Work function characterization of directionally solidified LaB6–VB2 eutectic

•LaB6–VB2 eutectic shown to have low work function at phase boundary.•Vanadium dosing yielded work function values as low as 1.1eV.•Thermionic emission imaging showed primary emission to be on the VB2 phase With its low work function and high mechanical strength, the LaB6/VB2 eutectic system is an i...

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Bibliographic Details
Published in:Ultramicroscopy 2017-12, Vol.183 (C), p.67-71
Main Authors: Back, Tyson C., Schmid, Andreas K., Fairchild, Steven B., Boeckl, John J., Cahay, Marc, Derkink, Floor, Chen, Gong, Sayir, Ali
Format: Article
Language:English
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Summary:•LaB6–VB2 eutectic shown to have low work function at phase boundary.•Vanadium dosing yielded work function values as low as 1.1eV.•Thermionic emission imaging showed primary emission to be on the VB2 phase With its low work function and high mechanical strength, the LaB6/VB2 eutectic system is an interesting candidate for high performance thermionic emitters. For the development of device applications, it is important to understand the origin, value, and spatial distribution of the work function in this system. Here we combine thermal emission electron microscopy and low energy electron microscopy with Auger electron spectroscopy and physical vapor deposition of the constituent elements to explore physical and chemical conditions governing the work function of these surfaces. Our results include the observation that work function is lower (and emission intensity is higher) on VB2 inclusions than on the LaB6 matrix. We also observe that the deposition of atomic monolayer doses of vanadium results in surprisingly significant lowering of the work function with values as low as 1.1eV.
ISSN:0304-3991
1879-2723
DOI:10.1016/j.ultramic.2017.05.006