Nonlinear current-voltage curves of gold quantum point contacts

Nonlinear current-voltage (I-V) curves of gold quantum point contacts (QPC) were investigated using a transmission electron microscope–scanning tunneling microscope system. The I-V curves were measured by sweeping the bias voltage from 0 to 0.3 V at room temperature under ultrahigh vacuum. The results revealed that when the QPC formed a short nanowire, a nonlinear I-V curve was observed, while a long nanowire produced a linear I-V curve. The nonlinear I-V curves were found to be caused by a nanowire thickening that occurred during increases of the bias voltage. This thickening resulted from a shortened distance between electrodes.