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Influence of ZnTe separation layer thickness on optical properties in CdTe/ZnTe double quantum dots on Si substrates
摘要： We investigate the influence of the ZnTe separation layer thickness on the photoluminescence (PL) dynamics of CdTe/ZnTe double quantum dots (DQDs) on Si substrates. The results clarify that the DQD's structure effectively improves the limit of the carrier collection and the thermal stability of the corresponding single-layer QDs. The unusual temperature-dependent PL is explained using the single model for thermal redistribution of carrier states. This model indicates that the main nonradiative process at high temperatures is caused by scattering via multiphonons with longitudinal optical phonon energy of about 19–21.3 meV. The confinement-induced mixing and electron-carrier coupling effects cause blue-shift and enhanced PL intensity. We propose that the separation layer controls carrier dynamics in optoelectronic devices by modulating the thermal escape and e-h pairs in the intermixing layers.
关键词： Quantum dots,Silicon substrate,Cadmium telluride,Thermal escape,Carrier confinement
更新于2025-09-16 10:30:52
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Ligand induced anomalous emission shift of size-controlled CsPbBr <sub/>3</sub> nanocrystals
摘要： CsPbX3 perovskite nanocrystals (NCs) have attracted much attention from researchers because of their excellent photoelectric properties like high quantum yield, large absorption cross section, and simple preparation process. The addition of ligands in the synthesis process has a significant effect on the microstructure and photophysical properties of solution-processed NCs, which needs further extensive studies. In this Letter, the effects of ligand electronegativity on the size and photoluminescence (PL) properties of CsPbBr3 NCs were reported. One is typical oleic acid with weak electronegativity, and another is 2-acrylamide-2-methylpropionic sulfonic acid with strong electronegativity. The third is their typical mixture with a molar ratio of 1:1. With the increase in ligand electronegativity, the size of CsPbBr3 NCs increases significantly. However, in contrast to the traditional quantum size confinement effect, the PL peak exhibits an abnormal blue shift gradually and the ligand passivation effect on NC surface defects also becomes more significant. The physical mechanism of this anomalous PL shift phenomena of CsPbBr3 NCs was investigated using the time-resolved PL spectrum and transient absorption spectrum.
关键词： transient absorption spectrum,quantum size confinement,photoluminescence,CsPbX3 perovskite nanocrystals,ligand electronegativity,time-resolved PL spectrum
更新于2025-09-16 10:30:52
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[IEEE 2019 Compound Semiconductor Week (CSW) - Nara, Japan (2019.5.19-2019.5.23)] 2019 Compound Semiconductor Week (CSW) - Numerical Demonstration of Trade-off between Carrier Confinement Effect and Carrier Transport for Multiple-Quantum-Well Based High-efficiency InGaP Solar Cells
摘要： To promote InGaP solar cell efficiency toward the theoretical limit, one promising approach is to incorporate multiple quantum wells (MQWs) into the InGaP host and improve its open-circuit voltage by facilitating radiative carrier recombination owing to carrier confinement. In this research, we demonstrate numerically that a strain-balanced (SB) In1-xGaxP/In1-yGayP MQW enhances confined carrier density while degrades the effective carrier mobility. However, a smart design of the MQW structure is possible by considering quantitatively the trade-off between carrier confinement effect and carrier transport, and MQW can be advantageous over the InGaP bulk material for boosting photovoltaic efficiency.
关键词： InGaP,carrier confinement effect,photovoltaics,multiple quantum wells
更新于2025-09-12 10:27:22
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Effective electromagnetic shielding with multi-layer structure material on Shenguang laser facility
摘要： Electromagnetic pulses (EMPs) with high intensity and frequency bandwidth can be generated during the intensive laser irradiating solid targets in inertial confinement fusion (ICF). To shield the EMPs radiation and hence protect various diagnostics in and outside the target chamber, we designed a multi-layer structure material to shield the EMPs and demonstrate experimentally and numerically shielding performance of the material structure. The thickness of the multi-layer structure material has a great influence on the EMPs shielding. It is shown that, with the increase of the material thickness, the better shielding performance is obtained, and the material structure with polytetrafluoroethylene (PTFE) of 0.5 mm, copper of 0.4 mm and lead of 2.4 mm reduces 448 times compared the maximum value of EMPs voltage to that without shielded. The design of multi-layer structure material for EMPs shielding provides a promising way to reduce EMPs radiation, which is extremely useful for the diagnostics protection and signal processing in ICF.
