Formation of 3D Cr₂C through solid state reaction-mediated Al extraction within Cr₂AlC/Cu thin films

We report on the formation of the Cr₂C compound using chemical etching-free methodology to extract Al from a Cr₂AlC MAX phase thin film. Cr₂AlC/Cu assemblies were deposited on sapphire substrates, using magnetron sputtering, and were subsequently annealed in vacuum. The Al from the MAX phase was shown to diffuse into Cu resulting in the formation of Al₄Cu₉ and causing the MAX phase to collapse into Cr₂C grains. These carbide grains were characterized by transmission electron microscopy and the interatomic distances extracted were in good agreement with ab initio calculations predicting the equilibrium volume of the Cr₂C phase.