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1
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Coupling of Quantum Dots with Quantum Wells in a System Based on (Cd,Zn,Mg)Te

100%
Połczyńska K., Janik E., Kossacki P., Pacuski W.
Acta Physica Polonica A
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2017
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vol. 132
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issue 2
369-371
EN
Coupled low dimensional structures have potential applications in quantum computing and spintronics. Using molecular beam epitaxy we fabricated three kinds of systems of coupled quantum wells and quantum dots with different energy order: wells at higher energy than dots, resonant structures, and dots at higher energy than wells. By analysis of photoluminescence and reflectivity spectra, we conclude that there is a possibility of effective carrier tunneling between structures, which opens possibility of subsequent testing of spin transfer efficiency.
2
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Time-Resolved Studies of Excitonic Dynamics in a Wide II-VI Quantum Well by a Femtosecond Pump-Probe Reflectivity

88%
Trajnerowicz A., Golnik A., Kossacki P., Pacuski W., Wojtowicz T.
Acta Physica Polonica A
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2006
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vol. 110
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issue 3
395-401
EN
We present time-dependent reflectance spectra of wide (Cd,Mn)Te/(Cd,Mg)Te quantum wells. Interactions between excitons, trions, and carriers are studied for exciton densities up to 10^{11} cm^{-2}. The resonant excitation at different excitonic lines is analyzed.
3
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Preparation and Optical Properties of Zn_{1-x}Mn_xTe_{1-y}O_y Highly Mismatched Alloy

88%
Avdonin A., Van Khoi L., Pacuski W., Domukhovski V., Gałązka R.
Acta Physica Polonica A
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2007
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vol. 112
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issue 2
407-414
EN
The Zn_{1-x}Mn_xTe_{1-y}O_y alloy was prepared using a rapid crystallization technique. X-ray diffraction measurements were used to estimate the oxygen doping level. It is demonstrated that the oxygen solubility in Zn_{1-x} Mn_xTe_{1-y}O_y alloys greatly depends on the manganese concentration. No oxygen related effects were observed in the manganese free samples. The highest value of the oxygen molar fraction (y) achieved in the present study was 0.0023 in a sample having manganese fraction (x) of 0.056. The decrease in the alloy band gap was observed with increasing oxygen content. The oxygen-related trap level in Zn_{1-x}Mn_xTe_{1-y}O_y was found to be strongly shifted with respect to that in ZnTe_{1-y}O_y. The shift is assigned to a creation of complex (Mn_xO) traps.
4
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Photoluminescence Dynamics of CdSe Quantum Dot with Single Mn^{2+} Ion under Modulated Excitation

88%
Pilat M., Goryca M., Smoleński T., Pacuski W., Kossacki P.
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vol. 126
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issue 5
1212-1214
EN
A quantum dot with a single magnetic ion is a perfect model system to investigate spin dynamics of a magnetic ion embedded in semiconductor matrix. In this work we present results of spin dynamics studies of Mn^{2+} ion embedded in CdSe quantum dot, performed under modulated excitation of the dot. In particular, the relaxation time of the Mn^{2+} ion in high magnetic field was determined.
5
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Excitonic Giant Zeeman Effect in Wide Gap Diluted Magnetic Semiconductors Based on ZnO and GaN

76%
Pacuski W., Ferrand D., Kossacki P., Marcet S., Cibert J., Gaj J., Golnik A.
Acta Physica Polonica A
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2006
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vol. 110
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issue 3
303-309
EN
We present a theoretical description of the excitonic giant Zeeman effect observed in wide gap diluted magnetic semiconductors (Zn,Co)O and (Ga,Mn)N. In these materials, A and B excitons present quite complex energy shifts and change of oscillator strengths under magnetic field. These features can be well reproduced using an excitonic Hamiltonian, taking into account ion-carrier exchange, wurtzite trigonal crystal field, spin-orbit and electron-hole exchange interactions.
6
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MBE Growth and Magnetooptical Properties of (Zn,Co)Te Layers

76%
Papaj M., Kobak J., Rousset J., Janik E., Golnik A., Kossacki P., Pacuski W.
Acta Physica Polonica A
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2012
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vol. 122
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issue 6
1010-1011
EN
We report on epitaxial growth of diluted magnetic semiconductor (Zn,Co)Te. Reflectivity spectra reveal excitonic transition which split under magnetic field due to giant Zeeman effect. Magnetooptical effects can be described using literature data.
7
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Type I CdSe and CdMgSe Quantum Wells

