Shape memory NiTi thin films deposited at low temperature

NiTi shape memory alloy (SMA) thin films have the potential to become high performance actuators for micro-electromechanical systems. Low temperature crystallized NiTi films would ensure a good compatibility with microelectro nic processes and polymers. To avoid the drawbacks induced by annealing, we have tried to obtain low temperature crystallized RF sputtered NiTi films by optimising deposition parameters. We have found that NiTi films containi ng an excess of Ti (similar to 52%) were crystallized when deposited on Si( 100) substrates heated up to only 473 K. NiTi/Si(n) Schottky diodes I-V cha racteristics showed a temperature dependence indicating structural transiti on in the NiTi electrode. By depositing this type of NiTi films on polymide substrates, we obtained bimorph micro-actuators exhibiting a memory effect . (C) 1999 Elsevier Science S.A. All rights reserved.