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Zn1 a?? xCdxS Nanoparticles Obtained by Laser Ablation
摘要： Approximately spherical nanoparticles of the II–VI semiconductor materials Zn1 – xCdxS have been produced successfully by laser ablation of the bulk material in several liquids. The non-stabilized suspensions of particles are characterized by absorption spectroscopy and transmission electron microscopy (TEM). The procedure is not strongly size-selective, radii of 7 ± 3 nm were found for Zn1 – xCdxS by transmission electron microscopy. Acetonitrile stabilizes the particles for several days up to weeks. Prolonged irradiation leads effectively to a reduction in particles size, in which particle agglomeration may play an important role. Ablation in degassed liquids does not have a significant effect on the absorption of the suspended particles.
关键词： Zn1 – xCdxS nanoparticles,laser ablation,absorption spectroscopy,transmission electron microscopy,quantum confinement
更新于2025-09-19 17:13:59
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Effect of a p-type ZnO insertion layer on the external quantum efficiency of GaInN light-emitting diodes
摘要： The external quantum ef?ciency (EQE) of a GaInN green light-emitting diode (LED) is improved by inserting a p-type ZnO layer between the indium tin oxide electrode and the p-type GaN layer. Several hypotheses are discussed to explain the EQE improvement in the LED with the ZnO layer. It is concluded that higher hole injection ef?ciency and better electron con?nement explain the EQE improvement, which is supported by the results of device simulations showing that the EQE is sensitive to the polarization sheet charge density at the interface between the last quantum barrier and electron-blocking layer.
关键词： external quantum efficiency,electron confinement,GaInN,hole injection efficiency,light-emitting diodes,p-type ZnO
更新于2025-09-16 10:30:52
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Spectral characteristics of laser-induced plasma under the combination of Au-nanoparticles and cavity confinement
摘要： To enhance the emission spectrum intensity of laser-induced plasma, a method of combining cavity-enhanced laser-induced breakdown spectroscopy (LIBS) with nanoparticles-enhanced LIBS (NELIBS) was proposed. In this paper, the brass with Au-nanoparticles deposited on the surface is placed under the condition of cavity confinement and cavity-free confinement, and the differences between various performances are analyzed. The experimental results show that spectral line enhancement effect is the best when cavity confinement diameter is 5 mm. When cavity-enhanced LIBS is combined with NELIBS, the plasma intensity is effectively enhanced, and the enhancement factor is up to 20.24 (Cu I 515.4 nm); signal-to-noise ratio (SNR) is improved significantly, and it reaches 337.21 when pulse energy is 60 mJ. Electron temperature is in the range of 12,040–14,260 K and electron density is increased, the ability of detect trace elements is greatly improved.
关键词： Cavity confinement,Electron temperature,LIBS,SNR,Au-nanoparticles
更新于2025-09-16 10:30:52
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Size-controlled excitonic effects on electronic and optical properties of Sb <sub/>2</sub> S <sub/>3</sub> nanowires
摘要： In this work, the electronic and optical properties of one-dimensional (1D) Sb2S3 nanowires (NWs) with different sizes are investigated using first-principles calculations. The indirect–direct band transition of Sb2S3 NWs can be tuned effectively by the NW size and various uniaxial strains. In the Sb2S3 NWs, the quantum confinement effects result in wider bandgaps while the significantly enhanced electron–hole interaction that is expected to produce excitonic bound states generates a bandgap narrowing. The exciton binding energies for the Sb2S3 NWs are predicted by the effective masses of electrons and holes to lie in the range of 0–1 eV, which are larger than that of bulk Sb2S3, suggesting that excitons in Sb2S3 NWs may bind possible defects to promote luminescence. The size-controlled absorption edge blueshift and redshift of Sb2S3 NWs suggest that Sb2S3 NWs may be promising in the applications of nanoscale light emitting devices.
关键词： optical properties,first-principles calculations,quantum confinement effects,light emitting devices,electronic properties,exciton binding energies,Sb2S3 nanowires
更新于2025-09-16 10:30:52
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Quantum Confinement Induced Excitonic Mechanism in Zinc-Oxide-Nanowalled Microrod Arrays for UV–Vis Surface-Enhanced Raman Scattering
摘要： We studied surface-enhanced Raman spectroscopy (SERS) in 4-mercaptopyridine (4-Mpy) deposited on zinc oxide (ZnO) nanostructures, by using resonance Raman scattering covering a range of incident photon energies from 1.7 to 5.7 eV. We investigated all primary routes of the energy-specific resonances that are associated with the electronic transitions between the ZnO valence band (VB) to the lowest unoccupied molecular orbital (LUMO) and the highest occupied molecular orbital (HOMO) to the ZnO conduction band (CB), respectively. Two resonances at 5.55 and 5.15 eV in the ultraviolet (UV) spectral range can be associated with transitions into the CB and most importantly into an excitonic-related state below the ZnO CB, respectively. The energy difference between the UV resonances is 0.4 eV corresponding to the excitonic binding energy as a result of excitonic quantum confinement in the 10?20 nm thick ZnO nanowalls. The observed excitonic SERS resonance enhancement of the ring-breathing mode of 4-Mpy is about 15 times stronger than for the VB resonance observed at 2.43 eV and free of luminescence background. Hence, we outline new pathways of improving the detectability of molecules by chemical SERS due to tuning of the quantum confinement in the excitonic resonance enhancement.
