On the amorphous nature of sputtered thin film alloys

Abstract

The power-law scaling behavior between the average interatomic distance and the atomic volume of sputter deposited Zr–Cu thin films has been compared with published data on Zr–Cu bulk metallic glasses. Despite the strong differences in the quench rate of the synthesis methods, the same scaling behavior is found which implies that the driving force for the alloy internal structure is the composition, not the magnitude of the quench rate. The validity of this statement was further tested for other nearly-equimolar multi-element alloy thin films deposited by magnetron sputter deposition. Binary, ternary, quaternary, and quinary alloys have been synthesized out of 5 base elements: Al, Cr, Cu, Ta, and Ti. Twenty-two (out of 26) thin films are XRD-amorphous. Based on the packing fraction of these alloys a subdivision can be made. Alloys with a high packing fraction follow the power-law scaling behavior for metallic glasses, whereas no clear correlation can be found for low packing fraction alloys. The thin film intrinsic stress for this latter group was substantially higher which shows that in the case of thin film deposition both composition and deposition conditions influence the internal structure of the amorphous alloys.