Synthesis of Sn-catalyzed Ge nanowires and Ge/Si heterostructures via a gradient method

In this study, we investigate the growth of Ge nanowires (NWs) using a gas supply gradient method during plasma-enhanced chemical vapor deposition (PECVD), focusing on the effects of GeH₄ partial pressure and total chamber pressure on NWs morphology. By adjusting either the GeH₄ flow rate or the total pressure, we explored a gradient method to manipulate the growth process. Scanning electron microscopy (SEM) images revealed that, even with constant GeH₄ partial pressure, variations in total pressure significantly influenced NWs diameter and structure. Furthermore, elemental mapping and compositional analysis demonstrated the presence of a Ge/Si heterostructure with a Sn catalyst at the apex and an amorphous Si layer encapsulating the NW surface.