INVESTIGATIONS ON THE REACTANT GAS-PRESSURE DEPENDENCE OF SPUTTERING YIELDS OF SEVERAL TRANSITION-METALS

Sputtering yields of polycrystalline samples of V, Co, Ni, Cu, Zn, Pd, Pt and Ag were investigated as a function of oxygen pressure from residual gas conditions (pO2 less-than-or-equal-to 0.002 mPa) to 6 mPa. Ar+ ions (2 keV; 35-mu-A/cm2; incidence angle theta = 45-degrees) were used for bombardment. Also sputtering yields of Fe, Nb and Ta were observed at residual gas conditions and for 2 mPa of O2 and for Ti, Cr and Cd under 2 mPa of O2. The sputtering yields were found to decrease with increasing oxygen pressure. This decrease is most pronounced for metals which are easily oxidized. Sputtering yields of V, Ni, Zn, Pd and Ag were also found to decrease under N2, N2O and NO. Using linear cascade theory the sputtering yields under oxygen were estimated and compared with experimental data. Satisfying correspondence was achieved, if different surface binding energies were assumed for clean and oxidized surfaces respectively.