The diffusion of Cs on (100) was studied by using biased secondary electron imaging methods which were capable of detecting Cs coverages of more than 0.005 of a monolayer. Unusual diffusion profiles, which were linear at low coverages and had edges which expanded as t½, were obtained at coverages of less than half of a monolayer. The results were modelled by assuming a diffusion coefficient which was of the form, D1 + D2(A/kT)[(1-)], where  was the coverage. This form was consistent with a diffusion theory which took account of strongly repulsive Cs-Cs interactions, as deduced from a decrease in the adsorption energy, q, as a function of coverage (dq/d = 2eV/monolayer). The diffusivity at temperatures ranging from 60 to 90C was consistent with an adatom diffusion energy of 0.47eV.

Linear Diffusion Profiles due to Long Range Adsorbate Interactions: Cs/Si(100) at Low Coverage. R.H.Milne, M.Azim, R.Persaud, J.A.Venables: Physical Review Letters, 1994, 73[10], 1396-9