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HL: Halbleiterphysik

HL 16: Störstellen/Grenz- und Oberfl
ächen I

HL 16.6: Vortrag

Dienstag, 28. März 2000, 10:45–11:00, H17

Photovoltage phenomena in sintered porous layers of TiO₂ — •Volodimyr Duzhko¹, Victor Timoshenko², and Thomas Dittrich¹ — ¹Technical University Munich, Physik Department E16, D-85748 Garching, Germany — ²M. V. Lomonossov Moscow State University, Faculty of Physics, 119899 Moscow, Russia

Sintered porous layers of TiO₂ nanocrystals (with different

mean diameter between 5 and 60 nm) were investigated by methods

of pulsed and spectral photovoltage in the spctral range from

1 to 4 eV. The sign of the photovoltage was found to be positive.

The photovoltage amplitude depends on the mean diameter of the

nanocrystals and on the traps induced by adsorbed molecules. The

photovoltage amplitude increases irreversibly by more than 2

orders of magnitude after short vauumation of freshly prepared

porous TiO₂ layers. This effect correlates with an increase

of the rise and decay times of the photovoltage transients.

Further, the photovoltage amplitude increases with increasing

diameter of the TiO₂ nanocrystals. The mechanism of the

formation of the photovoltage signal in in porous TiO₂ is

discussed on the basis of excess carrier diffusion and trapping

leading to optical doping of TiO₂ nanocrystals.