Room-temperature compressive transfer printing of nanowires for nanoelectronic devices

Recently, there has been a growing interest in the controlled alignment and robust bonding process of nanowires (NWs) on nanoelectronic devices. In this paper, we developed an innovative process for the fabrication of NW-based devices by room-temperature and low-pressure compressive transfer printing of NWs, in which NWs could be simultaneously aligned and bonded onto the metal electrodes. In this process, chemically synthesized NWs were first transferred and aligned on an intermediate substrate by contact printing and then finally printed onto a target substrate with mechanically soft Au electrodes, which enables the embedding of aligned NWs under low-pressure (5 bar) and room-temperature condition. The resulting contact between NW and Au electrodes exhibits Schottky behavior and high mechanical bonding strength (>567 MPa). The electrical characteristics could be converted from Schottky to Ohmic contact through thermal annealing treatment at 250 °C for 5 min due to Cr diffusion and direct Cr-ZnO contact formation. The applications of the fabricated devices as ultraviolet (UV) and gas sensors were successfully demonstrated. Furthermore, NW-based electronic devices were fabricated on a flexible substrate by using this process and showed mechanical and electrical robustness under mechanical bending conditions.