Top: DC06-07-18-b, ratio of the AFMIR maps at 1710 and 1600 cm⁻¹ of the region of interest B. The orange contour delineates the AFM sample boundaries. Positionsfor the individual spectra presented in the middle panel recorded on a 8 × 8 equally sampled map are indicated on top of the ratio map. Middle: individual AFMIR spectra in the 1850–1550 cm⁻¹ range recorded on an evenly spaced 8 × 8 map, with 0.7 μm spacing on the x-axis and 0.38 μm spacing on the y-axis. The spectra are deconvolved into two main bands corresponding to the carbonyl (C=O) dominating the 1710 cm⁻¹, and contribution from the carbon backbone contributing to the 1600 cm⁻¹ map. Bottom: histogram of the ratio of the AFMIR maps at 1710 and 1600 cm⁻¹ of region of interest B.