{"title":"High-Resolution EELS in an aberration-corrected LEEM: Design of electrostatic transfer lenses for hemispherical filters","authors":"Vincent Lemelin, Richard Martel","doi":"10.1016/j.ultramic.2025.114238","DOIUrl":null,"url":null,"abstract":"<div><div>Recent advances in Low-Energy Electron Microscopy (LEEM), including the development of aberration-corrected (AC) systems, have significantly enhanced spatial resolution. However, further progress is limited by the energy resolution of current instruments. In this work, we propose a novel approach to address this limitation by integrating two Hemispherical Deflector Analyzers (HDAs) in tandem: the first serving to monochromatize the electron source, and the second to enhance the spectroscopic performance of AC-LEEM for Electron Energy Loss Spectroscopy (EELS). This dual-HDA configuration provides a clear pathway toward combining high spatial and energy resolution, expanding the capabilities of LEEM for advanced surface and materials characterization. This paper discusses various criteria for implementing these HDAs on a commercial AC-LEEM and presents more specifically the design of four transfer lenses (TLs) for electron transfer between the HDAs and the other optical components of the instrument. The use of a natural aberration correction scheme based on the dispersion-compensation (DC) principle is also discussed for maximum current throughput. Using ray-tracing simulations, we first show that the TL design can effectively decelerate/accelerate the electrons between 0.1 and 15 keV, thus respecting the high-voltage operation of the AC-LEEM. A double focus of the electron beam is also simulated so that the electron positions are conserved after transfer at the exit/entrance of the HDAs, an important condition for DC operation. Finally, ray-tracing simulations of the TLs show that the focal plane can be switched from the image plane to the back focal plane, allowing fast switching between diffraction and imaging modes.</div></div>","PeriodicalId":23439,"journal":{"name":"Ultramicroscopy","volume":"278 ","pages":"Article 114238"},"PeriodicalIF":2.0000,"publicationDate":"2025-09-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Ultramicroscopy","FirstCategoryId":"5","ListUrlMain":"https://www.sciencedirect.com/science/article/pii/S0304399125001366","RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q2","JCRName":"MICROSCOPY","Score":null,"Total":0}
引用次数: 0
Abstract
Recent advances in Low-Energy Electron Microscopy (LEEM), including the development of aberration-corrected (AC) systems, have significantly enhanced spatial resolution. However, further progress is limited by the energy resolution of current instruments. In this work, we propose a novel approach to address this limitation by integrating two Hemispherical Deflector Analyzers (HDAs) in tandem: the first serving to monochromatize the electron source, and the second to enhance the spectroscopic performance of AC-LEEM for Electron Energy Loss Spectroscopy (EELS). This dual-HDA configuration provides a clear pathway toward combining high spatial and energy resolution, expanding the capabilities of LEEM for advanced surface and materials characterization. This paper discusses various criteria for implementing these HDAs on a commercial AC-LEEM and presents more specifically the design of four transfer lenses (TLs) for electron transfer between the HDAs and the other optical components of the instrument. The use of a natural aberration correction scheme based on the dispersion-compensation (DC) principle is also discussed for maximum current throughput. Using ray-tracing simulations, we first show that the TL design can effectively decelerate/accelerate the electrons between 0.1 and 15 keV, thus respecting the high-voltage operation of the AC-LEEM. A double focus of the electron beam is also simulated so that the electron positions are conserved after transfer at the exit/entrance of the HDAs, an important condition for DC operation. Finally, ray-tracing simulations of the TLs show that the focal plane can be switched from the image plane to the back focal plane, allowing fast switching between diffraction and imaging modes.
期刊介绍:
Ultramicroscopy is an established journal that provides a forum for the publication of original research papers, invited reviews and rapid communications. The scope of Ultramicroscopy is to describe advances in instrumentation, methods and theory related to all modes of microscopical imaging, diffraction and spectroscopy in the life and physical sciences.