NiTi shape memory alloy thin films deposited by co-evaporation

Abstract

NiTi shape memory alloy thin films from separate evaporation sources are produced. One micron films with a gradient of Ni–Ti ratios are fabricated at temperatures of 200 °C with a deposition rate of 8.3 Å/s. A single e-beam evaporation system combined with a thermal evaporation source is used to create a co-evaporation process. The evaporation rate of the nickel in the evaporation source is allowed to develop a steady state, and then the e-beam evaporation of the titanium is controlled to maintain the correct rate and desired ratio. The resulting thin films that exhibit the two-way shape memory effect had approximately a 50% concentration of titanium as measured by energy dispersive spectroscopy (EDS).