# Thickness dependence of the resistivity of Platinum group metal thin films

## TL;DR

This study investigates how the resistivity of platinum-group metal thin films varies with thickness, revealing that these metals can outperform copper at very thin scales due to weaker size effects, and models surface and grain boundary scattering effects.

## Contribution

It provides experimental data and modeling insights into the thickness-dependent resistivity of platinum-group metal thin films, highlighting the impact of surface and grain boundary scattering.

## Key findings

- Platinum-group metals have lower resistivity than Cu below 5 nm thickness.
- Surface scattering varies with interface material, being nearly specular with SiO2 or air.
- Resistivity dependence on mean free path is modeled using the Mayadas-Shatzkes framework.

## Abstract

We report on the thin film resistivity of several platinum-group metals (Ru, Pd, Ir, Pt). Platinum-group thin films show comparable or lower resistivities than Cu for film thicknesses below about 5\,nm due to a weaker thickness dependence of the resistivity. Based on experimentally determined mean linear distances between grain boundaries as well as ab initio calculations of the electron mean free path, the data for Ru, Ir, and Cu were modeled within the semiclassical Mayadas--Shatzkes model [Phys. Rev. B 1, 1382 (1970)] to assess the combined contributions of surface and grain boundary scattering to the resistivity. For Ru, the modeling results indicated that surface scattering was strongly dependent on the surrounding material with nearly specular scattering at interfaces with SiO2 or air but with diffuse scattering at interfaces with TaN. The dependence of the thin film resistivity on the mean free path is also discussed within the Mayadas--Shatzkes model in consideration of the experimental findings.