Angular Dependence of the Apparent Work Function of Carbon-Adsorbed Tungsten Tip

Unusually oriented carbon-adsorbed tungsten tips are made by a method developed by the present authors. Changes of the apparent work function and of the emission current on several crystal planes of these tips are measured in a F.E.M. tube as a function of angular distance from its apex. It is found that the work functions of the crystal planes become small in order of {110}, {100}, {221} and {210}, and also that the change in the apparent work function with the increase in angular distance becomes pronounced in this order. The crystal plane having smaller work function is found to show more pronounced decrease of emission current with the increase of angular distance from the apex compared with the crystal plane having larger work function.