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[IEEE 2019 IEEE SENSORS - Montreal, QC, Canada (2019.10.27-2019.10.30)] 2019 IEEE SENSORS - Room temperature gas sensors based on laser-annealed ZnO nanostructures for gaseous pollutants detection
摘要： To effectively control gaseous pollutants in air it is mandatory to fabricate reliable and non-expensive monitoring systems that can be easily deployed in urban areas. Sensing devices based on metal oxide nanostructures offer many advantages respect bulk material in detecting multiple hazardous gases such as, high stability, easy surface functionalization and temperature. Among diverse potentially nanostructures, ZnO nanorods can be obtained with low cost and simple process at a low manufacturing temperature opening the possibility to integrate the material with flexible substrates. Additionally, laser annealing procedure can be exploited to improve or tune the morphology and the electrical properties of these materials. In this work, we present a comparison between the performance of as deposited and laser-annealed devices in the detection of NO and NO2. Different sensors characteristics at increasing gas concentrations and dynamic behaviors are shown and discussed evaluating the mechanisms involved in the diverse pollutant detection. As result, the laser-annealed sensor exhibits a sensitivity one-order higher respect to as-grown sample in detecting NO (3.9x10-3 vs 2.7x10-4 [1/ppm]) while for NO2 sensitivity is more than four times higher (3.8x10-3 vs 8.4x10-4 [1/ppm]).
关键词： ZnO nanostructures,gaseous pollutants,room temperature gas sensing,laser annealing
更新于2025-09-16 10:30:52
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Enhancing Quantum Yield in Strained MoS2 Bilayers by Morphology-controlled Plasmonic Nanostructures towards Superior Photodetectors
摘要： Recently, extracting hot electrons from plasmonic nanostructures and utilizing them to enhance the optical quantum yield of 2D transition-metal dichalcogenides (TMDs) have been topics of interest in the field of optoelectronic device applications, such as solar cells, light emitting diodes, photodetectors and so on. The coupling of plasmonic nanostructures with nanolayers of TMDs depends on the optical properties of the plasmonic materials, including radiation pattern, resonance strength, and hot electron injection efficiency. Herein, we demonstrate the augmented photodetection of a large-scale, transfer-free bilayer MoS2, by decorating this TMD with four different morphology-controlled plasmonic nanoparticles. This approach allows engineering the bandgap of the bilayer MoS2 due to localized strain that stems up from plasmonic nanoparticles. In particular, the plasmonic strain blue shifts the band gap of bilayer MoS2 with 32 times enhanced photoresponse demonstrating immense hot electron injection. Besides, we observed the varied photoresponse of MoS2 bilayer hybridized with different morphology controlled plasmonic nanostructures. Although, hot electron injection was a substantial factor for photocurrent enhancement in hybrid plasmonic-semiconductor devices, our investigations further show that other key factors such as highly directional plasmonic modes, high aspect-ratio plasmonic nanostructures and plasmonic strain induced beneficial band-structure modifications were crucial parameters for effective coupling of plasmons with excitons. As a result, our study sheds light on designing highly tailorable plasmonic nanoparticles integrated transition metal dichalcogenide-based optoelectronic devices.
关键词： Plasmonic Nanostructures,Strained MoS2 Bilayers,Quantum Yield,Photodetectors
更新于2025-09-16 10:30:52
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Solar Cell Using Hourglass-Shaped Silicon Nanowires for Increased Light-Trapping Path
摘要： Silicon nanowires (SiNWs) are promising structures with excellent photovoltaic properties for low-cost, high-efficiency solar cells and have the potential to overcome the limits of bulk silicon solar cells. There is still a need to enhance light absorption in SiNWs without increasing the surface area. Here, we introduce a novel design, hourglass-shaped silicon nanowire (HG-SiNW) to significantly increase the light-trapping path. Electrical and optical measurements show the superiority of HG-SiNW as an antireflective layer. In addition, whispering gallery mode identified by optical simulations accounts for the greatly improved absorption at the broadband solar spectrum. The HG-SiNW solar cells show an increase in short-circuit current (JSC) and 1.85 times higher efficiency with only simple diameter variations.
