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Distinctive characteristics of carrier-phonon interactions in optically driven semiconductor quantum dots
摘要： We review distinct features arising from the unique nature of the carrier-phonon coupling in self-assembled semiconductor quantum dots. Because of the discrete electronic energy structure, the pure dephasing coupling usually dominates the phonon effects, of which two properties are of key importance: The resonant nature of the dot-phonon coupling, its non-monotonic behavior as a function of energy, and the fact that it is of super-Ohmic type. Phonons do not only act destructively in quantum dots by introducing dephasing, they also offer new opportunities, e.g. in state preparation protocols. Apart from being an interesting model systems for studying fundamental physical aspects, quantum dot and quantum dot-microcavity systems are a hotspot for many innovative applications. We discuss recent developments related to the decisive impact of phonons on key figures of merit of photonic devices like single or entangled photon sources under aspects like indistinguishability, purity and brightness. All in all it follows that understanding and controlling the carrier-phonon interaction in semiconductor quantum dots is vital for their usage in quantum information technology.
关键词： Non-Markovian dynamics,quantum information processing,optical manipulation,Semiconductor quantum dots,carrier-phonon interaction,photonics
更新于2025-09-12 10:27:22
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F?rster Resonance Energy Transfer between Colloidal CuInS2/ZnS Quantum Dots and Dark Quenchers
摘要： F?rster resonance energy transfer (FRET) using colloidal semiconductor quantum dots (QDs) and dyes is of importance in a wide range of biological and biophysical studies. Here, we report a study on FRET between CuInS2/ZnS QDs and dark quencher dye molecules (IRDye QC-1). Oleate-capped QDs with photoluminescence quantum yields (PLQYs) of 55±4% are transferred into water by using two types of multifunctional polymer ligands combining imidazole groups and specific moieties with amine or methoxy groups as the terminal sites. The resulting water-dispersible QDs show PLQYs as high as 44±4% and exhibit long-term colloidal stability (at least 10 months at 4 °C in the dark) with a hydrodynamic diameter of less than 20 nm. A side-by-side comparison experiment was performed using the amine or methoxy-functionalized QDs for coupling to dark quencher dye molecules. The amine-functionalized QDs bind to the dye molecules via covalent bonds while methoxy-functionalized ones bind only weakly and non-specifically. The progressive quenching of the QD emission and shortening of its photoluminescence decay time upon increasing the number of conjugated dye molecules demonstrate that the QD acts as the energy donor and the dark quencher dye as the energy acceptor in a donor-acceptor FRET pair. The FRET dynamics of the QD-dye conjugates are simulated using two different models based on the possible origin of the multiexponential PL decay of the QDs (i.e., variations in nonradiative or radiative decay rates). The model based on the radiative decay rates provides a better fit of our experimental data and estimates a donor–acceptor distance (6.5 nm) that matches well the hydrodynamic radius of the amine-functionalized QDs.
关键词： dark quencher dye molecules,energy acceptor,multifunctional polymer ligands,CuInS2/ZnS,F?rster resonance energy transfer,colloidal semiconductor quantum dots,energy donor,photoluminescence quantum yields
更新于2025-09-12 10:27:22
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Facile one-pot synthesis of gold/tin oxide quantum dots for visible light catalytic degradation of methylene blue: Optimization of plasmonic effect
摘要： Discovery and development of novel photocatalysts with superior performance in visible light is a fundamental step toward tackling several environment and energy related issues. In this study, a simple one-pot solvothermal approach was adopted to fabricate a series of novel SnO2 quantum dot/gold (SQD/Au) nanocomposites. The structure, morphology, chemical composition, and the optical and photocatalytic performance of the as-prepared SQD/Au nanocomposites were described. The dispersion of Au nanoparticles (NPs) over SQDs can significantly improve the synergistic charge transfer mechanism, which retards the reunion of photoinduced electron-hole pairs and results in decreased emission intensity. In particular, the SQD/Au nanocomposites with 1.00 mL in 100 mM gold chloride loading achieve a methylene blue (MB) degradation of 99% under visible light illumination within 150 min. This can be ascribed to the plasmonic effect of Au NPs in the visible region and the SQDs acting as an electron tank to receive the photoinduced electrons. Furthermore, the formation of a Schottky barrier between SQDs and Au NPs improved the charge separation efficiency, and enhanced the photocatalytic activity. A possible photocatalytic mechanism for the improved degradation efficiency of MB by SQD/Au nanocomposites is also proposed.
关键词： Photocatalysis,SnO2,Metal-semiconductor,Quantum dots,Plasmonic effect
更新于2025-09-12 10:27:22
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A Method for Estimating the Functionality of TiO2/Quantum Dot Multilayer Hybrid Structures Based on the Generation of Reactive Oxygen Species
摘要： A new technique for estimating the efficiency of electron transfer from a CdSe/ZnS quantum dot (QD) to TiO2 nanoparticles based on the generation of reactive oxygen species by hybrid structures is presented. It was demonstrated that in the formed multilayer hybrid structures of TiO2/QD, photoinduced electron transfer is realized with an efficiency of 26%.
关键词： hybrid structures,photoinduced electron transfer,semiconductor quantum dots,titanium dioxide nanoparticles,reactive oxygen species
更新于2025-09-12 10:27:22
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Tuning the optical properties of CdSe quantum dot using graphene nanocomposite
摘要： Graphene semiconductor quantum dots (G-QDs) nanocomposites have attracted a lot of scienti?c interest. They have promising properties which allow them to be a good choice for photoelectric devices. G-QDs nanocomposites are prepared chemically by thermal decomposition of organometallic complex. Synthesis procedures were performed in the absence and presence of graphene in order to study its in?uence on the optical properties of the quantum dots (QDs) precisely. Various experimental techniques were utilized to study the morphology, crystal structure and the optical properties of the as-prepared materials using X-ray diffraction, Fourier transform infrared spectroscopy, transmission electron microscopy and UV/visible spectrophotometer. This paper will discuss the coupling between graphene and QDs showing the quenching of QDs emission, slowing rate of particle growth, increasing stock shift and enhancing the particle size distribution.
