Investigating the Effects of Charge Carrier Modulation in the Development of Ferromagnetic Order in Semiconducting Oxides

* 非技术性摘要 * 磁性是人类已知的最古老的现象之一，也是最难理解的现象之一。磁性材料，通常由金属离子如镍或钴制成，已经被已知并使用了几个世纪。该项目将进行一系列实验，以测试磁性是否会出现在材料中，其中没有任何成分本身是磁性的。这一目标将通过引入原子尺度的点缺陷来修饰氧基半导体来实现，特别是在氧原子的有序网络中制造空穴。这些缺陷预计将导致这些氧化物半导体的电导率增加，这可能引发铁磁性的发展。结合成像和分析技术，移动的电子之间的相互作用，电子门控，和光学激发，将被用来阐明如何在这些半导体系统的磁性发展。该奖项将大大推进铁磁性如何在金属和绝缘体之间的中间材料中发展的基本理解，并为制造新的磁存储器和逻辑器件的材料提供重要见解，这些器件可用于先进的计算。参加该项目的学生将接受适用于半导体/纳米技术行业以及学术界职业的高级分析技术培训。* 技术摘要 * 本课题将通过一系列实验，对过渡金属氧化物半导体中室温铁磁性的形成机制进行验证，从而使局部磁矩磁性和巡回磁性之间的材料性质合理化。这些性质包括局域化的时刻，移动的电荷载流子，和点缺陷，特别是氧空位之间的相互作用。 这将通过将缺氧氧化物半导体中增加的电导率的出现与铁磁性的发展相关联来实现。使用成像和分析技术的独特组合，预计有可能阐明如何在载流子浓度的变化，包括非磁性离子和点缺陷，电子门控，和光学激发影响这些磁特性和如何从过渡金属的局部时刻与氧空位相互作用，以诱导铁磁性。该奖项将通过以可控的方式探测绝缘体和导体之间的中间系统中的磁性，大大推进对铁磁性的基本理解。两个博士参加该项目的学生和多名本科生将接受适用于半导体/纳米技术行业以及学术界职业的高级分析技术培训。

****NON-TECHNICAL ABSTRACT****Magnetism is one of the oldest phenomena known to men, yet one of the most difficult to understand. Magnetic materials, typically made from metallic ions such as nickel or cobalt, have been known and used for centuries. This project will pursue a series of experiments to test whether magnetism can arise in materials where none of the constituents are magnetic by themselves. This goal will be pursued by modifying oxygen-based semiconductors through the introduction of atomic scale point defects, specifically making holes in the ordered network of oxygen atoms. These defects are expected to lead to an increase in the electrical conductivity of these oxide semiconductors, which can trigger the development of ferromagnetism. A combination of imaging and analytical techniques, the interplay among mobile electrons, electrical gating, and optical excitations, will be used to elucidate how magnetism develops in these semiconducting systems. This award will substantially advance the fundamental understanding of how ferromagnetism develops in materials that are intermediate between metals and insulators as well as provide important insight into materials for making new magnetic memory and logic devices, which could be used for advanced computing. The students participating in this project will be trained in advanced analytical techniques applicable to careers in the semiconductor/nanotechnology industries, as well as in academia. ****TECHNICAL ABSTRACT****This project will pursue a series of experiments to test a number of mechanisms that have been proposed for the development of room temperature ferromagnetism in semiconducting transition metal oxides, rationalizing the properties of materials intermediate between local moment magnetism and itinerant magnetism. These properties include the interplay between localized moments, mobile charge carriers, and point defects, specifically oxygen vacancies. This will be accomplished by correlating the emergence of an increased electrical conductivity in oxygen deficient oxide semiconductors with the development of ferromagnetism. Using a unique combination of imaging and analytical techniques it is expected to be possible to elucidate how the shift in carrier concentration with the inclusion of non-magnetic ions and point defects, electrical gating, and optical excitations affects these magnetic properties and how local moments from transition metals interact with the oxygen vacancy to induce ferromagnetism. This award will substantially advance the fundamental understanding of ferromagnetism by probing in a controlled manner the magnetism in systems intermediate between insulators and conductors. The two Ph.D. students and multiple undergraduates participating in this project will be trained in advanced analytical techniques applicable to careers in the semiconductor/nanotechnology industries, as well as in academia.