For my application, I want to electroplate a metal onto a
non-conductor at a thickness of less than 100 nanometers - a few tens
of nanometers thickness would be ideal.
My purpose is to create very thin conducting wires so copper,
aluminum, nickel would all be acceptable. Since I want these to act as
wires they should be approximately the same width as depth and
centimeters long. They are allowed to be rectangular rather than
cylindrical in cross-section.
Ideally, I would like to be able peel these off the substrate but I
may be able to use them on the substrate as long as the substrate is
non-conducting. Actually, I've read that it is much easier to deposit
onto a conducting substrate but if done this way it would be important
to be able to peel the wires off the substrate since for my application
it is essential that the conducting material be less than 100
nanometers in diameter.
One more requirement: it has to be doable at the amateur and low cost
level, that is without the facilities of an industrial or university
Is this achievable?
Electroplating is most easily performed if the substrate is
conducting. Could you first make a non-conducting substrate conducting
by passing a high voltage through it to exceed its breakdown voltage?
With gases exceeding the breakdown voltage produces a highly ionized
plasma. To electroplate onto a substrate you want it to retain its
solid form. Could this be achieved while exceeding its breakdown
voltage or would it also become a plasma gas?
Alternatively, a non-conductor can be electrostatically charged by
rubbing with a wool or silk cloth. If it is negatively charged then
there are an excess of electrons attached to the atoms near the
surface. Could these electrons be made to flow as a current if a
voltage source was applied?
There are established techniques for doing this job, including evaporation of
semiconductor-manufacturing steps, and printing with conducting ink. I doubt
can be done well without the right equipment.
As for peeling the fine wires off, remember that they will be delicate.
You might try electroless plating. Much better results
when dealing with non-conductors. :-)
What's wrong with silver? Electroless deposition of silver
is widely used for mirrors. It can even be applied as a spray,
for example to plate glass windows in storefronts.
How about hollow tubes?
100 nm? That is indeed quite small. It may be easier to find
a conducting molecule of that size. Perhaps the graphite fibrils
from Hyperion Catalysis
Electroless plating is easy -- nothing but chemicals and beakers.
Watch out for the explosion hazard if you use silver. Copper
is also a well-developed technology, used for plated-thru holes
in circuit boards.
You might also consider depositing a conductive seed layer
prior to conventional electroplating. This is commonly done
with palladium or carbon, however carbon might be too
lumpy to meet your thickness requirement. A palladium seed
layer by itself might be thick enough. Here's a review of
It is possible to evaporate or sputter thin metalic film on an insulating
substrate. For example, I routinely evaporate 10nm thick Chromium on glass,
it is used as an adhesion layer for a 1um thick (copper or gold) microstrip
transmission line. This issue you will have is with the width of the lines.
The cost goes up as the smallest feature goes down. You will need a fab. If
you don't want to use industry or a university then you will need to build a
fab in your garage.
The electroplating is not a real problem. Either Ni or Cu can easily
be done by an amateur, maybe even gold could be done. The normal way to
do this would be to vapor deposit gold onto an Si wafer (or onto float
glass) about 10 nm thick, spin coat with PMMA resist, photolithographic
patterning, etch away the pattern of the wires then electroplate the
wires. The gold would be the release layer.
For an amateur, hmmmm............
You might try getting an old inkjet cartridge, filling it with Aquadag
carbon based conducting paint and then printing the finest lines you
can, still, 100 nm is .1 micron......then electroplating.
Another method, buy some ultra-thin Al foil from Goodfellow (kinda
expensive), sandwich it between two pieces of glass, seal all but one
edge, lap this edge with ultra-fine abrasive just prior to
electroplating so that you have exposed a fresh layer of Al,
electroplate for 6 min at 10 amp/sq ft (nickel sulfamate bath) to get
your .1 micron. Take out your Al foil and put it in sodium hydroxide
to dissolve the Al but leaving the Ni wire along the edge.
Most of the time when people want ultra-thin foils, they vapor deposit
them onto substrates coated with a soap film. Carbon "stripper foils"
for accelerator targets are made this way to a thickness of 10
ANGSTROMS believe it or not about 5mm diameter free standing on an Al
support with a hole in the middle. I have done this and it isnt too
hard with a vapor deposition system.
If you can think of a way to pattern your wires, all electron
microscope labs (universities etc.) have either carbon coaters or gold
sputter coaters for sample prep and these cost nothing to run so they
might do this for you.
I think a project like this is doable even by an amateur but am not
exactly sure how yet.
Bob, you received a whole set of good suggestion
form a bunch of posters.
Here is different, additional approach, that may solve
the "peel off" problem and provide you with a great
abundance of specimens to experiment with, namely
fishing "metal whiskers" out of an aqueous solution.
Google for it and see whether you can get a recipe for it.
Post also into sci.chem.electrochem. Those dudes
do run across such "metal whiskers" as a nuisance
particularly with Sn & Cu.
Somebody suggested electroless deposition. Either electrolytic or
electroless may work, however, I find the chemicals for electroplating
to be much "nicer" than for electroless. However, electroless has the
ability to plate deep down into pores and into slots whereas
electroplating may not be able to get down into deep structures. I do
not think this is a problem for you.
Another possibility is to electroplate (or electroless) onto thin
carbon fibers. I've done this but have no idea of the fiber size as it
was an accident when I did it.
Another possibility is "silvering" using the method that was long ago
used to silver mirrors which deposits a thin layer of silver onto
glass. This can easily be done by amateurs and is discussed in old
copies of Amateur Telescope Making or in How to Make a Telescope by
Jean Texereau. You would coat silver onto thin whiskers of some
non-conducting material or onto a patterned substrate.
Electroplated nickel does not stick to stainless steel so you might use
stainless as a substrate so your wires will release easily.
Gold will not stick well to glass or Si wafers so you can deposit a
little of it and use it as a release layer.
Copper will not stick well to glass so you might use it as a release
layer and wire material.
If you can get an electron microscope lab to deposit a thin layer of
carbon with their specimen coating system, it will coat the entire
thing all around and then you can electroplate onto it. Carbon also
makes a good release layer. Since the carbon coats all around, you can
actually coat individual salt crystals and then dissolve the salt
leaving little hollow cubes, its like magic.
OK, HERE IS HOW TO DO IT, just thought of this.
Coat pieces of glass with the previously mentioned silvering process.
Stack them on top of each other with edges exposed. Electroplate for
desired time (I say 6 minutes ) and then seperate the stack. Dissolve
the silver leaving the Ni wires. With many pieces of glass stacked,
say microscope slides, you will get many samples. All of this can be
done easily by an amateur.
If I'm understanding your suggestion correctly wouldn't this leave
nickel plate with a width that is the thickness of the glass slides?
Or perhaps you mean only coat a single side of each glass slide with
silver while pressing an edge of the glass slide firmly against a hard,
flat surface so this edge gets no silver coating. The sides covered by
the silver are the ones pressed together. Apply nickel electroplate to
an edge of the stuck-together glass slides. Then the nickel will only
adhere to the conducting silver between the slides.
There are high quality optical glass plates available that are flat at
the nanoscale. Then the separation between the glass slides will only
be nanometers, so this will form a nanometers wide nickel plating
between the slides. So now you dissolve the silver and separate the
What do you suggest for dissolving the silver?
If you only need a few, how about using wire that have already been created
on a silicon chip? Larger chips will have long straight runs insulated from
the layers below and I think that more recent ones are on the scale you
want. If you need to separate the wires from the chip you might have
problems, but maybe you could electroplate something like gold onto them and
then dissolve them away to release the gold?