Infrared-spectroscopic single-shot laser mapping ellipsometry: Proof of concept for fast investigations of structured surfaces and interactions in organic thin films

• Published in: Applied surface science 2017-11, Vol.421, p.440-445
• Main Authors: Furchner, Andreas, Kratz, Christoph, Gkogkou, Dimitra, Ketelsen, Helge, Hinrichs, Karsten
• Format: Article
• Language: English
• Subjects: Infrared-spectroscopic single-shot laser mapping ellipsometry; Molecular interactions; Structured surfaces
• ISSN: 0169-4332; 1873-5584
• DOI: 10.1016/j.apsusc.2016.08.140

[Display omitted] •An IR-spectroscopic mapping ellipsometer is developed based on a single-shot concept.•The ellipsometer is coupled to a broadband quantum cascade laser (1800–1540cm−1).•Unprecedented time resolutions of 60ms are reached.•Mapping and spectroscopic features are applied for thin-film characterization. We present a novel infrared-spectroscopic laser mapping ellipsometer based on a single-shot measurement concept. The ellipsometric set-up employs multiple analyzers and detectors to simultaneously measure the sample's optical response under different analyzer azimuths. An essential component is a broadly tunable quantum cascade laser (QCL) covering the important marker region of 1800–1540cm−1. The ellipsometer allows for fast single-wavelength as well as spectroscopic studies with thin-film sensitivity at temporal resolutions of 60ms per wavelength. We applied the single-shot mapping ellipsometer for the characterization of metal-island enhancement surfaces as well as of molecular interactions in organic thin films. In less than 3min, a linescan with 1600 steps revealed profile and infrared-enhancement properties of a gradient gold-island film for sensing applications. Spectroscopic measurements were performed to probe the amide I band of thin films of poly(N-isopropylacrylamide) [PNIPAAm], a stimuli-responsive polymer for bioapplications. The QCL spectra agree well with conventional FT-IR ellipsometric results, showing different band components associated with hydrogen-bond interactions between polymer and adsorbed water. Multi-wavelength ellipsometric maps were used to analyze homogeneity and surface contaminations of the polymer films.