York Probe Sources - electron emission modules Schottky sources, Schottky field emission, field emission cathodes, field electron emission, Schottky emitters, thermal field emission, TFE, electron microscopy, scanning electron microscopy, electron columns, ultrahigh vacuum, surface science, surface analysis, FIB, SIMS, XPS, instrumentation, Auger spectroscopy, Auger microscopy Offers electron emission modules and products for research and industry, based at the University of York