Configuration specific desorption by scanning tunneling microscope in organic-semiconductor hybrid systems

Abstract

Configuration-specific desorption of ethylene on a Ge(100) surface has been controlled at the nanoscale, induced using a scanning tunneling microscope (STM) tip at room temperature. Ethylene was found to adsorb in two distinct bonding geometries: (i) on top of a single Ge-Ge dimer (OT) and (ii) in a paired end-bridge between two neighboring Ge dimers within the same dimer row (PEB). Only OT configuration desorbs effectively at the sample bias voltages between -2.9 V and -3.1 V, tunneling current of 50 pA, and room temperature. The desorption yield for each configuration was measured as a function of sample bias voltages, where the voltage dependences of desorption yields show rapid increases between -2.9 V and -3.4 V for OT desorption, whereas between -3.2 V and -3.7 V, the PEB desorption increases rapidly. We have found that the applied sample bias voltages induce sigma(Ge-C) hole-resonant inelastic tunneling, resulting in the dissociation of the Ge-C bonds. This selective, STM-induced desorption makes it possible to apply local control of surface reactions and to develop nanoscale lithography for molecular electronic devices.