On the alignment of ZnO nanowires by Langmuir - Blodgett technique for sensing application

Nanowires are of interest for gas sensing application due to their one dimensional nature and size approaching quantum confinement limit, best studied in single nanowire devices. The reaction between gases and the semiconductor surface is better exploited when one, or few nanowires are involved. Yet, the widespread use of single nanowire devices is prevented by the need of expensive techniques to fabricate contacts. Here we applied the Langmuir-Blodgett technique to align ZnO nanowires between electrodes being two microns apart in a configuration that possess both the quality of single nanowire devices and the advantages of multiple nanowires. We achieved alignment without using lithography, so the procedure is inexpensive and scalable. As a proof of concept, we demonstrated that the obtained chips are suitable for sensing of NO2, either at 200 degrees C or at room temperature with light activation. We discussed the obtained sensing parameters as a function of supra and sub-bandgap photoactivation.