Kinetic roughening is not a phase transition and, as such, it lacks a sharp
definition. Therefore, the many criteria used to mark the onset of kinetic
roughening, are expected to give different results. Criteria stemming from
the classical two-dimensional nucleation theory are frequently used. Exper
imentalists, on the other hand, observe a transition from flat to rounded c
rystal facets at certain driving forces, or measure the growth rate as a fu
nction of the driving force and find a change from exponential to linear gr
owth kinetics. It is assumed that these experimental phenomena coincide wit
h the onset of kinetic roughening. In this paper, the extent of the differe
nces between these criteria is investigated by means of Monte Carlo simulat
ions on a Kossel (1 0 0) SOS model. The four criteria studied yield differe
nt values for the critical driving force, although three of them show a sim
ilar, almost linear, dependence of the critical driving force on the neares
t-neighbor bond strength. (C) 1999 Elsevier Science B.V. All rights reserve
d.