Lithographically patterned
nanowire electrodeposition (LPNE) is a new method for fabricating
polycrystalline metal nanowires using electrodeposition. In LPNE, a sacrificial
metal (M(1)=
silver or
nickel) layer, 5-100 nm in thickness, is first
vapor deposited onto a
glass, oxidized
silicon, or
Kapton polymer film. A (+)
photoresist (PR) layer is then deposited, photopatterned, and the exposed Ag or Ni is removed by wet etching. The etching duration is adjusted to produce an
undercut approximately 300 nm in width at the edges of the exposed PR. This
undercut produces a horizontal trench with a precisely defined height equal to the thickness of the M(1) layer. Within this trench, a
nanowire of
metal M(2) is electrodeposited (M(2)=
gold,
platinum,
palladium, or
bismuth). Finally the PR layer and M(1) layer are removed. The
nanowire height and width can be independently controlled down to minimum dimensions of 5 nm (h) and 11 nm (w), for example, in the case of
platinum. These
nanowires can be 1 cm in
total length. We measure the temperature-dependent resistance of 100 microm sections of Au and Pd wires in order to estimate an electrical grain size for comparison with measurements by
X-ray diffraction and
transmission electron microscopy.
Nanowire arrays can be postpatterned to produce two-dimensional arrays of
nanorods.
Nanowire patterns can also be overlaid one on top of another by repeating the LPNE process twice in succession to produce, for example, arrays of low-impedance, nanowire-nanowire junctions.
