Search

We study room temperature optics and electronic structures of ZnO:Cu films as a function of Cu concentration using a combination of spectroscopic ellipsometry, photoluminescence, and ultraviolet-visible absorption spectroscopy. Mid-gap optical states, interband transitions, and excitons are observed and distinguishable. We argue that the mid-gap states are originated from interactions of Cu and oxygen vacancy (Vo). They are located below conduction band (Zn4s) and above valence band (O2p) promoting strong green emission and narrowing optical band gap. Excitonic states are screened and its intensities decrease upon Cu doping. Our results show the importance of Cu and Vo driving the electronic structures and optical transitions in ZnO:Cu films. [ABSTRACT FROM AUTHOR]

The use of zinc oxide-based photocatalysts has been extensively conducted to breakdown harmful pollutants in wastewater treatment. Recently, ZnO doped non-metal can improve photocatalytic activity by reducing charge carrier recombination. Here, S-doped ZnO thin films, with a sulfur dopant of 1 and 5% molar, were synthesized by a seed-mediated hydrothermal process. The enhancement in crystal structure and morphology were noted with the presence of sulfur in the ZnO system. The photocatalytic test shows that the presence of sulfur enhances Rhodamine B (RhB) degradation efficiency up to 92% with reaction rates of 1.67 × 10−2 min−1 under visible light. The S-doped ZnO thin film is potentially applied as a stable photocatalyst for wastewater purification, with a noted photocatalytic efficiency of 75% after repeated use. • The sulfur-doped ZnO thin films have a good performance as a photocatalyst. • The photocatalyst process for rhodamine B can take place under visible light. • The sulfur dopant promotes an increase in surface density and crystallinity. • The recyclability test shows the sulfur-doped ZnO can be used repeatedly. [ABSTRACT FROM AUTHOR]