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Lossy Mode Resonance Generation by Graphene Oxide Coatings onto Cladding-Removed Multimode Optical Fiber
摘要： In this work, we have studied the suitability of graphene oxide-based thin films to be not only excellent sensitive coatings but also lossy mode resonance (LMR)-generating materials. Thin films of graphene oxide (GO) and polyethylenimine (PEI) fabricated by means of layer-by-layer assembly were selected in this study. Two optical fiber devices with 8 and 20 bilayers of the LMR-generating coating were fabricated and characterized as refractometers. Both devices show no hysteresis and high sensitivity, improving previously reported values. This research opens very promising and exciting possibilities in the field of optical fiber sensors based on LMR, strategically including specific recognition groups to the device surface to exploit this high sensitivity for monitoring a range of target analytes. The carboxylate functional groups at the edges of the GO sheets should provide excellent attachment sites for the required coupling chemistry to realize such devices.
关键词： optical fiber sensor,thin films,Dip-assisted layer by layer,lossy mode resonance,refractometer,graphene oxide
更新于2025-11-14 15:19:41
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Dependence of Mechanical Stresses in Silicon Nitride Films on the Mode of Plasma-Enhanced Chemical Vapor Deposition
摘要： Films of silicon nitride SiNx, obtained by plasma-enhanced chemical vapor deposition from the monosilane SiH4 and ammonia NH3 gases, are widely used in microelectronics and micro- and nanoelectromechanical systems. Residual mechanical stresses and film composition are important characteristics for many applications. The properties of SiNx films, particularly mechanical stresses and composition, depend largely on the conditions of production, e.g., the ratio of the reacting gas flow rates, the composition of the gas mixture, the power and frequency of the plasma generator, and the temperature and pressure during deposition. Despite the great volume of works on the subject, data regarding the dependence of the properties and composition of SiNx films on the conditions of production remain sparse. This work considers the effect the ratio of the reacting gas flow rates has on the mechanical stresses and composition of silicon nitride films SiNx obtained by plasma-enhanced chemical vapor deposition from gaseous mixtures of SiH4 monosilane and NH3 ammonia using low-frequency plasma. It is found that when the ratio of the gas flow rates of SiH4 and NH3 is raised from 0.016 to 0.25, the compressive mechanical stresses are reduced by 31%, the stoichiometric coefficient falls from 1.40 to 1.20, the refractive index rises from 1.91 to 2.08, the concentration of N–H bonds is reduced by a factor of 7.4, the concentration of Si–H bonds grows by a factor of 8.7, and the concentration of hydrogen atoms is reduced by a factor of 1.5. These results can be used for the controlled production of SiNx films with such specified characteristics as residual mechanical stresses, refractive index, stoichiometric coefficient, and the concentration of hydrogen-containing bonds.
关键词： mechanical stresses,optical profilometry,films of PECVD silicon nitride SiNx,IR Fourier spectroscopy
更新于2025-11-14 15:18:02
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Revealing the correlation between molecular structure and dielectric properties of carbonyl‐containing polyimide dielectrics
摘要： Polymer dielectrics with outstanding heat resistance and advanced dielectric properties are of great importance for high-temperature capacitors in the applications of hostile circumstances. In this work, a series of aromatic carbonyl-containing polyimides (CPI) are prepared from the carbonyl dianhydride and different diamines. The correlation between molecular structure (i.e., different linked structure ( O , CH2 , SO2 ) in diamines, the length of repeating unit and the linked position (para-para or meta-meta), and properties is revealed in detail to obtain CPI dielectrics with excellent thermal resistance (glass transition temperature, Tg: 241~352°C), reasonably high dielectric constant (3.99~5.23), low dissipation factor (0.00307~0.00395), and admirable breakdown strength (425~552 MV/m) simultaneously. Particularly, CPI-5 with carbonyl structure in dianhydride and sulfonyl group in diamine proves to exhibit discharged energy density and charge–discharge efficiency of 6.34 J/cm3 and 92.3% at 500 MV/m, respectively. In addition, CPI-5 also displays stable dielectric properties in temperature range of ?50?200°C. ? 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47883.
