TY - CHAP AU - Tóth, Sára AU - Füle, Miklós Jenő AU - Veres, Miklós AU - Pócsik, István AU - Koós, Margit ED - Gyulai, József ED - Szabó, Péter János TI - Supercapacitor electrodes made from mixture of amorphous carbon nano-particles and carbon black T2 - Materials Science, Testing and Informatics III PB - Trans Tech Publications CY - Stafa SN - 9632192745 T3 - Materials Science Forum, ISSN 0255-5476 ; 537-538. PY - 2007 SP - 263 EP - 267 PG - 5 DO - 10.4028/www.scientific.net/MSF.537-538.263 UR - https://m2.mtmt.hu/api/publication/144948 ID - 144948 LA - English DB - MTMT ER - TY - JOUR AU - Tóth, Sára AU - Füle, Miklós Jenő AU - Veres, Miklós AU - Pócsik, István AU - Koós, Margit AU - Tóth, András AU - Ujvári, Tamás AU - Bertóti, Imre TI - Photoluminescence of ultra-high molecular weight polyethylene modified by fast atom bombardment JF - THIN SOLID FILMS J2 - THIN SOLID FILMS VL - 497 PY - 2006 IS - 1-2 SP - 279 EP - 283 PG - 5 SN - 0040-6090 DO - 10.1016/j.tsf.2005.10.050 UR - https://m2.mtmt.hu/api/publication/111941 ID - 111941 AB - An increase in the application potential of the ultra-high molecular weight polyethylene (UHMWPE) may be achieved by producing a hard, wear resistant carbonaceous modified surface layer on it. In this study the surface of UHMWPE samples was treated by 1 keV N, H and He fast atom bombardment (FAB) to obtain amorphous carbon surface layer which produces an enhancement of microhardness. The untreated and FAB-modified samples were investigated by photoluminescence, infrared, Raman and optical absorption spectroscopy. The FAB-treatment caused a nearly complete disappearance of the characteristic luminescence bands of UHMWPE (at 335, 351, 363 and 381 nm), the appearance of new bands at 459 and 495 nm due to the formation of new recombination levels in the FAB-treated samples. The remarkable decrease in integrated luminescence intensity indicates the appearance of new non-radiative recombination levels caused by FAB treatment. Structural modifications in FAB treated samples result in the development of structural arrangement containing sp2 bonded carbon sites in rings or chains of different sizes and the electronic levels corresponding to these structural elements are situated in the forbidden gap in the electronic density of states which brings forth the observed changes of the photoluminescence properties. © 2005 Elsevier B.V. All rights reserved. LA - English DB - MTMT ER - TY - JOUR AU - Tóth, Sára AU - Füle, Miklós Jenő AU - Veres, Miklós AU - Koós, Margit AU - Pócsik, István AU - Selman, JR AU - Arcon, D TI - Influence of amorphous carbon nano-clusters on the capacity of carbon black electrodes JF - THIN SOLID FILMS J2 - THIN SOLID FILMS VL - 482 PY - 2005 IS - 1-2 SP - 207 EP - 210 PG - 4 SN - 0040-6090 DO - 10.1016/j.tsf.2004.11.175 UR - https://m2.mtmt.hu/api/publication/144406 ID - 144406 AB - Electric double layer supercapacitor electrodes were prepared from a mixture of carbon black, amorphous carbon nano-particles and binder to obtain higher capacitance. The capacitance of the electrodes was calculated from the charge-discharge characteristics. Aluminium foil served as the current collector. The active material was laid on it by the spraying technique. The best adherence of the compound to the foil was achieved by the solution of hexamethylenediamine (HMDA), glycidyl methacrylate (GMA) and polytetrafluoroethylene (PTFE) in isopropanol. However, this binding mixture caused a loss in the capacitance because after the polymerization, it obstructs the pores of the carbon black, thus decreasing the active surface of the capacitor. To compensate this, plasma-prepared carbon nano-clusters were introduced into the capacitor electrode matrix, because this material has a large polarizability. The effect of the amorphous carbon nano-particle content of the prepared electrodes on the capacitance was studied. The maximal capacitance was obtained when the active material contained 30 wt.