Control composition study of sputtered NiTi shape memory alloy film

Since the transition temperature of the shape memory effect in NixTi1−x films depends on the composition of the layer, it is indispensable to have an accurate control on their composition. We are now able to control in situ the composition of r.f. sputtered NiTi films in the whole domain of shape memory effect (0.476 < x < 0.531), by varying the product of sputtering gas pressure P and target-to-substrate distance d. Pressure measurements are found to give a good sensitivity for the control of Ti-rich layers, while the optical emission spectroscopy of the sputtering plasma gives better sensitivity for Ni-rich layers.