Electron Spin Effects in Semiconductor Nanostructures

目前，除了电子在当代电子学中的电荷外，还有一个激烈的全球运动，探索电子自旋（电子的量子力学磁性）的作用，着眼于增加电子微芯片设备的功能，特别是在计算领域。该奖项支持一个旨在解决这一问题的项目，该项目采用最先进的技术制造和表征一系列新型半导体纳米级结构，其中通过结合磁性离子增强电子自旋的作用。通过在尖端半导体制造技术以及设计多功能材料方面培训研究生和本科生，该项目有望产生广泛的影响，远远超出其直接的纯科学目标。美国工业、国家实验室和学术界对这些材料科学领域的技能有着广泛的需求。此外，圣母大学的研究小组与许多科学家合作（目前与超过35个其他机构合作），要么提供研究样本，要么进行联合实验。随着在本项目过程中开发出新的基于自旋的电子材料，这种传播和分享成果和专门知识的活动（使学生接触到机构间和跨学科团队合作的额外好处）预计将进一步扩大。技术摘要：本基金支持一个研究低维磁性半导体系统中自旋现象的两个新的互补领域的项目。(a)研究铁磁半导体在其尺寸接近纳米尺寸时性质的变化；(b)对磷化基FM半导体（如GaMnP和InMnP）的生长和性能进行探索性研究。区域(a)的动机是这样一种期望，即当磁性半导体（如GaMnAs）的物理尺寸接近纳米尺度并变得与铁磁畴壁的宽度或自由载流子耗尽长度相当时，其磁性能将发生显著变化。考虑到调频半导体器件在纳米技术中的应用，这一点变得尤为重要。利用分子束外延（MBE）和光刻技术，圣母大学团队提议通过磁化测量、磁输运、磁光研究和铁磁共振来探索这种缩小尺寸的后果。区域(b)的重点是对磷化铁磁半导体的MBE生长进行全面研究，然后对其基于自旋的特性进行系统研究。尽管GaMnP、InMnP和GaMnAsP等合金的自旋特性被认为是非常有前途的，并提供了一系列重要的新机会，但令人惊讶的是，与GaMnAs或InMnAs合金相比，在这类材料上所做的工作很少。将提出的研究扩展到这个新的调频半导体家族，预计将大大提高对铁磁半导体的理解。

NON-TECHNICAL ABSTRACTThere is currently an intense worldwide movement to explore the role of the electron spin (a quantum-mechanical magnetic property of the electron) in addition to the electron's charge in contemporary electronics, with an eye on increasing the functionality of electronic microchip devices, particularly in the realm of computation. This award supports a project aimed at addressing this issue by employing state-of-the-art techniques to fabricate and characterize a series of novel semiconductor nanometer scale structures in which the role of the electron spin is enhanced by incorporating magnetic ions. By training graduate and undergraduate students in cutting-edge semiconductor fabrication techniques as well as in designing multi-functional materials, the project is expected to have broad impact far beyond its immediate purely scientific goals. Skills in these areas of materials science are in wide demand in U.S. Industry, National Laboratories, and Academia. Additionally, the Notre Dame team collaborates with many scientists (currently with more than thirty-five other institutions) either by providing research samples or by carrying out joint experiments. This activity of dissemination and sharing of results and know-how (which has the added benefit of exposing students to inter-institutional and inter-disciplinary team collaborations) is expected to further expand as new spin-based electronic materials are developed in the course of the present project. TECHNICAL ABSTRACTThis grant supports a project that focuses on two new but complementary areas involving spin phenomena in low-dimensional magnetic semiconductor systems. (a) The study of changes in the properties of ferromagnetic (FM) semiconductors as their size approaches nanometer dimensions; and (b) exploratory research on growth and properties of phosphide-based FM semiconductors, such as GaMnP and InMnP. Area (a) is motivated by the expectation that, as the physical size of a magnetic semiconductor such as GaMnAs approaches the nanometer scale and becomes comparable to, e.g., the width of ferromagnetic domain walls or the free carrier depletion length, its magnetic properties will significantly change. This becomes especially important as one considers applications of FM semiconductor devices in nanotechnology. Using molecular beam epitaxy (MBE) followed by lithographic techniques, the Notre Dame team proposes to explore the consequences of such reduced size by magnetization measurements, magneto-transport, magneto-optical studies, and ferromagnetic resonance. Area (b) is focused on developing comprehensive research on MBE growth of phosphide-based ferromagnetic semiconductors, followed by a systematic investigation of their spin-based properties. Although the spin properties of alloys such as GaMnP, InMnP and GaMnAsP are expected to be highly promising, and offer a range of important new opportunities, surprisingly little work has been done on this family of materials as compared to the effort given to, e.g., the GaMnAs or InMnAs alloys. Extending the proposed studies to this new family of FM semiconductors is expected to significantly advance the understanding of ferromagnetic semiconductors generally.