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Application of scanning angle Raman spectroscopy for determining the location of buried polymer interfaces with tens of nanometer precision

TitleApplication of scanning angle Raman spectroscopy for determining the location of buried polymer interfaces with tens of nanometer precision
Publication TypeJournal Article
Year of Publication2015
AuthorsDamin, CA, Nguyen, VHT, Niyibizi, AS, Smith, EA
JournalAnalyst
Volume140
Pagination1955-1964
Date Published03
Type of ArticleArticle
ISBN Number0003-2654
Accession NumberWOS:000350573400029
Keywordsdepth resolution, homogeneous molecular profiles, integrated-optics, interferometry, microscopy, optical, scattering, thickness, thin-film, total internal-reflection, wave-guides
Abstract

Near-infrared scanning angle (SA) Raman spectroscopy was utilized to determine the interface location in bilayer films (a stack of two polymer layers) of polystyrene (PS) and polycarbonate (PC). Finite-difference-time- domain (FDTD) calculations of the sum square electric field (SSEF) for films with total bilayer thicknesses of 1200-3600 nm were used to construct models for simultaneously measuring the film thickness and the location of the buried interface between the PS and PC layers. Samples with total thicknesses of 1320, 1890, 2300, and 2750 nm and varying PS/PC interface locations were analyzed using SA Raman spectroscopy. Comparing SA Raman spectroscopy and optical profilometry measurements, the average percent difference in the total bilayer thickness was 2.0% for films less than similar to 2300 nm thick. The average percent difference in the thickness of the PS layer, which reflects the interface location, was 2.5% when the PS layer was less than similar to 1800 nm. SA Raman spectroscopy has been shown to be a viable, non-destructive method capable of determining the total bilayer thickness and buried interface location for bilayer samples consisting of thin polymer films with comparable indices of refraction.

DOI10.1039/c4an02240h
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