High resolution electron energy loss microscopy based on ionization of cold atoms: a new tool for surface nanochemistry

HREELM（高分辨率电子能量损失显微镜）项目的目标是将来自法国aim<s:1> Cotton实验室的一种新型、高度单色的电子源与来自法国molsamculaires d'Orsay科学研究所的电子控制化学光谱学实验以及来自德国美因茨大学的一种创新的高分辨率全场光谱电子显微镜结合起来。这种独特的组合将允许微聚焦单色（~1 meV），非常低能量的电子（0-20 eV）用于纳米级表面结构和诊断。与具有高空间、能量、动量和时间分辨率（分别为20nm、几meV、0.003埃-1和150ps）的创新光谱全场显微镜的耦合，将为高分辨率光谱低能电子成像和快速切换过程的实时空间访问开辟道路（CEA/IRAMIS/SPCSI，法国）。单色电子源的创建，在meV水平上，使用先进的激光冷却技术对中性Cs原子进行冷却，然后通过激光电离以提供超冷电子束。该项目的初始阶段将致力于测试两个光源：第一个在美因茨，使用显微镜提供的meV能量分辨率测试单色性；第二个在ISMO，基于原子束，测试纳米结构的低能量聚焦。纳米结构机制采用解离电子附着，这是一种在特定低能量下导致分子系统选择性键断裂的共振过程。就其本身而言，这个实验代表了在纳米尺度上操纵和控制化学反应领域的一个突破。下一步将设计和构建具有飞行时间能量色散的光谱全场显微镜和3D（x,y,t）分辨图像探测器（SPCSI/Mainz）。超冷电子束在显微镜中的应用将使新型的低能电子成像具有最终的光谱能力，用于几mev分辨率的非弹性全场成像，此外，用于实时探测动态过程的时间分辨率成像。它是一种阴极透镜型显微镜，具有最佳的时间分辨率，可实现飞行时间能量滤波（名义上的亚mev分辨率）和亚ns频闪成像（150ps分辨率），具有高实空间和互反空间分辨率。纳米结构机理的原位诊断将使用高分辨率电子能量损失谱进行。此外，超冷电子源的时间结构可用于对表面分子或铁电样品进行时间分辨成像电子能量损失谱实验。综上所述，该项目旨在开发出迄今为止光束质量最好的光源和显微镜，并在先进的表面科学研究领域对其进行评估。

The goal of the HREELM (High Resolution Electron Energy Loss Microscope) project is to combine a novel, highly monochromatic electron source from Laboratoire Aimé Cotton (LAC, France) with the Electron Controlled Chemical Lithography experiment from Institut des Sciences Moléculaires d'Orsay (ISMO, France) and with an innovative high-resolution full-field spectroscopic electron microscope (Mainz University, Germany). This unique combination will allow microfocussing monochromatic (~1 meV), very low energy electrons (0-20 eV) for nanoscale surface structuring and diagnostics. The coupling to an innovative, spectroscopic full-field microscope, with high spatial, energy, momentum and time resolution (20nm, few meV, 0.003 Angstroms-1 and 150ps, respectively), will open the way towards high resolution spectroscopic low energy electron imaging and real-space access to fast switching processes (CEA/IRAMIS/SPCSI, France). The creation of a monochromatic electron source, at the meV level, uses advanced laser cooling techniques for neutral Cs atoms that are then ionized by lasers to provide an ultracold electron beam. The initial phase of the project will be devoted to test two sources: the first at Mainz, to test monochromaticity using the meV energy resolution provided by the microscope and the second at ISMO, based on an atom beam, to test low energy focalization for nanostructuring. The nanostructuring mechanism employs dissociative electron attachment, a resonant process at a specific low energy leading to selective bond breaking in molecular systems. In itself this experiment will represent a breakthrough in the domain of manipulating and controlling chemical reactions on the nanoscale. The next step will be the design and construction of spectroscopic full-field microscope with time-of-flight energy dispersion and 3D(x,y,t)-resolving image detector (SPCSI/Mainz). The implementation of the ultracold electron beam in the microscope will make a novel type of low energy electron imaging with ultimate spectroscopic capabilities, for inelastic full-field imaging at few-meV resolution and, in addition, for time-resolved imaging for real-time probing of dynamic processes. It is a cathode-lens type microscope optimized for best time resolution enabling time-of-flight energy filtering (nominally sub-meV resolution) and sub-ns stroboscopic imaging (150ps resolution) with high real and reciprocal space resolution. In-situ diagnostics of nanostructuring mechanism will be performed using high resolution electron energy loss spectroscopy. Furthermore, the time structure of the ultracold electron source can be exploited in time-resolved imaging electron energy loss spectroscopy experiments on molecules on surfaces or on ferroelectric samples. In conclusion, the proposed project intends to develop sources and microscope with the best beam quality ever produced and to assess them in advanced surface science research domains.