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Your search keyword '"Kareekunnan, Afsal"' showing total 2 results
Start Over Author "Kareekunnan, Afsal" Topic raman spectroscopy
2 results on '"Kareekunnan, Afsal"'

1. Raman spectroscopy of doubly aligned bilayer graphene.

Author

Kareekunnan, Afsal, Akabori, Masashi, Watanabe, Kenji, Taniguchi, Takashi, and Mizuta, Hiroshi

Subjects
*RAMAN spectroscopy, *GRAPHENE, *BORON nitride, *PHONONS
Abstract

Graphene aligned with hexagonal boron nitride (hBN) undergoes significant structural reconstruction due to the formation of a moiré superlattice. Here, we look at the effect of such structural reconstruction on the Raman spectroscopy of bilayer graphene for both singly aligned and doubly aligned heterostructures. The G peak is found to be particularly sensitive to the hBN alignment as it broadens in doubly aligned bilayer graphene compared to that of singly aligned bilayer graphene. This broadening is attributed to the variation in the phonon frequency as a result of the lattice reconstruction of the bilayer graphene responding to the periodic potential exerted by hBNs on either side of the bilayer graphene. In addition, the position of the G-peak and 2D peak follows a slope of 2.2, which implies the formation of strain in the bilayer graphene, validating the argument of lattice reconstruction. [ABSTRACT FROM AUTHOR]

Published
2024
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2. Molecular doping of graphene across ultra-thin molybdenum disulphide spacers

Author

Manu Jaiswal, Punnakkaparambil R. Shaina, Lijin George, and Kareekunnan Afsal

Subjects
Materials science, Inorganic chemistry, 02 engineering and technology, 010402 general chemistry, 01 natural sciences, law.invention, Condensed Matter::Materials Science, symbols.namesake, law, Condensed Matter::Superconductivity, Physics::Atomic and Molecular Clusters, Physics::Chemical Physics, Dopant, Graphene, Fermi level, Doping, Heterojunction, 021001 nanoscience & nanotechnology, Condensed Matter Physics, 0104 chemical sciences, Electronic, Optical and Magnetic Materials, Chemical physics, symbols, 0210 nano-technology, Bilayer graphene, Raman spectroscopy, Graphene nanoribbons
Abstract

Molecular doping of graphene is intriguing since the electronic and vibrational properties of graphene are not only determined by the interfacial charge transfer process, but they can also be influenced by adsorbate–graphene hybridization, adsorbate–adsorbate interactions, as well as Fermi-level pinning of the molecule. In this work, we investigate the change in vibrational properties of graphene induced by an organic electron acceptor molecule in the presence of intervening spacers of ultra-thin molybdenum disulphide (MoS2) of variable thickness, down to a single layer. Mechanically exfoliated single-layer graphene and few-layer MoS2 crystals are combined to form heterostructures, which are then subjected to molecular doping by means of an organic hole-dopant, 7,7,8,8-tetracyanoquinodimethane (TCNQ). Variations in Raman G-peak parameters are discussed in terms of molecular doping of graphen e, when the dopant:graphene separation is controllably increased. We show that dopant-separation dependent Fermi level variations of graphene cannot be completely accounted within a simple charge transfer model. The additional mechanisms relevant to the complex nature of molecular doping are discussed.

Published
2016

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