Sintering of cobalt nanoclusters on Ag(1 1 1) by sulfur: Formation of one-, two-, and three-dimensional cobalt sulfide

Three different cobalt sulfur structures of different dimensionality and order develop upon interaction of sulfur with nanometer-sized cobalt clusters grown on Ag(1 1 1). We investigate the formation and transformation of these structures by fast-scanning tunneling microscopy. Initially, a meta-stable quasi one-dimensional structure consisting of double rows forms, and a disordered two-dimensional structure results from a collapse of the rows. However, the final thermodynamically stable structure is again crystalline and three-dimensional, and the nucleation and growth of this structure indicate that the kinetics is interface-limited.