SPUTTERED ALLOY COATINGS BY CODEPOSITION - EFFECTS OF BIAS VOLTAGE

The structure of most sputtered refractory metal coatings produced at low substrate temperatures consists of columnar grains with open boundaries, owing to self-shadowing effects caused by the low adatom mobility. It was shown that self-shadowing effects can be reduced by depositing two metals with dissimilarly sized atoms. Within a certain composition range, an alloy of niobium and chromium produced coatings comprising a dense fine columnar grain structure. Further improvement in structure has been demonstrated by the application of a bias voltage to the substrate during deposition. At - 100 V bias, the packing density was enhanced and a coating containing a non-columnar grain structure was obtained. The improved performance due to this optimum structure was shown by thermal shock tests.