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Electronic states of disordered grain boundaries in graphene prepared by chemical vapor deposition
Nemes-Incze, P.,Vancso, P.,Osvath, Z.,Mark, G.I.,Jin, X.,Kim, Y.S.,Hwang, C.,Lambin, P.,Chapelier, C.,PeterBiro, L. Pergamon Press ; Elsevier Science Ltd 2013 Carbon Vol.64 No.-
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 in graphene grown by chemical vapor deposition. Such low energy states are not reproduced by theoretical models which treat the grain boundaries as periodic dislocation-cores composed of pentagonal-heptagonal carbon rings. Using ab initio calculations, we have extended this model to include disorder, by introducing vacancies into a grain boundary consisting of periodic dislocation-cores. Within the framework of this model we were able to reproduce the measured density of states features. We present evidence that grain boundaries in graphene grown on copper incorporate a significant amount of disorder in the form of two-coordinated carbon atoms.
Graphene nanopatterns with crystallographic orientation control for nanoelectronic applications
Biro, L.P.,Nemes-Incze, P.,Dobrik, G.,Hwang, C.,Tapaszto, L. Elsevier 2011 Diamond and related materials Vol.20 No.8
The possibility of parallel processing of several features was investigated experimentally for the two methods allowing the crystallographically controlled nanopatterning of graphene: scanning tunneling lithography (STL) and carbothermal etching (CTE). It was found that with multitip systems both methods are suitable for parallel processing. CTE has the advantages that only in the atomic force microscope (AFM) indentation phase is needed the multitip system and it can reveal the location of grain boundaries, so that the nanodevices can be placed in a way that they do not cross grain boundaries. STL is well suited for purposefully producing twisted graphene multilayers with precisely-know misorientations of the individual layers, as also evidenced by Moire-type patterns observed in the atomic resolution scanning tunneling microscopy (STM) images.
Inexpensive, upscalable nanotube growth methods
Z.E. Horvath,K. Kertesz,L. Petho,A.A. Koos,L. Tapaszto,Z. Vertesy,Z. Osvath,Al. Darabont,P. Nemes-Incze,Zs. Ssrkozi,L.P. Bir? 한국물리학회 2006 Current Applied Physics Vol.6 No.2
Despite of the very promising foreseen applications, the use of carbon nanotubes in wider range is still limited by the high pro-duction costs. In this paper, our latest results concerning two inexpensive methods of carbon nanotube growth with the promise ofindustrial upscaling are presented. In case of the DC ‘‘arc in water’’ method, the eect of the angle of the two electrodes on theproduct yield was investigated. The highest nanotube yield and lowest amount of impurities were found at 90. electrode angles.zene/ferrocene solution in case of the injection CVD or ‘‘spay pyrolysis’’ method. Toluene, xylene, cyclohexane, cyclohexanone,n-hexane,n-heptane,n-octane andn-pentane were used as carbon source and cobaltocene and nickelocene as catalyst source. All thesecompounds were found to be suitable for nanotube production. The highest yield and the best quality were obtained when a mixtureof ferrocenenickelocene was used as catalyst and xylene as carbon source