76%
Rudniewski R., Rousset J., Janik E., Kossacki P., Golnik A., Nawrocki M., Pacuski W.
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vol. 126
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issue 5
1167-1170
EN
In this work we present the band gap engineering, epitaxial growth and optical characterization of CdSe/Cd_{0.9}Mg_{0.1}Se and Cd_{0.9}Mg_{0.1}Se/Cd_{0.85}Mg_{0.15}Se quantum wells with a thickness ranging from 1 to 15 nm. These structures exhibit strong near-band-gap photoluminescence from helium up to room temperature. The emission energy is tuned in the range from 1.74 to 2.1 eV at 7 K, depending on the thickness and well composition. The most intense photoluminescence (both at 7 and 300 K) was observed for 10 nm thick CdSe/Cd_{0.9}Mg_{0.1}Se wells. Such a structure gives also a sharp emission line (FWHM = 20 meV) at low temperature. The presented quantum wells are well suited for being embedded in lattice matched ZnTe based microcavities.
8
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Toward Better Light-Confinement in Micropillar Cavities

64%
Ściesiek M., Gietka K., Golnik A., Kossacki P., Jakubczyk T., Pacuski W., Kruse C., Hommel D.
Acta Physica Polonica A
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2011
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vol. 120
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issue 5
877-879
EN
We report on a two-step etching of ZnTe based micropillars. We demonstrate applicability of the technology and we analyze the optical properties of obtained structures. Microphotoluminescence spectra of individual micropillars show a typical mode pattern that confirms a successful growth of photonic structures. The reflectivity and photoluminescence spectra of a planar microcavity measured for various incident angles show that additional side distributed Bragg reflectors will be important for the further enhancement of photon confinement in micropillar cavity.
9
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MBE Growth of CdTe/ZnTe Quantum Dots with Single Mn Ions

64%
Gietka K., Kobak J., Rousset J., Janik E., Słupiński T., Kossacki P., Golnik A., Pacuski W.
Acta Physica Polonica A
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2012
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vol. 122
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issue 6
1056-1058
EN
We report MBE growth and properties of samples with self assembled quantum dots with single manganese ions and low density of quantum dots. Manganese concentration was calibrated using magneto-reflectivity measurements and the giant Zeeman effect in (Cd,Mn)Te and (Zn,Mn)Te layers. Successful incorporation of Mn in the CdTe/ZnTe quantum dots was confirmed using micro-photoluminescence measurements: single manganese ion in quantum dot manifests in sixfold splitting of exciton emission lines due to s, p-d exchange interaction.
10
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MBE Growth and Characterization of a III-V Distributed Bragg Reflectors and InAs Quantum Dots

64%
Rousset J., Słupinski T., Jakubczyk T., Kobak J., Stawicki P., Gołasa K., Babinski A., Nawrocki M., Pacuski W.
Acta Physica Polonica A
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2012
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vol. 122
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issue 6
984-987
EN
We describe the realization and characterization of a distributed Bragg reflectors and InAs quantum dots grown by molecular beam epitaxy. The distributed Bragg reflectors are based on a stack of eight or twenty pairs of GaAs and AlAs layers with a stopband centered at about E_0=1.24 eV (λ_0=1000 nm). The whole structures exhibit a reflectivity coefficient above 90%. The growth rate was monitored in situ by measurement of the oscillations of the thermal emission intensity. The investigations conducted on the InAs quantum dots grown on GaAs show photoluminescence around E=1.25 eV (λ=990 nm). The combination of these two elements results in the realization of a microcavity containing InAs quantum dots and surrounded by 20 pairs of distributed Bragg reflectors.
11
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Optical Properties of CdTe QDs Formed Using Zn Induced Reorganization

64%
Kobak J., Pacuski W., Jakubczyk T., Kazimierczuk T., Golnik A., Frank K., Rosenauer A., Kruse C., Hommel D., Gaj J.
Acta Physica Polonica A
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2011
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vol. 119
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issue 5
627-629
EN
In this paper we present optical studies of CdTe quantum dots formed using Zn-induced reorganization. The pattern of quantum dot photoluminescence lines is found to be similar to typical results reported for quantum dots grown with other techniques, although the positively charged exciton line is relatively more pronounced. Also the energy spacing between biexciton and exciton lines is found to be larger than in typical results. Zn-induced reorganization results in quantum dots density higher by an order of magnitude than in Te-induced quantum dots.
12
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Deep Levels Induced by CdTe/ZnTe Quantum Dots

