Direct observation of nanoscale switching centers in metal/molecule/metal structures

Conductance switching in metal/molecule/metal structures has attracted tremendous and broad interest. Understanding the switching mechanism, which remained controversial to date, will be vital for engineering nanoscale switches crucial for memory and logic applications. Here we describe a new switching mechanism revealed by a novel scanned-probe technique that images the mechano-electrical response of a Pt/ stearic acid/Ti structure switch device. In each image a single switching center, characterized by a nanoscale conductance peak, appeared or disappeared when the device was switched on or off. Our results strongly indicate that the formation and dissolution of individual nanoscale filaments through the molecular layer give rise to conductance switching in our molecular structures with unusually high on/off ratios (similar to10(5)).