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  1. 109 Acta Physica Polonica A

  2. 1 Biotechnologia

  3. 1 Bulletin of the Polish Academy of Sciences: Technical Sciences

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  4. 13 2011

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  1. 111 Godlewski M.

  2. 25 Guziewicz E.

  3. 24 Monemar B.

  4. 21 Ivanov V.

  5. 18 Witkowski B.

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1
Content available remote

Electroluminescence from Rare Earth Activated Materials - New Concepts

100%
Godlewski M.
Acta Physica Polonica A
|
1993
|
vol. 84
|
issue 3
435-444
EN
The recent progress in the field of thin film electroluminescence devices is reviewed. The mechanisms responsible for rare earth excitation in high electric field electroluminescence structures are explained. A new mechanism including rare earth ionization is described. Processes limiting electroluminescence efficiency are also discussed.
2
Content available remote

Charge Transfer States of Transition Metal and Rare Earth Ions: Their Role in Recombination Processes

100%
Godlewski M.
|
EN
Center ionization accompanied by carrier localization at the center by virtue of a short-range or a long-range Coulomb attractive potential is discussed. The role of charge transfer states in recombination processes is described. The source of carrier attractive potential is explained and a simple theoretical model is presented allowing to predict the nature (either electron or hole attractive) of this potential. The probability of different possible recombination paths is also analyzed.
3
Content available remote

Recombination Processes in ZnSe:Eu

64%
Świątek K., Godlewski M.
Acta Physica Polonica A
|
1991
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vol. 80
|
issue 3
381-384
EN
The photo-ESR and photoluminescence experiments have been performed on high-resistivity ZnSe:Eu crystals. We report the first evidence that the energy level of Eu^{2+} ground state is located within the ZnSe forbidden gap, approximately 2.1 eV below the bottom of the conduction band.
4
Content available remote

Mechanism of Carrier Heating in High Electric Field Electroluminescence Devices

64%
Dedulewicz S., Godlewski M.
Acta Physica Polonica A
|
1992
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vol. 82
|
issue 5
865-867
EN
The mechanism of carrier heating in ZnS-based electroluminescence devices is discussed. We show that carrier acceleration by an applied electric field is at 300 K not a loss-free (ballistic carriers) process. Even for large carrier energies (about 2.5 eV) inelastic scattering on polar optical phonons dominates over elastic scattering on acoustic phonons and ionized impurities.
5
Content available remote

Efficient Two-Center Auger Mechanism of Electron Trapping by Fe^{3+} Ions in ZnSe:Fe,Cr

64%
Surma M., Godlewski M.
Acta Physica Polonica A
|
1997
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vol. 92
|
issue 5
1017-1020
EN
A detailed analysis of decay kinetics of light induced electron spin resonance signals of Cr^{1+} and Fe^{3+} ions in ZnSe:Fe,Cr is given. We observe that the Cr^{1+} electron spin resonance signal decays once free electrons are thermally ionized from shallow donors of ZnSe. Such unusual behavior of the Cr^{1+} electron spin resonance signal is explained by efficient two-center Auger recombination: the Cr^{1+} center is ionized due to the Auger-type energy transfer from the electron being trapped by the Fe^{3+} ion. Such process is shown to be consistent with the temperature dependence of the decay times of electron spin resonance signals. Its quantum efficiency is estimated to be as large as 18% for Cr and Fe concentrations which were studied.
6
Content available remote

Carrier Heating Efficiency in Optically Detected Cyclotron Resonance Experiment

64%
Dedulewicz S., Godlewski M.
Acta Physica Polonica A
|
1993
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vol. 84
|
issue 3
535-537
EN
Monte Carlo calculations of carrier heating efficiency in optically detected cyclotron resonance experiment are presented. It is shown that electrons accelerated by microwave electric field gain energy sufficient for impact ionization of shallow centers and for exciton dissociation. It is also explained why very sharp thresholds for impact processes were observed in the optically detected cyclotron resonance investigations.
7
Content available remote

Thermal Donor Generation in Boron- and Aluminium-Doped Czochralski Silicon

52%
Kopalko K., Kaczor P., Godlewski M., Gregorkiewicz T.
Acta Physica Polonica A
|
1991
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vol. 80
|
issue 3
345-348
EN
Generation of thermal donor centres in oxygen-rich silicon doped with boron and aluminium acceptors has been studied with the FTIR technique. It has been found that upon annealing 470°C two kinds of absorption series were generated. One of them belonged to the well-known first ionization level of silicon thermal (double) donors (TD's): TD°/TD^{+} . The second series was identified with the so-called shallow thermal donors (STD's). The generation kinetics of the two series was followed for both kinds of acceptor doping and significant differences has been found. The results of the FTIR investigations were further compared with the magnetic resonance findings allowing for their mutual correlation and more general conclusions.
8
Content available remote

