Photoconductive, dielectric and percolation properties of anodic TiO.sub.2./sub. nanotubes studied by terahertz spectroscopy

0489478 - FZÚ 2019 RIV GB eng J - Journal Article
Kuchařík, Jiří - Sopha, H. - Krbal, M. - Rychetský, Ivan - Kužel, Petr - Macák, J. M. - Němec, Hynek
Photoconductive, dielectric and percolation properties of anodic TiO₂ nanotubes studied by terahertz spectroscopy.
Journal of Physics D-Applied Physics. Roč. 51, č. 1 (2018), s. 1-9, č. článku 014004. ISSN 0022-3727. E-ISSN 1361-6463
R&D Projects: GA ČR GA17-03662S
Institutional support: RVO:68378271
Keywords : anodic TiO₂ nanotubes * terahertz spectroscopy * charge transport * dielectric properties
OECD category: Condensed matter physics (including formerly solid state physics, supercond.)
Impact factor: 2.829, year: 2018

Self-organized layers of anodic TiO2 nanotubes were investigated by time-resolved terahertz spectroscopy in the steady state and upon photoexcitation. The interpretation of the conductivity spectra is based on the response of confined charges calculated by the Monte-Carlo method and on the evaluated distribution of the probing terahertz electric field in the heterogeneous structure. We show that the charge motion perpendicular to the nanotube axis is confined on ~10 nm scale, and that the charge mobility inside these confinement areas is comparable to that observed in a bulk anatase crystal. The electrical connectivity between individual nanotubes assessed from the terahertz spectra qualitatively correlates with the geometry observed in SEM images. The measured transient terahertz transmission spectra feature an apparent resonance. We demonstrate that it is not a signature of a new low-energy excitation but a geometrical effect of Fabry–Pérot interferences in the photoexcited slab.
Permanent Link: http://hdl.handle.net/11104/0283887