关键词： inertial confinement fusion,Shenguang laser facility,electromagnetic pulse,shielding
更新于2025-09-12 10:27:22
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AN EXPLORATION INTO THE QUANTUM CONFINEMENT OF CTS/NATURAL DYE CORE- SHELL QUANTUM DOTS
摘要： In this work, we have presented a simple way of changing the confinement energies of Copper Tin Sulphide (CTS) quantum dots using natural dyes as shell material. Tetragonal CTS quantum dots in the size range of 1.7nm- 2.2nm, of bandgaps of 2.48eV and 5.0 eV were prepared by means of a green colloidal synthesis technique. These quantum dots were treated with natural dyes such as onion and beetroot skin dyes. Pelargonidin and Betanin (pigments of onion and beetroot skin dye respectively) formed hydrogen bonding with the capping agent, thus forming a shell around the CTS quantum dots. The change in confinement due to the effect of dye as shell was studied from absorption, photoluminescence and infrared spectroscopic techniques. The transitions occurring were analysed using a theoretical approach. CTS quantum dots, with its high transmittance in a wide range of wavelengths find promising applications in the buffer layer of solar cells.
关键词： Betanin,Copper tin sulphide,quantum dots,Pelargonidin,colloidal synthesis,quantum confinement
更新于2025-09-12 10:27:22
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A nanoreactor based on SrTiO3 coupled TiO2 nanotubes confined Au nanoparticles for photocatalytic hydrogen evolution
摘要： A TiO2 nanotube-based nanoreactor was designed and fabricated by facile two steps synthesis: firstly, hydrothermal synthesized SrTiO3 was deposited on TiO2 nanotubes (TiO2NTs). Secondly, the Au nanoparticles (NPs) were encapsulated inside the TiO2NTs followed by vacuum-assisted impregnation. The as-synthesized composites were characterized using Transmission electron microscopy (TEM), X-ray powder diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Photoluminescence spectra (PL) and Ultravioletevisible absorption spectroscopy (UVevis). The photocatalytic performance was evaluated by the hydrogen evolution reaction. The results revealed that the SrTiO3 modified TiO2NTs confined Au NPs (STO-TiO2NTs@Au) achieved an enhanced hydrogen evolution rate at 7200 mmol h?1 g?1, which was 2.2 times higher than that of bald TiO2NTs@Au at 3300 mmol h?1 g?1. The improved photocatalytic activity could be attributed to the synergistic effect of the electron-donating of SrTiO3 and TiO2NTs confinement. The as-designed nanoreactor structure provides an example of efficient carriers’ separation photocatalyst.
关键词： Au nanoparticles,Confinement,SrTiO3,TiO2 nanotubes,Photocatalytic hydrogen evolution
更新于2025-09-12 10:27:22
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Surface/edge functionalized boron nitride quantum dots: Spectroscopic fingerprint of bandgap modification by chemical functionalization
摘要： Promising properties of boron nitride nanomaterials such as their chemical, thermal, and mechanical stability have made them suitable materials in a various range of applications. However, their low electrical conductivity and wide bandgap, particularly in the case of boron nitride quantum dots (BNQDs), have given rise to severe limitations. Efforts on bandgap engineering through doping and surface functionalization have gained little success due to their high thermodynamic stability and inertness. Herein, we present a novel approach to functionalize BNQDs by hydroxyl, methyl, and amine functional groups aiming to adjust the electronic structure. The successful exfoliation is demonstrated by transmission electron microscopy, and surface functionalization is elaborated by FTIR and XPS. Modifications of the electronic and optical properties are shown by UV–Vis and PL measurements. The formation of two absorption edges in bandgaps of BNQDs due to the delocalizing of the Px and Pz orbitals as result of edge/surface passivating groups is demonstrated. Splitting of the main transition bandgap of bulk BN from 5.9 eV to two absorption edges for hydroxyl (2.3-3.6 eV), methyl (3.2-4.2 eV), and amine (3.1-4 eV) is shown. These findings offer a bandgap engineering approach for BNQDs, which can boost their applications in quantum emitters (nanophotonics) and photovoltaic devices.
