One-pot size-controlled growth of graphene-encapsulated germanium nanocrystals
Journal
Applied Surface Science (APPL SURFACE SCI)
Date
2018.01.31
Abstract
To realize graphene-encapsulated semiconductor nanocrystals (NCs), an additional graphene
coating process, which causes shape destruction and chemical contamination, has so far been
inevitable. We report herein one-pot growth of uniform graphene-germanium core-shell
nanocrystals (Ge@G NCs) in gram scale by the addition of methane as a carbon source
during the thermal pyrolysis of germane. The methane plays a critical role in the growth of
the graphene shell, as well as in the determination of the nucleation density and diameter of
the NCs, similar to a surfactant in the liquid-phase growth of monodisperse NCs. By
adjusting the gas ratio of precursors, a mixture of germane and methane, we can control the
size of the Ge@G NCs in the range of ~5 nm to ~180 nm. The Ge@G NCs were
characterized by various microscopic and spectroscopic tools, which indicated that the Ge
core is single crystalline, and is completely covered by the graphene shell. We further
investigated the merits of the graphene shell, which can enhance the electrical conductivity of
nanocrystalline materials.