NER: Development of an Ultrafast Scanning Probe Microscope

本纳米尺度探索性研究（NER）提案已收到NSE， NSF 02-148的响应。这个为期一年的项目包括开发一种新型的飞秒无孔径扫描近场光学显微镜（FANSOM），它将提供具有纳米空间分辨率和飞秒时间分辨率前所未有的运动图像。该仪器将用于探测单个人工纳米结构（如量子点）的电子激发、消相和种群衰变动力学，以及单个有机大分子的光致电子和构象动力学。该显微镜将基于一种经过验证的无孔径近场成像技术，其中来自尖锐金属尖端的光散射扫描整个基板，提供纳米空间分辨率的图像。使用飞秒激光脉冲的光泵浦探测技术将获得快速的时间分辨率。随着泵浦脉冲和探针脉冲之间延迟时间的增加，相应的多幅图像将被组装成具有飞秒时间分辨率的纳米尺度动态过程的实际电影。这个项目的成功完成将产生一个强大的新工具来探索纳米世界，在几乎所有领域（物理、化学、材料科学、生命科学、量子计算等）都有潜在的应用，在这些领域中，有趣的动力学发生在纳米尺度上，并且被非均匀效应所掩盖。所获得的运动图像的图形性质，加上对纳米结构动力学的基本和实际兴趣，使该仪器成为科学学生和公众的理想教育工具。研究生和本科生将参与仪器的开发，以及它的使用科学研究。该项目由材料研究部和物理部联合支持。本纳米尺度探索性研究（NER）提案已收到NSE， NSF 02-148的响应。这个为期一年的项目涉及开发一种新型显微镜，该显微镜将提供具有近原子空间分辨率和超快时间分辨率的前所未有的运动图像。特别是，该仪器将用于探测单个人工纳米结构的激发和衰变，以及单个有机大分子的光诱导变化。这种显微镜将基于一种经过验证的技术，即从一个锋利的金属尖端散射的光扫描穿过一个表面，从而提供纳米空间分辨率的图像。使用超短激光脉冲可以获得快速的时间分辨率。一系列泵浦脉冲激发纳米结构，并使用延时探针脉冲进行成像。多幅图像对应于泵浦脉冲和探针脉冲之间增加的时间延迟，然后将被组装为感兴趣的过程的实际电影。这个项目的成功完成将产生一个强大的新工具来探索纳米世界，在几乎每个领域（物理、化学、材料科学、生命科学等）都有潜在的应用，在纳米尺度上发生有趣的过程。所获得的运动图像的图形性质，加上对纳米结构的基本和实际兴趣，使该仪器成为科学学生和公众的理想教育工具。研究生和本科生将参与仪器的开发，以及它的使用科学研究。该项目由材料研究部和物理部联合支持。

This Nanoscale Exploratory Research (NER) proposal was received in response to NSE, NSF 02-148. The one-year project involves developing a novel femtosecond apertureless scanning near-field optical microscope (FANSOM), which will provide moving images with the unprecedented combination of nanometer spatial resolution and femtosecond time resolution. The instrument will be used to probe the electronic excitation, dephasing, and population decay dynamics of individual artificial nanostructures such as quantum dots, as well as the photoinduced electronic and conformational dynamics of individual organic macromolecules. The microscope will be based on a proven apertureless near-field imaging technique, in which light scattering from a sharp metallic tip scanned across the substrate provides images with nanometer spatial resolution. Fast temporal resolution will be obtained using optical pump-probe techniques with femtosecond laser pulses. Multiple images corresponding to increasing delay time between pump and probe pulses will then be assembled as actual movies of nanometer-scale dynamical processes with femtosecond time resolution. Successful completion of this project will give rise to a powerful new tool to probe the nanoworld, with potential applications in virtually every field (physics, chemistry, materials science, life sciences, quantum computing, etc.) in which interesting dynamics occurs at the nanoscale and is obscured by inhomogeneous effects. The graphical nature of the moving images obtained, coupled with the fundamental and practical interest in the dynamics of nanostructures, make this instrument an ideal educational tool for both scientific students and the general public. Graduate and undergraduate students will be involved with the development of the instrument, as well as its use scientific studies. The project is jointly supported by the Divisions of Materials Research and Physics.This Nanoscale Exploratory Research (NER) proposal was received in response to NSE, NSF 02-148. The one-year project involves developing a novel microscope that will provide moving images with the unprecedented combination of near-atomic spatial resolution and ultrafast time resolution. In particular, the instrument will be used to probe the excitation and decay of individual artificial nanostructures, as well as light-induced changes of individual organic macromolecules. The microscope will be based on a proven technique, in which light scattering from a sharp metallic tip scanned across a surface provides images with nanometer spatial resolution. Fast time resolution will be obtained with ultrashort laser pulses. A series of pump pulses excites the nanostructure, and time-delayed probe pulses are used for imaging. Multiple images corresponding to increasing time delay between pump and probe pulses will then be assembled as actual movies of the processes of interest. Successful completion of this project will give rise to a powerful new tool to probe the nanoworld, with potential applications in virtually every field (physics, chemistry, materials science, life sciences, etc.) in which interesting processes occur at the nanoscale. The graphical nature of the moving images obtained, coupled with the fundamental and practical interest in nanostructures, make this instrument an ideal educational tool for both scientific students and the general public. Graduate and undergraduate students will be involved with the development of the instrument, as well as its use scientific studies. The project is jointly supported by the Divisions of Materials Research and Physics.