- ZHANG.Han@nims.go.jp
- Address
- 305-0047 1-2-1 Sengen Tsukuba Ibaraki JAPAN [Access]
Research
PublicationsNIMS affiliated publications since 2004.
Published patent applications
Center for Basic Research on Materials
Next generation electron microscopes using a cold field emission LaB6 nanowire
LaB6，nanotechnology，electron source, cold field emission， electron microscope， SEM， TEM， semiconductor inspection
Overview
Cold field emission (CFE) produces the brightest and the most monochromatic electron beam. Such electron beam is highly demanded in application of electron microscopy for use in material research, pharmaceutic discovery and semiconductor manufacturing. For a long time, wide application of CFE was hindered because it suffers from emission instability in conventional vacuum condition and a low angular current density. We produced nanowires of LaB6 material one out of 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 from compact tabletop SEMs, atomic-resolution aberration-corrected TEMs to semiconductor inspection machines.
Novelty and originality
- LaB6 nanowires are synthesized as single crystalline without defects or inpurity;
- We developed nano-manipulation method to assemble single-nanowire emitter with high speed and high quality;
- LaB6 nanowire emitter produced electron beam with energy spread of 0.2eV;
- Brightness is 100 times higher than state-of-the art Tungsten single crystal cold field emitter;
- 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;
- Extraction voltage below 200V is enough to generate high density electron emission. (Tungsten: ~3000V)
Details
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 special 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)
Summary
Recently, material research and semiconductor manufacturing both approached precision of 1nm. As the eye of industry, electron microscopy with high resolution is increasingly demanded. The high brightness, monochromaticity and endurance of the LaB6 nanowire emitter not only enhances resolution of the current electron microscope tools, but also lead to invention of new generation electron microscopes of more compact design, lower equipment cost and faster analysis speed.
