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<p>Dysprosium oxide (Dy<sub>2</sub>O<sub>3</sub>) is a stable binary rare earth oxide, where the rare earth ions are present in trivalent form. Due to its insolubility and high thermal stability, Dy<sub>2</sub>O<sub>3</sub> is considered a promising material for laser and optical applications. Furthermore, the structural and optical properties of Dy<sub>2</sub>O<sub>3</sub> are renowned for being enhanced due to its 4f electrons. In this research, we study the effect of post-deposition annealing on the structural and optical properties of Dy<sub>2</sub>O<sub>3</sub> films deposited at 250°C on a <i>n</i>-GaAs substrate by electron beam deposition under ultrahigh vacuum conditions. Atomic force microscopy (AFM) and x-ray diffraction (XRD) were used for structural characterization of the samples. The annealed sample exhibited crystallite diameters between 42&#xa0;nm and 55&#xa0;nm, compared to 18–35&#xa0;nm in the unannealed sample. This increase in crystallite size suggests that the annealing temperature supported the development of larger crystal grains and improved the film’s overall crystallinity. Atomic force microscopy and fractal analysis were used to analyze the surface topography in order to understand how the annealing temperature affects the layer surface. Annealing reduced the fractal dimension from 2.68 (unannealed) to 2.57, indicating improved surface uniformity and reduced irregularity. Using photoluminescence (PL) and reflectance measurements with an ultraviolet–visible–near-infrared (UV–Vis–NIR) spectrophotometer, the optical and photoluminescence characteristics of the Dy<sub>2</sub>O<sub>3</sub> film were investigated both before and after post-deposition annealing. Defect states in the materials were further supported by photoluminescence spectroscopy. Therefore, it appears that diffuse reflectance spectroscopy is a useful tool for analyzing the signature of defects in the samples. The annealed Dy<sub>2</sub>O<sub>3</sub> sample exhibits a dominant Gaussian component, confirming enhanced intrinsic luminescence due to improved structural ordering. Furthermore, during annealing at 400°C, the bandgap increased from 2.95&#xa0;eV to 3.1&#xa0;eV, according to the Tauc plot. After fabricating Au/Co/Dy<sub>2</sub>O<sub>3</sub>/<i>n</i>-GaAs metal–oxide–semiconductor (MOS) structures, current–voltage (<i>I–V</i>) measurements were used to evaluate the devices’s performance. <i>I–V</i> characterization suggests that Schottky emission, Poole–Frenkel conduction, Fowler–Nordheim tunneling, and space-charge-limited current are the dominant conduction mechanisms in the deposited Dy<sub>2</sub>O<sub>3</sub> layers.</p>

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Impact of Annealing on the Structural and Optical Properties of Dysprosium Oxide (Dy2O3) Thin Films Deposited on n-GaAs via Electron Beam Deposition

  • 期刊论文

  • 发表日期：

    2025年10月14日

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  • Hayet Saghrouni,
  • Lotfi Beji

摘要

Dysprosium oxide (Dy2O3) is a stable binary rare earth oxide, where the rare earth ions are present in trivalent form. Due to its insolubility and high thermal stability, Dy2O3 is considered a promising material for laser and optical applications. Furthermore, the structural and optical properties of Dy2O3 are renowned for being enhanced due to its 4f electrons. In this research, we study the effect of post-deposition annealing on the structural and optical properties of Dy2O3 films deposited at 250°C on a n-GaAs substrate by electron beam deposition under ultrahigh vacuum conditions. Atomic force microscopy (AFM) and x-ray diffraction (XRD) were used for structural characterization of the samples. The annealed sample exhibited crystallite diameters between 42 nm and 55 nm, compared to 18–35 nm in the unannealed sample. This increase in crystallite size suggests that the annealing temperature supported the development of larger crystal grains and improved the film’s overall crystallinity. Atomic force microscopy and fractal analysis were used to analyze the surface topography in order to understand how the annealing temperature affects the layer surface. Annealing reduced the fractal dimension from 2.68 (unannealed) to 2.57, indicating improved surface uniformity and reduced irregularity. Using photoluminescence (PL) and reflectance measurements with an ultraviolet–visible–near-infrared (UV–Vis–NIR) spectrophotometer, the optical and photoluminescence characteristics of the Dy2O3 film were investigated both before and after post-deposition annealing. Defect states in the materials were further supported by photoluminescence spectroscopy. Therefore, it appears that diffuse reflectance spectroscopy is a useful tool for analyzing the signature of defects in the samples. The annealed Dy2O3 sample exhibits a dominant Gaussian component, confirming enhanced intrinsic luminescence due to improved structural ordering. Furthermore, during annealing at 400°C, the bandgap increased from 2.95 eV to 3.1 eV, according to the Tauc plot. After fabricating Au/Co/Dy2O3/n-GaAs metal–oxide–semiconductor (MOS) structures, current–voltage (I–V) measurements were used to evaluate the devices’s performance. I–V characterization suggests that Schottky emission, Poole–Frenkel conduction, Fowler–Nordheim tunneling, and space-charge-limited current are the dominant conduction mechanisms in the deposited Dy2O3 layers.