Aug 29, 2012
All nanowire networks give photodetectors a twist
Nanowire networks offer a route to making flexible and transparent electronics, photodetectors in particular, and can be fabricated by depositing material from solution at room temperature and over large areas, if required. In a recent study, researchers from Middle East Technical University in Ankara, Turkey, have come up with a series of production steps to include nanowire contacts as well as active elements to create a fully flexible device with very fast response characteristics.
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.
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.
About the author
The work was performed in the Department of Metallurgical and Materials Engineering at Middle East Technical University by researchers from the Nanomaterials and Devices Group led by Prof. H Emrah Unalan. The group is focused on the synthesis and solution processing of semiconducting and metallic nanowires and exploiting their novel properties in flexible devices. This particular work was supported by The Scientific and Technological Research Council of Turkey (TUBITAK) and Turkish Academy of Sciences (TUBA).