Abstract
The deposition of tin on a tungsten emitter tip and subsequent heating above 700 °C results in a drastic change of the equilibrium shape of the emitter at an elevated temperature and the formation of a surface layer with unusual structure. The new surface layer requires a significantly higher external electric field to cause the migration of surface atoms than a bare tungsten surface layer. A tentative explanation is the formation of a closely packed two‐dimensional alloy of transition and nontransition metals.