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1
Content available remote

Temperature of a Single Mn Atom in a CdTe Quantum Dot

100%
Papierska J., Goryca M., Wojnar P., Kossacki P.
Acta Physica Polonica A
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2009
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vol. 116
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issue 5
899-900
EN
In this work we present a study of the temperature of the single magnetic atom embedded in a semiconductor quantum dot versus excitation power and magnetic field. This temperature is defined by the thermal distribution of spin states of single Mn ion, and results from its interaction with the neighborhood. This temperature was found to be much higher than the temperature of the thermal bath. Its dependence on the excitation power and magnetic field is discussed.
2
Content available remote

Changing the Properties of the CdTe/ZnTe Quantum Dots by in situ Annealing during the Growth

100%
Wojnar P., Karczewski G., Wojtowicz T., Kossut J.
Acta Physica Polonica A
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2007
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vol. 112
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issue 2
283-288
EN
We present an attempt to control the properties of CdTe/ZnTe self-assembled quantum dots during their formation in the process of molecular beam epitaxy. Namely, the structures were in situ annealed at various temperatures and annealing times after the formation of quantum dots, before the deposition of a capping layer. Depending on the annealing parameters, the dots exhibit different optical properties which were studied by means of spatially resolved photoluminescence. From the analysis of these results, the information about relative changes of the average size and sheet density of quantum dots was extracted.
3
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Numerical Rate Equation Approach to Picosecond Charge State Dynamics in CdTe/ZnTe Quantum Dots

76%
Koperski M., Kazimierczuk T., Goryca M., Wojnar P., Golnik A., Kossacki P., Gaj J.
Acta Physica Polonica A
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2009
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vol. 116
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issue 5
893-895
EN
The rate equation is used for description of photoluminescence dynamics after pulsed excitation of various states of quantum dots. The picosecond dynamics of averaged charge state of quantum dot is described. We compare our simulations with the experiment and come up with the conclusion that probability of carrier capture weakly depends on quantum dot charge state and that electrons and holes are captured non-synchronously.
4
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Anisotropic Exchange Interaction between p-Shell Electron and s-Shell Hole in CdTe/ZnTe Quantum Dots

76%
Kazimierczuk T., Golnik A., Goryca M., Wojnar P., Gaj J., Kossacki P.
Acta Physica Polonica A
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2009
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vol. 116
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issue 5
882-884
EN
We study electron-hole exchange interaction in a single CdTe/ZnTe quantum dot by polarization-resolved photoluminescence measurements. We focus on recombination of excitonic states involving p-shell electrons: X^{2-} and XX^-. Recombination lines of X^{2-} and XX^- states exhibit fine structure, which can be consistently explained within a model with four parameters δ_{i}^{αβ} representing strength of iso- and anisotropic parts of interaction between s-hole and s- or p-electron.
5
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Control of Local Electric Fields Influencing the Photoluminescence οf an Individual CdTe/ZnTe Quantum Dot

76%
Haas K., Kazimierczuk T., Wojnar P., Golnik A., Gaj J., Kossacki P.
Acta Physica Polonica A
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2009
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vol. 116
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issue 5
896-898
EN
We examine the influence of a weak non-resonant illumination on the quantum dot photoluminescence spectrum. We observe that even very weak illumination affects both intensity and spectral position of emission lines in the spectrum. We discover no significant asymmetry in spatial dependence and infer that the observed effects cannot be attributed to a single neighbor center.
6
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Identification of Optical Transitions from CdTe and CdMnTe Quantum Dots Embedded in ZnTe Nanowires

76%
Szymura M., Kłopotowski Ł., Wojnar P., Karczewski G., Wojtowicz T., Kossut J.
Acta Physica Polonica A
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2013
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vol. 124
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issue 5
824-826
EN
We study photoluminescence properties of CdTe and CdMnTe quantum dots embedded in ZnTe nanowires. The nanowires were grown by molecular beam epitaxy, applying the vapor-liquid-solid growth mechanism. Linear polarization anisotropy measurements allow us to assess that the excitonic transitions originate from a single nanowire. We identify the optical transitions by comparing observed spectroscopic shifts with the universal emission pattern from the epitaxial CdTe dots. We support this identification by analyzing the photoluminescence intensity dependence on excitation power.
7
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The Novel Multichannel Single Photon Correlations Technique Applied for the Spin Dynamics Study of a Few Mn^{2+} Ions in a CdTe/ZnTe Quantum Dot

76%
Malinowski F., Koperski M., Goryca M., Smoleński T., Golnik A., Kossacki P., Wojnar P.
Acta Physica Polonica A
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2013
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vol. 124
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issue 5
791-794
EN
In this work we demonstrate a novel experimental approach to the study of single photon correlations. The introduction of the multichannel detection setup enables the simultaneous measurement of a large number of correlation functions for photons emitted from different energetic ranges. The advantages of this new approach were exploited in a detailed study of the biexciton-exciton recombination cascade in CdTe/ZnTe quantum dots doped with a few Mn^{2+} ions. The information about the dynamics of the magnetic system in the quantum dot during the lifetime of the exciton was obtained from the analysis of the correlation functions.
8
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Resonant Excitation of CdTe/ZnTe Quantum Dot Pairs as a Tool for Spectroscopic Study of the Excitonic p-States

