Berlin 2005 – wissenschaftliches Programm

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DF: Dielektrische Festkörper

DF 4: Poster

DF 4.2: Poster

Samstag, 5. März 2005, 08:30–16:30, Poster TU C

Photoconductivity measurements at the surface of titanium dioxide — •Roger Amade¹, Sylvio Indris¹, Paul Heitjans¹, Andreas Haeger², Mina Finger², and Diethardt Hesse² — ¹Institut für Physikalische Chemie und Elektrochemie, Universität Hannover, 30167 Hannover, Germany. — ²Institut für Technische Chemie, Universität Hannover, 30167 Hannover, Germany.

The electrical photoconductivity σ_ph and conductivity σ at the surface of a TiO₂ single crystal (rutile) was studied in a range of temperatures between 300 K and 573 K and under different ambient gases (oxygen and nitrogen) by means of impedance spectroscopy. The long times required (many hours) to reach steady state photoconductivity suggests the presence of slowly emptying traps. A single exponential could be used to fit the rise curves. In the dark, surface adsorbed oxygen gas acts as a recombination center increasing the decay rate of the photoconductivity. At about 473 K a maximum is observed in the equilibrium photoconductivity and a minimum in the rate constants of the rise and decay.