Raman Signature and Phonon Dispersion of Atomically Thin Boron Nitride

Abstract

Raman spectroscopy has become an essential technique to characterize and investigate graphene and many other two-dimensional materials. However, there still lacks consensus on the Raman signature and phonon dispersion of atomically thin boron nitride (BN), which has many unique properties distinct from graphene. Such a knowledge gap greatly affects the understanding of basic physical and chemical properties of atomically thin BN as well as the use of Raman spectroscopy to study these nanomaterials. Here, we use both experiment and simulation to reveal the intrinsic Raman signature of monolayer and few-layer BN. We find experimentally that atomically thin BN without interaction with substrate has a G band frequency similar to that of bulk hexagonal BN, but strain induced by substrate can cause pronounced Raman shifts. This is in excellent agreement with our first-principles density functional theory (DFT) calculations at two levels of theory, including van der Waals dispersion forces (opt-vdW) and a fractional of the exact exchange from Hartree-Fock (HF) theory through hybrid HSE06 functional. Both calculations demonstrate that the intrinsic E2g mode of BN does not depend sensibly on the number of layers. Our simulations also suggest the importance of the exact exchange mixing parameter in calculating the vibrational modes in BN, as it determines the fraction of HF exchange included in the DFT calculations.

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• Mechanical Properties of Atomically Thin Boron Nitride and the Role of Interlayer Interactions
• High thermal conductivity of high-quality monolayer boron nitride and its thermal expansion
• Raman Signature and Phonon Dispersion of Atomically Thin Boron Nitride
• Outstanding Thermal Conductivity of Single Atomic Layer Isotope-Modified Boron Nitride
• Isolating hydrogen in hexagonal boron nitride bubbles by a plasma treatment
• Nonlinear Tunable Vibrational Response in Hexagonal Boron Nitride
• Monolayer WS${}_2$ electro- and photo-luminescence enhancement by TFSI treatment
• Strain-driven chiral phonons in two-dimensional hexagonal materials
• Experimental demonstration of the suppression of optical phonon splitting in 2D materials by Raman spectroscopy
• Dielectric breakdown and sub-wavelength patterning of monolayer hexagonal boron nitride using femtosecond pulses
• Strain distribution and thermal strain relaxation in MOVPE grown hBN films on sapphire substrates
• Hunting micrometer-sized graphene flakes on gold substrate