Zoltán Osváth

Zoltán Osváth
Centre for Energy Research · Institute of Technical Physics and Materials Science

PhD

About

83
Publications
10,840
Reads
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2,587
Citations
Introduction
Experienced Researcher skilled in Scanning Probe Microscopy of Graphene, Carbon Nanotubes, and Hybrid Nanostructures.
Additional affiliations
October 2016 - present
Hungarian Academy of Sciences, Centre for Energy Research
Position
  • Senior Researcher
January 2015 - September 2016
Hungarian Academy of Sciences, Centre for Energy Research
Position
  • Research Associate
September 2012 - December 2014
Hungarian Academy of Sciences, Research Centre for Natural Sciences (TTK)
Position
  • Research Associate

Publications

Publications (83)
Article
Full-text available
Graphene-covered silver nanoparticles were prepared directly on highly oriented pyrolytic graphite substrates and characterized by atomic force microscopy. UV–Vis reflectance spectroscopy was used to measure the shift in the local surface plasmon resonance (LSPR) upon exposure to acetone, ethanol, 2-propanol, toluene, and water vapor. The optical r...
Article
Full-text available
Graphene has numerous outstanding physical properties such as excellent electron mobility, extremely high thermal conductivity, high flexibility, remarkable mechanical strength, and high transparency [...]
Article
Here we report a new method combining strain and defect engineering for the periodic modulation of the graphene nanoscale rippling. First, gold nanoparticles of 16 nm in diameter were synthesized by seed-mediated, wet-chemical approach, and thiol-terminated polyethylene glycol (mPEG-SH) molecules were grafted onto their surface. High-density monola...
Article
Full-text available
Silver nanoparticles (Ag NPs) play important roles in the development of plasmonic applications. Combining these nanoparticles with graphene can yield hybrid materials with enhanced light–matter interaction. Here, we report a simple method for the synthesis of graphene–silver nanoparticle hybrids on highly oriented pyrolytic graphite (HOPG) substra...
Article
The direct experimental probing of locally varying lattice parameters and anisotropic lattice deformations in atomic multilayers is extremely challenging. Here, we develop a combined numerical and graphical method for the analysis of irregular moiré superstructures measured by scanning tunneling microscopy (STM) on a small-twist-angle (∼0.6∘) graph...
Preprint
Full-text available
The direct experimental probing of locally varying lattice parameters and anisotropic lattice deformations in atomic multilayers is extremely challenging. Here, we develop a new combined numerical/graphical method for the analysis of irregular moir\'e superstructures measured by scanning tunneling microscopy (STM) on a small-twist-angle ($\sim$0.6$...
Preprint
Full-text available
We investigated the vapour sensing properties of different graphene-gold hybrid nanostructures. We observed the shifts in the optical spectra near the local surface plasmon resonance of the gold nanoparticles by changing the concentration and nature of the analytes (ethanol, 2-propanol, and toluene). The smaller, dome-like gold nanoparticles proved...
Article
Full-text available
We investigated the vapour sensing properties of different graphene-gold hybrid nanostructures. We observed the shifts in the optical spectra near the local surface plasmon resonance of the gold nanoparticles by changing the concentration and nature of the analytes (ethanol, 2-propanol, and toluene). The smaller, dome-like gold nanoparticles proved...
Article
Substrate properties might significantly influence the scattering spectra of supported plasmonic nanoparticles due to different damping mechanisms. In this work ITO substrates are modified by the combination of nanosphere lithography and ion-bombardment to create a nanopattern with sharp boundaries between the irradiated and masked regions. The sin...
Article
Full-text available
Graphene on noble-metal nanostructures constitutes an attractive nanocomposite with possible applications in sensors or energy conversion. In this work we study the properties of hybrid graphene/gold nanoparticle structures by Raman spectroscopy and Scanning Probe Methods. The nanoparticles (NPs) were prepared by local annealing of gold thin films...
Article
It is shown that scanning-probe and optical measurements performed on individual gold particles provide direct experimental evidence on the inhomogeneous ligand distribution of tip-selectively cysteamine modified gold nanorods. At higher (10⁻² mM) cysteamine concentration, a well-defined patch is formed at the tips of 115 x 55 nm gold nanorods. Whi...
