Top: enhanced contrast palette image of the ratio of the AFMIR intensity maps at 1710 and 1600 cm⁻¹ of region of interest “A”. The white contour delineates the AFM sample boundaries as defined by the AFM. The white circles denote the locations where full spectra were acquired. Bottom: histogram of the ratio of the AFMIR maps at 1710 and 1600 cm⁻¹ for the whole region of interest “A”.