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Application of MoWS2-rGO/PVA thin film as all-fiber pulse and amplitude modulators in the O-band region
摘要： In this work, a MoWS2-rGO/PVA thin film is fabricated and its applications as in amplitude modulation are demonstrated. Embedded in a praseodymium fluoride fiber laser cavity, the MoWS2-rGO/PVA thin film is able to induce pulsing in the laser output, which operates in the O-band region. As an optical amplitude modulator, the MoWS2-rGO/PVA thin film is capable of achieving a modulation efficiency of 0.17 dB/mW in the O-band region over a pump power range of 46.0 mW to 78.5 mW. C-band and L-band operation is also demonstrated, with modulation efficiencies of 0.30 dB/mW and 0.15 dB/mW, respectively over pump power ranges of 3.51 mW–52.17 mW and 24.4 mW–61.3 mW. This work can be improved by further engineering the composition ratio of the alloy material to enhance the modulation efficiency for both pulsed and amplitude modulations, giving rise to various applications, in particular in bio-medicine and manufacturing.
关键词： Amplitude modulator,MoWS2-rGO/PVA thin film,Pulse modulator,O-band
更新于2025-11-28 14:23:57
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Determination of nanoscale titanium oxide thin film phase composition using X-ray photoelectron spectroscopy valence band analysis
摘要： The phase compositions of nanoscale thick titania films on the titanium were determined using X-ray photoelectron spectroscopy valence band analysis for the first time, by deconvoluting the two-peak structure of valence band into five peaks and analysing the relative peak area. The titania films of thickness varying from about 2 nm to 8 μm were obtained by the air oxidation of commercially pure titanium at different temperatures. The titania films formed on titanium for oxidizing temperatures up to 200 °C were amorphous, with thickness < 10 nm. The sub-stoichiometric oxides present at the TiO2-Ti interface were composed of Ti3+, Ti2+ and Ti1+ states when the film of thickness was < 10 nm. At 300 °C, when the titania film thickness was < 20 nm, it was fully converted to rutile phase and remained stable up to 1000 °C. A broadening of full-width half-maxima of the core level peaks for the titania layers was attributed to the presence of surface hydroxyl group and stress gradient within the oxide layer. The absence of metastable anatase phase in the titania layers at lower temperatures was attributed to the presence of high stresses within the oxide layers owing to their nanoscale thickness.
关键词： X-ray Photoelectron Spectroscopy,Thin film,Valence band,Surface phase composition,Titania,Titanium
更新于2025-11-21 11:24:58
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The Role of Secondary Electron Emission in the Charging of Thin-Film Phase Plates
摘要： In the past few years, physical phase plates (PP) have become a viable tool to enhance the contrast of weak-phase objects in transmission electron microscopy (TEM). Thin-film PPs, such as the Zernike and Hilbert PP, are based on the mean inner potential of microstructured thin films [1,2]. Typically, a thin amorphous carbon (aC)-film is applied, whose thickness is adjusted to induce a well-defined phase shift between unscattered and scattered electrons. However, the illumination with high-energy electrons initiates an irreversible degeneration of the aC-film, which causes electrostatic charging and affects the phase-shifting properties. Taking even advantage of charging, hole-free PPs were recently developed [3,4]. Electrostatic charging plays a central role in the application of thin-film PPs. However, the mechanisms of charging are not well-understood. This work shows that charging is dominated by secondary electron emission. For this purpose, Hilbert PPs were fabricated from different materials to study their charging behavior under electron beam illumination. Besides aC-films, thin films of the metallic glass alloy Pd77.5Cu6.0Si16.5 (PCS) were used for PP fabrication. The PCS-alloy is characterized by an amorphous structure and a high electrical conductivity, which is three orders of magnitude higher than that of aC [5,6]. Moreover, the PCS-alloy exhibits a strong resistance towards oxidation, which suggests less charging of PCS-films.