76%
Bogucki A., Smoleński T., Goryca M., Koperski M., Wojnar P., Kossacki P.
Acta Physica Polonica A
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2013
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vol. 124
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issue 5
788-790
EN
We propose a new method of obtaining a photoluminescence spectrum of a single quantum dot in a self-assembled system of CdTe/ZnTe quantum dots. The method is based on the resonant excitation of a coupled dots pair. The comparison of the spectra in resonance and out of resonance enables the identification of a well-isolated lines related to the excitonic p-states. The application of the method allows the basic characterisation of a quantum dot, including the measurements of linear anisotropy, the excitation power dependence, and the analysis of the photoluminescence in the magnetic field.
9
Content available remote

Signatures of p-Shell Electron g-Factor in s-Shell Emission of CdTe/ZnTe Quantum Dots

76%
Kazimierczuk T., Goryca M., Wojnar P., Golnik A., Nawrocki M., Kossacki P.
Acta Physica Polonica A
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2011
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vol. 120
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issue 5
874-876
EN
We analyze the photoluminescence of excitonic complexes containing p-shell electron in the magnetic field in the Faraday configuration. We demonstrate that despite the p-shell electron is not involved directly in the recombination process, its g-factor influences the emission spectrum. We found that in the case of CdTe/ZnTe quantum dots the p-shell electron is significantly less affected by the magnetic field than s-shell electron in the same dot.
10
Content available remote

Inter-Dot Coupling in a Self-Assembled Quantum Dot System

76%
Kazimierczuk T., Nowak S., Suffczyński J., Wojnar P., Golnik A., Gaj J., Kossacki P.
Acta Physica Polonica A
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2007
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vol. 112
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issue 2
321-324
EN
We present studies of resonant excitation of self-assembled CdTe/ZnTe quantum dots. Photoluminescence excitation measurements revealed existence of sharp resonances, common for photoluminescence lines attributed to different quantum dot charge states. We conclude from the ensemble of photoluminescence and photoluminescence excitation results that we observe energy transfer in coupled quantum dot pairs.
11
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Magnetoluminescence of a CdTe Quantum Dot with a Single Manganese Ion in Voigt Configuration

76%
Koperski M., Goryca M., Kazimierczuk T., Kossacki P., Wojnar P., Gaj J.
Acta Physica Polonica A
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2011
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vol. 119
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issue 5
618-620
EN
We present a study of the neutral exciton and negative trion recombination spectra of an individual CdTe quantum dot with a single manganese ion, in magnetic field measured in the Voigt configuration. We describe experimental results and compare with a theoretical model. The quantitative agreement between the model and the experiment allows us to determine separately the electron g-factor.
12
Content available remote

Single-Photon Emission from a Highly Excited CdTe Quantum Dot

64%
Nowak S., Goryca M., Kazimierczuk T., Gaj J., Golnik A., Kossacki P., Wojnar P., Karczewski G.
Acta Physica Polonica A
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2008
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vol. 114
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issue 5
1273-1278
EN
Time-resolved correlation measurements were performed to examine the statistics of photon emission from a single quantum dot at high excitation levels. The range of strong powers was determined by the saturation of intensity of excitonic lines. The significant contribution of pulsed background luminescence forced us to sophisticated analysis of the photoluminescence spectra. For quantum dots grown in the Stranski-Krastanov mode, one-photon emission was found to a good approximation. Fluctuation type quantum dots exhibit a significant level of multiphoton emission.
13
Content available remote

Spin-Related Spectroscopy of CdTe-Based Quantum Dots

64%
Gaj J., Kazimierczuk T., Goryca M., Koperski M., Golnik A., Kossacki P., Nawrocki M., Wojnar P., Karczewski G.
Acta Physica Polonica A
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2009
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vol. 116
|
issue 5
795-799
EN
This work contains a selection of our recent experimental results in the field of the spin-related spectroscopy of individual CdTe-based quantum dots. After a short description of the sample growth and experimental methods, optical measurements of the charge state dynamics are presented. Then the influence of in-plane anisotropy of the excitonic states of a quantum dot is discussed, followed by a description of experimental studies of information read-out and writing on quantum dot spin states. In particular, spin memory of a single Mn^{++} ion embedded in a CdTe quantum dot is quantitatively assessed. In an outlook part, perspectives opened by recently developed ZnTe lattice-matched Bragg reflectors are discussed.
14
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Content available

Topographical, Magnetic and Optical Studies of (II,Mn)VI Quantum Structures Grown on (Ga,Mn)As

