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1

GaMnAs: Layers, Wires and Dots

100%

Sadowski J.

Acta Physica Polonica A

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2008

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vol. 114

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issue 5

1001-1012

EN

Thin layers of GaMnAs ferromagnetic semiconductor grown by molecular beam epitaxy on GaAs(001) substrates were studied. To improve their magnetic properties the post-growth annealing procedures were applied, using the surface passivation layers of amorphous arsenic. This post-growth treatment effectively increases the ferromagnetic-to-paramagnetic phase transition in GaMnAs, and provides surface-rich MnAs layer which can be used for formation of low-dimensional structures such as superlattices. If the surface rich MnAs layer consists of MnAs dots, then it is possible to grow Mn-doped GaAs nanowires.

2

Application of microarray technology in plant genes expression

52%

Ludwikow A., Krasowski K., Misztal L. H., Sadowski J.

Biotechnologia

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2008

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issue 4

131-143

EN

A major progress has been made in the last decade in the understanding of molecular mechanisms involved in plant responses to stresses. This has been achieved in great part by application of a high-throughput genomics tools. Transcriptome analysis based on the DNA microarray technique has proved its effectiveness in studies of genome level responses to environmental changes and genetic manipulations. From the perspective of a decade, DNA microarrays serve as an invaluable tool for global gene expression analyses, unravelling new information about genes, pathways and their transcriptional regulation networks. In this review, we present applications of the DNA microarrays and a basic analysis of microarray data in relation to the transcriptional response of plants to ozone and drought stresses.

3

Electrically Detected Magnetic Resonance

52%

Fedorych O., Wilamowski Z., Jantsch W., Sadowski J.

Acta Physica Polonica A

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2004

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vol. 105

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issue 6

591-598

EN

We compare the results of electrically detected magnetic resonance in a 2D electron gas in Si/SiGe quantum wells with transport and magnetic resonance measurements on ferromagnetic Ga_{1-x}Mn_xAs. The results lead us to the conclusion that observation of electrically detected magnetic resonance is possible only in the case of a slow spin relaxation, where the microwave resonant absorption leads to a noticeable change of spin magnetization.

4

Observation of Vacancies in Ga_{1-x}Mn_xAs with Positron Annihilation Spectroscopy

52%

Tuomisto F., Slotte J., Saarinen K., Sadowski J.

|

EN

Positron annihilation spectroscopy can be used to determine the role of vacancy defects in semiconductors, by identification and quantification of the vacancies and their chemical surroundings. We have studied 0.5-0.8μm thick low temperature MBE GaMnAs layers with Mn content 0.5--5% and different As_2 partial pressures at growth. The Doppler broadening results show that the Ga vacancy concentration in the layers decreases with increasing Mn content and decreasing As_2 partial pressure.

5

Growth Processes of ZnTe Epilayers Deposited by MBE on GaAs(100) Vicinal Surfaces - Studies by Static and Dynamic RHEED

52%

Sadowski J., Dziuba Z., Iierman M. A.

Acta Physica Polonica A

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1995

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vol. 87

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issue 1

225-228

EN

Static and dynamic reflection high energy electron diffraction (RHEED) has been applied for studying the initial growth processes of ZnTe crystallized by molecular beam epitaxy (MBE) on vicinal surfaces of GaAs(100) substrates. Atomically smooth ZnTe epilayers have been grown by MBE when in situ thermal desorption of the substrate protecting oxide layer was performed in the ultra high vacuum environment of the vacuum growth chamber just before the growth of ZnTe started. By gradual increasing of the substrate temperature of the crystallized ZnTe epilayers from 300°C to 420°C, when recording the RHEED intensity oscillations at these and eleven intermittent temperatures, it has been shown that the transition from the 2D-nucleation growth mechanism to the step-flow growth mechanism of ZnTe occurs at 410°C. Measuring periods of RHEED intensity oscillations recorded during the MBE growth processes it has been demonstrated that the growth rate of ZnTe at constant fluxes of the constituent elements decreases with increasing temperature from 0.37 ML/s at 300°C to 0.22 ML/s at 400°C.

