Testing the Performance of Tungsten-Graphite Cathodes as Electron Sources for MEMS Electron Microscopes

Kód výsledku v IS VaVaI

<a href="https://www.isvavai.cz/riv?ss=detail&h=RIV%2F68081731%3A_____%2F25%3A00648367" target="_blank" >RIV/68081731:_____/25:00648367 - isvavai.cz</a>

Výsledek na webu

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DOI - Digital Object Identifier

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Jazyk výsledku

angličtina

Název v původním jazyce

Testing the Performance of Tungsten-Graphite Cathodes as Electron Sources for MEMS Electron Microscopes

Popis výsledku v původním jazyce

ALLAHAM, M. M., KNÁPEK, A., BURDA, D., MOUSA, M. S. Testing the Performance of Tungsten-Graphite Cathodes as Electron Sources for MEMS Electron Microscopes. In: OTÁHAL, A., KNÁPEK, A., SKÁCEL, J., NOVOTNÁ, V., eds. IMAPS Flash Conference. 11th International Microelectronics Assembly and Packaging Society Flash Conference. Brno: Brno University of Technology, FEEC, 2025, č. 25, s. 57-58. ISBN 978-80-214-6369-1. MEMS technology enables the development of miniature electron microscopes, commonly referred to as MEMS electron microscopes. These systems employ field-emission electron guns designed to generate a stable electron beam with a small spot size, high emission current density, and long operational lifetime, which is essential for achieving high-quality microscopic imaging. However, traditional uncoated tungsten field emission cathodes exhibit several limitations when operated outside ultra-high vacuum conditions, including high threshold voltages, limited lifetime, short operation time, and a widely dispersed electron beam. Recent studies have demonstrated that coating the nano-apex of such cathodes with graphene nanolayers can significantly improve their performance, particularly in scanning tunneling microscopy under non-ultra-high vacuum conditions. Additionally, excellent field emission characteristics have been observed in amorphous exfoliated graphite flakes applied to micro glass tips. In this study, tungsten nano-tips were prepared and cleaned using an electrochemical etching process, and subsequently integrated into a 3D-printed field emission microscope comprising a cylindrical sample holder, a cylindrical extractor with a 2 mm aperture, and a cylindrical Einzel lens system with a 4 mm aperture. The electrodes were coated with gold and further treated with a layer of colloidal graphite to ensure optimal electrical conductivity. Tungsten-graphite cathodes were then fabricated by coating the entire cathode surface with an exfoliated isopropyl-graphite solution, ensuring full surface coverage including the nano-apex with graphene nanofilms, thereby enabling electron emission directly from the graphite layer. These cathodes were experimentally evaluated within the 3D-printed microscope setup to characterize the field emission properties of the generated electron beam, including current density, spot size, lifetime, operational stability, field enhancement factor, voltage conversion length, and effective emission area. Furthermore, their applicability as electron sources for MEMS electron microscopes was assessed through experimental measurements and simulations based on the 3D-printed structures, including stability testing of emitted current across multiple samples.

Název v anglickém jazyce

Testing the Performance of Tungsten-Graphite Cathodes as Electron Sources for MEMS Electron Microscopes

Popis výsledku anglicky

ALLAHAM, M. M., KNÁPEK, A., BURDA, D., MOUSA, M. S. Testing the Performance of Tungsten-Graphite Cathodes as Electron Sources for MEMS Electron Microscopes. In: OTÁHAL, A., KNÁPEK, A., SKÁCEL, J., NOVOTNÁ, V., eds. IMAPS Flash Conference. 11th International Microelectronics Assembly and Packaging Society Flash Conference. Brno: Brno University of Technology, FEEC, 2025, č. 25, s. 57-58. ISBN 978-80-214-6369-1. MEMS technology enables the development of miniature electron microscopes, commonly referred to as MEMS electron microscopes. These systems employ field-emission electron guns designed to generate a stable electron beam with a small spot size, high emission current density, and long operational lifetime, which is essential for achieving high-quality microscopic imaging. However, traditional uncoated tungsten field emission cathodes exhibit several limitations when operated outside ultra-high vacuum conditions, including high threshold voltages, limited lifetime, short operation time, and a widely dispersed electron beam. Recent studies have demonstrated that coating the nano-apex of such cathodes with graphene nanolayers can significantly improve their performance, particularly in scanning tunneling microscopy under non-ultra-high vacuum conditions. Additionally, excellent field emission characteristics have been observed in amorphous exfoliated graphite flakes applied to micro glass tips. In this study, tungsten nano-tips were prepared and cleaned using an electrochemical etching process, and subsequently integrated into a 3D-printed field emission microscope comprising a cylindrical sample holder, a cylindrical extractor with a 2 mm aperture, and a cylindrical Einzel lens system with a 4 mm aperture. The electrodes were coated with gold and further treated with a layer of colloidal graphite to ensure optimal electrical conductivity. Tungsten-graphite cathodes were then fabricated by coating the entire cathode surface with an exfoliated isopropyl-graphite solution, ensuring full surface coverage including the nano-apex with graphene nanofilms, thereby enabling electron emission directly from the graphite layer. These cathodes were experimentally evaluated within the 3D-printed microscope setup to characterize the field emission properties of the generated electron beam, including current density, spot size, lifetime, operational stability, field enhancement factor, voltage conversion length, and effective emission area. Furthermore, their applicability as electron sources for MEMS electron microscopes was assessed through experimental measurements and simulations based on the 3D-printed structures, including stability testing of emitted current across multiple samples.

Druh

O - Ostatní výsledky

CEP obor

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OECD FORD obor

10302 - Condensed matter physics (including formerly solid state physics, supercond.)

Projekt

<a href="/cs/project/GF25-19981L" target="_blank" >GF25-19981L: INFASCOPE – Integrovaná analýza autoemisních zdrojů</a><br>

Návaznosti

I - Institucionalni podpora na dlouhodoby koncepcni rozvoj vyzkumne organizace

Rok uplatnění

2025

Kód důvěrnosti údajů

S - Úplné a pravdivé údaje o projektu nepodléhají ochraně podle zvláštních právních předpisů