Interface interactions in hybrid organosilane-nitride films on polymer substrates

Organic-inorganic hybrid coatings are becoming increasingly important due to their unique property combination [1, 2], including high optical transparency, improved scratch and abrasion resistance and excellent weathering, thanks to the synergism between the properties of the organic and inorganic components. The present study focuses on preparation and characterization of hybrid materials based on organosilane-modified silicon nitride films. Most of the studies of silane interaction with inorganic films have been limited to metal oxide surfaces [3, 4]. Transparent, inorganic silicon nitride (SiNx) thin films of various thicknesses were deposited by PECVD on polyimide substrates. A range of organosilanes with different amine functionality, and at different concentrations in ethanol were spin coated on the SiNx films and thermally cured at 80°C for 18 hrs. The silane coated SiNx films were characterized with Rutherford Backscattering Spectrometry (RBS), Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS) and X-ray Photoelectron Spectroscopy (XPS) with an aim of understanding the interactions between the organic and the inorganic layers. The results show the condensation of the aminosilane in contact with the nitride (hydrolyzed surface) layer. Interface formation mechanisms, including partial dissolution of the nitride and formation of cross-linked polysiloxane layer are also investigated.