Effect of RF sputtering parameters on the nanoscratch properties of quinary Ti-Zr-Cu-Ni-Al thin film metallic glass

Recently, thin film metallic glasses (TFMGs) gained renewed attention as they can circumvent the brittleness problem of bulk metallic glasses. When sputtered from a multicomponent cast target, the composition control of TFMG is always challenging. Here, we demonstrate the tight composition control of sputtered Ti-Zr-Cu-Ni-Al TFMG by a spark plasma sintered multicomponent target and investigate their structural and nanoscratch properties. The radio frequency (RF) power and Ar pressure were tuned to optimize nanoscratch properties. The highest hardness (~16.2 GPa) and thus best nanoscratch resistance was obtained at an RF power of 160 W and Ar pressure of 7 Pa. The best nanoscratch properties originated from the dense, fine column morphology of the TFMG. Moreover, it was found that the scratch mechanism changed from plowing to a combination of plowing and stick-slip under a ramping scratching load of 10 mN. The transition happened progressively at lower loads when the hardness of the TFMG decreased. This study provides a useful guideline for developing TFMG as a scratch-resistant protective coating.