  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 vapour
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 1.1 eV.
