イベント

千現地区 研究本館8階 中セミナー室

ZHANG Han
Advanced Low-Dimensional Nanomaterials Group

Cold field emission of electrons is the brightest known form of particle emission. Electron microscopy demands the highest brightness from an electron source. However, emission current instability and stringent high vacuum requirement have made cold field emission gun less favored in the industry though it promises the highest performance. More than 20 years ago, nano-structured electron emitters have been found with much higher brightness and stability compared to the conventional W single crystal needle emitters. Difficulty in structure control over these nano-objects and their poor performance reliability have hindered further advancement towards real-life microscopy applications. After a brief review over historical efforts, I want to describe a new breakthrough in the field: a LaB6 nanowire with only a few La atoms bonded on the tip that emits collimated electrons from a single point with high monochromaticity. Installed in a commercial scanning electron microscope, the tip demonstrated: 3000 times current density gain over W (310) tips, no emission decay and noise level as low as 0.1%. The verified life time over 1000 hours and 100 times higher tolerable operating gas pressure have staged the new cold field emitter as the choice for the next generation electron microscopes.