Novel Semiconductor-Based Epitaxial Magnetic Heterostructures

本论文主要研究了一类新型的多组元磁性合金和半导体外延异质结的合成和性质。它的目的是整合磁性材料和半导体，以探索涉及电荷和自旋自由度的现象，用于基础、基础科学研究和技术应用。要研究的体系将包括含有过渡金属(TM)、锰和B族元素(Z)的三元合金，即TMX-MNY-ZZ，它将与传统半导体如Si、Ge和GaAs耦合。前者包括一些预测的具有完全自旋极化导电态的半金属Heusler合金，也可能包括一些磁性半导体，这两种材料都是很好的自旋注入和分析候选材料。载流子电荷和自旋之间的相互作用，以及它们在半导体中的长平均自由程和自旋相干长度，有望产生许多传统异质结中不存在的新现象和自旋器件概念，并可能给电子和存储器件带来革命性的变化。然而，由于材料体系的缺乏，以及多组分体系的复杂性，该领域受到了限制。提出的方法是组合分子束外延合成和表征其结构、磁性和输运效应。该提议的优势在于外延合成和系统的方法，由此将产生新的材料和性能。参与该项目的研究生和本科生将接受对当前和未来技术至关重要的新型合成和表征方面的严格培训。还将为K12教师和学生进行大学前暑期研究项目，向这些小组介绍本研究涉及的技术问题。%这项工作集中于一类新的包含磁性合金和半导体单晶薄膜的异质结构的合成和性质。它的目的是探索涉及电子电荷和自旋的现象，用于基础、基础科学研究和技术应用。目前最先进的系统分别处理电子电荷和自旋。前者的一个例子是微处理器，它只使用电荷进行逻辑运算；相比之下，磁性硬盘只处理自转。两者的分离使这些系统本质上变得缓慢和笨重，而将两者整合可以彻底改变信息技术，例如，使电子和存储设备变得更快、更紧凑。然而，材料体系的缺乏和多元体系的复杂性限制了这一领域的发展。合适的候选材料必须从大量可能的组合中挑选出来。所提出的方法是对大量新材料及其性能进行系统的并行处理和筛选，即所谓的组合方法，以便第一次快速生成新材料和性能的库。从这项工作中发现的用于预期集成的材料预计是多元素磁性合金，其所有传导电子都被极化，同时与硅等传统半导体兼容。新材料将使同时处理电荷和自旋成为可能，从而产生新的量子现象和器件概念。参与该项目的研究生和本科生将接受严格的过程和技术培训，这些过程和技术对当前和未来的高科技至关重要。还将开展针对K12教师和学生的大学前暑期研究项目，向这些群体介绍本研究涉及的技术问题。*

This research is focused on the synthesis and properties of a new class of epitaxial heterostructures containing multi-component magnetic alloys and semiconductors. It is aimed at integrating magnetic materials and semiconductors, in order to explore phenomena involving both charge and spin degrees of freedom, for both fundamental, basic scientific studies and technological applications. The systems to be investigated will include ternary alloys containing transition metals (TM), Mn, and group B elements (Z), i.e. TMx-Mny-Zz, which will be coupled with conventional semiconductors, e.g. Si, Ge, and GaAs. The former include some predicted half-metallic Heusler alloys with fully spin-polarized conduction states, and may also include some magnetic semiconductors, both of which are excellent candidates for spin injection and analysis. The interactions between carrier charge and spin, and their long mean-free-path and spin coherence length in semiconductors are expected to give rise to many novel phenomena and spin device concepts that are not available in conventional heterostructures and can revolutionize electronic and memory devices. However, the field is limited by the lack of materials systems, and by the complex nature of the multi-component systems. The proposed approach is combinatorial molecular beam epitaxy synthesis and characterization of the structure, magnetism and transport effects. The strength of the proposal is in epitaxial synthesis and the systematic approach, from which new materials and properties will result. Graduate and undergraduate students involved in the project will be trained rigorously in novel synthesis and characterization that are essential for the current and future technologies. Pre-college summer research projects for K12 teachers and students will also be conducted to introduce these groups to the technology issues involved in this research.%%%This work is focused on the synthesis and properties of a new class of heterostructures containing single crystalline films of magnetic alloys and semiconductors. It is aimed at exploring phenomena involving both the charge and spin of electrons for both fundamental, basic scientific studies and technological applications. Current state-of-the-art systems process the electron charge and spin separately. An example of the former is the microprocessor that uses only the charge to do logic operations; in contrast the magnetic hard disc processes only the spin. The separation of the two makes these systems intrinsically slow and bulky, while integrating the two can revolutionize information technology, for example, making electronic and memory devices substantially faster and more compact. However, the field is limited by the lack of materials systems, and by the complex nature of the multi-element systems. The suitable materials candidates must be selected from an enormous number of possible combinations. The proposed approach is to systematically process and screen a large number of new materials and their properties in parallel, the so-called combinatorial approach, such that for the first time libraries of new materials and properties will be generated rapidly. Materials to be discovered from this work for the intended integration are expected to be the multi-element magnetic alloys having all of their conduction electrons polarized while compatible with conventional semiconductors like silicon. The new materials will make it possible to process both the charge and spin simultaneously, leading to novel quantum phenomena and device concepts. Graduate and undergraduate students involved in the project will be trained rigorously in processes and techniques that are essential for the current and future high technologies. Pre-college summer research projects for K12 teachers and students will also be conducted to introduce these groups to the technology issues involved in this research.***