Experimental evaluation of a scanning tunneling microscope-microlens system

This paper presents the results of the first successfully fabricated scanning tunneling microscope (STM) aligned field emission (SAFE) microsource. SAFE sources have been shown to produce 2–3 orders of magnitude improvement in brightness over conventional field‐emission sources. Lens electrodes were fabricated from 1‐μm thick silicon membranes by electron‐beam lithography and reactive‐ion‐beam etching. Two‐element microlenses were tested in an ultrahigh vacuum (UHV) chamber with a piezo mounted tungsten tip and a dual feedback system. The sources demonstrated stable emission for periods of hours at beam energies of up to 1 kV. Measurement of the virtual source position showed good agreement with calculated values.