关键词： dielectric properties,films,thermal properties,polyimides
更新于2025-11-14 14:48:53
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Single process CVD growth of hBN/Graphene heterostructures on copper thin films
摘要： In this study, we have successfully grown hBN/graphene heterostructures on copper thin films using chemical vapor deposition in a single process. The first and most surprising result is that graphene grows underneath hBN and adjacent to the Cu film even though it is deposited second. This was determined from cross-sectional TEM analysis and XPS depth profiling, which chemically identified the relative positions of hBN and graphene. The effect of various growth conditions on graphene/hBN heterostructures was also studied. It was found that a pressure of 200 torr and a hydrogen flow rate of 200 sccm (;1 H2/N2) yielded the highest quality of graphene, with full surface coverage occurring after a growth time of 120 min. The resulting graphene films were found to be approximately 6–8 layers thick. The grain size of the nanocrystalline graphene was found to be 15–50 nm varying based on growth conditions.
关键词： XPS depth profiling,copper thin films,TEM analysis,hBN/graphene heterostructures,chemical vapor deposition
更新于2025-11-14 14:32:36
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Self-Assembled Ordered Three-Phase Au-BaTiO <sub/>3</sub> -ZnO Vertically Aligned Nanocomposites Achieved by a Templating Method
摘要： Complex multiphase nanocomposite designs present enormous opportunities for developing next-generation integrated photonic and electronic devices. Here, a unique three-phase nanostructure combining a ferroelectric BaTiO3, a wide-bandgap semiconductor of ZnO, and a plasmonic metal of Au toward multifunctionalities is demonstrated. By a novel two-step templated growth, a highly ordered Au–BaTiO3–ZnO nanocomposite in a unique “nanoman”-like form, i.e., self-assembled ZnO nanopillars and Au nanopillars in a BaTiO3 matrix, is realized, and is very different from the random three-phase ones with randomly arranged Au nanoparticles and ZnO nanopillars in the BaTiO3 matrix. The ordered three-phase “nanoman”-like structure provides unique functionalities such as obvious hyperbolic dispersion in the visible and near-infrared regime enabled by the highly anisotropic nanostructures compared to other random structures. Such a self-assembled and ordered three-phase nanocomposite is obtained through a combination of vapor–liquid–solid (VLS) and two-phase epitaxy growth mechanisms. The study opens up new possibilities in the design, growth, and application of multiphase structures and provides a new approach to engineer the ordering of complex nanocomposite systems with unprecedented control over electron–light–matter interactions at the nanoscale.
关键词： vertically aligned nanocomposites,plasmonics,epitaxial thin films,metamaterials,three-phase nanocomposites,self-assembly
更新于2025-10-22 19:40:53
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AlN-based hybrid thin films with self-assembled plasmonic Au and Ag nanoinclusions
摘要： Aluminum nitride (AlN)-based two-phase nanocomposite thin films with plasmonic Au and Ag nanoinclusions have been demonstrated using a one-step thin film growth method. Such AlN-based nanocomposites, while maintaining their wide bandgap semiconductor behavior, present tunable optical properties such as bandgap, plasmonic resonance, and complex dielectric function. Depending on the growth atmosphere, the metallic nanoinclusions self-organized into different geometries, such as nano-dendrites, nano-disks, and nanoparticles, providing enhanced optical anisotropy in-plane and out-of-plane. The infrared transmission measurements demonstrate the signature peaks of AlN as well as a broad transmission window attributed to the plasmonic nanoinclusions. This unique AlN-metal hybrid thin film platform provides a route to modulate the optical response of wide bandgap III-V nitride semiconductors towards infrared sensing or all optical based integrated circuits.
关键词： plasmonic Au and Ag nanoinclusions,infrared sensing,integrated circuits,AlN-based hybrid thin films,optical properties
更新于2025-10-22 19:40:53
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Structural, electronic and optical properties of pulsed laser deposited Cu2SnS3 photo absorber thin films: A combined experimental and computational study
摘要： Pulsed laser deposited thin films of Cu2SnS3 (CTS) are characterized for the structural, electronic and optical properties using X-ray diffraction, Raman, UV–Vis-NIR spectroscopy, scanning electron microscopic techniques, and density functional theory. It is observed that thin-film samples annealed at low temperature have a metastable tetragonal structure, whereas the films annealed at 450 °C have a predominant stable monoclinic phase. A direct band gap of 1.1 eV, measured from the transmittance spectra, in close agreement with the theoretical band gap value of 0.89 eV obtained from density functional theory calculations. Optical properties reveal that CTS has a large absorption coefficient ~0.5 × 104 cm?1 at 1.5 eV which is comparable to other CuS based materials like CuInS2 and Cu2ZnSnS4. The direct band gap and large absorption coefficient make CTS as one of the potential alternative absorber materials for thin-film solar cell applications.
