Transition voltage spectroscopy in vacuum break junction: Possible role of surface states
Theoretische Chemie, Physikalisch-Chemisches Institut, Universität Heidelberg - Im Neuenheimer Feld 229, D-69120 Heidelberg, Germany, EU
Accepted: 11 March 2012
The recently proposed transition voltage (Vt) spectroscopy (TVS) is becoming an increasingly popular tool to analyze electric transport through molecular devices. Very recently, to get additional insight into TVS, the distance (d) dependence Vt(d) in vacuum break junctions has been investigated experimentally. In this letter, we point out inconsistencies of the initial theoretical interpretation, based on approximate Wenzel-Krammers-Brillouin (WKB)-type results within the standard vacuum tunneling barrier model. We demonstrate that even the exact treatment of this model fails to explain the experimental Vt(d)-dependence, but the agreement with experiment is substantially improved by accounting for electron states (or resonances) at electrodes' surface. These findings suggest that surface states may also play a significant role in molecular devices with sharp electrodes and calls for further investigations.
PACS: 73.63.Rt – Nanoscale contacts / 85.35.Gv – Single electron devices / 85.65.+h – Molecular electronic devices
© EPLA, 2012