Study of Diffusion of Magnetic Ions in Semiconductor Heterostructures and Its Effect on Spin Injection

技术：许多目前研究的自旋电子学器件涉及从铁磁材料到半导体的自旋注入。最近的研究表明，当在GaAs或Si上生长含Mn和Fe的铁磁金属时，会发生显著的扩散。也有最近的报告显示自旋极化载流子注入到晶体结构后的自旋散射的证据。因此，重要的是系统地研究这个问题，以便可以改进注射结果的分析。该项目的重点是磁性离子在大多数研究系统，即Fe/GaAs，FeCo/GaAs，MnAs/GaAs和GaMnAs/GaAs中的扩散，以及涉及硅的选定结构。样品是用分子束外延生长的。使用飞行时间的第二离子质谱和横截面扫描隧道显微镜的扩散分布确定。扩散的磁性离子对自旋注入的影响主要由自旋发光二极管结构确定，该结构在确定注入电子的自旋极化水平方面是有效的。这项研究的目的是提供有关的档案的扩散磁性离子在半导体的自旋注入，和他们的影响的定量信息。通过检查扩散作为温度的函数通过退火，人们能够把上限的生长和器件加工温度。该项目还探讨了抑制磁性离子扩散过程的可能性。非技术性：这项科学工作可能对未来几代信息技术的发展产生重大影响。它解决了一个共同的问题，存在于大多数研究的自旋效应，涉及运输的自旋极化电流从一种材料到另一种。这将包括自旋发光二极管、自旋激光器、自旋阀和其他涉及铁磁材料的更复杂的自旋逻辑器件的研究。该项目还有助于培养下一代科学家，增加了另一个场地，为三名研究人员的学生提供跨学科培训，这三名研究人员长期以来一直为物理和化学研究生提供咨询。此外，该项目还涉及到布法罗的美洲土著磁铁学校（K-8），并在早期阶段让美洲土著和非洲裔美国学生学习科学和工程。

Technical: Many currently studied spintronics devices involve spin injection from ferromagnetic materials into nonmagnetic semiconductors. Recent studies show that significant diffusion occurs when Mn and Fe containing ferromagnetic metals are grown on GaAs or Si. There are also recent reports showing evidence of spin scattering after spin-polarized carriers are injected into nonmagnetic structures. It is therefore important to investigate this problem systematically, so that the analysis of injection results can be improved. This project focuses on diffusion of magnetic ions in the most studied systems, namely Fe/GaAs, FeCo/GaAs, MnAs/GaAs and GaMnAs/GaAs, and on selected structures involving silicon. The samples are grown by molecular beam epitaxy. Diffusion profiles are determined using time-of-flight second ion mass spectroscopy and cross sectional scanning tunneling microscopy. The effect of diffused magnetic ions on spin injection is primarily determined with spin light emitting diode structures, which have been effective in determining the level of spin polarization of the injected electrons. The study is designed to provide quantitative information concerning the profile of diffused magnetic ions in nonmagnetic semiconductors, and their effect on spin injection. By examining diffusion as a function of temperature through annealing, one is able to put upper limits on growth and device processing temperatures. The project also explores the possibility of suppressing diffusion processes for the magnetic ions.Non-technical: This scientific work could have a significant impact on the development of future generations of information technology. It addresses a common issue that exists in most studies of spin effects involving transport of spin polarized currents from one material to another. This would include studies of spin light emitting diodes, spin lasers, spin valves and other more complicated spin-logic devices that involve ferromagnetic materials. The project also contributes to training the next generation of scientists by adding another venue to provide interdisciplinary training to students for the three investigators who have a long history of jointly advising graduate students in physics and chemistry. In addition, the project involves outreach to the Native American Magnet School (K-8) in Buffalo and engages, at an early stage, Native American and African American students in sciences and engineering.