Surface mass diffusion and step stiffness on V(011)

By step fluctuation experiments on V(011) thin films grown on (11 2- 0) α- Al2 O3, using low energy electron microscopy, we determine the coefficient of surface mass diffusion Ds in the temperature range of 1170 K<T<1560 K, centered near 0.6 Tm, with the melting temperature Tm =2183 K for V. As is common to annealed V, Nb, and Ta in UHV, submonolayer coverages of O were present on the otherwise clean and well-defined surface. We obtain Ds =0.8 exp (-1.43 eV kB T) cm2 s for this temperature interval. Compared to Nb(011), the step stiffness obtained from the measurements is relatively small and isotropic at ∼60 meVnm. Sublimation is made visible by uphill step flow above 1460 K, with a temperature dependence consistent with the known cohesive energy.