Sputter-deposited and ion-mixed NiTi and NiCr thin films

Abstract

In this work we have compared the microstructure of NiTi and NiCr films prepared by ion beam mixing as well as by r.f. sputter deposition at room temperature. Ion beam mixing of thin alternating layers of NiTi and NiCr was done by 350 keV Cr + ions at a dose of 2 × 10 16 cm −2. The thicknesses of individual layers were chosen to provide an overall composition of Ni 50Ti 50 and Ni 50Cr 50 after ion mixing. Homogeneous Ni 52Ti 48 and Ni 45Cr 55 films were also prepared by r.f. sputter deposition from composite targets. Amorphous NiTi was obtained by ion mixing as well as by r.f. sputtering while NiCr remained polycrystalline under similar processing conditions. These results are discussed in terms of existing empirical rules of amorphous phase formation.