ACS Nano http://doi.org/hrv (2012)

Single-electron transistors (SETs) — devices in which the motion of a single charge can be accurately controlled — have potential in nanoelectronics due to their low power consumption and miniaturization capabilities. Bottom-up approaches can deliver SETs with features that are less than 10 nm in size. However, fine control over the fabrication process is needed to form stable functional devices. Yutaka Majima and colleagues at the Tokyo Institute of Technology, the University of Tsukuba, Kyoto University and Sunchon National University have now used chemical assembly to create a two-gate SET capable of performing two-input logic-gate operations such as exclusive OR (XOR) or not exclusive OR (XNOR).

The researchers produced a 10 nm gap between two dithiol-coated gold electrodes (the source and the drain) and covalently placed a gold nanoparticle in the nanogap to function as a single Coulomb island. Tunnelling from the source to the drain is controlled by the presence of two gold gates perpendicular to the direction of the flowing charges. Because both gates couple with the island in an almost identical way, modulating their voltage generates the two-input logic-gate device.

During operation, the device exhibits ideal Coulombic oscillations and remains stable over repeated cycles with no hysteresis and a high on/off current ratio at 9 K. Further miniaturization will, however, be required before the device can operate at room temperature.