  We present the cationic impurity assisted band offset phenomena in NixCd1-xO
(x= 0, 0.02, 0.05, 0.1, 0.2, 0.4, 0.8, 1) thin films and further discussed in
the light of orbital hybridization modification. Compositional and structural
studies revealed that cationic substitution of Cd2+ by Ni2+ ions leads to a
monotonic shift in (220) diffraction peak, indicating the suppression of
lattice distortion while evolution of local strain with increasing Ni
concentration mainly associated to the mismatch in electro-negativity of Cd2+
and Ni2+ ion. In fact, Fermi level pinning towards conduction band minima takes
place with increasing Ni concentration at the cost of electronically
compensated oxygen vacancies, resulting modification in the distribution of
carrier concentration which eventually affects the band edge effective mass of
conduction band electrons and further endorses band gap renormalization.
Besides that, the appearance of longitudinal optical (LO) mode at 477 cm-1 as
manifested by Raman spectroscopy also indicate the active involvement of
electron-phonon scattering whereas modification in local coordination
environment particularly anti-crossing interaction in conjunction with presence
of satellite features and shake-up states with Ni doping is confirmed by X-ray
absorption near-edge and X-ray photoelectron spectroscopy studies. These
results manifest the gradual reduction of orbital hybridization with Ni
incorporation, leading to decrement in the band edge effective mass of
electron. Finally, molecular dynamics simulation reflects 13% reduction in
lattice parameter for NiO thin film as compared to undoped one while projected
density of states calculation further supports the experimental observation of
reduced orbital hybridization with increasing Ni concentration.
