Work Function Characterization of the Directionally Solidified LaB6 VB2 Eutectic

TL;DR

This study investigates the work function distribution in LaB6/VB2 eutectic using microscopy and spectroscopy, revealing lower work functions on VB2 inclusions and significant reductions after vanadium deposition, relevant for thermionic emitter development.

Contribution

It combines advanced microscopy and spectroscopy techniques to analyze work function variations in LaB6/VB2 eutectic, providing new insights into surface properties for device applications.

Findings

Lower work function on VB2 inclusions compared to LaB6 matrix

Vanadium monolayer deposition significantly reduces work function to as low as 1.1 eV

Work function variations correlate with chemical and physical surface conditions

Abstract

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.