Patterned Assembly of Inorganic Semiconducting Nanowires Using Lithography-Free Technique

Patterned assembly of inorganic nanowires (NWs) at desired locations offers the opportunity to realize large-area high-performance flexible electronics. Transfer and contact printing methods are some of the viable methods to achieve this. However, some of the fabrication steps in these methods rely on lithography, which are inherently wasteful, and therefore, the approach is not an ideal solution for large-area electronics. Here, we show a lithography-free patterning technique in which NWs are selectively removed from a uniformly contact printed electronic layer. The NWs are removed using an elastomeric stamp. The removal efficiency is improved by evaporating a thin layer of water onto its patterned face, which greatly enhances the stamp-NW adhesion via the capillary action. The scanning electron microscope (SEM) analyses of the NW layer showed a good pattern fidelity, fair retention of the initial NW density, and optimal contrast between positive and negative areas of the pattern. The efficacy of the presented technique for printed electronics is demonstrated by fabricating all-printed ZnO NW-based photodetectors (PDs) on a flexible substrate. Using the as-prepared patterned NWs, a $3\times4$ array of PD devices is fabricated. The PDs show good responsivity (1.3 $\times 10^{6}$ A/W) and specific detectivity ( $6.95\times 10^{16}$ Jones) in the UV range. These devices show that the presented selective removal approach could be an attractive route for future lithography-free printed electronics.