% of carbon nano-particles. © 2004 Elsevier B.V. All rights reserved. LA - English DB - MTMT ER - TY - JOUR AU - Füle, Miklós Jenő AU - Tóth, Sára AU - Veres, Miklós AU - Pócsik, István AU - Koós, Margit TI - Two bands structure of the photoluminescence excitation spectrum of the composite bands in a-C:H luminescence JF - DIAMOND AND RELATED MATERIALS J2 - DIAM RELAT MATER VL - 14 PY - 2005 IS - 3-7 SP - 1041 EP - 1046 PG - 6 SN - 0925-9635 DO - 10.1016/j.diamond.2005.01.042 UR - https://m2.mtmt.hu/api/publication/144404 ID - 144404 AB - A well defined structure in the photoluminescence excitation (PLE) spectrum of several hydrogenated amorphous carbon (a-C:H) films have been observed. An intense band appears in the PLE spectrum at excitation photon energies below optical gap and the other band of a much weaker intensity compared to the low energy peak can be observed for excitations in the vicinity of band-to-band optical transitions. The low energy band of the PLE spectrum exhibits resonance features and its peak position is in a close relation with the energy of the photoluminescence (PL) band maximum; that is when the PLE maximum corresponding to the blue PL band is shifted to higher photon energy relatively to that of the green PL band. In contrast to this behavior the high energy band maximum of PLE appears, practically at the same photon energy for both the green and the blue bands measured in the same a-C:H sample. In the framework of the luminescence mechanism for a-C:H the observed characteristic features of PLE spectra is explained by optical excitation inside the luminescence centers, at which spatial confinement of the electron hole pairs takes place and by optical transitions in the neighborhood of the luminescence centers to a some extended states as well. © 2005 Elsevier B.V. All rights reserved. LA - English DB - MTMT ER - TY - JOUR AU - Veres, Miklós AU - Füle, Miklós Jenő AU - Tóth, Sára AU - Koós, Margit AU - Pócsik, István AU - Kokavecz, János AU - Tóth, Zsolt AU - Radnóczi, György TI - Simultaneous preparation of amorphous solid carbon films, and their cluster building blocks JF - JOURNAL OF NON-CRYSTALLINE SOLIDS J2 - J NON-CRYST SOLIDS VL - 351 PY - 2005 IS - 12-13 SP - 981 EP - 986 PG - 6 SN - 0022-3093 DO - 10.1016/j.jnoncrysol.2004.12.009 UR - https://m2.mtmt.hu/api/publication/140309 ID - 140309 AB - The chemical vapor deposition (CVD) has 'dusty plasma' condition region, under which circumstances there is a strong tendency for formation of nano-particles in the plasma by aggregation of ions. Using this phenomena carbon nano-particles have been prepared simultaneously with solid hydrogenated amorphous carbon (a-C:H) films. Transmission electron microscopy (TEM) and atomic force microscopy (AFM) were used to study the morphology of nano-particles and the film surfaces as well. Size distributions and shape factors of nano-clusters have been obtained from TEM results; their change with applied self-bias voltage was also examined. The bonding properties of deposited layers and nano-clusters were investigated by infrared spectroscopy. A comparative analysis concerning the morphology of the films and the nano-clusters was performed. © 2005 Elsevier B.V. All rights reserved. LA - English DB - MTMT ER - TY - JOUR AU - Veres, Miklós AU - Koós, Margit AU - Tóth, Sára AU - Füle, Miklós Jenő AU - Pócsik, István AU - Tóth, András AU - Mohai, Miklós AU - Bertóti, Imre TI - Characterisation of a-C:H and oxygen-containing Si:C:H films by Raman spectroscopy and XPS JF - DIAMOND AND RELATED MATERIALS J2 - DIAM RELAT MATER VL - 14 PY - 2005 IS - 3-7 SP - 1051 EP - 1056 PG - 6 SN - 0925-9635 DO - 10.1016/j.diamond.2005.01.020 UR - https://m2.mtmt.hu/api/publication/111855 ID - 111855 AB - Diamond-like (DLC), silicon- (DLC-Si) and oxygen-containing (DLC-Si-O) a-C:H films were deposited at ambient temperatures onto Si wafers by radio frequency plasma CVD from methane, tetramethylsilane, and hexamethyldisiloxane precursors. The chemical composition and bonding between the constituents are investigated by Raman spectroscopy and X-ray photoelectron spectroscopy. Influence of silicon and oxygen content on the structure of amorphous diamond-like carbon films are discussed. © 2005 Elsevier B.V. All rights reserved. LA - English DB - MTMT ER - TY - JOUR AU - Veres, Miklós AU - Füle, Miklós Jenő AU - Tóth, Sára AU - Pócsik, István AU - Koós, Margit AU - Tóth, András AU - Mohai, Miklós AU - Bertóti, Imre TI - Raman scattering of ultra-high molecular weight polyethylene treated by plasma-based ion implantation JF - THIN SOLID FILMS J2 - THIN SOLID FILMS VL - 482 PY - 2005 IS - 1-2 SP - 211 EP - 215 PG - 5 SN - 0040-6090 DO - 10.1016/j.tsf.2004.11.176 UR - https://m2.mtmt.hu/api/publication/111854 ID - 111854 AB - Plasma-based ion implantation was used to modify the surface of ultra-high molecular weight polyethylene. High-purity N2, He and H2 gases were ionized in radio frequency (rf) discharge and implanted at acceleration voltages of 20-30 kV with dose of 2×1017 ion/cm2. The first-order Raman spectra with probe wavelengths of 785 nm and 488 nm as well as infrared reflection spectra were recorded. It was established that considerable dehydrogenization took place at these treatments and incorporation of oxygen was also detected. Amorphous carbon