Search Results (200)

Photocatalytic composite materials (TiO₂/SiO₂/BFSF) were first fabricated using the sol–gel method of loading SiO₂ and TiO₂ on blast furnace slag fibers (BFSFs) in sequence and using them as a new carrier. Then, TG-DTA, XRD, BET, SEM-EDS, and UV-Vis absorption spectra, as well as spectrophotometric measurements, were employed to analyze the physicochemical properties of TiO₂. The influence of SiO₂ coating, the number of impregnations in TiO₂ sol, the calcination temperature, and the number of repeated usages on the activity of TiO₂/SiO₂/BFSF was researched by analyzing the degradation of methylene blue (MB) aqueous solution. The results show that SiO₂ could increase the load of TiO₂, impede the growth of TiO₂ grains, and inhibit the recombination of electron–hole pairs, ultimately enhancing the photocatalytic activity of samples. The activity of TiO₂/SiO₂/BFSF first quickly increased and then slowly decreased with an increase in the loading times of TiO₂ sol and calcination temperature. After three impregnations in TiO₂ sol and calcining at 450 °C for 2.5 h, a uniform and compact anatase TiO₂ thin film was deposited on the surface of TiO₂/SiO₂/BFSF, showing the strongest activity. When this sample was used to degrade MB aqueous solution for 180 min under ultraviolet light irradiation, the degradation proportion reached a maximum of 96%. After four reuses, the degradation ratio could still reach 67%. In addition, three potential photocatalytic mechanisms were proposed. Finally, the high-value-added application of blast furnace slag for preparing photocatalytic composite materials was achieved, successfully turning solid waste into “treasure”. Full article

This study investigated the enhancement of Cu₂MnSnS₄ (CMTS) thin films’ photocatalytic properties through potassium (K) doping for rhodamine B degradation under visible light. K-doped CMTS films synthesized using spray pyrolysis technology achieved a 98% degradation efficiency within 120 min. The physical property improvements were quantitatively validated through X-ray diffraction (XRD) analysis, which confirmed enhanced crystallinity. Scanning electron microscopy (SEM) revealed significant modifications in surface morphology as a function of potassium content, highlighting its influence on film growth dynamics. Optical characterization demonstrated a pronounced reduction in transmittance, approaching negligible values at 7.5% potassium doping, and a narrowed optical band gap of 1.41 eV, suggesting superior light absorption capabilities. Photocatalytic performance was significantly enhanced, achieving a Rhodamine B degradation efficiency of up to 98% at 7.5% doping. These enhancements collectively improved the material’s light-harvesting capabilities and charge separation efficiency, positioning K-doped CMTS as a highly effective photocatalyst compared to other ternary and quaternary materials. Full article

We consider light, high-absorbance, low-reflectance, electrically large layered sheet structures composed of thin carbon nanotube films. Such structures can be utilized in electromagnetic absorption and shielding applications in the X-band. They are of increasing interest in sensor-enabling technologies, stealth systems, and EMI shielding of electronic components. Especially in aerospace, this is crucial, as sensors are integral to aerospace engineering, enhancing the safety, efficiency, and performance of aircraft and spacecraft. To that end, sheets with carbon nanotube films embedded in a glass fiber polymer matrix are fabricated. The films have a thickness of around 70 μm. As shown, they cause a significant attenuation of the electromagnetic field. For shielding applications, a single-film sheet structure with total thickness of 1.65 mm presents an attenuation of around 25 dB in the transmission coefficient, while the attenuation can reach 37 dB for a two-film sheet structure with thickness of 1.8 mm. Shielding effectiveness performance is found to be greater than 35 dB for the two-film sheet structure. For applications requiring both high shielding and absorption, a two-layered structure with a thickness of 4.65 mm has been designed. The absorption, represented by the Loss Factor, is calculated to achieve values greater than 90%. The simulation results show good agreement with the measured data. The findings demonstrate a promising structure for materials suitable for sensor housings and smart electromagnetic environments where the suppression of electromagnetic interference is critical. In conclusion, the addition of carbon nanotube films, even at micrometer thicknesses, within a glass fiber polymer matrix significantly enhances both electromagnetic shielding and absorption performance. Full article

