Study of processes at helium ion bombardment of thin silver films

Thin silver films (700 to 1000 A thick) were bombarded by He+ ions (energy 7 to 10 keV, current density 0.1 μA/cm2) at the temperature range 288 to 725 K. During the bombardment an increase of a specific film resistance was measured. With the help of transmission electron microscopy a formation of helium bubbles in the films with embedded helium particles was observed. By means of a total evaporation of films in high vacuum the implantation coefficient was determined. The value of the film specific resistance at the given time of bombardment is determined by an accumulation of the point defects of the implantation type, a release of helium into vacuum and by the formation of helium bubbles. Activation energies of gas release and growth of helium bubbles were determined. They turned out to be equal to 0.1 and 0.25 eV. (author)