Optical properties of sputtered fluorinated ethylene propylene and its application to surface-plasmon resonance sensor fabrication
Optical dispersions ranging in wavelength from on Si and from on glass for sputtered FEP thin films and bulk FEP target material. The Cauchy fits are only reported over the range that the wavelengths were fitted as the fits change slightly with wider ranges, reflecting that the Cauchy fit is indeed a good approximation to a more complicated film structure. Refractive index for increasing thickness films (Run 1, Run 2, and Run 3) is plotted for (a) Si and (b) glass substrates. Absorption is plotted for all three runs on (c) Si.
Roughness as measured with an AFM on the third deposited film on (a) BK7 and (b) Si.
Three-dimensional model of the dual-mode surface-plasmon resonance sensor. The sensor is illuminated using total-internal reflection through a BK7 glass hemispherical prism. Two surface-plasmon modes are excited at different angles. This leads to a reflection spectrum with two minima whose angles are sensitive to both surface and bulk refractive index changes. An experimental dual-mode SPR sensor, illuminated with green light for illustrative purposes, is shown in the inset.
Simulated transverse magnetic (TM) polarized reflectivity vs angle for an light introduced through a BK7 prism at angles ranging from 64° to 76°. The sensor surface is comprised of thick sputtered FEP and thick Au. Ethanol was used as analyte. The reflection minima correspond to long- and short- range surface plasmons, respectively.
Sputtered FEP film thicknesses and roughness. The ellipsometry thickness measurements agreed well with those from a Veeco Dektak profiler. Roughness was included in the ellipsometry analysis according to a realistic value found using an AFM (average peak to peak roughness). Locations where N/A is used mean that the roughness was negligible (much less than ), so was excluded from the ellipsometry fit. An thick layer was used in the model on all Si substrates.
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