Past Talks 2017 - Detailseite

Speaker:
Dr. Soon Jung Jung, MPI Stuttgart

Titanium dioxide (TiO₂) is an important material for the solar-based applications due to its stability, band alignment and abundance. However, the large bandgap of TiO₂ yields device efficiencies that are too low to be economically sound. To make TiO₂-based devices competitive, the electronic and chemical properties of TiO₂ need to be clearly understood. Our group investigated the pristine surface using high-resolution STM in atomic scale, which have been ambiguous in the past. (1) Going one step further, we created a novel surface phase consisting of undercoordinated Ti atoms with reduced bandgap and enhanced reactivity. On the other hand, by exposing the anatase surface to excess oxygen at elevated temperatures, we reduced the overall surface reactivity. This reduction was achieved by formation of an oxygen network, acting as a passivating layer on top of the TiO₂ anatase (101) surface. Later, STM-IETS was applied for the first time to obtain chemical identification of adsorbed species on the semiconducting TiO₂ surface. (2) We labeled individual H₂O and OH molecules on the semiconducting surface by detecting their vibrational modes with STM-IETS. Our work will be presented here opens new possibilities for engineering the TiO₂ anatase surface.

[1] C. Dette, M. A. Pérez-Osorio, C. S. Kley, P. Punke, C. E. Patrick, P. Jacobson, F. Giustino, S. J. Jung and K. Kern, Nano Lett. 14 (2014) 6533  [2] C. Dette, M. A. Pérez-Osorio, S. Mangel, F. Giustino, S. J. Jung and K. Kern, J. Phys. Chem. C 121 (2017) 1182.