What Is Raman Spectroscopy?
Raman spectroscopy analyzes the inelastic scattering of monochromatic light, usually from a laser, to identify molecular vibrations and gain insight into a substance’s structure and composition. Raman scattering occurs when incident photons interact with molecular or lattice vibrations within the sample, causing a shift in energy that results in scattered light with different wavelengths, either higher (anti-Stokes) or lower (Stokes) than the incident light. Each material exhibits a unique Raman spectrum, enabling reliable identification and characterization based on its molecular structure and composition.
High Spatial and Depth Resolution
High Spatial and Depth Resolution
Achieves sub-micron mapping with <0.5 µm spatial and <2 µm depth resolution.
Versatile Sample Compatibility
Versatile Sample Compatibility
Analyzes solids, liquids, and gases, even through transparent containers, without damaging samples.
Enhanced Sensitivity Options
Enhanced Sensitivity Options
Uses SERS and multiple excitation lasers to detect trace compounds across diverse materials.
Why Use Raman Spectroscopy?
Raman spectroscopy can be used to map or identify the structure & chemistry of samples at the sub-micron scale. The Raman signal is often used to identify the type and nature of chemical compounds by comparing the sample signature against reference standards.
Unique Chemical Fingerprinting
Provides distinct molecular signatures for accurate material identification.
Non-Destructive High-Precision Analysis
Delivers structural and chemical insights without altering or damaging samples.
Wide Industry Applications
Supports analysis in semiconductors, pharmaceuticals, polymers, and advanced materials research.
Covalent’s Capabilities Offer Raman Spectroscopy
for Non‑Destructive Sub Micron
Chemical Analysis
Working Principle
A confocal Raman microscope uses a laser to illuminate a microscopic sample and collects the inelastically scattered light through a pinhole to obtain high-resolution chemical information from specific depths within the sample.
Equipment Used for Raman Spectroscopy:
Our Raman and photoluminescence spectroscopy capabilities span multiple instrument platforms, allowing us to tailor laser excitation wavelength, confocal optics, and measurement conditions to each sample and application. We also integrate Raman spectroscopy with complementary analytical techniques to deliver a more complete understanding of a sample’s composition, structure, defects, and material properties.
- Confocal Raman and photoluminescence (PL) microscope designed for advanced materials and semiconductor characterization
- Excitation sources:
- 355 nm.
- 532 nm.
- 300 mm wafer capability: Motorized vacuum wafer stage supports automated mapping and characterization of semiconductor wafers up to 300 mm in diameter.
- TrueSurface™ Topography tracking: Maintains optimal focus across rough, curved, patterned, and non-planar samples by automatically following surface topography.
- Vibration-isolated platform: enables high stability measurements.
- Configurable spectral resolution: Multiple spectrometer grating options can support both wide spectral range acquisitions and high-resolution characterization.
- Multiple Excitation Lasers:
- 455 nm.
- 532 nm.
- 785 nm.
- Laser Power with precision controls: 0.1 mW power increments.
- Spatial Resolution: Better than 0.5 micron.
- Confocal Depth Resolution: Better than 2 micron.
- Maximum image area: 101.6 mm x 76.2 mm.
Key Differentiators
- Excitation in the UV, VIS, and NIR for various sample types.
- Micron and sub-micro scale information can be obtained.
- Topography-aware measurements – TrueSurface™ tracking maintains focus across patterned and non-planar semiconductor structures.
- Surface enhanced Raman scattering (SERS) can provide enhanced sensitivity for certain compounds.
Strengths
- Non-destructive.
- Can measure samples through glass and other transparent containers.
- Works for most samples, liquids, gases or solids.
- Confocal microscopy provides depth resolution (~1-2um) for non-destructive depth profiling of layered.
Limitations
- Laser confocal microscope configuration probes a small spot/volume, around 1um, which requires multiple spots to adequately sample heterogeneous materials. Fast mapping of many particles or locations can be beneficial.
- Most metals are difficult/impossible to measure.
- Highly fluorescent samples can overwhelm the weaker Raman signal, in certain cases higher or lower excitation wavelengths can overcome this.
- Certain vibrational modes are forbidden due to sample symmetry.
Unsure Whether Raman Spectroscopy Is Right for You?
Learn more about using Raman spectroscopy chemical analysis services today.
Sample Information
Raman spectrum of liquid nitrogen demonstrating the high spectral resolution of the WITec 360 Raman microscope. A Lorentzian fit to the Raman peak yields a linewidth of 0.42 cm-, highlighting the system’s ability to resolve closely spaced spectral features and perform accurate Raman shift measurements.
UV Raman spectrum of crystalline quartz. The spectrum clearly resolves the characteristic Si–O vibrational mode near 464 cm-1 with a high signal-to-noise ratio. UV excitation enhances Raman scattering efficiency while suppressing fluorescence, enabling sensitive characterization of silica-based materials, thin films, minerals, and semiconductor process materials.
