Sequential monitoring of film thickness variations with surface plasmon resonance imaging and imaging ellipsometry constructed with a single optical system

Sequential surface plasmon resonance imaging (SPRI) and imaging ellipsometry (IE) measurements are realized with a single set of optical components mounted on a goniometer. The sample situated on top of a triangular prism is positioned in the center of the goniometer. The resultant setup (SPRI/IE) can be used to examine the same surface region above (IE) and below (SPRI) the sample. Thickness values of silver stripes sputtered onto a gold substrate were determined by SPRI and IE, and the results were compared to establish the validity of the method. The SPRI/IE setup was also used to monitor the thickness of phospholipid films of different layer numbers. SPRI measurements were found to be more accurate for ultrathin films, whereas the IE results are more reliable for films whose thicknesses approach or exceed the distance encompassed by the evanescent wave of the surface plasmon. Thus, utilizing these two techniques sequentially facilitates the continuous monitoring of film thickness variation over a wide thickness range with high fidelity and provides a viable approach to image the surface regions with large topographic fluctuations.