Novel Semiconductor-Based Epitaxial Magnetic Heterostructures

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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.***