Local Crystallization of ${\rm LaB}_{6}$ Yielding Compact, Strong Thermionic Electron Emission Source

Local microheating of amorphous LaB₆ film could control the degree of crystallization as determined by spatially resolved Raman spectroscopy and transmission electron microscopy. With full crystallization of the LaB₆, we achieved micrometer-sized thermionic electron emission source with the maximum current density of 1.2 A/cm². The advantage of fabricating a micrometer-sized emitter with high current density enables versatile applications such as compact X-ray or vacuum type terahertz radiation sources. A new structure of micrometer-sized, lateral-type vacuum channel transistor is proposed based on the simulation. The calculated electron travelling time from emitter-to-collector was 8.3 ps at the traveling distance of ~10 μm, meaning that the maximum operation frequency is 120 GHz.