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Author: search.filters.author.Carlos A. Vilca HuayhuaLanguage: search.filters.language.English

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    Tailoring structural, electrical, and optical properties of ITO thin films via vacuum-pressure annealing: An experimental and theoretical study
    (Elsevier BV, 2025-02-25)
    This study explores the structural, optical, and electronic properties of polycrystalline Sn-doped In2O3 (ITO) thin films deposited via DC sputtering method and annealed at 600∘ C for 2 h under different vacuum pressures (VPs) ranging from 1 to 10−6 mbar. The bandgap energy increases from 3.8 eV to 4.1 eV with the vacuum, driven by the Burstein-Moss effect, accompanied by the reduction of Urbach energy, crystallinity improvement and reduction of disorder. This reduction is likely due to enhanced migration of interstitial oxygen ions with vacuum during the annealing. The electrical resistivity decreases significantly when the carrier concentration increases, meanwhile, the effective mass increases (from 0.3 to 0.5me), which is linked to a transition from parabolic to non-parabolic density of states. Near-infrared optical analysis reveals higher optical mobility than Hall mobility, particularly in samples annealed under lower vacuum, which was assigned to the predominant grain boundary scattering process. Photocurrent generation correlates with photoabsorption, Urbach energy, and crystallite size, which decrease as the vacuum is increased. Impedance analysis shows a reduction of the resistance and inductance, with an increase of the capacitance and carrier concentration with the vacuum of the annealing. DFT calculations confirm oxygen vacancies enhance charge density and widen the bandgap, aligning with experimental findings. These results highlight the role of oxygen vacancies in tuning ITO properties for optoelectronic applications.
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    Engineering dynamic defect compensation in Sn-Doped In2O3 thin films for enhanced optoelectronic performance
    (Elsevier BV, 2026-07-15)
    Sn-doped In2O3 is a typical transparent conducting oxide, yet the mechanisms governing carrier suppression and functional degradation at high doping levels remain unclear. Here, defect engineering via controlled Sn incorporation is employed to tune dynamic defect compensation, enabling direct correlation between defect chemistry and optoelectronic functionality. A non-monotonic evolution of lattice parameter and carrier density reveals two distinct regimes. At low Sn concentrations, enhanced free-electron density induces a Burstein–Moss bandgap widening. Beyond a critical doping threshold, cooperative compensation mediated by Sn4+/Sn2+ coexistence and oxygen interstitials suppresses carrier density, activating competition between bandgap renormalization and the Burstein–Moss shift. Density functional theory calculations confirm the electronic impact of this defect complex. Remarkably, the evolution of photocurrent closely mirrors the methane sensing response, demonstrating that oxygen-related defects regulate charge-transfer dynamics. These findings establish dynamic defect compensation as a tunable design principle for engineering multifunctional transparent conducting oxides.
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    Effect of the working pressure on the structural, morphological, optical, electrical and gas sensor properties of ZnO films grown by DC magnetron sputtering
    (Elsevier BV, 2026-02-01)
    In this work, ZnO thin films were deposited by DC magnetron sputtering under varying working pressures and subsequently annealed in air, followed by vacuum thermal annealing. The increase of working pressure drive to the reduction of the film thickness, crystallite size, lattice constants, and to the strengthening of the (002) X-ray diffraction peak, suggesting changes in the in oxygen vacancy concentration. Scanning electron microscopy revealed the formation of randomly distributed nanorods, while UV–Vis spectroscopy data analysis evidenced the presence of defect-related levels inside the band gap. As the thickness decreases, Hall measurements show a noticeable drop in charge carrier density and mobility, which is linked to the combined impact of defects and the decreasing size of crystallites. This suggests that thicker films exhibited a higher density of zinc interstitials, whereas thinner films exhibit more oxygen vacancies (VO[jls-end-space/]), mainly associated with surface states, as supported by temperature-dependent resistance measurements and photocurrent analysis. Gas detection tests demonstrated a superior response to methane (CH4[jls-end-space/]) for thinner films at 200 °C, attributed to their higher oxygen vacancy concentration. Photocurrent and gas sensing measurements showed similar trends, indicating a common defect-driven mechanism. These results highlight the potential of tuning defect chemistry in ZnO films to optimize their performance for gas sensing and optoelectronic devices.
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