Collaborative Research: Transport Imaging of Semiconductor Nanowires

技术支持：该项目结合了VLS（气-液-固）生长/加工的桥接SiC和Si纳米线与纳米成像技术，研究合成，加工和接触/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。目标是通过监测经由光的复合发射的电荷的运动来“图像传输”。该技术建立在标准的阴极发光（CL），但显着不同，因为它保持了发射光的空间信息，这允许直接测量的空间分辨少数载流子扩散，迁移率寿命产品下施加的领域，和接触电阻-参数，否则难以测量在一个单一的纳米线。该项目的目的是通过使用在SEM内操作的原子力显微镜（AFM）/近场扫描光学显微镜（NSOM）将这种成像带到~ 50-100 nm尺度。通过将电子束激发与光学收集解耦，可以沿着沿着导线长度在从~ 100 nm到微米的距离上对电荷的传输进行成像。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SiC和Si纳米线以及ZnO和GaN线上进行。VLS纳米线合成/加工研究是合作研究的一个组成部分。这种技术已被成功地证明为固体晶须和纳米线的生长;桥接生长已被证明在硅微沟槽内。已经发现桥接结构与沟槽的接收侧形成刚性连接，使得它们对大规模器件制造感兴趣。它们还为输运成像的外部偏压的应用提供了理想的结构。具体目标包括：1）演示半导体纳米线中的直接输运成像，2）作为纳米线直径的函数的输运测量，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：该项目涉及电子/光子材料科学领域的基础研究问题，具有高度的技术相关性。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。该学院教育美国军队所有分支的现役军官，以及来自30多个国家的学生。学生反映了美国现役部队的全面多样性，许多人在完成服务后将他们的技术教育纳入常规劳动力的领导岗位。一个加州大学伯克利分校的研究生将合作工作，UCB将利用其SUPERB（（伯克利分校工程研究夏季本科课程）计划，让本科生和暑期学生参与。将特别强调征聘妇女和任职人数不足的学生。这两个PI都有很好的指导妇女和代表性不足的群体的记录，并一直活跃在本科和K-12外展。调查结果将通过出版物和介绍以及在联合国教科文组织和教科文组织协调局的公共宣传场所进行传播。

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.