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Recipients of 2014 Gjønnes Medal

[Steeds and Tanaka] John Steeds and Michiyoshi Tanaka receive the 2014 Gjønnes Medal.

John Steeds (UK) and Michiyoshi Tanaka (Japan) received the 2014 Gjønnes Medal for their outstanding contributions to convergent-beam electron diffraction that has revolutionized electron crystallography. The work of Steeds, Tanaka and colleagues at Bristol and Sendai has had a major impact on the design of transmission electron microscopes. Steeds was a pioneer of dislocation imaging and wrote a monograph on the anisotropic elasticity theory of dislocations.

In his lecture entitled 'A Convergence of Beauty and Utility', Steeds highlighted his involvement in the development of the technique of CBED. This work had a crucial role in placing convergent-beam electron diffraction (CBED) on a firm experimental and theoretical footing. He analyzed Bloch wave propagation through crystalline material and interpretation of CBED patterns. Technical advances in EM provide the ability to form small convergent electron probes that have allowed exploration of the symmetry of patterns and their relationship to crystal symmetry, as detailed in the 'Buxton Tables'. CBED became a technique that is widely used for lattice parameter determination, strain determination and point and space group determination, and for the evaluation of charge-density distributions at a sub-atomic level. CBED is now used by almost all electron microscopists who study materials. Steeds pioneered the use of TEM as a versatile and controlled way to introduce point defects into wide band gap semiconductors.

Elena Orlova