{"title":"Outstanding ferroelectric properties in the narrow bandgap cobalt-substituted BiFeO3 spin-coated films","authors":"Jing Zhang, Jian-Qing Dai, Guang-Cheng Zhang, Xin-Jian Zhu","doi":"10.1007/s10971-024-06443-4","DOIUrl":null,"url":null,"abstract":"<p>Thin films of BiFe<sub>1−<i>x</i></sub>Co<sub><i>x</i></sub>O<sub>3</sub> (BFCO, <i>x</i> = 0–0.05) were prepared using the sol–gel method and deposited on a fluorine-doped tin oxide (FTO)/glass substrate. The crystal structure, surface morphology, dielectric properties, polarization, and optical characteristics of the BFCO thin films were investigated. X-ray diffraction (XRD) and Raman spectroscopy analyses show that Co doping induces lattice distortion. Scanning electron microscopy (SEM) images demonstrate that BFCO films with <i>x</i> = 0.03 possess uniform fine grains, which are crucial for their ferroelectric properties. From XPS pattern, it can be observed that Co doping can inhibit the conversion of Fe<sup>3+</sup> into Fe<sup>2+</sup>, and BiFe<sub>0.97</sub>Co<sub>0.03</sub>O<sub>3</sub> films exhibit greatly reduced oxygen vacancy concentration. Therefore, BiFe<sub>0.97</sub>Co<sub>0.03</sub>O<sub>3</sub> film was found to have the lowest leakage current density (<i>J</i> = 7.18 × 10<sup>−7</sup> A/cm<sup>2</sup>). The film demonstrates outstanding residual polarization at room temperature, with a value of <i>P</i><sub>r</sub> = 152.1 μC/cm<sup>2</sup>, more than twice the magnitude of that in pure BFO (<i>P</i><sub>r</sub> = 72.33 μC/cm<sup>2</sup>). Moreover, the dielectric properties of BFCO films show a significant improvement when compared to those of pure BFO samples. This enhancement is attributed to the Co doping-induced structural transition, along with a reduction in grain size and a decrease in the concentration of oxygen vacancies. Additionally, the BiFe<sub>0.97</sub>Co<sub>0.03</sub>O<sub>3</sub> film exhibits a narrower band gap (<i>E</i><sub>g</sub> = 1.69 eV) in comparison to the BFO film (<i>E</i><sub>g</sub> = 1.87 eV). Consequently, an expansion in the range of photovoltaic applications for BFO films can be achieved.</p><h3 data-test=\"abstract-sub-heading\">Graphical Abstract</h3>","PeriodicalId":664,"journal":{"name":"Journal of Sol-Gel Science and Technology","volume":null,"pages":null},"PeriodicalIF":2.3000,"publicationDate":"2024-07-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Journal of Sol-Gel Science and Technology","FirstCategoryId":"88","ListUrlMain":"https://doi.org/10.1007/s10971-024-06443-4","RegionNum":4,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q2","JCRName":"MATERIALS SCIENCE, CERAMICS","Score":null,"Total":0}
引用次数: 0
Abstract
Thin films of BiFe1−xCoxO3 (BFCO, x = 0–0.05) were prepared using the sol–gel method and deposited on a fluorine-doped tin oxide (FTO)/glass substrate. The crystal structure, surface morphology, dielectric properties, polarization, and optical characteristics of the BFCO thin films were investigated. X-ray diffraction (XRD) and Raman spectroscopy analyses show that Co doping induces lattice distortion. Scanning electron microscopy (SEM) images demonstrate that BFCO films with x = 0.03 possess uniform fine grains, which are crucial for their ferroelectric properties. From XPS pattern, it can be observed that Co doping can inhibit the conversion of Fe3+ into Fe2+, and BiFe0.97Co0.03O3 films exhibit greatly reduced oxygen vacancy concentration. Therefore, BiFe0.97Co0.03O3 film was found to have the lowest leakage current density (J = 7.18 × 10−7 A/cm2). The film demonstrates outstanding residual polarization at room temperature, with a value of Pr = 152.1 μC/cm2, more than twice the magnitude of that in pure BFO (Pr = 72.33 μC/cm2). Moreover, the dielectric properties of BFCO films show a significant improvement when compared to those of pure BFO samples. This enhancement is attributed to the Co doping-induced structural transition, along with a reduction in grain size and a decrease in the concentration of oxygen vacancies. Additionally, the BiFe0.97Co0.03O3 film exhibits a narrower band gap (Eg = 1.69 eV) in comparison to the BFO film (Eg = 1.87 eV). Consequently, an expansion in the range of photovoltaic applications for BFO films can be achieved.
期刊介绍:
The primary objective of the Journal of Sol-Gel Science and Technology (JSST), the official journal of the International Sol-Gel Society, is to provide an international forum for the dissemination of scientific, technological, and general knowledge about materials processed by chemical nanotechnologies known as the "sol-gel" process. The materials of interest include gels, gel-derived glasses, ceramics in form of nano- and micro-powders, bulk, fibres, thin films and coatings as well as more recent materials such as hybrid organic-inorganic materials and composites. Such materials exhibit a wide range of optical, electronic, magnetic, chemical, environmental, and biomedical properties and functionalities. Methods for producing sol-gel-derived materials and the industrial uses of these materials are also of great interest.