Distinguished for his contributions to the development of electron microscopy and its applications to Materials Science. He developed the theory, and with Ray the experimental procedures for the "weak beam" technique, which improved by an order of magnitude, to 1.5nm, the resolution at which complex lattice defect geometries could be studied. The technique has led to important advances in understanding of the structure and properties of defects, and is now a routine tool. Cockayne's papers in this field are classic. He applied the technique inter alia to measure accurate values of stacking fault energies, demonstrated unambiguously for the first time that dislocations in semiconductors are dissociated, whether stationary or gliding, and elucidated the structure and positions of misfit dislocations in strained layer superlattices. He has made important contributions to the interpretation of lattice fringes. Following earlier work by Grigson, with McKenzie he developed a powerful electron diffraction technique for determining radial distribution functions from small areas of amorphous materials, collecting only elastically scattered electrons, transforming the method into a precision tool giving nearest neighbour distances accurate to 0.01A. Applications include the demonstration of the existence of the amorphous form of tetrahedrally coordinated carbon, and the refinement of models for C60 and C70. Cockayne's work is remarkable for his deep physical insight, and his ability to apply this insight to the development of powerful and widely applicable techniques.
^Lobo, C.; Leon, R.; Marcinkevic̆ius, S.; Yang, W.; Sercel, P. C.; Liao, X. Z.; Zou, J.; Cockayne, D. J. H. (1999). "Inhibited carrier transfer in ensembles of isolated quantum dots". Physical Review B60 (24): 16647–16651. doi:10.1103/PhysRevB.60.16647. ISSN0163-1829.
^Ray, I. L. F.; Crawford, R. C.; Cockayne, D. J. H. (1970). "The weak-beam technique applied to superlattice dislocations in an iron—aluminium alloy". Philosophical Magazine21 (173): 1027–1032. doi:10.1080/14786437008238488. ISSN0031-8086.
^Leon, R.; Kim, Yong; Jagadish, C.; Gal, M.; Zou, J.; Cockayne, D. J. H. (1996). "Effects of interdiffusion on the luminescence of InGaAs/GaAs quantum dots". Applied Physics Letters69 (13): 1888. doi:10.1063/1.117467. ISSN0003-6951.