David Cockayne had a wide-ranging and lasting impact on electron microscopy in materials science. He had dual UK and Australian nationality, and his professional career was divided between the two countries. His research was exceptional. His most important scientific contribution was the development (with I. L. F. Ray and M. J. Whelan in Oxford) of the dark-field ‘weak-beam’ technique of transmission electron microscopy, which improved by an order of magnitude (to 1.5 nm) the resolution at which complex crystal lattice defect geometries could be studied. The technique had a significant impact on advancing our understanding of the structure and properties of lattice defects in many materials, and became established as a routine tool in laboratories all over the world; it is still widely used today. With D. R. McKenzie in Sydney he developed a powerful high-precision electron diffraction technique within an electron microscope to study small volumes of amorphous material, orders of magnitude smaller than is possible with X-rays or neutrons, giving nearest-neighbour distances accurate to 0.001 nm. As Director of the University of Sydney Electron Microscope Unit from 1974 to 1999, he led the development of the Unit to provide a first-class centralized service of electron microscopy for the university as a whole. This stimulated other Australian universities to follow his example.
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Published by the Royal Society