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Anorganische Schichten: Graphenartiges MoS2 und WS2 wurde durch drei verschiedene chemische Methoden hergestellt. Mikroskopische Untersuchungen offenbarten, dass die Strukturen aus einer oder wenigen Schichten aufgebaut sind (siehe TEM‐Aufnahme von WS2‐Schichten), und ein atomar aufgelöstes TEM‐Bild zeigt, dass schichtförmiges MoS2 eine hexagonale Anordnung von Mo‐ und S‐Atomen aufweist (siehe Einschub).

We perform first-principles calculations based on density functional theory to study quasi onedimensional edge-passivated (with hydrogen) zigzag graphene nanoribbons (ZGNRs) of various widths with chemical dopants, boron and nitrogen, keeping the whole system isoelectronic. Gradual increase in doping concentration takes the system finally to zigzag boron nitride nanoribbons (ZBNNRs). Our study reveals that, for all doping concentrations the systems stabilize in antiferromagnetic ground states. Doping concentrations and dopant positions regulate the electronic structure of the nanoribbons, exhibiting both semiconducting and half-metallic behaviors as a response to the external electric field. Interestingly, our results show that ZBNNRs with terminating polyacene unit exhibit half-metallicity irrespective of the ribbon width as well as applied electric field, opening a huge possibility in spintronics device applications.Nanomaterials of carbon, like nanotubes, fullerenes, etc., have been of great interest in condensed-matter and material science because of their novel low-dimensional properties [1,2]. Over past few decades, cutting edge research has been carried out for advanced device integration, exploring the electronic and mechanical properties of these systems. The recent addition in this journey is graphene: a strictly two-dimensional flat monolayer of carbon atoms tightly packed into a honeycomb lattice [3,4]. Since its innovation [5,6,7], it has made possible the understanding of various properties in two dimensions, by simple experiments and has opened up huge possibilities for electronic device fabrications [8,9,10]. A large number of theoretical and experimental groups all over the world have gathered on this two dimensional platform to search for the "plenty of room" at this reduced dimension [11].Electronic properties of low dimensional materials are mainly governed by their size and geometry. Recent experimental sophistications permit the preparation of finite size quasi one dimensional graphene, named as graphene nanoribbons (GNRs) of varying widths, either by cutting mechanically exfoliated graphenes and patterning by lithographic techniques [12,13] or by tuning the epitaxial growth of graphenes [14,15]. Different geometrical terminations of the graphene monolayer give rise to two different edge geometries of largely varying electronic properties, namely, zigzag and armchair graphene. Several theoretical models, e.g., tight-binding model within Schrodinger [16,17,18], Dirac formalism for mass less fermions [19,20,21], density functional theory (DFT) etc. have been applied to explore the electronic and band structure properties of GNRs. There exists a few many-body studies, exploring the electronic and magnetic properties of these systems [22,23].DFT studies suggest that, the anti-ferromagnetic quasi one-dimensional (1D) zigzag edge graphene nanoribbons (ZGNRs) show half-metallicity at a finite external elec- tric field across the ribbon width within both local density approximation (LDA) [24] and g...

We have studied the modification in the electronic structure, as well as optical and transport properties of graphene induced by molecular charge transfer using ab initio density functional theory. Our results from first-principles spin-polarized calculations are compared with those of the available data from Raman spectroscopic studies of modified graphene systems. We find that electron donor and acceptor molecules adsorbed onto the graphene surface exhibit effective molecular charge transfer, giving rise to mid-gap molecular levels with tuning of the band gap region near the Dirac point. The molecular charge transfer causes the stiffening or softening of the Raman G-band frequency in graphene, and we find that it also has a significant impact on the intensity ratio of the D- to G-band, corroborating experimental findings. We suggest that these charge transfer mechanisms can be probed through the low-frequency profile of the optical conductivity.

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