Enhanced photodetector performance in gold nanoparticle decorated ZnO microrods

Herein, we present a facile synthesis of ZnO microrods and surface decoration with gold nanoparticles using a low-cost deposition apparatus. The ZnO microrods were fabricated via a single-step solid-state reaction, and the gold nanoparticles were synthesized on the surface of the microrods by the deposition of gold thin films and sequential heat treatment. The size of the gold nanoparticles was controlled by varying the thickness of the gold thin films and the annealing temperature. The intensity of green emission in the photoluminescence spectra decreased with increasing gold nanoparticle size. A surface plasmon resonance peak originating from the gold nanoparticles appeared at ~570 nm in the absorption spectra, and the peak redshifted as the nanoparticle size increased. The ultraviolet (UV) on–off current ratio and response speed of single ZnO microrod photodetectors significantly increased after surface decoration by gold nanoparticles. However, the performance of the photodetector degraded as the size of the gold nanoparticles increased owing to the absorption of incident UV light. The enhanced photodetector performance of the surface-modified ZnO microrods is explained by the transfer of energetic electrons excited by surface plasmon resonance from the defect level to the conduction band of the ZnO microrods.