Fine tuning of optical transition energy of twisted bilayer graphene via interlayer distance modulation

Corro, Elena del; Peña-Álvarez, Miriam; Sato, Kentaro; Morales‐García, Ángel; Bouša, Milan; Mračko, M.; Kolman, Radek; Pacáková, Barbara; Kavan, Ladislav; Kalbáč, Martin; Frank, Otakar

doi:10.1103/physrevb.95.085138

Cited by 14 publications

(13 citation statements)

References 33 publications

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“…The worse PV characteristics can stem either from a larger separation between the bilayer and the Si substrate or between the graphene layers themselves. It has been shown previously that the twist angle between the layers can influence photocurrent generation, and that the interaction between the two layers is strongly influenced by their distance . We note that in contrast to the previous case of monolayer graphene measured point by point with I–V sweeps at setpoints probably high enough to compress the bubble, the photocurrent maps were obtained in contact mode at smaller setpoints in order to avoid damaging the sample as much as possible.…”

Section: Resultsmentioning

confidence: 99%

Local Photovoltaic Properties of Graphene–Silicon Heterojunctions

Rahova

Sampathkumar

Vetushka

et al. 2018

Physica Status Solidi (b)

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Interfacing of materials with different dimensionalities becomes increasingly relevant for many applications which can utilize the exceptional properties of low‐dimensional materials on one hand, and build‐up on the existing production know‐how for bulk (3D) materials on the other. Numerous appealing possibilities are offered by such combinations. In this work, the authors focus on 2D–3D heterostructures composed of mechanically exfoliated single‐ and few‐layer layer graphene (Gr) coupled to freshly etched n‐doped silicon. Two ways of characterizing the photovoltaic (PV) properties of such junctions by Conductive Atomic Force Miscroscopy (C‐AFM) under illumination are shown: 1) by measuring the I–V curves directly at selected points, while the flakes are scanned in intermittent mode and 2) by scanning the samples in contact mode at different bias voltages, followed by reconstruction of I–V curves using mean photocurrent quantified in selected areas. The direct I–V curves measurement has been employed to discriminate the effect of increased p‐doping of the graphene layer, and the contact mode has been utilized to evaluate the separation between the graphene flake and the substrate. Additionally, pros and cons of the two routes are briefly discussed and outlook for further advanced nanoscale characterization of such junctions is proposed.

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Section: Resultsmentioning

confidence: 99%

Local Photovoltaic Properties of Graphene–Silicon Heterojunctions

Rahova

Sampathkumar

Vetushka

et al. 2018

Physica Status Solidi (b)

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“…Beside the mechanical properties of graphene, other aspects have been explored in high pressure experiments from which we can mention the evolution of the van Hove singularities, or the coupling evolution between graphene layers …”

Section: Graphene Under Extreme Conditions – a Surveymentioning

confidence: 99%

Raman scattering studies of graphene under high pressure

Machon

Bousige

Alencar

et al. 2017

J Raman Spectroscopy

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The effect of pressure -by definition a 3-dimensional concept -on 2-dimensional systems brings a number of fundamental questions, which have been partly answered through newly engineered samples and experimental setups. In this review of the high-pressure Raman studies of graphene, we will in particular underline the importance of the presence of a supporting substrate and its role for the production of biaxial strain conditions in high pressure experiments. Raman shifts observed during these experiments may be related to the strain induced by the substrate rather than by the applied pressure, graphene stress, and hydrostatic pressure not being straightforwardly equivalent in this case of a composite 2D-on-3D material. We will also consider the effects of the nature of the substrate surface, the nature of the pressure transmitting media, as well as the effect of the number of layers on the high-pressure response of the 2D-system, by using the phonon behavior as strain probe as pressure is applied. The effects of adhesion and of strain transfer from the substrate to the 2D-system will be at the heart of our discussion.

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“…The compressive stress, caused by the change of temperature and the negative thermal expansion coefficient of graphene, results in a progressive closing of the wrinkle walls and thus decrease of the interlayer distance 17 . The possibility of fine tuning the level of interaction between two misoriented layers by changing d has been shown recently 41 . Finally, the natural superlattices of the wrinkled graphene are promising candidates for facile experimental realisation of high-purity magic angle bilayers, which exhibit tuneable collective states at low temperatures.…”

Section: Resultsmentioning

confidence: 99%

Superlattice in collapsed graphene wrinkles

Verhagen

Pacáková

Bouša

et al. 2019

Sci Rep

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Topographic corrugations, such as wrinkles, are known to introduce diverse physical phenomena that can significantly modify the electrical, optical and chemical properties of two-dimensional materials. This range of assets can be expanded even further when the crystal lattices of the walls of the wrinkle are aligned and form a superlattice, thereby creating a high aspect ratio analogue of a twisted bilayer or multilayer – the so-called twisted wrinkle. Here we present an experimental proof that such twisted wrinkles exist in graphene monolayers on the scale of several micrometres. Combining atomic force microscopy and Raman spectral mapping using a wide range of visible excitation energies, we show that the wrinkles are extremely narrow and their Raman spectra exhibit all the characteristic features of twisted bilayer or multilayer graphene. In light of a recent breakthrough – the superconductivity of a magic-angle graphene bilayer, the collapsed wrinkles represent naturally occurring systems with tuneable collective regimes.

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Fine tuning of optical transition energy of twisted bilayer graphene via interlayer distance modulation

Cited by 14 publications

References 33 publications

Local Photovoltaic Properties of Graphene–Silicon Heterojunctions

Local Photovoltaic Properties of Graphene–Silicon Heterojunctions

Raman scattering studies of graphene under high pressure

Superlattice in collapsed graphene wrinkles

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