6

MBE Growth of YbTe on GaAs(100) and BaF_{2}(111) Substrates

52%

Sadowski J., Dynowska E., Kowalczyk L.

Acta Physica Polonica A

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1995

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vol. 88

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issue 5

1028-1032

EN

The structural properties of MBE grown YbTe layers were investigated by X-ray diffraction methods and photoluminescence measurements. YbTe films were grown on the ZnTe and CdTe buffer layers crystallised on the GaAs(100) 2° off oriented substrates and on the BaF_{2}(100) substrates. In the case of GaAs substrates the two-dimensional growth mode of YbTe was observed on reflection high energy electron diffraction picture. Results of the X-ray rocking curve and photoluminescence excitation measurements indicate that the structural properties of YbTe films are comparable to the properties of the MBE grown ZnTe and CdTe layers on the GaAs(100) substrates. The measured values of the YbTe lattice constant parallel and perpendicular to the growth plane show that the 1 μm thick layers are partially strained. The full width at half maximum values of the X-ray rocking curves are the smallest (900 arc seconds) for the YbTe films crystallised on the 2 μm thick CdTe bucher layer grown on the GaAs(100) substrate. In the case of BaF_{2}(111) substrate the two-dimensional MBE growth mode of YbTe was not observed.

7

Comparative sequencing of genomes: generating of INDEL and SNP genetic markers

46%

Ziolkowski P. A., Babula-Skowronska D., Kaczmarek M., Ciesla A., Sadowski J.

Biotechnologia

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2010

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issue 4

53-68

EN

Comparison of genome sequences has become an important approach to identify and understand biological significance of the variations and fluxes that occur through a genome. The main subject of the work concentrates on identification of indels and SNPs in large genomes and their potential application in biotechnology. Importantly, fine elaboration of genome structure and sequence polymorphism that results from resequencing promises to benefit breeding, biotechnology and medical research. The article also describes how the data extracted from comparative studies of genomes depends on phylogenetic distances of the species involved.

8

Optical Pump - Terahertz Probe Measurement of the Electron Dynamics in Ga_{1-x}Mn_xAs

46%

Šustavičiūtė R., Balakauskas S., Adomavičius R., Krotkus A., Sadowski J.

Acta Physica Polonica A

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2007

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vol. 112

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issue 2

311-314

EN

An optical pump - terahertz probe technique was used for measuring electron lifetime in various Ga_{1-x}Mn_xAs epitaxial layers with the subpicosecond temporal resolution. The measurements were performed on the samples with x up to 2%, which had large resistivities and were transparent in a THz frequency range. It has been found that an induced THz absorption relaxation is the fastest and electron lifetimes are the shortest for the samples with the smallest Mn content. For the samples with x=0.3% and x=2% this relaxation becomes much slower; its rate is comparable to the carrier recombination rate in Ga_{1-x}Mn_xAs substrate.

9

Ferromagnetic, Ferrimagnetic and Spin-wave Resonances in GaMnAs Layers

46%

Fedorych O., Byszewski M., Wilamowski Z., Potemski M., Sadowski J.

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issue 4-5

617-625

EN

Molecular beam epitaxy grown Ga_{1-x}Mn_xAs layers were investigated by means of magnetic resonances. With an increase in Mn concentration, x, the spectrum changes from the (i) paramagnetic one, with resolved fine and hyperfine structures, typical of S=5/2 spin of substitutional Mn^{2+} ions, for very diluted alloy, via (ii) paramagnetic spectrum, where the fine and hyperfine structures are averaged by a long range Mn^{2+}-Mn^{2+} exchange coupling, (iii) single, isotropic line of ferromagnetic resonance. Insulator to metal transition is accompanied with occurrence of (iv) a very complex spectrum of the ferrimagnetic resonance, accompanied with the well-resolved spin wave resonance. Reentrance to insulator phase for the most condensed alloys is accompanied with the reentrance to (v) ferromagnetic phase. The data confirm that the effective mass holes transfer the exchange interaction between localized Mn^{2+} spins.

