Abstract
In this research, Al-doped and (Al, Fe) codoped ZnO films were prepared on glass substrate by the sol–gel method. The surface morphology, structure, and optical property were characterized by scanning electron microscope (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and Ultraviolet-Visible-Near-infrared (UV-Vis-NIR) spectroscopy. The film surface morphologies all exhibited granular characteristics. With the Fe doping concentration increasing, the codoped films had smaller grain size and tended to be smoother. XRD analysis revealed that all films had a hexagonal wurtzite structure. The codoping can contribute to more Al and Fe ions entering the ZnO crystal structure, but result in the crystalline degree of the films decreasing. XPS results showed that the Al and Fe irons in the films exist in the form of trivalent. Moreover, the doped films had higher transmission, especially for codoped (Fe:Al = 3) film, but their absorption edge shifted to the short-wavelength direction.
Highlights
Coatings 2021, 11, 946. https://Zinc oxide (ZnO), as an important semiconductor material, has many excellent properties such as wide band gap energy of 3.37 eV, high exciton binding energy of 60 meV, non-toxicity, chemical stability, biocompatibility, and optical transparency
The undoped, Al-doped, and (Al, Fe) codoped ZnO films were deposited on a glass substrate (CAS: 65997-17-3, Bohui Medical Supplies Co., Ltd, Taizhou, China) by the dip-coating sol–gel method similar to those described in the literature [14,15,16]
The surface chemical state was analyzed with PHI5700 X-ray photoelectron spectroscopy (XPS) (PHI, Inc., Lafayette, LA, USA), using a Mg Kα source (1253.6 eV)
Summary
Zinc oxide (ZnO), as an important semiconductor material, has many excellent properties such as wide band gap energy of 3.37 eV, high exciton binding energy of 60 meV, non-toxicity, chemical stability, biocompatibility, and optical transparency. These properties lead to a range of potential applications in ultraviolet photoconductive detectors, solar cells, photocatalysts, and light emitting diodes [1]. Zn films can be doped with some metal elements to improve their optical, electrical, and magnetic properties [4]. In this work, (Al, Fe) codoped ZnO films were synthesized by the sol–gel method, and their surface morphology, structural, and optical properties were investigated.
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