Fringe and Noise Reductions of pMAIRS Spectra Using Principal Component Analysis.

Infrared p-polarized multiple-angle incidence resolution spectrometry (pMAIRS) is a promising analytical tool for revealing the molecular orientation quantitatively of each chemical group in a thin film even with surface roughness. The spectra are often disturbed by noise and fringe, however, due to the multiple reflections in the substrate and the film, which makes the quantitative analysis very difficult. Therefore, improvement of the signal to noise (SN) ratio of the spectra is expected. Principal component analysis (PCA), in the present study, is first applied to the noise reduction for pMAIRS spectra of a poly(3-hexylthiophene) spin-coated thin film by employing the spin-speed as the experimental parameter. As a result, high quality pMAIRS spectra are readily obtained, with which highly reliable quantitative discussion is made.