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Item type:Publication, Thickness dependence of the room-temperature ethanol sensor properties of Cu2O polycrystalline films(Institute of Physics, 2024-08-05)This study investigates the fabrication process of copper thin films via thermal evaporation, with precise control over film thickness achieved through Z-position adjustment. Analysis of the as-fabricated copper films reveals a discernible relationship between grain size (〈D〉) and Z-position, characterized by a phenomenological equation 〈 D 〉 XRD n ( Z ) = 〈 D 〉 0 n 1 + 3 2 r Z 2 + 15 8 r Z 4 , which is further supported by a growth exponent (n) of 0.41 obtained from the analysis. This value aligns well with findings in the literature concerning the growth of copper films, thus underlining the validity and reliability of our experimental outcomes. The resulting crystallites, ranging in size from 20 to 26 nm, exhibit a resistivity within the range of 3.3-4.6 μΩ · cm. Upon thermal annealing at 200 °C, cuprite Cu2O thin films are produced, demonstrating crystallite sizes ranging from ∼9 to ∼24 nm with increasing film thickness. The observed monotonic reduction in Cu2O crystallites relative to film thickness is attributed to a recrystallization process, indicating amorphization when oxygen atoms are introduced, followed by the nucleation and growth of newly formed copper oxide phase. Changes in the optical bandgap of the Cu2O films, ranging from 2.31 to 2.07 eV, are attributed mainly to the quantum confinement effect, particularly important in Cu2O with size close than the Bohr exciton diameter (5 nm) of the Cu2O. Additionally, correlations between refractive index and extinction coefficient with film thickness are observed, notably a linear relationship between refractive index and charge carrier density. Electrical measurements confirm the presence of a p-type semiconductor with carrier concentrations of ∼1014 cm−3, showing a slight decrease with film thickness. This phenomenon is likely attributed to escalating film roughness, which introduces supplementary scattering mechanisms for charge carriers, leading to a resistivity increase, especially as the roughness approaches or surpasses the mean free path of charge carriers (8.61 nm). Moreover, ab-initio calculations on the Cu2O crystalline phase to investigate the impact of hydrostatic strain on its electronic and optical properties was conducted. We believe that our findings provide crucial insights that support the elucidation of the experimental results. Notably, thinner cuprite films exhibit heightened sensitivity to ethanol gas at room temperature, indicating potential for highly responsive gas sensors, particularly for ethanol breath testing, with significant implications for portable device applications. - Some of the metrics are blocked by yourconsent settings
Item type:Publication, TL, EPR, and optical properties of undoped and Eu-, Ce-, Tb-, Sm-, Cu-, Mn-, and Li-doped MgSiO3 phosphors, synthesized by sol-gel combustion technique(Elsevier Ltd, 2024-11-01)Polycrystalline MgSiO3 samples, undoped or doped with rare earth- (Eu, Tb, Ce, Li, Sm), transition- (Mn and Cu), and alkali metal- (Li) elements, were prepared by the sol-gel combustion method and characterized by thermoluminescence, electron spin resonance, and optical properties. Enstatite and protoenstatite phases are observed in undoped and doped MgSiO3. Better TL results have been observed for phosphors doped with Tb, Ce, and Li (0.5 % mol). Fading experiments and the GCD method have been performed. EPR signals of gamma-irradiated phosphors indicate the formation of radiation-induced defect centers. Cu-doped MgSiO3 shows an unusual feature of the Cu2+ ion. The Cu2+ ion occupies a tetragonally compressed octahedral site, presenting an unconventional attribute. Optical bandgap value Eg is higher for the Ce, Tb, Mn, Li, Sm, and Cu-doped MgSiO3 phosphors. Ce, Li, and Tb dopant ions were found suitable for the MgSiO3 sample regarding its thermoluminescent response and its possible application in radiation dosimetry. - Some of the metrics are blocked by yourconsent settings
Item type:Publication, 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.7 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Cu-Doped SnO₂ Nanocrystals: Tunable Magnetism, Critical Incorporation Limit, and Defect Configuration Analysis by EPR and Ab Initio DFT(American Chemical Society, 2025-11-05)Copper in oxide semiconductors exhibits distinct electronic and magnetic behavior depending on its oxidation state, with Cu¹⁺ acting as a nonmagnetic impurity and Cu²⁺ contributing to the magnetic moment. In SnO₂, Cu incorporation represents a heterovalent substitution for Sn⁴⁺, which inherently promotes formation of compensating defects, particularly oxygen vacancies, that can strongly influence electronic and magnetic properties. To elucidate these effects, we investigated Cu-doped SnO₂ nanocrystals through combined experimental and theoretical approaches. Electron paramagnetic resonance (EPR) revealed that Cu incorporation of up to 3% enhances resonance intensity, consistent with isolated Cu²⁺ ions in the SnO₂ matrix. Beyond 3%, the EPR signal intensity decreases, and hyperfine parameters stabilize due to Cu²⁺ clustering and spin–spin interaction. Magnetization measurements revealed a paramagnetic phase (reflecting the presence of isolated Cu²⁺) that coexists with a ferromagnetic phase attributed to bound magnetic polarons and magnetic clustering. Complementary first-principles calculations showed that Cu substitution modifies the electronic structure by introducing localized density of states variations and altering the spin–charge density distribution, particularly near oxygen vacancies. Deeper in-plane defects were found to stabilize magnetization, whereas surface defects promoted competing ferromagnetic and antiferromagnetic interactions. Structural characterization by X-ray diffraction and morphological analysis using high-resolution transmission electron microscopy further confirmed lattice compression and particle size reduction with increasing Cu-content. The calculated and experimental findings provide a comprehensive and interconnected understanding, not yet emphasized in the literature, of the interplay among defects, doping, and magnetism in Cu-doped SnO₂.1