Microstructural evolution in laser-ablation-deposited Fe-25 at.% Ge thin film

Abstract

Films with Fe-25 at.% Ge composition are deposited by the process of laser ablation on single crystal NaCl and Cu substrates at room temperature. Both the vapor and liquid droplets generated in this process are quenched on the substrate. The microstructures of the embedded droplets show size as well as composition dependence. The hierarchy of phase evolution from amorphous to body-centered cubic (bcc) DO₃ to has been observed as a function of size. Some of the medium-sized droplets also show direct formation of ordered DO₁₉ phase from the starting liquid. The evolution of disordered bcc structure in some of the droplets indicates disorder trapping during liquid to solid transformation. The microstructural evolution is analyzed on the basis of heat transfer mechanisms and continuous growth model in the solidifying droplets.