Collaborative Research: Transport Imaging of Semiconductor Nanowires

技术：该项目将桥接的碳化硅和硅纳米线的气液固(VLS)生长/处理与纳米级成像技术相结合，以研究合成、处理和接触/传输行为之间的关系。传输成像结合了近场光学的扫描分辨率和扫描电子显微镜(SEM)的电荷产生光束控制。一个目标是通过光的复合发射来监测电荷的运动，从而“成像传输”。这项技术建立在标准阴极发光(CL)的基础上，但有很大的不同，因为它保持了发射光的空间信息，允许直接测量空间分辨的少数载流子扩散、外加电场下的迁移率寿命产物和接触电阻--否则很难在单根纳米线上测量这些参数。该项目的目标是使用原子力显微镜(AFM)/近场扫描光学显微镜(NSOM)在扫描电子显微镜内操作，将这种成像带到~50-100 nm的尺度。通过将电子束激发与光学收集分离，人们可以成像沿导线长度从大约100纳米到微米的距离的电荷传输。将使用Nanonics MultiView 2000系统，该系统允许对光纤尖端或样品进行独立扫描。测量将在单独桥接的碳化硅和硅纳米线以及氧化锌和氮化镓纳米线上进行。VLS纳米线的合成/加工研究是合作研究的一个组成部分。这项技术已经成功地用于固体晶须和纳米线的生长；桥联生长已经在硅微沟槽中得到证实。桥接结构已被发现与沟槽的接收侧进行刚性连接，使得它们对于大规模器件制造具有重要意义。它们还为传输成像提供了施加外偏压的理想结构。具体目标包括1)演示半导体纳米线的直接输运成像，2)输运测量作为纳米线直径的函数，3)接触电阻和载流子注入的测量，4)研究VLS工艺催化剂和表面钝化对光学和输运性质的作用。非技术性：该项目涉及具有高度技术相关性的电子/光子材料科学专题领域的基础研究问题。此外，该项目还为三名研究生和至少6-8名本科生和高中生提供教育和培训。NPS教育美国军队所有军种的现役军官，以及来自30多个国家的学生。这些学生反映了美国现役军人的充分多样性，许多学生在完成服役后将他们的技术教育带入正规劳动力的领导职位。加州大学伯克利分校的一名研究生将进行合作，UCB将利用其卓越的(Summer Underly Program In Berkeley)工程研究项目，让本科生和暑期学生参与进来。将特别重视招收妇女和任职人数偏低的学生。这两个私人助理都有指导妇女和代表性不足群体的良好记录，并一直活跃在本科生和K-12外联活动中。结果将通过出版和介绍以及在国家警察和联合公民委员会的公共宣传场所传播。

Technical: This project combines VLS (vapor-liquid-solid) growth/processing of bridged SiC and Si nanowires with a nanoscale imaging technique to study relationships between synthesis, processing, and contact/transport behavior. Transport imaging combines the scanning resolution of near field optics with the charge generation beam control of a scanning electron microscope (SEM). A goal is to "image transport" by monitoring the motion of charge via the recombination emission of light. The technique builds upon standard cathodoluminescence (CL), but is significantly different, since it maintains spatial information of the emitted light, which allows for direct measurement of spatially resolved minority carrier diffusion, mobility-lifetime products under applied fields, and contact resistance--parameters otherwise difficult to measure on a single nanowire. The project aims to take this imaging to the ~ 50-100 nm scale with the use of an atomic force microscope (AFM)/near field scanning optical microscope (NSOM) operating inside an SEM. By decoupling the e-beam excitation from the optical collection, one can image transport of charge over distances from ~ 100 nm to microns along wire lengths. A Nanonics MultiView 2000 system will be used, which allows for independent scanning of fiber tip or sample. Measurements will be performed on individually bridged SiC and Si nanowires, as well as ZnO and GaN wires. VLS nanowire synthesis/processing research is an integral part of the collaborative research. This technique has been successfully demonstrated for the growth of solid whiskers and nanowires; bridged growth has been demonstrated within silicon microtrenches. The bridged structures have been found to make rigid connections to the receiving side of the trench, making them of interest for large scale device fabrication. They also provide ideal structures for application of external bias for transport imaging. Specific goals include 1) demonstration of direct transport imaging in semiconductor nanowires, 2) transport measurements as a function of nanowire diameter, 3) measurement of contact resistance and carrier injection, 4) study of the role of VLS process catalyst and surface passivation on optical and transport properties. Non-technical: The project addresses basic research issues in a topical area of electronic/photonic materials science with high technological relevance. Additionally, the project provides education and training for three graduate students and a minimum of 6-8 undergraduate and high school students. NPS educates active duty officers in all branches of the US forces, as well as students from 30+ countries. The students reflect the full diversity of the US active duty force and many take their technical education into positions of leadership in the regular workforce upon completion of their service. A UC Berkeley graduate student will work in collaboration, and UCB will take advantage of its SUPERB ((Summer Undergraduate Program in Engineering Research at Berkeley) program to involve undergraduate and summer students. Special emphasis will be placed on recruitment of women and underrepresented students. Both PIs have strong records of mentoring women and underrepresented groups and have been active in undergraduate and K-12 outreach. The results will be disseminated through publication and presentation, as well as public outreach venues at both NPS and UCB.