Three-dimensional fabrication of free-standing epitaxial semiconductor nanostructures obtained by focused ion beam

We target the nanofabrication of free-standing nanostructures made of epitaxial semiconductor material layers of high crystallinity quality and high heterostructure complexity for optical applications at the nanoscale. Here we demonstrate the fabrication method in the case of epitaxial germanium grown on a silicon substrate but the method can be applied to any heterostructure material. The nanostructures are fabricated out of planar epitaxial wafers in the form of pillars with arbitrary section and high aspect ratio by electron-beam lithography and deep reactive-ion etching. The patterned SiGe structures are then released by focused ion-beam milling of the pillar base. In this way, they become free-standing and can be relocated on a suitable substrate by using a nanomanipulator. Microscopic characterizations are ongoing to verify that the high crystal quality typical of epitaxial layers grown on a large-area substrate is preserved throughout the different fabrication steps.