Electronic excitation induced modifications of nanostructured Ni-Ti shape memory alloy thin films

In the present work, the effects of 120 MeV Au ion irradiation at different fluences ranging from 1×10 12 to 3×10 13 ions/cm 2 on structural and electrical properties of thin films of Nickel-titanium (Ni-Ti) shape memory alloys (SMAs) grown on Si substrate using DC magnetron co-sputtering is studied. The surface morphology, crystallization and phase transformation behaviour of these films were investigated using field emission scanning electron microscopy (FESEM), atomic force microscopy (AFM), X-ray diffraction (XRD) and Four-terminal resistivity measurement method. XRD pattern reveals that both the phases-martensite as well as austenite exist in the pristine film. Resistivity measurements revealed a two way transformation from cubic to rhombohedral and from rhombohedral to monoclinic phase in pristine film and decrease in its transformation temperature with increased fluence. At higher fluences 5×10 12 and 1×10 13 ions/cm 2 , films showed non-metallic behaviour which could be due to