Preparation of heat treated Ni₂MnGa thin film without silicon diffusion

Abstract.

The Ni₂MnGa ferromagnetic alloys are one of these smart materials, that show a great interest for micro-electromechanical systems (MEMS) and micro-opto-electromechanical systems (MOEMS) when they are deposited as a thin film by rf sputtering. These films can be sputtered on silicon wafer in order to be easily integrated in Si-based device. Indeed, the use of this kind of substrate is very interesting because of the several well-known micromachining and integration technologies. However only heat treated thin films shows good functional properties that lay the problem of the silicon diffusion, as usually observed in the literature. In this work, a process (rf-sputtering process and annealing treatment) is proposed to elaborate martensite Ni₂MnGa thin films on Si substrate without silicon diffusion. This paper presents results on samples annealed at 873 K during 6 h.