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<p>The present study demonstrates the influence of synthesis temperature on the microstructural, optical, morphological, dielectric, and electrical properties of ZnO nanostructures prepared via the hydrothermal process at varying temperatures. X-ray diffraction (XRD) patterns ensured that all samples&#xa0;possess&#xa0;polycrystalline wurtzite structure&#xa0;with&#xa0;hexagonal phase belonging to the <i>P6_3mc</i> space group, with crystallite sizes ranging from 28 to 46&#xa0;nm as synthesis temperature increased. Raman and FTIR spectra revealed consistent Raman active modes and the effect of temperature on functional group vibrations, respectively. SEM and EDS analyses exhibited distinct surface morphologies and elemental compositions. The optical bandgap of the nanostructures reduced from 2.89 to 2.66&#xa0;eV as synthesis temperature varies from 100&#xa0;°C to 200&#xa0;°C. The real part of the dielectric constant (εʹ) is&#xa0;reduced with rising frequency but slightly increases at lower frequencies with higher synthesis temperatures, which can be explained by the Maxwell–Wagner model. A rise in synthesis temperature led to a significant increase in a.c. conductivity, facilitating charge carrier hopping, and an exponential decrease in resistivity, indicating the semiconducting nature of the samples. The small polaron hopping model, fitted to the resistivity data, suggested the non-adiabatic type of polaron hopping and the increase in crystallite size contributes to a reduction in activation energy. Additionally, the variable range hopping (VRH) model suggests that&#xa0;an increase in the density of states (DoS) at the Fermi level a reduction in both hopping energy and hopping range.</p>

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Study of polaron hopping conduction mechanism and dielectric behavior of ZnO nanostructures synthesized via hydrothermal method at different temperatures

  • 期刊论文

  • 发表日期：

    2025年11月11日

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  • M. Raza Khan,
  • M. Abushad,
  • Hilal Ahmed,
  • Shahid Husain,
  • Wasi Khan

摘要

The present study demonstrates the influence of synthesis temperature on the microstructural, optical, morphological, dielectric, and electrical properties of ZnO nanostructures prepared via the hydrothermal process at varying temperatures. X-ray diffraction (XRD) patterns ensured that all samples possess polycrystalline wurtzite structure with hexagonal phase belonging to the P6_3mc space group, with crystallite sizes ranging from 28 to 46 nm as synthesis temperature increased. Raman and FTIR spectra revealed consistent Raman active modes and the effect of temperature on functional group vibrations, respectively. SEM and EDS analyses exhibited distinct surface morphologies and elemental compositions. The optical bandgap of the nanostructures reduced from 2.89 to 2.66 eV as synthesis temperature varies from 100 °C to 200 °C. The real part of the dielectric constant (εʹ) is reduced with rising frequency but slightly increases at lower frequencies with higher synthesis temperatures, which can be explained by the Maxwell–Wagner model. A rise in synthesis temperature led to a significant increase in a.c. conductivity, facilitating charge carrier hopping, and an exponential decrease in resistivity, indicating the semiconducting nature of the samples. The small polaron hopping model, fitted to the resistivity data, suggested the non-adiabatic type of polaron hopping and the increase in crystallite size contributes to a reduction in activation energy. Additionally, the variable range hopping (VRH) model suggests that an increase in the density of states (DoS) at the Fermi level a reduction in both hopping energy and hopping range.