Visible Emission on Nanostructured CeO2 Thin Films Obtained by Spray Pyrolysis

• Published in: Physica status solidi. A, Applications and materials science Applications and materials science, 2020-11, Vol.217 (22), p.n/a
• Main Authors: García Sánchez, Mario Fidel, Ponce Rosas, Ismael, Malagón García, José Francisco, Andraca Adame, José Alberto, Lartundo‐Rojas, Luis, Santana, Guillermo
• Format: Article
• Language: English
• Subjects: Carrier gases; cerium dioxide; Cerium oxides; Crystal defects; Flow velocity; Gas flow; Grain size; Morphology; Nanostructure; nanostructured materials; Optical properties; Parameters; Photoelectrons; Photoluminescence; Spray pyrolysis; Substrates; Thin films
• ISSN: 1862-6300; 1862-6319
• DOI: 10.1002/pssa.202000235

Herein, the influence of the flow rate, substrate temperature, and thermal annealing at 700 °C on the optical and structural parameters of nanostructured ceria thin films prepared by ultrasonic spray pyrolysis is evaluated. The morphology, structure, and optical properties are studied by scanning electron microscopy, X‐ray diffraction, X‐ray photoelectron spectroscopy (XPS), and photoluminescence (PL). The spray conditions are optimized for obtaining smooth, dense, and homogeneous nanocrystalline films with grain sizes smaller than 20 nm. XPS demonstrates a high percentage (≈40%) of Ce3+ in the films, even in heat‐treated films (≈25%). The Ce3+ concentration does not depend on the growth temperature. Intense peaks at 575 and 618 nm are observed in PL measurements. These peaks are not reported in pure ceria thin films, they are dependent on the growth parameters (director and carrier gas flow rates and substrate temperature), and they are associated with levels produced by oxygen defects in the films. Variations in the flow rate modify the optimal temperature and the kinetic reaction, which also modifies the preferential orientation and the defect distribution in the films. Smooth, dense, and homogeneous nanostructured CeO2 thin films are deposited. Photoluminescence measurements show intense signals at 575 and 618 nm, which are associated with surface levels related to the high content of Ce3+ calculated in the films. Variations in flow rate modify the optimal deposition temperature, crystalline orientation, and defect distribution in the material.