Quantum Channels and Conductance Oscillations in Metal/Molecule/Metal Switches

We investigate conductance switching in Pt/stearic acid monolayer/Ti devices by pressure-modulated conductance microscopy. For devices with conductance G$>>$G$_{Q}$ and G$<<$ G$_{Q}$, where G$_{Q}$ is the conductance quantum, localized pressure-induced conductance peaks are observed, indicating formation of nanoscale conductance pathways on the electrodes. For devices with G$\sim $ 1- 2 G$_{Q}$, in addition of conductance peaks, we also observed conductance dips and oscillations in response to localized pressure. These results suggest formation of quantum conductance channels in our devices, and can be satisfactorily modeled by considering interfering electron waves between two partially transmitting electrodes. Moreover, the force dependence of such conductance modulations is fully consistent with this model. Our findings underscore the possible use of these devices as atomic switches.