Determination of the optical constants of tin oxide and silver thin films for their use in multilayer low-emissivity coatings.

The determination of the values of the optical constants (n, refractive ind ex and k, extinction coefficient) in the visible range of both silver (Ag) and tin oxide (SnO2) films is a necessary condition to predict the behaviou r of a SnO2/Ag/SnO2 multilayer for low emissivity coatings, improving the v isual comfort. For this purpose, thin films of Ag and SnO2 with a thickness similar to that of multilayer coatings (90 Angstrom and 380 Angstrom respe ctively) were used in order to avoid the thickness dependence of the optica l constants. A simulation computational program based on the matrix method was employed to estimate the values of the optical constants of these films in the visible range. It has been also determined the dependence on the wa velength of the absorption coefficient (alpha), as well as the value of the energy gay, and the nature of the optical transitions.