Abstract
Erbium silicides (ErSi2-x) nanowires (NWs) were grown on Si(001) at 700 °C. The orientation relationships between ErSi2-x and Si(001) were determined to be ErSi2-x [0001]// Si [1-10], ErSi2-x(1-100) // Si (001) and ErSi2-x [0001]// Si [-1-10], ErSi2-x (1-200)// Si (001). Owing to the anisotropy of lattice matches on Si(001), ErSi2-x has a preferred direction of growth along ErSi2-x[11-20]. Additional layers on tops of existing NWs have stacking faults, acting as sinks for incoming adatoms resulted in growing rapidly at the expense of laminated NWs. Si is expected to be the dominant diffusing species during intermixing, NWs were surrounded by silicon steps. Due to the shape and deposition rate, the vacancy ordering structure along c-axis is more order in NWs than in thin-film system. The analysis indicates that the variation of vacancy ordering structures depends on the growth conditions. A high density of ordered erbium atomic chain arrays has been grown uniformly on flat Si(001) surface at 500 °C. Site-specific adsorption of metallic erbium atomic-chain arrays were self-organized to grow single-row, double-row and triple-row Er atoms atomic chains with identical period in interspacing on (2×4) reconstructed surface. Single-row atomic chains on (2×4) surface reconstruction are seen to serve as nuclei for adsorbed Er atoms to adjust positions to grow Er silicide nanowires. The extremely high density of atomic Er chains promises to be applicable in altrasmall electronics devices. Stepped growth of erbium silicide nanowires on silicon at 700 °C by one Moiré fringe spacing at a time has been observed in situ in an ultrahigh vacuum transmission electron microscope (UHV-TEM). The transport of Er silicide in the side lane confined by Moiré fringes with a speed tens of the times of the nanowire growth rate was also directly observed. The results indicate that the strain between the Er silicide and silicon is periodic with Moiré fringe spacing as a period. In addition, the surface diffusion plays a major role in the nanowire growth. Two features of ErSi2 islands were formed in Si(001) substrate at 800 °C. One is the island in square shape with trapezoidal cross-sections. And the second feature is self-assembled endotaxial NWs. As more Er is added, the square islands increase in size isotropically. On the other hand, the high-aspect-ratio NW was formed by growth ledges along the interface to relieve the stress generated during the growth.