Investigating phase regimes via combinatorial synthesis: A pathway to tailored materials libraries

Combinatorial magnetron sputtering has been implemented to synthesize compositionally graded thin film material libraries, enabling rapid exploration of structure–property trends via high-throughput characterization techniques. In this study, an Fe-W material library with 169 unique samples is sputter-deposited to investigate the amorphous-crystalline transition across the Fe – 9.4 to 45.5 at.% W range. X-ray diffraction and electron microscopy techniques reveal trends in film microstructure and morphology that are intrinsically connected to alloy composition but further shown to be dependent on synthesis conditions by decoupling composition and thickness/deposition rate effects. Samples are classified into three distinct regimes: crystalline, mixed-mode, or X-ray amorphous. By deconvoluting and analyzing the interplay between composition and deposition rate, it is shown that growth kinetics can sufficiently alter phase formation to dominate compositionally driven mechanisms within a single material library. This observation is verified after heat-treatment to 750 °C on selected samples. Particularly within the mixed-mode regime, the relationship between solute content and deposition rate is quantified, thereby enabling the tailoring of materials libraries investigations of composition and growth rate effects. Overall, this work combines the expansive compositional space in a combinatorial library with sputtering science to identify microstructural and phase regime boundaries in the Fe-W system.