10

Magnetic Resonance Studies of the Origin of Ferromagnetism in Ga_{1-x}Mn_xAs

46%

Fedorych O., Wilamowski Z., Potemski M., Byszewski M., Sadowski J.

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EN

Different types of magnetic resonance observed in Ga_{1-x}Mn_xAs reflect three different magnetic phases: para-, ferro-, and ferrimagnetic. Ferromagnet is characterized by single isotropic resonance line. A complex spectrum in ferrimagnet can be described by g factor equal to 1.44 and a sum of an axial and cubic anisotropy field. The axial field is by an order of magnitude greater than the cubic one. The complex structure of ferrimagnetic resonance is attributed to spin-wave resonance. Quantitative analysis of the dispersion of spin wave shows that the range of exchange coupling is very long, of the order of 25 nm, while spin-wave stiffness and the total exchange field are very small. The exchange field as evaluated from spin wave is by two orders of magnitude smaller than the Zener field corresponding to the critical temperature.

11

Zn(Mn)O Surface Alloy Studied by Synchrotron Radiation Photoemission

46%

Guziewicz E., Kopalko K., Sadowski J., Guziewicz M., Golacki Z.

Acta Physica Polonica A

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2005

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vol. 108

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issue 4

689-696

EN

The Mn/ZnO(0001) system was investigated by synchrotron radiation photoemission. The Mn/ZnO interface with 4 ML of manganese deposited onto the ZnO surface was annealed up to 500ºC. No Mn capping layer was found at the surface after annealing as was confirmed by scanning Auger spectroscopy experiment. We used a resonant photoemission to extract the Mn3d partial density of states in photoemission spectra. The Mn3d states contribute to the electronic structure of the system within 10 eV of the Fermi level. They show three features: a main peak at 3.8-4.5 eV, a valence structure at the top of the valence band (1-3 eV), and a broad satellite situated between 5.5 and 9 eV below E_F. The satellite/main branching ratio was determined to be 0.43, which is a fingerprint of strong hybridization between the Mn3d electrons and the valence band of the crystal. The hybridization effect in Zn_{1-x} Mn_xO surface alloy is comparable to Zn_{1-x}Mn_xS and much higher than in Zn_{1-x}Mn_xSe, Zn_{1-x}Mn_xTe, and Ga_{1-x}Mn_xAs semimagnetic compounds.

12

Magnetic Properties of Short Period InGaMnAs/InGaAs Superlattices

40%

Sadowski J., Mathieu R., Svedlindh P., Kanski J., Karlsteen M., Świątek K., Domagała J.

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issue 4-5

687-694

EN

We have observed a paramagnetic-to-ferromagnetic phase transition in short period InGaMnAs/InGaAs superlattices. The thicknesses of magnetic InGaMnAs layers in the structures studied was chosen to be 4 or 8 molecular layers (12Å or 24Å). The non-magnetic InGaAs spacer layers are 12Å thick. The composition (In content) in InGaMnAs and InGaAs was chosen in such a way that magnetic layers were: deep potential wells, high potential barriers, or shallow potential wells. For superlattices with 8 monolayer thick InGaMnAs magnetic layers and 4 monolayer thick InGaAs non-magnetic spacers the temperatures of paramagnetic-to-ferromagnetic phase transition do not depend on the band offsets between InGaMnAs and InGaAs adjusted by the In content.

13

MBE Growth and Properties of GaMnAs(100) Films

40%

Sadowski J., Domagała J., Bąk- Misiuk J., Świątek K., Kanski J., Ilver L., Oscarsson H.

Acta Physica Polonica A

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1998

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vol. 94

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issue 3

509-513

EN

We present here the results of measurements of structural and electronic properties of GaMnAs - a new diluted magnetic semiconductor system. This ternary III-V-Mn compound with the Mn content as high as 7% was obtained for the first time (by means of molecular beam epitaxial growth) by Ohno, Munekata et al. and the studies of its properties are not completed until now. We did the high resolution X-ray diffraction investigations and photoemission measurements of the samples with Mn content varied from about 0.1% up to 5%. The crystalline perfection of the ternary GaMnAs compound is very high - full width at half maximum of GaMnAs (400) Bragg reflections are of order of 50 arcseconds and the layers are fully strained to the GaAs(100) substrate. In photoemission experiments we traced the contribution of Mn 3d states to the band structure of GaMnAs ternary compound.

