Search results for "combination"
showing 10 items of 1379 documents
Near band edge recombination mechanisms in GaTe
2003
GaTe samples of p-type have been investigated by analyzing the photoluminescence (PL) response for different excitation intensities at energies higher than the band gap. The PL intensity variation of recombination peaks as a function of the excitation intensity has been measured and fitted by a power law. The results show some particular features that do not appear in other III-V and II-VI compound semiconductors. These features can be interpreted by means of the recombination dynamics of the carriers in the band-gap edges. The expressions for the coefficients associated with different recombination rates and the relations between them are derived and used for understanding the recombinatio…
Photoluminescence of Ga-face AlGaN/GaN single heterostructures
2001
Abstract The radiative recombination in Ga-face Al 0.30 Ga 0.70 N/GaN single heterostructures (SHs) was studied by photoluminescence (PL) measurements. An energy shift of the excitonic transitions toward higher energies was observed, indicating the presence of residual compressive strain in the GaN layer. In addition to these exciton lines, a broad band energetically localized between the exciton lines and the LO-phonon replica was noticed in the undoped SH. From its energy position, excitation power dependence, as well as temperature behaviour, we have attributed this luminescence to the H -band (HB), which is representative of the two-dimensional electron gas (2DEG) recombination.
Nature of the blue luminescence bands in PbWO4
1997
Abstract The photoluminescence spectrum of PbWO 4 is composed of blue and green bands, previously attributed to the regular WO 4 group and to the defect-related WO 3 group, respectively. Untill now only green emission was observed in the thermostimulated luminescence (TSL) above 77 K. Investigation of the TSL spectra starting from 20 K indicates that the blue band, being definitely present at least in the 28 K TSL peak, is also due to recombination emission at defect sites.
Two-Color Single-Photon Emission from In As Quantum Dots: Toward Logic Information Management Using Quantum Light
2014
In this work, we propose the use of the Hanbury-Brown and Twiss interferometric technique and a switchable two-color excitation method for evaluating the exciton and noncorrelated electron-hole dynamics associated with single photon emission from indium arsenide (InAs) self-assembled quantum dots (QDs). Using a microstate master equation model we demonstrate that our single QDs are described by nonlinear exciton dynamics. The simultaneous detection of two-color, single photon emission from InAs QDs using these nonlinear dynamics was used to design a NOT AND logic transference function. This computational functionality combines the advantages of working with light/photons input/output device…
Characterization of PTW-31015 PinPoint ionization chambers in photon and proton beams
2018
The increased use of complex forms of radiotherapy using small-field photon and proton beams has invoked a growing interest in the use of micro-ionization chambers. In this study, 48 PTW-TM31015 PinPoint-type micro-ionization chambers that are used in the commissioning and patient specific QA of a proton pencil beam scanning (PBS) delivery system have been characterized in proton and high-energy photon beams. In both beam modalities, the entire set of PinPoint chambers was characterized by imaging them, by evaluating their stability using check source measurements, by experimentally determining the ion recombination, polarity effect and by cross calibrating them in terms of absorbed dose to…
Quasimolecular luminescence centers formed by photoinduced recombination of exciton-created defects in KI
1995
Abstract The photoinduced recombination of exciton-created lattice defects - the F,H center pairs was studied in KI crystal at low temperatures. Two different luminescence centers with quasimolecular structure can be distinguished. One of them is the self-trapped exciton, the other one could be the H-plus-electron (H+e) center.
Temperature dependence of the effective mobility edge and recombination dynamics of free and localized excitons in InGaP/GaAs quantum wells
2003
3 páginas, 1 figura.-- Comunicación presentada al Proceedings of the International Conference on Superlattices, Nano-structures and Nano-devices ICSNN 2002 o-structures and Nano-devices ICSNN 2002.
First-principles LCAO study of phonons in NiWO4
2011
Abstract The electronic, structural and phonon properties of antiferromagnetic wolframite-type NiWO4 have been studied using first-principles spin-polarized LCAO calculations based on the hybrid Hartree-Fock (HF)/density functional (DFT) scheme. The influence of different percentages of HF contribution, i.e. different correlation strength, on the structure and phonon frequencies has been investigated and compared with the available experimental data.
Quantum chemical modelling of "green" luminescence in ABO $ \mathsf {_3}$ perovskites
2002
The origin of the intrinsic excitonic (“green”) luminescence in ABO3 perovskites remains a hot topic over the last quarter of a century. We suggest as a theoretical interpretation for the “green” luminescence in these crystals, the recombination of electron and hole polarons forming a charge transfer vibronic exciton. In order to check quantitatively the proposed model, we performed quantum chemical calculations using the Intermediate Neglect of Differential Overlap (INDO) method combined with the periodic defect model. The luminescence energies calculated for four perovskite crystals are found to be in good agreement with experimental data.
The effect of reducing dimensionality on the excitonic recombination in InAs/InP heterostructures
1997
In this work we study the exciton recombination of InAs/InP self-organized quantum dots by means of photolumincscence (PL) as a function of temperature and excitation density. Well defined islands, spatially separated in most cases, and with different size distribution, make localized exciton recombination the dominant contribution to the PL spectrum. From our experimental results, we propose the co-existence of two types of islands, one with small height whose contribution to the PL spectra is important in samples with low InAs coverage (below two monolayers), and the properly 3D islands, whose dimensions and sheet concentration increase with the InAs coverage. Good quality structures are …