Room-Temperature Epitaxial Electrodeposition of Single-Crystalline
Germanium Nanowires at the Wafer Scale from an Aqueous Solution
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Abstract
Direct
epitaxial growth of single-crystalline germanium
(Ge) nanowires
at room temperature has been performed through an electrodeposition
process on conductive wafers immersed in an aqueous bath. The crystal
growth is based on an electrochemical liquid–liquid–solid
(ec-LLS) process involving the electroreduction of dissolved GeO<sub>2</sub>(aq) in water at isolated liquid gallium (Ga) nanodroplet
electrodes resting on single-crystalline Ge or Si supports. Ge nanowires
were electrodeposited on the wafer scale (>10 cm<sup>2</sup>) using
only common glassware and a digital potentiostat. High-resolution
electron micrographs and electron diffraction patterns collected from
cross sections of individual substrate-nanowire contacts in addition
to scanning electron micrographs of the orientation of nanowires across
entire films on substrates with different crystalline orientations,
supported the notion of epitaxial nanowire growth. Energy dispersive
spectroscopic elemental mapping of single nanowires indicated the
Ga(l) nanodroplet remains affixed to the tip of the growing nanowire
throughout the nanowire electrodeposition process. Current–voltage
responses measured across many individual nanowires yielded reproducible
resistance values. The presented data cumulatively show epitaxial
growth of covalent group IV nanowires is possible from the reduction
of a dissolved oxide under purely benchtop conditions