Modification of HF-treated silicon (100) surfaces by scanning tunneling microscopy in air under imaging conditions

The modification of HF-etched silicon (100) surface with a scanning tunneling microscope (STM) operated in air is studied for the first time in samples subjected to the standard HF etching without the follow-up rinsing in H2O. The modifications are produced in air under normal STM imaging conditions (Vt=-1.4 V and It=2 nA). The simultaneous acquisition of topographical, current image tunneling spectroscopy and local barrier-height images clearly shows that the nature of the modification is not only topographical but also chemical. The features produced with a resolution better than 25 nm are attributed to a tip-induced oxidation enhanced by the presence of fluorine on the surface.