Abstract
Sputter-deposited TiNi films had needed for a long time a post-annealing process (about 500°C) in order to have properties for shape memory alloy (SMA). A new deposition process, which incorporated simultaneous ion irradiation with multi-target RF magnetron sputtering, enabled to form crystalline TiNi films directly on a substrate at a temperature lower than 200°C. We have reported in our previous study that an SMA device was successfully fabricated on polyimide substrate without any thermal annealing. In this paper, we reveal how the energy of irradiating ion affects on lowering the optimum crystallization temperature of films. As a result, the threshold of ion energy at which crystallization comes out changes depending on plasma conditions, if the energy of irradiating ion determined only by the pulse bias voltage. However, when the energy of irradiating ion is corrected by adding the plasma potential to the bias voltage, it becomes almost constant.
