Surface Diffusion Phenomena in Gaseous Diffusion, (I)

The surface diffusion in localized monolayers is discussed. The authors regard the surface diffusion phenomena as the random walk of the so-called “hopping molecules” on a solid surface. It is assumed that when a molecule adsorbed in a site jumps to one of the nearest neighbor sites the molecule can jump to any one of them whether it is vacant or not, and if the site to which a molecule jumps has been already occupied the molecule is not bound to this site but collides with the former occupant and scatters isotropically. On the basis of this new model for surface diffusion mechanism, we introduce the approximate relation between surface diffusion coefficient and coverage.The proposed new model is examined by various experimental data, and some of the approximations and assumptions used in the model are discussed.