Measuring ultrathin metal coatings using SPR spectroscopic ellipsometry with a prism-dielectric-metal-liquid configuration.

Abstract

A new surface plasmon resonance (SPR) configuration is proposed, which consists of a prism, a dielectric layer, a metal coating, and a matching liquid. The optical constants of each layer in the proposed prism-dielectric-metal-liquid (PDML) configuration have been optimized to match the SPR conditions and reach the strongest intensity. Combining the PDML configuration with spectroscopic ellipsometry, SPR spectroscopic ellipsometry (SPRSE) with a PDML configuration was developed. The SPR wavelength can be adjusted to the desired wavelength by varying the thickness of the dielectric layer. The amplitude and phase change, magnified by the SPR in the visible and near-infrared wavelengths, were obtained to determine the optical constants and thickness of ultrathin metal coatings. The extracted optical constants were found to be in good agreement with the results obtained using transmission electron microscopy (TEM) and X-ray reflectivity (XRR) techniques. These SPRSE measurements show great potential for characterizing the interface between a metal coating and a dielectric layer, and the surface uniformity of ultrathin metal coatings.