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Item type:Publication, Structural, morphological, and magnetic characterizations of (Fe0.25Mn0.75)2O3 nanocrystals: A comprehensive stoichiometric determination(Elsevier Ltd, 2024-12-01)This report aims to investigate in depth FeMnO3, a material of interest due to its fascinating magnetic and multiferroic properties and its many applications in fields including lithium-ion batteries, microwave devices, and catalysis. However, understanding the precise stoichiometry of the material is crucial for a better comprehension of its physical properties. A cheap, simple, and repeatable sol-gel process was used to fabricate the FeMnO3 nanocrystals. Comprehensive multi-technique characterization of the as-fabricated FeMnO3 indicates that the main phase (94 wt%) is Fe0.5Mn1.5O3, although hematite appears as the minority phase (6 wt%). Magnetic characterization shows core-shell spin-glass like behavior, as well as paramagnetic-ferrimagnetic transitions and a Griffiths phase regime. EPR measurements revealed a strong and broad resonance line across the temperature range of 4.3 K–300 K, primarily influenced by the majority phase. The g-value decreases monotonically from 2.93 at 50 K to 2.18 at 300 K. There is a notable change in the resonance field and linewidth between 40 and 50 K, attributed to surface spin glass behavior. The EPR data below 50 K are in line with the core-shell model of (Fe0.25Mn0.75)2O3 nanoparticles. Below 50 K, the shell's spin system undergoes a transition from paramagnetic to spin-glass-like, with a critical temperature around 43 K. Above 50 K, the superparamagnetic minority phase significantly affects the temperature dependence of the resonance linewidth. These results hold particular importance as they advance our understanding of the intricate magnetic interactions present in FeMnO3. For the best possible use of this material platform in new technologies, such insights are essential. - 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, Impact of the thickness on the optical, electronic, and structural properties of sputtered Cu2S thin films(American Institute of Physics Inc., 2024-02-14)A successful hexagonal Cu 2 S p-type semiconductor thin film using DC magnetron sputtering is reported. Films with thickness gradients were deposited by taking advantage of deposition geometry and target dimensions. X-ray diffraction (XRD) analysis confirmed the exclusive formation of the hexagonal Cu 2 S phase. Elemental composition and thickness dependence with the sample position were determined using energy-dispersive x-ray spectroscopy. Optical properties, including the optical bandgap, refractive index, and extinction coefficient, were assessed by modeling transmittance spectra. The Tauc-Lorentz oscillator and Drude models were employed for this purpose. XRD data analysis successfully determined the film thickness ( t X R D ) as a function of the sample position, aligning well with thickness values ( t T ) derived from transmittance spectra analyses. These results were further supported by film thickness values ( t S E M ) obtained from cross-sectional SEM images. Charge carrier density and mobility, extracted from the optical models, were found to be consistent with DC electrical measurements. AC impedance curves were effectively modeled with RL-RC parallel circuits. The results indicate that the inductance (L) and capacitance (C) components of the films increase with decreasing film thickness. - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Enhancing the Photoconductivity and Gas Sensing Performance of TiO2/SnO2 Heterostructures Tuned by the Thickness of the SnO2 Upper Layer(Elsevier B.V., 2023-03-15)In this report, polycrystalline TiO2/SnO2 heterostructures with variable SnO2 film thickness were deposited by DC sputtering. Scanning electron microscopy images show a cracked surface in all films. The latter gets more widespread as the SnO2 layer thickness increases with deposition time. Optical transmittance measurements were used to determine the thickness of the TiO2 and SnO2 polycrystalline films. Photocurrent measurements of pure SnO2 films using UVA irradiation revealed a good response for thinner SnO2 films, however, these decrease as film thickness increases. Besides, photocurrent response is enhanced for the TiO2/SnO2 heterostructures over pure SnO2 film. It is thought that a high photocurrent response can be produced due to the improved ability to separate the photoinduced electrons and holes, as well as due to suitable charge management at the TiO2 and SnO2 interface. Additionally, the large amount of active sites for the thinner SnO2 upper layer favors better room temperature gas response to ethanol than that obtained for single SnO2 films. These features make the TiO2/SnO2 heterostructure a promising candidate for room temperature gas sensors and photosensitivity applications.