  The results of combined experimental and theoretical study of substitutional
and clustering effects in Bi-doped TiO2 hosts (bulk and thin-film morphologies)
are presented. Bi-doping of the bulk and thin-film titanium dioxide was made
with help of pulsed ion-implantation (E(Bi+) = 30 keV, D = 1 * 1017 cm-2)
without posterior tempering. The X-ray photoelectron spectroscopy (XPS)
qualification (core-levels and valence bands) and Density-Functional Theory
(DFT) calculations were employed in order to study the electronic structure of
Bi-ion implanted TiO2 samples. According to XPS data obtained and DFT
calculations, the Bi -> Ti cation substitution occurs in Bi-implanted bulk
TiO2, whereas in the thin-film morphology of TiO2:Bi the Bi-atoms have
metal-like clusters segregation tendency. Based on the combined XPS and DFT
considerations the possible reasons and mechanism for the observed effects are
discussed. It is believed that established peculiarities of bismuth embedding
into employed TiO2 hosts are mostly the sequence of pleomorphic origin for the
formed "bismuth-oxygen" chemical bonding.
