Microstructure and optical properties of electrodeposited Al-doped ZnO nanosheets

This study grew A1-doped ZnO nanosheets on polycrystalline zinc foils using cathodic electrodeposition in an aqueous solution consisting of 0.02 M Zn(NO₃)₂ and 0.001 M Al(NO₃)₃ at 90 °C. The effects of the electrodepositing potential and thermal annealing on the physical properties of the Al-doped ZnO sheets were investigated. This study observed a high quality sheet-like structure of the electrodeposited Al-doped ZnO for the applied potential larger than −1.1 V, and the sheets were interconnected over the area of interest. The X-ray diffraction patterns showed that the intensity of the Bragg reflections of the electrodeposited Al-doped ZnO sheets increases with the electrodepositing potential because a larger applied potential results in the Al-doped ZnO sheets having a larger lateral dimension and thickness. However, the appearance of the Al-doped ZnO sheets becomes coarse and rough after thermal annealing at 400 °C in ambient air for 4 h. The intensity of the Bragg reflections of the Al-doped ZnO sheets was markedly increased through the thermal annealing due to the improvement of the crystalline quality of the annealed Al-doped ZnO sheets. Annealing caused a large decrease in structural defects of the Al-doped ZnO sheets electrodeposited at −1.3 V causing the sheets to exhibit a sharp photoluminescence peak at ∼380 nm.