Integration Technologies for Single-Crystalline NiMnGa Films

Fadila Khelfaoui 1Manfred Kohl 1Jörg Buschbeck 2Michael Thomas 2Oleg Heczko 2Sebastian Fähler 2Ludwig Schultz 2

1. Forschungszentrum Karlsruhe, IMT, Postfach 3640, Karlsruhe 76021, Germany
2. Leibniz-Institute for Solid State and Materials Research, P.O.Box 270116, Dresden D-01171, Germany

Abstract

The implementation of the giant magneto-strain effect of ferromagnetic shape memory alloys (FSMAs) in microactuators requires novel single crystalline thin films with bulk-like intrinsic properties and microsystems-compatible integration technologies. In this paper, Ni-Mn-Ga films epitaxially grown on heated substrates by DC magnetron sputtering are examined. The films are martensitic and ferromagnetic at room temperature and thus fulfill basic requirements for applications. For a detailed analysis of the martensitic transformation temperature-dependent X-ray diffraction measurements are performed, which are discussed together with orientation-dependent magnetization and electrical resistance measurements.

Technologies for micromachining and integration of free-standing epitaxial NiMnGa films are developed to investigate magnetic-field and stress-dependent reorientation effects of the martensitic variants. In order to obtain free-standing films, the options of peeling the film off the substrate and of using a Cr buffer layer and chemical release have been pursued. The process of micromachining requires an etchant-resistive substrate. For this purpose, the thin film is bonded to an alumina substrate covered by an adhesive coating. The adhesive coating is selected to provide sufficient bonding strength during processing and to use it as a sacrificial layer later on. A transfer bonding process is developed allowing the integration of micromachined NiMnGa components to a target substrate. For electrical interconnection, the technologies of laser welding and gap welding are investigated.

 

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Presentation: Oral at E-MRS Fall Meeting 2007, Symposium E, by Fadila Khelfaoui
See On-line Journal of E-MRS Fall Meeting 2007

Submitted: 2007-05-14 14:24
Revised:   2009-06-07 00:44