Wojciech Stępniowski

Publications (14) View all

• Source

  Available from: Marta Ewa Michalska-Domańska

  Article: Plasmonic enhancement of blue emission from ZnO nanorods grown on the anodic aluminum oxide (AAO) template

  Małgorzata Norek, Grzegorz Łuka, Marek Godlewski, Tomasz Płociński, Marta Michalska-Domaska, Wojciech J. Stępniowski
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  ABSTRACT: Luminescent properties of ZnO nanorods covered with Ag nanoparticles are examined. Nanorods were synthesized on AAO templates using Atomic Layer Deposition (ALD) technique. Two types of the samples were prepared with different arrangement of ZnO nanorods and doping conditions. Nanorods of the second type were codoped with Al, to stimulate defect-related emissions. The ZnO material fills heterogeneously the interior of the AAO nanopores and has hexagonal, wurtzite structure. Both types of structures exhibit a broad defect-related emission at about 440 nm, most probably related to recombination at zinc interstitial (Zni) defects. This emission in samples with a random distribution of ZnO:Al nanorods and finer Ag nanoparticles is enhanced by factor of ∼2.5 upon Ag deposition. The so-obtained material is interesting from the point of view of its application in blue range emitting diodes.
  Applied Physics A. 04/2013; 111:265-271.
• Article: Quantitative arrangement analysis of anodic alumina formed by short anodizations in oxalic acid

  Wojciech J. Stępniowski, Agata Nowak-Stępniowska, Zbigniew Bojar
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  ABSTRACT: Fast Fourier transform (FFT) based quantitative arrangement analysis was performed for the model periodic structures. Number of pores, surface area and porosity of the structures influence the FFT-based regularity ratio. Elimination of these effects allowed one to obtain convenient tool for quantitative arrangement analysis of anodic aluminum oxide (AAO). Researched AAO nanostructures were formed in 0.3 M oxalic acid via two-step selforganized 15-minute long processes. Temperature of electrolyte was ranging from 35 to 50 °C and anodizing voltage was ranging from 20.0 to 60.0 V. The greatest values of regularity ratio were obtained for anodic alumina fabricated at 40.0 and 50.0 V. Defect analysis, performed with Delanuay maps, has shown that the lowest values of defects percentage were for alumina obtained at 40.0 and 50.0 V. This finding is in agreement with FFT-based regularity ratio. The lowest values of circularity, describing nanopores shape, were obtained for anodic aluminum oxide fabricated at 60.0 V. Multi way analysis of variance of the regularity ratio, defects percentage and circularity has shown that both: anodizing voltage and electrolyte's temperature influence the nanopores arrangement.
  Materials Characterization 01/2013; 78(78):79. · 1.57 Impact Factor
• Article: The effect of anodizing temperature on structural features and hexagonal arrangement of nanopores in alumina synthesized by two-step anodizing in oxalic acid

  Leszek Zaraska, Wojciech J. Stępniowski, Eryk Ciepiela, Grzegorz D. Sulka
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  ABSTRACT: Nanoporous anodic aluminum oxide (AAO) layers were synthesized by a two-step self-organized anodization in 0.3 M oxalic acid under various anodizing conditions. The influence of anodizing temperature on the structural features and pore arrangement of AAO was investigated. With increasing anodizing temperature, an increase of the pore diameter and porosity of AAO, as well as a decrease of the cell wall thickness and barrier layer thickness were observed. Notwithstanding, the interpore distance and pore density were found to be almost constant independently of the anodizing temperature. A degree of pore order was studied on the basis of the fast Fourier transform (FFT) images, Delaunay triangulations (defect maps), pair distribution functions (PDF) and the angular distribution functions (ADF). For anodizations carried out at 30 V, it was found that the better nanopore order in AAO is observed, the higher temperature is applied. It can be explain in terms of the faster reorganization of pores at the metal/oxide interface occurring during the oxide growth at elevated temperatures. On the other hand, no direct effects of the anodizing temperature on the regularity of nanoporous AAO were found for anodizations carried out at higher potentials. A significant increase of the pore circularity with increasing temperature was observed for all studied potentials. The highest values of the FFT-based, PDF and ADF-derived regularity ratios, as well as the lowest percentage of defects and the highest circularity of pores were obtained for samples anodized at 40 V independently of the anodizing temperature.
  Thin Solid Films 01/2013; 534:155. · 1.89 Impact Factor
• Source

  Available from: Wojciech Stępniowski

  Dataset: ApplSurfSci2012a

  Wojciech J. Stępniowski, Małgorzata Norek, Marta Michalska-Domańska, Aneta Bombalska, Agata Nowak-Stępniowska, Mirosław Kwaśny, Zbigniew Bojar
• Source

  Available from: Marta Ewa Michalska-Domańska

  Article: Nanoporous alumina formed by self-organized two-step anodization of Ni3Al intermetallic alloy in citric acid

  Wojciech J St, Grzegorz Cielak, Małgorzata Norek, Krzysztof Karczewski, Marta Michalska-Domá, Dariusz Nska, Wojciech Zasada, Paweł J Polkowski, Zbigniew Zwik, Bojar
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  ABSTRACT: Formation of the nanoporous alumina on the surface of Ni 3 Al intermetallic alloy has been studied in details and compared with anodization of aluminum. Successful self-organized anodization of this alloy was performed in 0.3 M citric acid at voltages ranging from 2.0 to 12.0 V using a typical two-electrode cell. Current density records revealed different mechanism of the porous oxide growth when compared to the mechanism pertinent for the anodization of aluminum. Electrochemical impedance spectroscopy experiments confirmed the differences in anodic oxide growth. Surface and cross-sections of the Ni 3 Al intermetallic alloy with anodic oxide were observed with field-emission scanning electron microscope and characterized with appropriate software. Nanoporous oxide growth rate was estimated from cross-sectional FE-SEM images. The lowest growth rate of 0.14 m/h was found for the anodization at 0 • C and 2.0 V. The highest one – 2.29 m/h – was noticed for 10.0 V and 30 • C. Pore diameter was ranging from 18.9 nm (2.0 V, 0 • C) to 32.0 nm (12.0 V, 0 • C). Interpore distance of the nanoporous alumina was ranging from 56.6 nm (2.0 V, 0 • C) to 177.9 nm (12.0 V, 30 • C). Pore density (number of pore occupying given area) was decreasing with anodizing voltage increase from 394.5 pores/m 2 (2.0 V, 0 • C) to 94.9 pores/m 2 (12.0 V, 0 • C). All the geometrical features of the anodic alumina formed by two-step self-organized anodization of Ni 3 Al intermetallic alloy are depending on the operating conditions.
  Applied Surface Science 01/2013; 264:605-610. · 2.10 Impact Factor