  In the atom probe microanalysis of steels, inconsistencies in the measured
compositions of solutes (C, N) have often been reported, as well as their
appearance as molecular ions. Here we propose that these issues might arise
from surface migration of solute atoms over the specimen surface. Surface
migration of solutes is evidenced by field-ion microscopy observations, and its
consequences on atom probe microanalysis are detailed for a wide range of
solute (P, Si, Mn, B, C, N). It is proposed that directional walk driven by
field gradients over the specimen surface and thermally activated is the
prominent effect.
