Asymmetric intermixing and kinetic analysis in Ni/Ti multilayers

JL Zhao and K Yi and H Wang and XX Li and HB He and JD Shao, APPLIED SURFACE SCIENCE, 688, 162422 (2025).

DOI: 10.1016/j.apsusc.2025.162422

The interface quality of Ni/Ti multilayers are crucial for neutron and soft X-ray optics, which is mainly limited by the serious intermixing at Ni-on-Ti interface. However, a fundamental understanding of asymmetric intermixing is still lacking. Herein, we demonstrate the asymmetric intermixing in Ni/Ti multilayers with an empirical molecular dynamic method. The intermixing width of Ni-on-Ti interface is significantly wider than that of Ti-onNi interface at the same incident energy. The simulated intermixing width falls in a reasonable range of experimental values (2.0 - 12 & Aring; for the Ni-on-Ti interface and 2.0 - 6.4 & Aring; for the Ti-on-Ni interface). The threshold behavior of intermixing width indicates the kinetic feature of intermixing process for both interfaces. The kinetic analysis of the exchange process reveals that the fcc site is not only the most successful impact site but also an exchange channel for the hcp site during the Ni-on-Ti deposition. The difference of rigid response during incorporation or exchange process is the key factor in asymmetric intermixing for Ni-on- Ti and Ti-on-Ni interface, which is significantly affected by the difference in lattice constants. The fundamental knowledge of asymmetric intermixing would shed light on tailoring interface quality and improving optical performance of Ni/ Ti multilayers.

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