Trilayer and Superlattice Half Metal Thin Films

智力优势：人们对硅基自旋电子材料，特别是半金属材料，在室温器件中的应用有着浓厚的兴趣。在以往的研究中，已经预测了掺杂锰的硅薄膜的半金属丰度。然而，Mn原子需要占据能量昂贵的取代位，这需要打破Si-Si键。这种键断过程一直是实现这类材料的主要障碍，这些材料可能利用成熟的Si技术。最近，PI预测了两个Mn/Si/Mn三层的半金属性，Mn浓度为0.5单层并占据能量有利的间隙位，以及间隔层中0.5单层的空穴掺杂。这些令人兴奋的结果表明，半金属硅基三层薄膜及其相关的超晶格是可以实现的。本项目结合理论和实验的努力，设计和实现了这种薄膜形式的硅基半金属的三层和超晶格伪自旋阀。在铁磁或反铁磁相中寻找理想的半金属三层和超晶格，以及修改现有算法来处理所提出的伪自旋阀的输运性质，将为层状结构中的磁性和电子性质提供新的知识。在硅间隔层中掺杂将增强两个锰层之间的磁耦合。新的磁化率算法将允许在任何磁性系统中精确测定居里温度。将进行结构、磁性和磁输运测量，以表征制造结构并将其性质与理论预测进行比较。硅基材料的使用将使自旋电子器件的技术应用迅速发展。理论和实验工作的协同作用有望促进这些新型器件的优化设计和制造。更广泛的影响：拟制的伪自旋阀有望展现出新的、有趣的半金属性质，这与新型自旋电子器件的发展高度相关，如传感器、开关、磁存储器和逻辑器件。此外，本文还对以下问题有了新的认识：(1)两层过渡金属元素之间的空穴掺杂是如何导致三层和超晶格中Mn层之间的半金属丰度和磁矩耦合的？（ii）关于操纵生长参数的独特新知识，通过合成方法获得具有预测性质的硅基三层和超晶格伪自旋阀样品。这些进步将极大地促进自旋电子器件的未来发展。pi将积极招募少数族裔学生与他们一起工作。他们与美国、瑞典、德国、中国、西班牙和土耳其的研究小组合作。研究生将有机会与国内和国际领域的顶尖研究人员进行互动。pi还努力将研究与教育和外展活动相结合，以增强学生从初中到研究生院的学习经验。

Intellectual Merit:There has been intense interest in silicon based spintronic materials, particularly half-metals, for room temperature device applications. In previous studies, half-metallicity has been predicted in thin films of Mn-doped Si. However, the Mn atoms need to occupy the energetically costly substitutional sites that require breaking of Si-Si bonds. This bond breaking process has been the major obstacle for achieving this class of materials that may take advantage of the mature Si technology. Very recently, the PI has predicted half-metallicity in two Mn/Si/Mn trilayers with Mn concentration at 0.5 monolayer and occupying the energetically favorable interstitial sites, and a 0.5 monolayer hole doping in the spacer layer. These exciting results suggest that half metallic Si-based trilayers and their related superlattices are within reach. This project combines theoretical and experimental efforts to design and realize such trilayer and superlattice pseudo-spin valves of silicon-based half-metal in thin film forms. The search for the ideal half-metallic trilayers and superlattices in ferromagnetic or antiferromagnetic phases, and modifications of existing algorithms to treat transport properties for proposed pseudo-spin valves will provide new knowledge concerning magnetism and electronic properties in layered structures. Doping in the Si spacer layer will be used to enhance the magnetic coupling between the two Mn layers. New algorithms of magnetic susceptibility will allow accurate determination of Curie temperature in any magnetic systems. Structural, magnetic, and magneto-transport measurements will be performed in order to characterize the fabricated structures and compare their properties with theoretical predictions. The use of silicon-based materials would enable rapid development of technological applications for spintronic devices. The synergy of the theoretical and experimental efforts is expected to facilitate the optimal design and fabrication of these novel devices.Broader Impacts:The proposed pseudo-spin valves are expected to exhibit new and intriguing half-metallic properties, which are highly relevant for the development of novel spintronic devices, such as sensors, switches, magnetic memory, and logic devices. Furthermore, new understandings will be gained on: (i) how can the hole doping between two layers of transition metal elements cause the half metallicity and couple the magnetic moments between Mn layers in the trilayers and superlattices? (ii) unique new knowledge about manipulating growth parameters to obtain samples of Si-based trilayer and superlattice pseudo-spin valves with predicted properties by the synthesis method. These advancements will significantly facilitate future developments of spintronic devices. The PIs will actively recruit underrepresented minority students to work with them. They have collaborations with research groups in the US, as well as in Sweden, Germany, China, Spain and Turkey. Graduate students will have the opportunity to interact with leading researchers in the field nationally, as well as internationally. The PIs also strive to integrate research with educational and outreach activities to enhance the learning experience of students from junior high school through graduate school.