layer was formed after H+ and N+ treatments. The He+ implantation caused formation of a region with highly graphitic character. © 2004 Elsevier B.V. All rights reserved. LA - English DB - MTMT ER - TY - JOUR AU - Ivan, I AU - Veres, Miklós AU - Pócsik, István AU - Kökényesi, Sándor Jenő TI - Structural and optical changes in As2S3 thin films induced by light ion irradiation JF - PHYSICA STATUS SOLIDI A-APPLIED RESEARCH J2 - PHYS STATUS SOLIDI A APPL RES VL - 201 PY - 2004 IS - 14 SP - 3193 EP - 3199 PG - 7 SN - 0031-8965 DO - 10.1002/pssa.200406890 UR - https://m2.mtmt.hu/api/publication/1210968 ID - 1210968 AB - The influence of H+ and D+ ion irradiation and laser illumination on the optical absorption edge, the refractive index and the Raman scattering spectra of as-deposited and annealed As2S3 films have been investigated. It was established, that a significant similarity exists between optical changes induced in As2S3 films by light illumination and by irradiation with light ions and also between structural changes thought to be responsible for these effects. The changes are connected with electron excitation processes in both cases and further initiation of atomic rearrangements within the amorphous phase. © 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. LA - English DB - MTMT ER - TY - JOUR AU - Veres, Miklós AU - Füle, Miklós Jenő AU - Tóth, Sára AU - Koós, Margit AU - Pócsik, István TI - Surface enhanced Raman scattering (SERS) investigation of amorphous carbon JF - DIAMOND AND RELATED MATERIALS J2 - DIAM RELAT MATER VL - 13 PY - 2004 IS - 4-8 SP - 1412 EP - 1415 PG - 4 SN - 0925-9635 DO - 10.1016/j.diamond.2004.01.041 UR - https://m2.mtmt.hu/api/publication/144111 ID - 144111 AB - Surface enhanced Raman scattering (SERS) was applied to study hydrogenated amorphous carbon (a-C:H) and amorphous carbon (a-C) samples. Carbon free silver colloid served as SERS active medium; it was dried on the sample surface. The Raman signal amplitude increase by order of magnitude was observed. Further enhancement was recorded on the Raman spectrum as a result of the blinking phenomenon, which took place applying certain measurements conditions. A number of reproducible peaks was observed in the D and G band region both for a-C:H and a-C. Coexistence of these peaks in one sample's spectrum indicates that the amorphous carbon D and G peaks consist of several components: they are inhomogeneously broadened. For a given amorphous carbon sample the shape of the conventional Raman spectrum is determined by vibrations of dominant structural units. SERS gives the possibility to identify these units; moreover, presence of other components, not so characteristic for the sample, also can be evaluated. © 2004 Elsevier B.V. All rights reserved. LA - English DB - MTMT ER - TY - JOUR AU - Pócsik, István AU - Veres, Miklós AU - Füle, Miklós Jenő AU - Tóth, Sára AU - Koós, Margit TI - Specific statistical features of surface enhanced Raman scattering (SERS) spectra of graphite JF - JOURNAL OF NON-CRYSTALLINE SOLIDS J2 - J NON-CRYST SOLIDS VL - 338-340 PY - 2004 IS - 15 June 2004 SP - 496 EP - 498 PG - 3 SN - 0022-3093 DO - 10.1016/j.jnoncrysol.2004.03.027 UR - https://m2.mtmt.hu/api/publication/144110 ID - 144110 AB - A surface enhanced Raman scattering (SERS) study was carried out on highly oriented pyrolitic graphite (HOPG). In a typical SERS experiment the investigated material is in the liquid phase. For studying a solid sample, such as graphite, we put colloidal silver droplets on its surface, and let them dry. The dried colloid drops provide a strongly inhomogeneous lateral distribution of silver clusters. The pattern can be described as domains with different enhancement levels and hot spots. The increased SERS intensity was accompanied by increased spectral resolution, but with some unusual fluctuations. The SERS process on graphite seems to be an unstable one. The fluctuations suggest that the graphite Raman spectrum is inhomogeneously broadened whereby some components are selected and enhanced more strongly than the rest of the spectrum. These enhanced spectral bands are selected by some specific interaction between one of the metal clusters and the carbon surface structure. It is hard to determine at present whether these spectral components are constant, attached to certain frequencies, corresponding to definite structural units; or are distributed continuously in frequency. The physical process behind the temporal fluctuations is probably the structural variability in the silver clusters under intense illumination. © 2004 Elsevier B.V. All rights reserved. LA - English DB - MTMT ER -