关键词： light absorption,Antireflection,silicon (Si) nanostructures,photovoltaics (PVs),whispering gallery mode (WGM)
更新于2025-09-16 10:30:52
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Plasmonic and nonlinear optical behavior of nanostructures in glass matrix for photonics application
摘要： There is a growing interest in bimetallic core shell nanostructures that comprised out of noble metals due to their fascinating plasmonic properties, leading to a wide range of applications in future nanotechnology. Here we report on Ag/Cu core shell nanostructures in a glass matrix. It includes novel approaches for characterizing embedded core shell nanostructures with a detailed study on the nanosize effect in tuning their optical and nonlinear optical properties along with biomedical applications. Annealing the Ag/Cu as- exchanged samples resulted in the formation of core-shell nanostructures, which were confirmed using UV–vis absorption spectroscopy and high-resolution transmission electron microscopy. The prepared plasmonic nanostructures were further studied using X-ray diffraction, Rutherford backscattering, photoluminescence, Raman, X-ray photoelectron spectroscopy and Z scan techniques. The nonlinear optical properties of the glasses containing bimetallic nanoparticles have been studied at a non-resonant wavelength using femtosecond laser pulses and a possible mechanism for the observed nonlinearity have been explained.
关键词： Soda-lime glass,Core-shell nanostructures,Surface plasmon resonance
更新于2025-09-16 10:30:52
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A review of 2D and 3D plasmonic nanostructure array patterns: fabrication, light management and sensing applications
摘要： This review article discusses progress in surface plasmon resonance (SPR) of two-dimensional (2D) and three-dimensional (3D) chip-based nanostructure array patterns. Recent advancements in fabrication techniques for nano-arrays have endowed researchers with tools to explore a material’s plasmonic optical properties. In this review, fabrication techniques including electron-beam lithography, focused-ion lithography, dip-pen lithography, laser interference lithography, nanosphere lithography, nanoimprint lithography, and anodic aluminum oxide (AAO) template-based lithography are introduced and discussed. Nano-arrays have gained increased attention because of their optical property dependency (light-matter interactions) on size, shape, and periodicity. In particular, nano-array architectures can be tailored to produce and tune plasmonic modes such as localized surface plasmon resonance (LSPR), surface plasmon polariton (SPP), extraordinary transmission, surface lattice resonance (SLR), Fano resonance, plasmonic whispering-gallery modes (WGMs), and plasmonic gap mode. Thus, light management (absorption, scattering, transmission, and guided wave propagation), as well as electromagnetic (EM) field enhancement, can be controlled by rational design and fabrication of plasmonic nano-arrays. Because of their optical properties, these plasmonic modes can be utilized for designing plasmonic sensors and surface-enhanced Raman scattering (SERS) sensors.
关键词： sensor,lithography,nanofabrication,nano-array,plasmon,surface-enhanced Raman scattering (SERS),nanostructures
更新于2025-09-16 10:30:52
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Strongly coupled, high-quality plasmonic dimer antennas fabricated using a sketch-and-peel technique
摘要： A combination of helium- and gallium-ion beam milling together with a fast and reliable sketch-and-peel technique is used to fabricate gold nanorod dimer antennas with an excellent quality factor and with gap distances of less than 6 nm. The high fabrication quality of the sketch-and-peel technique compared to a conventional ion beam milling technique is proven by polarisation-resolved linear dark-field spectromicroscopy of isolated dimer antennas. We demonstrate a strong coupling of the two antenna arms for both fabrication techniques, with a quality factor of more than 14, close to the theoretical limit, for the sketch-and-peel–produced antennas compared to only 6 for the conventional fabrication process. The obtained results on the strong coupling of the plasmonic dimer antennas are supported by finite-difference time-domain simulations of the light-dimer antenna interaction. The presented fabrication technique enables the rapid fabrication of large-scale plasmonic or dielectric nanostructures arrays and metasurfaces with single-digit nanometer scale milling accuracy.
关键词： helium-ion beam lithography,near-field enhancement,strong coupling,plasmonic nanostructures,sketch and peel,quality factor,single-particle dark-field spectroscopy
更新于2025-09-16 10:30:52
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Epitaxial Regrowth and Hole Shape Engineering for Photonic Crystal Surface Emitting Lasers (PCSELs)
摘要： In the present research, epitaxial regrowth by molecular beam epitaxy (MBE) is investigated as a fabrication process for void-semiconductor photonic crystal (PhC) surface emitting lasers (PCSELs). The PhC is patterned by electron beam lithography and inductively coupled plasma (ICP) etch and is subsequently regrown by molecular beam epitaxy to embed a series of voids in bulk semiconductor. Experiments are conducted to investigate the effects of regrowth on air-hole morphology. The resulting voids have a distinct teardrop shape with the radius and depth of the etched hole playing a very critical role in the final regrown void’s dimensions. We demonstrate that specific hole diameters can encourage deposition to the bottom of the voids or to their sidewalls, thus allowing us to engineer the shape of the void more precisely as is required by the PCSEL design. A 980 nm InGaAs quantum well laser structure is optimized for low threshold lasing at the design wavelength and full device structures are patterned and regrown. An optically pumped PCSEL is demonstrated from this process.
