Structures in textured Cu–Al–Ni shape memory thin films grown by sputtering

The structure and texture formation in Cu–Al–Ni thin films of different thicknesses (1μm to 5μm) grown by DC magnetron sputtering without any intentional heating of the substrate are reported. The as-grown films present grains with an average size of 20nm. The films with thickness of 1μm have a single metastable phase with a hexagonal structure and are textured with planes (0002) parallel to the plane of the films. It was observed that thicker films present phase coexistence between metastable hexagonal and body centered cubic structures with a gradual increment of the body centered cubic phase fraction. The films with thickness of 5μm are textured with planes (0002) and 101¯0 in the hexagonal structure, whereas in the body centered cubic structure the films are textured with {110} planes parallel to the plane of the films. This fact can be associated with self-heating of the substrate during the growth of the films and with the relative stability of the metastable phases. Free standing films annealed in a second step (1123K for 1h) present austenitic phase with L21 structure and sub-micrometric grains textured with {220}L21 planes parallel to the plane of the films. The martensitic transformation temperature was determined from the analysis of resistance against temperature measurements. •Cu–Al–Ni films grown by DC sputtering•Characterization by TEM of the microstructure in the as-grown and annealed films•Texture formation in austenitic films from metastable room temperature phases