Fourier Transform Infrared Spectroscopy (FTIR)
Fourier Transform Infrared Spectroscopy (FTIR) is an effective analytical technique for quickly identifying the “chemical family” of a substance. Typically, organic and polymeric compounds (and, to a lesser degree, inorganic compounds) produce a “fingerprint” IR spectrum, which can be compared to EAG’s extensive reference database, and the unknown component’s chemical family or actual identity may be determined.
FTIR measures the absorbance of infrared light by a sample and generates a spectrum based on the functional groups in the material. In addition to typical sample preparation methods (such as micro-extraction, dilution, KBr pellet and mulling techniques), EAG also utilizes various Attenuated Total Reflectance (ATR) accessories, which allows insoluble or multi-layer samples to be examined directly.
Ideal Uses of FTIR
- Characterization and identification of complex mixtures of materials, including gases, liquids and solids
- Identification of organic contaminants (e.g. particles, residues) on the macro and micro scales
- Quantification of Oi in Si wafers and H in SiN, SiON and a-Si thin films (Si-H vs. N-H)
- Medical device chemical characterization via ISO 10993:18
Strengths
- Capable of identifying organic functional groups and often specific organic compounds
- Extensive spectral libraries for compound and mixture identifications
- Ambient conditions (vacuum is not necessary; applicable for semi-volatile compounds)
- Minimum (limit of detection) analysis area: ~15-50 µm. Rule-of-thumb: if you can see the sample by eye, it most likely can be analyzed.
- Can be quantitative with appropriate standards and uniform sample thicknesses
- Complementary to Raman spectroscopy
Limitations
- Firstly, limited surface sensitivity (typical limit of detection is a film thickness of 100 nm)
- Only specific inorganic species exhibit an FTIR spectrum (for example: yes: silicates, carbonates, nitrates and sulfates; no: titinia, oxides, etc.)
- Sample quantitation requires the use of standards
- Glass absorbs infrared light and is not an appropriate substrate for FTIR analysis
- Water also strongly absorbs infrared light and may interfere with the analysis of dissolved, suspended or wet samples
- Simple cations and anions, e.g., Na+ and Cl–, do not absorb FTIR light and hence cannot be detected by FTIR. Identification of mixtures/multiple sample components may require additional laboratory preparations and analyses.
- Lastly, FTIR cannot analyze metals that reflect light
FTIR Technical Specifications
- Signal Detected: Infrared absorption
- Elements Detected: Molecular functional groups (NOT elements)
- Detection Limits: 1-10 wt% (quantification of known components); 5-20 % (identification of unknown components)
- ATR Depth Resolution: ~0.1-1 micron
- Transmission FTIR: Infrared light passes through the entire sample
- Imaging: No mapping for FTIR
- Lateral Resolution/Probe Size: > 15-50 µm
In conclusion, EAG offers our customers FTIR services to analyze many materials. Moreover, you can count on fast turnaround times, accurate data and person-to-person service, ensuring you understand the information that you receive.
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