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Ordered Array of Metal Particles on Semishell Separated with Ultrathin Oxide: Fabrication and SERS Properties
摘要： Metal particles in gap cavities provide an interesting system to achieve hybrid local surface plasmon modes for local field enhancement. Here, we demonstrate a relatively simple method to fabricate Ag nanoparticles positioned on Ag semishells separated by a thin (~5 nm) dielectric layer. The obtained structure can provide strong local electric field enhancement for surface-enhanced Raman scattering (SERS). The fabrication of the ordered array structure was realized by nanosphere self-assembly, atomic layer deposition, and metal thin-film dewetting. Numerical simulation proved that, compared to the conventional metal semishell arrays, the additional Ag particles introduce extra hot spots particularly in the valley regions between adjacent Ag semishells. As a result, the SERS enhancement factor of the metal semishell-based plasmonic structure could be further improved by an order of magnitude. The developed novel plasmonic structure also shows good potential for application in plasmon-enhanced solar water-splitting devices.
关键词： particle in cavity,nanosphere lithography,surface-enhanced Raman scattering (SERS),surface plasmonic,monolayer self-assembly
更新于2025-09-23 15:22:29
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Optical properties of ZnO deposited by atomic layer deposition (ALD) on Si nanowires
摘要： In this work, we report proof-of-concept results on the synthesis of Si core/ ZnO shell nanowires (SiNWs/ZnO) by combining nanosphere lithography (NSL), metal assisted chemical etching (MACE) and atomic layer deposition (ALD). The structural properties of the SiNWs/ZnO nanostructures prepared were investigated by X-ray diffraction, Raman spectroscopy, scanning and transmission electron microscopies. The X-ray diffraction analysis revealed that all samples have a hexagonal wurtzite structure. The grain sizes are found to be in the range of 7–14 nm. The optical properties of the samples were investigated using reflectance and photoluminescence spectroscopy. The study of photoluminescence (PL) spectra of SiNWs/ZnO samples showed the domination of defect emission bands, pointing to deviations of the stoichiometry of the prepared 3D ZnO nanostructures. Reduction of the PL intensity of the SiNWs/ZnO with the increase of SiNWs etching time was observed, depicting an advanced light scattering with the increase of the nanowire length. These results open up new prospects for the design of electronic and sensing devices.
关键词： nanosphere lithography (NSL),atomic layer deposition (ALD),Silicon nanowires (SiNWs),metal-assisted chemical etching (MACE),ZnO
更新于2025-09-23 15:21:21
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Transition from discrete patches to plasmonic nanohole array by glancing angle deposition on nanosphere monolayers
摘要： By combining nanosphere lithography and glancing angle deposition, a morphological transition from disconnected patchy silver (Ag) coated nanosphere particles to a connected Ag nanohole sheet on close-packed nanosphere monolayers has been demonstrated, which significantly changes the optical property of the Ag nanostructure deposited. For different sized nanosphere monolayers, when the vapor incident angle was set to be 55o, the transmission spectra showed complicated features when the Ag deposition thickness was less than 60 nm. When the thickness was large enough (> 60 nm), a distinguished extraordinary optical transmission (EOT) peak was observed. The EOT peak wavelength position is independent of the Ag thickness deposited and is proportional to the nanosphere diameter. The obtained EOT peaks possess a high quality factor and have high transmission values compared to those reported in the literature for similar structures. Such a high quality EOT response could be used for constructing better sensors or developing other plasmonic applications.
