VISIBLE AND INFRARED ELLIPSOMETRY STUDY OF ION-ASSISTED SIO2-FILMS

Oxygen ion-assisted silica thin films are studied by means of in situ visible spectroscopic ellipsometry as well as infrared spectroscopic e llipsometry in air. It is well known that ion beam assistance leads to compacted material that does not adsorb atmospheric water vapour. Our aim is to study precisely the transition from porous evaporated films to compacted ones. We take into consideration here the refractive ind ex of the films under vacuum, their behaviour upon venting to the atmo sphere and a morphological model based on the association of IR and vi sible results. Expressing the ion assistance level in terms of the ave rage energy per molecule deposited at the surface by the ions, we dist inguish two compaction rates separated by a threshold energy value and corresponding to two different primary aspects of the compaction mech anism. (C) 1998 Elsevier Science S.A.