Nonmonotonic dependence of adhesion between liquid aluminum and silicon surface on the temperature of the surface

Abstract In this paper, the effect of temperature on the adhesion properties between liquid aluminum (Al) and solid silicon (Si) in the presence and absence of vacancy defects is elucidated. Firstly, the perfect defect-free and vacancy defect models consist of crystalline Al probe and Si substrate are established by classical molecular dynamics simulation method. Then, the melting and adhesion process of probe Al are simulated, and the adhesion performance and microscopic permeation evolution of liquid Al/solid Si are analyzed. The results show that the adhesion force changes nonmonotonically with increasing substrate temperature T without vacancy defects. Specifically, when the substrate temperature varies at relatively low values smaller than the melting point of Al, that is, 100 K < T < 933 K, the thermal excitation provides more energy to the substrate Si atoms, which intensifies the aggregation of the substrate atoms, makes the interfacial atoms more dense and the number of atoms permeating into the substrate decreases, resulting in a decrease in adhesion force. On the contrary, when 933 K < T < 1500 K, due to the thermal effect, higher temperatures intensify the thermal vibration of the substrate atoms, resulting in violent collisions between the interfacial atoms, and the space for free movement increases, thus making the distance between the atoms larger. And the number of Al atoms permeating into the substrate Si increases, leading to an increase in interfacial adhesion. Furthermore, the adhesion force shows an upward trend with the elevated temperature in the presence of vacancy defects at low temperatures, this is attributed to the fact that more atoms are broken away from the equilibrium lattice structure, and the number of permeating atoms increases by increasing temperature. In particular, the interfacial adhesion is the largest when the vacancy defects of the substrate are the most serious.