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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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Alignment of liquid crystals using Langmuir?Blodgett films of unsymmetrical bent-core liquid crystals
摘要： The properties of the thin films of liquid crystal (LC) molecules can be governed easily by external fields. The anisotropic structure of the LC molecules has a large impact on the electrical and optical properties of the film. The Langmuir monolayer (LM) of LC molecules at the air–water interface is known to exhibit a variety of surface phases which can be transferred onto a solid substrate using the Langmuir?Blodgett (LB) technique. Here, we have studied the LM and LB films of asymmetrically substituted bent-core LC molecules. The morphology of LB film of the molecules is found to be a controlling parameter for aligning bulk LC in the nematic phase. It was found that the LB films of the bent-core molecules possessing defects favour the planar orientation of nematic LC, whereas the LB films with fewer defects show homeotropic alignment. The defect in LB films may introduce splay or bend distortions in the nematic near the alignment layer which can govern the planar alignment of the bulk LC. The uniform layer of LB film facilitates the molecules of nematic to anchor vertically due to a strong van der Waals interaction between the aliphatic chains leading to a homeotropic alignment.
关键词： field emission scanning electron microscope,atomic force microscope,Langmuir?Blodgett film,liquid crystals,Brewster angle microscopy,Langmuir monolayer
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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Three-dimensional Nanoscale Mapping of Porosity in Solution-Processed ITO Multilayer Thin Films for Patternable Transparent Electrodes
摘要： Indium tin oxide (ITO) films constitute components of many layered heterostructures used for emergent technologies beyond conventional optoelectronics. Compositional and morphological changes have a direct impact on the device’s performance. Hence control over the morphology with advanced multimodal characterization approaches are required to evaluate the devices. Herein multilayer ITO films deposited by spin coating were quantified in nanoscale detail in three dimensions by combining results from depth-sensitive neutron reflectometry (NR), non-contact topographic AFM images and cross-sectional SEM images. Films with different number of deposited layers were visually transparent even though the topmost layer was as high as 60% porous, with porosity gradually decreasing as the number of the underneath sublayers increased. Surface and interfacial roughness through the total film and individual layer thickness were obtained. NR data also furnished quantitative depth information on the films chemical composition and layer-by-layer bulk density, which has never been obtained before, providing a way to monitor and ultimately control the sheet resistivity via the pore network. When the same formulation is used for inkjet printing patterns, the larger pores disappear and the optical properties are improved to >90% transmittance at all visible wavelengths. All 5L films achieved sheet resistivities as low as 10-2 ?-cm and can therefore be used as patternable transparent electrodes for many devices including liquid crystal displays.
关键词： thin multilayer film,neutron reflectometry,depth density distribution,neutron absorption reflectometry,Indium tin oxide,porosity,structure chemical depth profile,off-specular neutron scattering,layer by layer deposition
更新于2025-11-19 16:56:35
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TiO2/SnO2 and SnO2/TiO2 heterostructures as photocatalysts for degradation of stearic acid and methylene blue under UV irradiation
摘要： The effect TiO2/SnO2 (TiO2 is on the top and SnO2 at the bottom) and SnO2/TiO2 (SnO2 is on the top and TiO2 at the bottom) heterostructures towards photocatalytic degradation of stearic acid and methylene blue is reported. The two heterostructures, wherein SnO2 (or TiO2) is the top or bottom layer, are prepared by the sol-gel technique. TiO2/SnO2 film exhibit better photocatalytic activity as compared to SnO2/TiO2, TiO2 and SnO2 films. Wettability studies reveal that TiO2/SnO2 films modified with stearic acid (8mM concentration of stearic acid in ethyl alcohol) tend towards superhydrophobic regime with contact angle as high as 137o. Further, TiO2/SnO2 films are efficient in degrading the stearic acid under UV irradiation. Interestingly, TiO2/SnO2 films that display flake like structures, with increased charge separation, are responsible for better degradation of pollutants under UV irradiation because of coupling heterostructures.
