3. Early reaction: thin film formation

The surface of a solid is a very special zone, still largely unknown, and the subject of a great deal of research (physical chemistry of surfaces and interfaces): it is the site of solid-gas relations [13][14] . Gases can bind to the surface of solids (adsorption) or detach from them (desorption). It is generally accepted that all gases can bind to the surface of any solid by more or less complex mechanisms. This reversible attachment is known as physisorption. It is the first stage in solid/gas reactions.

The physisorbed molecules can then, under certain conditions, give rise to electronic exchanges with the solid. This step, called chemisorption, is a real chemical reaction that produces a new compound on...