Influence of TOPO and TOPO-CdSe/ZnS Quantum Dots on Luminescence Photodynamics of InP/InAsP/InPHeterostructure Nanowires

The passivation influence by ligands coverage with trioctylphosphine oxide (TOPO) and TOPO including colloidal CdSe/ZnS quantum dots (QDs) on optical properties of the semiconductor heterostructure, namely an array of InP nanowires (NWs) with InAsP nanoinsertion grown by Au-assisted molecular beam epitaxy on Si (111) substrates, was investigated. A significant dependence of the photoluminescence (PL) dynamics of the InAsP insertions on the ligand type was shown, which was associated with the changes in the excitation translation channels in the heterostructure. This change was caused by a different interaction of the ligand shells with the surface of InP NWs, which led to the formation of different interfacial low-energy states at the NW-ligand boundary, such as surface-localized antibonding orbitals and hybridized states that were energetically close to the radiating state and participate in the transfer of excitation. It was shown that the quenching of excited states associated with the capture of excitation to interfacial low-energy traps was compensated by the increasing role of the “reverse transfer” mechanism. As a result, the effectiveness of TOPO-CdSe/ZnS QDs as a novel surface passivation coating was demonstrated.

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Microcharacterization of Interfaces

MRS Proceedings ◽

10.1557/proc-18-7 ◽

1982 ◽

Vol 18 ◽

Author(s):

P. M. PETROFF

Keyword(s):

Phase Contrast ◽

Molecular Beam ◽

Minority Carrier ◽

Carrier Recombination ◽

Roughening Transition ◽

Semiconductor Heterostructure ◽

Transmission Electron ◽

Quantum Well Wire ◽

Interfacial Strain

The atomic structure of semiconductor heterostructure interfaces and metalsemiconductor interfaces are best characterized by transmission electron microscopy (TEM). Both phase contrast TEM and structure factor contrast TEM are able to distinguish very small structural (two monolayers) or compositional (less than 0.2%) fluctuations at interfaces. Applications of these techniques to the study of the roughening transition temperature at the Gal−xAlxAs–GaAs and Ga1−xAlxAs–Ge interfaces grown by molecular beam epitaxy are presented. Minority carrier recombination at interfaces is characterized on a microscopic scale by low temperature cathodoluminescence. This technique is used to demonstrate the role of interfaces in gettering defects in Gal1−xAlxAs/GaAs heterostructures. Finally, the effects of interfacial strain in producing a localization of the luminescence in GaAs quantum well wire structures will be discussed.

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Role of As in the Anisotropic Positioning of Self-Assembled InAs Quantum Dots

MRS Proceedings ◽

10.1557/opl.2013.892 ◽

2013 ◽

Vol 1551 ◽

pp. 3-9

Author(s):

Fabrizio Arciprete ◽

Ernesto Placidi ◽

Rita Magri ◽

Massimo Fanfoni ◽

Adalberto Balzarotti ◽

...

Keyword(s):

Quantum Dots ◽

Molecular Beam ◽

High Growth ◽

Inas Quantum Dots ◽

Potential Applications ◽

Gaas Buffer Layer ◽

Image Position ◽

Pulsed Deposition ◽

Deposition Mode

ABSTRACTProgress in tailoring the size, shape and positioning of Quantum Dots on the substrate is crucial for their potential applications in new optoelectronic devices for nano-photonics as well as in quantum information and computation. Using Molecular Beam Epitaxy in pulsed deposition mode we demonstrate that the nucleation of InAs Quantum Dots can be selectively guided on the GaAs(001) surface by a suitable choice of the kinetic parameters for the growth of both the GaAs buffer layer and the InAs Quantum Dots. By developing a two-species rate-equation kinetic model we show that the positioning of the Quantum Dots on only one side of mounds of the GaAs buffer can be traced back to the very small As flux gradient between the two mound slopes $\left( {\Delta F_A /F_A \approx 1 - 5\% } \right)$ caused by the proper tilting of the incoming As flux. Such gradient originates, at the relatively high growth-temperature, a net cation flow from one slope of the mound to the other that is responsible for the selective growth.

