Molecular Layer Deposition

The proposed solution

Molecular Layer Deposition (MLD) is a vapour phase deposition technique for hybrid thin films based on successive self-limiting surface reactions. In several aspects, MLD resembles the now mainstream technique of Atomic Layer Deposition (ALD). However, where ALD is limited to exclusively inorganic coatings, the precursor chemistry in MLD is expanded to include organics and enables linking both types of building blocks together in a controlled way to build up organic-inorganic hybrid materials.

The figure below schematically shows an MLD process. First, the “inorganic” precursor is pulsed to the reactor and it reacts with the surface species. Once all adsorption sites have been consumed, no more precursor will react. The excess precursor and possible byproducts are removed from the reactor, either by purging with inert gas or by pumping. Next, the “organic” precursor is introduced, which reacts with the precursor molecules anchored to the surface. This surface reaction is again self-saturated, and is followed again by purging/pumping of the reactor. In an ideal case a monolayer of a hybrid inorganic–organic material is formed, and the layer is terminated with surface groups that can react with the “inorganic” precursor. Therefore, the MLD deposition cycle can be repeated, thereby building up hybrid films one layer at a time. The resulting process enables coatings with unparalleled conformality, thickness control and film quality while at the same time unlocking a spectrum of new materials.

MLD cycle