Identification of individual nanocrystal structures and morphologies by TEM
Portland State University, US
nanocrystal structure morphology transmission electron microscopy
Two novel methods for the structurally identification of a nanocrystal from either a single high resolution (HR) transmission electron microscopy (TEM) micrograph or a single electron precession diffractogram are described. While the structural information that can be extracted from a HRTEM image is the projected reciprocal lattice geometry, the plane symmetry group, and a few structure factor amplitudes and phases, the structure factor phases are lost in the recording of the electron precession diffractogram. This loss of structure characteristic information is compensated for by the typically much higher structural resolution of electron precession diffractograms and the possibility to determine the space group by including information from higher order Laue Zones. Searching for these kinds of structural information in open access databases (e.g. nanocrystallography.research.pdx.edu and crystallography.net) and matching it with high figures of merit to that of candidate structures allows for highly discriminatory identifications of nanocrystals, even without additional chemical information as obtainable in analytical TEMs. When the structure of a nanocrystal is identified, a series of tilt protocols leads to the determination of the crystal morphology. Components of these methods are demonstrated on both experimental and simulated HRTEM images and diffraction data.
Nanotech 2008 Conference Program Abstract