M. Godlewski

Polish Academy of Sciences, Warszawa, Masovian Voivodeship, Poland

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Publications (431)648.7 Total impact

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    ABSTRACT: The theoretical approach towards improving the photovoltaic response of n-ZnO/p-Si heterojunctions proposed by Knutsen et al. [Phys. Status Solidi A 210 (2013) 585–588] has been experimentally tested. AZO/n-Zn(1−x)MgxO layers were deposited at 160 °C on p-Si substrates by atomic layer deposition (ALD) with magnesium concentration in the 0–4 at% range. The examined devices showed a reduction of the conduction band offset from (0.63±0.03) eV to (0.48±0.03) eV. This decrease leads to a diminishing impact of recombination centers at the interface between zinc oxide based layers and silicon substrate, when the Mg content is below ~1.6 at%. In this range, the overall photovoltaic efficiency increased from ~3.7% to ~6.0%. As a next step, we tested solar cells with similar magnesium concentration in the Zn(1−x)MgxO layer, but deposited at 300 °C. Due to the higher deposition temperature, a further 1.1% increase in efficiency has been obtained. So far, this is the highest reported efficiency for a ZnO/Si heterojunction grown by ALD method, thus experimentally confirming the validity of the approaches here studied for raising the efficiency of heterojunctions solar cells based on n-ZnO/p-Si, while significantly reducing the fabrication complexity respect to conventional Si based devices as emphasized by Hussain et al. [Sol. Energy Mater. Sol. Cells 139 (2015) 95–100].
    No preview · Article · Apr 2016 · Solar Energy Materials and Solar Cells
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    ABSTRACT: Thermally induced crystallization of cubic Eu2O3 obtained with the microwave hydrothermal method has been investigated. The starting material crystallized in the form of needle-shaped agglomerates of nanocrystalline hexagonal Eu(OH)3. Thermal treatment up to 800 °C induced the crystallization of cubic Eu2O3, after further calcination at 1200 °C in the air a monoclinic phase appeared. The phase transformation caused abnormal reduction of Eu3+ ions, related to the oxygen vacancy creation during sintering of the oxide crystallites. The crystallization process of cubic Eu2O3 occurred within the agglomerates without change of their shapes. The cubic form exhibited bright emission of Eu3+ related luminescence with intensity increasing with the size of crystallites.
    No preview · Article · Jan 2016
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    ABSTRACT: Europium doped ZnO nanopowders made by microwave hydrothermal method are investigated. As zinc oxide precursor zinc nitrate(V) hexahydrate (Zn(NO3)2·6H2O) was used. Two types of nanopowder samples are examined: as grown and annealed at 750 °C in air atmosphere. We investigate the structural, morphological and optical prosperities of europium doped ZnO. Results of scanning electron microscopy, X-ray diffraction, photo- and cathodoluminescence investigations and also CIE1961 chromaticity diagram are presented.
    No preview · Article · Jan 2016
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    ABSTRACT: In this paper a new generation of non-toxic nanoparticles based on the zirconium oxide doped with 0.5%Tb and co-doped by the range of 0–70% with Y was evaluated for the use as a fluorescent biomarker of neuronal trafficking. The ZrO2:Tb nanoparticles were created by microwave driven hydrothermal method. Influence of the yttrium content and thermal processing on the Tb3+ related luminescence emission was discussed. The higher intensities were achieved, when host was cubic and for the nanoparticles with 33 nm. Presence of yttrium was associated with the energy coupling of the host and dopant, wide excitation band is present at 309 and 322 nm before and after calcination respectively. For the experiment on living primary neurons, nanoparticles doped with 0.5%Tb and 7%Y were chosen based on their luminescence emission intensity. Recently transfer of the nanoparticles through the barriers in the organism including blood–brain barrier following their alimentary absorption was confirmed (Godlewski and Godlewski, 2012). This raised the possibility of the nanoparticle application as a tool in the neuroscience, and the question of potential mechanisms of nanoparticle turnover in neurons. Concentration of 0.001 mg/ml of ZrO2:0.5%Tb 7%Y in growth medium was added to the primary murine culture medium, and the intracellular trafficking of nanoparticles was observed following 15 min pre-incubation period. ZrO2:0.5%Tb 7%Y nanoparticles were dynamically absorbed by the neurons and the dynamic passage of transport vesicles containing ZrO2:0.5%Tb 7%Y nanoparticles was observed along the neuronal processes and in between two neighbouring neurons. Reassuming, the ZrO2:0.5%Tb 7%Y nanoparticles proved to be biocompatible and a valid tool to assess intracellular trafficking dynamics in the neurobiology.
