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<p>In the present work, X-ray diffraction, HATR-FTIR spectroscopy, UV-visible spectroscopy, and measurements of film thickness and electrical resistivity were used to investigate structural, optical, and electrical changes induced during the Cu<sub>2</sub>O-CuO phase transformation as a function of the annealing temperature. XRD showed a Cu<sub>2</sub>O-CuO mixed phase formation at 200&#xa0;°C and a complete Cu<sub>2</sub>O-CuO phase transformation at 400&#xa0;°C. The crystallite size of the as-deposited Cu<sub>2</sub>O dropped from (14.6 ± 0.9) to (8 ± 0.7) nm after annealing at 200&#xa0;°C, whereas that of CuO increased, from (7.5 ± 0.6) to (11.1 ± 0.8) nm when the annealing temperature increased from 200 to 400&#xa0;°C. A CuO phase fraction of x<sub>XRD</sub> = 0.39 ± 0.08 was determined in the Cu<sub>2</sub>O-CuO mixed phase. The Cu<sub>2</sub>O-CuO phase transformation was verified by HATR-FTIR spectra, which also demonstrated the efficiency of the Cu<sub>2</sub>O phase over the CuO phase in CO<sub>2</sub> reduction. According to UV-visible spectroscopy, the mean transmittance in the visible light region dropped from (28.2 ± 0.8) % for Cu<sub>2</sub>O to (15.3 ± 1.0) % for CuO, and the band gap energy dropped from (2.33 ± 0.05) eV for Cu<sub>2</sub>O to (1.82 ± 0.04) eV for CuO. A CuO phase fraction of x = 0.44 was calculated, assuming that both phases contributed to the band gap energy of the Cu<sub>2</sub>O-CuO mixed phase. As the annealing temperature increased, the electrical resistivity dropped from (4.6 ± 0.2) x 10<sup>2</sup> Ω·cm for the as-deposited Cu<sub>2</sub>O to (17 ± 6) Ω·cm for CuO after annealing at 400&#xa0;°C. Using the effective medium theory, a CuO volume fraction f<sub>CuO</sub> = 0.45 was determined for the sample annealed at 200&#xa0;°C. With these characteristics, the studied materials will be suitable for application in different domains such as photovoltaics, optoelectronics, and photocatalysis.</p>

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Structural, optical, and electrical characterization of CuO fabricated by thermal annealing of Cu2O

  • 期刊论文

  • 发表日期：

    2026年8月4日

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  • R. Djebien,
  • A. Kabir

摘要

In the present work, X-ray diffraction, HATR-FTIR spectroscopy, UV-visible spectroscopy, and measurements of film thickness and electrical resistivity were used to investigate structural, optical, and electrical changes induced during the Cu2O-CuO phase transformation as a function of the annealing temperature. XRD showed a Cu2O-CuO mixed phase formation at 200 °C and a complete Cu2O-CuO phase transformation at 400 °C. The crystallite size of the as-deposited Cu2O dropped from (14.6 ± 0.9) to (8 ± 0.7) nm after annealing at 200 °C, whereas that of CuO increased, from (7.5 ± 0.6) to (11.1 ± 0.8) nm when the annealing temperature increased from 200 to 400 °C. A CuO phase fraction of xXRD = 0.39 ± 0.08 was determined in the Cu2O-CuO mixed phase. The Cu2O-CuO phase transformation was verified by HATR-FTIR spectra, which also demonstrated the efficiency of the Cu2O phase over the CuO phase in CO2 reduction. According to UV-visible spectroscopy, the mean transmittance in the visible light region dropped from (28.2 ± 0.8) % for Cu2O to (15.3 ± 1.0) % for CuO, and the band gap energy dropped from (2.33 ± 0.05) eV for Cu2O to (1.82 ± 0.04) eV for CuO. A CuO phase fraction of x = 0.44 was calculated, assuming that both phases contributed to the band gap energy of the Cu2O-CuO mixed phase. As the annealing temperature increased, the electrical resistivity dropped from (4.6 ± 0.2) x 102 Ω·cm for the as-deposited Cu2O to (17 ± 6) Ω·cm for CuO after annealing at 400 °C. Using the effective medium theory, a CuO volume fraction fCuO = 0.45 was determined for the sample annealed at 200 °C. With these characteristics, the studied materials will be suitable for application in different domains such as photovoltaics, optoelectronics, and photocatalysis.