A first low-energy quasi-elastic He-atom scattering study was made of adsorbate atom diffusion. At 820K, S adatoms segregated onto the close-packed (111) surface of monocrystals at a rate of about 0.01monolayers/h. These adatoms produced an appreciable diffuse intensity of scattered He. Quasi-elastic energy broadening data indicated that these atoms were highly mobile. The deduced diffusion coefficient of 2.9 x 10-5cm2/s exhibited no dependence upon surface coverage; thus suggesting that the S-S interactions on this substrate were relatively weak.

B.J.Hinch, J.W.M.Frenken, G.Zhang, J.P.Toennies: Surface Science, 1991, 259[3], 288-300