A Study of SiC Nanostructures Grown on Si Substrate as Thermionic Cathode and its Work Function Lowering Effect

Silicon carbide (SiC) nanostructures were synthesized on a silicon (Si) substrate that served as a thermionic cathode. Nanosheets, nanograins, and high-aspect-ratio nanostructures formed on the thermionic cathodes, depending on the synthesis parameters. The calculated work functions of thermionic cathodes ranged from 4.48 eV to 4.83 eV. It can be observed that the work function is attributed to the geometrical characteristics, such as the aspect ratios and the surface-area-to-volume ratios of SiC nanostructures. Among the nanostructures, using SiC nanowire structures (M200SC3) resulted in the greatest reduction in the thermionic cathode's work function, which was 0.36 eV. This reduction is attributed to the sharp-tip structures having high aspect ratios, which is a strong field enhancement factor to the electron emission. This study suggests that the presence of SiC nanostructures on a thermionic cathode can potentially enhance electron emission in a thermionic energy converter (TEC) system.