Probing Individual and Interacting Dopants in Semiconductors and Superconductors on the Nanometer Scale

摘要：在过去的50年里，许多技术的进步都是通过掺杂杂质来控制材料的性能而实现的。如果没有通过掺杂调整半导体电子特性的能力，现代信息处理是不可能实现的。该计划通过纳米尺度的测量和使用最先进的实验技术的操作，为理解材料中的掺杂提供了一个新的窗口。这个程序的独特性来自于演示的实验能力，以原子精度控制单个掺杂剂的位置。该计划将重点关注掺杂如何将半导体转变为磁铁的问题。磁性半导体有潜力创造一种利用自旋自由度进行计算的新型电子设备。它们可能使信息处理和存储在单个芯片上结合起来成为可能。可以想象，在这个项目中探索的基础科学将导致可以在室温下工作的磁性半导体-克服这些材料应用中的主要障碍之一。该项目还将为培养下一代物理学家做出重大贡献，这些物理学家是材料物理学和先进扫描探针显微镜技术的专家。本科学生积极参与拟议的计划，并将受益于一个新的新生研讨会的发展，一个新的STM的建设。该计划还通过普林斯顿纳米显微镜实验室的定期参观和演示，吸引了更多的高中生和教育工作者。技术摘要：本项目的研究包括两个相关的工作，它们的主要目标是了解单一掺杂剂和掺杂剂之间的相互作用，这些相互作用使绝缘材料成为具有集体电子现象的导电系统。特别是，该项目侧重于原子尺度测量的影响，将半导体转变为铁磁体和电荷密度波系统转变为超导体的掺杂剂。利用扫描隧道显微镜（STM）和高分辨率光谱测量技术对掺杂剂进行纳米级操作，以探测单一掺杂剂及其相互作用。利用STM的原子置换技术，将单个磁性过渡金属掺杂剂植入GaAs中，以确定这些掺杂剂如何改变半导体的局部电子结构。这些磁性掺杂剂之间的相互作用被认为会产生磁性，例如mn掺杂GaAs中的铁磁性。过渡金属掺杂剂之间相互作用的原子尺度特征将使用各种STM光谱技术进行探测。将掺杂剂的轨道态直接映射为外部磁场的函数，将用于探测单掺杂剂水平上的自旋轨道耦合。总的来说，该程序提供了单个掺杂剂的电子结构的微观视图，并使用纳米操作来执行隔离掺杂剂之间相互作用的受控测量。

Non-Technical Abstract:Much of the technological advances in the past 50 years have been made possible by controlling the properties of materials through doping them with impurities. Modern information processing would have not been possible without the ability to tailor the electronic properties of semiconductors through doping. This program provides a new window in understanding doping in materials through nanoscale measurement and manipulation using state-of-the-art experimental technique. The uniqueness of this program comes from the demonstrated experimental ability to control the position of individual dopants with atomic precision. The program will focus on the question of how doping transforms a semiconductor into a magnet. Magnetic semiconductors have the potential to create a new class of electronic devices that utilize the spin degree of freedom for computation. They may make it possible to combine information processing and storage on a single chip. It is conceivable that the basic science explored in this project would lead to magnetic semiconductors that can operate at room temperature -- overcoming one of the major obstacles in applications of these materials. This project will also contribute significantly to training of the next generation of physicists, who are experts in materials physics as well as advanced scanning probe microscopy techniques. Undergraduate students are actively involved in the proposed program and will benefit from the development of a new Freshman Seminar on the construction of an STM. The proposed program also reaches wider audience of high-school students and educators through regular tours and demonstrations at the Princeton Nanoscale Microscopy Laboratory.Technical Abstract:The research undertaken in this project comprises two related efforts that are connected by the main objective-- to understand single dopants and dopant-dopant interactions that make insulating materials into conducting systems with collective electronic phenomena. In particular, this project focuses on atomic scale measurements of the influence of dopants that transforms a semiconductor into a ferromagnet and a charge-density-wave system into a superconductor. Nanoscale manipulation of dopants with the scanning tunneling microscope (STM) and high-resolution spectroscopic measurements will be combined to probe single dopants and their interactions. Using a novel atom-by-atom substitution technique with the STM, individual magnetic transition metal dopants will be implanted in GaAs to determine how these dopants alter the local electronic structure of this semiconductor. Interaction between these magnetic dopants is believed to result in magnetism, such as ferromagnetism in Mn-doped GaAs. The atomic scale characteristics of the interaction between transition metal dopants will be probed using various STM spectroscopic techniques. Direct mapping of the orbital state of dopants as function of external magnetic field will be used to probe spin-orbit coupling at a single-dopant level. Overall, the program provides a microscopic view of electronic structure of single dopants and uses nano-manipulation to perform controlled measurements of the interaction between isolated dopants.