Microscopic Studies of Schottky Barrier Nano-Contacts and Nano-Structured Metal/Semiconductor and Metal/Insulator Interfaces

该项目涉及肖特基势垒纳米接触和纳米结构金属/半导体和金属/绝缘体界面的基础材料科学细节。该方法结合了三组实验，对具有纳米尺度尺寸或纳米尺度内部结构的金属-半导体（MS）和金属-绝缘体（MI）肖特基势垒（SB）界面的纳米级电子特性进行成像、量化和建模。局部SB性质将用纳米分辨率弹道电子发射显微镜（BEEM）测量，3D静电建模将用于比较和关联纳米尺度SB性质与总器件电响应。第一组实验将研究SB纳米接触，其中半导体尺寸系统地变化到~ 1nm，以探索小尺寸效应（例如量子约束和“环境钉住”）如何影响半导体纳米结构中的载流子注入。一种结构将由在GaAs/AlGaAs异质结构的劈裂面上制成的SB组成，该异质结构含有不同的，精确已知宽度的量子阱（qw）。这些样品也将用作纳米尺寸的“孔径”，用于定量研究金属薄膜中的横向热电子散射和弛豫，包括单个金属颗粒内部和之间的散射过程。第二组实验将使用不同的样品结构进行纳米分辨率的SB研究，同时对SB接触施加强门场。主要目的是成像和量化缺陷和器件边缘的强几何感应场如何影响局部SB特性和通过SB注入的载流子。这些样品结构也将用于双极BEEM测量，其中电子势垒和空穴势垒可以在同一位置量化，例如靠近特定缺陷。第三组实验将研究金属氧化物硅（MOS）结构，其中金属膜是具有非常不同工作功能的金属的横向纳米结构混合物。目标是成像、量化和建模金属薄膜中的横向纳米级结构如何影响金属/氧化物界面的局部和平均势垒高度，从而产生氧化膜和临界氧化物/硅界面中的局部和平均电场。一个相关的目标是研究金属双层层和其他纳米结构金属膜作为未来器件（mosfet）可能的“可调谐工作功能”金属。该项目涉及与纳米电子学中具有技术相关性的材料相关的基础研究问题。该项目的一个重要特点是高度重视教育，强调研究与教育的结合。该项目将为研究生和本科生的培养提供一个高度跨学科和协作的环境。学生应结合设备建造、半导体加工、使用新设备的先进实验、数值模拟以及与合作者的频繁互动，发展广泛的知识和训练基础。将继续积极招收本科生和代表性不足的学生。此外，PI将继续积极参与科学推广，特别是在K-6科学演示，学生互动和教师指导。

This project addresses fundamental materials science details of Schottky barrier nano contacts and nano-structured metal/semiconductor and metal/insulator interfaces The approach incorporates three sets of experiments to image, quantify, and model nm-scale electronic properties of metal-semiconductor (MS) and metal-insulator (MI) Schottky-barrier (SB) interfaces, which have nm-scale dimensions or nm-scale internal structure. Local SB properties will be measured with nm-resolution ballistic electron emission microscopy (BEEM), and 3D electrostatic modeling will be used to compare and correlate nm-scale SB properties with the total device electrical response. The first set of experiments will study SB nanocontacts where the semiconductor dimension is systematically varied down to ~ 1 nm, to probe how small-size effects (e.g. quantum-confinement and "environmental pinning") affect carrier injection into semiconductor nanostructures. A structure will be used consisting of a SB made on the cleaved face of a GaAs/AlGaAs heterostructure containing quantum wells (QWs) of different, precisely known width. These samples will also be used as nm-sized "apertures" for quantitative study of lateral hot-electron scattering and relaxation in metal films, including scattering processes within and between individual metal grains. A second set of experiments will use different sample structures for nm-resolution SB studies while a strong gate-field is applied to the SB contact. The main objective is to image and quantify how strong geometry-induced fields at defects and device edges affect the local SB properties and carrier injection through the SB. These sample structures will also be used for Ambipolar BEEM measurements, where the electron barrier and the hole barrier can be quantified at the same location, for example close to a particular defect. The third set of experiments will study metal-oxide-silicon (MOS) structures, where the metal film is a laterally nanostructured mixture of metals with very different workfunctions. The goal is to image, quantify, and model how lateral nm-scale structure in the metal film affects the local and average barrier height at the metal/oxide interface, and hence the resulting local and average electric fields in the oxide film and at the critical oxide/Si interface. A related goal is to investigate metal bilayers and other nanostructured metal films as possible "tunable workfunction" metals for future devices (MOSFETs). %%% The project addresses fundamental research issues associated with materials having technological relevance in nanoelectronics. An important feature of the project is the strong emphasis on education, with emphasis on integration of research and education. This project will provide a highly interdisciplinary and collaborative environment for graduate and undergraduate student training. Students are expected to develop a broad knowledge and training base by combining equipment construction, semiconductor processing, advanced experiments with novel equipment, numerical modeling, and frequent interactions with collaborators. Undergraduate and underrepresented students will continue to be actively recruited. Additionally, the PI will continue active involvement with science outreach, particularly in K-6 with science demonstrations, student interactions, and teacher mentoring.