Kinetics of Growth and Sorption Properties of Evaporable Barium Getter Films

Abstract

The evaporable getters (gas absorbing materials) are widely used in industry in all applications where it is necessary to
maintain required vacuum and to assure long lifetime of the operating systems through the sorption of undesired gases.
One of the main factors influencing gas sorption characteristics of such getter films is physico-chemical nature of their
surfaces. In this research the thin barium getter films have been prepared on glass substrates by thermal evaporation
method. Adsorption properties of evaporated barium films formed in the presence of reactive (O2) and inert (Ar) gas
atmospheres by means of in-situ and ex-situ measurement facilities were analysed. An overall view of the films in-situ
and ex-situ results shows that the best sorption performance of the Ba films was obtained when the Ba film was porous
(high vacuum cases) and short-time of evaporation was used. It was found that the sorption properties of particular
barium film depend on duration of evaporation process that should be considered together with the residual gas pressure
as a parameter influencing porosity of getter film. In conclusion it is evident that the process of barium evaporation must
be short-term and forced with respect to temperature, in order to obtain good sorption and structural characteristics of the
barium film.