Microspectroscopy


Figure 8: Optical images and O-PTIR spectra of sample A (top) and sample B (bottom) from two locations indicated by the red arrows where there were unidenti- fied organic contaminants on the surface of a recording head. The middle red spectrum of nylon was obtained via a digital search of the KnowItAll IR database.


this defective thin-film transistor display. Use of conventional ATR microscopy would have been limited by presence of the thin film, obstructing direct access to the contamination par- ticle. Te sample was able to be analyzed via O-PTIR with- out additional sample preparation or the need to perform any physical extraction of the particle. Both the pump IR and probe-visible lasers penetrated the thin metal film and were focused on the contamination that lies beneath. Te probe laser detected the photothermal expansion of and


was reflected


the particles back


through the metal film and onto the photodetector. Examination of the spectra, particularly the presence of the strong broad IR absor- bance band at the 1706 cm−1 band, suggests that this sus- pect contamination particle may have been a vulcanized styrene-butadiene rubber (SBR) that has oxidized to form a carboxylic acid.


Conclusion We have introduced a new IR microscopy modality called


O-PTIR spectroscopy that can be coupled to Raman micros- copy for submicron simultaneous IR and Raman micro- spectroscopy. Seagate chose the mIRage system to improve


Figure 9: Optical image showing a ∼5 μm defect on the surface of a recording head. The O-PTIR spectrum collected from the center of the defect is an excellent match with the reference spectrum of a polyetherimide found in the KnowItAll database of digitized IR spectra.


2020 May • www.microscopy-today.com 33


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