Room-temperature plasticity in diamond

In spite of extremely high strength and hardness, the property of brittleness is tightly linked to diamond. In the deformation of diamond at room temperature, the plasticity of the diamond is normally considered hard to occur because of the domination of catastrophic brittle fracture. Herein, we employed in-situ transmission electron microscopy to reveal the diamond room-temperature plastic behavior, and compared it with a recent report (Adv. Mater. 2020, 1906458) on transformation-induced room-temperature plasticity of diamond nanopillars. Our present in-situ uniaxial compression tests in sub-micron-sized diamond pillars indicate that the plasticity in diamond is carried out by dislocations slipping instead of phase transformation and the initiation of plasticity highly depends on the stress state. On the other hand, we noted that a high proportion of amorphous surface layer in the diamond pillars with a diameter of less than 20 nm may be a significant factor leading to the plasticity.