Abstract
On growth of singular surface of crystal, the surface diffusion process plays an important role. The back-force effect is a reduction of the localized driving force due to the presence of the steps as sinks for the growth units on the surface. Introducing it into the BCF's spiral growth theory, the expansion of the interstep distance is caused and therefore the growth rate is reduced. In nucleation growth process, it causes significant reduction of the two-dimensional nucleation rate on the surface. Moreover, on already existing nucleus, the critical size of nucleus is greater than one derived from conventional nucleation theory. It may be called the effective critical radius. On the perfect surface, two-dimensional nucleation occurs here and there and may occur also on growing nucleus.
