Miniature Schottky electron source

A miniature Schottky electron source has been developed and evaluated for applications in a new generation of scanning tunneling microscope aligned field emission microcolumns. Both the physical dimensions and the heating power of this source have been significantly reduced from a conventional source of the same kind. Operating parameters for such a source in a microcolumn environment in terms of emission characteristics, suppressor operating range, etc., have been evaluated. Test results show that very good emission stability at greater than or equal to 100 mu A emission current over several hours, and axial angular current densities in excess of 100 mu A/sr can be obtained. Energy distributions have been measured using a carefully calibrated analyzer, and the results show a full width at half-maximum of 0.4 to 0.76 eV for a 0.3 mu m radius Schottky source operating over an angular current density range of 1 to over 100 mu A/sr. A significant change in the shape of the energy distribution was observed over this range of operation, indicating evidence of tunneling currents at the high angular current density regime. (C) 1995 American Vacuum Society.