FIELD-EMISSION BARRIER HEIGHT OF AN ALLOY TIP - POSSIBLE EFFECT OF SURFACE SEGREGATION

We have investigated the influence of surface segregation on the field -emission characteristics of alloy emitters. Our tip material is a Ni- 0.8 at. % Au alloy where gold segregates to the surface. Emission barr ier height was obtained from the slope of the Fowler-Nordheim plot ass uming the field proportionality constant estimated from the best image voltage in the field-ion imaging. Upon annealing the alloy tip at 700 K, the barrier height is found to decrease by similar to 0.5 eV. As n o lowering of the barrier height was observed in an annealed Ni tip, t he observed reduction of the barrier height is attributable to the sur face enrichment of gold due to its partial segregation. Our findings t hus support the claim by Yoshihara and Yoshitake [J. Vac. Sci. Technol . A 13, 2407 (1995)] that the surface segregation can be used as a met hod for improving the emission characteristics of field emitters. (C) 1997 American Vacuum Society.