Search Results

You are looking at 1 - 5 of 5 items for

  • Author: Mário Kotlár x
Clear All Modify Search
Open access

Jozef Liday, Peter Vogrinčič, Viliam Vretenár, Mário Kotlár, Marián Marton and Vlastimil Řeháček

Abstract

Due to their properties, carbon nanotubes and reduced graphene oxide are highly promising materials for obtaining low-resistance ohmic contacts to p-GaN with good optical transparency for visible light. In this contribution we designed a combination of these two materials, along with a cap layer, to be used as structures for ohmic contacts to p-GaN. Carbon nanotube (CNT) and graphene oxide (GO) layers were deposited by spray coating using an off-the-shelf airbrush on p-GaN layers. The metallic layers of Au/Pd were vapour deposited. The structures for ohmic contacts were prepared in two configurations, namely as Au/Pd/r-GO/CNT/p-GaN and Au/Pd/CNT/r-GO/CNT/p-GaN. The prepared structures provide a low resistivity ohmic contact after subsequent annealing in air ambient at 600 °C for 3 minutes. The contact containing the sandwich CNT/r-GO/CNT interstructure exhibits lower values of contact resistance in comparison with the r-GO/CNT interstructure.

Open access

Vlastimil Řeháček, Ivan Hotový, Marian Vojs, Mário Kotlár, Thomas Kups and Lothar Spiess

Pyrolyzed Photoresist Film Electrodes for Application in Electroanalysis

Pyrolyzed photoresist film (PPF) electrodes for application in electroanalysis were prepared on alumina substrates. These electrodes were characterized for their electrical, microstructural (by Raman spectroscopy) and electrochemical properties. As a support, the PPF electrodes were tested for simultaneous determination of Pb(II), Cd(II) and Zn(II) in an aqueous solution on in-situ formed bismuth film by square wave voltammetry (SWV). The dependence of the stripping responses on the concentration of target metals was linear in the range from 1 × 10-8 to 9 × 10-8 mol/L. The effect of activation of the PPF surface by argon plasma on analytical performance of bismuth film electrode (BiFE) on PPF support was also investigated.

Open access

Jozef Liday, Peter Vogrinčič, Viliam Vretenár, Mário Kotlár, Marián Marton and Vlastimil Reháček

Abstract

We have designed and verified a new structure for ohmic contacts to p-GaN, mainly for applications in light emitting devices based on a layer of single-walled carbon nanotubes (SWCNT) and metallic layers of Cr and Au, namely in configuration Au/Cr/SWCNT/p-GaN. The layer of carbon nanotubes was deposited on p-GaN by spraying a solution of synthesized SWCNTs, while the layers of Cr and Au were vapour deposited. The effects of the annealing temperature and time upon the electrical properties of Au/Cr/SWCNT/p-GaN contacts have been studied. It has been found that the contact structure provides a low resistivity ohmic contact after subsequent annealing in N2 ambient at 700 °C for 1 minute.

Open access

Liday Jozef, Vogrinčič Peter, Vretenár Viliam, Kotlár Mário, Marton Marián, Mikolášek Miroslav and Řeháček Vlastimil

Abstract

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.

Open access

Jozef Liday, Peter Vogrinčič, Viliam Vretenár, Ivan Hotový, Mário Kotlár, Marián Marton and Vlastimil Řeháček

Abstract

We have examined electrical properties and concentration depth profiles of contact structures Au/Ni-Mg-(O)/SWCNT/p- GaN and Au/Ni-Mg-O/p-GaN, thus with and without an interlaying layer of single-walled carbon nanotubes (SWCNT). The metallization layers were deposited on p-GaN by DC reactive magnetron sputtering in an atmosphere with and without a low concentration of oxygen (cca 0.2 at%). The contacts were annealed in N2 . We have found that the structure containing the SWCNT interlayer exhibits lower values of contact resistivity in comparison with an otherwise identical contact without the SWCNT interlayer