的大小和分布。将比较由结构和磁性测量确定的簇大小。非技术性：该项目解决了具有高技术相关性的材料科学主题领域的基础研究问题，预计将提供对铁磁半导体材料的科学理解，以及自旋阀、磁性随机存取存储器和量子计算等基于自旋的器件的潜在应用。该项目为研究生和本科生提供跨学科主题的培训，包括半导体物理和磁学。该项目还包括对当地学校的教育外展活动以及与国家实验室的合作，为学生提供更多的学习机会。