Field electron emission properties of a supertip

We have operated a supertip-type field emitter to provide electron beams of low angular divergence and high intensity. The beams obtained from a supertip on a (111) W tip are characterized by narrow emission angles of alpha/2 approximate to 2 degrees, effective emission areas of A similar to 10 nm(2) and energy spreads of Delta E less than or equal to 0.5 eV (FWHM) at stable total emission currents of I approximate to 100 nA. The corresponding brightness figures favourably compare with those of conventional emitters in use for focused electron beam applications.