| Autor: |
Jana Schaber, Rong Xiang, Jochen Teichert, André Arnold, Petr Murcek, Paul Zwartek, Anton Ryzhov, Shuai Ma, Stefan Gatzmaga, Peter Michel |
| Jazyk: |
angličtina |
| Rok vydání: |
2023 |
| Předmět: |
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| Zdroj: |
Scientific Reports, Vol 13, Iss 1, Pp 1-12 (2023) |
| Druh dokumentu: |
article |
| ISSN: |
2045-2322 |
| DOI: |
10.1038/s41598-023-30329-0 |
| Popis: |
Abstract This study shows residual surface carbon’s influence on photocathodes’ quantum efficiency based on p-GaN grown on sapphire by metal organic chemical vapor deposition. An X-ray photoelectron spectrometer (XPS) built in an ultrahigh vacuum system allowed the in-situ monitoring of the photocathode surface beginning immediately after their cleaning and throughout the activation and degradation processes. An atomically clean surface is necessary to achieve a negative electron affinity, which is the main prerequisite for high quantum efficiency. The p-GaN samples were cleaned with ethanol and underwent a sub-sequential thermal vacuum cleaning. Although carbon and oxygen contaminations are expected to be undesired impurities from the metal organic chemical vapor deposition, which remained on the surface, p-GaN could still form a negative electron affinity surface when exclusively activated with cesium. After the activation with cesium, a shift to a higher binding energy of the photoemission peaks was observed, and a new species, a so-called cesium carbide, was formed, growing over time. The XPS data elucidated the critical role of these cesium carbide species in photocathode degradation. The X-ray damage to the p-GaN:Cs photocathodes, especially the influence on the cesium, was additionally discussed. |
| Databáze: |
Directory of Open Access Journals |
| Externí odkaz: |
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