Metal-insulator photocathode heterojunction for directed electron emission
Timothy C Droubay1, Scott A Chambers1, Alan G Joly1
1Physical Sciences Division, Pacific Northwest National Laboratory, Richland, Washington 99352, USA.
Physical Review Letters
|March 4, 2014
Summary
Depositing magnesium oxide (MgO) onto silver (Ag(001)) significantly boosts electron emission. This enhancement makes the MgO/Ag(001) heterojunction a promising material for advanced photocathodes.
Area of Science:
- Surface Science
- Materials Science
- Condensed Matter Physics
Background:
- Silver (Ag(001)) surfaces are studied for electron emission.
- Understanding interface effects is crucial for optimizing material properties.
Purpose of the Study:
- To investigate the effect of epitaxial magnesium oxide (MgO) deposition on the electron emission properties of Ag(001).
- To explore the potential of MgO/Ag(001) heterojunctions as advanced photocathodes.
Main Methods:
- Angle-resolved photoemission spectroscopy using ultraviolet laser excitation.
- Deposition of a few monolayers of epitaxial MgO on a Ag(001) substrate.
Main Results:
- Electron emission properties of Ag(001) were markedly enhanced and redirected along the surface normal upon MgO deposition.
- New low-binding energy states with small surface parallel momentum spreads were observed due to MgO/Ag(001) interface formation.
- Quantum efficiency increased by a factor of 7 compared to clean Ag(001) under 4.66 eV laser excitation.
Conclusions:
- Epitaxial MgO deposition significantly enhances and redirects electron emission from Ag(001).
- The observed interface states are key to the improved performance.
- MgO/Ag(001) heterojunctions show great promise as advanced photocathodes.
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