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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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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
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Helium focused ion beam direct milling of plasmonic heptamer-arranged nanohole arrays
摘要： We fabricate plasmonic heptamer-arranged nanohole (HNH) arrays by helium (He) focused ion beam (HeFIB) milling, which is a resist-free, maskless, direct-write method. The small He+ beam spot size and high milling resolution achieved by the gas field-ionization source used in our HeFIB allows the milling of high aspect ratio (4:1) nanoscale features in metal, such as HNHs incorporating 15 nm walls of high verticality between holes in a 55-nm-thick gold film. Drifts encountered during the HeFIB milling of large arrays, due to sample stage vibrations or He beam instability, were compensated by a drift correction technique based on in situ He ion imaging of alignment features. Our drift correction technique yielded 20 nm maximum dislocation of HNHs, with 6.9 and 4.6 nm average dislocations along the horizontal and vertical directions, respectively. The measured optical resonance spectra of the fabricated plasmonic HNH arrays are presented to support the fabrication technique. Defects associated with HeFIB milling are also discussed.
关键词： plasmonics,focused ion beam,helium ion microscopy,nanofabrication
更新于2025-09-12 10:27:22
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Creation of Si quantum dots in a silica matrix due to conversion of radiation defects under pulsed ion-beam exposure
摘要： In this work we present an innovative method of creating Si quantum dots under pulsed ion-beam exposure. The evolution of defect structure ODC(II) - E0 - ODC(I) - Si QDs in glassy SiO2 under ion-beam implantation was established by optical absorption and photoluminescence spectroscopies. Depending on the mode of ion exposure, it is possible to easily control the type and concentration of defects in the host and modify its optical properties for novel applications. Ab initio calculations confirm that bond softening in SiO2 is attainable via the use of Gd ion implantation. According to our experimental and theoretical results, the three-stage interaction of primary oxygen-deficient centers leads to the formation of stable silicon quantum dots with a size of 3.6 nm and luminescence at 1.8 eV excited by incoherent light.
关键词： Gd ion implantation,Si quantum dots,pulsed ion-beam exposure,optical absorption,photoluminescence spectroscopies,glassy SiO2
更新于2025-09-12 10:27:22
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Design and optimization of a laser-PIXE beamline for material science applications
摘要： Multi-MeV proton beams can be generated by irradiating thin solid foils with ultra-intense (>1018 W/cm2) short laser pulses. Several of their characteristics, such as high bunch charge and short pulse duration, make them a complementary alternative to conventional radio frequency-based accelerators. A potential material science application is the chemical analysis of cultural heritage (CH) artifacts. The complete chemistry of the bulk material (ceramics, metals) can be retrieved through sophisticated nuclear techniques such as particle-induced X-ray emission (PIXE). Recently, the use of laser-generated proton beams was introduced as diagnostics in material science (laser-PIXE or laser-driven PIXE): Coupling laser-generated proton sources to conventional beam steering devices successfully enhances the capture and transport of the laser-accelerated beam. This leads to a reduction of the high divergence and broad energy spread at the source. The design of our hybrid beamline is composed of an energy selector, followed by permanent quadrupole magnets aiming for better control and manipulation of the final proton beam parameters. This allows tailoring both, mean proton energy and spot sizes, yet keeping the system compact. We performed a theoretical study optimizing a beamline for laser-PIXE applications. Our design enables monochromatizing the beam and shaping its final spot size. We obtain spot sizes ranging between a fraction of mm up to cm scale at a fraction of nC proton charge per shot. These results pave the way for a versatile and tunable laser-PIXE at a multi-Hz repetition rate using modern commercially available laser systems.
关键词： hybrid beamline and beam manipulation,laser-PIXE,Cultural heritage,particle induced X-ray emission (PIXE),laser-driven proton acceleration,ion beam analysis
更新于2025-09-12 10:27:22
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Double-Lattice Magnetoplasmonic Structures Based on BIG and Perforated Gold Films
摘要： A method of manufacturing double-lattice magnetoplasmonic crystals with the structure (Au/BIG)2, in which the plasmon gold lattices are displaced relative to each other by half a period, has been presented. Gold films with thicknesses of about 40 nm have been formed by the ion-beam sputtering–deposition method, while the adhesive properties of the films allow the dimensional etching by a sharp-focused ion beam. It has been shown that the formation of the second plasmon lattice located on top of the 100 nm thick garnet layer allows the preserving of the periodicity of the first Au lattice. However, there is a significant influence of diffusion spreading on the lower lattice material, which leads to a decrease in its density. The dependence of the intensity magnetooptical effect in the geometry on the transmission as a function of the thickness of the upper lattice and presence of an additional layer of Ta2O5 has been studied.
