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Bratislava, Slovakia

Liday J.,Slovak University of Technology in Bratislava | Vogrincic P.,Slovak University of Technology in Bratislava | Vretenar V.,Danubia NanoTech | Kotlar M.,Slovak University of Technology in Bratislava | And 3 more authors.
Journal of Electrical Engineering | Year: 2014

We have designed and verified a new structure for ohmic contacts to p-GaN based on a layer of carbon nanotubes (CNT), reduced graphene oxide (r-GO) and metallic layers of Cr, Pd and Au, namely in configurations Au/Cr/r-GO/CNT/p-GaN and Au/Pd/r-GO/CNT/p-GaN. The effects have been studied of the annealing temperature and the gas ambient upon the electrical properties of the contacts. Annealing of the Au/Pd/r-GO/CNT/p-GaN structure in air at 500 ◦C for 1 minute resulted in linear I − V curves measured between planar electrodes on the p-GaN. Hence, addition of r-GO to the CNT interlayer between p-GaN and the metallization layer is a highly promising procedure for further improvements of the ohmic contacts to p-GaN. © 2014 FEI STU. Source

Varga M.,Slovak University of Technology in Bratislava | Varga M.,ASCR Institute of Physics Prague | Kotlar M.,Slovak University of Technology in Bratislava | Vretenar V.,Danubia NanoTech | And 9 more authors.
Physica Status Solidi (B) Basic Research | Year: 2012

In this article, we investigate the nanocomposite material formation, particularly the deposition of nanocrystalline diamond and carbon nanowalls (CNWs) on single-wall carbon nanotubes buckypaper (BP). One part of the buckypaper substrate was nucleated by nanodiamond powder. The growth was carried out in a hot filament chemical vapor deposition (HFCVD) system. Contact angle measurements, scanning electron microscopy, and Raman spectroscopy were used for the surface morphology analysis and characterization of carbon phases. Due to a different surface pretreatment, different carbon nanostructures were formed: diamond film was grown on the nucleated BP area; non-treated area of the BP was covered with a dense field of CNWs. Covering a part of the BP surface prevented an access of the HF-plasma and so the growth of any carbon structures. © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Source

Pospisil J.,Brno University of Technology | Schmiedova V.,Brno University of Technology | Zmeskal O.,Danubia NanoTech | Vretenar V.,Danubia NanoTech | Kotrusz P.,Brno University of Technology
Key Engineering Materials | Year: 2016

The paper deals with the study of optical and electrical properties of inkjet-printed graphene oxide (GO) layers, which can be used e.g. for the preparation of various types of electronic devices. To ensure stable inkjet printing conditions of GO solution, mixture was thoroughly stirred for 1 h at room temperature or sonicated in the bath for 30 min. The thicknesses of prepared layers were determined by spectroscopic ellipsometry and profilometry. An electrical conductivity of GO was increased by the multistep reduction (due to annealing) - the conductivity was changed by these processes about seven orders of magnitude (GO is an isolator and reduced GO is a conductor). For electrical and dielectric measurements, samples with GO and mixture of GO with PEDOT were prepared. All current-voltage characteristics have a diode character. From AC measurements the bulk electrical conductivity and geometric capacity of prepared layers were determined. © 2016 Trans Tech Publications, Switzerland. Source

Mesko M.,Danubia NanoTech | Vretenar V.,Danubia NanoTech | Vretenar V.,Slovak Academy of Sciences | Kotrusz P.,Danubia NanoTech | And 4 more authors.
Physica Status Solidi (B) Basic Research | Year: 2012

Carbon nanowalls (CNWs) were grown by atmospheric dc plasma enhanced chemical vapour deposition method. Maintaining plasma at atmospheric pressure give us possibility to synthetize CNWs at high rate. By using two different liquid carbon sources we can control CNWs density. Growth of sparsely distributed CNWs can be achieved by using ethanol, while hexane gives densely packed CNWs films. © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Source

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