From crystalline germanium-silicon axial heterostructures to silicon nanowire-nanotubes.

One-dimensional (1D) nanostructures have attracted considerable attention as a result of their exceptional properties and potential applications. Among them, 1D axial heterostructures with well-defined and controlled heterojunctions between different nanomaterials or between different 1D nanostructures (i.e., nanowire-nanotube heterojunctions) have recently become of particular interest as potential building blocks in future high-performance nano-optoelectronic and nanoelectronic devices. Here, we report on the preparation and characterization of crystalline silicon nanowire-nanotube (SiNW-NT) heterostructures with controlled geometry, kinked and unkinked, and composition using germanium-silicon nanowire heterostructures with abrupt heterojunctions (~2 nm wide) as a template via the VLS-CVD mechanism.