Nanoscale electronic devices are promising alternatives to silicon-based microelectronics, which is fast approaching its limits. However, most nanoscale switches are still switched on and off with an electric field. Given the present demand for high storage densities and fast data-processing rates, future nanoscale devices will need to be switched using light rather than electrical current.

Lidong Li of the University of Science and Technology Beijing and colleagues have now developed a nanoswitch made from an organic insulator – polystyrene or poly(methylmethacrylate) – sandwiched between indium tin oxide and gold. The device has on/off switching ratios of 106 even at low power densities of 10–5 W/cm2 when illuminated with UV light. Such properties are crucial for optical computing and data-processing applications.

The researchers made their photoswitch by spin coating the organic layer between the other two layers. They then "activated" the device under electric fields to form metal filaments in the organic insulator film. These filaments act as a UV-sensitive material. When exposed to UV light, the current flowing though the devices is inhibited (the "off" state) and when the radiation is removed, current flows through the device again (the "on" state).

The devices are an improvement on previously made photoswitches, which had on/off ratios of less than 103 and needed high powers of more than 10–3 W/cm2 to work.

"These nanophotoswitches could be used in optically controlled logic circuits thanks to their binary switching," Li told "Moreover, since organic field-effect transistors (OFETs) and organic capacitors also employ metal electrode layers and organic insulating layers in their structures, this approach could be extended to applying OFETs in photoswitching or in organic memory devices to fabricate photonic and electric dual-controlled memories."

Li and colleagues would now like to reduce the response time of their nanophotoswitches to UV light.

The work was reported in Applied Physics Letters.