关键词： extraordinary optical transmission,nanosphere lithography,glancing angle deposition,silver nanoparticles,plasmonic nanohole array
更新于2025-09-19 17:13:59
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Tunable Optical Metamaterial-Based Sensors Enabled by Closed Bipolar Electrochemistry
摘要： Enabled by the proliferation of nanoscale fabrication techniques required to create spatially-repeating, sub-wavelength structures to manipulate the behavior of visible-wavelength radiation, optical metamaterials are of increasing interest. Here we develop and characterize a chemical sensing approach based on electrochemical tuning of the optical response function of large-area, inexpensive nanoaperture metamaterials at visible and near-IR wavelengths. Nanosphere lithography is used to create an ordered array of sub-wavelength apertures in a Au film. The spacing of these apertures is established during fabrication, based on the size of the polystyrene nanospheres. Tunable shifts in the transmission spectrum can be produced post-fabrication by electrodeposition of a dissimilar metal, Ag, using the nanoaperture film as one electrode in a 2-electrode closed bipolar electrochemical (CBE) cell, altering hole size, film thickness, and film composition while maintaining hole spacing dictated by the original pattern. Optical transmission spectra acquired under galvanostatic conditions can be expressed as a linear combination of the initial and final (saturated) spectra, and the resulting response function exhibits a sigmoidal response with respect to the amount of charge (or metal) deposited. This architecture is then used to perform optical coulometry of model analytes in a CBE-based analyte-reporter dual cell device, thus expanding the capability of CBE-based sensors. Increasing the exposed electrode area of the analyte cell increases the response of the device, while modifying the circuit resistance alters the balance between sensitivity and dynamic range. These tunable nanoaperture metamaterials exhibit enhanced sensitivity compared to CBE electrochromic reporter cells to the μM to nM concentration range, suggesting further avenues for development of CBE-based chemical sensors as well as application to inexpensive, point-of-care diagnostic devices.
关键词： nanosphere lithography,electrodeposition,closed bipolar electrochemistry,chemical sensing,optical metamaterials
更新于2025-09-11 14:15:04
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[IEEE 2018 IEEE 7th World Conference on Photovoltaic Energy Conversion (WCPEC) (A Joint Conference of 45th IEEE PVSC, 28th PVSEC & 34th EU PVSEC) - Waikoloa Village, HI (2018.6.10-2018.6.15)] 2018 IEEE 7th World Conference on Photovoltaic Energy Conversion (WCPEC) (A Joint Conference of 45th IEEE PVSC, 28th PVSEC & 34th EU PVSEC) - The damage mitigation process for Si nanopillar structure using silica nanosphere lithography and metal assisted chemical etching
摘要： This work focuses on mitigating the damage from nanostructure fabrication using silica nanosphere lithography (SNL) and metal assisted chemical etching (MACE). Metal contamination and plasma damage are the two main factors to limit the Si wafer's minority carrier lifetime. Ni/Au and Ti/Au metal layers on bare Si wafer are compared using lifetime recovery test. Ti/Au shows to be more suitable for the MACE process. Samples deposited with Ni/Au and Ti/Au show lifetimes of 7 μs and 1200μs, respectively. The silicon surface is degraded significantly by the RIE plasma during the nanosphere etching process. SiO2 protective layer was added to the process, mitigating significantly the plasma damage on the silicon surface. Lifetime measurements shows an improvement over 1 ms when SiO2 protective layer on planar Si wafer is used. Lifetimes of 353 μs and implied open circuit voltages of 651mV were accomplished on nanopillar structured wafers using SiOx protective layer and Ti/Au.
关键词： lifetime recovery,silica nanosphere lithography,metal assisted chemical etching,Si nanopillar structure,damage mitigation
更新于2025-09-11 14:15:04
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Fabrication of Uniform Gold Nanopatterns on Graphene by Using Nanosphere Lithography
摘要： In this study, we have realized controllable fabrication of gold nanopatterns on pristine monolayer graphene by using nanosphere lithography, in which polystyrene (PS) spheres are used as templates. With this method, periodically ordered triangular Au nanopatterns are uniformly formed on graphene surface. Micro-Raman spectroscopy shows that these sacrificial PS templates have no obvious effect on graphene surface structure while the subsequently formed Au nanopatterns are found to enhance Raman intensity of G and 2D bands by surface plasmon resonance. The compressive stress introduced in the metal deposition process leads to an obvious blue shift of 2D band. Besides, the metal-induced doping effect reduces the intensity ratio between 2D and G bands. This uniform arrangement of metal nanostructure is expected to grow other nanomaterials or used as Raman enhancement substrate in biomedicine, catalyzer and optics areas.
关键词： Gold Nanopatterns,Nanosphere Lithography,Graphene,Raman Spectroscopy
更新于2025-09-04 15:30:14