关键词： quantum confinement,surface-enhanced Raman spectroscopy,excitonic mechanism,UV-Vis,ZnO,SERS,zinc oxide
更新于2025-09-16 10:30:52
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Spatial confinement effects of bubbles produced by laser ablation in liquids
摘要： The paper deals with the influence of the spatial confinement on the evolution of laser bubbles and shock waves by means of the shadowgraphy technique. Due to the constraint of walls, the bubble center shrinks faster than the bubble edge and collapses before the edge of the bubble, splitting into left and right small bubbles that continue to shrink down. The result validates that the Bjerknes force has little effect on bubble evolution at the expansion stage but a great influence on it at the collapse stage. We study the evolution of laser bubbles with different Al-plate intervals for displaying a gradual transition from constrained conditions to unconstrained conditions. In addition, we describe the dynamics of the first bubble at the expansion stage using the Rayleigh-Plesset equation. The pressure and temperature inside laser bubbles are calculated in the meanwhile.
关键词： spatial confinement,Rayleigh-Plesset equation,shock waves,laser ablation,bubbles
更新于2025-09-16 10:30:52
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Efficient coupling of light from dielectric to HIMI plasmonic waveguide
摘要： This is the ?rst report on the investigation of a hybrid plasmonic tapered coupler injecting light ef?ciently from conventional dielectric waveguide to a hybrid insulator–metal–insulator (HIMI) plasmonic waveguide. The proposed structure gives high transmission ef?ciency and suppresses the re?ection losses signi?cantly. With this tapered coupling mechanism, maximum transmittance and return loss of 98% and 26 dB have been observed, respectively. The coupler also offers very good propagation length (274 μm) along with minimal mode propagation losses (0.016 dB/μm). Apart from that, it offers decent con?nement of light in low dielectric regions up to 32%. The proposed structure is designed in an ultra-short tapered length of 1.0 μm, and the entire structure occupies a footprint area of 1.4 × 2.4 μm2. Proposed hybrid waveguide coupler could be useful for several chip scale applications.
关键词： chip scale applications,light confinement,hybrid plasmonic tapered coupler,propagation length,mode propagation losses,reflection losses,HIMI plasmonic waveguide,transmission efficiency
更新于2025-09-16 10:30:52
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Perovskite quantum dots for light-emitting devices
摘要： Perovskite quantum dots (QDs) have been hotly pursued in recent decades owing to their quantum confinement effect and defect-tolerant nature. Their unique optical properties, such as high photoluminescence quantum yield (PLQY) approaching unity, narrow emission bandwidth, tunable wavelength spanning the entire visible spectrum, and compatibility with flexible/stretchable electronics, render perovskite QDs promising for next-generation solid lighting sources and information displays. Herein, the advances in perovskite QDs and their applications in LEDs are reviewed. Strategies to fabricate efficient perovskite QDs and device configuration, including material composition design, synthetic methods, surface engineering, and device optimization, are investigated and highlighted. Moreover, the main challenges in perovskite QDs of instability and toxicity (lead-based) are identified, while the solutions undertaken with respect to composition engineering, device encapsulation, and lead-replacement QDs are demonstrated. Meanwhile, perspectives for the further development of perovskite QDs and corresponding LEDs are presented.
关键词： device encapsulation,quantum confinement,Perovskite quantum dots,LEDs,instability,composition engineering,flexible electronics,photoluminescence,lead-replacement,stretchable electronics,toxicity,light-emitting devices
更新于2025-09-16 10:30:52
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Facile Preparation of Molybdenum Disulfide Quantum Dots Using a Femtosecond Laser
摘要： Molybdenum disulfide (MoS2) is rapidly emerging in a wide range of applications owing to its superior optical, electrical, and catalytic properties. In particular, aside from the current great interest in monolayer MoS2, MoS2 quantum dots (QDs) have received much attention in the electronics and optoelectronics fields owing to their inherent electrical and optical properties arising from the quantum confinement effect. Thus, various methods for producing MoS2 QDs, such as exfoliation, substrate growth, and colloidal synthesis, have been attempted. In this study, the method for manufacturing MoS2 QD with a size of 10 nm which is simpler than the conventional method was devised. On the basis of characterization of the prepared MoS2 QD samples, resistive switching devices was fabricated. These devices demonstrated stable unipolar resistive switching behavior without an electroforming process. This study provides a new approach for the mass production of MoS2 QD and one of their potential applications.
关键词： exfoliation,memristor,MoS2,quantum confinement effect,phase transition
更新于2025-09-16 10:30:52
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Raman spectroscopy of poly (methyl methacrylate) under laser shock and static compression
摘要： Time-resolved Raman spectroscopy for visualizing molecular fingerprint snapshots at nanosecond time scale is a useful tool for detailed understanding of in situ shock behaviour of materials. This technique was applied to study the changes in molecular vibrations of poly (methyl methacrylate) (PMMA) under laser driven shock compression up to ~1.9 GPa in a confinement geometry. A layered target configuration is used to enhance the shock pressure. The vibrational modes are measured as a function of dynamic shock and static compression. The Grüneisen parameters and bond anharmonicities in PMMA are determined using compression behaviour of Raman modes. The deduced shock velocity (~3.5 ± 0.4 km/s) in PMMA based on the time evolution of shocked Raman mode at 1.9 GPa is in agreement with the one calculated (~3.7 km/s) from 1-D radiation hydrodynamic simulations. A comparative study on shock experiment and static high pressure Raman spectroscopic measurements is done. Static pressure measurement up to ~16 GPa show rapid blue shifting of C–H stretching modes.
关键词： Raman spectroscopy,PMMA,confinement geometry,Raman shift,laser shock,diamond anvil cell (DAC),static experiment
更新于2025-09-16 10:30:52