Article
Full-text available
The development of functional composite nanomaterials based on graphene and metal nanoparticles (NPs) is currently the subject of intense research interest. In this study we report the preparation of novel type of graphene/Sn and graphene/SnOx (1 < x < 2) hybrid nanostructures and their investigation by scanning probe methods. First, we prepare Sn...
Article
Full-text available
We investigate the local electronic structure of a Sinai-like, quadrilateral graphene quantum billiard with zigzag and armchair edges using scanning tunneling microscopy at room temperature. It is revealed that besides the $(\sqrt{3}\times\sqrt{3})R30${\deg} superstructure, which is caused by the intervalley scattering, its overtones also appear in...
Article
Hybrid materials composed of single walled carbon nanotubes (SWCNTs) as hollow containers and small molecules as fillers possess intriguing physical and chemical properties. Infrared spectroscopy is a useful method in most cases to characterize hybrid systems; however, regardless of the type of small molecule encapsulated in the SWCNT, the IR spect...
Article
Full-text available
Graphene grown by chemical vapour deposition is transferred on top of flat gold nanoislands and characterized by scanning tunnelling microscopy (STM) and atomic force microscopy (AFM). Graphene bubbles are formed with lateral dimensions determined by the size and shape of nanoislands. These graphene bubbles can be squeezed during STM imaging using...
Article
Full-text available
Using nanoparticles to impart extrinsic rippling in graphene is a relatively new method to induce strain and to tailor the properties of graphene. Here we study the structure and elastic properties of graphene grown by chemical vapour deposition and transferred onto a continuous layer of SiO2 nanoparticles with diameters of around 25 nm, prepared b...
Article
Full-text available
Graphene-metal nanoparticle hybrid materials potentially display not only the unique properties of metal nanoparticles and those of graphene, but also additional novel properties due to the interaction between graphene and nanoparticles. This study shows that gold nanoislands can be used to tailor the local electronic properties of graphene. Graphe...
Article
Heterostructures of 2D materials are expected to become building blocks of next generation nanoelectronic devices. Therefore, the detailed understanding of their interfaces is of particular importance. In order to gain information on the properties of the graphene - MoS2 system, we have investigated MoS2 sheets grown by chemical vapour deposition (...
Article
3C-SiC layers were deposited on Si substrates by using a low temperature buffer layer and the addition of methyl trichloro silane to the gas phase during the high temperature thick film growth. Several samples were grown by varying the deposition temperature and the methyl trichloro silane content in order to study how these parameters affect the l...
Article
Epitaxial iron silicide nanostructures are grown by solid phase epitaxy on Si(0 0 1) and Si(1 1 1), and by reactive deposition epitaxy on Si(0 0 1) substrates. The formation process is monitored by reflection high-energy electron diffraction. The morphology, size, and electrical properties of the nanoparticles are investigated by scanning electron...
Article
Full-text available
Mesoporous silica thin films were patterned at the sub-micron scale utilizing the ion hammering effect in order to combine the advantages of mesoporous character and surface morphology, while preserving the interconnected pore system or creating laterally separated porous volumes surrounded by nonpermeable compact zones. Porous silica coatings were...
Article
Full-text available
Thin (45–50 nm) non-doped and doped (by Sb and Al) polycrystalline Mg stannide films consisting mainly of Mg2Sn semiconductor phase and containing small quantity of Mg2Si phase have been grown by multiple layer deposition at room temperature and single step annealing at 150 °C of the (Sn–Mg) bi-layers on Si(111) n-type wafers with 7.5 Ωcenterdotcm...
Conference Paper
Full-text available
Optical and electrical properties of Mg stannide and germanide nanolayers grown by solid phase epitaxy on a Si(111)7×7 substrate have been studied. It was shown that all grown ultrathin (45-90 nm) films are semiconductors with small band gaps: 0.17-0.22 eV for Mg2Sn and Mg2SnxSi1-x, 0.70 eV for Mg2Ge and 0.56 eV for Mg2GexSi1-x. Optical functions,...
