Sputter deposited Ni–Ti thin films on polyimide substrate

In this paper, we report on the feasibility of depositing Ni–Ti, with Ni-rich composition, thin films at 450 °C on polyimide. The films were magnetron co-sputter deposited from Ni–Ti and Ti targets on to three different substrate types: a) polyimide (PI) foils, b) SiO2/Si and c) PI spin coated Si wafers. The crystal structure, surface morphology and microstructure were studied using X-ray diffraction, atomic force microscopy and transmission electron microscopy. A difference in thin film growth mode was observed depending on the substrate. Ni–Ti films deposited on polyimide foil did not show any phase transformation upon thermal cycling. Ni–Ti films deposited on polyimide spin coated wafers showed the expected phase transformation upon thermal cycling.

► Crystalline Ni–Ti films have been deposited on polyimide (PI).
► The grain size of Ni–Ti on PI is extremely fine, compared to Ni–Ti on SiO2/Si.
► Ni–Ti deposited on wafers spin coated with PI exhibit thermoelastic transformation.