Faceting of curved tungsten surface induced by palladium

The influence of a palladium adlayer on the surface topography of a needle-shaped tungsten crystal is studied using field ion microscopy. When the curved surface is covered by palladium and annealed at 1000–1200 K, both macroscopic faceting and steplike microfaceting is observed. The macroscopic {1 1 0} and {2 1 1} crystal facets increase in size, {2 1 1} steplike microfacets are formed around 〈1 1 1〉 poles, {1 1 0} and {2 1 1} steplike microfacets are formed in 〈1 1 1〉 crystal zones. With the increase of annealing temperature the number of {2 1 1} microfacets decreases, while the macroscopic {2 1 1} facets increase in size. At 1300 K no faceting is observed because palladium desorbs thermally.