关键词： transmission electron microscopy,thin-film,secondary electron emission,charging,phase plates
更新于2025-11-21 11:20:48
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Influence of RbF post deposition treatment on heterojunction and grain boundaries in high efficient (21.1%) Cu(In,Ga)Se2 solar cells
摘要： Post deposition treatments (PDT) by alkali fluorides applied to chalcopyrite-based absorbers have produced record efficiencies in thin-film solar devices in the past few years and recently the efficiency of 22.6 % was achieved with Cu(In,Ga)Se2 (CIGS) using rubidium fluoride (RbF) PDT. However, the effects of RbF-PDT towards changes in its interfacial and grain boundary (GB) properties are still not fully understood. In this work, cells with efficiency higher than 21% are investigated by combination of atom probe tomography (APT) and transmission electron microscopy (TEM) to show how changes in GB and interface chemistry may facilitate high efficiencies. APT studies, carried out at the interface between CIGS absorber and solution-grown CdS buffer layer, show In enrichment and Cu depletion along with traces of Rb. Our APT studies reveal higher amounts of Rb (1.5 at. %) and lower amounts of Na and K (<0.5 at. %) at GBs as compared with previous studies (on non-PDT samples) thus indicating substitution of Na and K by Rb. However, concentration of all alkali elements inside the grain bulk is below detection limit of APT. The concentration of Rb at the GBs in CIGS is measured depth-dependent using both APT and TEM, which consistently shows the increase in Rb towards the Mo back contact. In addition, a pronounced Cu depletion is observed at the GBs which might enhance hole-barrier properties of the GBs, thus improving charge carrier collection and hence the overall efficiency of the device. Thus, understanding effects of RbF-PDT at the atomic scale provides new insights concerning the further improvement of CIGS absorber and interfaces.
关键词： Cu(In,Ga)Se2,Thin-film solar cell,heterojunction,atom probe tomography,post deposition treatments,transmission electron microscopy
更新于2025-11-21 11:20:48
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Vancomycin functionalized WO3 thin film-based impedance sensor for efficient capture and highly selective detection of Gram-positive bacteria
摘要： In this study, we report a facile, reusable, and highly sensitive label-free impedance sensor for discriminating Gram-positive and Gram-negative bacteria. The impedance sensor was fabricated using gold interdigitated electrodes onto a tungsten oxide thin film. X-Ray diffraction confirmed the formation of polycrystalline tungsten oxide. Field emission scanning electron microscopy and atomic force microscopy revealed that tungsten oxide has a porous structure. Tungsten oxide was functionalized with vancomycin, a glycopeptide antibiotic known to have a specific interaction with the peptidoglycan layer of Gram-positive bacteria. fourier transform infrared microscopy and scanning electron microscopy were employed to test the morphological coating of vancomycin on interdigitated electrodes/ tungsten oxide sensor. The functionalized tungsten oxide sensor was highly efficient in the capture of Gram-positive bacteria. The impedance measurement was also sensitive to differentiate between viable and non-viable Gram-positive bacteria. Limit of detection 102 colony forming unit/ml, linear dynamic range 102 - 107 colony forming unit/ml under physiological conditions and reusable nature of this vancomycin coated impedance sensor provide a label-free strategy for quick, sensitive and highly selective detection of Gram-positive bacteria.
关键词： Vancomycin,WO3 thin film,Gram-positive bacteria,Impedance sensor
更新于2025-11-21 11:18:25
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Plasmon-enhanced upconversion luminescence in pyrochlore phase Yb<sub>x</sub>Er<sub>2-x</sub>Ti<sub>2</sub>O<sub>7</sub> thin film
摘要： Pyrochlore phase YbxEr2-xTi2O7 (YETO) thin films have been prepared by employing a facile sol-gel method combining with spin-coating technique and post-annealing treatment at 700 ℃. High concentration of Yb3+ ions can promote the transformation from Yb3+/Er3+ co-doped anatase phase TiO2 to pyrochlore phase YETO at 700 ℃ temperature. We find that the YETO thin film with 30 mol% Yb3+ ions exhibits the brightest upconversion (UC) emission. Moreover, introduction of Au nanorods (Au NRs) in the YETO thin film can further enhance the UC fluorescence. By adjusting the density of Au NRs, the UC emission intensity is increased by about 2.8-fold due to the excitation field enhancement caused by the localized surface plasmon resonance effect.
关键词： YbxEr2-xTi2O7,Thin film,Plasmon,Upconversion
更新于2025-11-21 11:01:37
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Highly sensitive and selective room-temperature NO2 gas-sensing characteristics of SnOX-based p-type thin-film transistor
摘要： The high-performance p-type metal-oxide-semiconductor (MOS)-based gas sensor is an important subject of research in the field of gas-sensing technology. In this work, we demonstrated a p-type MOS-based thin-film transistor (TFT) nitrogen dioxide (NO2) gas sensor that used tin oxide (SnOX) for both the channel and sensing layers. The crystalline status, surface morphology, and atomic-bonding configuration of the thin-film were examined using X-ray diffraction, field emission-scanning electron microscopy, and X-ray photoelectron spectroscopy. The results indicated that the deposited thin-film was mainly composed of polycrystalline SnO with a tetragonal structure. The fabricated p-type SnOX TFT showed a maximum response value of 19.4-10 ppm NO2 at room temperature (RT, 25 °C) when operated in the subthreshold region, which was significantly higher than that of 2.8–10 ppm NO2 obtained from a p-type SnOX thin-film chemiresistor at RT. In addition, the SnOX TFT gas sensor showed significantly higher sensitivity to NO2 gas than to other target gases such as NH3, H2S, CO2, and CO at RT. To the best of our knowledge, this is the first study to a p-type MOS-based field-effect transistor-type gas sensor. Our experimental results demonstrate that the p-type SnOX TFT is a promising gas sensor that can operate at RT with high sensitivity and selectivity to NO2 gas.
