Phase formation of nanolaminated Mo2AuC and Mo2(Au1−xGax)2C by a substitutional reaction within Au-capped Mo2GaC and Mo2Ga2C thin films

Abstract

Au-containing nanolaminated carbides Mo₂AuC and Mo₂(Au_1−xGa_x)₂C were synthesized by a thermally induced substitutional reaction in Mo₂GaC and Mo₂Ga₂C, respectively. The Au substitution of the Ga layers in the structures was observed using cross-sectional high-resolution scanning transmission electron microscopy. Expansion of c lattice parameters was also observed in the Au-containing phases compared to the original phases. Energy dispersive spectroscopy detected residual Ga in Au-substituted layers of both phases with a peculiar Ga in-plane ordering for Au : Ga = 9 : 1 ratio along the Au–Ga layers in Mo₂(Au_1−xGa_x)₂C. These results indicate a generalization of the Au substitution reaction for the A elements in MAX phases.