Squitches...

The metal–molecule–metal switching gap lowers the surface adhesion forces and allows nanoscale force control through compression of the molecular layer, while enabling formation of a few nanometer-thick gaps for sub-1 V operation. Courtesy of ACS Nano

Topics: Electrical Engineering, Nanotechnology, NEMS, Quantum Mechanics, Semiconductor Technology

The transistor – a switching element that defined technological progress through the 20th century – may be reaching its limits as demands for smaller devices continue. One alternative is the nanoelectromechanical (NEM) switch, but so far these have fallen short of the performance criteria required. Now an improved NEM switch based on tunnelling has demonstrated how these switches may yet be a viable contender to succeed the conventional transistor in low-power devices.

“To be competitive, the NEM switch operation must be made more energy efficient and reliable,” says Farnaz Niroui, a researcher at the Organic and Nanostructured Electronics Laboratory at the Massachusetts Institute of Technology in the US. “Our proposed tunnelling switching mechanism based on molecular thin films enables us to achieve drastic miniaturization of the devices to lower the operating voltages and provide nanoscale force control for more repeatable and reliable performance.”

Traditional electromechanical switches complete a circuit when the two electrodes are in contact, and break it – ‘turn off’ – when they are not. Scaling these elements down to the nanoscale offers a switching mechanism that may outperform conventional transistors in terms of the on/off ratio and low leakage current that can be achieved. However, operating reliably at low voltages requires control over the nanoscale distance between the electrodes that is tricky in itself, and further complicated by adhesive ‘stiction’ forces that cause the device to fail.

Here, the tunnelling approach appears to provide the answer for Niroui and her team at MIT led by Vladimir Bulović, Jeffrey Lang and Timothy Swager. They sandwich a self-assembled organic molecular film – poly(ethylene glycol)-dithiol (PEG-dithiol) – between the electrodes and modulate the tunnelling current through the film as it compresses and recovers.

Nanotechweb.org:
Low-voltage electromechanical 'squitches' make their debut, Anna Demming