Molecular-based electronics represents a new class of devices which
can achieve 1) high-densities per chip; 2) truly three-dimensional
architecture; and 3) high-speed operation. In addition, such electronics may exhibit quantum-mechanical
phenomena, e.g.single-electron tunneling, at or near room
temperature which are applicable to logic devices.
Key to realizing molecular-based electronics is the fabrication of metallic
leads whose length scales are commensurate to the size of a single molecule
(~1 nm). Such leads are necessary to interface
and connect the molecules of interest. While efforts have been placed on
electron-beam and scanning-probe lithographies and self-assembled
structures, there has yet to be an appropriate method for achieving, with
precision and high-yield, such length scales in metallic nanostructures.
One promising strategy, however, is electrodeposition via aqueous
solutions, i.e. electroplating [1, 2].
Here, metallic ions in solution are deposited onto the leads via an
electrolytic chemical reaction. While successful in achieving nanometer
resolution, this particular technique is limited to solutions which must
contain the metal ions of interest and cannot be used to produce an
arbitrary deposition profile.
We have developed a more flexible variation of the electrodeposition
process. Unlike previous methods, ours employs an on-chip anode as
the metal source and utilizes microliter quantities of a solution that
initially does not contain the particular metal ion. The process can thus
deposit metals in situ, producing separations less than 10 nm.
Potential applications of our technique include nanofabrication processes
requiring a low-metal ion concentration, localized electrodeposition, and
the repair of damaged or malformed circuit interconnects in situ, the
latter of which is currently not possible with standard lithographic
techniques. The use of electrodeposited nanoscale electrodes as either
quantum point contacts or metallic leads for a molecular junction may have
potential applications in logic devices, both classical and quantum.