关键词： Annealing,Raman spectroscopy,Thin films,Density functional theory,Pulsed laser deposition,Optical properties
更新于2025-10-22 19:40:53
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Nanostructured Transparent Conductive Electrodes for Applications in Harsh Environments Fabricated via Nanosecond Laser‐Induced Periodic Surface Structures (LIPSS) in Indium–Tin Oxide Films on Glass
摘要： A self-organization phenomenon named laser-induced periodic surface structures (LIPSS) is utilized for pattern formation in indium–tin oxide (ITO) transparent conductive films coated on borosilicate glass. Stripe patterns with periodicities down to 175 nm are created by scanning the focused beam (30 μm spot diameter 1 e?2) of a nanosecond pulsed laser operating at 532 nm wavelength over ITO films. Highly ordered ITO-LIPSS are generated at a pulse duration of 6 ns, pulse frequencies between 100 and 200 kHz, pulse energies around 20 μJ, and laser spot scan speeds in the range of 50–80 mm s?1. Resulting nanopatterns are electrically conductive and feature improved optical transparency as well as stability against strong acids such as hydrochloric acid, sulfuric acid, and even aqua regia. The formation of mixed phases between ITO and silicon is considered to be the origin for the chemical robustness of laser patterned transparent conductive electrodes.
关键词： laser-induced periodic surface structures (LIPSS),laser patterning,self-organization,indium–tin oxide (ITO),transparent conductive films (TCF)
更新于2025-10-22 19:40:53
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Tuning of the Optical Properties of the Transparent Conducting Oxide SrVO <sub/>3</sub> by Electronic Correlations
摘要： The vanadate SrVO3 is a transparent conductor perovskite with optical and electrical properties competing with those of the most-used indium tin oxide material. Although its charge density is comparable to that of metals, SrVO3 shows a plasma frequency below the visible range due to strong electronic correlations characterizing the electronic transport in this material and enhancing the effective mass. Therefore, the well-known interplay between the structure and the electronic properties of strongly correlated systems can be used in such transparent conductor to tune the optical properties, as the plasma frequency also depends on the effective mass. In this study, SrVO3 films are grown by pulsed laser deposition onto different lattice mismatched perovskite substrates such as SrTiO3, LaAlO3, and (LaAlO3)0.3(Sr2TaAlO6)0.7 at different growth temperatures. The structural, electronic, and optical properties are analyzed, illustrating the influence of the strain on the structure of the films and on a shift of the plasma frequency. The electronic correlations in this new group of transparent conducting oxides can be therefore used as a supplementary lever for the tuning of the functional properties.
关键词： transparent conducting oxides,vanadates,thin films,correlated materials,epitaxy
更新于2025-10-22 19:40:53
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Layer-by-layer MoS2:GO composite thin films for optoelectronics device applications
摘要： With reference of our previous report (Appl. Surf. Sci. 2018, ASAP), the molybdenum disulphide (MoS2) thin film were prepared by the dip-coating technique at different temperatures (4000C – 4500C) using methanolic solution of ammonium molybdate and ammonium thiocyanate that are used as bare-substrate for the deposition of graphene oxide (GO) thin films. For the deposition of graphene oxide (GO), commercially purchased GO (0.5 mg in 10 mL aqueous solution) was deposited by dip-coating technique on dip-deposited MoS2 thin film to make layer-by-layer MoS2:GO composite thin films and hence studied their electronic and electrical behaviours. The micro-structural and surface morphology were studied using Raman spectroscopy and field emission scanning electron microscopy, whereas optical band estimated from the optical absorption spectra. The electronic structure and their bonding properties were studied using x-ray photoelectron spectroscopy and the electrical behaviours were observed from the current-voltage (I-V) characteristic curve. The formation of different phases of MoS:GO thin films show an enhanced electronic and electrical performance due to their unique-structure and the synergetic effect of MoS2:GO nanosheets when compared to those of bare MoS2.
关键词： XPS Spectroscopy,Layer-by-layer MoS2:GO composite thin films,I-V curve
更新于2025-10-22 19:40:53