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.

技术支持：铁磁、III-V族半导体的发展为一类具有磁性、磁光和半导体性质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。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起着至关重要的作用。出现的问题，作为稳定的高温铁磁相和磁性物种的性质的详细机制。本计画将开发窄禁带铟基Ⅲ-Ⅴ族铁磁半导体薄膜，包括InMnAs与InMnSb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和短程有序的性质中起什么作用。此外，自由载流子浓度对铁磁相稳定性的作用将被检查。在该项目中，外延薄合金薄膜将通过金属有机气相外延（MOVPE）合成。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。最近的模型的基础上形成的铁磁集团的旋节分解将进行测试。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）及其在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大小。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。扩展X射线精细结构分析（EXAFS），分析电子显微镜，和电极原子探针与原子尺度分辨率将用于确定集群的大小和分布。非技术性：该项目致力于解决材料科学领域的基础研究问题，并有望提供对铁磁半导体材料的科学理解，以及对自旋阀、磁性随机存取存储器和量子计算等自旋器件的潜在应用。该项目为研究生和本科生提供跨学科主题的培训，包括半导体物理学和磁学。该项目还包括对当地学校开展教育外联活动，并与国家实验室合作，为学生提供更多的学习机会。