Publikationsrepositorium - Helmholtz-Zentrum Dresden-Rossendorf

Many applications of titanium dioxide (TiO₂) partially rely on its good performance as solvent for impurities [1]. For example, metal (cation) dopants can functionalize or enhance TiO₂ as catalyst [2], diluted magnetic semiconductor [3] or transparent conductor [4]. Special attention has been devoted to TiO₂ photoactivity where doping has been extensively studied towards band-gap narrowing to achieve visible-light (VISL) response [2]. Here, the most common approach has relied on anion (B,C,N,F,S,…) dopants triggered by the work of Asahi et al. [5]. However, cation (Cr,V,Fe,Ni,Mo,…) doping can also effectively increase VISL absorption but introducing severe structural distortions that additionally result in carrier recombination centers [4].
Our interest is focused on improving the structural quality of metal (co-)doped TiO₂ films by post-deposition rapid and non-contact thermal treatments such as flash-lamp-annealing (FLA). An additional objective is to do so with (single and mixed) phase selectivity. For example, the promotion of anatase would be preferable due to the superior photoactivity of this phase or phase mixtures with high anatase content [6]. In particular, in this paper we address the impact of FLA on pure and (co-)doped (Cr,N) TiO₂ films produced by magnetron sputtering as relevant systems for VISL photoactivity. The results on monolithic films [7] will be presented as well as promising alternatives to promote anatase by the use of modulated film architectures. The interest of FLA processing can also be extended to other dopants in TiO₂ for improving the photoactivity or any other functionality. Therefore, the reported methodology can be attractive for many industrial applications dealing with the synthesis of band-gap engineered TiO₂-based materials.
[1] Sacerdoti et al., J. Solid State Chem. 177, 1781 (2004); [2] Henderson, Surf. Sci. Rep. 66, 185 (2011); [3] Matsumoto et al. Science 291, 854 (2001); [4] Serpone et al., J. Phys. Chem. B 110, 24287 (2006); [5] Asahi et al. Science 293, 269 (2001) [6] Scanlon et al., Nat. Mater. 12, 798 (2013); [7] R. Gago, S. Prucnal et al., J. Alloys & Compounds 729 (2017) 438.