The metastable Al-Zr alloy thin films prepared by alternate sputtering deposition

Al-Zr alloy thin films are prepared via alternate sputtering deposition. The as prepared films exhibit metastable phases including amorphous, cubic ZrAl3(L12), supersaturated Al-in-Zr close-packed hexagonal structures, and Zr-in-Al face-centered cubic solid solutions with uniform composition distribution. The amorphous phase occurs in the compositions ranging from 16.8 to 69.9 at. % Al. The formation of amorphous structure is considered to follow the mechanism of solid state reaction amorphization or surface diffusion induced mixing. Additionally, the formation of a metastable cubic ZrAl3 intermetallic compound is attributed to its low nucleation energy barrier with respect to the stable tetragonal ZrAl3 (DO23). The heat of crystallization of the amorphous phase is also measured to investigate the metastability of the amorphous phase.