  We report on a new surface phase of the Co-vicinal-Cu(111) system which
exhibits self-assembled uniform Co quantum wires that are stable at 300K.
STM-imaging measurements show that wires will self-assemble within a narrow
range of Co coverage and, within this range, the wires increase in length as
coverage is increased. The STM images show that the wires form along the
leading edge of the step rise, differentiating it from previously theoretically
predicted atomic-wire phases. The formation of relatively long laterally
un-encapsulated one- and two-atom wires also differentiates it from past
experimentally observed step-island formation. Furthermore, our experiments
also show directly that the Co wires coexist with another Co phase that had
been previously predicted for growth on Cu(111). Our observations allow us to
comment on the formation kinetics of the atomic-wire phase and on the fit of
our data to a recently developed lattice-gas model.