Article
Full-text available
Graphene covered metal nanoparticles constitute a novel type of hybrid materials, which provide a unique platform to study plasmonic effects, surface-enhanced Raman scattering (SERS), and metal-graphene interactions at the nanoscale. Such a hybrid material is fabricated by transferring graphene grown by chemical vapor deposition onto closely spaced...
Article
Full-text available
The possibility that non-magnetic materials such as carbon could exhibit a novel type of s-p electron magnetism has attracted much attention over the years, not least because such magnetic order is predicted to be stable at high temperatures. It has been demonstrated that atomic-scale structural defects of graphene can host unpaired spins, but it r...
Article
Full-text available
The electronic properties of graphene can be significantly influenced by mechanical strain. One practical approach to induce strain in graphene is to transfer atomically thin membranes onto pre-patterned substrates with specific corrugations. The possibility of using nanoparticles to impart extrinsic rippling to graphene has not been fully explored...
Article
The properties of graphene nanoribbons are dependent on both the nanoribbon width and the crystallographic orientation of the edges. Scanning tunneling microscope lithography is a method which is able to create graphene nanoribbons with well defined edge orientation, having a width of a few nanometers. However, it has only been demonstrated on the...
Article
Full-text available
Metal-graphene interfaces generated by electrode deposition induce barriers or potential modulations influencing the electronic transport properties of graphene based devices. However, their impact on the local mechanical properties of graphene is much less studied. Here we show that graphene near a metallic interface can exhibit a set of ripples s...
Article
Perturbations of the two dimensional carbon lattice of graphene, such as grain boundaries, have significant influence on the charge transport and mechanical properties of this material. Scanning tunneling microscopy measurements presented here show that localized states near the Dirac point dominate the local density of states of grain boundaries i...
Article
Full-text available
First experiments on swift ion irradiation of highly oriented pyrolythic graphite led to formation of carbon nanotubes (CNT) at the cascade eruption points. CNT length was in the micron range, which corresponded to an explosive crystallization of the carbon plume with about sound velocity. Multiplicity of CNT walls depended on cascade density: sing...
Article
We studied a possibility of reduction of the surface of graphite fluoride obtained by fluorination of highly oriented pyrolytic graphite (HOPG) by a gaseous mixture of BrF3 and Br2. X-ray diffraction (XRD) revealed a layered structure of the fluorinated product being a second-stage intercalate due to a presence of bromine molecules between the fluo...
Article
Kimutattuk, hogy a nem-hatszöges (n-H) gyűrűket is tartalmazó szén nanoszerkezetek (Y-elágazás, hengerspirálok, stb.) növekedését az n-H gyűrűk beépülésének mikéntje határozza meg, új modellt javasoltunk hengerspirálok szerkezetére. Elsőként készítettünk Si3N4/szén nanocső kompozitokat és megmutattuk, hogy megfelelő szinterelési paraméterek alkalma...
Article
In this work, carbon nanotube samples were produced by aerosol chemical vapour deposition from a solution of ferrocene in benzylamine. The multi-walled nanotubes produced by this method were investigated by TEM, SEM/EDS, scanning tunneling microscopy (STM) and tunneling spectroscopy (STS). The dl/dV curves obtained from the STS measurements showed...
Article
Multi-walled carbon nanotubes irradiated with Ar+ ions of low (5×1011 ions/cm2) and high (1015 ions/cm2) fluences were investigated by STM. Contrary to the case of low fluence irradiation, the defects produced during the high fluence irradiation could not be observed individually, and the surface of nanotubes became rough. Irradiated nanotubes coul...
Article
Amorphous carbon/nickel double layers were irradiated by 30 keV Ga+ ions via focused ion beam. The effect of irradiation on the concentration distribution of all constituents was studied by Auger electron spectroscopy depth profiling and cross sectional transmission electron microscopy, while the morphology change of the sample was determined by at...
Article
Atomic Force Microscopy (AFM) in the tapping (intermittent contact) mode is a commonly used tool to measure the thickness of graphene and few layer graphene (FLG) flakes on silicon oxide surfaces. It is a convenient tool to quickly determine the thickness of individual FLG films. However, reports from literature show a large variation of the measur...
