Fig. 2: Ellipsometry characterization and optical imaging setup for DL-pACGs. | npj Nanophotonics

Fig. 2: Ellipsometry characterization and optical imaging setup for DL-pACGs.

From: Imaging-based quantification of sub-25 nm coking layer on Au by dielectric-loaded plasmonic azimuthally chirped gratings

Fig. 2

a Ellipsometry characterization of the refractive index of thin carbon films with nominal thicknesses ranging from 5 to 25 nm, measured across a spectral range of 200 to 1000 nm. b Schematic of the optical setup used for capturing the reflectance image. Unpolarized white light from the light source (LS) first passes through the collector lens (CL), then enters the vertical illuminator, which includes an aperture diaphragm (AD), a lens, field diaphragms (FD), a field lens (FL), and a bandpass filter (BP). The light is then reflected by a beamsplitter and directed through the objective (OBJ) to illuminate the specimen under Köhler illumination. Reflected light from the specimen’s surface re-enters the objective and is directed into the camera (CCD). The insets in b show a representative bright-field CCD image under green light illumination (upper inset) and SEM image (lower inset) of the DL-pACGs used in this work. The contrast in the SEM image comes from the difference in electron scattering efficiency of gold (bright) and PMMA (dark).

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