A new epitaxial mechanism enables ultra-high quality Ag films on Cu substrates Shapes (Courtesy: Shutterstock/Olga Korneeva) It is straightforward to produce polycrystalline metal films on wafers but producing single ‑ crystal metal films is far more challenging. Because single crystals have no grain boundaries (the joints between differently oriented crystal regions in polycrystalline materials), they offer much better electrical performance: higher conductivity, lower resistive losses, improved high ‑ frequency behaviour (important for high ‑ speed communication and 5G), and reduced noise for quantum technologies. As a result, methods for reliably producing single ‑ crystal films are highly sought after.   Single ‑ crystal silver and copper films are particularly valuable. Silver is an exceptional conductor of both electricity and light, while copper provides excellent thermal management and reduces resistive heating.…