Raman Spectroscopy

Figure 1. Raman spectroscopy equipment.

Features

Raman spectroscopy is a method for obtaining information on the structure of a molecule by utilizing the Raman light scattering, that is, frequency change of the incident light due to interaction with a molecule. By analysing the spectrum, it is possible to obtain information on the molecular structure of a sample. The diameter of the LASER beam is about 1 µm so it is possible to analyse smaller regions of interest (ROI) compared to Fourier transform infrared (FT-IR) spectroscopy.

Application Examples

• Qualitative analysis of contaminants

• Structure of thin carbon films

• Structure of \(\text{Si}\text{O}_{x}\) films

• Strain and crystallinity of Si

• Resin hardening

• Crystallinity of compound semiconductors

Principle

Raman scattering is a phenomenon in which the frequency of scattered light, \(\nu\), is shifted from the incident light frequency \(\nu_{0}\). The amount of shift corresponds to the vibrational energy levels in atomic groups and can be both negative (Stokes shift) and positive (anti-Stokes shift, see Figure 2). It is thereby possible to identify the vibrational modes of atomic groups contained in the analytical sample and obtain information on the coupling state.

Figure 2. Principle of Raman spectroscopy.

Equipment configuration

Figure 3. Beam diameter of after passing the microscope objective lens is about 1 \(\mu\text{m}\) and possible excitation wavelengths are 785, 632.8, 532, and 457 nm, respectively.

Data examples

Figure 4. Example of a Raman spectrum where each peak corresponds to a vibration mode of the atoms indicated.
Figure 5. Example of substance identification through searching a library of known spectra.

Data delivery formats

• Spectrum: PDF file

• Spectral data in Microsoft^® Excel^® file (.xlsx) on request

Measurement specifications

Property	Value	Unit	Notes
Maximum sample size	\[200 \times 300\]	mm
Maximum sample height	15	mm
Measurable region	\[150 \times 150 \times 15\]	\[\text{m}\text{m}^{\text{3}}\]
Measurement spot diameter	1	\[\mu\text{m}\]	\(100 \times\) objective lens
Magnifications	10, 50, 100	\[\times\]	Selection of objective lenses

Items for enquiries

• Purpose and scope of the analysis

• Sample information:

  1. Quantity, availability of pre-analysis samples

  2. Structure, shape, layer structure, film thickness, presence or absence of pattern, expected substances, etc.

  3. Care instructions

• Delivery date:

  1. Desired delivery dates of preliminary and final results

  2. Handling instructions

• Other relevant information

Caution

• LASER irradiation may cause thermal damage to the sample.

• Materials with strong fluorescence may be impossible to measure.