Nanomechanical Oscillators Could Replace Transistors in Some Computers

Half a century ago a Japanese graduate student came with the idea of creating a revolutionary electrical circuit that would function on the basis of mechanical operations, opposite the electrical ones used today in digital computers. The device was called 'Parametron', but although computers based on these basic building blocks were put together, they were far less efficient than transistor based ones, in terms of power consumption and circuit integration.

Computers today use transistors as basic information processing devices that practically switch between two states represented through zero or non-zero voltage across them. This is also why computers can only be programmed and are able to process information in the binary language. The nanomechanical device Parametron on the other hand can oscillate in only two possible ways, defining two states, meaning it also works only in binary.

Continuing the work started more than 50 years ago, Imran Mahboob and Hiroshi Yamaguchi from the NTT Corporation have developed a new electromechanical oscillator using a bridge-over-gap design. The new Parametron device measures only 260 micrometers in length and it is 84 micrometers wide and 1.35 micrometers thick. The bridge and the gap have been constructed using gallium-arsenide, a widely used semiconductor.

The bridge stands on two clamping points formed by a thin layer of gallium-arsenide sandwiched by gold electrodes. As alternating current matching the natural oscillating frequency of the bridge is being applied to the clamping points, the bridge starts oscillating vertically over the gap. The oscillating motion is determined by the motion of the atoms in the gallium-arsenide bridge in response to the voltage, bending it slightly. By matching the natural oscillating frequency, maximum oscillating amplitude is being achieved.

The oscillating phase of the oscillators can be used to represent the two possible states in binary language, either '0' logic or '1' logic, thus information can be stored and processed through logical circuits made using Parametrons. "This is a highly tunable system, which we expect will make it easily integrable into complex architectures", says Imran.

The new design is neither innovative nor faster than transistor based computers, the main advantage being that it is much more resilient to electromagnetic shocks and more energy efficient, which should be ideal for less powerful computers such as those used in mobile appliances.