Exciton photoluminescence and energy in a percolation cluster of ZnSe quantum dots as a fractal object

Bondar, N. V.; Brodyn, M. S.

doi:10.1134/s1063782612050090

Cited by 2 publications

(2 citation statements)

References 17 publications

(67 reference statements)

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“…It has to be noted that, if the exciton size effect is preserved, it is rather difficult to determine the exact moment of percolation threshold formation in an array of QDs and their critical concentration (or the coverage degree of the surface area). It can be done more easily in 3D structures with QDs, where the formation of this threshold was registered in PL spectra [14]. As a rule, the percolation manifests itself in the disappearance of the exciton size effect and a change to the radiation emission of the system from the bulk phase.…”

Section: Exciton Size Effect Feature In Sparse Arrays Of Quantum Dots...mentioning

confidence: 99%

Quantum-Size Effect and Exciton Percolation in Porous and Disordered Films on the Basis of Spherical “Core/Shell” Elements

2015

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The results of spectroscopic researches of porous and disordered films fabricated on the basis of spherical elements of the "core/shell" type, SiO2/CdS nanoparticles (SiO2 spheres covered with CdS quantum dots) are reported. The quantum-size effect of excitons in the quantum dots located on the surface of spheres is found to depend on the sphere size and to weakly depend on the quantum dot radius, which results from the quantization of the exciton motion normally to the sphere surface. The quantization survives, even if the sphere coverage exceeds the exciton percolation threshold. To evaluate the latter in the film plane and to determine the critical concentration of SiO2/CdS nanoparticles, a number of specimens on the basis of the mixtures 20-80% SiO2 : 80-20% SiO2/CdS are studied. The exciton percolation threshold is registered in those structures for the first time at a fraction of SiO2/CdS nanoparticles in the mixture of about 60%, which is twice as high as the value predicted by the hard sphere model. A qualitative explanation of this phenomenon is proposed. K e y w o r d s: exciton, quantum-size effect, exciton percolation, quantum dot.

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Section: Exciton Size Effect Feature In Sparse Arrays Of Quantum Dots...mentioning

confidence: 99%

Quantum-Size Effect and Exciton Percolation in Porous and Disordered Films on the Basis of Spherical “Core/Shell” Elements

2015

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“…The set of phenomena caused by transforming the wave functions of the electrons from a form that characterizes isolated states to a form typical of interacting QDs is sometimes called quantum percolation (see, for example, Refs. [24][25][26].…”

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confidence: 98%

Orbital and spin moments of one-electron states localized on quantum dots in a magnetic field

et al. 2015

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This paper discusses the behavior of single-electron states localized on quantum dots in an external magnetic field. Such states have a significant size of the electron cloud and can serve as a basis for implementing qubits with optical computation procedures. The orbital and spin "current" induced by a magnetic field in such states is calculated, along with the magnetic moments of these currents. It is shown that the magnetic susceptibility of the states of interest exceeds by several orders of magnitude the values that are characteristic of atomic physics, while the spin moment is determined only by the magnetic splitting factor of the semiconductor.It is well known that quantum dots (QDs) have been regarded for a fairly long time as possible candidates for the role of the memory elements of quantum computers, known as qubits (see for example, Refs. 1-5). An important advantage of CDs for implementing quantum computations is that they exhibit virtually none of the inhomogeneous broadening of the levels that is usually caused by interaction with the surroundings and which perturbs the quantum states. If such a QD has only one bound electronic state, it is sometimes called ideal. 6,7 Such states have a very small binding energy and a significant size of the electron cloud. The spatial delocalization of their wave functions makes it possible in principle to create the "entangled" states needed for quantum computations. For this, the cluster formed by the QDs must be fairly small (a simple quantitative estimate of the size is carried out below). Note that, even for the case of a single level in a well, optical measurement (or read-write) procedures are in principle possible-for example, on transitions from the bound state in a QD to the conduction band of the matrix. This opens up the possibility of optically implementing quantum computations in condensed media. Qubits can be implemented in this case on two-level systems with various spin states in an external magnetic field.To analyze such a possibility, it is necessary first of all to construct the wave functions of the states under consideration in a magnetic field. As shown below, electron states that have a very small binding energy and an electron cloud that is enormous on a microscale can be localized on ideal QDs. They are analogous in some sense to Rydberg atomic states. An electron in such a state passes inside the attractive center (the QD itself) for a very small fraction of the time, and its binding energy is much less than the depth of the potential well. This well is formed because of the difference of the energy levels of the bottom of the conduction band of the main matrix and the material of the QD. Therefore, the actual confining potential of such a particle can be approximated by a delta-potentiali.e., the potential of an infinitely small and infinitely deep well. The energetics of such weakly bound states in a magnetic field was first described in Ref. 8 (see also the monographs in Refs. 9 and 10)-but neglecting the spin states of the electron....

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Exciton photoluminescence and energy in a percolation cluster of ZnSe quantum dots as a fractal object

Cited by 2 publications

References 17 publications

Quantum-Size Effect and Exciton Percolation in Porous and Disordered Films on the Basis of Spherical “Core/Shell” Elements

Quantum-Size Effect and Exciton Percolation in Porous and Disordered Films on the Basis of Spherical “Core/Shell” Elements

Orbital and spin moments of one-electron states localized on quantum dots in a magnetic field

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