Dresden 2014 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 16: Electronic Structure and Spin-Orbit Interaction II

O 16.6: Vortrag

Montag, 31. März 2014, 17:15–17:30, GER 38

The origin of TiO2 shallow gap states evidenced from resonant photoelectron spectroscopy (RPES) and AFM on anatase single crystal (101) surface, nanocrystalline anatase films and ALD titania ante and post annealing — •Philip Reckers1, Mariel Dimamay1, Sara Trost2, Thomas Riedl2, Thomas Mayer1, and Wolfram Jaegermann11Technical University of Darmstadt, Surface Science, Germany — 2Wuppertal University, Electronic Devices, Germany

Transparent, conductive and catalytic active TiO2 with all its polymorphs is of high interest as it is used e.g. for water splitting, in DSSC and OSC. Gap states in TiO2 play a crucial role as they influence e.g. charge transport and act as recombination centers. We investigated TiO2 samples with respect to gap states by the use of resonant photoelectron spectroscopy. We detected two different band gap states. Deep gap states (DGS), that are attributed to oxygen defects are found around 1.3 eV and shallow gap states (SGS) are occupied from the Fermi level to about 0.35 eV binding energy. On a single crystal (SC) anatase (101) surface only SGS were detected. DGS and SGS states are observed on sintered nanocrystals (NC). Together with images from AFM we were able to ascribe the SGS to under coordinated Ti sites. The measured DOS fits well to the calculated DOS tailing into the energy gap inherent to NC as 1D line defects of under coordinated Ti sites form at (101) intersections[1]. Similar defects are located at edges of terraces on SC surfaces that form along the (101) direction. [1]F.Nunzi, F.De Angelis, E.Environ. Sci.,2013,6,4,1221-1229

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