Thin-film growth by deposition from a liquid surface is among the earliest and most practical of the various
bottom-up techniques developed for making nanomaterials. It involves introducing atoms or molecules of the
desired material to a liquid surface to create a thin film that can then be redeposited and used as a material
with an orderly structure.
A drop of oil spilled on water will, for example, spread out to create a film that will appear rainbow-colored
depending on the angle viewed. This film has a thickness of only one or two molecules (and is known as a monomolecular
film). When the molecules spread over the water have a certain
affinity for water, they tend to display a uniform three-dimensional orientation. If they can be lifted whole
off the water surface, they can be used to make materials with a uniform three-dimensional molecular structure.
Perhaps the best-known such films are Langmuir Blodgett (LB) films,
which have been studied in depth now for close to eighty years.
LB films are created by depositing the raw material of the film to be made on the surface of water or some other
liquid so that it creates a monomolecular film. This can then be transferred to a solid substrate, such as glass,
by bringing the substrate into contact with the film, and then lifting it out.
Because the molecules self-assemble into a specific structure, the film created on the substrate is not only
very thin but also boasts a uniform structure. Traditional LB film manufacture exploits the differences in ease
of bonding between water, the raw material of the film, and a glass substrate. The structure of the resulting
film can be controlled by the way the glass is dipped in the water to lift the film from the water surface.
There are various other techniques that utilize thin film growth, and while they may require clean rooms and
other conditions, they can all be carried out with very simple equipment.
