Presented are transmission electron microscopic observations of micron-sized single crystals of poly(9,9-di-n-octyl-2,7-fluorene) (PFO) prepared from thin films in the melt state. A preliminary determination of unit cell dimensions and molecular packing (orthorhombic, a = 2.56 nm, b = 2.34 nm, c = 3.32 nm, 8 chains, with space group P212121 and density 1.041 g mL-1) was made via combined considerations of the selected-area electron diffraction (SAED) pattern obtained along the [00l] zone of the single crystals, the SAED “fiber” pattern obtained from shear-oriented films, and the “powder” pattern from X-ray diffraction of melt-crystallized thick films in the absence of preferred orientation. In this model, PFO backbones are generally separated by transversely extended alkyl side chains, consistent with the dominance of single-chromophore emissions and the general lack of interbackbone delocalization of PFO chains in this ordered state as indicated by earlier photophysical studies. In addition, microscopic evidence for the presence of a vast number of nanograins was presented, and its implications in the crystallization process of semirigid PFO chains were discussed.

Transmission electron microscopy (TEM) has been utilized to study the nickel-silicide growth in self-supported lateral-diffusion, thin-film couples by overlapping deposited layers of Ni and Si between two silicon oxide deposited films. Energy-dispersive x-ray spectroscopy, microdiffraction, and selected area diffraction were used to identify the Ni-silicide phases and their crystal structures. Long-grain growth of Ni2Si, as a result of phase-boundary migration induced by diffusion, was observed during in situ annealing between 500 and 750 °C in TEM. No preferred orientation or particular crystallographic relationship was found among the long grains.