Straight single-crystalline germanium nanowires and their patterns grown on sol–gel prepared gold/silica substrates

Straight single-crystalline Ge nanowires with a uniform diameter distribution of 50–80 nm and lengths up to tens of micrometers were grown in a high yield on sol–gel prepared gold/silica substrates by using Ge powder as the Ge source. Detailed electron microscopy analyses show that the nanowires grow through a vapor–liquid–solid growth mechanism with gold nanoparticles located at the nanowire tips. By using transmission electron microscope grids as the shadow mask, the sol–gel technique can be readily adapted to prepare patterned film-like gold/silica substrates, so that regular micropatterns of Ge nanowires were obtained, which could facilitate the integration of Ge nanowires for characterization and devices.