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Anharmonicity in Raman-active phonon modes in atomically thin MoS2

Sarkar, S and Maity, I and Pradeepa, HL and Nayak, G and Marty, L and Renard, J and Coraux, J and Bendiab, N and Bouchiat, V and Das, S and Majumdar, K and Jain, M and Bid, A (2020) Anharmonicity in Raman-active phonon modes in atomically thin MoS2. In: Physical Review B, 101 (20).

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Official URL: https://dx.doi.org/10.1103/PhysRevB.101.205302


Phonon-phonon anharmonic effects have a strong influence on the phonon spectrum; most prominent manifestation of these effects are the softening (shift in frequency) and broadening (change in FWHM) of the phonon modes at finite temperature. Using Raman spectroscopy, we studied the temperature dependence of the FWHM and Raman shift of E2g1 and A1g modes for single-layer and natural bilayer MoS2 over a broad range of temperatures (8<T<300K). Both the Raman shift and FWHM of these modes show linear temperature dependence for T>100K, whereas they become independent of temperature for T<100K. Using first-principles calculations, we show that three-phonon anharmonic effects intrinsic to the material can account for the observed temperature dependence of the linewidth of both the modes. It also plays an important role in determining the temperature dependence of the frequency of the Raman modes. The observed evolution of the linewidth of the A1g mode suggests that electron-phonon processes are additionally involved. From the analysis of the temperature-dependent Raman spectra of MoS2 on two different substrates-SiO2 and hexagonal boron nitride-we disentangle the contributions of external stress and internal impurities to these phonon-related processes. We find that the renormalization of the phonon mode frequencies on different substrates is governed by strain and intrinsic doping. Our work establishes the role of intrinsic phonon anharmonic effects in deciding the Raman shift in MoS2 irrespective of substrate and layer number. © 2020 American Physical Society.

Item Type: Journal Article
Publication: Physical Review B
Publisher: American Physical Society
Additional Information: Copy right for this article belongs to American Physical Society
Keywords: Calculations; III-V semiconductors; Layered semiconductors; Molybdenum compounds; Phonons; Silica; Substrates; Temperature distribution, Different substrates; Finite temperatures; First-principles calculation; Hexagonal boron nitride; Linear temperature dependence; Raman-active phonon; Temperature dependence; Temperature-dependent raman, Sulfur compounds
Department/Centre: Division of Electrical Sciences > Electrical Communication Engineering
Division of Physical & Mathematical Sciences > Physics
Date Deposited: 22 Dec 2020 08:29
Last Modified: 22 Dec 2020 08:29
URI: http://eprints.iisc.ac.in/id/eprint/65858

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