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Role of Excited States in Low-Energy Electron (LEE) Induced Strand Breaks in DNA Model Systems: Influence of Aqueous Environment

ChemPhysChem ◽

10.1002/cphc.200900025 ◽

2009 ◽

Vol 10 (9-10) ◽

pp. 1426-1430 ◽

Cited By ~ 39

Author(s):

Anil Kumar ◽

Michael D. Sevilla

Keyword(s):

Excited States ◽

Low Energy ◽

Energy Electron ◽

Model Systems ◽

Aqueous Environment ◽

Strand Breaks ◽

Low Energy Electron

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Influence of Surface Passivation on Perovskite CsPbBr1.2I1.8 Quantum Dots and Application of High Purity Red Light-Emitting Diodes

10.21203/rs.3.rs-796798/v1 ◽

2021 ◽

Author(s):

Lung-Chien Chen ◽

Yen-Hung Tien ◽

Jianjun Tian

Keyword(s):

Quantum Dots ◽

Surface Passivation ◽

Light Emitting Diode ◽

Red Light ◽

Lead Nitrate ◽

Luminous Efficiency ◽

Trioctylphosphine Oxide ◽

Light Emitting ◽

Co Doped

Abstract In this work, trioctylphosphine oxide (TOPO) ligand is employed to improve the quality of CsPbBr1.2I1.8 quantum dots (QDs) films. Lead nitrate (Pb(NO3)2) is also used to passivate the surface of the films. The study of ligand and surface passivation on the luminous efficiency of red light-emitting diode (LED) is discussed. The CsPbBr1.2I1.8 QDs films co-doped with TOPO and Pb(NO3)2 can effectively improve the performance of the CsPbBr1.2I1.8 QDs LEDs due to reduction of non-radiation recombination of the carriers and smooth morphology in the active layer, thus improving the injection and transportation capabilities of carriers. As a result, the highest luminosity and current efficiency are 502.7 cd/m2 and 0.175 cd/A, respectively.

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Optical and Electron Correlation Effects in Silicon Quantum Dots

Journal of Metastable and Nanocrystalline Materials ◽

10.4028/www.scientific.net/jmnm.23.129 ◽

2005 ◽

Vol 23 ◽

pp. 129-132 ◽

Cited By ~ 2

Author(s):

S.K. Ghoshal ◽

K.P. Jain ◽

R. Elliott

Keyword(s):

Quantum Dots ◽

Band Gap ◽

Surface Passivation ◽

Surface States ◽

Hydrogen Atoms ◽

Basis Expansion ◽

Electron Correlation Effects ◽

Homo Lumo ◽

Pseudo Potential

We study (through computer simulation) the variation of the band gap as a function of sizes and shapes of small Silicon (Si) dots using pseudo-potential approach. We have used empirical pseudo-potential Hamiltonian and a plane wave basis expansion and a basic tetrahedral structure. It is found that the gap decreases for increasing dot size. Furthermore, the band gap increases as much as 0.13eV on passivation the surface of the dot with hydrogen. So both quantum confinement and surface passivation determine the optical and electronic properties of Si quantum dots. Visible luminescence is probably due to radiative recombination of electrons and holes in the quantum confined nanostructures. The effect of passivation of the surface dangling bonds by hydrogen atoms and the role of surface states on the gap energy as well as on the HOMO-LUMO states has also been examined. We have investigated the entire energy spectrum starting from the very low lying ground state to the very high lying excited states for silicon dots having 5, 18, 17 and 18 atoms. The results for the size dependence of the HOMO-LUMO gap and the wave functions for the bonding-antibonding states are presented and the importance of the confinement and the role of hydrogen passivation on the confinement are also discussed.

