Morphology control of self-catalyzed germanium nanostructures with graphitic carbon shell

Abstract: Crystalline germanium nanowires (GeNWs) with a uniform graphitic carbon shell were successfully prepared via a conventional low-pressure chemical vapor deposition (LPCVD) method without any external catalyst. The GeNWs grown at low temperature (Tg< 500 °C) have a uniform diameter with a large expect ratio, but the NW morphology is dramatically changed into a hybrid structure which highly dense Ge nanoparticles (GeNPs) with a diameter of 5？10 nm are attached on to the NW with increasing the temperature (Tg> 500 °C). They are not only closely connected with the NW body and the other NPs, but also consisted of a crystalline Ge-core and thin graphitic carbon shell. The possible anisotropic growth mechanism without metal catalyst and the controllable morphological transition of Ge nanostructures are discussed and demonstrated.