Growth of elastically-stiff, nanostructured, high-entropy alloy nitride, (VNbTaMoW)N/Al2O3(0001) thin film

Abstract

Abstract We\xa0demonstrate the growth of 111-oriented, stoichiometric, B1-structured high-entropy alloy nitride (VNbTaMoW)N/Al2O3(0001) thin film via reactive magnetron sputtering and determine its elastic modulus E as 187±70 GPa using\xa0in situ\xa0buckling tests. Ab initio\xa0density functional theory calculations reveal that B1-MoN and B1-WN are structurally unstable, yet the nitride alloy with nearly equal fractions of parent nitrides is stable in B1 structure with E111 along [111] around 270 GPa. Interestingly, E111 values of the nitride alloys are higher than those expected from rule-of-mixture of all as well as the mechanically stable parent binary nitrides (B1- VN, NbN, and TaN). Our results suggest that cocktail effects, expected of high-entropy alloys, help not only stabilize a significant concentration of the unstable B1-WN and B1-MoN but also result in an enhanced stiffness of (VNbTaMoW)N.