Kinetic Coefficients in a System Far from Equilibrium

Abstract

The kinetic coefficients in a growing surface are very different from their equilibrium values. Assuming deposition of particles from a beam on an initially flat surface of high symmetry orientation and neglecting evaporation, the kinetic coefficients K ₀ and λ₀ relevant at the beginning of the growth are evaluated in 1+1 and 2+1 dimensions. K ₀ is the sum of three terms: i) a term coming from an “equilibrium” chemical potential, which vanishes with temperature but diverges at low flux in the case of a singular surface; ii) a term, whose origin is the random character of nucleation, which depends only on the beam intensity and the diffusion constant but is independent of the atomic distance; iii) a term deriving from the fluctuations of the diffusion current, which depends on the beam intensity, the diffusion length, and the atomic distance and, in 1+1 dimensions, only depends on the temperature through the diffusion length. The validity of a linear equation is limited to small slopes |m| < 1/ℓ _c , where ℓ _c is the maximum terrace width.