Growth and properties of coherent twinning superlattice nanowires

Although coherent twin boundaries require little energy to form in nanoscale single crystals, their influence on properties can be dramatic. In recent years, some important steps forward have been made in understanding and controlling twinning processes at the nanoscale, making possible the fabrication of nanoengineered twinning superlattices in crystalline nanowires. These advances have opened new possibilities for properties and functionalities at the atomic and quantum scales by modulating twin densities. This article presents a brief overview of recent theoretical and experimental progress in growth mechanisms and promising properties of coherent twinning superlattice nanowires with special emphasis toward cubic systems in semiconductor and metallic materials. In particular, we show how nanoscale growth twins can considerably enhance bandgap engineering and mechanical behaviour in quasi-one-dimensional materials. Opportunities for future research in this emerging area are also discussed.