TiO2 is an important photocatalyst and is often used as a model system to understand the basic processes involved. Still, this material has some surprising properties with significant consequences not only in photocatalysis but also in photovoltaic applications. The transport of free carriers between bulk and surface is of fundamental interest for both. Based on calculations with the screened hybrid functional HSE06 (which is nearly free of the electron self-interaction error of standard approximations to density functional theory), we show that electrons can be self-trapped by a Ti(4+/3+) transition anywhere in bulk rutile. This does not happen in anatase, where holes get self-trapped by O(2-/1-) transitions. These properties of TiO2 influence the behavior of intrinsic defects [1], and also the separation of the photo-generated electron-hole pair. Anatase has no native electron traps impeding the electron mobility. We show that, particularly in nanowires, the existence of massless quasi-relativistic Dirac states in the conduction band may provide extreme high mobility values [2]. [1] P. De�k, B. Aradi, and T. Frauenheim, Phys. Rev. B 86 , 195206 (2012).[2] P. De�k et al., Nanoletters, 13 , 1073-1079 (2013).

Peculiarities of TiO<sub>?2</sub>: Carrier self-trapping and massless electron states

246th National Meeting (2013)

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Peculiarities of TiO?2: Carrier self-trapping and massless electron states

Peculiarities of TiO_?2: Carrier self-trapping and massless electron states