Optically Detected Magnetic Resonance Studies of Te-Related Shallow Donors in Al_{x}Ga_{1-x}As

52%
Godlewski M., Fronc K., Chen W., Monemar B.
Acta Physica Polonica A
|
1991
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vol. 80
|
issue 3
341-344
EN
The first studies of the Optically Detected Magnetic Resonance (ODMR) of Te-doped (x = 0.42) are presented. The ODMR data indicate an efficient energy transfer between epilayer and GaAs substrate.
9
Publication available in full text mode
Content available

Electronic Structure of ZnS:Co Semiconductors: X-ray and Optical Spectroscopy Studies

52%
Surkova T., Galakhov V., Godlewski M.
Acta Physica Polonica A
|
2003
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vol. 103
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issue 6
703-708
EN
Experimental studies of X-ray photoelectron and Co L_α X-ray emission spectra of the ZnS:Co semiconductor were carried out. It was established that Co ions are in a Co^{2+} configuration and that the Co 3d impurity states are localized above the top of the valence band by 1.0±0.2 eV.
10
Content available remote

Influence of Annealing on Optical Properties of ZnO Nanorods Obtained by the Microwave-Assisted Hydrothermal Process

52%
Materska P., Witkowski B., Godlewski M.
Acta Physica Polonica A
|
2016
|
vol. 130
|
issue 5
1202-1204
EN
Optical properties of ZnO nanorods (of different sizes, grown on two different substrates) are investigated. Nanorods were grown using microwave-assisted hydrothermal process on gallium nitride or silicon substrate. To initiate nanorods growth on a silicon substrate ZnO nucleation layer was used. ZnO nanoseeds were deposited by atomic layer deposition. For GaN substrate an epitaxial relation was observed. For both substrates nanorods show a hexagonal structure, expected for wurtzite ZnO. Results of nanorods annealing are discussed.
11
Content available remote

SrS:Eu and CaS:Eu Thin Films: Influence of Host Lattice on Kinetics of Europium Emission

52%
Świątek K., Godlewski M., Niinistö L., Leskelä M.
Acta Physica Polonica A
|
1992
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vol. 82
|
issue 5
769-772
EN
In this paper we report the studies of photoluminescent properties of CaS:Eu and SrS:Eu thin films containing up to 3 mole % of Eu, grown by the atomic layer epitaxy method. The energy transfer and direct intrashell excitation channels of Eu ions are examined in function of temperature.
12
Content available remote

Electron Spin Resonance Studies of Te Doped AlGaAs Epilayers

52%
Surma M., Godlewski M., Żytkiewicz Z.
Acta Physica Polonica A
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1992
|
vol. 82
|
issue 5
817-820
EN
Results of electron spin resonance studies of tellurium doped AlGaAs epilayers are presented. We demonstrate a new approach to the studies of shallow donor-deep DX level transformation upon illumination or with an increase in temperature. The processes can be monitored by observing the changes of magnitude of an unidentified ESR signal of AlGaAs.
13
Content available remote

Nature of Blue Anti-Stokes Luminescence in ZnSe:Cr

52%
Ivanov V. Y., Semenov Y. G., Surma M., Godlewski M.
Acta Physica Polonica A
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1995
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vol. 88
|
issue 4
743-746
EN
The mechanism of the anti-Stokes photoluminescence in ZnSe:Cr is dis­cussed. It is shown that the two-step ionization transitions of Cr(2^{+} ↔ 1^{+}) result in appearance of the blue anti-Stokes photoluminescence of ZnSe:Cr. There are also some indications that the Auger type co-operative process can contribute to the photoluminescence excitation.
14
Content available remote

ZnO Nanopowders by a Microwave Hydrothermal Method - Influence of the Precursor Type on Grain Sizes

52%
Wolska E., Witkowski B., Godlewski M.
Acta Physica Polonica A
|
2011
|
vol. 119
|
issue 5
683-685
EN
Two series of ZnO nanopowders obtained by a microwave hydrothermal method are examined. We used two different zinc precursors (zinc chloride (ZnCl_2) and zinc nitrate hexahydrate (N_2O_6Zn·6H_2O)). Both types of nanopowders show a bright emission in a visible light, including the band edge emission, which indicates their good crystallographic quality. Results of scanning electron microscopy, photo- and cathodoluminescence investigations are presented.
15
Content available remote

