Raman Spectroscopy Analysis

Scope

Raman spectroscopy covers the non-destructive identification and characterization of materials through their vibrational (Raman) spectra, applicable to solids, liquids, powders, and films. The laser wavelength and configuration are selected to suit the sample and to manage effects such as fluorescence.

Key aspects of the technique include:

• Molecular fingerprinting – identification of compounds and functional groups from the characteristic Raman spectrum, matched against reference spectra
• Phase and polymorph identification – distinguishing crystalline phases, polymorphs, and allotropes that share the same chemical composition but differ in structure
• Raman microscopy and mapping – coupling with a microscope to analyze micron-scale areas and to map the spatial distribution of components across a surface
• Crystallinity and stress – assessing degree of crystallinity and residual stress/strain (notably in semiconductors and carbon materials) from peak position and shape
• Carbon material characterization – characterizing graphene, graphite, diamond, carbon nanotubes, and diamond-like carbon via their distinctive Raman bands (D, G, and 2D bands)
• Laser wavelength options – multiple excitation wavelengths (UV, visible, near-IR) to optimize signal and minimize fluorescence
• Minimal sample preparation – analysis of samples as received, including through transparent containers and in aqueous media

Applications

• Polymer identification and characterization – identifying polymer types, additives, and degradation, and assessing crystallinity
• Semiconductor characterization – measuring stress/strain, crystallinity, and composition in silicon and compound semiconductors
• Carbon and nanomaterials – characterizing graphene layer number and quality, carbon nanotubes, diamond, and DLC coatings from their Raman signatures
• Contaminant and particle identification – identifying unknown particles, inclusions, and surface contamination, often via Raman microscopy
• Mineral and geological analysis – identifying minerals and phases from their characteristic spectra
• Forensic and art analysis – non-destructive identification of pigments, materials, and trace evidence
• Failure analysis support – identifying foreign materials, residues, and phase changes contributing to a failure

Benefits

• Non-destructive molecular fingerprint – Raman identifies materials by their characteristic spectrum without consuming or altering the sample, preserving it for further analysis
• Little to no sample preparation – samples can often be analyzed as received, including through transparent packaging and in water, which is difficult for infrared methods
• Distinguishes phases and polymorphs – because Raman is sensitive to structure as well as composition, it separates polymorphs and crystalline phases that have identical chemistry, a key advantage in pharmaceuticals and materials
• Micron-scale spatial analysis – Raman microscopy maps composition across a surface and analyzes tiny features, particles, and inclusions
• Complements FTIR – Raman and infrared respond to different vibrations, so Raman provides information that infrared misses and vice versa, strengthening molecular identification
• Powerful for carbon and semiconductor materials – Raman is one of the most informative techniques for graphene, carbon materials, and semiconductor stress/crystallinity