    Full-text · Article · Jan 2016 · Optical Materials
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    ABSTRACT: This paper is devoted to the development of standard and inverted polymer solar cells based on polyazomethine (PAZ-Car-TPA), poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl C61 butyric acid methyl ester (PCBM). We analyzed the influence of: (i) PEDOT:PSS or MoO3 as a hole transporting layer in standard devices, (ii) aluminum doping level (from 0 to 3.7%) in ZnO (obtained by atomic layer deposition, ALD) applied as an electron transporting layer in inverted solar cells and (iii) the method applied to obtain ZnO layer (ALD or sol-gel) on its photovoltaic properties. The best device configuration is ITO/AZO (3% Al)/P3HT:PCBM/MoO3/Ag which exhibits a power conversion efficiency of 1.51% under 100 mW/cm2 AM 1.5 G simulated solar emission. Devices were additionally tested by electrochemical impedance spectroscopy. HOMO-LUMO levels of PAZ-Car-TPA and its mixture with HCl, H2SO4, p-toluenesulfonic acid, PEDOT:PSS and water were analyzed by cyclic voltammetry and quantum mechanical calculations using Density Functional Theory method.
    No preview · Article · Jan 2016
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    Full-text · Dataset · Jan 2016
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    ABSTRACT: Microwave hydrothermal growth of Y2O3 crystallites results in needle-shaped aggregates of μm length. Thermal treatment has little influence on the material microstructure, but significant impact on the nanometric level. Nanoparticles doped with europium show an intense red luminescence, related to the 5D0 → 7F2 transition of Eu3+ ions. The luminescence intensity increases with the calcination temperature and is accompanied by increasing size of Y2O3:Eu crystallites. EPR studies show the absence of Eu2+ related signals in the material. Y2O3:Eu nanoparticles crystallized via a microwave hydrothermal method were employed as luminescent biomarkers in mice. The initial tests confirmed their applicability as biological markers. Persorption of the Y2O3:Eu nanoparticles after IG in the adult mouse duodenum, brain and liver is reported.
    Full-text · Article · Dec 2015 · Optical Materials
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    ABSTRACT: We report on the ground- and excited-state properties of Fe3+ centers in hydrothermally and chemical-vapor-transport grown single ZnO crystals studied by continuous-wave electron-paramagnetic resonance (EPR) under dark and laser-illuminated conditions, pulsed-EPR and magneto-photoluminescence. By use of EPR experiments, the fine-structure parameters of the Fe3+ spin Hamiltonian are determined. Three types of charge-compensated Fe3+ centers are identified and the charge conversion from Fe2+ to Fe3+ is highlighted. The magneto-optical studies of the Zeeman components of the spin-forbidden electric-dipole transitions from excited 4^T_1(G) to ground 6^A_1(6^S) states of the Fe3+ center indicate the trigonal symmetry of the fine structure of the lowest \Gamma_8(4^T_1) excited state. The energy positions of the Zeeman components are measured in the external magnetic field of 8 T rotated in (1210) and (0001) crystal planes. The angular variation of the Zeeman lines exhibits two magnetically nonequivalent Fe3+ centers. These features result from the contribution of high-rank Zeeman terms of dimension BJ^3 in the spin Hamiltonian. For the electron spin S = 5/2 system of the trigonal Fe3+ ion, we further demonstrate the tuning of one-photon Rabi oscillations by means of electron spin-echo measurements.
