Atomic-Resolution Studies of Radiation-Induced Defects In High Conductivity Delafossite Oxide Metals

Delafossite metals are known for having the highest in-plane conductivity in the oxide family. Room temperature resistivity of PdCoO₂ is 2.6μΩ, and at low temperature it drops down to 0.0075μΩ, with a mean free path of 20μm. Such long mean free path raises the question of the nature of the defects – is the density truly that low, or are defects present but somehow hidden from scattering channels? Using scanning transmission electron microscopy (STEM) we deliberately introduced defects at a specific atomic plane of PdCoO₂ and PtCoO₂ using a high electron dose of 520×10^-3C/mm², then imaging at lower doses. Our results show that damage from an electron beam focused on the Pd (Pt) atomic layers creates local metallic chains and clusters. A beam placed on the O-Co-O layer damages more dramatically by cutting the Co layers off, resulting in Pd (Pt) layers to be pulled towards the neighboring Co layer position.