Catalyst-free chemical vapor deposition of Ge wires from readily available precursors

A Review of Self-Seeded Germanium Nanowires: Synthesis, Growth Mechanisms and Potential Applications

“…Ge and C precipitates from the liquid droplet and a phase separation between Ge and C generate the Ge–C core shell nanowire structures. Similar growth mechanisms were suggested by several other groups for self-seeded Ge nanowire growth [ 147 , 148 , 150 ]. In these methods, the GeO 2 precursor was intentionally mixed with a hydrocarbon gas (methane, acetylene and ethanol, respectively) to obtain Ge–C core shell nanowires.…”

“…However, the nanorods produced showed a mixture of tetragonal, cubic and amorphous Ge structures, including a combination of these morphologies in single nanorods. GeO 2 has also been used as an alternative solid precursor, as it can be reduced in situ by H 2 at high reaction temperatures [ 147 , 148 ]. The crystallinity of the Ge nanowires produced can be tuned to be either amorphous, polycrystalline or single crystalline, by modifying the substrate temperature and/or evaporation rate.…”

“…An amorphous shell of between 1 and 7 nm in thickness was also observed on the surfaces of these nanowires. Other research groups also utilised GeO 2 as a precursor for growing Ge nanowires, combined with H 2 and various hydrocarbon molecules, e.g., methane, acetylene and ethanol, to achieve self-seeded core-shell 1D nanostructures (shells composed of carbon) [ 147 , 148 , 150 ]. These carbon-based self-seeded Ge nanowires were shown to be useful for energy storage applications such as anode materials for Li-ion batteries [ 147 , 148 , 150 ].…”

“…Other research groups also utilised GeO 2 as a precursor for growing Ge nanowires, combined with H 2 and various hydrocarbon molecules, e.g., methane, acetylene and ethanol, to achieve self-seeded core-shell 1D nanostructures (shells composed of carbon) [ 147 , 148 , 150 ]. These carbon-based self-seeded Ge nanowires were shown to be useful for energy storage applications such as anode materials for Li-ion batteries [ 147 , 148 , 150 ]. We have summarised and compared the current state of the art in the vapour-phase self-seeded growth of Ge nanowires in Table 1 .…”