In order to predict the behaviour of thin barrier layers, the equations governing diffusion must be known. From these, models based on the composition of such layers or their build-up can be developed. Using low pressure RF plasmas, even pressure- and temperature-sensitive substrates can be coated. Such coatings range in thickness from a few nanometres to a few microns The precursors used were hexamethyldisiloxane, oxygen and nitrogen. The coatings themselves can be tailored in terms of their transparency, flexibility, stability, adhesion and diffusion properties.