关键词： polycrystalline ferrite-garnet,magnetoplasmonic crystals,magnetooptical effects,deposition,ion-beam methods,sputtering,plasmon resonance
更新于2025-09-11 14:15:04
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European Microscopy Congress 2016: Proceedings || FIB patterning for position-controlled nanowire growth
摘要： Semiconductor nanowire (NW) based heterostructures are a promising material system for next generation optoelectronic devices, such as flexible solar cells and light emitting diodes [1]. Their reduced contact area and surface strain relaxation allow for epitaxial growth on lattice-mismatched substrates, a key advantage for integration of different III-V semiconductors with existing silicon-based technology. Position-controlled NWs can be grown in ordered arrays on Si to improve uniformity and device integration. This is commonly performed by using a SiO2 thin film as a mask. Patterning of circular holes in the mask (Fig. 1(a)) allows for site-specific NW growth in predefined patterns and positions. To date, this is performed using lithography techniques such as electron beam lithography or nanoimprint lithography [2]. Important processing parameters include oxide thickness, hole diameter and pattern pitch, requiring several steps to be optimized in order to achieve a high yield of uniform NWs [3]. Additionally, the catalytic particle is rarely centered in the hole, leading to undesirable asymmetry in the NW cross-sections [4]. In this work, the parameter space for direct patterning of NW growth substrates by focused ion beam (FIB) is explored (Fig. 1). Self-catalyzed GaAsSb NWs were grown using molecular beam epitaxy (MBE) on a FIB patterned Si(111) substrate with 40 nm thermal oxide, where hole size, dose and Ga-beam overlap were systematically varied (Fig. 1(a-c)). It is expected that a higher degree of flexibility and control can be attained using FIB compared to the conventionally used resist-based patterning techniques. In addition, patterning by FIB leads to Ga implantation in both Si and SiO2, which could positively affect the self-catalyzed NW growth and the properties of the NW-substrate system in a unique way. After MBE growth, three distinct growth regimes can be recognized, present in all arrays (Fig. 1(d-e)): The smallest (10 nm pattern) diameter row features a high yield (≤ 80%) of straight NWs. As the hole diameter increases there is initially a transition to more parasitic crystal growth and finally multiple (2-5) NWs grow within each hole. As the dose increases between arrays in each column, the patterned diameter for these transitions decreases proportionally. The results demonstrate that using FIB the parameter space can be mapped out efficiently within a single growth session and that growth can be tuned between aligned single NWs, 2D parasitic crystals and multiple NWs per hole. Transmission electron microscopy and electrical testing of single NWs directly on the growth substrate [5] will be used to refine the structural analysis and study the electrical properties of these NWs. It is expected that in addition to the flexibility of FIB patterning, III-V NWs grown on FIB-patterned Si will exhibit novel properties due to the implantation of Ga and the altered NW-substrate interface.
关键词： self-catalyzed,nanowires,focused ion beam,nanostructuring,GaAsSb
更新于2025-09-11 14:15:04
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Synthesis of Plasmonic Photonic Crystal SiO2–Ag Nanostructures by Ion Beam Deposition of Silver Clusters onto Silica Microspheres
摘要： The synthesis of plasmonic photonic crystal SiO2–Ag nanostructures by deposition of silver nanoparticles is considered. The technique includes the physical sputtering of a silver target with a kiloelectronvolt argon ion beam onto silica microspheres obtained according to St?ber. The plasmon resonance effect is shown to be interrelated with the optical properties of nanostructured supports and the morphology of aggregate structures of silver nanoparticles (clusters).
关键词： silica microspheres,ion beam deposition,plasmonic photonic crystal,SiO2–Ag nanostructures,silver clusters
更新于2025-09-11 14:15:04
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Investigation of the scintillation screens used for low energy DC ion beam profiling
摘要： A ion beam profile monitoring system based on scintillation screens has been established for a neutron generator used for neutron radiography. Three types of scintillation screens (monocrystalline Al2O3, Quartz and BGO) were investigated for their response to the 100 keV, 30 ??A, DC deuterium ion beams. The light yield, beam width, and electric charge accumulation effect of the scintillation materials were tested. The temperature rises of the scintillation screens caused by ion irradiation was calculated. Results showed that, the electric charge accumulation effect is very serious for this type of ion beams, and the using of metal film or mesh on the scintillation screen surface to diminish the electric charging is necessary. Al2O3 screen owns the best behavior of radiation hardness, its measured beam width only shows a little change for the ion irradiation of up to 2.3×1015 particles/mm2. The temperature rises of Al2O3, Quartz and BGO under ion irradiation of 2.3×1015 particles/mm2 was 120 ?C, 243 ?C, and 768 ?C respectively. The temperature rise difference is quite coincident with the light yield degradation of the three material, so temperature might be the key factor that affect the light yield degradation of scintillation materials.
关键词： Beam profile,Radiation effect,Scintillation screen,Low energy ion beam
更新于2025-09-10 09:29:36
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Variation of the photoluminescence spectrum of InAs/GaAs heterostructures grown by ion-beam deposition
摘要： This work reports on an experimental investigation of the influence of vertical stacking of quantum dots, the thickness of GaAs potential barriers, and their isovalent doping with bismuth on the photoluminescence properties of InAs/GaAs heterostructures. The experimental samples were grown by ion-beam deposition. We showed that using three vertically stacked layers of InAs quantum dots separated by thin GaAs barrier layers was accompanied by a red-shift of the photoluminescence peak of InAs/GaAs heterostructures. An increase in the thickness of the GaAs barrier layers was accompanied by a blue shift of the photoluminescence peak. The effect of isovalent Bi doping of the GaAs barrier layers on the structural and optical properties of the InAs/GaAs heterostructures was investigated. It was found that the Bi content up to 4.96 atom % in GaAs decreases the density of InAs quantum dots from 1.53 × 1010 to 0.93 × 1010 cm?2. In addition, the average lateral size of the InAs quantum dots increased from 14 to 20 nm, due to an increase in the surface diffusion of In. It is shown that isovalent doping of GaAs potential barriers by bismuth was accompanied by a red-shift of the photoluminescence peak of InAs quantum dots of 121 meV.
关键词： photoluminescence,semiconductors,quantum dot,ion-beam deposition,nanoheterostructures,infrared photodetectors
更新于2025-09-10 09:29:36