Formation of 3D-Cr$_2$(C$_{1-y}$O$_y$) at Cr$_2$AlC / AlO$_x$ interfaces

We report on the microstructural characterization of a multilayer AlO$_x$-Cr$_2$AlC thin film grown at 580 °C by direct current magnetron sputtering. Instead of stabilizing a two-dimensional carbide derivative, intentional periodic excess oxygen incorporation during thin film deposition leads to the formation of a 3D-Cr$_2$(C$_{1-}$$_y$O$_y$) phase within the AlO$_x$-Cr$_2$AlC multilayered film. The microstructure of the film was investigated by combining various imaging techniques in aberration corrected scanning transition electron microscopy. The distribution of C and related defects at atomic scale was revealed by the integrated differential phase contrast method.