关键词： B3. Laser diodes,A3. Molecular Beam Epitaxy,A1. Nanostructures,B2. Semiconducting gallium arsenide
更新于2025-09-16 10:30:52
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Tunable Optical Properties in Self‐Assembled Oxide‐Metal Hybrid Thin Films via Au‐Phase Geometry Control: From Nanopillars to Nanodisks
摘要： Plasmonic oxide-metal hybrid nanostructures exhibit unprecedented optical properties because of the nanoscale interactions between the oxide and metal components. Precise control of the geometry and arrangement of optical building blocks is key to tailoring system properties toward various nanophotonic applications. Herein, self-assembled BaTiO3-Au vertically aligned nanocomposite thin films with a series of thicknesses are fabricated using a one-step pulsed laser deposition technique. By reducing the film thickness, the geometry of Au phase is effectively tailored from nanopillars to nanodisks, with the aspect ratio (height/width) varied from ≈4.0 to ≈1.0. The experimental optical spectra and numerical simulation results demonstrate that localized surface plasmon resonance and hyperbolic dispersion wavelength can be effectively tuned in the visible to near-infrared regime by varying the film thickness due to the change of Au aspect ratio and free electron density. This study demonstrates a feasible approach in tuning the optical responses in hybrid oxide-metal nanostructures, and opens up enormous possibilities in design and fabrication of novel optical components toward all optical integrated devices.
关键词： tunability,hybrid nanostructures,plasmonic Au nanostructures,localized surface plasmon resonance,hyperbolic dispersion
更新于2025-09-12 10:27:22
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Plasmonic Metamaterials for Nanochemistry and Sensing
摘要： Plasmonic nanostructures were initially developed for sensing and nanophotonic applications but, recently, have shown great promise in chemistry, optoelectronics, and nonlinear optics. While smooth plasmonic films, supporting surface plasmon polaritons, and individual nanostructures, featuring localized surface plasmons, are easy to fabricate and use, the assemblies of nanostructures in optical antennas and metamaterials provide many additional advantages related to the engineering of the mode structure (and thus, optical resonances in the given spectral range), field enhancement, and local density of optical states required to control electronic and photonic interactions. Focusing on two of the many applications of plasmonic metamaterials, in this Account, we review our work on the sensing and nanochemistry applications of metamaterials based on the assemblies of plasmonic nanorods under optical, as well as electronic interrogation.
关键词： field enhancement,sensing,localized surface plasmons,optical antennas,nanochemistry,optical resonances,electronic interrogation,surface plasmon polaritons,metamaterials,Plasmonic nanostructures
更新于2025-09-12 10:27:22
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Ion irradiation of III–V semiconductor surfaces: From self-assembled nanostructures to plasmonic crystals
摘要： Ion-irradiation of semiconductor surfaces has emerged as a promising approach to generate a variety of self-organized nanostructures. Furthermore, the combination of focused-ion-irradiation with molecular-beam epitaxy provides unprecedented design and control of surfaces and interfaces of hybrid materials at the atomic level during fabrication. In this review, we describe the directed self-assembly of nanostructure arrays ranging from islands to nanorods to 3-dimensional nanoparticle (NP) arrays. First, we discuss focused-ion-irradiation of III–V surfaces, which leads to preferential sputtering of group V species, followed by the formation of group III-rich metallic nanostructures. For continued irradiation beyond a threshold dose, the nanoparticle (NP) evolution is determined by the sputtering yield and the local ion beam angle of incidence, resulting in arrays of nanoparticles, nanorods, or nanoparticle chains. In addition to describing the formation of close-packed embedded Ga:GaAs nanocomposites using overgrowth of focused-ion-beam fabricated NP arrays, we discuss the surface plasmon resonances of NP arrays as well as the influence of both surface and buried NP arrays on the GaAs photoluminescence efficiency. Finally, we discuss the potential of “plasmonic crystals” for plasmon-enhanced optoelectronics.
关键词： self-assembled nanostructures,ion irradiation,plasmonic crystals,molecular-beam epitaxy,III-V semiconductor,nanoparticle arrays,surface plasmon resonances,photoluminescence efficiency,focused-ion-beam
更新于2025-09-12 10:27:22