Self-assembled Gd silicide nanostructures grown on Si(001)

The growth of self-assembled gadolinium silicide nanostructures on Si(001) was studied over a range of metal coverages and growth temperatures. Scanned probe microscopy was used to study the nanostructure morphology. The analyses of cross-sectional transmission electron microscopy images, plan view transmission electron microscopy moire fringe patterns, and nanobeam electron diffraction patterns show that the Gd silicide nanostructures fall into two classes: elongated nanowires with hexagonal crystal structure and rectangular islands with orthorhombic (or tetragonal) crystal structure. These results indicate that the nanostructure morphology is controlled by the magnitude and direction of the lattice mismatch with respect to the substrate. Optimum growth conditions for preferential growth of either nanowires or islands are described. In addition, the phase transformation from hexagonal to the more stable orthorhombic (or tetragonal) phase is observed and discussed.