The diffusion and coarsening of two-dimensional homoepitaxial islands
on Cu(100) and Ag(100) surfaces have been studied at room temperature
with time-sequenced scanning tunneling microscopy. Quantitative analys
es of the dependence of island diffusion coefficient D vs the island s
ide length L, D proportional to L-alpha, yield noninteger scaling expo
nents which are consistent with island coalescence. Moreover, the near
absence of island decay shows that the island diffusion occurs via ma
ss transport along the island periphery.