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LaB6 ナノワイヤ冷電界放出による新世代電子顕微鏡




Cold field emission (CFE) produces the brightest and the most monochromatic electron beam. Such electron beam is highly demanded in applicationof electron microscopy for use in material research, pharmaceutic discovery and semiconductor manufacturing. For a long time, wide application ofCFE was hindered because it suffers from emission instability in conventional vacuum condition. We produced nanowires of LaB6 material one outof 100 billion size of a conventional electron emitter. The combination of low work function and nanometric size produced an emission brightness100 times higher and stability 10 times better than conventional electron sources. Wide application of LaB6 nanowire CFE has been realized fromcompact tabletop SEMs to atomic-resolution aberration-corrected TEMs.


1. LaB6 nanowires are synthesized as single crystalline without defects or inpurity;
2. We developed nano-manipulation method to assemble single-nanowire emitter with high speed and high quality;
3. LaB6 nanowire emitter produced electron beam with energy spread of 0.2eV;
4. Brightness is 100 times higher than state-of-the art Tungsten single crystal cold field emitter;
5. No emission decay and probe current noise lower than 1% under vacuum of 1E-7Pa, which is 1000 times higher than that required by Tungsten CFE;
6. Extraction voltage of ~200V is enough to generate high density electron emission. (Tungsten: ~3000V)



We first used a chemical vapor deposition method to synthesize large quantity of LaB6 nanowires on a catalyzed substrate. (A) A single nanowire was picked up and assembled into a nanowire electron emitter using nano-manipulation method (B) A speical field evaporation method was used to form a clean and La atom terminated surface on the nanowire tip to enable stable high brightness electron emission. (C) Such an emitter was then installed into commercial electron microscopes to improve both energy and spatial resolution. (D) Using the nanowire emitter, we showed 0.2eV energy spread shown in the zero-loss peak of EELS and single atom resolution in STEM. (E)


Recently, material research and semiconductor manufacturing both approached precision of 1nm. As the eye of industry, electron microscopy withhigh resolution is increasingly demanded. The high brightness, monochromaticity and endurance of the LaB6 nanowire emitter not only enhancesresolution of the current electron microscope tools, but also lead to invention of new generation electron microscopes of more compact design, lowerequipment cost and faster analysis speed.