RT Journal Article
T1 Band Gap Narrowing versus Formation of Electronic States in the Gap in N-TiO2 Thin Films.
A1 Romero-Gómez, Pablo
A1 Hamad, Said
A1 González, Juan Carlos
A1 Barranco, Ángel
A1 Espinós, Juan Pedro
A1 Cotrino, José
A1 González Elipe, Agustin
K1 Películas degadas
K1 Electrónica del estado sólido
AB N-containing TiO2 thin films with different amounts of nitrogen have been prepared by plasma enhancedchemical vapor deposition (PECVD) by using different titanium precursors without (titanium isopropoxide,TTIP) and with (tetrakis diethylamino titanium, TDEAT and tetrakis dimethylamino titanium, TDMAT) nitrogenin their structures and different N2/O2 ratios as plasma gas. For low/high content of nitrogen, Ti-NO- and/orTi-N-like species have been detected in the films by X-ray photoelectron spectroscopy (XPS). Their opticalbehavior is characterized by a red shift of their absorption edge when Ti-N species are a majority, and byan unmodified edge with localized absorption states in the gap when only Ti-NO-like species are present inthe film. The experimental results have been interpreted by calculating the density of states of model systemsconsisting of a 2 × 2 × 3 repetition of the anatase unit cell. This basic structure incorporates nitrogen defectsin either substitutional or interstitial lattice positions that are considered equivalent to the Ti-N- and Ti-NO-like species detected by XPS. To simulate the effect of, respectively, a low or a high concentration of nitrogen,calculations have been carried out by placing two nitrogen defects either in separated or in nearby positionsof the anatase structure. The computational analysis reveals that the defects have different stabilization energiesand confirm that an edge shift of the valence band is induced by the substitutional nitrogen centers, as observedwhen a high concentration of Ti-N species becomes incorporated into the films. In agreement with theexperimental results, when only Ti-NO like species are detected by XPS, no band gap narrowing is obtainedby the calculations that predict the appearance of localized electronic states in the gap.
PB ACS
YR 2010
FD 2010-12-02
LK https://hdl.handle.net/10630/36774
UL https://hdl.handle.net/10630/36774
LA eng
NO P. Romero-Gómez, Said Hamad, J. C. González, A. Barranco, J. P. Espinós, J. Cotrino, and A. R. González-Elipe The Journal of Physical Chemistry C 2010 114 (51), 22546-22557 DOI: 10.1021/jp104634j
NO https://openpolicyfinder.jisc.ac.uk/id/publication/7799
DS RIUMA. Repositorio Institucional de la Universidad de Málaga
RD 19 ene 2026