REACTIVE PHASE-FORMATION IN SPUTTER-DEPOSITED NI AL MULTILAYER THIN-FILMS/

We have investigated reactive phase formation in magnetron sputter-dep osited Ni/Al multilayer films with a 1:3 molar ratio and various perio dicities, Lambda, ranging from 320 nm down to a codeposited film with zero effective periodicity. The films were studied by x-ray diffractio n, differential scanning calorimetry, electrical resistance measuremen ts, and transmission electron microscopy. We find that Ni and Al have reacted during deposition to form the B2 NiAl phase and an amorphous p hase. The formation of these phases substantially reduces the driving force for subsequent reactions and explains why nucleation kinetics be come important for these reactions. Depending on the periodicity, thes e reactions result in the formation of NiAl3 or Ni2Al9 followed by NiA l3. Detailed calorimetric analysis reveals differences in the nucleati on and growth behavior of NiA(l)3 compared with other studies.