Theory of Spin Transport in Silicon Nanostructures

超越CMOS时代的未来技术正在成为极其重要的研究前沿。在这方面，科学家推测，基于自旋的设备一定是在地平线上。在这些装置中，量子力学自旋被引入电子电路。硅是制造自旋电子器件的理想材料。它拥有在半导体行业占据绝对优势的成熟技术。重要的是，硅具有相对较长的自旋弛豫时间，这是由于其弱自旋-轨道耦合和重要的自旋弛豫机制被抑制（通过晶体反转对称性和其天然丰富的同位素的零核自旋）。因此，自旋信息可以在硅中携带超过1毫米的长度尺度。所建议活动的智力价值：1。研究了应变、电场和量子化存在下硅器件的自旋弛豫。在这一部分中，基本的器件几何结构包括自旋注入器和检测器之间的传输通道。通过这种基本结构的输运将使用漂移-扩散模型进行研究，该模型的基本参数（例如，自旋寿命和电荷迁移率）将通过精确量化电子-声子相互作用的严格数值方法计算。这些方法包括经验伪势方法和k&amp；#8729；用P模型计算电子波函数，用绝热键荷模型计算声子色散和原子位移矢量。应变效应可以很容易地纳入这些模型，而沿约束方向的量子化效应在k&amp；#8729；p模型。电子-声子散射将用刚性离子近似来模拟。群论将用于确定简化分析的选择规则。2。将获得的知识整合到设备模拟中。自旋注入、抽离和接触宽度的作用将由经过验证的实验结果得出的现实边界条件进行。本文将研究一种基于自旋的片上信息传输的新概念，以缓解片上传输线的许多尖锐问题。通过蒙特卡罗模拟研究了导电电子在硅线和硅锗纳米结构器件中漂移的加热效应，量化了电荷输运和自旋寿命。除了自旋翻转，动量弛豫将由电子-晶格和电子-杂质散射来模拟。拟议活动的更广泛影响：拟议的研究包括硅自旋电子学的新理论方面和器件概念。由于硅的自旋注入是近年来非常活跃的研究领域，本研究非常及时，可能具有重要的影响。除了在同行评审的期刊上发表的论文和在专业会议上的演讲外，这个项目的成果（理论预测和设备模型结果）将与硅自旋电子学的主要实验家分享。我们之前的自旋电子学结果的广泛影响已经在几本科学杂志上得到了强调，包括《科学新闻》、《纳米材料新闻》和《新科学家》。教育活动是该项目的重要组成部分，并与拟议的计划紧密结合。拟议的研究提出了吸引广大学生的想法。通过工程和物理研究生的合作，双方相互学习量子力学或器件功能概念。PI已经设计了一门关于自旋电子学的新课程，该课程解释了如何将量子力学和磁学应用于新的逻辑和存储架构。PI致力于培养学生，并将本研究与本科课程相结合，并将招募合格的本科生参与研究。PI将通过提供互动讲座/演示，在K-12学生中积极推广这项研究，突出未来技术在设备中的应用。这项研究对社会产生巨大影响的潜力有望吸引来自代表性不足群体的学生参与该项目。

Future technologies beyond the CMOS age are becoming exceedingly important research frontiers. In this regard, scientists conjectured that spin-based devices must be on the horizon. In these devices, the quantum mechanical spin is introduced to electronic circuits. Silicon is an ideal material choice for spintronic devices. It has a mature technology which overwhelmingly dominates the semiconductor industry. Importantly, silicon has a relatively long spin relaxation time due to its weak spin-orbit coupling and the suppression of important spin relaxation mechanisms (via the crystalline inversion symmetry and the zero nuclear spin of its naturally abundant isotope). Accordingly, spin information can be carried over 1 mm length scales in silicon.Intellectual Merit of the proposed activity:I. Studying the spin relaxation in silicon devices in the presence of strain, electrical fields and quantization. In this part, the basic device geometry includes a transport channel between spin injector and detector. Transport across this basic structure will be studied using a drift-diffusion model whose basic parameters (e.g., spin lifetime and charge mobility) will be calculated from rigorous numerical methods that accurately quantify the electron-phonon interaction. These include an empirical pseudopotential method and a k∙p model to calculate the electron wavefunctions and an adiabatic bond-charge model to calculate the phonon dispersion and atom displacement vectors. Strain effects can be readily incorporated in these models while quantization effects along the confinement direction are explicitly considered in the k∙p model. The electron-phonon scattering will be modeled by a rigid-ion approximation. Group theory will be used to identify selection rules that simplify the analysis. II. Incorporating the gained knowledge in device simulations. Spin injection, extraction and the role of contact widths will be carried by realistic boundary conditions taken from verified experimental results. A new concept for on-chip spin-based information transfer that alleviates much of the acute problems of on-chip transmission lines will be studied. Heating effects of drifting conduction electrons (by the electric field) in silicon wires and silicon-germanium nanostructure devices will be investigated by Monte Carlo simulations which quantify both the charge transport and spin lifetime. Other than spin flips, momentum relaxation will be modeled by electron-lattice and electron-impurity scattering. Broader impacts of the proposed activity:The proposed research includes new theoretical aspects and device concepts in silicon spintronics. This research is timely and may have an important impact since spin injection in silicon has recently become a very active research field. Other than publications in peer-reviewed journals and presentations in professional conferences, outcomes of this project (theoretical predictions and device model results) will be shared with leading experimentalists in silicon spintronics. The broad impact of our previous spintronics results has been highlighted in several science magazines including the Science News, Nanomaterials News and the New Scientist. Educational activities are an essential part of this project and are closely integrated with the proposed program. The proposed research presents ideas that are fascinating to a wide range of students. By collaboration of engineering and physics graduate students, each side learns from the other quantum mechanics or device function concepts. The PI has already designed a new course on spintronics which explains how quantum mechanics and magnetism can be applied into new logic and memory architectures. The PI is committed to training students and will integrate this research with undergraduate courses and will recruit qualified undergraduate students to participate in the research. The PI will actively promote this research among K-12 students by delivering interactive lectures/demos that highlight the use of future technology in devices. The potential of this research for high societal impact will hopefully attract students from under-represented groups to the project.