Growth kinetics controlled rational synthesis of germanium nanotowers in chemical vapor deposition

This study demonstrated a simple method for gold (Au) catalyzed atmospheric pressure chemical vapor deposition (CVD) of tower-like germanium (Ge) nanostructures (denoted as Ge nanotowers) on silicon substrate. The Ge nanotowers have quasi- hexagonal cross-section with a diameter gradually decreasing from the bottom to the top end and sawtooth-faceted sidewalls. The Ge nanotowers are formed in a competitive growth process involving an Au-catalyzed axial growth and lateral growth, which can be controlled by the varied reagent vapor pressure in the CVD growth. The relationship between CVD growth kinetics and the complex morphologies was carefully examined for Ge nanostructures ranging from cylindrical and tapered nanowires to moniliform-shaped and sawtooth faceted hexagonal nanotowers in different deposition zones. The resultant complex Ge nanotowers not only enrich the family of Ge-based nanostructures, but also have potentials as building blocks for Ge-based functional nanodevices.