KINETIC-THEORY OF SURFACE MIGRATION

The mechanism of surface migration is considered to be due to the competition between the adatom energy relaxation and the motion in the migration state above the activation energy. If the relaxation is retarded, the multiple-site hoppings become noticeable, otherwise the model of jumps into the nearest neighbour site is valid. To compute the jump probabilities we use the kinetic equation where the convection is described as particle exchange between adjacent surface cells. The last statement is justified at efficient randomisation of motion in the migration state which is confirmed for the bcc (110) face by direct numerical simulation. The corresponding rate constant is linear in energy in the most important region. The estimated jump probabilities into second nearest sites for W/W(110) self-diffusion are of a few percent at room temperature but they have a drastic temperature dependence.