    Full-text · Article · Nov 2015 · Phys Rev B. Solid State
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    ABSTRACT: Zinc oxide nanopowders doped with 1–15 mol % cobalt were produced by the microwave solvothermal synthesis (MSS) technique. The obtained nanoparticles were annealed at 800 °C in nitrogen (99.999%) and in synthetic air. The material nanostructure was investigated by means of the following techniques: X-ray diffraction (XRD), helium pycnometry density, specific surface area (SSA), inductively coupled plasma optical emission spectrometry (ICP-OES), extended X-ray absorption fine structure (EXAFS) spectroscopy, scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) and with magnetometry using superconducting quantum interference device (SQUID). Irrespective of the Co content, nanoparticles in their initial state present a similar morphology. They are composed of loosely agglomerated spherical particles with wurtzite-type crystal structure with crystallites of a mean size of 30 nm. Annealing to temperatures of up to 800 °C induced the growth of crystallites up to a maximum of 2 μm in diameter. For samples annealed in high purity nitrogen, the precipitation of metallic α-Co was detected for a Co content of 5 mol % or more. For samples annealed in synthetic air, no change of phase structure was detected, except for precipitation of Co3O4 for a Co content of 15 mol %. The results of the magentometry investigation indicated that all as-synthesized samples displayed paramagnetic properties with a contribution of anti-ferromagnetic coupling of Co–Co pairs. After annealing in synthetic air, the samples remained paramagnetic and samples annealed under nitrogen flow showed a magnetic response under the influences of a magnetic field, likely related to the precipitation of metallic Co in nanoparticles.
    Full-text · Article · Sep 2015 · Beilstein Journal of Nanotechnology
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    ABSTRACT: In this work, the analysis of the temperature-dependent electrical conductivity of highly crystalline zinc oxide (ZnO) thin films obtained by the Atomic Layer Deposition (ALD) method is performed. It is deduced that the most important scattering mechanisms are: scattering by ionized defects (at low temperatures) as well as by phonons (mainly optical ones) at higher temperatures. Nevertheless, the role of grain boundaries in the carrier mobility limitation ought to be included as well. These conclusions are based on theoretical analysis and temperature-dependent Hall mobility measurements. The presented results prove that existing models can explain the mobility behavior in the ALD-ZnO films, being helpful for understanding their transport properties, which are strongly related both to the crystalline quality of deposited ZnO material and defects in its lattice.
    No preview · Article · Jul 2015 · Journal of Applied Physics
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    ABSTRACT: Abstract In this paper, cheap and efficient photovoltaic cells based on ZnO/Si heterostructure are discussed. These cells contain zinc oxide nanorods (ZnONR) grown by a low temperature hydrothermal method on a p-type silicon surface. The hydrothermal method applied in the present work uses cheap precursors and allows reproducible and controllable growth of 3D systems. As-grown ZnONR on Si surface are uniformly covered by a zinc oxide (ZnO) layer followed by an aluminum doped zinc oxide (AZO) layer. The latter is deposited on top of the cell as transparent conductive oxide (TCO). Both zinc oxide and aluminum doped zinc oxide layers are grown by a low temperature atomic layer deposition (LT ALD) method. Thickness of ZnO layers is optimized to increase significantly the light-trapping effect and thus the photovoltaic (PV) response. We evaluate impact of ZnO thickness on the PV devices operation. It is found that PV efficiency increases when thickness of the ZnO layer changes from 50 nm to 500 nm. The best response of solar cells is achieved for a sample containing ZnO layer with a thickness equal to 500 nm. The overall photovoltaic response is 10.9% and can be further improved by contact and Si layer optimization.
    No preview · Article · Jul 2015 · Solar Energy Materials and Solar Cells
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    ABSTRACT: Thermally evaporated fullerene C60 porous films served as templates for a hybrid (molecular-inorganic) disordered blend formation. C60 films were covered with zinc oxide (ZnO) grown by atomic layer deposition. ZnO filled every pore in the C60 layer which led to the formation of C60–ZnO films with separate and distinguishable phases of C60 and ZnO constituents. Morphological, structural, optical, and electrical properties of the so-obtained films were investigated. Deposition of ZnO polycrystalline films on C60 porous layers resulted in the formation of ZnO with additional structural defects, compared to the films grown on planar substrates, which affected the electrical transport in the ZnO–C60 layers.
