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A method to extend wavelength into middle-wavelength based on InAsSb/(Al)GaSb interband transition quantum well infrared photodetector
摘要： A method to extend the operating wavelength of the interband transition quantum well photodetector from extended short-wavelength IR to middle-wavelength infrared has been introduced. In the modified InAsSb quantum well, GaSb is replaced with AlSb/AlGaSb, the valence band of barrier material is lowered, the first restricted energy level (E1) is higher than the valence band of barrier material, the energy band structure forms type-II structure. The photocurrent spectral manifested that the fabricated photodetector exhibited a response range from 1.9 μm to 3.2 μm with two peaks at 2.18 μm and 3.03 μm at 78 K.
关键词： energy band calculation,InAsSb/AlSb/AlGaSb quantum well,interband transition,photodetector
更新于2025-09-23 15:21:01
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Anti-Stokes Emission from Hot Carriers in Gold Nanorods
摘要： The origin of light emission from plasmonic nanoparticles has been strongly debated lately. It is present as the background of surface enhanced Raman scattering, and, despite the low yield, has been used for novel sensing and imaging application because of its photostability. While the role of surface plasmons as an enhancing antenna is widely accepted, the main controversy regarding the mechanism of the emission is its assignment to either radiative recombination of hot carriers (photoluminescence) or electronic Raman scattering (inelastic light scattering). We have previously interpreted the Stokes shifted emission from gold nanorods as the Purcell effect enhanced radiative recombination of hot carriers. Here we specifically focused on the anti-Stokes emission from single gold nanorods of varying aspect ratios with excitation wavelengths below and above the inter-band transitions threshold while still employing continuous wave lasers. Analysis of the intensity ratios between Stokes and anti-Stokes emission yields temperatures that can only be interpreted as originating from the excited electron distribution and not a thermally equilibrated phonon population despite not using pulsed laser excitation. Consistent with this result as well as previous emission studies using ultrafast lasers, the power-dependence of the upconverted emission is nonlinear and gives the average number of participating photons as a function of emission wavelength. Our findings thus show that hot carriers and photoluminescence play a major role in the upconverted emission.
关键词： surface plasmon resonance,anti-Stokes photoluminescence,interband transition,intraband transition,hot electron temperature,gold nanoparticle
更新于2025-09-19 17:15:36
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Effect of gravity and electromagnetic field on the spectra of cylindrical quantum dots together with AB flux field
摘要： In this work, we study the spectral properties of electron quantum dots (QDs) confined in 2D parabolic harmonic oscillator influenced by gravity, external uniform electromagnetic field together with an Aharonov–Bohm (AB) flux field. Our calculations are based on the Nikiforov–Uvarov method and we obtain exact solutions for the energy levels and normalized wave functions. The interband optical absorption QDs of the parabolic spherical shape in GaAs is studied theoretically and the total optical absorption coefficient has been calculated by using the energy eigenvalues spectra and the corresponding wave functions.
关键词： quantum dots,threshold frequency of absorption,Aharonov–Bohm flux field,gravity,light interband transition,Parabolic harmonic oscillator,electromagnetic field
更新于2025-09-16 10:30:52
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Effects of GaN capping layer on carrier occupation and interband transition probability of vertically coupled InGaN/GaN quantum dots
摘要： The carrier occupation and the interband transition probability of wurtzite (WZ) coupled InGaN/GaN quantum dots (QDs) were investigated as a function of the distance d between QDs in a range of 30?70?A. The light emission intensity rapidly decreases with increasing the distance d and becomes minimum near d=50?A. This can be explained by the fact that the matrix element values are significantly reduced with increasing d owing to an increase in the internal field and the quasi-Fermi-level separation shows a minimum value at d=50?A. However, the light intensity slightly begins to increase when d exceeds 50?A because the quasi-Fermi-level separation increases with increasing d. These results can be used as the design guideline of the active region in QD-based optoelectronic devices with a high efficiency.
关键词： optoelectronic devices,interband transition probability,GaN capping layer,InGaN/GaN quantum dots,carrier occupation
更新于2025-09-11 14:15:04
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Light irradiation enhanced CO2 reduction with methane: A case study in size-dependent optical property of Ni nanoparticles
摘要： Ni/Al2O3 catalysts and bulk Ni nanoparticles, with the average sizes of Ni particles varying from 2.7 nm to 238.0 nm, were synthesized and evaluated in CO2 photoreduction with methane (CRM). It was found that the catalytic activities of the Ni-based catalysts were all increased almost linearly with light intensity in the range of 0–1.07 W cm?2, with the optical properties of Ni particles being regarded to account for the activity enhancement. Wavelength dependent performance study suggested that Ni LSPR dominated for the optical property of smaller Ni nanoparticles whereas interband transition played gradually increased role in improving the activities over larger Ni particles. To the best of our knowledge, it is the first time to study the size-dependent optical properties of Ni nanoparticles, meanwhile, this study offers a foundation to further improve the efficiency of Ni-based catalysts in CO2 utilizations.
关键词： Ni nanoparticles,Interband transition,CO2 photoreduction,Localized Surface plasmon resonance,Photocatalysis
更新于2025-09-10 09:29:36
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Ultrathin Conductor Enabling Efficient IR Light CO2 Reduction
摘要： Concurrent transformation of carbon dioxide and water into hydrocarbons and oxygen by low-photonic-energy IR light still represents a huge challenge. Here, we design an ultrathin conductor system, in which the special partially occupied band serves as the mediator to simultaneously guarantee IR light harvesting and satisfied band-edge positions, while the ultrathin configuration improves charge separation rates and surface redox kinetics. Taking the low cost and earth abundant CuS as an example, we first fabricate ultrathin CuS layers, where temperature-dependent resistivities, valence-band spectrum and theoretical calculation affirm their metallic nature. Synchrotron-radiation photoelectron and ultraviolet-visible-near infrared spectra unveil metallic CuS atomic layers could realize a new cooperative intraband-interband transition under IR light irradiation, where the generated electrons and holes could simultaneously involve the carbon dioxide reduction and water oxidation reactions. As a result, CuS atomic layers exhibit nearly 100% selective CO production with an evolution rate of 14.5 μmol g-1 h-1 under IR light irradiation, while the catalytic performance shows no obvious decay after 96 h test. Briefly, benefiting from ultrahigh conductivity and unique partially occupied band, the abundant conductor materials such as conducting metal sulfides and metal nitrides hold great promise for applications as effective IR light responsive photocatalysts.
关键词： intraband-interband transition,ultrathin,CO2 reduction,conductor,IR light
更新于2025-09-04 15:30:14