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Your search keyword '"Stępniewski, R."' showing total 145 results
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145 results on '"Stępniewski, R."'

1. Direction-sensitive graphene flow sensor

Author

Kaźmierczak, P., Binder, J., Boryczko, K., Ciuk, T., Strupiński, W., Stępniewski, R., and Wysmołek, A.

Subjects
Physics - Applied Physics, Condensed Matter - Materials Science
Abstract

Graphene flow sensors hold great prospects for applications, but also encounter many difficulties, such as unwanted electrochemical phenomena, low measurable signal and limited dependence on the flow direction. This study proposes a novel approach allowing for the detection of a flow direction-dependent electric signal in aqueous solutions of salts, acids and bases. The key element in the proposed solution is the use of a reference electrode which allows external gating of the graphene structure. Using external gating enables to enhance substantially the amplitude of the flow-generated signal. Simultaneous measurement of the reference electrode current allows us to recover a flow-direction-sensitive component of the flow-induced voltage in graphene. The obtained results are discussed in terms of the Coulomb interaction and other phenomena which can be present at the interface of graphene with the aqueous solution., Comment: 7 pages, 6 figures

Published
2023

2. Excitonic luminescence of iodine-intercalated HfS$_2$

Author

Zawadzka, N., Woźniak, T., Strawski, M., Antoniazzi, I., Grzeszczyk, M., Olkowska-Pucko, K., Muhammad, Z., Ibanez, J., Zhao, W., Jadczak, J., Stępniewski, R., Babiński, A., and Molas, M. R.

Subjects
Condensed Matter - Materials Science, Condensed Matter - Mesoscale and Nanoscale Physics
Abstract

Photoluminescence from bulk HfS$_2$ grown by the chemical vapor transport method is reported. A series of emission lines is apparent at low temperature in the energy range of 1.4 - 1.5 eV. Two groups of the observed excitonic transitions followed by their replicas involving acoustic and optical phonons are distinguished using classical intensity correlation analysis. The emission is attributed to the recombination of excitons bound to iodine (I$_2$) molecules intercalated between layers of HfS$_2$. The I$_2$ molecules are introduced to the crystal during the growth as halogen transport agents in the growth process. Their presence in the crystal is confirmed by secondary ion mass spectroscopy., Comment: 5 pages, 6 figures + SM

Published
2022
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3. In-situ Raman Spectroscopy of the Graphene / Water Interface of a Solution-Gated Field Effect Transistor: Electron-Phonon Coupling and Spectroelectrochemistry

Author

Binder, J., Urban, J. M., Stepniewski, R., Strupinski, W., and Wysmolek, A.

Subjects
Condensed Matter - Mesoscale and Nanoscale Physics
Abstract

We present a novel measurement approach which combines the electrical characterization of solution-gated field effect transistors based on epitaxial bilayer graphene on 4H-SiC (0001) with simultaneous Raman spectroscopy. By changing the gate voltage, we observed Raman signatures related to the resonant electron-phonon coupling. An analysis of these Raman bands enabled the extraction of the geometrical capacitance of the system and an accurate calculation of the Fermi levels for bilayer graphene. An intentional application of higher gate voltages allowed us to trigger electrochemical reactions, which we followed in-situ by Raman spectroscopy. The reactions showed a partially reversible character, as indicated by an emergence / disappearance of peaks assigned to C-H and Si-H vibration modes as well as an increase / decrease of the defect-related Raman D band intensity. Our setup provides a highly interesting platform for future spectroelectrochemical research on electrically induced sorption processes of graphene on the micrometer scale.

Published
2014
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5. Magnetotransport in graphene on silicon side of SiC

Author

Vasek, P., Smrcka, L., Svoboda, P., Jurka, V., Orlita, M., Maude, D. K., Strupinski, W., Stepniewski, R., and Yakimova, R.

Subjects
Condensed Matter - Mesoscale and Nanoscale Physics
Abstract

We have studied the transport properties of graphene grown on silicon side of SiC. Samples under study have been prepared by two different growth methods in two different laboratories. Magnetoresistance and Hall resistance have been measured at temperatures between 4 and 100 K in resistive magnet in magnetic fields up to 22 T. In spite of differences in sample preparation, the field dependence of resistances measured on both sets of samples exhibits two periods of magneto-oscillations indicating two different parallel conducting channels with different concentrations of carriers. The semi-quantitative agreement with the model calculation allows for conclusion that channels are formed by high-density and low-density Dirac carriers. The coexistence of two different groups of carriers on the silicon side of SiC was not reported before., Comment: 5 pages, 6 figures, accepted for publication in the "IOP Journal of Physics: Conference series" as a contribution to the proceedings of the 20th International Conference on "High Magnetic Fields in Semiconductor Physics", HMF 20

Published
2012
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6. Quasi-classical cyclotron resonance of Dirac fermions in highly doped graphene

Author

Witowski, A. M., Orlita, M., Stepniewski, R., Wysmolek, A., Baranowski, J. M., Strupinski, W., Faugeras, C., Martinez, G., and Potemski, M.