    No preview · Article · Jun 2015 · Journal of Materials Science
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    ABSTRACT: The test structures for photovoltaic (PV) applications based on zinc oxide nanorods (NRs) that were grown using a low-temperature hydrothermal method on p-type silicon substrates (100) covered with Ag nanoparticles (NPs) were studied. The NPs of three different diameters, i.e., 5–10 nm, 20-30 nm, and 50–60 nm, were deposited using a sputtering method. The morphology and crystallinity of the structures were confirmed by scanning electron microscopy and Raman spectroscopy. It was found that the nanorods have a hexagonal wurtzite structure. An analysis of the Raman and photoluminescence spectra permitted the identification of the surface modes at 476 cm−1 and 561 cm−1. The presence of these modes is evidence of nanorods oriented along the wurtzite c-axis. The NRs with Ag NPs were covered with a ZnO:Al (AZO) layer that was grown using the low-temperature atomic layer deposition technique. The AZO layer served as a transparent ohmic contact to the ZnO nanorods. The applicability of the AZO layer for this purpose and the influence of the Ag nanoparticles on the effectiveness of light acquisition by such prepared PV cells were checked by reflectance and transmittance measurements of the AZO/glass and AZO/NPs/glass reference structures. Based on these studies, the high-energy transmittance edge was assigned to the ZnO energy gap, although it is blueshifted with respect to the bulk ZnO energy gap because of Al doping. It was also shown that the most optimal PV performance is obtained from a structure containing Ag nanoparticles with a diameter of 20–30 nm. This result is confirmed by the current-voltage measurements performed with 1-sun illumination. The structures show a plasmonic effect within the short wavelength range: the PV response for the structure with Ag nanoparticles is twice that of the structure without the nanoparticles. However, the influence of the Ag nanoparticle diameters on the plasmonic effect is ambiguous.
    No preview · Article · May 2015 · Journal of Applied Physics
  • Vitalii Yu. Ivanov · Marek Godlewski · Alexander Dejneka
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    ABSTRACT: Electron Spin Resonance investigations allow to attribute a broad absorption band below the band-to-band transition of ZnO:Co to photoionization transitions of Co-ions. This absorption, with the onset at about 2.4–2.6 eV, is due to cobalt recharging, as concluded from the photo-ESR and pulsed ESR experiments. In these experiments light sensitive ESR signals of Co2+ and shallow donor are observed. Their response to light favors cobalt 2+ to 3+ photoionization.
    No preview · Article · May 2015 · physica status solidi (b)
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    ABSTRACT: We present results of cathodoluminescence (CL) investigations of high-quality zinc oxide (ZnO) nanorods obtained by an extremely fast hydrothermal method on a silicon substrate. A scanning electron microscopy (SEM) system equipped with CL allows direct comparison of SEM images and CL maps, taken from exactly the same areas of samples. Investigations are performed at a temperature of 5 K. An interlink between sample microstructure and emission properties is investigated. CL confirms a very high quality of ZnO nanorods produced by our method. In addition, the presence of super radiation effects in ZnO nanorod arrays is suggested.
    No preview · Article · Apr 2015 · Microscopy and Microanalysis
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    ABSTRACT: Abstract: In this paper, we discuss an impact of thin titanium dioxide (TiO2) coatings on refractive index (RI) sensitivity and biofunctionalization of long-period gratings (LPGs). The TiO2 overlays on the LPG surfaces have been obtained using atomic layer deposition (ALD) method. This method allows for a deposition of conformal, thickness-controlled, with well-defined optical properties, and high-RI thin films which are highly desired for optical fiber sensors. It has been found that for LPGs working at a dispersion turning point of higher order cladding modes only tens of nanometers of TiO2 overlay thickness allow to obtain cladding mode transition effect, and thus significant improvement of RI sensitivity. When the TiO2 overlay thickness reaches 70 nm, it is possible to obtain RI sensitivity exceeding 6200 nm/RIU in RI range where label-free sensors operate. Moreover, LPGs with TiO2-enhanced RI sensitivity have shown improved sensitivity to bacteria endotoxin (E. coli B lipopolysaccharide) detection, when TiO2 surface is functionalized with endotoxin binding protein (adhesin) of T4 bacteriophage.
    Full-text · Article · Mar 2015 · Optics Express
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    ABSTRACT: Dielectric films, such as hafnium dioxide (HfO2), aluminum oxide (Al2O3), zirconium dioxide (ZrO2), titanium dioxide (TiO2), and their composite layers are deposited on polycrystalline and amorphous substrates by the atomic layer deposition (ALD) method. We demonstrate that the use of this technology guarantees an uniform and controlled surface coverage in the nanometer scale at low temperatures (in our case below 100 °C). Modification of the composition of oxide layers allows the deposition of materials with quite different absorption coefficients, refractive indexes and dielectric constants. In particular, we demonstrate structural, electrical and optical properties of dielectric layers and test metal-oxide-semiconductor structures with these oxide materials. Our good quality dielectric layers, obtained at low temperature ALD, are characterized by a high dielectric constant (above 10), very smooth surface, wide energy gap (above 3 eV), low leakage current (in the range of 10- 8 A/cm2 at 1 V), high dielectric strength (even 6 MV/cm) and high refractive indexes (above 1.5 in visible spectral range).