14

MnAs Nanocrystals Embedded in GaAs

40%

Kwiatkowski A., Wasik D., Kamińska M., Twardowski A., Dłużewski P., Borysiuk J., Sadowski J.

Acta Physica Polonica A

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2008

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vol. 114

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issue 5

1207-1211

EN

Magnetic properties of MnAs nanocrystals embedded in GaAs are analyzed in the frame of phenomenological model proposed by Sasaki for ferritin superparamagnets. Our calculations explain qualitatively experimental data of magnetization versus temperature, obtained according to zero-field-cooled and field-cooled protocols. They show dynamics of magnetization of MnAs nanocrystals in range of temperature from 10 K to 320 K. There is transition from state in which very slow dynamics is observed (frozen state) to state in which dynamics is fast (quasi-superparamagnetic state).

15

Off-Axis Electron Holography of Magnetic Nanostructures: Magnetic Behavior of Mn Rich Nanoprecipitates in (Mn,Ga)As System

40%

Barańska M., Dłużewski P., Kret S., Morawiec K., Li T., Sadowski J.

Acta Physica Polonica A

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2017

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vol. 131

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issue 5

1406-1408

EN

The Lorentz off-axis electron holography technique is applied to study the magnetic nature of Mn rich nanoprecipitates in (Mn,Ga)As system. The effectiveness of this technique is demonstrated in detection of the magnetic field even for small nanocrystals having an average size down to 20 nm.

16

Interval Identification of FMR Parameters for Spin Reorientation Transition in (Ga,Mn)As

40%

Gutowski M., Stefanowicz W., Proselkov O., Sawicki M., Żuberek R., Sadowski J.

Acta Physica Polonica A

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2012

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vol. 121

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issue 5-6

1228-1230

EN

In this work we report results of ferromagnetic resonance studies of a 6% 15nm (Ga,Mn)As layer, deposited on (001)-oriented GaAs. The measurements were performed with in-plane oriented magnetic field, in the temperature range between 5 K and 120 K. We observe a temperature induced reorientation of the effective in-plane easy axis from [\overline{1}10] to [110] direction close to the Curie temperature. The behavior of magnetization is described by anisotropy fields, H_{eff} (=4π M-H_{2⊥}), H_{2∥}, and H_{4∥}. In order to precisely investigate this reorientation, numerical values of anisotropy fields have been determined using powerful - but still largely unknown - interval calculations. In simulation mode this approach makes possible to find all the resonance fields for arbitrarily oriented sample, which is generally intractable analytically. In "fitting" mode we effectively utilize full experimental information, not only those measurements performed in special, distinguished directions, to reliably estimate the values of important physical parameters as well as their uncertainties and correlations.

17

Structural and Electrical Properties of Low Concentration SnTe Layers and PbTe/SnTe Heterostructures Grown by MBE

40%

Sadowski J., Grodzicka E., Dynowska E., Adamczewska J., Domagała J., Przedpelski W.

Acta Physica Polonica A

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1997

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vol. 92

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issue 5

967-970

EN

We analyse properties of thin SnTe layers and PbTe/SnTe heterostructures grown by MBE on BaF_{2}(111) substrates. Reflection high energy electron diffraction patterns registered during MBE growth of the samples as well as post-growth X-ray diffraction measurements evidence a high structural perfection of 0.6 μm thick SnTe layers and (50 Å PbTe)/(50 Å SnTe) superlattices. The full width at half maximum values of (222) X-ray rocking curves measured for these thin SnTe layers crystallized in the optimal MBE growth conditions are about 300 arcsec; the carrier concentrations can be tuned from 5×10^{19} cm^{-3} to 10^{2 1} cm^{-3} depending on the MBE process parameters.

18

MBE Growth and Properties of ZnYbTe Layers

40%

Sadowski J., Szamota-Sadowska K., Świątek K., Kowalczyk L., Abounadi A., Rajira A.