Subjects
Condensed Matter - Mesoscale and Nanoscale Physics, Condensed Matter - Materials Science
Abstract

Cyclotron resonance in highly doped graphene has been explored using infrared magnetotransmission. Contrary to previous work, which only focused on the magneto-optical properties of graphene in the quantum regime, here we study the quasi-classical response of this system. We show that it has a character of classical cyclotron resonance, with an energy which is linear in the applied magnetic field and with an effective cyclotron mass defined by the position of the Fermi level m = E_F/v_F^2., Comment: 6 pages, 4 figures

Published
2010
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8. Excitonic luminescence of iodine-intercalated HfS2

Author

National Science Centre (Poland), National Natural Science Foundation of China, Zawadzka, N., Woźniak, T., Strawski, M., Antoniazzi, Igor, Grzeszczyk, M., Olkowska-Pucko, K., Muhammad, Z., Ibáñez Insa, Jordi, Zhao, W., Jadczak, J., Stępniewski, R., Babiński, A., Molas, M. R., National Science Centre (Poland), National Natural Science Foundation of China, Zawadzka, N., Woźniak, T., Strawski, M., Antoniazzi, Igor, Grzeszczyk, M., Olkowska-Pucko, K., Muhammad, Z., Ibáñez Insa, Jordi, Zhao, W., Jadczak, J., Stępniewski, R., Babiński, A., and Molas, M. R.

Abstract

Photoluminescence from bulk HfS2 grown by the chemical vapor transport method is reported. A series of emission lines is apparent at low temperature in the energy range of 1.4-1.5 eV. Two groups of the observed excitonic transitions followed by their replicas involving acoustic and optical phonons are distinguished using classical intensity correlation analysis. The emission is attributed to the recombination of excitons bound to iodine (I2) molecules intercalated between layers of HfS2. The I2 molecules are introduced to the crystal during the growth as halogen transport agents in the growth process. Their presence in the crystal is confirmed by secondary ion mass spectroscopy.

Published
2023

9. Excitonic luminescence of iodine-intercalated HfS2

Author

Zawadzka, N., primary, Woźniak, T., additional, Strawski, M., additional, Antoniazzi, I., additional, Grzeszczyk, M., additional, Olkowska-Pucko, K., additional, Muhammad, Z., additional, Ibanez, J., additional, Zhao, W., additional, Jadczak, J., additional, Stępniewski, R., additional, Babiński, A., additional, and Molas, M. R., additional

Published
2023
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11. Excitonic luminescence of iodine-intercalated HfS2.

Author

Zawadzka, N., Woźniak, T., Strawski, M., Antoniazzi, I., Grzeszczyk, M., Olkowska-Pucko, K., Muhammad, Z., Ibanez, J., Zhao, W., Jadczak, J., Stępniewski, R., Babiński, A., and Molas, M. R.

Subjects
ACOUSTIC phonons, LUMINESCENCE, MASS spectrometry, CRYSTAL growth, EXCITON theory
Abstract

Photoluminescence from bulk HfS2 grown by the chemical vapor transport method is reported. A series of emission lines is apparent at low temperature in the energy range of 1.4–1.5 eV. Two groups of the observed excitonic transitions followed by their replicas involving acoustic and optical phonons are distinguished using classical intensity correlation analysis. The emission is attributed to the recombination of excitons bound to iodine (I2) molecules intercalated between layers of HfS2. The I2 molecules are introduced to the crystal during the growth as halogen transport agents in the growth process. Their presence in the crystal is confirmed by secondary ion mass spectroscopy. [ABSTRACT FROM AUTHOR]

Published
2023
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23. Growth of Gan MOCVD Layers on Gan Single Crystals

Author

Pakuła, K., primary, Wysmołek, A., additional, Korona, P. P., additional, Baranowski, J. M., additional, Stępniewski, R., additional, Grzegory, I., additional, Boćkowski, M., additional, Jun, J., additional, Krukowski, S., additional, Wróblewskl, M., additional, and Porowski, S., additional

Published
1996
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25. Structural defects in epitaxial graphene layers synthesized on C-terminated 4H-SiC (0001) surface--Transmission electron microscopy and density functional theory studies.

Author

Borysiuk, J., Sołtys, J., Piechota, J., Krukowski, S., Baranowski, J. M., and Stępniewski, R.

