Combinatorial investigation of the mechanical properties of aluminum-silicon thin film nanocomposites

We have undertaken the exploration of Al_xSi_1−x material systems to discover new alloys with enhanced mechanical properties. Combinatorial methods were used to systematically control thin film microstructure through variations in composition and growth temperature. Discrete libraries of compositionally graded films have been sputter deposited onto silicon substrates to produce two structural phase regions: amorphous Al–Si and amorphous Si plus crystalline Al. The mechanical properties of the thin films were determined through indentation experiments by analyzing the load–displacement traces based on the Oliver–Pharr method. X-ray diffraction was used to investigate the microstructures and determine the crystallite sizes. In samples with an Al concentration near 55 at.%, the data show that decreasing the Al crystallite size by nearly one half increases the nanocomposite hardness by nearly a factor of two.