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<p>This study investigates cobalt–lanthanum (Co–La) co-doped zinc oxide (ZnO) thin films, which have received limited attention despite their potential in optoelectronics. The films were synthesized via spray pyrolysis, varying Co–La concentrations from 1 to 5 weight percent (wt%). Characterization techniques such as X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), optical spectroscopy, and direct current (DC) conductivity measurements were utilized. XRD confirmed a hexagonal ZnO structure at both 1 wt% and 5 wt% Co–La concentrations, with a distinct La<sub>2</sub>O<sub>3</sub> phase observed at 3 wt%. Crystallite sizes calculated using Scherrer’s equation were approximately 25.89–26.82 nm across different concentrations. FE-SEM analysis revealed average grain sizes of 150.3–187.9 nm, indicating agglomeration effects. The surface roughness of all films was measured using AFM, revealing that the RMS roughness of the surfaces increased with higher Co–La ratios. The band gap slightly increased with higher co-dopant concentrations, while Urbach energy decreased. Photoluminescence (PL) spectra showed multiple peaks across all films, reflecting their defect-rich nature, with variations in peak position and intensity based on co-dopant levels. DC conductivity measurements indicated two activation energy values for films at 1&#xa0;wt% and 5&#xa0;wt%, while the film with 3 wt% exhibited a single value linked to the La<sub>2</sub>O<sub>3</sub> phase identified by XRD. Furthermore, we evaluated the UV sensing performance of the deposited films against two wavelengths: 365 nm and 245 nm. Sensitivity reached as high as 18,000 for some films when an applied potential of 30 V was used.</p>

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ZnO thin films: the impact of Co–La co-doping on structure and performance

  • 期刊论文

  • 发表日期：

    2025年7月21日

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  • Salma Alshehri,
  • M. D. Alshahrani,
  • Ahmed A. Aboud

摘要

This study investigates cobalt–lanthanum (Co–La) co-doped zinc oxide (ZnO) thin films, which have received limited attention despite their potential in optoelectronics. The films were synthesized via spray pyrolysis, varying Co–La concentrations from 1 to 5 weight percent (wt%). Characterization techniques such as X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), optical spectroscopy, and direct current (DC) conductivity measurements were utilized. XRD confirmed a hexagonal ZnO structure at both 1 wt% and 5 wt% Co–La concentrations, with a distinct La2O3 phase observed at 3 wt%. Crystallite sizes calculated using Scherrer’s equation were approximately 25.89–26.82 nm across different concentrations. FE-SEM analysis revealed average grain sizes of 150.3–187.9 nm, indicating agglomeration effects. The surface roughness of all films was measured using AFM, revealing that the RMS roughness of the surfaces increased with higher Co–La ratios. The band gap slightly increased with higher co-dopant concentrations, while Urbach energy decreased. Photoluminescence (PL) spectra showed multiple peaks across all films, reflecting their defect-rich nature, with variations in peak position and intensity based on co-dopant levels. DC conductivity measurements indicated two activation energy values for films at 1 wt% and 5 wt%, while the film with 3 wt% exhibited a single value linked to the La2O3 phase identified by XRD. Furthermore, we evaluated the UV sensing performance of the deposited films against two wavelengths: 365 nm and 245 nm. Sensitivity reached as high as 18,000 for some films when an applied potential of 30 V was used.