Hot Carrier Effects in Optically Detected Cyclotron Resonance Studies of III-V Semiconductors

52%
Karpińska K., Dedulewicz S., Godlewski M.
Acta Physica Polonica A
|
1992
|
vol. 82
|
issue 4
623-626
EN
The mechanisms of irregular photoluminescence intensity oscillations, as observed in optically detected cyclotron resonance experiments, are discussed. Two possible scenarios are analyzed, both requiring impact ionization of the center(s) by electric field accelerated free carriers. The first assumes coexistence of dielectric and energy relaxation processes. The second assumes a subsequent impact ionization of two different centers.
16
Content available remote

Transition Metal Impurities and Electronic Structure of ZnSe-Based Isovalent Semiconductor Alloys

52%
Surkova T. P., Giriat W., Godlewski M., Permogorov S.
Acta Physica Polonica A
|
1997
|
vol. 92
|
issue 5
1009-1012
EN
Energy level positions of the nickel 2+/1+ and cobalt 2+/3+ charge states have been used to estimate band edges for the valence and conduction bands of ZnSe-based alloys with cation (ZnCdSe) and anion (ZnSSe) substitution. Chemical trends in band offsets of heterostructures of Zn- or Mn-based II-VI compounds are analysed. Further on, the change of Ni^{2+}(3d^{8}) and Co^{2+}(3d^{7}) intra-d shell transition bands upon the alloying of host material is discussed.
17
Content available remote

Infrared Absorption Study of Thermally Generated Shallow Donor Centers in Czochralski Silicon

52%
Kaczor P., Kopalko K., Godlewski M., Gregorkiewicz T.
Acta Physica Polonica A
|
1992
|
vol. 82
|
issue 4
677-680
EN
A comparative study of thermally generated donor centers in boron and aluminum doped Czochralski silicon was performed by means of Fourier transform infrared technique. A detailed study revealed presence of donor centers belonging to the well-known series of thermal donors and shallow thermal donors. For both types of material the same centers could be observed while considerable differences in their generation kinetics occurred. In addition to the previously identified species also new ones could be observed. One of them, with single ionization level at approximately 39.5 meV, was found to exhibit clear dependence of its concentration upon illumination of the sample during cooling from room temperature to liquid He temperature.
18
Content available remote

ESR Study of the Magnetic Properties of the CdTe/CdMnTe Multi Quantum Wells

52%
Surma M., Godlewski M., Waag A.
Acta Physica Polonica A
|
1993
|
vol. 84
|
issue 3
543-546
EN
The results of electron spin resonance investigations of bulk Cd_{1-x}Mn_{x}Te and of molecular beam epitaxy grown CdTe/CdMnTe single 2 μm thick layer and multi quantum well with Mn concentrations of about x = 0.10 are compared. The Mn^{2+} electron spin resonance spectrum of the MQW CdTe/CdMnTe shows several features different from those observed in the CdMnTe bulk sample. The Mn^{2+} resonance shows a small anisotropy of position and width with the anisotropy axis normal to the heterointerface. The temperature dependence of the width of the electron spin resonance line is also different from that observed for the bulk and for the thick single layer.
19
Content available remote

Fe^{2+} → Fe^{3+} Ionization Transition in ZnSe

52%
Surma M., Godlewski M., Surkova T.
Acta Physica Polonica A
|
1993
|
vol. 84
|
issue 3
547-550
EN
Detailed photo-ESR study of iron and chromium impurities in ZnSe is presented. The energy level position of Fe 2+/3+ energy level is determined. The role of iron and chromium impurities in nonradiative recombination processes is discussed.
20
Publication available in full text mode
Content available

Spin Relaxation Processes in Quantum Well Structures of Cd_{1-x}Mn_xTe/Cd_{1-x}Mg_xTe

52%
Khachapuridze A., Ivanov V., Godlewski M., Karczewski G.
|
|
issue 4-5
643-648
EN
Fast spin relaxation of Mn^{2+} ions in a magnetic quantum well of CdMnTe with 1% Mn fraction is related to a very efficient spin-flip interaction between Mn ions and free carriers. This mechanism of spin relaxation becomes dominant at increased excitation densities. The observed response of the photoluminescence bands to the Mn^{2+} magnetic resonance indicates that free carriers are heated at the magnetic resonance conditions. A decrease in formation/recombination rates of free and trion excitons is observed. Donor bound exciton photoluminescence is enhanced, which we relate to delocalization of free excitons, caused by interaction with microwave heated free carriers.
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