Experimental determination of the {111}/{001} surface energy ratio for Pd crystals

Pd crystals grown in ultrahigh vacuum (UHV) on nanostructured SrTiO3(001) and anatase TiO2(001) thin film substrates were studied using scanning tunneling microscopy. The crystals have the equilibrium shape of a truncated octahedron with a {111} top facet, {111} and {001} side facets, and a {111} interface. A consistent crystal shape is reached only after annealing the samples in UHV at 450 degrees C or above. By measuring the top facet dimensions of the equilibrium crystals, we determine the ratio of the surface energies for Pd to be gamma 111 / gamma 001 = 0.77 +/- 0.02.