Atomic layer deposition (ALD) is a thin film preparation technique in which substances are deposited layer by layer on a substrate surface in the form of a monatomic film. During coating, two or more chemical vapor precursors react sequentially on the substrate surface to produce a solid film. The atomic-layer deposition system uses a crossflow reaction chamber through which an inert carrier gas is passed, into which the precursor is injected by a very short pulse. The inert carrier gas carries the precursor pulse as an ordered "wave" through the reaction chamber, the vacuum pump line, the filtration system, and finally through the vacuum pump. During atomic layer deposition, the chemical reaction of a new atomic film is directly associated with the previous one, in such a way that only one atom is deposited at a time.