Pleomorphic structural imperfections caused by pulsed Bi-implantation in   the bulk and thin-film morphologies of TiO2
  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. 
D.A. Zatsepin, D.W. Boukhvalov, E.Z. Kurmaev, N.V. Gavrilov, S. S.   Kim, I. S. Zhidkov
cond-mat.mtrl-sci