Top-down SiGe nanostructures on Ge membranes realized by e-beam lithography and wet etching

SiGe nanostructures on Ge membranes have been fabricated by electron beam lithography and anisotropic wet-chemical etching, starting from SiGe/Ge heterostructures epitaxially deposited on Si substrates. Two different top-down approaches have been studied in order to obtain the best freestanding structures. We find that the process in which the Ge membrane is suspended after the lithography of the SiGe nanostructures leads to high quality SiGe nanostructures without damage to either the SiGe nanostructures or the Ge membrane. The structures have been systematically analyzed at every step of the fabrication process, by scanning electron microscopy and by atomic force microscopy.