ADHESION OF SILVER FILMS TO ION-BOMBARDED SILICON-CARBIDE - ION-DOSE DEPENDENCE AND WEIBULL STATISTICAL-ANALYSIS OF PULL-TEST RESULTS

Silver films were deposited by evaporation onto polished silicon carbide substrates that had been sputtered for various lengths of time with 500 eV ions. The adhesion strength of the films was measured as a function of the ion bombardment time and species with a pull-type adhesion tester. Adhesion of Ag to argon-ion-sputtered surfaces was low except at the highest dose, in which case very good adhesion was measured. In contrast, oxygen/argon-ion sputtering produced a rapid rise in adhesion strength, but adhesion was limited to less than 60 MPa, even for lengthy bombardment. The applicability of Weibull statistical analysis to the distribution of pull-test failure strengths was investigated. A good fit of the data to the Weibull expression was observed. A significant Weibull threshold stress was found and the Weibull modulus was low.