64%
Butkutė R., Aleszkiewicz M., Janik E., Cywiński G., Wojnar P., Däweritz L., Primus J., De Boeck J., Kossut J.
Acta Physica Polonica A
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2003
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vol. 103
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issue 6
649-657
EN
We report on an overgrowth of quantum structures consisting of diluted magnetic semiconductor CdMnTe quantum wells with non-magnetic barriers made of CdMgTe or ZnTe on ferromagnetic MnAs and GaMnAs films by molecular beam epitaxy. Atomic force microscopy images of the quantum structures grown on MnAs demonstrated the existence of two types of regions on the surface: protruded islands with micrometric sizes, surrounded by areas of small-scale roughness. Magnetic force microscopy study of these samples revealed a magnetic domain structure only on the above mentioned islands. The (II,Mn)VI quantum wells grown on GaMnAs films exhibited relatively smooth surface, but no magnetic force microscopy signal was measurable either before or after magnetizing the sample. In the luminescence spectra of all our quantum structures the emission attributed to CdMnTe quantum wells was observed. The influence of magnetization on the luminescence line position was investigated.
15
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Spectroscopy of Indirect Excitons in Vertically Stacked CdTe Quantum Dot Structures

64%
Kukliński K., Kłopotowski Ł., Fronc K., Wojnar P., Wojciechowski T., Czapkiewicz M., Kossut J., Karczewski G., Wojtowicz T.
Acta Physica Polonica A
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2011
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vol. 120
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issue 5
856-858
EN
We show that by means of an electric field we can tune the energy levels in vertical quantum dot pairs and study transitions related to recombination of direct and indirect excitons. With decreasing the reverse bias, we observe both the blue- and red-shifted indirect exciton transitions. Based on the band profile of our device, we conclude that the former corresponds to the recombination of the electron and hole localized in the top and the bottom dot, respectively and the latter is related to the recombination of the electron and hole localized in the bottom and the top dot, respectively.
16
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Statistical Study of the Inter-Dot Excitation Transfer in CdTe/ZnTe Quantum Dots

64%
Koperski M., Kazimierczuk T., Goryca M., Golnik A., Gaj J., Nawrocki M., Wojnar P., Kossacki P.
Acta Physica Polonica A
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2011
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vol. 120
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issue 5
880-882
EN
In this work we present a statistical study of resonantly excited luminescence of coupled CdTe/ZnTe quantum dots studied by photoluminescence excitation measurements. We investigate the probability of resonance occurrence as a function of resonant energy. We come to the conclusion that the distribution of the inter-dot resonances is uniform, which suggests that the inter-dot excitation transfer is not limited by mean density of states in the emitting quantum dots.
17
Content available remote

TEM Study of the Structural Properties of Nanowires Based on Cd, Zn, Te grown by MBE on Silicon Substrates

64%
Kaleta A., Kret S., Sanchez A., Bilska M., Kurowska B., Szczepańska A., Płachta J., Wojnar P., Wojciechowski T.
Acta Physica Polonica A
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2017
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vol. 131
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issue 5
1399-1405
EN
In this work we report on the atomic structures, elemental distribution, defects and dislocations of three types of semiconductor nanowires: ZnTe, CdTe, and complex ZnTe/(Cd,Zn)Te core/shell hetero-nanowires grown by a molecular beam epitaxy on (111) Si substrate using a vapor-liquid-solid mechanism. The structural properties and the chemical gradients were measured by transmission electron microscopy methods. The nanowires reveal mainly sphalerite structure, however wurtzite nanowires were also observed.
18
Content available remote

Influence of Configuration Mixing on Energies and Recombination Dynamics of Excitonic States in CdTe/ZnTe Quantum Dots

64%
Smoleński T., Kazimierczuk T., Goryca M., Kossacki P., Gaj J., Wojnar P., Fronc K., Korkusiński M., Hawrylak P.
Acta Physica Polonica A
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2011
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vol. 119
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issue 5
615-617
EN
We study experimentally and theoretically excitonic recombination processes in CdTe/ZnTe quantum dots. The single quantum dot photoluminescence spectrum was observed and emission lines from X, X^-, X^+ and 2X excitonic states were identified. Experimental results were analysed in the theoretical model based on the effective mass approximation. Numerical calculations of energy positions and recombination probabilities of X, X^-, X^+ and 2X were performed. Computed results reproduce correctly the order and relative positions of emission lines and ratios of radiative lifetimes.
19
Content available remote

Excitation Mechanisms of CdTe/ZnTe Quantum Dots under Non-Resonant and Quasi-Resonant Regime

64%
Kazimierczuk T., Gaj J., Golnik A., Goryca M., Nawrocki M., Koperski M., Smoleński T., Suffczyński J., Wojnar P., Kossacki P.
Acta Physica Polonica A
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2011
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vol. 119
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issue 5
588-591
EN
We discuss possible mechanisms of quantum dot population control. A set of experiments, including time-resolved photoluminescence, single photon correlations, excitation correlation, and photoluminescence excitation is used to determine the actual mechanism under non-resonant and quasi-resonant regime.
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