MRI: Equipment Development: Development of Advanced Scanning Probe Techniques for Spintronics and Nanodevice Research

扫描探针显微镜（STM， AFM， BEEM等）已经彻底改变了我们可视化和操纵单个原子，化学键和电子波的方式。一项新技术和仪器的成功开发，使我们能够可视化和操纵磁态，甚至是单个自旋，显然将是设备和材料研究的另一个伟大里程碑。STM只是一个双终端设备，但是研究自旋相关的纳米级输运现象，类似于晶体管的作用，需要一个三终端设备的安排。本课题拟构建一种低温、强磁场、超高真空环境下的双探针扫描隧道显微镜。该仪器不仅保持独立的扫描能力，而且能够将两个尖端（电极）定位在纳米级距离和所需位置，与样品形成纳米级三端器件。利用自旋极化STM尖端，该仪器将使我们能够注入、检测和操纵电荷和自旋，其可控性可低至原子尺度。它应该能够实现许多新的实验，包括但不限于：(a)基于高磁场中电子能谱的塞曼分裂映射稀磁性半导体中的局部自旋极化；(b)利用双尖端BEEM研究铁磁性金属自旋注入半导体；(c)自旋场效应管器件的演示；这些研究将有助于加深对半导体和其他器件材料中的铁磁性的基本理解，为提高材料性能（如更高的居里温度和自旋相干载流子的长平均自由程）提供指导，并使基于自旋自由度和电荷自由度的新器件概念的发展成为可能。所提出的仪器的独特和强大的能力是目前任何传统的SPM仪器或光刻制造技术无法实现的。更广泛的影响将吸引并使本科生，研究生和博士后研究人员探索最前沿的纳米级器件和材料物理学，特别是自旋电子学。这项提议的研究涉及广泛的实验技能，应该为培训下一代实验物理学家和工程师提供一个相当特殊的机会。

Intellectual MeritScanning Probe Microscopy (STM, AFM, BEEM etc) has revolutionized the way we visualize and manipulate individual atoms, chemical bonds, and electron waves. A successful development of a new technique and instrument that can enable us to visualize and manipulate magnetic states and even a single spin would clearly be another great milestone in device and materials research. An STM is just a two terminal device but the investigation of spin-dependent nanoscale transport phenomenon, similar to transistor action, requires a three terminal device arrangement. Here we propose to construct a dual-probe scanning tunneling microscope operating in a low temperature, high magnetic field and ultra high vacuum environment. Such an instrument not only maintains independent scanning capability but also is capable of positioning the two tips (electrodes) at nanoscale distances and desired locations, forming a nano-scale three-terminal device with the specimen. Using spin polarized STM tips, this instrument will enable us to inject, detect and manipulate both charges and spins with the controllability down to the atomic scale. It should enable many new experiments including but not limited to: (a) mapping local spin polarization in a dilute magnetic semiconductor based on the Zeeman splitting of the energy spectra of an electron in a high magnetic field; (b) investigating spin injection from a ferromagnetic metal into a semiconductor using a dual tip BEEM; (c) demonstrations of spin FET devices;These studies should enable deeper fundamental understanding of ferromagnetism in semiconductors and other device materials, provide guidance for improving materials performance such as higher Curie temperature and long mean free path for spin coherent carriers, and enable development of novel device concepts based on spin degrees of freedom, in addition to charge degrees of freedom. The unique and powerful capabilities of the proposed instrument cannot be achieved by any current conventional SPM instrument or lithographical fabrication technique.Broader ImpactIt will attract and enable the undergraduate, graduate students, and postdoctoral fellows to explore the most forefront nanoscale device and materials physics, particularly spintronics. This proposed research involves a broad set of experimental skills and should provide a rather special opportunity for training the next generation of experimental physicists and engineers.