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Seminar | X-Ray Science

Understanding Low Work Function Perovskite Oxides for Thermionic Electron Emission Applications

XSD/MM Special Presentation

Abstract: Work function is one of the most important properties in science and technology involving material surfaces and interfaces. Pursuing lower work function electron emitters is particularly crucial for thermionic emission cathodes for vacuum electronic applications, especially with intrinsically polar materials such as perovskite oxides, since it is possible with these materials to overcome shortcomings of contamination and lifetime existing in current dispenser cathodes.

In this presentation, the experimental demonstrations of low work function perovskites SrVO3 will be introduced. A huge disagreement between density functional theory (DFT) predicted and ultraviolet photoelectron spectroscopy (UPS) measured work functions has been observed. With deep investigation on the surface chemistry and work function physics, this disagreement has been attributed to surface over-oxidation and patch field effect. These effects has been overcome with in-situ thermionic electron emission testing, in which SrVO3 has shown low 2.3 to 2.7 eV effective work function. This has been so far the lowest work function observed from a bulk monolithic conductive oxide material, promising for work function engineering including thermionic emission applications.