Patterned nanostructure in AgCoÕPtÕMgO„001... thin films

The formation of a patterned nanostructure in an AgCo/Pt/MgO~001! thin film is simulated by a technique of combining molecular dynamics and phase-field theory. The dislocation ~strain! network existing in Pt/MgO is used as a template whose pattern is transferred to the AgCo phase in spinodal decomposition, resulting in regular arrays of Co islands that are attracted by the dislocations. The influence of various factors, such as the component concentration and film thickness, is studied. It is found that the spinodal decomposition of AgCo in this system is mainly characterized by a competition between a surface-directed layer structure and the straininduced patterned structure, where the patterned Ag-Co structure only dominates in a small range near the interface ~less than ten atomic layers!. However, if the interlayer diffusion can be minimized by controlling film growth conditions, it is shown that the patterned structure can be formed throughout the entire film.