Subjects
GRAPHENE synthesis, MULTILAYERS, CRYSTAL defects, SILICON carbide, CRYSTAL grain boundaries, EDGE dislocations, DENSITY functional theory, TRANSMISSION electron microscopy
Abstract

The principal structural defects in graphene multilayers synthesized on the carbon-terminated face of a 4H-SiC (0001) substrate were investigated using the high-resolution transmission electron microscopy. The analyzed systems include a wide variety of defected structures such as edge dislocations, rotational multilayers, and grain boundaries. It was shown that graphene layers are composed of grains of the size of several nanometres or larger; they differ in a relative rotation by large angles, close to 30°. The structure of graphene multilayers results from the synthesis on a SiC (0001) surface, which proceeds via intensive nucleation of new graphene layers that coalesce under various angles creating an immense orientational disorder. Structural defects are associated with a built-in strain resulting from a lattice mismatch between the SiC substrate and the graphene layers. The density functional theory data show that the high-angular disorder of AB stacked bilayers is not restoring the hexagonal symmetry of the lattice. [ABSTRACT FROM AUTHOR]

Published
2014
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26. Transmission electron microscopy investigations of epitaxial graphene on C-terminated 4H–SiC.

Author

Borysiuk, J., Bożek, R., Grodecki, K., Wysmołek, A., Strupiński, W., Stępniewski, R., and Baranowski, J. M.

Subjects
GRAPHENE, SILICON carbide, TRANSMISSION electron microscopy, SUBSTRATES (Materials science), CARBON
Abstract

Transmission electron microscopy (TEM) investigations of epitaxial graphene, grown on on-axis and 8° off-axis C-terminated 4H–SiC [formula] surfaces are presented. The TEM results provide evidence that the first carbon layer is separated by 3.2 Å from the C-terminated SiC surface. It was also found that thick graphene layers grown on on-axis SiC [formula] are loosely bound to the SiC substrate. Moreover, the structural observations reveal a certain degree of disorder between the graphene planes, which manifests itself in a rotation of the layers and in an increase in the interplanar spacing between certain carbon layers from 3.35 Å, which is characteristic for graphite, up to 3.7 Å. Graphene grown on 8° off-axis SiC [formula] substrates covers the steps of SiC and as a result disorder seems to be not as pronounced as it is on the on-axis SiC [formula] substrate. [ABSTRACT FROM AUTHOR]

Published
2010
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30. Charge Transfer in 1T-TaS2/Graphene Hybrid Structures Studied by Spatially Resolved Raman Spectroscopy.

Author

ROGOŻA, J., ŁACIŃSKA, E. M., BINDER, J., LUTSYK, I., ROGALA, M., DABROWSKI, P., KLUSEK, Z., KOWALCZYK, P. J., STRUPIŃSKI, W., STĘPNIEWSKI, R., and WYSMOŁEK, A.

Subjects
RAMAN spectroscopy, CHARGE transfer, CARRIER density, TANTALUM, GRAPHENE
Abstract

Graphene/1T-TaS2 hybrid structures were measured using the Raman spectroscopy at room temperature. Spatially resolved Raman maps show that the region for which an effective graphene G band shift was observed correlates well with the tantalum disulfide flake, suggesting a change of the carrier concentration in graphene induced by 1T-TaS2. This effect was observed only for the sample exfoliated in vacuum, which signifies the necessity of preventing tantalum disulfide from oxidation during sample preparation. [ABSTRACT FROM AUTHOR]

Published
2021
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34. Graphene Based Flow Sensors

Author

Kaźmierczak, P., primary, Binder, J., additional, Boryczko, K., additional, Ciuk, T., additional, Strupiński, W., additional, Stępniewski, R., additional, and Wysmołek, A., additional

Published
2014
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48. Control of Photon Polarization in GaAs/AlAs Single Quantum Dot Emission

Author

Suffczyński, J., primary, Trajnerowicz, A., additional, Kazimierczuk, T., additional, Piętka, B., additional, Kowalik, K., additional, Kossacki, P., additional, Golnik, A., additional, Nawrocki, M., additional, Gaj, J.A., additional, Wysmołek, A., additional, Stępniewski, R., additional, Potemski, M., additional, and Thierry-Mieg, V., additional

Published
2007
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50. Magnetopolaron effect on shallow donors in GaN

Author

Wysmołek, A., primary, Stępniewski, R., additional, Potemski, M., additional, Chwalisz-Piętka, B., additional, Pakuła, K., additional, Baranowski, J. M., additional, Look, D. C., additional, Park, S. S., additional, and Lee, K. Y., additional

Published
2006
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