Direct Observation of Room-Temperature Dislocation Plasticity in Diamond

Summary It is well known that diamond does not deform plastically at room temperature and usually fails in catastrophic brittle fracture. Here, we demonstrate room-temperature dislocation plasticity in submicrometer-sized diamond pillars by in situ mechanical testing under the transmission electron microscope. We document in unprecedented details of spatiotemporal features of the dislocations introduced by the confinement-free compression, including dislocation generation and propagation. Atom-resolved observations with tomographic reconstructions show unequivocally that mixed-type dislocations with Burgers vectors of 1/2 are activated in the non-close-packed {001} planes of diamond under uniaxial compression of and directions, respectively, while being activated in the {111} planes under the directional loading, indicating orientation-dependent dislocation plasticity. These results provide new insights into the mechanical behavior of diamond and stimulate reconsideration of the basic deformation mechanism in diamond as well as in other brittle covalent crystals at low temperatures.