Extracting the Boersch effect contribution from experimental energy spread measurements for Schottky electron emitters

Bronsgeest, M. S.; Barth, J.; Schwind, G. A.; Swanson, L. W.; Kruit, P.

doi:10.1116/1.2794067

Cited by 25 publications

(3 citation statements)

References 17 publications

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“…When V E was 3,000 and 3,500 V, the FWHMs of the energy spread were measured and found to be 1.27 eV ( J Ω = 92 μ A/sr) and 1.47 eV ( J Ω = 137 μ A/sr), respectively, where J Ω is the angular current density. We assume that the angular current density increases as the electric field increases, resulting in a broadened energy distribution owing to electron-electron interaction, known as the Boersch effect (Bronsgeest et al, 2007). Therefore, when the parameter q is increased by V E in the theoretical TED, the ES model becomes inaccurate.…”

Section: Resultsmentioning

confidence: 99%

High-Performance Compact Pre-Lens Retarding Field Energy Analyzer for Energy Distribution Measurements of an Electron Gun

Lee

Hwang

Ogawa

et al. 2022

Microscopy and Microanalysis

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The energy distribution of an electron gun is one of the most important characteristics determining the performance of electron beam-based instruments, such as electron microscopes and electron energy loss spectroscopes. For accurate measurements of the energy distribution, this study presents a novel retarding field energy analyzer (RFEA) with the feature of an additional integrated pre-lens, which enables an adjustment of beam trajectory into the analyzer. The advantages of this analyzer are its compact size and simple electrode configuration. According to trajectory simulation theories, the optimum condition arises when the incident electron beam inside the RFEA is focused on the center of a retarding electrode. Comparing I–V curves depending on whether the pre-lens working or not, it is confirmed that the use of the pre-lens dramatically improves the energy resolution and efficiency of the signal acquisition process. The pre-lens RFEA was applied to characterize a Schottky electron gun under various temperatures and extraction voltages as operational conditions. When the tip temperature was increased by 50 K, we were able to measure an energy distribution broadening of 13.8 meV with the proposed pre-lens RFEA. The relative standard deviation of energy distribution was 0.7% for each working condition.

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Section: Resultsmentioning

confidence: 99%

High-Performance Compact Pre-Lens Retarding Field Energy Analyzer for Energy Distribution Measurements of an Electron Gun

Lee

Hwang

Ogawa

et al. 2022

Microscopy and Microanalysis

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“…In Ref. 28,Bronsgeest et al presented the way to distinguish the Boersch effect from the intrinsic energy distribution. Since the intrinsic energy distribution is a function of temperature, work function, and the field at the emitter, this distribution can be assumed to be the same in case of the suppressorless configuration.…”

Section: Discussionmentioning

confidence: 99%

Concept and operation of Schottky emitter without suppressor electrode

Dokania

Kruit

2009

Journal of Vacuum Science &Amp; Technology B: Microelectronics and Nanometer Structures Processing, Measurement, and Phenomena

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The Schottky electron emitter is the most frequently used electron source in electron microscopes. A suppressor electrode around the emitter is usually employed to prevent emission from the shank of the cathode. A concept of operating the Schottky emitter without the suppressor electrode is proposed with the aim of lowering the potential of the extractor electrode. Simulation results show that if the suppressor electrode is removed, then the same field as for the standard configuration can be obtained at the tip apex at an extraction voltage of 2265 V instead of 5000 V. The total emission from the shank region is calculated by estimating the emission area of the shank, taking into the account the different work functions of the crystal facets. The total emission for typical operating parameters is calculated to rise from 500 to 668 A. The total emission from the shank and the filament of the Schottky emitter is measured experimentally in two different configurations, which match with the simulated results. The measured total emission of 450-750 A confirms the idea that a Schottky emitter can be operated without suppressor, all the more so because the power at the extractor aperture is even reduced as a result of the lower acceleration voltage.

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“…During the last few decades, brightness limitations caused by Coulomb interactions have been the subject of many experimental 18,34,53,54 and theoretical studies [55][56][57][58][59][60][61][62][63][64] considering continuous electron sources as well as pulsed photoemitters.…”

Section: Introductionmentioning

confidence: 99%

Coulomb Interactions in High-Coherence Femtosecond Electron Pulses from Tip Emitters

Bach¹

2021

Proceedings of the European Microscopy Congress 2020

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Tip-based photoemission electron sources offer unique properties for ultrafast imaging, diffraction, and spectroscopy experiments with highly coherent few-electron pulses. Extending this approach to increased bunch-charges requires a comprehensive experimental study on Coulomb interactions in nanoscale electron pulses and their impact on beam quality. For a laserdriven Schottky field emitter, we assess the transverse and longitudinal electron pulse properties in an ultrafast transmission electron microscope at a high photoemission current density. A quantitative characterization of electron beam emittance, pulse duration, spectral bandwidth, and chirp is performed. Due to the cathode geometry, Coulomb interactions in the pulse predominantly occur in the direct vicinity to the tip apex, resulting in a well-defined pulse chirp and limited emittance growth. Strategies for optimizing electron source parameters are identified, enabling advanced ultrafast transmission electron microscopy approaches, such as phase-resolved imaging and holography.

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Extracting the Boersch effect contribution from experimental energy spread measurements for Schottky electron emitters

Cited by 25 publications

References 17 publications

High-Performance Compact Pre-Lens Retarding Field Energy Analyzer for Energy Distribution Measurements of an Electron Gun

High-Performance Compact Pre-Lens Retarding Field Energy Analyzer for Energy Distribution Measurements of an Electron Gun

Concept and operation of Schottky emitter without suppressor electrode

Coulomb Interactions in High-Coherence Femtosecond Electron Pulses from Tip Emitters

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