A numerical investigation into the growth of TiNi thin films using molecular dynamics

MA Ichou and H Mes-adi and K Saadouni and T Mouhib, JOURNAL OF CRYSTAL GROWTH, 667, 128218 (2025).

DOI: 10.1016/j.jcrysgro.2025.128218

TiNi thin film has become the most widely used shape memory alloy in various industrial and medical applications. An in-depth study of their growth mechanisms and crystalline properties is essential. Molecular dynamics (MD) simulations provide a comprehensive understanding, predicting various growth mechanisms before making the deposit experimentally, and identifying the optimal growth conditions that lead to the formation crystalline film for achieving desired properties. Here, the effects of incidence energy, substrate temperature, and incidence angle on the deposition of TiNi film are modeled using MD simulation with a 2NN MEAM interatomic potential. The results show that at an incident energy of 0.1 eV, the deposited atoms cluster together, ultimately forming a rough film due to their low surface mobility. In the energy range of 1 to 15 eV, the high mobility of deposited atoms inhibits cluster formation on the surface. This results in smoother films and suggests that the growth occurs in a layer-by-layer manner. Increasing the substrate temperature from 300 to 600 K slightly reduces film roughness. This improvement is due to the enhanced agitation of the atoms, which also promotes the filling of surface voids. At low incidence energies (0.1 and 1 eV), increasing the incidence angle changes the direction of the incoming atoms, causing collisions between these atoms above the surface. This reduction in atomic mobility promotes cluster formation, which in turn increases the roughness of the film. In contrast, for higher incidence energies (10 and 15 eV), the surface roughness remains largely unaffected by the incidence angle up to 45 degrees. Beyond this point, a significant increase in roughness is observed. This behavior is attributed to the self-shadowing effect. Increasing the incident energy enhances the diffusion of film atoms from the surface sites into deeper layers of the substrate. This process is accompanied by the ejection of substrate atoms into the thin film, which improves mixing. Based on the common neighbor analysis of atoms, the film maintains an amorphous structure under all deposition conditions and the FCC phase diminishes with increasing incidence energy and temperature.

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