Tunable nanoporosity in Sr-doped ZnO thin films by thermal annealing treatment and its effect on photocatalytic activity

In this work, Sr-doped ZnO thin films are prepared by sol-gel technique and annealed at various temperatures. The crystal structure of the samples is analyzed by X-ray diffraction (XRD); surface and sectional morphologies are observed by scanning electron microscopy (SEM). The XRD patterns show that all the films crystallize in a wurtzite phase and have a preferential orientation along the c-axis. The SEM morphology images reveal that all the Sr-doped ZnO thin films have a porous structure and the pore size changes with the rise of annealing temperature. When the annealing temperature is 500 degrees C, the porosity in the films is highest. The photocatalytic tests of these samples show that all th e porous ZnO thin films exhibit better photocatalytic performance than pure ZnO thin films; and the sample annealed at 500 degrees C exhibits the highest photocatalytic activity, which should be attributed to the higher porosity and stronger light absorption.