Development of an Ultra-Bright Electron Source of Scanning Transmission Electron Microscopy

65083 The field emission electron source is a key element in powerful electron microscopes that characterize matter on the atomic scale, but the brightness, coherence, and stability are no longer sufficient to investigate materials at the level of resolution demanded by modern industry. Specifically, brightness needs to be improved by a factor of ten, the energy spread needs to be decreased 2-3 times, and the overall stability, reliability, and user-friendliness all must be improved substantially. This project will develop a 200 keV field emission electron source using a Zr/O/W(100) or similar low workfunction emitter. The new source is expected to have unprecedented brightness (>1010A cm-2 sr-1eV-1 at 200 keV), monochromaticity (10 hours between emitter cleanings, >10 years lifetime of the emitter), surpassing all existing electron sources. Phase I developed and tested a new type of electron source with the desired properties: increased brightness, decreased energy spread, and improved longevity. The source, using a Zr/O/W(100) cathode operated at liquid nitrogen temperature, achieved a workfunction of 2.7 eV, angular confinement of emission to within ¿4¿, emission noise 8 hours between cleanings. Phase II will develop a new type of electron accelerator that allows the electron source to be held at 78K in an ultra-clean, ultra-high vacuum. New high-voltage electronics also will be developed with extensive computer control that provides unprecedented stability at 200 keV and completely automated operation. Commercial Applications and Other Benefits as described by the awardee: The new source should ultimately be incorporated in an advanced electron microscope that will provide revolutionary new capabilities for imaging and analyzing matter. The world-wide market for such instruments is greater than $500 million, and there is no U.S. manufacturer.