arXiv subjects

Philippe Guyot-Sionnest

Publications and source records attributed to Philippe Guyot-Sionnest.

7 recordsLinked to original sources

arXiv2025

Mid-infrared intraband transitions in InAs colloidal quantum dots

III-V colloidal quantum dots are widely studied for their applications as detectors and emitters from visible to short-wave infrared. They might also be used in the mid-infrared if they can be stably n-doped to access their intraband transitions. Mid-infrared intraband transitions are therefore studied for InAs, InAs/InP, and InAs/ZnSe colloidal quantum dots with an energy gap at 1.4 micron. Using electrochemistry, the quantum dot films show state-resolved mobility, state-resolved electron filling, and intraband absorption in the 3-8 micron range. The InAs/ZnSe films need a more reducing potential than InAs, but the InAs/InP films need a lower reduction potential. As a result, we found that dry films of InAs/InP dots show stable n-doping of the 1Se state, with a steady-state intraband absorption in the 3-5 micron range, and intraband luminescence at 5 micron. low-toxicity, high thermal stability, and stable n-doping, InAs quantum dots become an interesting material for mid-infrared applications.

cond-mat.mtrl-sci↗

arXiv2023

Bright Fluorophores in the Second Near-Infrared Window: HgSe/CdSe Quantum Dots

Fluorophores emitting in the NIR-IIb wavelength range (1.5 micron - 1.7 micron) show great potential for bioimaging due to their large tissue penetration. However, current fluorophores suffer from poor emission with quantum yields ~2% in aqueous solvents. In this work, we report the synthesis of HgSe/CdSe core/shell quantum dots emitting at 1.7 microns through the interband transition. Growth of a thick shell led to a drastic increase in the photoluminescence quantum yield, with a value of 55% in nonpolar solvents. The quantum yields of our QDs and other reported QDs are explained well by a model of Forster resonance energy transfer to ligands and solvent molecules. The model predicts a quantum yield >6% when these HgSe/CdSe QDs are solubilized in water. Our work demonstrates the importance of a thick type-I shell to obtain bright emission in the NIR-IIb region

cond-mat.mtrl-sci↗

arXiv2020

Extrinsic Voltage Control of Carrier Lifetime in Polycrystalline PbSe Mid-wave IR Photo Detectors for Increased Detectivity

Polycrystalline PbSe for mid-wave IR (MWIR) photodetector is an attractive material option due to high operating/ambient temperature operation and relatively easy and cheap fabrication process, making it candidate for low-power and small footprint applications such as internet-of-thing (IoT) sensors and deployment on mobile platforms due to reduced/removed active cooling requirements. However, there are many material challenges that reduce the detectivity of these detectors. In this work, we demonstrate that it is possible to improve upon this metric by externally modulating the lifetime of conducting carriers by application of a back-gate voltage that can control the recombination rate of generated carrier. We first describe the physics of $PbSe$ detectors, the mechanisms underlying carrier transport, and long observed lifetimes of conducting carriers. We then discuss the voltage control of these inverted channels using a back-plane gate resulting in modulation of the lifetime of these carriers. This voltage control represents and extrinsic "knob" through which it may be possible to open a pathway for design of high performance IR photodetectors, as shown in this work.

physics.app-ph↗

arXiv2012

Transport properties of mid-infrared colloidal quantum dot films

The transport and thermal properties of HgTe colloidal quantum dot films with cut-off wavelengths in the mid-IR are investigated. The cut-off wavelength of this material can be tuned over the 3-5 μm range, which makes it a promising alternative to existing high cost detectors. Post deposition processes such as ligand exchange and atomic layer deposition are investigated as a way to increase the carrier mobility.

cond-mat.mes-hall↗

arXiv2006

Ultrafast resonant optical scattering from single gold nanorods: Large nonlinearities and plasmon saturation

We measure nonlinear optical scattering from individual Au nanorods excited by ultrafast laser pulses on resonance with their longitudinal plasmon mode. Isolating single rods removes inhomogeneous broadening and allows the measurement of a large nonlinearity, much greater than that of nanorod ensembles. Surprisingly, the ultrafast nonlinearity can be attributed entirely to heating of conduction electrons and does not exhibit any response associated with coherent plasmon oscillation. This indicates a previously unobserved damping of strongly driven plasmons.

cond-mat.mtrl-sci↗

arXiv2004

Characterizing Quantum-Dot Blinking Using Noise Power Spectra

Fluctuations in the fluorescence from macroscopic ensembles of colloidal semiconductor quantum dots have the spectral form of 1/f noise. The measured power spectral density reflects the fluorescence intermittency of individual dots with power-law distributions of "on" and "off" times, and can thus serve as a simple method for characterizing such blinking behavior.

cond-mat.mtrl-sci↗

arXiv2004

Variable range hopping conduction in semiconductor nanocrystal solids

The temperature and electrical field dependent conductivity of n-type CdSe nanocrystal thin films is investigated. In the low electrical field regime, the conductivity follows G ~ exp(-(T*/T)^0.5) in the temperature range 10K<T<120K. At high electrical field, the conductivity is strongly field dependent. At 4K, the conductance increases by eight orders of magnitude over one decade of bias. At very high field, conductivity is temperature-independent with G ~ exp(-(E*/E)^0.5). The complete behavior is very well described by variable range hopping with Coulomb gap.

cond-mat.mtrl-sci↗