Changes in the Surface Electronic State of CeB6 Single Crystals Induced by Oxidation: Effects on Field Emission

Cerium hexaboride (CeB6) is a promising field emission electron emitter due to its low work function and high thermal stability. This study examines the surface properties of CeB6 (100) and (310) single crystals under oxygen exposure and thermal oxidation. Clean surfaces exhibited low work functions but showed rapid degradation due to oxygen adsorption. Oxygen exposure increased the work function up to 4.09 eV, while thermal oxidation produced a stable surface with a lower work function (~3.26 eV). XPS analysis revealed the formation of B2O3 and Ce⁴⁺ species, suggesting that a thin oxidized subsurface layer serves as a passivation film, enhancing surface stability.