Controlled growth of CuO nanowires on Cu grid via thermal oxidation process with enhanced field electron emission properties

We report improved field electron emission (FEE) properties of copper oxide (CuO) nanowires (NWs) emitter by adjusting their aspect ratio, density at emitting edges, and strength of the NWs. We have grown CuO NWs by controlled morphology on copper grid via two-stage annealing process. In the first step of annealing performed at 200 °C for 2 h, creation of nucleation sites for growth of the NWs is achieved. Subsequently, a second annealing phase at 400 °C for another 2 h leads to the emergence of vertically aligned NWs. These structures are notably dense at their base, with an approximate width of 23 nm and lengths reaching several micrometers, as indicated by SEM analysis. During the FEE, the field screening effect is noticeably minimized as the NWs are quite long and well separated at apex. The turn-on field (E_on) is observed to be 4.72 V/μm (10 μA/cm²). A maximum emission current density (J) of ~ 14.11 mA/cm² has been drawn from the emitter, at an applied field ~ 11.12 V/μm. The enhancement in the emission current density after stability is because of desorption of the gases and the presence of clean emitting sites on the emitter surface. The emission at preset value ~ 15 μA is observed to be very stable over more than 3 h. These results are the implications of unceasing quest for the development, production, and improvement of integrated field emitters based on self-supportive 1D nanostructures.