Accurate prediction of size-dependent conductivity of PdCoO₂ thin films using size- and momentum-dependent mean free paths

Noble metals like copper have low bulk conductivity due to their long mean free paths. However, as modern CMOS devices and interconnects shrink in size, materials with long mean free paths tend to be disadvantaged because they suffer from more surface scattering. To address this issue, alternative materials with delafossite structures have been proposed. In particular, PdCoO₂, one of the delafossite materials, has a 2D-like Fermi surface due to its layered structure, resulting in in-plane conductivity comparable to that of noble metals. Several model approaches have been proposed to estimate the size-dependent conductivity, but since they are all based on experimental data fitting and a constant mean free path approximation, accurately predicting the conductivity of new materials as a function of device size remains a challenge. Here, we present a novel approach developed to predict size-dependent conductivity using momentum- and size-dependent relaxation times derived from momentum-dependent group velocities and size-dependent mean free paths. Our approach was able to accurately evaluatethe electrical properties of PdCoO₂ as well as other metal interconnects for different thicknesses. Due to strong anisotropy, PdCoO₂ films can be more conductive than copper when the thickness is less than 5 nm. Our findings suggest that anisotropic materials play an important role in device interconnects, opening up new possibilities for future electronic device applications.