Size-Dependent Grain-Boundary Scattering in Topological Semimetals

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