Comparison of Raman spectra for polystyrene, polypropylene, and high-density polyethylene, illustrating distinct peak patterns that enable clear discrimination and identification of these polymers.
Raman spectra of boron nitride, silicon carbide, and diamond highlighting the distinct strong phonon peaks characteristic of each material.
What we accept:
Sample must be stable under laser irradiation; reduced power can be used to mitigate. Strongly absorbing samples can be sensitive.
Use Cases
Analysis of Graphite Quality
Raman spectroscopy evaluates graphite crystallinity and defect density by examining the intensity and shape of the D, G, and 2D bands. In addition to quality different polymorphs (nanotubes, graphene, C60, diamond, etc.) can be easily distinguished.
Strain Mapping in Semiconductors
Raman shifts of phonon modes are sensitive to strain and provide a non-destructive way to detect and quantify strain/stress in semiconductor wafers and devices. Using the mapping capabilities strain gradients at the microscale can be characterized.
Mapping Active Ingredients in Pharmaceuticals
Raman imaging allows spatially resolved identification and distribution of active pharmaceutical ingredients (APIs) and excipients within tablets and other solid formulations. Often used to QA/QC in pharmaceutical manufacturing. Different crystal polymorphs can also be distinguished.
Polymer Identification
Raman spectroscopy enables identification of polymer materials by comparison to an extensive reference library. This is well suited for small particles, thin layers and localized contamination where FTIR is not practical. Raman can also measure particles behind transparent materials like glass as it relies on visible or NIR light.
Battery Development
Identifying active materials, monitoring structural and chemical changes from cycling, and mapping compositional variations across electrodes and solid electrolytes. Supporting materials research, quality control, and failure analysis.
Photonics & Quantum Materials
Crystal quality assessment, stress characterization, phase identification, and structural characterization of optical materials, wide-bandgap semiconductors, integrated photonic devices, and quantum materials.
2D Materials
Layer number determination, crystal quality assessment, strain and doping analysis, phase identification, and spatial mapping of transition metal dichalcogenides (TMDs) and van der Waals heterostructures.
Minerals and Geology
Rapid, nondestructive identification of minerals, phases, and polymorphs based on their characteristic vibrational signatures. Spatially resolved measurements support mineral mapping, inclusion analysis, contamination identification, and characterization of geological materials with micron-scale spatial resolution.
Complementary Techniques
- Photoluminescence (PL) – Performed on the same instrument platform, PL complements Raman by providing information on defect-related emission, optical quality, and electronic transitions.
- FTIR and AFM-IR provide complementary analysis of bonding vibrational modes, particularly for organic samples.
- SEM-EDS provides complementary chemical information.
- XRD provides complementary structural information
Why Choose Covalent for Your Raman Spectroscopy Needs?
Covalent combines advanced confocal Raman microscopy with a broad portfolio of materials characterization and failure analysis capabilities. Our Raman spectroscopy platforms offer multiple excitation wavelengths, configurable spectral resolution, and high-spatial-resolution mapping, allowing measurements to be optimized for a wide range of materials and analytical challenges.
Beyond collecting Raman spectra, we help customers understand the underlying causes of observed material behavior. Raman results can be integrated with our in-house spectroscopy, profilometry, SEM, XPS, FIB, TEM, XRD, and other analytical techniques to accelerate root-cause investigations, process optimization, product development, and materials research.
Frequently Asked Questions
Identifying the right test can be complex, but it doesn’t have to be complicated.
Here are some questions we are frequently asked.
What spatial resolution can be achieved?
Lateral spatial resolution can be better than 1um using a high numerical aperture objective. Individual point spectra and maps are possible.
What depth resolution can be achieved?
Depth resolution of 1-2um can be achieved using dry objectives and can be improved using oil immersion objectives. A variety of well-characterized immersion oils are available to minimize overlap of the oil Raman peaks with the sample.
What types of materials can be analyzed?
Solids, liquids, and gases—including pharmaceuticals, polymers, minerals, biological samples, and more. Non-volatile liquids can be measured easily as drops on a metal substrate, and volatile or hazardous liquids can be measured in a cuvette.
Does Raman damage samples?
Raman spectroscopy is generally non-destructive and requires little to no sample preparation. Laser power can be adjusted to minimize heating or damage in sensitive materials.
Can Raman detect stress and strain?
Small shifts in Raman peak position can be used to measure stress and strain in materials such as silicon, SiC, and other semiconductors.
Can Raman measurements be performed across large sample areas?
Yes, automated Raman mapping can perform automated measurements over areas ranging from a few microns to entire 300 mm wafers.
Can Raman distinguish different crystal phases or polymorphs?
Yes, Raman spectroscopy is highly sensitive to crystal structure and molecular bonding, making it an excellent technique for identifying phases, polymorphs, and crystallinity in many materials.