Diffusion processes in NiTi/Si, NiTi/SiO2 and NiTi/Si3N4 systems under annealing

We present a nanometric scale analysis of the NiTi/Si, NiTi/SiO2 and NiTi/Si3N4 systems before and after annealing at 500 deg. C during 30 min, by secondary ion mass spectrometry and electron-induced X-ray emission spectroscopy. Before annealing, a few nanometers thick transition layer forms at the interface of each system. Under annealing, a NiSi2 layer forms in the NiTi/Si system over several tens of nanometers, whereas a TiOx diffusion barrier builds up at the NiTi/SiO2 interface. A few nanometers thick mix layer composed of TiSi2, TiN and NiSi2 forms at the NiTi/Si3N4 interface. This interface presents an intermediate reactivity under annealing between that of NiTi/Si and NiTi/SiO2