Size-Dependent Grain Boundary Scattering in Topological Semimetals

TL;DR

This study demonstrates that topological semimetals CoSi and CoGe maintain surface state conduction even with grain boundaries, showing decreasing resistance with thinner films, unlike traditional metals, indicating potential for nano-interconnect applications.

Contribution

It reveals size-dependent grain boundary scattering effects in topological semimetals, highlighting their unique surface conduction properties in thin films.

Findings

Resistance decreases with decreasing film thickness in CoSi and CoGe.

Surface states dominate conduction despite grain boundaries.

Contrasts with conventional metals like Cu and Al.

Abstract

We assess the viability of topological semimetals for application in advanced interconnect technology, where conductor size is on the order of a few nanometers and grain boundaries are expected to be prevalent. We investigate the electron transport properties and grain boundary scattering in thin films of the topological semimetals CoSi and CoGe using first-principles calculations combined with the Non-Equilibrium Green's Function (NEGF) technique. Unlike conventional interconnect metals like Cu and Al, we find that CoSi and CoGe conduct primarily through topologically-protected surface states in thin film structures even in the presence of grain boundaries. The area-normalized resistance decreases with decreasing film thickness for CoSi and CoGe thin films both with and without grain boundaries; a trend opposite to that of the conventional metals Cu and Al. The surface-dominated transport mechanisms in thin films of topological semimetals with grain boundaries demonstrates a fundamentally new paradigm of the classical resistivity size-effect, and suggests that these materials may be promising candidates for applications as nano-interconnects where high electrical resistivity acts as a major bottleneck limiting semiconductor device performance.