NER: Nanoscale Photocathodes for Ultrafast Electron Microscopy

NER：用于超快电子显微镜的纳米级光电阴极

• 批准号: 0508143
• 负责人: W. Andreas Schroeder
• 金额: $ 8万
• 依托单位: University of Illinois at Chicago
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2005
• 资助国家: 美国
• 起止时间: 2005-07-15 至 2006-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0508143&HistoricalAwards=false
• 关键词: NER; Nanoscale; Photocathodes; Ultrafast; Electron

The recent First National Lab and University Alliance Workshop on Ultrafast ElectronMicroscopies, April 16-17, 2004, Pleasanton, CA, clearly indicated the tremendous potential scientific advances that would be facilitated by combining today's atomic-scale resolution of electron microscopy with the sub-picosecond (10-12s) temporal resolution now standard in ultrafast laser spectroscopy. The unprecedented spatio-temporal resolution afforded by the development of a dynamic transmission electron microscope (DTEM) would provide an important new tool for sensing materials and molecules on the nanoscale. Such an innovative advance could, in the future, allow the direct visualization of individual atomic motions - an important step in understanding both chemical reaction kinetics (e.g., biological and industrial catalysis) and fundamental physical processes in solid-state materials (e.g., the interaction of lattice vibrations with atomic-scale defects). Even modest temporal information provided by such an instrument on individual nano-particles and structures should also enable significant improvements to be made in Nanoscale Devices and System Architecture. It is this promise of significant scientific benefit and broad impact that ameliorates the high risk of this technologically challenging exploratory research project.We intend to investigate the primary key intellectual problem facing the development of a future DTEM; namely, the generation of a spatially-coherent electron pulse from an ultrashort pulse laser-driven photocathode in the presence of intrinsic decoherencing electron-electron scattering (or space-charge) effects. To meet this challenge, we propose to combine today's nanotechnology with a state-of-the-art, high-power, picosecond laser system to control the initial spatial phase of pulsed photoemission from a large-area nano-patterned (e.g., quantum dot array) photocathode. The propagation dynamics (i.e., partial spatial coherence and temporal pulse broadening) of the electron pulse from the prototype ultrafast test-bed electron gun will be studied to determine the optimum coherent photoemission conditions.

最近于2004年4月16日至17日在加利福尼亚州普莱森顿举行的第一届国家实验室和大学联盟超快电子显微镜研讨会清楚地表明，将当今电子显微镜的原子尺度分辨率与目前超快激光光谱标准的亚皮秒(10-12秒)时间分辨率相结合，将促进巨大的潜在科学进步。动态电子显微镜(DTEM)的发展提供了前所未有的时空分辨率，将为在纳米尺度上传感材料和分子提供重要的新工具。这种创新的进展在未来可以直接显示单个原子的运动--这是理解化学反应动力学(例如，生物和工业催化)和固体材料中的基本物理过程(例如，晶格振动与原子尺度缺陷的相互作用)的重要一步。即使是这种仪器提供的关于单个纳米粒子和结构的适度时间信息，也应该能够在纳米设备和系统架构方面取得重大改进。正是这种具有重大科学意义和广泛影响的前景，改善了这一具有技术挑战性的探索性研究项目的高风险。我们打算研究未来DTEM发展面临的主要关键智力问题，即在存在固有退相干电子-电子散射(或空间电荷)效应的情况下，从超短脉冲激光驱动的光电阴极产生空间相干电子脉冲。为了应对这一挑战，我们建议将当今的纳米技术与最先进的高功率皮秒激光系统相结合，以控制来自大面积纳米图案(例如量子点阵列)光电阴极的脉冲光电发射的初始空间相位。研究了原型超快实验台电子枪电子脉冲的传播动力学(即部分空间相干性和时间脉冲展宽)，以确定最佳相干光发射条件。