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