Ballistic transport in nanodevices based on single-crystalline Cu thin films.

In ballistic transport, the movement of charged carriers remains unimpeded by scattering events. In this limit, microscopic parameters such as crystal momentum, spin and quantum phase are well conserved, allowing electrons to maintain their quantum coherence over longer distances. Nanoscale materials, such as carbon nanotubes, graphene, and nanowires, can exhibit ballistic transport. However, their scalability in devices is significantly limited. While deposited metal films offer scalability for nanodevices, their short electronic mean free paths hinder ballistic transport. In this study, we investigated the electronic transport in cross-geometry devices fabricated with 90-nm-thick Cu films without grain boundaries. We demonstrated ballistic transport in devices with channel widths of 150 nm at temperatures below 85 K via negative bend resistance measurements. Our findings establish a scalable platform for exploring the intrinsic quantum mechanical properties of Cu, advancing both the fundamental understanding of quantum transport in metals and its practical applications in next-generation electronic quantum technologies.