Comparison of NFIM and FIM of polymer layers with tetracyanoethylene and benzene as image gases

Field ion microscopy (FIM) with positive ions and negative ions (NFIM) is compared for polymer layers of two structures grown by field induced anionic polymerization of tetracyanoethylene (TCNE) on a metal tip. The positive and negative ion images of the polymer layer mainly consisting of linear polymer chains are complementary, i.e. positive ion emission is preferentially observed in dark areas of the corresponding negative ion images. For the layer with a crosslinked polymer structure the bright rings of negative ion images are not observed in positive ion images. The dissimilarities between NFIM with TCNE and FIM with benzene and TCNE are attributed to differences in the excess electron and electron hole conductivities of the polymer layers exposed to the image gases.