On the growth and coalescence of the epitaxial islands of L1_0-FePt (001) thin-film

摘要

The growth and coalescence behavior of L1_0-FePt (001) epitaxial islands have been studied using in-plane and cross-section HRTEM study. In particular, the defect structure of coalesced boundary has been investigated utilizing FTT technique by investigating the defects of lattice-fringes of boundary plane near the boundary. The growth of epitaxial islands, at low deposition rate, leads to a development of an island-network structure, which consists of a network of inter-island space channels (IISCs). The IISCs are basically composed of two-90° (110)s and one (200), which are slightly adjusted at a corner to meet the force balance. The space-channels remaining un-filled up to percolation-stage are mostly two 90° (110) channels because of the presence of two chemically distinctive (110) surfaces. The coalescence of island network structure occurs either by "crack-closure" (zipping) mechanism or by "groove-filling" mechanism by repeated epitaxial growth. The defect structure in a simple "zipped" interface consists of two asymmetrical tilt boundaries with opposite sense to minimize the strain energy. The magnetic coercivity and nucleation field, which are large in island-network structure, decrease significantly with the progress of coalescence due to the introduction of defects at the interface.