Nanowire networks for macroelectronic devices

Zinc oxide nanowires are promising materials for inexpensive large-area electronics

Credit: © 2009 AIP

Zinc oxide (ZnO) is a wide-bandgap semiconductor with a large exciton binding energy, and nanowires made of ZnO are promising for applications such as field-effect transistors and transparent electrodes for solar cells. However, integrating ZnO nanowires with macroscopic device structures remains a barrier to these applications. Now, Husnu Emrah Unalan and colleagues at Cambridge University and Rutgers University have shown that highly transparent ZnO-nanowire networks can be used as the active material in thin-film transistors and complementary inverter devices.

The devices were fabricated by a three step process: growth of a dense 'lawn' of ZnO nanowires on gold-catalysed silicon substrates by hydrothermal reduction of ZnO powder at 950 °C; transfer of the nanowire networks to SiO₂/Si substrates by contact printing; and photolithography to form device structures with niobium source and drain contacts.

The nanowire networks had effective electron mobilities of ∼25 cm² Vs⁻¹, compared with just ∼1 cm² Vs⁻¹ for devices made of amorphous silicon or organic semiconductors. Networks of ZnO nanowires could find applications as materials for the large-scale fabrication of inexpensive devices on flexible substrates.