Fluorescence spectral shift of QD films with electron injection: Dependence on counterion proximity
4
Citation
24
Reference
10
Related Paper
Citation Trend
Keywords:
Blueshift
Stokes shift
Blueshift
Optical spectra
Line (geometry)
Cite
Citations (9)
Blueshift
Red shift
Cite
Citations (1)
The exciton-exciton interaction energy of tellurium doped CdSe colloidal quantum dots is experimentally investigated. The dots exhibit a strong Coulomb repulsion between the two excitons, which results in a huge measured biexciton blue shift of up to 300 meV. Such a strong Coulomb repulsion implies a very narrow hole wave function localized around the defect, which is manifested by a large Stokes shift. Moreover, we show that the biexciton blue shift increases linearly with the Stokes shift. This result is highly relevant for the use of colloidal QDs as optical gain media, where a large biexciton blue shift is required to obtain gain in the single exciton regime.
Biexciton
Blueshift
Stokes shift
Tellurium
Cite
Citations (56)
The evolution of the optical absorption and emission properties of strained Ga1−xInxN/GaN double quantum wells grown on (0001)-oriented sapphire substrates with varying well width has been investigated by spectroscopic ellipsometry (SE) and photoluminescence (PL). The SE result shows that the band-gap absorption energy of the wells shifts to higher energies as the well width decreases, indicating a quantum-confinement effect. The decreasing trend agrees with the result of one-dimensional square-well potential calculations. The PL result shows a Stokes shift of the emission edge from the corresponding absorption edge, attributable to the combined effects of the strain-induced piezoelectric potential and the In-fluctuation potential in the well. The blueshift of the emission edge with increasing PL excitation density further supports the existence of a strong piezoelectric field in the well.
Blueshift
Stokes shift
Absorption edge
Ellipsometry
Wide-bandgap semiconductor
Cite
Citations (6)
Cite
Citations (12)
A large, rigid downward shift of excitonic luminescence peak energies was observed with increasing transverse electric field in tensilely strained Si1−yCy/Si(001) symmetric quantum wells, as opposed to theoretical calculations predicting a blueshift due to exciton weakening, which more than balances the redshift due to quantum-confined Stark effects. The observed anomalies are interpreted in terms of field-enhanced Stokes shifts which occur due to carrier relaxation in an inhomogeneously distributed potential of the grown-in Si1−yCy/Si interfaces.
Blueshift
Stokes shift
Quantum-confined Stark effect
Cite
Citations (2)
The e.s.r. spectrum of the 4,5-methylenephenanthrene dianion radical has been studied with particular interest in the variation of the alkali-metal splitting constant with the nature of the solvent, the nature of the counterion, and temperature. The results may be interpreted in terms of interaction of the unpaired electron with one counterion only. The results also indicate that a variety of environments are possible for the counterion in the 'contact' ion pair and that in particular cases an equilibrium is also present in which this counterion is in a 'solvent-separated' environment. Interaction of the unpaired electron with the second counterion is not observed and is probably due to a solvent separated environment for this counterion.
Unpaired electron
Cite
Citations (4)
We have studied the effects of various conditions of rapid thermal annealing (RTA) on 10nm GaInNAs∕GaAs single quantum wells (SQWs) with fixed indium concentration and increasing nitrogen content to obtain photoluminescence (PL) in the telecom wavelength regime of 1.3 and 1.5μm. Specifically, we analyzed the results of annealing for a fixed short time but at different temperatures and for longer times at a fixed temperature. In all experiments, InGaAs SQWs with the same In concentration were used as references. For both RTA conditions, the well-known blueshift of the band gap energy and the PL intensity improvement show trends that reveal that these are unrelated effects. At high RTA temperatures the PL efficiency reaches a maximum and then drops independently of N content. On the contrary, the blueshift experiences a rapid increase up to 700°C (strong blueshift regime) and it saturates above this temperature (weak blueshift regime). Both these blueshift regimes are related to the nitrogen content in the SQWs but in different ways. In the strong blueshift regime, we could obtain activation energy for the blueshift process in the range of 1.25eV, which increases with N content. Analysis with high-resolution x-ray diffraction (HRXRD) shows that the blueshift experienced in this regime is not due to a stoichiometric change in the QW. In the weak blueshift regime, the blueshift, which is only partly due to In outdiffusion, saturates more slowly the higher the N content. Annealing at the same temperature (600°C) for a longer time shows that the blueshift saturates earlier than the PL intensity and that samples with higher nitrogen experience a larger blueshift. Only a small In outdiffusion for annealing at high temperatures (>650°C) and long duration was observed. However, this modest stoichiometric change does not explain the large blueshift experienced by the GaInNAs SQWs. We conclude that the mechanism responsible for the drastic blueshift after annealing is related to the N content in the QW, while the improvement in PL integrated intensity is uniquely related to the annealing conditions.
Blueshift
Cite
Citations (17)
We have studied luminescence Stokes shift and phonon-assisted luminescence in H-terminated and surface-oxidized Si nanocrystals by means of resonant excitation spectroscopy. For resonant excitation at energies within a broad luminescence band, TO- and TA-phonon related structures in luminescence spectra are observed in both H-terminated and surface-oxidized Si nanocrystals. In oxidized Si nanocrystals, the luminescence Stokes shift is large and the phonon-related structures are unclear compared to the case of H-terminated Si nanocrystals. The origin of the luminescence Stokes shift and surface localized states in surface-oxidized Si nanocrystals are discussed.
Stokes shift
Cite
Citations (59)
The vibrational Stokes shift of the OH stretching transition nu(OH) of water is the shift between the ground-state absorption and the excited-state (v=1) emission. A recent measurement on HOD in D(2)O solvent [S. Woutersen and H. J. Bakker, Phys. Rev. Lett. 83, 2077 (1999)] of a 70 cm(-1) redshift, and a subsequent calculation of a 57 cm(-1) redshift using equilibrium molecular dynamics simulations [C. P. Lawrence and J. L. Skinner, J. Chem. Phys. 117, 8847 (2002)] were in good agreement. We now report extensive measurements of the vibrational Stokes shift in HOD/D(2)O using an ultrafast IR pump, Raman probe method. The vibrational Stokes shift is seen to depend on the pump pulse frequency and on time delay; by varying these parameters it can be made to range from 112 to -32 cm(-1) (negative values indicate a blueshift in the excited state). The equilibrium vibrational Stokes shift is actually a negative rather than a positive quantity. Possible reasons for the disagreement between experiment and theory are briefly discussed.
Stokes shift
Blueshift
Cite
Citations (27)