Gd disilicide nanowires attached to Si(111) steps

Self-assembled electronic devices, such as quantum dots or switchable molecules, need self-assembled nanowires as connections. We explore the growth of Gd disilicide nanowires at step arrays on Si(111). Atomically smooth wires with large aspect ratios are formed at low coverage and high growth rate (length ? 1 ? m, width 10 nm, height 0.6 nm). They grow parallel to the steps in the [1 0] direction, which is consistent with a lattice match of 0.8% with the a-axis of the hexagonal silicide, together with a large mismatch in all other directions. This mechanism is similar to that observed previously on Si(100). In contrast to Si(100), the wires are always attached to step edges on Si(111) and can thus be grown selectively on regular step arrays.