Techniques for forming nanostructured materials are provided. In one aspect of the invention, a method for forming nanotubes on a buried insulator includes the steps of: forming one or more fins in a SOI layer of an SOI wafer, wherein the SOI wafer has a substrate separated from the SOI layer by the buried insulator; forming a SiGe layer on the fins; annealing the SiGe layer under conditions sufficient to drive-in Ge from the SiGe layer into the fins and form a SiGe shell completely surrounding each of the fins; and removing the fins selective to the SiGe shell, wherein the SiGe shell which remains forms the nanotubes on the buried insulator. A nanotube structure and method of forming a nanotube device are also provided.