CONDUCTANCE QUANTIZATION IN NANOWIRES FORMED BETWEEN MICRO AND MACROSCOPIC METALLIC ELECTRODES

In this work we present experimental results concerning conductance qu antization at room temperature in metallic nanowires. The experiments are performed both at ambient presure and in ultrahigh vacuum using sc anning tunneling microscopy (STM)-like devices. Both microscopic and m acroscopic electrodes are used. The obtained results are independent o f the electrode size, indicating that nanowires form at the last stage s of the contact-breakage process, independently of the initial size a nd shape of the contact. In addition, we study (a) the stability of th e nanowires, finding their lifetimes remarkably long, an the order of minutes; (b) the I-V curves for different quantum channels; (c) nanowi res formed and visualized using a STM inside a scanning electron micro scope (SEM); (d) the statistical behavior of the conductance, sampling tens of thousands of consecutive conductance experiments, showing cle ar quantized peaks up to five quanta of conductance; and (e) the lengt h of the conductance plateaus, that might indicate the chaotic behavio r of the quantum states formed at the nanowire. The statistical study of the conductance plateau lengths shows a broad Wigner-like distribut ion with an average value of 0.13 nm for the first quantum channel. Th is is at variance with a constant length, predicted and experimentally observed, in the plateaus between force jumps.