EFFECT OF CONTAMINATION REACTIONS ON THE COMPOSITION AND MECHANICAL-PROPERTIES OF MAGNETRON SPUTTERED TIN COATINGS

The residual gas impurities in the atmosphere of a magnetron sputtering chamber are frequently concentrated enough to affect the composition of the coatings and their mechanical properties. By film deposition in an ultrahigh vacuum system with controlled residual gas pressure it can be demonstrated that only at O2 and H2O partial pressures below 10(-6) mbar can oxygen contamination of the coating be avoided. The reactivities of O2 and H2O are about ten times higher than that of N2 at the same partial pressure. The effects of impurities on data measured by scratch tests and by microhardness were studied. The first results on the determination of the adhesion strength of coatings by a fracture-mechanical shear test are presented. The problem of preparing samples with defined impurity content for the evaluation of the sensitivity and reliability of various testing methods and their systematic errors is discussed.