A large array of densely packed silicon nanowires can be used as a chemical sensor
Nanowires can be used for the detection of chemicals as well as biomolecular recognition events such as DNA hybridization. However, methods currently used to make the nanowire sensors are time consuming and involve photolithographic processing of semiconductors. Furthermore, the electrical properties of nanowires produced by such ‘top-down’ methods are non-uniform, leading to inconsistent device performance.
Now, A. Alec Talin and colleagues1 of Sandia National Laboratories in the USA have demonstrated the versatility of nanoimprint lithography for making chemical sensors based on silicon nanowire arrays. A silicon-on-insulator wafer was thermally imprinted using a silicon mold with 100-nm-wide parallel lines spaced 100 nm apart. Pattern transfer was achieved by ion etching to give large-area, highly uniform arrays of Si nanowires, each with a width of approximately 75 nm.
The array was built into a field-effect transistor structure by depositing aluminium electrodes, and was used to detect chemicals such as ammonia, nitrobenzene and phenol. The output from these sensors depends upon the polarity of the analytes and is proportional to their concentration. Nanoimprinting of Si nanowires may offer a simpler route than the use of carbon nanotubes for making chemical and biological sensors.
Talin, A. A. Hunter, L. L. Léonard, F. & Rokad, B. Appl. Phys. Lett. (2006). 10.1063/1.2358214