Journal Article

FZJ-2024-03007

http://join2-wiki.gsi.de/foswiki/pub/Main/Artwork/join2_logo100x88.png Charge carrier density dependent Raman spectra of graphene encapsulated in hexagonal boron nitride

Sonntag, J.RWTH* ; Watanabe, K. ; Taniguchi, T. ; Beschoten, B.FZJ* ; Stampfer, C. (Corresponding author)FZJ*

2023
Inst. Woodbury, NY

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Please use a persistent id in citations: doi:10.1103/PhysRevB.107.075420  doi:10.34734/FZJ-2024-03007

Abstract: We present low-temperature Raman measurements on gate-tunable graphene encapsulated in hexagonal boron nitride, which allows us to study in detail the Raman G and 2D mode frequencies and linewidths as a function of the charge carrier density. We observe a clear softening of the Raman G mode (of up to 2.5 cm−1) at low carrier density due to the phonon anomaly and a residual G mode linewidth of ≈3.5cm−1 at high doping. By analyzing the G mode dependence on doping and laser power we extract an electron-phonon-coupling constant of ≈4.4×10−3 (for the G mode phonon). The ultraflat nature of encapsulated graphene results in a minimum Raman 2D peak linewidth of 14.5 cm−1 and allows us to observe intrinsic electron-electron scattering-induced broadening of the 2D peak of up to 18 cm−1 for an electron density of 5×1012cm−2 (laser excitation energy of 2.33 eV). Our findings not only provide insights into electron-phonon coupling and the role of electron-electron scattering in the broadening of the 2D peak but also crucially show the limitations when it comes to the use of Raman spectroscopy (i.e., the use of the frequencies and the linewidths of the G and 2D modes) to benchmark graphene in terms of charge carrier density, strain, and strain inhomogeneities. This is particularly relevant when utilizing spatially resolved 2D Raman linewidth maps to assess substrate-induced nanometer-scale strain variations.

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Contributing Institute(s):

1. Halbleiter-Nanoelektronik (PGI-9)
2. JARA Institut Quanteninformation (PGI-11)

Research Program(s):

1. 5221 - Advanced Solid-State Qubits and Qubit Systems (POF4-522) (POF4-522)
2. 5222 - Exploratory Qubits (POF4-522) (POF4-522)
3. GrapheneCore3 - Graphene Flagship Core Project 3 (881603) (881603)
4. 2D4QT - 2D Materials for Quantum Technology (820254) (820254)
5. DFG project 437214324 - Durchstimmbare Twistronics: Lokales Tuning und lokale Detektion topologischer Randzustände und Supraleitung in Zweilagigen-Graphen (437214324) (437214324)
6. DFG project 436607160 - NEMS Sensoren aus 2D-Material-Heterostrukturen (436607160) (436607160)
7. DFG project 390534769 - EXC 2004: Materie und Licht für Quanteninformation (ML4Q) (390534769) (390534769)

Appears in the scientific report 2024

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Database coverage:
; ; ; Clarivate Analytics Master Journal List ; Current Contents - Electronics and Telecommunications Collection ; Current Contents - Physical, Chemical and Earth Sciences ; Ebsco Academic Search ; Essential Science Indicators ; IF < 5 ; JCR ; SCOPUS ; Science Citation Index Expanded ; Web of Science Core Collection

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