Tin(II) sulfide(SnS)/titanium(IV) oxide (TiO₂) heterostructure thin films were prepared by radio-frequency magnetron sputtering to investigate the enhancement effect of the formed heterojunction on the photocatalytic performance. By adjusting the sputtering time to vary the thickness of the SnS layer, the crystallinity and light-absorption properties of the light-absorbing layer and the quality of the heterojunction interface were effectively controlled, thereby optimizing the fabrication process of the heterojunction. It was found that when the SnS layer thickness was 244 nm and the TiO₂ layer thickness was 225 nm, the heterostructure film exhibited optimal photoelectrochemical performance, generating the highest photocurrent of 3.03 µA/cm² under visible light, which was 13.8 times that of a pure TiO₂ film and 2.4 times that of a pure SnS film of the same thickness. Additionally, it demonstrated the highest degradation efficiency for methylene blue dye. The improved photoelectrochemical performance of the SnS/TiO₂ heterostructure film can be primarily attributed to the following: (1) the incorporation of narrow-bandgap SnS effectively broadens the light-absorption range, improving visible-light harvesting; (2) the staggered band alignment between SnS and TiO₂ forms a type-II heterojunction, significantly enhancing the charge carrier separation and transport efficiency. The present work demonstrated the feasibility of magnetron sputtering for constructing high-quality SnS/TiO₂ heterostructures, providing insights into the design and fabrication of photocatalytic heterojunctions. Full article

Artificial photoelectric synapses exhibit great potential for overcoming the Von Neumann bottleneck in computational systems. All-inorganic halide perovskites hold considerable promise in photoelectric synapses due to their superior photon-harvesting efficiency. In this study, a novel wavy-structured CsPbBr₃/ZnO hybrid film was realized by depositing zinc oxide (ZnO) onto island-like CsPbBr₃ film via atomic layer deposition (ALD) at 70 °C. Due to the capability of ALD to grow high-quality films over small surface areas, dense and thin ZnO film filled the gaps between the island-shaped CsPbBr₃ grains, thereby enabling reduced light-absorption losses and efficient charge transport between the CsPbBr₃ light absorber and the ZnO electron-transport layer. This ZnO/island-like CsPbBr₃ hybrid synaptic transistor could operate at a drain-source voltage of 1.0 V and a gate-source voltage of 0 V triggered by green light (500 nm) pulses with low light intensities of 0.035 mW/cm². The device exhibited a quiescent current of ~0.5 nA. Notably, after patterning, it achieved a significantly reduced off-state current of 10⁻¹¹ A and decreased the quiescent current to 0.02 nA. In addition, this transistor was able to mimic fundamental synaptic behaviors, including excitatory postsynaptic currents (EPSCs), paired-pulse facilitation (PPF), short-term to long-term plasticity (STP to LTP) transitions, and learning-experience behaviors. This straightforward strategy demonstrates the possibility of utilizing neuromorphic synaptic device applications under low voltage and weak light conditions. Full article

The Al-Sb co-doped SnO₂ composite thin films were prepared by the sol–gel spin-coating method. The structure, morphology, optical and electrical properties of the samples were investigated using XRD, XPS, SEM, UV-Vis spectroscopy, and Hall effect tester, respectively. It was found that when the aluminum doping amount was 15 at%, the resistivity of the sample was the lowest, and the overall optoelectronic performance was the best. Moreover, the Al-SnO₂ composite thin film transformed from an n-type semiconductor to a p-type semiconductor. When Al and Sb were co-doped, the carrier concentration increased significantly from 4.234 × 10¹⁹ to 6.455 × 10²⁰. Finally, the conduction type of the Al-Sb-SnO₂ composite thin film changed from p-type to n-type. In terms of optical performance, the transmittance of the Al-Sb co-doped SnO₂ composite thin films in the visible light region was significantly improved, reaching up to 80% on average, which is favorable for applications in transparent optoelectronic devices. Additionally, the absorption edge of the thin films exhibited a blue-shift after co-doping, indicating an increase in the bandgap energy, which can be exploited to tune the light-absorption properties of the thin films for specific photonic applications. Full article

Nanoplasmonic structures have emerged as a promising approach to address light trapping limitations in thin-film optoelectronic devices. This study investigates the integration of metallic nanoparticle arrays onto nanocrystalline silicon (nc-Si:H) thin films to enhance optical absorption through plasmonic effects. Using finite-difference time-domain (FDTD) simulations, we systematically optimize key design parameters, including nanoparticle geometry, spacing, metal type (Ag and Al), dielectric spacer material, and absorber layer thickness. The results show that localized surface plasmon resonances (LSPRs) significantly amplify near-field intensities, improve forward scattering, and facilitate coupling into waveguide modes within the active layer. These effects lead to a measurable increase in integrated quantum efficiency, with absorption improvements reaching up to 30% compared to bare nc-Si:H films. The findings establish a reliable design framework for engineering nanoplasmonic architectures that can be applied to enhance performance in photovoltaic devices, photodetectors, and other optoelectronic systems. Full article

