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The optical properties of various PEDOT:PSS films obtained by drop casting and blade coating are analyzed by variable-angle spectroscopic ellipsometry in the visible-UV spectral range. We discuss observed differences in the optical spectra due to PSS content and DMSO treatment and correlate them to structural changes extracted from Raman measurements. In particular, we investigate the optical anisotropy of the complex refractive indices which arises from the in-plane arrangement of the PEDOT backbones, giving rise to optically uniaxial behavior with the optic axis perpendicular to the film plane. Although this is widely accepted, most investigations disregard the anisotropy for simplicity, which sometimes leads to inaccurate conclusions. In this work, we compare the results of isotropic and anisotropic analyses to clarify which kind of errors we can expect if anisotropy is not considered. Finally, the correlation between Raman scattering and ellipsometric analyses shows that not only local structural changes of the chain conformation but also the overall morphology of the composite films are significant in the interpretation of Raman spectra.
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http://dx.doi.org/10.1021/acsomega.2c05945 | DOI Listing |
Sci Rep
August 2025
Department of Basic and Applied Sciences for Engineering, Sapienza University of Rome, 00161, Rome, Italy.
This study explores the potential of Bloch surface waves (BSWs) at the interface of a finite one-dimensional photonic crystal (1D-PC) and vacuum, exploiting spectroscopic ellipsometry in a range that encompasses the mid-infrared (4000 cm to 200 cm). BSWs can be excited in both σ and π polarizations, which in the ellipsometric configuration can be detected at the same time, presenting distinct advantages for sensor applications targeting the growth of thin solid films and molecular monolayers, surface-adsorbed gas molecules, and liquid droplets. Compared to other sensing techniques exploiting mid-infrared vibrational absorption lines for chemical-specific sensitivity, like waveguides, nano-antenna arrays, metasurfaces, attenuated total reflectance (ATR) in crystals or in optical fibers, the present approach features high field enhancements, strong field confinement, and large quality factors of the resonances, all while relying on a rather simple and potentially low-cost configuration.
View Article and Find Full Text PDFACS Appl Mater Interfaces
August 2025
Department of Physics, Chungbuk National University, Cheongju 28644, South Korea.
Thin-film components employed in modern semiconductor fabrication are becoming increasingly ultrathin, often exhibiting porous, nonuniform structures with open surfaces that exhibit properties distinct from those of the bulk materials. Precise characterization of these ultrathin layers is essential to optimize device performance. However, conventional characterization techniques often lack the sensitivity necessary for the analysis of films thinner than 10 nm.
View Article and Find Full Text PDFThe dual-rotating compensator Mueller matrix ellipsometer is a well-established and commercially mature instrument, with its compensators typically modeled as linear retarders. However, in many practical implementations, these compensators behave as elliptical retarders rather than purely linear ones. Accurate calibration of the compensators is essential to ensure proper instrument functionality, but calibrating elliptical retarders is considerably more complex than calibrating linear ones.
View Article and Find Full Text PDFThis paper describes a dynamic spectroscopic ellipsometer that can extract accurate () and () dynamically without ambiguity problems. We address how quadratic equations cause ambiguity in extracting () and how the ambiguity problem is solved by employing a wedge-window monolithic polarizing interferometric (W-MPI) device. To prove the benefit of the proposed W-MPI scheme, some experiments are conducted using four thin-film samples with a wide range of thicknesses.
View Article and Find Full Text PDFWe present an angle-resolved channeled spectroscopic micro-ellipsometry (ACSE) system operating in a near-normal-incidence configuration with a line-scan spectrometer. The hardware covers the visible spectral range from 480 to 680 nm and provides incidence angles from 0° to 60°. By analyzing the spectral interference envelope, we accurately separate and extract the low-frequency (DC) and high-frequency (AC) components of the interferometric signal, corresponding to the baseline intensity and modulation, respectively.
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