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Role of Cation-Anion Organic Ligands for Optical Properties of Fully Inorganic Perovskite Quantum Dots

MRS Advances ◽

10.1557/adv.2018.552 ◽

2018 ◽

Vol 3 (55) ◽

pp. 3255-3261 ◽

Cited By ~ 4

Author(s):

Aaron Forde ◽

Talgat Inerbaev ◽

Dmitri Kilin

Keyword(s):

Quantum Dots ◽

Surface Passivation ◽

Binding Energies ◽

Organic Ligands ◽

Trap States ◽

Light Emitting ◽

Inorganic Perovskite ◽

Perovskite Quantum Dots ◽

Reasonable Choice

ABSTRACTApplication of lead-halide perovskite nanostructures for photovoltaic and light emitting applications depends on fashion of the surface termination. The reasonable choice of surface ligands for perovskite nanostructures prevent formation of trap states and contribute to chemical stability, wide opening of the bandgap, and intensity of absorption and photoluminescence of perovskite nanostructures. This work provides atomistic arguments for dual ligand protocol of surface passivation of fully inorganic perovskite quantum dots with fully organic ligands being a mix of cations (ethyl-ammonium) and anions (acetic) in nearly equal proportions. Computed binding energies of either individual ligands or anion-cation pairs demonstrate high stability in comparison to thermal energy and are concluded to be favourable choice in synthesis of colloidal perovskite quantum dots for light emitting applications.

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Optical properties of self-assembled InAs quantum dots grown on InAlAs/InP(001)

MRS Proceedings ◽

10.1557/proc-737-e9.5 ◽

2002 ◽

Vol 737 ◽

Cited By ~ 1

Author(s):

B. Salem ◽

T. Benyattou ◽

G. Guillot ◽

G. Bremond ◽

J. Brault ◽

...

Keyword(s):

Quantum Dots ◽

Excited States ◽

Molecular Beam ◽

Growth Parameters ◽

Exciton Dissociation ◽

Inas Quantum Dots ◽

Self Organized ◽

Component Spectrum ◽

Pl Intensity ◽

Lattice Matched

ABSTRACTSelf-organized InAs quantum islands (QIs) were grown in the Stranski-Krastanov regime, by solid source molecular beam epitaxy (SSMBE), on In0.52Al0.48As layer lattice matched to InP(001) substrate. The growth parameters are chosen to produce dot shaped InAs islands as indicated by the photoluminescence (PL) linear polarization which is about 9%. The PL spectrum reveals several resolvable components. PL versus power excitation and photoluminescence excitation (PLE) measurements show clearly that this multi-component spectrum is related to emission from transitions associated to fundamental and related excited states of quantum dots (QDs) having monolayer-height fluctuations. The integrated PL intensities have been measured as a function of temperature in the 8–300 K range. The PL intensity measured at 300K is only 8 times lower than at 8 K, indicating good carrier confinement in these InAs/InAlAs QDs. An enhancement of the PL intensity in the 8–90 K temperature range has been tentatively attributed to the exciton dissociation from the InAlAs barriers which then recombine radiatively in the InAs QDs.

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Carbon Doping into GaAs Using Low-Energy Hydrocarbon Ions

MRS Proceedings ◽

10.1557/proc-510-61 ◽

1998 ◽

Vol 510 ◽

Author(s):

Hirokazu Sanpei ◽

Takayuki Shima ◽

Yunosuke Makita ◽

Shinji Kimura ◽

Yasuhiro Fukuzawa ◽

...

Keyword(s):

Low Temperature ◽

Room Temperature ◽

Molecular Beam ◽

Ion Beam ◽

Low Energy ◽

Carbon Doping ◽

Co Doping ◽

Hall Effect Measurements ◽

Low Temperature Photoluminescence

AbstractThe role of hydrogen (H) in carbon (C)-doped GaAs was examined by co-doping of C and H atoms using low-energy hydrocarbon (CH+ and CH3+) ions. Experiments were carried out using the combined ion beam and molecular beam epitaxy (CIBMBE) system. Samples were characterized by low-temperature photoluminescence at 2K and Hall effect measurements at room temperature. Results show that incorporated C atoms are optically and electrically activated as acceptors even by hydrocarbon ion impingement. The effect of H incorporation was found to be noticeable when impinged current density of CH3+ ion beam is high that produces equivalent net hole carrier concentration greater than ∼1018 cm−3

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