STM beyond vacuum tunneling : scanning tunneling hydrogen microscopy as a route to ultra-high resolution

摘要

Direct imaging is a fast and reliable method for the characterization of surfaces. Whenit comes to small surface structures in the size of the features e.g. in todays computerprocessors, classical optical imaging methods fail in resolving these structures. Withthe invention of the scanning tunnelling microscope (STM) for the first time it becamepossible to image the structure of surfaces with atomic precision. However, the STM failsin resolving complex chemical structures like e.g. organic molecules. The lack of chemicalsensitivity in STM images can be overcome by the condensation of molecular hydrogenor deuterium in the STM junction. Images recorded in the so-called scanning tunnellinghydrogen microscopy (STHM) closely resemble the chemical structure of different organicmolecules. However, the mechanism behind the contrast formation has not been addressedso far. Here we show that the origin of the STHM contrast is a single hydrogen (H2) ordeuterium (D2) molecule located directly below the tip apex that acts as a combinedsensor and signal transducer....