Article
Fe/Ag thin films are intensively investigated due to their special magnetic properties. Recently a deposition-order dependent asymmetric interface has been found. When iron is grown on silver, the interface is sharp, while the growth of Ag on Fe results in a long, low-energy tail of the Ag peak in the Rutherford backscattering spectrometry (RBS) sp...
Article
Full-text available
Multiwalled carbon nanotubes have been prepared using catalytic decomposition of solutions of ferrocene in liquid hydrocarbons: n-hexane, benzene and xylenes. The solutions were injected into the reaction furnace using Ar as carrier gas. The experimental investigations were effectuated in a home-made experimental setup using the spray-pyrolysis met...
Article
Commercial few-layer graphite platelets were characterized by atomic force microscopy (AFM). Successive oxidation of the graphite platelets was carried out at 450-550 degrees C in air, and AFM measurements were performed after each oxidation step. The measurements showed that the applied thermal oxidation reduced the dimensions of the platelets. We...
Article
Atomic resolution scanning tunneling microscope (STM) images of native and artificially created defect sites on graphite and carbon nanotubes were compared. The presence of position-dependent coexisting superstructure patterns was identified on all of the investigated samples. The results indicate that superstructure patterns are mainly determined...
Article
Measuring with a spectroscopic ellipsometer we determined the complex dielectric function of completely amorphous silicon carbide prepared by ion implantation. 860 keV Ni+ ions were implanted into single crystalline 4H-SiC to produce thick amorphized layer. Ion beam analysis was applied to assess total amorphization. For this purpose 4He+ ion beam...
Article
Full-text available
We have measured how irradiation by Ar+ and N+ ions modifies electronic conduction in single-wall carbon nanotube (SWNT) networks, finding dramatically different effects for different thicknesses. For very thin transparent networks, ion irradiation increases localization of charge carriers and reduces the variable-range hopping conductivity, especi...
Article
Graphite platelets of 1-5 mu m in diameter consisting of a few graphenes were generated from commercially available exfoliated graphite by ultrasonic treatment in benzene (1 mg material in 20 ml solvent) for 3 h. Droplets from the suspension were dispersed on silicon wafer. The graphite platelets were characterized by atomic force microscopy (AFM)....
Article
Full-text available
Si amorphous 41 nm/Cr polycrystalline 46 nm multilayer structure was irradiated by 30 keV Ga + ions with fluences in the range of 25− 820 ions/ nm 2 using a focused ion beam. The effect of irradiation on the concentration distribution was studied by Auger electron spectroscopy depth profiling, cross-sectional transmission electron microscopy, and a...
Article
We study the effect of Ar+ irradiation on the intermediate frequency modes (IFM) in Raman spectra of single-wall carbon nanotubes. We observe new features in the intermediate frequency region from 386 to 635 cm–1 as the defect concentration increases, whereas at the same time there is a decrease of other IFM modes. After annealing in vacuum, the IF...
Article
In this work the STM investigation of nanotube point defects created by ion irradiation (e.g. vacancies) is presented. The defects appeared as hillock-like features on the STM images. These defects were compared with similar features observed on the STM images of as-grown coiled carbon nanotubes. In this case the observed hillock-like features were...
Article
Smooth (0001)AlN surface on a (0001) sapphire substrate was prepared by ammonia Molecular Beam Epitaxy. A continuous (2×2)(1×1) reconstruction phase transition on the (0001)AlN surface under ammonia flux was experimentally investigated by RHEED. The intensity of a fractional (0 1/2) streak was studied as a function of the sample temperature under d...
Article
Kinetics of (0001) Al2O3 surface nitridation and subsequent growth of AlN films on the sapphire substrate by ammonia molecular beam epitaxy (MBE) are investigated. Surface morphology evolution during AlN growth is studied in situ by reflection high energy electron diffraction and ex situ by atomic force microscopy. It is found that the surfaces of...
Article
Full-text available
The atomic resolution scanning tunneling microscopy investigation of a multiwall carbon nanotube bend junction is reported. Atomic resolution images taken at the junction region revealed position-dependent modulation of the electronic density of states, with a period larger than but commensurate to the underlying atomic lattice, attributed to the s...
