The effect of the Cu dopant on the ultraviolet photodetector based on ZnO nanorods

In this work, a (ZnO)/(Cu-doped ZnO) core/shell nanorods array was fabricated by a two-step ZnO hydrothermal synthesis followed by encapsulation via a dip-coating process. The effects of the Cu dopant concentration on the structural, electrical and optical properties of the nanorods were studied. The SEM images showed that the encapsulation increased the nanorods average diameter from ~40 to ~60 nm. All ZnO core/shell nanorods showed a hexagonal wurtzite structure with no trace of a Cu oxide phase. A peak shift was observed in the XRD pattern, indicating the better Cu+ substitution into the Zn sites. The I–V measurements also showed that Cu doping up to 4.5 at.% decreased the samples resistance, which could be attributed to the +1 valance state of the Cu ions. It was also found that Cu doping increased the UV photoresponsivity of the photodetectors made by Cu:ZnO.