关键词： Surface science,Nanoparticle semiconductor,Quantum confinement,Bandgap engineering
更新于2025-09-12 10:27:22
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Combined implementation of smoothing technologies for improving illumination uniformity of laser quad in multi-directions
摘要： Azimuthal smoothing (AS) that enables the focal spot of a laser quad to rotate in a period of a few picoseconds can improve the illumination uniformity. However, the smoothing performance of azimuthal smoothing is worse than that of smoothing by spectral dispersion (SSD) due to the low rotation speed in the center area of the focal spot. A combined implementation of the schemes including smoothing by spectral dispersion, radial smoothing (RS) and azimuthal smoothing is discussed to achieve better and faster illumination uniformity. The theoretical models of the combined smoothing scheme have been built up to analyse the smoothing performance. The key parameters affecting the smoothing performance of the combined smoothing scheme are analysed and optimized, including the topological charge and the wavelength difference. The simulation results show that the illumination uniformity of the laser quad can be significantly improved in multi-directions by the combined smoothing scheme.
关键词： Inertial confinement fusion,azimuthal smoothing scheme,vortex beam,radial smoothing,uniformity,smoothing by spectral dispersion
更新于2025-09-12 10:27:22
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Alloyed Ag2SexS1-x quantum dots with red to NIR shift: the band gap tuning with dopant content for energy harvesting applications
摘要： Alloyed quantum dots have pulled in a large consideration because of their fascination from visible to near infrared regime. In this work, quantum dots of alloyed Ag2SexS1-x (x = 0, 0.4, 0.6, 1.0) system are synthesized by making use of a simple intermediate temperature method. The structure and morphology of Ag2SexS1-x quantum dots are examined through X-ray diffraction, Fourier-transform infrared spectroscopy, transmission electron microscopy, and Raman spectroscopy. The X-ray diffraction data indicates monoclinic and orthorhombic structure of Ag2SexS1-x quantum dots. The size and composition controlled optical bandgap of Ag2SexS1-x quantum dots is meticulously looked into by Ultraviolet-Visible-Near Infrared absorption spectroscopy. The size of alloyed Ag2SexS1-x quantum dots varies from 3.5 nm to 4.8 nm. The bandgap of Ag2SexS1-x quantum dots has varied from 1.35 eV to 0.88 eV as calculated by Tauc plot. The observed values of bandgap indicate quantum confinement in two regimes-weak and strong confinement regimes. The results show that quantum confinement depends on both the size and composition of Ag2SexS1-x quantum dots. The alloying of Se to Ag2S has been confirmed using the Raman spectroscopy. These alloyed quantum dots might be reasonable for catching solar energy particularly from visible to NIR regime.
关键词： Alloyed Quantum Dots,Solar Energy,Quantum Confinement,Optical Band Gap
更新于2025-09-12 10:27:22
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AIP Conference Proceedings [AIP Publishing SECOND INTERNATIONAL CONFERENCE ON MATERIAL SCIENCE, SMART STRUCTURES AND APPLICATIONS: ICMSS-2019 - Erode, India (21–22 November 2019)] SECOND INTERNATIONAL CONFERENCE ON MATERIAL SCIENCE, SMART STRUCTURES AND APPLICATIONS: ICMSS-2019 - Adopted octagonal photonic crystal fiber for analyte liquids sensing
摘要： In this paper, octagonal-photonic crystal fiber (O-PCF) has been proposed for studying liquid types for sensing applications. The propagation properties for the proposed O-PCF were studied numerically by utilizing full-vector finite element method (FV-FEM ) using COM SOL M ultiphysics version 5.1. The confinement loss, the relative sensitivity, and the nonlinearity coefficient can be controlled by changing the factors related with the geometry such as the cladding in a range of wavelength, air hole diameter, and the core pitch. The proposed O-PCF is realized with three rings from the air hole in the cladding and two circular rings in the core region. Numerical simulation of the proposed structure is achieving the highest sensitivity by increasing the diameter of the air hole the cladding, while the pitch remains constant. At the same time, the confinement losses have distinguishable decrease with an increase in diameter as well as an increase in the number of rings within the cladding layer. In addition, the effective area and the nonlinear coefficient each of them is affected with every hole of the diameter and with the type of the chemical material used. The proposed model shows that the fiber is of a high efficiency not only in the sensing application, but also being distinguishable with the nonlinear optical application.
关键词： chemical sensor,nonlinearity coefficient,O-PCF,Sensitivity,confinement loss
更新于2025-09-12 10:27:22