Atomic Layer Deposition (ALD) involves the deposition of materials one atomic monolayer at a time. It forms extremely uniform, conformal, pin-hole-free coatings even on high-aspect-ratio structures. This is achieved by pulsing a chemical precursor onto a hydroxylated substrate surface which reacts, resulting in a monolayer of material to be formed. The unused precursor is purged from the chamber and then the surface is again hydroxylated with water vapour or oxygen, followed by another purge. These steps are then repeated until the desired thickness of material is achieved.

ALD has a vast array of applications from semiconductors, MEMS, nanostructures and optics through to wear-resistant coatings.