Systematic error in conventionally measured Raman spectra of boron carbide-A general issue in solid state Raman...

Area of Science:

• Materials Science
• Solid-State Physics
• Spectroscopy

Background:

• Solid-state Raman spectroscopy is sensitive to laser penetration depth.
• High absorption in semiconductors (e.g., boron carbide) and high reflectivity in metals (e.g., hexaborides) limit bulk phonon excitation.
• Previous Raman spectra of boron carbide have been debated due to surface scattering effects.

Purpose of the Study:

• To investigate the bulk phonon characteristics of boron carbide and related materials.
• To resolve controversies regarding Raman spectra of boron carbide.
• To demonstrate the utility of Fourier transform-Raman spectroscopy for bulk analysis.

Main Methods:

• Solid-state Raman spectroscopy.
• Fourier transform-Raman spectroscopy applied to boron carbide (B4.3C) and alpha-rhombohedral boron.
• Analysis of icosahedral phonon features.

Main Results:

• Fourier transform-Raman spectra of B4.3C show common features of icosahedral phonons.
• Raman spectra of alpha-rhombohedral boron exhibit bulk characteristics.
• These findings refute interpretations based on conventionally measured Raman spectra, which are influenced by surface scattering.

Conclusions:

• Fourier transform-Raman spectroscopy provides access to bulk phonon modes in materials with limited laser penetration.
• The study clarifies the nature of Raman spectra for boron carbide, confirming bulk icosahedral phonon signals.
• This technique is crucial for accurate characterization of semiconductors and metals where surface effects dominate conventional Raman measurements.