Oxidation kinetics of nitrogen doped TiO(2-δ) thin films.
The oxidation kinetics of nitrogen doped, oxygen deficient titanium dioxide thin films has been studied in atmospheres of pure oxygen or nitrogen at 500 °C, 550 °C, and 600 °C, respectively, by means of in situ optical spectroscopy. The thin films show high electronic absorbance in the visible and NIR region, accompanied by a red shift of the absorption edge of about 0.4 eV, e.g., from about 2.9 to 2.5 eV at 600 °C. The time dependent decrease of absorbance due to oxidation is found to follow a parabolic rate law. An activation energy of about 1.96 eV can be obtained from the temperature dependence of the parabolic oxidation rate constant. In the framework of a microscopic oxidation model, this energy barrier is attributed to the diffusion of titanium interstitials in the re-oxidized part of the thin films as a rate-determining process. In addition, an attempt is made to evaluate the kinetics of nitrogen release from the time dependent blue shift of the absorption edge during re-oxidation.
Institut für Physikalische und Theoretische Chemie, Technische Universität Braunschweig, Hans-Sommer-Str. 10, D-38106 Braunschweig, Germany. j.shi@tu-braunschweig.de
Jianmin
J
Shi
Doh-Kwon
DK
Lee
Han-Ill
HI
Yoo
Jürgen
J
Janek
Klaus-Dieter
KD
Becker