Acta Physica Polonica A

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1996

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vol. 90

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issue 5

1060-1064

EN

The MBE grown ZnYbTe layers were characterized by X-ray diffraction, photoluminescence and reflectivity measurements. The MBE growth conditions allowing to obtain monocrystalline ZnYbTe layers were found to be metal-rich (MBE growth with excess of Zn flux). In optical measurements (photoluminescence, reflectivity), both transitions connected with ternary ZnYbTe compound and with Yb^{3+} ions were detected. The quality of ZnYbTe layers with Yb content of 3% and 1% is inferior to the quality of pure ZnTe MBE layers, which is clearly seen in the results of photoluminescence and reflectivity measurements. In the ZnYbTe layers with 3% Yb, exhibiting monocrystalline character in reflection high-energy electron diffraction and X-ray diffraction measurements, optical transitions characteristic of pure YbTe were detected. In ZnYbTe layers with 1% Yb, no transitions connected with YbTe were observed.

19

40%

Kwiatkowski A., Borysiuk J., Bożek R., Wasik D., Kamińska M., Sadowski J., Twardowski A.

Acta Physica Polonica A

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2006

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vol. 110

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issue 2

233-236

EN

We report on cross-sectional transmission electron microscopy and magnetic force microscopy studies performed on self-organized MnAs nanoclusters embedded in GaAs. It was found that 10÷20 nm large MnAs ferromagnetic nanocrystals were formed during rapid thermal annealing of Ga_{1-x}Mn_xAs layers at 600ºC, leading to magnetic contrasts in magnetic force microscopy images.

20

Influence of Epitaxial Strain on Magnetic Anisotropy in (Ga,Mn)As

40%

Juszyński P., Wasik D., Gryglas-Borysiewicz M., Przybytek J., Szczytko J., Twardowski A., Sadowski J.

Acta Physica Polonica A

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2012

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vol. 122

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issue 6

1004-1006

EN

Two (Ga,Mn)As samples having different magnetic anisotropy (one with in-plane easy axis and another one with out-of-plane easy axis) were studied by means of magnetotransport experiments. Anisotropy field B_{A} was determined for both samples as a function of temperature. For the sample having in-plane easy axis, an inversion of the direction of planar Hall effect hysteresis was observed upon increase of temperature. This result was simulated using the Stoner-Wohlfarth model.

Refine search results

GaMnAs: Layers, Wires and Dots

Application of microarray technology in plant genes expression

Electrically Detected Magnetic Resonance

Observation of Vacancies in Ga_{1-x}Mn_xAs with Positron Annihilation Spectroscopy

Growth Processes of ZnTe Epilayers Deposited by MBE on GaAs(100) Vicinal Surfaces - Studies by Static and Dynamic RHEED

MBE Growth of YbTe on GaAs(100) and BaF_{2}(111) Substrates

Comparative sequencing of genomes: generating of INDEL and SNP genetic markers

Optical Pump - Terahertz Probe Measurement of the Electron Dynamics in Ga_{1-x}Mn_xAs

Ferromagnetic, Ferrimagnetic and Spin-wave Resonances in GaMnAs Layers

Magnetic Resonance Studies of the Origin of Ferromagnetism in Ga_{1-x}Mn_xAs

Zn(Mn)O Surface Alloy Studied by Synchrotron Radiation Photoemission

Magnetic Properties of Short Period InGaMnAs/InGaAs Superlattices

MBE Growth and Properties of GaMnAs(100) Films

MnAs Nanocrystals Embedded in GaAs

Off-Axis Electron Holography of Magnetic Nanostructures: Magnetic Behavior of Mn Rich Nanoprecipitates in (Mn,Ga)As System

Interval Identification of FMR Parameters for Spin Reorientation Transition in (Ga,Mn)As

Structural and Electrical Properties of Low Concentration SnTe Layers and PbTe/SnTe Heterostructures Grown by MBE

MBE Growth and Properties of ZnYbTe Layers

Influence of Epitaxial Strain on Magnetic Anisotropy in (Ga,Mn)As