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Raman spectrum for each individual layers on a 90 nm . The band peaks are normalized to the band.
Thin graphene flakes on 90 nm imaged on an optical microscope under (a) TM and (b) TE polarizations. (c) Red, (d) green, and (e) blue wavelength images were obtained by selecting the corresponding wavelengths. Each column represents images taken at 0°, 23°, 55°, and 60°, respectively. The dotted circle is the spot used for the contrast measured of a monolayer.
Top: model used for our analysis. Optical reflection for a three-layer system. Bottom: contrast plot for TE and TM polarizations as function of wavelength and angles for a 90 nm substrate. The expected contrast is shown on the color scale found on the right.
Comparison of experimental (color curve) and calculated (black curve) contrast plot as a function of angle at a fixed wavelength. (a) Red contrast plot at a wavelength of 620 nm and (b) green contrast plot at 495 nm. (c) Blue contrast plot at 450 nm. The error bars are the standard deviations for three different data sets and the line is a guide for the eyes.
Contrast plot as a function of angles and wavelength with fixed thickness of 2 nm of GaAs, 140 nm of AlAs and TM polarizations. The inset shows the structure used for our calculation.
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