TY - JOUR
T1 - Coherent electron nanodiffraction from perfect and imperfect crystals
AU - Zuo, J. M.
AU - Spence, John
N1 - Funding Information:
This work is supported by NSF grant DMA-9015867. The authors are grateful for useful discussions with Professor J. M. Cowley and (particularly in regard to equation (15)) and to Dr J. Rodenburg.
PY - 1993/11
Y1 - 1993/11
N2 - The theory of coherent electron nanodiffraction from strained crystals is developed, based on the column approximation. Contributions to the diffraction pattern from different parts of the crystal under the illumination are considered, and a treatment of high-order weak reflections and diffuse scattering is given based on perturbation theory. Ultimate limits to the spatial resolution of coherent electron nanodiffraction in electron microscopy are discussed. A relationship between higher order Laue zone line width, probe size and specimen thickness is given, based on the uncertainty principle. Failure conditions of the column approximation for coherent convergent beam electron diffraction are tested by numerical simulations using the multislice method applied to a supercell containing a simulated strain field. The results and their implications are discussed. Phase determination of dynamical beams using overlapping orders is shown to require greater source coherence than that which is needed under single scattering conditions. The symmetry of coherent nanodiffraction patterns is shown to depend on probe position within a unit cell for all focus settings which fill the illumination aperture.
AB - The theory of coherent electron nanodiffraction from strained crystals is developed, based on the column approximation. Contributions to the diffraction pattern from different parts of the crystal under the illumination are considered, and a treatment of high-order weak reflections and diffuse scattering is given based on perturbation theory. Ultimate limits to the spatial resolution of coherent electron nanodiffraction in electron microscopy are discussed. A relationship between higher order Laue zone line width, probe size and specimen thickness is given, based on the uncertainty principle. Failure conditions of the column approximation for coherent convergent beam electron diffraction are tested by numerical simulations using the multislice method applied to a supercell containing a simulated strain field. The results and their implications are discussed. Phase determination of dynamical beams using overlapping orders is shown to require greater source coherence than that which is needed under single scattering conditions. The symmetry of coherent nanodiffraction patterns is shown to depend on probe position within a unit cell for all focus settings which fill the illumination aperture.
UR - http://www.scopus.com/inward/record.url?scp=21344494181&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=21344494181&partnerID=8YFLogxK
U2 - 10.1080/01418619308219387
DO - 10.1080/01418619308219387
M3 - Article
AN - SCOPUS:21344494181
SN - 0141-8610
VL - 68
SP - 1055
EP - 1078
JO - Philosophical Magazine A: Physics of Condensed Matter, Structure, Defects and Mechanical Properties
JF - Philosophical Magazine A: Physics of Condensed Matter, Structure, Defects and Mechanical Properties
IS - 5
ER -