Obtaining wide energy-gap semiconductor ultra-thin films is an important aspect for their application in sulfide-based solar cells. By reducing the optical losses associated with light reflection and exhibiting absorption edge shifts towards short wavelengths, these layers can optimize the amount of photons interacting with the active photovoltaic material, which increases the conversion efficiency of the solar cell. Ultra-thin CdS films were prepared by a low-cost chemical synthesis and the impact of silver doping on the optical, structural, and morphological properties was evaluated. SEM micrographs revealed that the layers are ultra-thin, homogeneous and uniform, with a reduction in particle size with increasing doping concentration. X-ray diffraction data confirmed the crystallization of CdS in the hexagonal phase for all prepared samples. A low concentration contributed to the formation of Ag₂S in the monoclinic phase according to the diffractograms. The optical properties of the thin films revealed an absorption edge shift that increased the CdS band gap from 2.267 ± 0.007 to 2.353 ± 0.005 eV with increasing doping concentration, improving the spectral transmittance response. These results make these layers particularly useful for implementation in next-generation flexible photovoltaic devices. Full article

Silk fibroin (SF), the primary protein in silkworm silk, has emerged as a promising organic nonlinear optical material due to its unique combination of optical transparency, biocompatibility, and environmental sustainability. In this study, we investigate the nonlinear optical properties of SF thin films using the z-scan technique with femtosecond laser pulses (35 fs, 800 nm, 1 kHz). Our results reveal a strong self-defocusing effect (negative nonlinear refractive index) and significant multiphoton absorption, demonstrating SF’s tunable nonlinear response. Additionally, optical transmittance measurements confirm SF’s partial transparency in the deep UV region, enhancing its potential for second-harmonic generation (SHG) and efficient light frequency conversion. These findings address a key knowledge gap in nonlinear optics, positioning SF as a versatile biopolymer for advanced photonic applications. Full article

This research is on the structural, optical, and electrical properties of SnO₂ and ZnO thin films, which are increasingly used in many electronic devices, including gas sensors, light-emitting diodes, and solar cells. For the various applications, it is essential to accurately determine the band gap energy, as it controls the optical and electrical behavior of the material. However, there is no single method for its determination; rather, different approximations depend on the crystalline quality and the doping level because these modify the energy band structure of the semiconductor. With the aim of analyzing the various approaches, SnO₂ and ZnO films were prepared by sputtering on unheated glass substrates and subsequently annealed in N₂ at various temperatures between 250 °C and 450 °C. These samples showed different crystallite sizes, absorption coefficients, and free carrier concentrations depending on the material and the annealing temperature. Analysis of the results shows that the expression developed for amorphous materials underestimates the band gap value, and the so-called unified method tends to overestimate it, while the equations for perfect or heavily doped crystals give band gap energies more consistent with the doping level, regardless of the crystalline quality of the films. Full article

We present structural, morphological, optical and photocatalytic properties of multiferroic Bi_0.98Ba_0.02FeO₃ (BBFO2) perovskite thin films prepared by a combined sol–gel and spin-coating method. X-ray diffraction (XRD) analysis revealed that all the perovskite films consisted of the stable polycrystalline rhombohedral phase structure (space group R3c) with a tolerance factor of 0.892. By using Rietveld refinement of diffractogram XRD data, crystallographic parameters, such as bond angle, bond length, atom position, unit cell parameters, and electron density measurements were computed. Scanning electron microscopy (SEM) allowed us to assess the homogeneous and smooth surface morphology of the films with a small degree of porosity, while chemical surface composition characterization by X-ray photoelectron spectroscopy (XPS) showed the presence of Bi, Fe, O and the doping element Ba. Absorption measurements allowed us to determine the energy band gap of the films, while photoluminescence measurements have shown the presence of oxygen vacancies, which are responsible for the enhanced photocatalytic activity of the material. Photocatalytic degradation experiments of Methylene Blue (MB), Methyl orange (MO), orange G (OG), Violet and Rhodamine B (RhB) performed on top of BBFO2 thin films under solar light showed the degradation of all pollutants in varying discoloration efficiencies, ranging from 81% (RhB) to 54% (OG), 53% (Violet), 47% (MO) and 43% (MB). Full article

