Enhanced sensitivity from Ag micro-flakes encapsulated Ag-doped ZnO nanorods-based UV photodetector

Abstract

An innovative method of improving zinc oxide (ZnO) nanorods-based ultraviolet (UV) photodetectors was fabricated by photodeposition of silver (Ag) micro-flakes on top of Ag-encapsulated Ag-doped ZnO nanorods. Four concentrations are selected for the doping process (0, 1.7, 3.4, and 5.1 mol%). The Ag-doped ZnO nanorods are synthesized via the hydrothermal method, followed by photodeposition using AgNO3 solution, both of which are low-cost and simple. Ag doping resulted in thinner and shorter ZnO nanorods, improved crystallinity, and reduction of deep-level emissions as corroborated by field emission scanning electron microscopy, X-ray diffraction, and photoluminescence analyses. UV photodetectors fabricated from the samples showed that Ag-doped ZnO nanorods in addition to Ag micro-flakes have improved sensitivity and gain than non-doped ZnO nanorods. Excessive doping results in a higher dark current and reduced sensitivity. A proposed mechanism is given showing the source of photocurrents from Ag micro-flakes and Ag-doped ZnO nanorods.