Tanaka Patterns
Large-Angle Convergent-Beam Diffraction
LACBED
The Tanaka Methods
• Traditional microscopy taught that the microscope should be focussed on the specimen or on the diffraction pattern in the back focal plane.
• Tanaka liberated us and gave rise to a family of new techniques by telling us to look in other places.
S p ec im e n S p ec im e n S p ec im e n
GaAs K. Christenson
GaAs [100] K. Christenson
M. Kaufman
Ni3Mo
Ni3Mo BF Tanaka pattern
S p ec im e n S p ec im e n S p ec im e n
Ni3Mo
Ni3Mo DF Tanaka pattern
Al layer on GaAs Tanaka Group
Defect Analysis
• Large-Angle Convergent-Beam patterns provide an alternative method of determining the Burgers vectors of dislocations. (And characterizing other defects.)
• The dislocations have to be well separated.
Fe,30Ni,19Cr [114] Cherns and Preston
Fe,30Ni,19Cr [114] Cherns and Preston
Fe,30Ni,19Cr [114] Cherns and Preston
Si Tanaka Group
g.b = n
g is the reciprocal lattice vector corresponding to the diffracting planes
b is the Burgers vector of the dislocation
n is the number of lines of no contrast