Enhancing photoresponse time of low cost Pd/ZnO nanorods prepared by thermal evaporation techniques for UV detection

Abstract

High quality undoped ZnO nanorods have been synthesized at 850 °C by vapor–solid (VS) technique without a catalyst through a low cost process on silicon substrates. Then, ZnO nanorods have been characterized by using scanning electron microscopy (SEM), X-ray diffractometer (XRD), and photoluminescence (PL) spectroscopy. Metal–semiconductor–metal (MSM) photodetectors with palladium (Pd) as contact electrodes have been successfully constructed for ultraviolet (UV) detection. Under dark and UV illumination, the load resistance of the Pd/ZnO junction was found to be 80.4 kΩ, and 23.5 kΩ referring to the maximum allowed bias voltage; the barrier height was estimated to be about 0.8 eV, and 0.76 eV, at 5 V applied bias voltage, respectively. It was found that the maximum responsivity of the Pd/ZnO MSM photodetector was 0.106 A/W at 300 nm which corresponds to a quantum efficiency of 43.8% at 5 V applied bias voltage. The transient photoresponse of the fabricated device is reported under different applied biases at 1 V, 3 V, and 5 V.