Application of micro-cantilevers in characterization of crystallization-induced stresses and mechanical properties of amorphous thin films

Abstract

Micro-fabricated cantilevers were used to investigate the stresses and density changes upon crystallization in thin films of amorphous metals and chalcogenide phase-change materials. In the study of amorphous Ge2Sb2Te5 thin films (the chacolgenide phase-change material), we found that the crystallization-induced stresses in phase-change materials are a function of the film thickness and whether or not the phase-change material was covered with a capping layer. In the study of amorphous Cu-Zr and Zr-Cu-Al thin films, combining the cantilever platform with a combinatorial deposition approach, we found a clear correlation between the glass-forming ability and the density change upon crystallization. Peaks in the density change were found to correlate with specific maxima in the critical thickness for glass formation. Using cantilevers of the same design, the Young?s modulus and the thermal expansion coefficients of amorphous Cu-Zr films were also measured. This new experimental methodology allows fast screening of material properties over large composition ranges with high compositional resolution, and thus has the potential of significantly accelerating the development of advanced materials with desired properties. In addition, the discovery of a correlation between sharp changes in the density change on crystallization and glass-forming ability in metallic alloys provides a new approach to rapid alloy development as well as new insight into the fundamental characteristics of alloys that most readily form glasses.