Ballistic transport in nanodevices based on single-crystalline Cu thin film

In ballistic transport, the movement of charged carriers is essentially unimpeded by scattering events. In this limit, microscopic parameters such as crystal momentum, spin and quantum phases are well conserved, allowing electrons to maintain their quantum coherence over longer distances. Nanoscale materials, like carbon nanotubes, graphene, and nanowires, exhibit ballistic transport. However, their scalability in devices is significantly limited. While deposited metal films offer excellent scalability for nanodevices, achieving ballistic transport in these films poses a challenge due to their short electronic mean free path. Here, we investigated the electronic transport in cross-geometry devices fabricated with 90 nm-thick copper films without grain boundaries. We observed ballistic transport in devices with channel width smaller than 150 nm below 85 K by measuring negative bend resistance. Our findings would open the opportunity for probing intrinsic quantum properties of Cu, and for realizing scalable low-loss signal transmission and high-quality interconnects in semiconductor devices.