Ultrafast Exciton Dynamics in Cd x Hg (1 − x ) Te alloy Quantum Dots

Leontiadou, Marina A.; Al-Otaify, Ali; Kershaw, Stephen V.; Zhovtiuk, Olga; Kalytchuk, Sergii; Mott, Derrick; Maenosono, Shinya; Rogach, Andrey L.; Binks, David J.

doi:10.1016/j.chemphys.2016.02.003

Cited by 11 publications

(9 citation statements)

References 42 publications

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“…Measuring the photoconductance signal as a function of light power, Figure e, we found that the photoconductance is weakly dependent on light intensity in this power range. Thus, assuming that the photocurrent has reached its maximum value, the relation I Photo = 2 e /τ enables to extract the lifetime τ ≈ 1.6 μs for the exciton in the QDot, assuming a current I Photo ≈ 0.2 pA at the drain voltage V Drain = 1 V. The lifetime for exciton recombination in mercury chalcogenide QDots is usually below 1 ns. , A lifetime of ≈1 μs usually suggests that deep traps are involved.…”

Section: Discussionmentioning

confidence: 99%

Transport in a Single Self-Doped Nanocrystal

Wang

Lhuillier

et al. 2017

ACS Nano

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Addressing the optical properties of a single nanoparticle in the infrared is particularly challenging, thus alternative methods for characterizing the conductance spectrum of nanoparticles in this spectral range need to be developed. Here we describe an efficient method of fabricating single nanoparticle tunnel junctions on a chip circuit. We apply this method to narrow band gap nanoparticles of HgSe, which band structure combine the inverted character of the bulk semimetal with quantum confinement and self-doping. Upon tuning the gate bias, measurement reveals the presence of two energy gaps in the spectrum. The wider gap results from the interband gap, while the narrower gap results from intraband transitions. The observation of the latter near zero gate voltage confirms the doped character of the nanoparticle at the single particle level, which is in full agreement with the ensemble optical and transport measurements. Finally we probe the phototransport within a single quantum dot and demonstrate a large photogain mechanism resulting from photogating.

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Section: Discussionmentioning

confidence: 99%

Transport in a Single Self-Doped Nanocrystal

Wang

Lhuillier

et al. 2017

ACS Nano

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“…The subnanosecond charge dynamics were studied using a home-built ultrafast transient absorption spectrometer, which has been reported previously. ,,, A Ti:sapphire regenerative amplifier (Spectra-Physics Spitfire-Pro) seeded by a mode-locked Ti:sapphire oscillator (Spectra-Physics Tsunami) produces pulses of 100 fs duration and ∼1 mJ energy at a wavelength of ∼800 nm and 1 kHz repetition rate. Using a beam splitter, 95% of this beam is passed to an optical parametric amplifier (OPA, Light Conversion Ltd. TOPAS-C) with harmonic generating crystals to produce the pump beam, tunable from the infrared to the ultraviolet with a minimum wavelength of 232 nm.…”

Section: Methodsmentioning

confidence: 99%

“…MEG in CQDs was first proposed in 2001 and first experimentally demonstrated in 2005 for PbSe CQDs . Since then MEG has been demonstrated in CQDs composed of a range of single materials, including PbS, HgTe, CdHgTe, and CuInSe 2 , as well as in other forms of colloidal nanostructures such as PbSe nanorods and PbS nanosheets . One of the most useful aspects of the solution-phase synthesis of CQDs is that it allows a core–shell structure to be readily produced by the growth of a shell or shells of different material(s) around the original CQD.…”

Section: Introductionmentioning

confidence: 99%

Multiple Exciton Generation and Dynamics in InP/CdS Colloidal Quantum Dots

et al. 2017

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We report measurements of multiple exciton generation and recombination in InP/CdS (core/shell) colloidal quantum dots. Ultrafast transient absorption spectroscopy was used to measure the sub-nanosecond charge dynamics for a range of pump fluences and for different pump photon energies. Analysis of the resulting transients was used to determine the quantum yield of multiple exciton generation, which was found to be 1.22 ± 0.01 for a pump photon energy equivalent to three times the band gap.

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“…Guyot-Sionnest et al have shown that the separation of electron and hole wave functions and surface ligands can modified the intraband relaxation rate from the 1P(e) state to the 1S(e) state . The exciton dynamics of Cd x Hg 1– x Te alloy quantum dots in ultrafast time scale has been investegated by Binks and his co-worker . We have recently investigated the excited state dynamics of Cd x Zn 1– x S nanocrystal in nanosecond time scale and evaluate the radiative and nonradiative relaxation channel depending upon the lattice strain of NCs.…”

Section: Introductionmentioning

confidence: 99%

“…20 The exciton dynamics of Cd x Hg 1−x Te alloy quantum dots in ultrafast time scale has been investegated by Binks and his co-worker. 21 We have recently investigated the excited state dynamics of Cd x Zn 1−x S nanocrystal in nanosecond time scale and evaluate the radiative and nonradiative relaxation channel depending upon the lattice strain of NCs. Still it is not clear how the crystal defect and lattice strain influence the trapping process, which eventually controls the nonradiative relaxation processes.…”

Section: ■ Introductionmentioning

confidence: 99%

Identification of Nonradiative Relaxation Processes in Alloy Nanocrystals

et al. 2020

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Luminescent colloidal nanocrystals (NCs) are extensively used in optoelectronics, light harvesting, and imaging, depending on their efficiency. The efficiency of these nanocrystals depends on radiative and nonradiative processes, which can be altered by crystal phase, nature of ligand, lattice strain, surface defects, etc. Herein, we investigate the role of crystal defects and the lattice strain on nonradiative relaxation processes of pure CdS and Cd x Zn 1−x S alloy NCs with changing compositions. Rietveld analysis reveals the presence of biphases in pure CdS NCs that influence the nonradiative relaxation process due to the trap states whereas the nonradiative relaxation process of alloy nanocrystals is controlled by the lattice strain developed in alloy NCs. The significant change in the hot electron cooling dynamics from 400 to <120 fs is obtained from pure to alloy QDs. It is seen that the nonradiative relaxation due to lattice strain follows in the order CdS < Cd 0.8 Zn 0.2 S < Cd 0.75 Zn 0.25 S < Cd 0.67 Zn 0.33 S whereas the nonradiative relaxation due to the crystal defect follows in the order CdS > Cd 0.8 Zn 0.2 S > Cd 0.75 Zn 0.25 S > Cd 0.67 Zn 0.33 S. Thus, both of the nonradiative processes are important to understand because they have significant influence on the ultrafast relaxation process, and this knowledge is beneficial for fabricating efficient optoelectronic devices.

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Ultrafast Exciton Dynamics in Cd x Hg (1 − x ) Te alloy Quantum Dots

Cited by 11 publications

References 42 publications

Transport in a Single Self-Doped Nanocrystal

Transport in a Single Self-Doped Nanocrystal

Multiple Exciton Generation and Dynamics in InP/CdS Colloidal Quantum Dots

Identification of Nonradiative Relaxation Processes in Alloy Nanocrystals

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