Gábor Magda

Budapest University of Technology and Economics, Budapeŝto, Budapest, Hungary

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Publications (3)45.99 Total impact

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    ABSTRACT: 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 remains unclear under what conditions long-range magnetic order can emerge from such defect-bound magnetic moments. Here we propose that, in contrast to random defect distributions, atomic-scale engineering of graphene edges with specific crystallographic orientation--comprising edge atoms from only one sub-lattice of the bipartite graphene lattice--can give rise to a robust magnetic order. We use a nanofabrication technique based on scanning tunnelling microscopy to define graphene nanoribbons with nanometre precision and well-defined crystallographic edge orientations. Although so-called 'armchair' ribbons display quantum confinement gaps, ribbons with the 'zigzag' edge structure that are narrower than 7 nanometres exhibit an electronic bandgap of about 0.2-0.3 electronvolts, which can be identified as a signature of interaction-induced spin ordering along their edges. Moreover, upon increasing the ribbon width, a semiconductor-to-metal transition is revealed, indicating the switching of the magnetic coupling between opposite ribbon edges from the antiferromagnetic to the ferromagnetic configuration. We found that the magnetic order on graphene edges of controlled zigzag orientation can be stable even at room temperature, raising hopes of graphene-based spintronic devices operating under ambient conditions.
    Nature 10/2014; 514(7524):608-611. · 38.60 Impact Factor
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    ABSTRACT: Graphene has gripped the scientific community ever since its discovery in 2004, with very promising electronic properties and hopes to integrate graphene into nanoelectronic devices. For graphene to make its way into electronic devices, two major obstacles have to be overcome: reproducible preparation of large area graphene samples and patterning techniques to obtain functional components. In this paper we present a graphene etching technique, which is crystallographic orientation selective and allows for the patterning of graphene layers using a chemical reduction process. The process involves the reduction of the SiO2 support by the carbon in the graphene itself. This reaction only occurs at the sample edges and does not result in the degradation of the graphene crystal lattice itself. However, we have observed evidence of strong hole doping in our etched samples.This etching technique opens up new possibilities in graphene patterning and modification. (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
    physica status solidi (c) 03/2010; 7(3‐4):1241 - 1245.
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    ABSTRACT: Graphene has many advantageous properties, but its lack of an electronic band gap makes this two-dimensional material impractical for many nanoelectronic applications, for example, field-effect transistors. This problem can be circumvented by opening up a confinement-induced gap, through the patterning of graphene into ribbons having widths of a few nanometres. The electronic properties of such ribbons depend on both their size and the crystallographic orientation of the ribbon edges. Therefore, etching processes that are able to differentiate between the zigzag and armchair type edge terminations of graphene are highly sought after. In this contribution we show that such an anisotropic, dry etching reaction is possible and we use it to obtain graphene ribbons with zigzag edges. We demonstrate that the starting positions for the carbon removal reaction can be tailored at will with precision. KeywordsGraphene-atomic force microscopy (AFM)-etching-nanoribbon-zigzag
    Nano Research 12/2009; 3(2):110-116. · 7.39 Impact Factor