Search results for "QUANTUM DOT"
showing 10 items of 418 documents
Reduced efficiency roll-off in light-emitting diodes enabled by quantum dot–conducting polymer nanohybrids
2014
We demonstrate QLEDs implementing wider active layers (50 nm) based on QD–conducting polymer nanohybrids, which exhibit a stable operational device performance across a wide range of current densities and brightness. A comparative study reveals that the significant suppression of efficiency roll-off in the high current density regime is primarily attributed to a sufficient charge carrier distribution over the wider active layer and improved charge carrier balance within QDs enabled by the hybridization of QDs with conducting polymers. Utilization of this finding in future studies should greatly facilitate the development of high performance, stable QLEDs at high current density or luminance…
Memory effects in single-electron nanostructures
2001
We investigate the memory function at room temperature in devices based on quantum dots. By Low Pressure Chemical Vapour Deposition (LPCVD) we deposited Si dots embedded in SiO2. On these devices flat band voltage shifts were well detected at low write voltages for write times of the order of milliseconds, and furthermore, a plateau in the flat band voltage shift, maybe consequence of Coulomb blockdale, was observed.
Exact Coulomb cutoff technique for supercell calculations in two dimensions
2009
We present a reciprocal space technique for the calculation of the Coulomb integral in two dimensions in systems with reduced periodicity, i.e., finite systems, or systems that are periodic only in one dimension. The technique consists in cutting off the long-range part of the interaction by modifying the expression for the Coulomb operator in reciprocal space. The physical result amounts in an effective screening of the spurious interactions originated by the presence of ghost periodic replicas of the system. This work extends a previous report [C. A. Rozzi et al., Phys. Rev. B 73, 205119 (2006)], where three-dimensional systems were considered. We show that the use of the cutoffs dramatic…
Frequency conversion of propagating surface plasmon polaritons by organic molecules
2008
We demonstrate frequency conversion of surface plasmon polaritons (SPP) by utilizing the coupling between organic dye molecules and SPP. Launching of SPPs into a plasmonic waveguide is done in two ways: by optically excited molecules and by quantum dots (QDs). QDs are demonstrated to overcome the major problem of bleaching occurring with molecules. The SPP propagates tens of micrometers and clear frequency conversion is observed in the SPP spectrum after passing an area of converter molecules. The use of molecules and QDs as elements of all-plasmonic devices has the potential for high integration and use of self-assembly in fabrication. Peer reviewed
All-Optical Fiber Hanbury Brown & Twiss Interferometer to study 1300 nm single photon emission of a metamorphic InAs Quantum Dot
2016
[EN] New optical fiber based spectroscopic tools open the possibility to develop more robust and efficient characterization experiments. Spectral filtering and light reflection have been used to produce compact and versatile fiber based optical cavities and sensors. Moreover, these technologies would be also suitable to study N-photon correlations, where high collection efficiency and frequency tunability is desirable. We demonstrated single photon emission of a single quantum dot emitting at 1300 nm, using a Fiber Bragg Grating for wavelength filtering and InGaAs Avalanche Photodiodes operated in Geiger mode for single photon detection. As we do not observe any significant fine structure s…
Size dependent carrier thermal escape and transfer in bimodally distributed self assembled InAs/GaAs quantum dots
2012
We have investigated the temperature dependent recombination dynamics in two bimodally distributed InAs self assembled quantum dots samples. A rate equations model has been implemented to investigate the thermally activated carrier escape mechanism which changes from exciton-like to uncorrelated electron and hole pairs as the quantum dot size varies. For the smaller dots, we find a hot exciton thermal escape process. We evaluated the thermal transfer process between quantum dots by the quantum dot density and carrier escape properties of both samples. © 2012 American Institute of Physics.
Continuous-Variable Tomography of Solitary Electrons
2019
A method for characterising the wave-function of freely-propagating particles would provide a useful tool for developing quantum-information technologies with single electronic excitations. Previous continuous-variable quantum tomography techniques developed to analyse electronic excitations in the energy-time domain have been limited to energies close to the Fermi level. We show that a wide-band tomography of single-particle distributions is possible using energy-time filtering and that the Wigner representation of the mixed-state density matrix can be reconstructed for solitary electrons emitted by an on-demand single-electron source. These are highly localised distributions, isolated fro…
Unconventional Fluorescence Quenching in Naphthalimide-Capped CdSe/ZnS Nanoparticles
2013
Core–shell (CS) CdSe/ZnS quantum dots (QD) capped with ligands that possess a mercapto or an amino group and a naphthalimide (NI) as chromophore unit, linked by a short ethylene chain (CS@S–NI and CS@H2N–NI, respectively), have been synthesized and fully characterized by infrared and nuclear magnetic resonance spectroscopies, high-resolution transmission electron microscopy, and voltammetry as well as by steady-state absorption and emission spectroscopies. The organic ligands HS–NI and H2N–NI act as bidentate ligands, thereby causing a drastic decrease in the QD emission. This was particularly evident in the case of CS@S–NI. This behavior has been compared with that of commercially availabl…
Entanglement dynamics of two independent cavity-embedded quantum dots
2010
We investigate the dynamical behavior of entanglement in a system made by two solid-state emitters, as two quantum dots, embedded in two separated micro-cavities. In these solid-state systems, in addition to the coupling with the cavity mode, the emitter is coupled to a continuum of leaky modes providing additional losses and it is also subject to a phonon-induced pure dephasing mechanism. We model this physical configuration as a multipartite system composed by two independent parts each containing a qubit embedded in a single-mode cavity, exposed to cavity losses, spontaneous emission and pure dephasing. We study the time evolution of entanglement of this multipartite open system finally …
Enhanced nanoscopy of individual CsPbBr3 perovskite nanocrystals using dielectric sub-micrometric antennas
2020
We demonstrate an efficient, simple, and low-cost approach for enhanced nanoscopy in individual green emitting perovskite (CsPbBr3) nanocrystals via TiO2 dielectric nanoantenna. The observed three- to five-fold emission enhancement is attributed to near-field effects and emission steering promoted by the coupling between the perovskite nanocrystals and the dielectric sub-micrometric antennas. The dark-field scattering configuration is then exploited for surface-enhanced absorption measurements, showing a large increase in detection sensitivity, leading to the detection of individual nanocrystals. Due to the broadband spectral response of the Mie sub-micrometric antennas, the method can be e…