Stabilizing nanocrystalline materials with dopants

The enhancement of material properties caused by extremely small grain sizes in metals and ceramics is attractive for many technological applications including protective coatings, electronic interconnects and microelectromechanical systems (MEMS) devices. However, the large driving force for grain growth caused by the abundance of grain boundaries remains a critical complication in the synthesis and functionality of nanocrystalline materials. Here we present atomistic simulations that illuminate the stabilizing effect of interfacially segregated, oversized dopants in face-centered cubic (fcc) copper. Using a bicrystal configuration, the calculated grain boundary energy is reduced to zero with systematically increasing dopant coverage and atomic radius mismatch. We then extend this result to a nanocrystalline network and determine the critical dopant concentration required to eliminate grain growth in bulk and thin film structures. The results of this investigation are intended to guide future experimental efforts to design appropriately doped, stable nanocrystalline materials.