关键词： Bilayer film,Wettability,Superhydrophobic,Photocatalytic activity
更新于2025-11-19 16:56:35
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Deposition of gold nanoparticles upon bare and indium tin oxide film coated glass based on annealing process
摘要： We presented a simple and efficient strategy for deposition of gold nanoparticles (AuNPs) upon transparent bare and indium tin oxide (ITO) film coated glass substrate using gold colloids as Au sources. The method involved two steps: embedding in polyvinyl alcohol (PVA) film and annealing at high temperature. The AuNPs deposited on solid substrate because of migration and coalescence of gold at high temperature. The optical and structural properties of the AuNPs were characterised by UV-vis absorption spectra and scanning electron microscopy. The results indicate that the surface of AuNPs upon substrate was clean as annealing at 600 °C for 0.5 h. The size of AuNPs deposited on ITO glass increased with annealing time and volume of PVA-AuNPs. Meanwhile, the localised surface plasmon resonance peak of AuNPs deposited on substrate was also gradual red-shift. In addition, the size of AuNPs deposited on ITO substrate was larger than that on bare glass. This work provides a simple, low-cost and large-scale method for fabrication of substrate-based AuNPs, which is benefit for exploiting biosensors, photonic devices and optoelectronic devices.
关键词： thermal annealing,solid substrate,Gold nanoparticles,indium tin oxide film coated glass
更新于2025-11-19 16:56:35
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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
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Thinning ferroelectric films for high-efficiency photovoltaics based on the Schottky barrier effect
摘要： Achieving high power conversion efficiencies (PCEs) in ferroelectric photovoltaics (PVs) is a longstanding challenge. Although recently ferroelectric thick films, composite films, and bulk crystals have all been demonstrated to exhibit PCEs >1%, these systems still suffer from severe recombination because of the fundamentally low conductivities of ferroelectrics. Further improvement of PCEs may therefore rely on thickness reduction if the reduced recombination could overcompensate for the loss in light absorption. Here, a PCE of up to 2.49% (under 365-nm ultraviolet illumination) was demonstrated in a 12-nm Pb(Zr0.2Ti0.8)O3 (PZT) ultrathin film. The strategy to realize such a high PCE consists of reducing the film thickness to be comparable with the depletion width, which can simultaneously suppress recombination and lower the series resistance. The basis of our strategy lies in the fact that the PV effect originates from the interfacial Schottky barriers, which is revealed by measuring and modeling the thickness-dependent PV characteristics. In addition, the Schottky barrier parameters (particularly the depletion width) are evaluated by investigating the thickness-dependent ferroelectric, dielectric and conduction properties. Our study therefore provides an effective strategy to obtain high-efficiency ferroelectric PVs and demonstrates the great potential of ferroelectrics for use in ultrathin-film PV devices.
关键词： power conversion efficiency,Schottky barrier effect,ferroelectric photovoltaics,PZT ultrathin film,depletion width
更新于2025-11-14 17:28:48
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Pyrene-SH functionalized OTFT for detection of Hg2+ ions in aquatic environments
摘要： Mercury ion (Hg2+) sensor based on bottom gate top contact organic thin film transistor (OTFT) was fabricated. The OTFT channel area was functionalized with pyrene that contain thiol group, which has strong binding affinity toward Hg2+ ion. The OTFT sensor exhibited a charge mobility of 0.28 cm2 V–1 s–1, a threshold voltage of -22.3 V and on-to-off ratio 103. The sensor shows high selectivity to Hg2+ ion over other two valence metal ions. OTFT sensor exhibited high sensitivity to Hg2+ ion, indicated by increasing of drain current after exposed to different concentration of Hg2+ ion ranging from 1 mM to 0.01 μM. Moreover, the OTFT sensor capability for practical application was also demonstrated by sensing the present of 25 μM of Hg2+ ion in tap, drinking and seawater samples.
关键词： Mercury sensor,Pyrene derivative,Organic thin film transistor
更新于2025-11-14 17:28:48