ABSTRACT
One of the most significant features of optical thin films is the way in which their properties and behaviour differ from those of identical materials in bulk form. This is, of course, also true for thin films in areas other than optics. Almost always, the performance of the film is poorer than that of the corresponding bulk material. Refractive index is usually lower, although, very occasionally, for some semiconductor materials it can be slightly higher, losses greater, durability less and stability inferior. There is also a sensitivity to deposition conditions, especially substrate temperature.
