Crystallographic study of self-assembled dysprosium silicide nanostructures on Si(001)

The crystallography of epitaxial dysprosium silicide nanometer scale islands on Si(001) has been studied using transmission electron microscopy. Cross-sectional high resolution images show that the silicide nanostructures have either hexagonal or orthorhombic/tetragonal crystal structure. Moire fringe patterns from plan view specimens show that elongated islands have the hexagonal structure while islands with smaller aspect ratios have the orthorhombic/tetragonal structure of DySi2. Less lattice distortion and/or fewer dislocations are seen along the small lattice mismatch direction for both the hexagonal and orthorhombic/tetragonal silicides, indicating that lattice mismatch plays an important role in controlling island morphology.