Effect of oxidation on mechanical properties of Ni/Cu interface: A density functional theory study

Nickel/Copper (Ni/Cu) interfaces are applied in various fields such as manufacturing of thermoelectric modules and soldering applications. Therefore, the bond strength and mechanical properties of the Ni/Cu interfaces were investigated using spin-polarized density functional theory calculations. Compressed Cu slabs were utilized to model coherent Ni/Cu interfaces. The bond strength of the Ni/Cu interface was evaluated by calculating the work of separation for the (100), (110), and (111)-oriented interfaces. The mechanical properties of the most stable Ni/Cu interface configurations in each orientation were studied along the normal direction using rigid grain shift and homogeneous lattice extension methods. During homogeneous stretching of the Ni/Cu structures along the [100]-, [110]-, and [111]-directions, fracture was initiated in the Cu region because of its smaller work of separation than that of the interface. In the (110)- and (111)-oriented interfaces, the interlayer was separated by the addition of an oxygen (O) atom in the Ni/Cu interface. This oxidation results in a significant decrease in the work of separation at the interface. However, oxidation at the interface does not significantly change the mechanical properties of the Ni/Cu structure, resulting in a fracture strain similar to that before the insertion of the O atom.