Adsorption effect of oxygen on ZnO Nanowires (100 nm) leading towards pronounced edge effects and voltage enhancement

Abstract

Here, we report high output piezoelectric voltage generation from oxidized ZnO nanowires (100 nm). Periodic high output voltage peaks were observed during series of oxygen exposure experiments. Gradual rise in piezoelectric potential from oxidized ZnO nanowires is being evidenced for the very first time. Sharp voltage peaks 464 mV, 803 mV, 1.354 V, 1.795 V and 2.44 V are observed for an exposure of oxygen for 1 h, 2 h, 3 h, 4 h and 5 h respectively in a sealed chamber at 50 ppm. It has been observed maximum output value has been saturated after 5 h of O exposure. Enhanced piezoelectric potential appearing at output stages is due to the adsorption of oxygen molecules on long ZnO nanowires, giving rise to ‘Edge Effects’ and consequently reducing reverse leakage current through nanowires and enhancing output voltage. SEM images revealed the surface morphology ZnO nanowires, diameter range was found around 100 nm. XRD pattern verified vertical growth orientation of ZnO nanowires on ITO (indium Tin oxide) coated PET (poly ethylene terephthalate) substrates. Minute external force ∼50 nN is used to produce piezoelectric potential within nanowires.