Thermal Annealing Influences on the Photoresponse of Zinc Oxide Nanoparticle Films

In this work, the effects of annealing temperature on the photoresponse of zinc oxide (ZnO) nanoparticle (NP) films are reported. The photoresponse mechanism of ZnO NP films at various annealing temperatures is investigated using a blue-violet laser diode at a wavelength of 405 nm. The electrical sensitivity measurements of annealed film at 500 degrees C shows an increasing photocurrent from 0.5 mu A to 4 mu A when it is irradiated by a 405-nm laser with an output power of 50 mW. Oxygen vacancies of film surfaces constructed by the annealing process have a significant role in increasing the photocurrent. The structure and optical properties of fabricated films are studied using x-ray diffraction pattern, field emission scanning electron microscopy, Fourier transformation infrared spectroscopy, UV-visible absorption spectrometry and photoluminescence spectroscopy. Also, the photoconductivity behavior of films is investigated using a two-point probe technique. The results show that by increasing annealing temperature, the electrical conductivity of the films has remarkably improved. The properties that are explored in the annealed ZnO NP films make this material an excellent alternative for fabricating photodetectors.