Quantitative, nanoscale mapping of sp2 percentage and crystal orientation in carbon multilayers

Experimental and analytical techniques are introduced for the quantitative, nanoscale mapping of chemical bonding information in carbon-based materials. With these techniques, the spatial orientation of graphitic crystallites in tetrahedrally bonded amorphous carbon was imaged. Simultaneously, the percentage of sp2- and sp3-bonded carbon could be mapped quantitatively, all with spatial resolution of just a few nanometers. Two electron energy-loss spectroscopy (EELS) techniques were compared: low-loss mapping of the plasmon energy and core-loss mapping of the carbon ionization edge. The recently developed EELS acquisition routine of binned gain averaging was applied, together with multivariate statistical analysis, providing a robust method for obtaining real-space, two-dimensional bonding maps.