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Atomic layer deposition, ALD

Coating process where a workpiece is sequentially coated by two different gasses in a heated vacuum container.

Illustration of Atomic layer deposition, ALD

The process

The workpiece is placed in a heated tank which is pumped out to a vacuum.

Two different carrier gasses mixed with various substances are linked to the container. One gas mixture is admitted, reacts with the workpiece surface [A] and is then pumped back out of the vacuum pump. Then the second base mixture is released into the chamber which then reacts with and builds on the previous coating | B]. Each alternating cycle that built the atomic layer on the surface and the number of cycles thus controls the thickness of the final coating.

The main difference between this method and the chemical vapor deposition is that the chemicals in this method are added sequentially and as a rule never exists simultaneously about the workpiece.