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Influence of Surface Cleaning on Quantum Efficiency, Lifetime and Surface Morphology of p-GaN:Cs Photocathodes

Accelerator scientists have high demands on photocathodes possessing high quantum efficiency (QE) and long operational lifetime. p-GaN, as a new photocathode type, has recently gained more and more interest because of its ability to form a negative electron affinity (NEA) surface. Being activated wi...

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Autores principales: Schaber, Jana, Xiang, Rong, Teichert, Jochen, Arnold, André, Murcek, Petr, Zwartek, Paul, Ryzhov, Anton, Ma, Shuai, Gatzmaga, Stefan, Michel, Peter, Gaponik, Nikolai
Formato: Online Artículo Texto
Lenguaje:English
Publicado: MDPI 2022
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9227593/
https://www.ncbi.nlm.nih.gov/pubmed/35744463
http://dx.doi.org/10.3390/mi13060849
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author Schaber, Jana
Xiang, Rong
Teichert, Jochen
Arnold, André
Murcek, Petr
Zwartek, Paul
Ryzhov, Anton
Ma, Shuai
Gatzmaga, Stefan
Michel, Peter
Gaponik, Nikolai
author_facet Schaber, Jana
Xiang, Rong
Teichert, Jochen
Arnold, André
Murcek, Petr
Zwartek, Paul
Ryzhov, Anton
Ma, Shuai
Gatzmaga, Stefan
Michel, Peter
Gaponik, Nikolai
author_sort Schaber, Jana
collection PubMed
description Accelerator scientists have high demands on photocathodes possessing high quantum efficiency (QE) and long operational lifetime. p-GaN, as a new photocathode type, has recently gained more and more interest because of its ability to form a negative electron affinity (NEA) surface. Being activated with a thin layer of cesium, p-GaN:Cs photocathodes promise higher QE and better stability than the known photocathodes. In our study, p-GaN samples grown on sapphire or silicon were wet chemically cleaned and transferred into an ultra-high vacuum (UHV) chamber, where they underwent a subsequent thermal cleaning. The cleaned p-GaN samples were activated with cesium to obtain p-GaN:Cs photocathodes, and their performance was monitored with respect to their quality, especially their QE and storage lifetime. The surface topography and morphology were examined by atomic force microscopy (AFM) and scanning electron microscopy (SEM) in combination with energy dispersive X-ray (EDX) spectroscopy. We have shown that p-GaN could be efficiently reactivated with cesium several times. This paper systematically compares the influence of wet chemical cleaning as well as thermal cleaning at various temperatures on the QE, storage lifetime and surface morphology of p-GaN. As expected, the cleaning strongly influences the cathodes’ quality. We show that high QE and long storage lifetime are achievable at lower cleaning temperatures in our UHV chamber.
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spelling pubmed-92275932022-06-25 Influence of Surface Cleaning on Quantum Efficiency, Lifetime and Surface Morphology of p-GaN:Cs Photocathodes Schaber, Jana Xiang, Rong Teichert, Jochen Arnold, André Murcek, Petr Zwartek, Paul Ryzhov, Anton Ma, Shuai Gatzmaga, Stefan Michel, Peter Gaponik, Nikolai Micromachines (Basel) Article Accelerator scientists have high demands on photocathodes possessing high quantum efficiency (QE) and long operational lifetime. p-GaN, as a new photocathode type, has recently gained more and more interest because of its ability to form a negative electron affinity (NEA) surface. Being activated with a thin layer of cesium, p-GaN:Cs photocathodes promise higher QE and better stability than the known photocathodes. In our study, p-GaN samples grown on sapphire or silicon were wet chemically cleaned and transferred into an ultra-high vacuum (UHV) chamber, where they underwent a subsequent thermal cleaning. The cleaned p-GaN samples were activated with cesium to obtain p-GaN:Cs photocathodes, and their performance was monitored with respect to their quality, especially their QE and storage lifetime. The surface topography and morphology were examined by atomic force microscopy (AFM) and scanning electron microscopy (SEM) in combination with energy dispersive X-ray (EDX) spectroscopy. We have shown that p-GaN could be efficiently reactivated with cesium several times. This paper systematically compares the influence of wet chemical cleaning as well as thermal cleaning at various temperatures on the QE, storage lifetime and surface morphology of p-GaN. As expected, the cleaning strongly influences the cathodes’ quality. We show that high QE and long storage lifetime are achievable at lower cleaning temperatures in our UHV chamber. MDPI 2022-05-29 /pmc/articles/PMC9227593/ /pubmed/35744463 http://dx.doi.org/10.3390/mi13060849 Text en © 2022 by the authors. https://creativecommons.org/licenses/by/4.0/Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/).
spellingShingle Article
Schaber, Jana
Xiang, Rong
Teichert, Jochen
Arnold, André
Murcek, Petr
Zwartek, Paul
Ryzhov, Anton
Ma, Shuai
Gatzmaga, Stefan
Michel, Peter
Gaponik, Nikolai
Influence of Surface Cleaning on Quantum Efficiency, Lifetime and Surface Morphology of p-GaN:Cs Photocathodes
title Influence of Surface Cleaning on Quantum Efficiency, Lifetime and Surface Morphology of p-GaN:Cs Photocathodes
title_full Influence of Surface Cleaning on Quantum Efficiency, Lifetime and Surface Morphology of p-GaN:Cs Photocathodes
title_fullStr Influence of Surface Cleaning on Quantum Efficiency, Lifetime and Surface Morphology of p-GaN:Cs Photocathodes
title_full_unstemmed Influence of Surface Cleaning on Quantum Efficiency, Lifetime and Surface Morphology of p-GaN:Cs Photocathodes
title_short Influence of Surface Cleaning on Quantum Efficiency, Lifetime and Surface Morphology of p-GaN:Cs Photocathodes
title_sort influence of surface cleaning on quantum efficiency, lifetime and surface morphology of p-gan:cs photocathodes
topic Article
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9227593/
https://www.ncbi.nlm.nih.gov/pubmed/35744463
http://dx.doi.org/10.3390/mi13060849
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