  We report first principles theory based electronic structure studies of a
semiconducting stoichiometric cage-like Cd9Te9 cluster. Substantial changes are
observed in the electronic structure of the cluster on passivation with
fictitious hydrogen atoms, in particular, widening of the energy gap between
highest occupied molecular orbital and lowest unoccupied molecular orbital and
enhancement in stability of cluster is seen. The cluster, when substitutionally
mono-doped for a Cd by a set of 3d and 4d transition metal atoms (Ti, V, Cr,
Mn, Fe, Co, Ni, Cu, Zn, Ru, Rh and Pd), is found to acquire polarization as
seen from spin resolved density of states near Fermi level. Further, such
mono-doping in passivated cluster shows half-metallic behavior. Mapping of
partial density of states of each system on that of undoped cluster reveals
additional levels caused by doping each TM atom separately. In the 3d elemental
doping, Ti and Mn doping result into electron type doping whereas all other
cases result into hole doped systems. For all the 4d elements studied, it is
akin to the doping with holes for Cd substitution in the outer ring, whereas
for Ru and Rh, there is electron type doping in case of substitution for Cd in
central ring upon passivation. A comparison of partial density of states plots
for bare and passivated clusters, on doping with transition metal atoms,
suggests suitability of the cage-like cluster for spintronics applications.

Materials Science;Mesoscale and Nanoscale Physics;Atomic and Molecular Clusters