Article
We study the effect of Ar + -irradiation on electrical transport in an individual single wall carbon nanotube (SWNT), a thin SWNT network and a thick SWNT film. The damage to SWNT structure induced by Ar + -irradiation is characterized by Raman spectroscopy. The electrical conductance both in an individual SWNT and in a thin SWNT network is strongl...
Article
The characteristics of carbon nanotube field effect transistor are investigated after the whole device is irradiated with Ar+ ions. The resistance become much higher due to the electron scattering at vacancies produced by Ar+ irradiation. In addition, the subthreshold slop, S, (dVG/d(log ID)) increases and the Schottky barrier height decreases afte...
Article
Single layers of Fe and Ag, as well as Fe/Ag (iron deposited first) and Ag/Fe bilayers were prepared by molecular beam evaporation onto Si. The samples were investigated with backscattering spectrometry (BS) and atomic force microscopy (AFM). BS spectra of Fe/Ag and Ag/Fe indicate a significant difference at the interface. In the case of Fe/Ag the...
Article
Multi-wall carbon nanotubes (MWCNTs) dispersed on graphite (HOPG) substrate were irradiated with Ar+ ions of 30 keV, using a dose of D=5×1011 ions/cm2. The irradiated nanotubes were investigated by scanning tunneling microscopy (STM) and spectroscopy (STS) under ambient conditions. Atomic resolution STM images revealed individual nanotube defects,...
Article
Despite of the very promising foreseen applications, the use of carbon nanotubes in wider range is still limited by the high production costs. In this paper, our latest results concerning two inexpensive methods of carbon nanotube growth with the promise of industrial upscaling are presented. In case of the DC “arc in water” method, the effect of t...
Article
The injection chemical vapor deposition (CVD) method allows the semi-continuous production of pure multi-wall carbon nanotubes (MWCNTs). In order to find the most efficient catalyst material and carbon source, we investigated the quality and quantity of carbon nanotubes, when different metallocenes (ferrocene, cobaltocene and nickelocene) and hydro...
Article
A systematic study on the controlled growth of large areas of aligned multi-wall carbon nanotube arrays, from ferrocene–benzene precursor, and of nanotube junctions from ferrocene–thiophene precursor, without hydrogen addition, using an injection CVD method easy to scale up for industrial production is reported.A detailed study is presented of how...
Article
Multi‐wall carbon nanotubes (MWCNTs) dispersed on graphite (HOPG) substrate were irradiated with Ar+ ions of 30 keV, using a low‐dose of D = 5×1011 ions/cm2. The irradiated samples were investigated by scanning tunneling microscopy (STM) under ambient conditions. Atomic resolution STM images reveal individual nanotube defects, which appear as hil...
Article
Multiwall carbon nanotubes (MWCNTs) dispersed on graphite on highly oriented pyrolytic graphite (HOPG) substrate were irradiated with Ar+ ions of 30 keV. The irradiated samples were investigated by scanning tunneling microscopy (STM) and spectroscopy (STS) in air. The irradiation-induced defects appear as hillocklike protrusions on the nanotube wal...
Article
Full-text available
The present work is devoted to the synthesis of carbon nanotubes by spray pyrolysis method. This procedure is a version of CCVD method (Catalysed Chemical Vapour Deposition). Using a quartz reactor we have studied the influence of the history of the reactor wall surface, the lenght of the reactor and different aliphatic, saturated hydrocarbons as c...
Article
An overview of the available data on carbon nanotube Y junctions is given. The structural models and the transport calculations on the Y junctions are reviewed followed by the various methods, which successfully produced these junctions and the available experimental transport and tunneling data of the grown junctions. In the discussion section, th...
Article
Multi-wall and single wall carbon nanotubes (MWCNTs, SWCNTs) dispersed on graphite (HOPG) and gold substrates were irradiated with two different doses of Ar+ ions. The irradiated samples were investigated by scanning tunneling microscopy (STM) and spectroscopy (STS). The investigation of SWCNTs irradiated with low-dose Ar+ ions revealed isolated de...