The integration of a photodetector that converts optical signals into electrical signals is essential for scalable integrated lithium niobate photonics. Two-dimensional materials provide a potential high-efficiency on-chip detection capability. Here, we demonstrate an efficient on-chip photodetector based on a few layers of MoTe₂ on a thin film lithium niobate waveguide and integrate it with a microresonator operating in an optical telecommunication band. The lithium-niobate-on-insulator waveguides and micro-ring resonator are fabricated using the femtosecond laser photolithography-assisted chemical–mechanical etching method. The lithium niobate waveguide-integrated MoTe₂ presents an absorption coefficient of 72% and a transmission loss of 0.27 dB µm⁻¹ at 1550 nm. The on-chip photodetector exhibits a responsivity of 1 mA W⁻¹ at a bias voltage of 20 V, a low dark current of 1.6 nA, and a photo–dark current ratio of 10⁸ W⁻¹. Due to effective waveguide coupling and interaction with MoTe₂, the generated photocurrent is approximately 160 times higher than that of free-space light irradiation. Furthermore, we demonstrate a wavelength-selective photonic device by integrating the photodetector and micro-ring resonator with a quality factor of 10⁴ on the same chip, suggesting potential applications in the field of on-chip spectrometers and biosensors. Full article

When a phosphor film based on a photonic crystal (PhC) is excited at the photonic band-edge wavelength, the absorption of excitation light increases, which can potentially enhance the color-conversion efficiency. In this study, we modeled a two-dimensional (2D) PhC quantum dot (QD) film with a square-lattice structure using the finite-difference time-domain method to theoretically investigate its optical properties. The embedment of a thin-film layer with a high refractive index on the surface of the QD film enables an effective localization of excitation light within the phosphor. A numerical estimation shows that the optimized 2D PhC QD film can enhance the light absorption by up to 4.2 times with a monochromatic source and by up to 1.8 times with a broadband (FWHM~30 nm) source compared to a flat-type reference QD film. Full article

Polycrystalline zinc oxide (ZnO) thin films were deposited on soda-lime glass substrates using the chemical spray pyrolysis method at 450 °C. The samples were irradiated with 8 keV H⁺ ions at three different fluences using a Colutron ion gun. The effects of the irradiation on the structural, morphological, and optical properties were studied with different techniques, including Rutherford Backscattering Spectrometry (RBS), X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), and Ultraviolet and Visible Spectroscopy (UV–Vis). The results show that ion irradiation enhances crystallinity, narrowing the optical band gap. The changes in transmittance are related to defect formation within the material, which acts as light absorption and re-emission centers. A shifting of the film’s preferred growth orientation to the c-axis and changing the grain morphology and size distribution was detected. We observed an increase in the lattice parameters observed after irradiation, suggesting an expansion of the crystalline structure due to ions incorporation and defects within the ZnO crystal lattice. The morphological study shows an increase in the average size of the large particles after irradiation. This change is attributed to the emergence of defects and nucleation centers during irradiation. The average size of small particles remained relatively constant after irradiation, suggesting that small particles are more stable and less susceptible to external influences, resulting in fewer changes due to irradiation. Full article

This study presents the fabrication and characterization of a dual-functional Pt/Ga₂O₃/Pt optoelectronic synaptic device, capable of operating as both a memristor and a memcapacitor. We detail the optimized radio frequency (RF) sputtering parameters, including a base pressure of 8.7 × 10⁻⁷ Torr, RF power of 100 W, working pressure of 3 mTorr, and the use of high-purity Ga₂O₃ and Pt targets. These precisely controlled conditions facilitated the formation of an amorphous Ga₂O₃ thin film, as confirmed by XRD and AFM analyses, which demonstrated notable optical and electrical properties, including light absorption properties in the visible spectrum. The device demonstrated distinct resistive and capacitive switching behaviors, with memory characteristics highly dependent on the wavelength of the applied light. Ultraviolet (365 nm) exposure facilitated long-term memory retention, while visible light (660 nm) supported short-term memory behavior. Paired-pulse facilitation (PPF) measurements revealed that capacitance showed slower decay rates than EPSC, suggesting a more stable memory performance due to the dynamics of carrier trapping and detrapping at the insulator interface. Learning simulations further highlighted the efficiency of these devices, with improved memory retention upon repeated exposure to UV light pulses. Visual encoding simulations on a 3 × 3 pixel array also demonstrated effective multi-level memory storage using varying light intensities. These findings suggest that Ga₂O₃-based memristor and memcapacitor devices have significant potential for neuromorphic applications, offering tunable memory performance across various wavelengths from ultraviolet to red. Full article