Ultraviolet mem-sensors: flexible anisotropic composites featuring giant photocurrent enhancement

Abstract

By using two separate components, mem-sensing devices can be fabricated combining the sensitivity of a transducer with non-volatile memory. Here, we discuss how a mem-sensor can be fabricated using a single material with built-in sensing andmemory capabilities, based on ZnO microwires (MWs) embedded in a photocurable resin and processed from liquid by vertically aligning the MWs across the polymeric matrix using dielectrophoresis. This results in an ultraviolet (UV) photodetector, a device that is widely applied in fields such as telecommunication, health, and defense, and has so far implemented using bulk inorganic semiconductors. However, inorganic detectors suffer from very high production costs, brittleness, huge equipment requirements, and low responsivity. Here, we propose for the first time aneasy processable, reproducible, and low-cost hybrid UV mem-sensor. Composites with aligned ZnO MWs produce giant photocurrentscompared to the same composites with randomly distributed MWs. In particular, we efficiently exploit a mem-response where the photocurrent carries memory of the last electronic state experienced by the device when under testing. Furthermore, we demonstrate the non-equivalence of different wave profiles used during thedielectrophoresis: a pulsed wave is able to induce order in both the axis and the orientation of the MWs, whereas a sine wave only affects the orientation.