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Processing of Bulk Nanocrystalline Metals at the US Army Research Laboratory
Published on: March 7, 2018
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Work function characterization of directionally solidified LaB6-VB2 eutectic.
Tyson C Back1, Andreas K Schmid2, Steven B Fairchild3
1University of Dayton Research Institute, 300 College Park, Dayton, OH 45469-0170, USA; Air Force Research Laboratory, Materials and Manufacturing Directorate, 3005 Hobson Way, Wright-Patterson Air Force Base, OH 45433, USA.
Ultramicroscopy
|May 20, 2017
Summary
The LaB6/VB2 system shows promise for thermionic emitters. Vanadium deposition significantly lowers the work function, enhancing emission intensity for potential device applications.
Area of Science:
- Materials Science
- Surface Science
- Condensed Matter Physics
Background:
- Lanthanum hexaboride (LaB6) and Vanadium Diboride (VB2) eutectic systems offer a unique combination of low work function and high mechanical strength.
- These properties make them attractive for high-performance thermionic emitter applications.
Purpose of the Study:
- To investigate the work function's origin, value, and distribution in the LaB6/VB2 system.
- To understand the physical and chemical factors influencing the work function of these surfaces.
Main Methods:
- Combined use of thermal emission electron microscopy (TEEM) and low energy electron microscopy (LEEM).
- Auger electron spectroscopy (AES) for chemical analysis.
- Physical vapor deposition (PVD) for controlled elemental deposition.
Main Results:
- Observed lower work function and higher emission intensity on VB2 inclusions compared to the LaB6 matrix.
- Demonstrated a significant work function reduction (down to 1.1 eV) upon deposition of atomic monolayer doses of vanadium.
Conclusions:
- The spatial distribution of VB2 significantly impacts the work function of the LaB6/VB2 system.
- Vanadium surface modification is a promising strategy for achieving ultra-low work functions in thermionic emitters.
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