X-ray diffraction studies during magnetron co-sputtering of Ni-Ti shape memory alloy films

The study of Ni-Ti shape memory alloy films is of great technological interest for applications in the field of microengineering. They can work as sensors and actuators at the same time. However, there are still important issues unresolved like formation of film crystallographic orientation and its control. Films exhibiting the two-way shape memory effect are also required. A two-magnetron sputter deposition chamber mounted into the six-circle diffractometer of the Rossendorf Beamline at the European Synchrotron Radiation Facility was used for the processing of Ni-Ti films. The in-situ x-ray diffraction studies enabled to identify the different steps of the structural evolution during film growth. Deposition conditions leading to Ni-Ti films mainly containing grains with (100) or (110) planes of the B2 phase parallel to the film surface were successfully defined. This is an important achievement since texture has a strong influence on the extent of the strain recovery. The deposition of films with a "two-way" actuation (films with a combination of superelasticity and shape memory characteristics) was also achieved. It will allow the development of smaller devices since no consideration has to be paid to a resetting spring.