ABSTRACT
This chapter presents a novel approach for the direct synthesis
of ultrathin Si nanowires (NWs) exhibiting room temperature
light emission, based on a wet etching process of Si substrates
assisted by a thin metal film. The thickness-dependent morphology
of the metal layer produces uncovered nanometer-sized regions,
which act as precursor sites for NW formation. The process is
cheap, fast, maskless, and compatible with Si technology. Very
dense arrays of long (up to several μm) and thin (diameter of 5-
9 nm) NWs have been synthesized. An efficient room temperature
photoluminescence (PL), visible to the naked eye, is observed when
NWs are optically excited; the PL spectrum exhibits a blue shift
with decreasing NW size in agreement with the occurrence of
quantum confinement effects. A prototype device based on Si NWs,
showing a strong and stable electroluminescence at low voltage, has
been fabricated. The first evidence of simultaneous light emission
from both Si (in the visible region) and Ge (in the IR region)
nanostructures in Si/Ge NWs is also presented. The relevance and
the perspectives of the reported results, which open the route
toward novel photonic applications of semiconductor NWs, are
finally discussed.
