The XPS and AES results display the great interest of physical UHV treatment to eliminate the contamination layer and stimulate the incorporation and oxidation of indium into the ZnO matrix. Both samples are submitted in the same conditions to cleaning treatment (argon ion etching followed by thermal annealing in Ultra High Vacuum UHV). The growth process of films on the Si substrate is achieved by ultrasonic spray pyrolysis. We show the importance of powerful and complementary analysis techniques XPS (X-rays Photoelectron Spectroscopy), AES (Auger Electron Spectroscopy), and UPS (UV Photoelectron Spectroscopy) associated with PL (Photoluminescence) to investigate the chemical composition, optical emission, and electronic structure of undoped ZnO (UZO) and In-doped ZnO (IZO) thin films at the contaminated and clean. These factors combined with the increased grain size, the decreased microstrain, and the low ionization potential (6.80 eV) are suggested to be responsible for improving the photocatalytic efficiency in CoZnO#1. However, bandgap narrowing, Fermi level lowering, a redshift with considerable fluctuations in excitonic emission, and a perfect quenching of visible emission (400-640 nm) were observed only with Co(1at%)-doping. Besides, PL spectra of both Co-ZnO films reveal the participation of band-to-band transition in UV emissions and a useful intense red-emission at 685 nm, due to the Co incorporation. UV-vis, PL, and UPS were adopted to study the influence of Co substituting Zn on the optoelectronic properties of ZnO, including the valence band electronic structure, bandgap, mid-bandgap states, excitonic emission, work function, Fermi level, and ionization potential. XRD, XPS, and AES, as sensitive and complementary techniques, substantiate the successful Co incorporation as a substitute for Zn, especially with low content (1at%). AFM-images reveal a high tendency for crystalline grains of both CoZnO surfaces to aggregate to form large ones, increasing the mean roughness. were used to coat the inner walls of transparent tubes for MB photocatalytic degradation.
In this regard, pure and Co (1at%, 3at%)-doped ZnO (Co-ZnO) thin films were synthesized using the ultrasonic spray pyrolysis technique. In this study, the effect of low-content cobalt doping on the chemical, structural, morphological, optoelectronic, and photocatalytic properties of ZnO was systematically investigated via XRD, XPS, AES, UPS, PL, UV-vis, and AFM techniques.
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