White Light Photodetection Using Vertical ZnO/CuO Heterostructure Nanowires

Vertically aligned axial ZnO/CuO heterostructure (HS) nanowires (NWs) were grown using sputtering integrated with glancing angle deposition (GLAD) technique. Field emission scanning electron microscopy (FESEM) images confirmed the growth of vertically aligned axial ZnO/CuO HS NWs. Furthermore, post-annealing treatment at varying temperatures like 300°C, 400°C and 500°C was performed on the samples in order to study the effect of temperature on the structural, optical and electrical characteristics of the samples. On fabricating photodetectors, the 400°C annealed axial ZnO/CuO HS NWs sample showed the best performance in terms of faster photoresponse (response time (${\mathrm {t}}_{\text{rise}}=0.21 \mathrm{~ms}$ and $t_{\text{fall}}=0.20 \mathrm{~ms}$ at +5V under white light illumination)) due to minimum defect density, enhancement in crystallinity (as established from X-ray diffraction and photoluminescence analyses respectively) in addition to efficiently separated photocarrier generation. This signified that post-treatment on the axial ZnO/CuO HS NWs have attractive scope for photodetector application.