The group uses a high-temperature vapour transport method to synthesize germanium nanowires, which can then be taken into solution and deposited onto various substrates in the form of a network with controllable density. This forms the active semiconducting element of the photodetectors.

Nanowire networks are used again for the contacts to create devices that are fully flexible, but this time the material is silver. Spray-coated silver nanowires, synthesized by the same group through a polyol process, are used for this purpose. In the work, single-walled carbon nanotube networks are also investigated as contacts.

Metal-semiconductor-metal photodetectors were fabricated both on glass and flexible PET substrates for subsequent analysis by the team. Junctions between germanium nanowires allow barrier-dominated conduction in the network and are found to be responsible for the fast response and recovery time of the device. A recovery time of less than 10 ms is achieved.

Future work

The scientists operated their device under solar-simulated light and the next steps include investigating the near-infrared response of the germanium nanowire networks. The group also plans to explore the use of germanium nanowire networks as the active material in thin-film transistors.

More details can be found in the journal Nanotechnology.