Observation of A Raman mode splitting in few layer black phosphorus encapsulated with hexagonal boron nitride

Area of Science:

• Materials Science
• Condensed Matter Physics
• Nanotechnology

Background:

• Black phosphorus is a promising 2D material with unique electronic and optical properties.
• Few-layer black phosphorus exhibits distinct Raman spectra sensitive to its environment.
• Hexagonal boron nitride (h-BN) is a van der Waals material used for encapsulating 2D materials.

Purpose of the Study:

• To investigate the effect of h-BN encapsulation on the Raman spectrum of few-layer black phosphorus.
• To understand how encapsulation influences phonon scattering and interlayer interactions.
• To identify new Raman modes and their origin in encapsulated black phosphorus.

Main Methods:

• Raman spectroscopy was performed on few-layer black phosphorus flakes encapsulated with h-BN.
• Analysis of Raman mode line widths to determine phonon scattering rates.
• Identification and characterization of new Raman peaks in the spectra.

Main Results:

• h-BN encapsulation significantly reduced the line width of black phosphorus Raman modes.
• A previously unobserved Raman peak was detected approximately 4 cm^-1 above the A mode in thicker flakes.
• This new mode is attributed to strong interlayer interactions and surface atom vibrations.

Conclusions:

• h-BN encapsulation enhances the quality of few-layer black phosphorus by reducing phonon scattering.
• The newly observed Raman mode provides insights into interlayer coupling in black phosphorus.
• This mode can serve as an indicator of the surface quality and encapsulation effectiveness.