  In this work we have employed density-functional theory with hybrid
functionals to investigate the atomic and electronic structure of bare and
hydrogenated Co doped ZnO nanowires. We find that in the absence of passivation
on the nanowire surface, the cobalt atoms segregate to the surface. On the
other hand, under hydrogen passivation, the incorporation of Co is more
favorable at inner sites. This suggests that the incorporation of Co in
nanostructures has a dependence on the environment and may be facilitated by
external atoms and relaxation of the surface.
