Magnetron sputtering of epitaxial Al5C3N thin films

Al 5 C 3 N has a nanolaminated crystal structure with layers of AlN separated by layers of Al 2 C and Al 2 C 2 . The physical and chemical properties of Al 5 C 3 N is more or less unknown due to the high temperatures required to synthesize bulk samples but in analogy with other nanolaminated materials such as MAX-phases, this compound may have potential applications as thin film materials. In this study we have deposited single-phase Al 5 C 3 N films with magnetron sputtering onto α-Al 2 O 3 (001) and AlN(001)/α-Al 2 O 3 (001) substrates at deposition temperatures ranging from 650 °C to 800 °C. The as-sputtered films were analyzed using multiple compositional and structural characterization methods. Epitaxial growth of Al 5 C 3 N was obtained on AlN(001)/α-Al 2 O 3 (001) but with a large number of defects mainly with extra stacking planes locally inserted into the structure. Nanoindentation measurements showed a hardness of about 18-19 GPa, which is significantly harder than for the MAX-phases. This can be explained by a high bond strength between the alternating AlN and Al 2 C/Al 2 C 2 layers giving this compound a more three-dimensional character than the MAX-phases. The band gap measurements show band gaps of 2.2 eV and 2.9 eV for the films deposited at 650 °C, and 1.8 eV and 2.5 eV for films deposited at 800 °C. • Al 5 C 3 N successfully synthesized as thin films, using reactive sputter deposition. • Epitaxial growth achieved at 800 °C using AlN(001)/α-Al 2 O 3 (001) substrate. • Band gap measured and determined to be in the range of 1.8 to 2.9 eV. • Films shows ceramic hardness of 18 to 19 GPa.