关键词： SnO,Thin-film transistor,NO2 gas sensing,SnOX,P-type metal oxide semiconductor
更新于2025-11-21 11:01:37
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Plasmonic Metasurfaces with Tunable Gap and Collective SPR Modes
摘要： Optical properties of a plasmonic metasurface made of a monolayer of gold nanoparticles in close proximity to an aluminum thin film were studied numerically and experimentally. Extinction spectra of the plasmonic metasurface were studied as functions of the thickness of a dielectric spacer between the monolayer of gold nanoparticles and the aluminum film in the visible wavelength range. The goal was to understand the excitation of a collective surface plasmon resonance (SPR) mode and a gap plasmon mode as well as their dependence on the spacer thickness, nanoparticles spacing and their size. By using finite-difference-time-domain (FDTD) calculations we find that the SPR extinction peak first red-shifts and then splits into two peaks. The first extinction peak is associated with the collective SPR mode of the monolayer and it shifts to shorter wavelengths as the spacer layer decreases. As the spacer layer decreases from 35 nm to 7.5 nm, the second peak gradually appears in the extinction spectra of the metasurface. We assign the second peak to the gap mode. The gap mode first appears at around 620 nm or greater and it shifts to larger wavelength for larger nanoparticle spacing and size. The FDTD simulations are confirmed by an experimental examination of the dispersion curves of a similar multilayer system. The computational results match the experimental results and confirm the excitation of the two modes.
关键词： gap plasmon mode,surface plasmon resonance,Plasmonic metasurfaces,aluminum thin film,FDTD,gold nanoparticles
更新于2025-11-19 16:56:42
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Preparation of La<sub>0.9</sub>Sr<sub>0.1</sub>Ga<sub>0.8</sub>Mg<sub>0.2</sub>O<sub>3</sub> Film by Pulse Laser Deposition (PLD) Method on Porous Ni–Fe Metal Substrate for CO<sub>2</sub> Electrolysis
摘要： Preparation of metal supported La0.9Sr0.1Ga0.8Mg0.2O3 (LSGM) thin film cell for CO2 electrolysis was studied and by using selective reduction method of NiO–NiFe2O4, it was found that porous Ni–Fe(9:1) based substrate with ca.30% porosity was successfully prepared without large volume change resulting in the successful preparation of LaGaO3 dense thin film on metal substrate. By using Ce0.8Sm0.2O2 (SDC) thin film, Ni diffusion from Ni–Fe substrate was prevented. CO2 electrolysis was performed on the prepared LSGM/SDC on Ni–Fe porous substrate. When Sm0.5Sr0.5CoO3 (SSC) anode was prepared by screen print method using SSC powder, sintering of SSC powder was significantly occurred resulting in the large IR loss and overpotential. In contrast, when SSC anode layer was deposited by PLD (30 min) after LSGM/SDC layer deposition, tight contact between SSC anode and LSGM electrolyte film was obtained and the large CO2 electrolysis current of 3 and 0.5 A/cm2 were achieved at 973 and 773 K, respectively. Impedance analysis suggests that increased CO2 electrolysis current was obtained by decreased IR loss and electrode overpotential.
关键词： LaGaO3 thin film,CO2 electrolysis,metal support,solid oxide electrolysis cell
更新于2025-11-19 16:51:07
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RbF post deposition treatment for narrow bandgap Cu(In,Ga)Se2 solar cells
摘要： Multi-junction solar cells are known to have a considerably increased efficiency potential over their typical single junction counterparts. In order to produce low cost and lightweight multi-junction devices, the availability of suitable narrow (<1.1 eV) bandgap bottom cells is paramount. A possible absorber for such a bottom cell is the Cu(In,Ga)Se2 (CIGS) compound semiconductor, one of the most efficient thin film materials to date. In this contribution we report on the RbF post deposition treatment of narrow bandgap CIGS absorbers grown with a single bandgap grading approach. We discuss the necessary deposition conditions and the observed improvements on solar cells performance. A certified record efficiency of 18.0 % for an absorber with 1.00 eV optoelectronic bandgap is presented and its suitability for perovskite/CIGS tandem devices is shown.
关键词： Post deposition treatment,Narrow bandgap,Tandem solar cells,Thin film solar cells,photovoltaics,Rubidium fluoride,Copper indium gallium selenide
更新于2025-11-14 17:28:48