Dynamics of ion beam modification of polymer films

Thin polymer films were irradiated in a high vacuum environment with energetic (∼2 MeV) ions. The emitted molecular species were studied with a quadrupole mass spectrometer during bombardment. The emitted species are predominantly small molecules. The efficiency of emission depends strongly upon the electronic energy loss of the incident ions in the film and, hence, upon the velocity and atomic number of the incident ion. The emission efficiency of all species decreases with increasing damage in the film. By pulsing the ion beam, the time dependence of irradiation induced emission of molecular species from the films has been studied. Emission delays of hundreds of milliseconds are observed in some cases. These delays are found to depend upon the emitted species as well as the host film and seem to be associated with diffusion of the species in the films.