Raman Microscopy (Raman)

Raman map showing how the biaxial stress state induced by deposition of a semiconductor thin film on a lattice mismatched substrate illustrates the interplay between processing and physical properties.

Raman spectroscopy is a chemical analysis technique which probes the vibrational modes of compounds. It produces a spectrum which can provide fingerprint identification of materials when compared against a reference library of known standards.

Strengths

High spatial resolution
Signature can be used to identify chemical species

Limitations

Low probability process needs significant excitation energy
Energy levels used can damage some materials
Non-linear phenomena

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Example Outputs Instruments Used How Raman Works

Raman Microscopy Services

Raman Microscopy

Raman spectroscopy is a chemical analysis technique which probes the vibrational modes of compounds. It produces a spectrum which can provide fingerprint identification of materials when compared against a reference library of known standards.

Sample Requirements

Solid phase

Example Outputs

Raman images are presented in which the image contrast is generated by multivariate curve resolution (MCR) analysis. In this case, MCR finds the differences not only within each image but also across the entire time sequence. A different color is assigned to each resolved component. Each image is from the same 30 µm square portion of the anode. The blue MCR component is indicative of the 1580 cm^-1 band; green the 1590 cm^-1 band; yellow the 154 cm^-1 band; red represents carbon black, a conductivity enhancer.

From: Thermo Scientific Application Note

Raman map showing how the biaxial stress state induced by deposition of a semiconductor thin film on a lattice mismatched substrate illustrates the interplay between processing and physical properties.

From: Thermo Scientific

Instruments Used

ThermoFisher Scientific DXR3xi Raman Spectrometer

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

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How Raman Works

Raman spectroscopy relies on the fact that a molecule (or element) when excited by optical illumination has a finite probability of emitting light which is slightly higher (or slightly lower) than the excitation wavelength.

Photons are emitted with a nonstandard wavelength, caused by the original atom/molecule either losing some energy (resulting in a lower-wavelength photon emission – called the “Stokes shift”) or gaining energy (“anti-Stokes”) from a vibrational energy change in the sample. This change in energy is dependent on the type of sample and the excitation wavelength.

Typically, Raman uses a tightly focused laser beam as the excitation source. Light emitted from the sample is high-pass filtered to remove the laser line and then the intensity as a function of wavelength is measured using a high-resolution spectrometer.

The spectroscopic signature of the Raman signal is often used to identify the type and nature of chemical compounds by comparing the sample signature against reference standards.