Fig. 3: Comparison of PMMA subsurface layers and thin PMMA surface layers. | Nature Communications

Fig. 3: Comparison of PMMA subsurface layers and thin PMMA surface layers.

From: Subsurface chemical nanoidentification by nano-FTIR spectroscopy

Fig. 3

a, c Peak heights \(\varphi _n^{{\mathrm{max}}}\) and b, d spectral peak positions \(\omega _n^{{\mathrm{max}}}\) extracted from experimental (large dots) and calculated (lines) nano-FTIR phase spectra, as a function of PMMA depth d2 (left column) and PMMA thickness t1 (right column), for different demodulation orders n = 3 (red) and n = 4 (blue). The solid and dashed lines are calculated with and without the far-field factor (1 + r)² in Eq. (1), respectively. The gray horizontal dotted line indicates the peak position ωref experimentally obtained on thick (bulk) PMMA samples. Inset: definition of \(\varphi _n^{{\mathrm{max}}}\) and \(\omega _n^{{\mathrm{max}}}\). Each experimental data point shows mean values and standard deviation (error bars) obtained from ten averaged (5×) spectra (16 averaged spectra for d2 ≥ 85 nm).

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