  Surface enhanced Raman spectroscopy (SERS) has the capacity of detecting
trace amount of biological or chemical matter, even single molecules, through
the use of metallic nanostructures such as nanorods. Silver (Ag) and gold (Au)
nanorods have led to the impressive enhancement of Raman signals, but they are
either expensive, degrade fast over time, or suffer from poor sample
repeatability. In contrast, Al is much less expensive, and Al nanorods could
potentially be resistant to degradation over time due to the protection from
native aluminum-oxide layers. Unfortunately, the controllable growth of Al
nanorods has not been reported so far. This Letter reports, for the first time,
the controllable growth of Al nanorods using physical vapor deposition (PVD);
through the use of oxygen (O) surfactants. The enhancement factor of the Al
nanorods in SERS is as high as 1250, and shows nearly no degradation after
storage in ambient for 30 days or annealing at 475 K for one day.
