STUDY OF THE SILICON GAMMA-APS/PYRALIN ASSEMBLY INTERFACES BY X-RAY PHOTOELECTRON-SPECTROSCOPY/

Polyimides have been extensively studied in view of their wide industr ial applications. Adhesion to a substrate is essential for normal oper ation of devices. This problem is often solved by the use of an adhesi on promoter on the surface of interest. A surface-sensitive technique such as SPS has proved to be a powerful analytical tool for the analys is of the polymer/substrate interface, In the present paper, the inter faces of the SiO2/gamma-aminopropyltriethoxysilane (gamma-APS)/Pyralin system have been investigated at a precured stage. A detailed analysi s of the molecular structures formed at the interface is carried out u sing XPS spectroscopy. An attribution of the various peak components i s made with the help of accurate calculations of presumed core-electro n binding energies using a recent procedure based on the Density Funct ional Theory. Two acid-base mechanisms are described. The first one oc curs between the ammonium end of the gamma-APS molecule and the silico n surface hydroxyl (NH3+SiO-), whereas the second one is formed betwee n the ammonium end of the gamma-APS and the polymer carboxylic functio n (NH3+COO-). The results at the first interface are in contradiction with the expected stable oxygen-bridged bond (siloxane), thus the rear rangement of the gamma-APS molecule upon heating, as suggested by Lind e in a dynamic 'Flip model,' has been studied.