关键词： Semiconductor quantum dots,QDs emission,G-QDs nanocomposites
更新于2025-09-12 10:27:22
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GaAs Quantum Dot in a Parabolic Microcavity Tuned to <sup>87</sup> Rb D <sub/>1</sub>
摘要： We develop a structure to efficiently extract photons emitted by a GaAs quantum dot tuned to Rubidium. For this, we employ a broadband microcavity with a curved gold backside mirror which we fabricate by a combination of photoresist reflow, dry reactive ion etching in an inductively coupled plasma and selective wet chemical etching. Precise reflow and etching control allows us to achieve a parabolic backside mirror with a short focal distance of 265 nm. The fabricated structures yield a predicted (measured) collection efficiency of 63 % (12 %), an improvement by more than one order of magnitude compared to unprocessed samples. We then integrate our quantum dot parabolic microcavities onto a piezoelectric substrate capable of inducing a large in-plane biaxial strain. With this approach, we tune the emission wavelength by 0.5 nm/kV, in a dynamic, reversible and linear way, to the Rubidium D1 line (795 nm).
关键词： two-photon resonance fluorescence,strain tuning,microcavity,single-photon source,extraction efficiency,semiconductor quantum dots
更新于2025-09-12 10:27:22
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Wavelength-Tunable Band-Edge Photoluminescence of Nonstoichiometric Ag–In–S Nanoparticles via Ga <sup>3+</sup> Doping
摘要： The nonstoichiometry of I?III?VI semiconductor nanoparticles, especially the ratio of group I to group III elements, has been utilized to control their physicochemical properties. We report the solution-phase synthesis of non-stoichiometric Ag?In?S and Ag?In?Ga?S nanoparticles and results of the investigation of their photoluminescence (PL) properties in relation to their chemical compositions. While stoichiometric AgInS2 nanoparticles simply exhibited only a broad PL band originating from defect sites in the particles, a narrow band edge PL peak newly appeared with a decrease in the Ag fraction in the nonstoichiometric Ag?In?S nanoparticles. The relative PL intensity of this band edge emission with respect to the defect-site emission was optimal at a Ag/(Ag + In) value of ca. 0.4. The peak wavelength of the band edge emission was tunable from 610 to 500 nm by increased doping with Ga3+ into Ag?In?S nanoparticles due to an increase of the energy gap. Furthermore, surface coating of Ga3+-doped Ag?In?S nanoparticles, that is, Ag?In?Ga?S nanoparticles, with a GaSx shell drastically and selectively suppressed the broad defect-site PL peak and, at the same time, led to an increase in the PL quantum yield (QY) of the band edge emission peak. The optimal PL QY was 28% for Ag?In?Ga?S@GaSx core?shell particles, with green band-edge emission at 530 nm and a full width at half-maximum of 181 meV (41 nm). The observed wavelength tunability of the band-edge PL peak will facilitate possible use of these toxic-element-free I?III?VI-based nanoparticles in a wide area of applications.
关键词： band-edge photoluminescence,multinary semiconductor,quantum dots,nonstoichiometry,I?III?VI2 semiconductor,visible photoluminescence,wavelength tunability,semiconductor nanocrystals
更新于2025-09-10 09:29:36
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A fast quantum interface between different spin qubit encodings
摘要： Single-spin qubits in semiconductor quantum dots hold promise for universal quantum computation with demonstrations of a high single-qubit gate fidelity above 99.9% and two-qubit gates in conjunction with a long coherence time. However, initialization and readout of a qubit is orders of magnitude slower than control, which is detrimental for implementing measurement-based protocols such as error-correcting codes. In contrast, a singlet-triplet qubit, encoded in a two-spin subspace, has the virtue of fast readout with high fidelity. Here, we present a hybrid system which benefits from the different advantages of these two distinct spin-qubit implementations. A quantum interface between the two codes is realized by electrically tunable inter-qubit exchange coupling. We demonstrate a controlled-phase gate that acts within 5.5 ns, much faster than the measured dephasing time of 211 ns. The presented hybrid architecture will be useful to settle remaining key problems with building scalable spin-based quantum computers.
关键词： spin qubits,quantum computation,controlled-phase gate,semiconductor quantum dots,singlet-triplet qubit
更新于2025-09-10 09:29:36
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Cryogenic Characterization of 22nm FDSOI CMOS Technology for Quantum Computing ICs
摘要： An approach is proposed to realize large-scale, “high-temperature” and high-fidelity quantum computing ICs based on single- and multiple coupled quantum-dot electron- and hole-spin qubits monolithically integrated with the mm-wave spin manipulation and readout circuitry technology. Measurements of minimum-size 6nmx20nmx80nm Si-channel n-MOSFETs (electron-spin qubit), SiGe-channel p-MOSFETs (hole-spin qubit), and double quantum-dot complementary qubits reveal strong quantum effects in the subthreshold region at 2 K, characteristic of resonant tunneling in a quantum dot. S-parameter measurements of a transimpedance amplifier (TIA) for spin readout show improved performance from 300 K to 2 K. Finally, the qubit-with-TIA circuit has 50Ω output impedance, 78dBΩ transimpedance gain with unity-gain bandwidth of 70 GHz and consumes 3.1 mW.
关键词： CMOS,silicon-on-insulator,quantum information processing,radio frequency,monolithic integrated circuits,semiconductor quantum dots,silicon,cryogenics
更新于2025-09-10 09:29:36