A Molecular Dynamics Study Of Thermal Stability Of Surface Quantum Dot Structure

Owing to various quantum effects induced by confinement in nanometer scale, surface arrays of quantum dots have great potential of applications in modern electronic and opto-electronic industries. Due to surface effect, thermal stability of the quantum dot structures has become an important issue in this field.A three-dimensional molecular dynamics simulation of structural thermal stability of surface quantum dot of an fcc aluminum has been carried out. An embedded atom method (EAM) potential is employed and a surface nano crystalline pillar model is adopted. Destabilization process and mechanism, the effects of geometrical feature of nano crystalline pillar and temperature on its stability are specially studied.The results show that, a critical section size dc is found in a nano crystalline pillar, which is composed by sub-square {111} stacking plane and two side-planes, the perpendicular {112} and {110} plane. When section size of crystalline pillar is less than dc, the pillar collapses and fuses; while the section size is larger than dc, it does not happen. And the value of dc increases lineally as the temperature rises. The collapsed and fused atomic group recrystallizes immediately and forms a polyhedron bounded by {111} and {100} facets, which is very stable until fusion when improving annealing temperature and prolonging annealing time. When the section size of nano crystalline pillar is at critical value, there are two ways to form the polyhedron. One way is the above process of fusion-recrystallization; the other way is the rearrangement of surface atoms through the diffusion and migration. While the section size of nano crystalline pillar is larger than critical value, even an atom layer larger, the rearrangement of whole surface atoms can not be found, only a few atoms...