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Long term operation of high quantum efficiency GaAs(Cs,O) photocathodes using multiple recleaning by atomic hydrogen.
- Source :
-
Journal of Applied Physics . Sep2009, Vol. 106 Issue 5, p054907-054914. 7p. 1 Color Photograph, 1 Diagram, 1 Chart, 3 Graphs. - Publication Year :
- 2009
-
Abstract
- Atomic hydrogen, produced by thermal dissociation of H2 molecules inside a hot tungsten capillary, is shown to be an efficient tool for multiple recleaning of degraded surfaces of high quantum efficiency transmission-mode GaAs photocathodes within an ultrahigh vacuum (UHV) multichamber photoelectron gun. Ultraviolet quantum yield photoemission spectroscopy has been used to study the removal of surface pollutants and the degraded (Cs,O)-activation layer during the cleaning procedure. For photocathodes grown by the liquid-phase epitaxy technique, the quantum efficiency is found to be stable at about 20% over a large number of atomic hydrogen cleaning cycles. A slow degradation of the quantum efficiency is observed for photocathodes grown by metal-organic chemical vapor deposition, although they reached a higher initial quantum efficiency of about 30%–35%. Study of the spatial distributions of photoluminescence intensity on these photocathodes proved that this overall degradation is likely due to insertion of a dislocation network into the mechanically strained photocathode heterostructures during multiple heating cycles and is not due to the atomic hydrogen treatment itself. [ABSTRACT FROM AUTHOR]
Details
- Language :
- English
- ISSN :
- 00218979
- Volume :
- 106
- Issue :
- 5
- Database :
- Academic Search Index
- Journal :
- Journal of Applied Physics
- Publication Type :
- Academic Journal
- Accession number :
- 44193540
- Full Text :
- https://doi.org/10.1063/1.3208054