Ion beam mixing of Ni/Al multilayer structure at different temperatures

Abstract

A multilayer structure composed of 10 sputter-deposited alternating Ni and Al thin films with an average composition of Ni 0.50Al 0.50 was ion mixed at different temperatures between −145°C and +430°C. Ion mixing of Ni/Al multilayers was performed in an implanter using 350 keV Ar ions at a dose of 1×10 16 ions cm −2. The ion range of about 180 nm was estimated with the TRIM 95 computer code. The as-deposited and ion-mixed specimens were characterized by Auger electron spectroscopy (AES) depth profiling. The AES depth profiles of the ion- and heat-treated Ni/Al multilayer structures allowed a quantitative determination of interface widths which indicated different migration lengths of atoms at the interfaces in the early stage of the mixing process. Generally, the effect of ion beam mixing increased with increasing temperature. Extended X-ray absorption fine structure spectroscopy (EXAFS) revealed the presence of the NiAl phase in the samples ion mixed at temperatures of 280 and 330°C. In the sample treated at 430°C, the AES has shown the formation of homogeneous nickel–aluminum layer. X-ray diffraction (XRD) has indicated that the layer is textured and probably composed of the NiAl and Ni 2Al 3 phases.