Characterization of Free-Volume Properties of Surface and Interfaces in Thin Film Using Positron Annihilation Spectroscopy

Positron annihilation spectroscopy (PAS) is a special nondestructive evaluation (NDE) technique for materials characterization, which uses the positron (anti-electron) as a radio-analytical probe. This paper presents some of our recent results on the applications of positron annihilation lifetime spectroscopy and Doppler broadening energy spectroscopy coupled with a variable energy positron beam to characterize free-volume properties in nano-scale polymeric films. Depth profiles of glass transition temperature and layered structures in polystyrene thin films on the gold substrate are determined.