3. Single layer deposited on a substrate

Let's take a look at the reflectivity curve when the substrate surface is coated with a thin film. The latter may, for example, have been deposited by evaporation or formed by chemical reaction.

In this case, after the zone of total reflection, oscillations are observed in the descent of the reflectivity curve. These oscillations, known as Kiessig bangs , are the result of interference between two waves: that reflected by the air-thin-film interface and that reflected by the thin-film-substrate interface. The contrast of the bangs depends on the relative intensity of the two waves, i.e. the respective index of the two materials and hence their relative absorption. The period of the oscillations depends...