Enhanced clustering tendency of Cu-impurities with a number of oxygen vacancies in heavy carbon-loaded TiO2 - the bulk and surface morphologies

Abstract

The over threshold carbon-loadings (~50 at.%) of initial TiO2-hosts and posterior Cu-sensitization (~7 at.%) was made using pulsed ion-implantation technique in sequential mode with 1 hour vacuum-idle cycle between sequential stages of embedding. The final Cx-TiO2:Cu samples were qualified using XPS wide-scan elemental analysis, core-levels and valence band mappings. The results obtained were discussed on the theoretic background employing DFT-calculations. The combined XPS and DFT analysis allows to establish and prove the final formula of the synthesized samples as Cx-TiO2:[Cu+][Cu2+] for the bulk and Cx-TiO2:[Cu+][Cu0] for thin-films. It was demonstrated the in the mode of heavy carbon-loadings the remaining majority of neutral C-C bonds (sp3-type) is dominating and only a lack of embedded carbon is fabricating the O-C=O clusters. No valence base-band width altering was established after sequential carbon-copper modification of the atomic structure of initial TiO2-hosts except the dominating majority of Cu 3s states after Cu-sensitization. The crucial role of neutral carbon low-dimensional impurities as the precursors for the new phases growth was shown for Cu-sensitized Cx-TiO2 intermediate-state hosts.