Rolled-up micro- and nanotubes from single-material thin films

The authors fabricate well-positioned and size-scalable semiconductor micro- and nanotubes from single-material layers. The tubes form when a partially strain-relaxed film, grown at low substrate temperatures, is released from the substrate by selective underetching. The layer rolls downwards or upwards depending on whether it is initially tensile or compressively strained. They create silicon and indium-gallium-arsenide tubes with diameters accurately tunable by varying the layer thickness. They draw a simple model to describe the mechanism responsible for the tube formation from a single-material thin film. Moreover, the tube diameters are shown to scale with strain and layer thickness.