High resolution electron microscopy of crystalline polymer wedges

High resolution electron micrographs (HREM) of wedge-shaped crystalline samples of the polydiacetylene 1,6-di(N-carbazolyl)-2,4-hexadiyne (DCHD) are compared to quantitative predictions of image contrast obtained from dynamical electron scattering theory. Multislice calculations using experimentally determined instrument operating parameters make it possible to interpret the variation in HREM image contrast as a function of crystal thickness. Pendellِsung plots of the intensity of the main beam and the scattered beams as a function of thickness corroborate characteristic features in the lattice images including extinctions and half-spacings. The position of these contrast features with respect to the edge of the polymer crystal wedge are compared to the theoretical calculations and used to estimate the height profile. This profile is then compared to wedge height profiles measured with scanning probe microscopy (SPM). The two approaches give similar results for DCHD crystal thicknesses below 50 nm.