64%
Zielony E., Placzek-Popko E., Roznicka A., Gumienny Z., Szatkowski J., Dyba P., Pacuski W., Kruse C., Hommel D., Guziewicz M.
Acta Physica Polonica A
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2011
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vol. 119
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issue 5
630-632
EN
The electrical properties of the CdTe/ZnTe quantum dot system have been analyzed to identify deep-level defects related with the presence of quantum dots. The capacitance-voltage (C-V) and deep level transient spectroscopy measurements were used to investigate the samples. A reference ZnTe sample (without dots) was also studied for comparison. Both samples were grown by molecular beam epitaxy technique on the n-type GaAs substrate. The quantum dots were formed by a Zn-induced reorganization of a thin CdTe layer. The presence of quantum dot formation was confirmed by micro-photoluminescence measurements. The deep level transient spectra for both samples are complex. In order to characterize individual contributions to the deep level transient spectra the latter have been simulated by separated Gaussian components [1]. The results of the deep level transient spectroscopy measurements yield the conclusion that the same defects are present in both materials but there is an increased concentration of the defects in the quantum dot structures. No deep level associated directly with the quantum dot confinement has been identified.
13
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Optical Properties of CdTe QDs in Proximity to a Surface

64%
Piwowar J., Papierska J., Sawicki K., Kobak J., Pacuski W., Golnik A., Kossacki P., Suffczyński J.
Acta Physica Polonica A
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2013
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vol. 124
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issue 5
795-797
EN
Optical properties of CdTe/ZnTe quantum dots are studied as a function of a capping layer thickness by means of time-integrated and time-resolved microphotoluminescence. The samples are grown by MBE and covered with 10 nm and 100 nm capping layer. Despite that the proximity of the surface may result in an enhanced rate of non-radiative processes limiting the quantum dots optical performance, the set of results indicates that reduction of the capping layer thickness down to 10 nm has no effect on the quantum dot emission intensity and decay rate, contrary to the previously reported case of InAs/GaAs quantum dots.
14
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Optical Study of ZnTe-Based 2D and 0D Photonic Structures Containing CdTe/ZnTe Quantum Dots

64%
Jakubczyk T., Kazimierczuk T., Golnik A., Bienias P., Pacuski W., Kruse C., Hommel D., Kłopotowski Ł., Wojtowicz T., Gaj J.
Acta Physica Polonica A
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2009
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vol. 116
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issue 5
888-889
EN
We report on an optical study of ZnTe-based microcavity and micropillars. Angle-resolved reflectivity studies confirm a high quality of the investigated structure by setting the lower bound on the quality factor Q ≥ 1000, determined from normal-incidence reflection spectra. In a microphotoluminescence study, micropillar modes are observed at temperatures of the order of tens of kelvins. For structures grown by a complex growth procedure at two different MBE facilities, an enhancement of photoluminescence in the cavity mode is observed.
15
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Magnetooptical Properties of (Ga,Fe)N Layers

52%
Papierska J., Rousset J., Pacuski W., Kossacki P., Golnik A., Nawrocki M., Gaj J., Suffczyński J., Kowalik I., Stefanowicz W., Sawicki M., Dietl T., Navarro-Quezada A., Faina B., Li T., Bonanni A.
Acta Physica Polonica A
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2011
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vol. 120
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issue 5
921-923
EN
Magnetooptical properties of (Ga,Fe)N layers containing various concentrations of Fe-rich nanocrystals embedded in paramagnetic (Ga,Fe)N layers are reported. Previous studies of such samples demonstrated that magnetization consists of a paramagnetic contribution due to substitutional diluted Fe ions as well as of ferromagnetic and antiferromagnetic components originating from Fe-rich nanocrystals, whose relative abundance can be controlled by the growth conditions. The nanocrystals are found to broaden and to reduce the magnitude of the excitonic features. However, the ferromagnetic contribution, clearly seen in SQUID magnetometry, is not revealed by magnetic circular dichroism. Possible reasons for differences in magnetic response determined by magnetic circular dichroism and SQUID measurements are discussed.
16
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Growth and Properties of ZnMnTe Nanowires

46%
Zaleszczyk W., Janik E., Presz A., Szuszkiewicz W., Morhange J., Dłużewski P., Kret S., Kirmse H., Neumann W., Dynowska E., Domagała J., Caliebe W., Aleszkiewicz M., Pacuski W., Golnik A., Kossacki P., Baczewski L., Petroutchik A., Karczewski G., Wojtowicz T.
Acta Physica Polonica A
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2007
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vol. 112
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issue 2
351-356
EN
Catalytically enhanced growth of ZnMnTe diluted magnetic semiconductor nanowires by molecular beam epitaxy is reported. The growth is based on the vapor-liquid-solid mechanism and was performed on (001) and (011)-oriented GaAs substrates from elemental sources. X-ray diffractometry, scanning and transmission electron microscopy, atomic force microscopy, photoluminescence spectroscopy, and Raman scattering were performed to determine the structure of nanowires, their chemical composition, and morphology. These studies revealed that the obtained ZnMnTe nanowires possess zinc-blende structure, have an average diameter of about 30 nm, typical length between 1 and 2μm and that Mn^{2+} ions were incorporated into substitutional sites of the ZnTe crystal lattice.
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