AVS 62nd International Symposium & Exhibition
    Surface Science Tuesday Sessions
       Session SS+EN-TuA

Paper SS+EN-TuA2
STM Tip-Induced Desorption of TMAA from TiO2(110): Model Study of a Photocatalytic Process

Tuesday, October 20, 2015, 2:40 pm, Room 112

Session: Photocatalysis, Photochemistry, and Chirality at Surfaces
Presenter: Denis Potapenko, Columbia University
Authors: D.V. Potapenko, Columbia University
R.M. Osgood, Jr., Columbia University
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Titanium oxide is a versatile photocatalytic material with numerous applications in the areas related to utilization of solar energy. Scanning Tunneling Microscopy (STM) allows explorations on the single molecule basis thus providing important insight into the physical phenomena involved in photocatalysis. Our experiments examine the tip-induced chemistry of trimethyl acetic acid (TMAA) molecules adsorbed on TiO2 rutile(110) surface;this systems was chosen as a model for light-driven catalysis since it is easily imaged with STM and since this system has been the subject of many earlier studies of photo and thermal chemistry. In present work we study the electrical hole-driven desorption of TMAA molecules, initiated by the charges, injected from the STM tip. Different values of the flux and the energy of the excitation charges were achieved by the simultaneous control of the setpoint current and the bias voltage of the STM tunneling junction. The dynamics of the tip-induced desorption of TMAA was compared with the photo-induced dynamics of the same reaction. In the latter experiments the monochromated light from a UV lamp was used as the source of excitation. We show that there is a threshold energy for a hot hole below the edge of the TiO2 valence band that is required for TMAA photo-desorption.