  Surface doping of ZnO allows for tailoring the surface chemistry of the
material while preserving the superb electronic structure of the bulk. Apart
from obvious changes in adsorption energies and activation energies for
catalysis, surface doping can alter the workfunction of the material and allow
it to be tuned for specific photocatalytic and optoelectronic applications. We
present first-principles electronic structure calculations for surface doping
of Mn on the ZnO (0001) surface. Various dopant concentrations have been
considered at the out-most (surface) layer of Zn atoms, while the interior of
the material is kept at the ideal wurtzite structure. For each system, the
surface energy and surface workfunction have been calculated. Both workfunction
and surface energy drop with increasing Mn concentration for O-terminated
surfaces, while more complex behaviour is observed in metal-terminated ones. We
discuss trends in surface stability and surface electronic structure of this
material and how they affect its properties.