    No preview · Article · Jan 2015 · Thin Solid Films
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    ABSTRACT: This paper reports on results of modeling of current-voltage characteristics of the Ag/ZnO/TiAu planar Schottky diodes containing interfacial layer of hafnium dioxide (HfO2) with thickness ranging from 1.25 to 7.5 nm. It was found that forward characteristics can be described with thermionic emission theory. In this way, values of some relevant diodes' parameters were determined, including the ideality factor and the effective Schottky barrier height. We found a satisfactory agreement of experimental and theoretical results for most diodes, with exception of the one with a 7.5-nm thick layer. It was found that a 2.5-nm thick HfO2 spacer between ZnO and silver contact yields the highest effective Schottky barrier height (~0.7 eV) accompanied by a pronounced rectification ratio (reaching 7 × 102 at ±2.5 V) of the examined planar structure.
    No preview · Article · Dec 2014 · IEEE Transactions on Electron Devices
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    ABSTRACT: Further development and commercialization of the new generation of optoelectronic and photovoltaic is often limited by the necessity of fabrication of low-cost and efficient transparent conductive electrodes. The development so far is hindered by the conveniently used indium tin oxide (ITO), which suffers from high cost and not high enough availability to support mass production. The zinc oxide is emerging as a convenient replacement for ITO for solar cell and light-emitting diode applications. The optical functions of aluminum-doped zinc oxide thin films are determined using optical spectroscopy measurements from 300 to 1100 nm. The dopant range studied varies from intrinsic ZnO to 5% Al content. Below the direct band gap there is a residual enhancement of the optical absorption coefficient by Al dopants, which is not related to surface roughness. We determined the dielectric functions and absorption coefficient evolution as the dopant concentration increases, as well as the free-carrier concentration.
    Full-text · Conference Paper · Nov 2014
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    ABSTRACT: t. We achieved high conductivity of zinc oxide layers doped with aluminum atoms using atomic layer deposition (ALD) method. Their growth mode, electrical and optical properties have been investigated. We discuss how the growth temperature and doping affect resistivity and optical properties of the films. The obtained resistivities of ZnO:Al thin films ( 1.2x10-3 Ωcm) and high transparency make them suitable for the TCO applications in photovoltaics. Developing of effective methods of aluminum doping of ZnO layers in ALD process and optimization of these layers
    Full-text · Article · Oct 2014 · Przeglad Elektrotechniczny

Publication Stats

3k Citations
648.70 Total Impact Points

Institutions

  • 1975-2016
    • Polish Academy of Sciences
      • Institute of Physics
      Warszawa, Masovian Voivodeship, Poland
  • 2001-2015
    • Cardinal Stefan Wyszynski University in Warsaw
      • Department of Mathematics
      Warszawa, Masovian Voivodeship, Poland
  • 2014
    • West Pomeranian University of Technology, Szczecin
      • Institute of Chemical and Environmental Engineering
      Stettin, West Pomeranian Voivodeship, Poland
    • Warsaw University Of Life Sciences
      • Department of Physiological Sciences
      Warszawa, Masovian Voivodeship, Poland
  • 2000-2014
    • Institute of Physics of the Polish Academy of Sciences
      Warszawa, Masovian Voivodeship, Poland
  • 2011
    • Universitas Kristen Satya Wacana
      Salatiga, Central Java, Indonesia
  • 1999-2011
    • Macquarie University
      • Department of Physics and Astronomy
      Sydney, New South Wales, Australia
  • 1983-2000
    • University of Hull
      Kingston upon Hull, England, United Kingdom
  • 1995
    • Ioffe Physical Technical Institute
      Sankt-Peterburg, St.-Petersburg, Russia
  • 1991-1992
    • University of Amsterdam
      • Van der Waals-Zeeman Institute
      Amsterdamo, North Holland, Netherlands
  • 1985-1990
    • Linköping University
      • Department of Physics, Chemistry and Biology (IFM)
      Linköping, Östergötland, Sweden
  • 1984
    • University of Warsaw
      Warszawa, Masovian Voivodeship, Poland