Synthesis and characterization of Nb2AlC thin films

We report on the synthesis and characterization of epitaxial c-axis oriented Nb2AlC thin films deposited on c-axis sapphire (Al2O3) substrates by magnetron sputtering. Selected area electron diffraction reveal that independent of substrate temperature or film stoichiometry, there is the growth of a secondary phase not found in bulk, Nb5Al3Cx with a- and c-axis lattice constants of 7.746 Å and 5.246 Å, respectively. Scanning electron micrographs reveal large surface features, many with hexagonal shape and faceted texture. Atomic force microscopy topographical measurements indicate a surface roughness of approximately 15% of the total film thickness. Electrical transport measurements show typical metal-like conduction with a room temperature resistivity of ≈ 0.9 μΩ-m and a residual resistivity ratio of 2.5. A superconducting transition was found at ≈ 440 mK.