What you see it is not what it is! Chemical and morphological changes in the tip are frequent during an experimental STM session. We have shown the effect of different tip apexes on the appearance of atomic features of STM images by relating experimental STM images with DFT calculations. The work, which focuses on the particular case of the TiO2(110)-(1×1) surface, also identifies typical point-defects of this surface, as oxygen vacancies and hydroxyl groups.
TiO2(110)-(1×1) surface seen with a “contaminated” tip
The left panel shows an experimental STM image of the TiO2(110)-(1×1) surface. As we show by DFT calculations, in this case the W tip is terminated in a single O atom adsorbed replacing the W-apex. The right panel shows a) the STM experimental image of the same surface. A double tip formed by two O atoms adsorbed at the apex is the responsible of the image, as inferred from the theoretical calculations (image b). The presence of defects has also been simulated theoretically (images c and d).
These results have been published on “Nanotechnology”.