Highly anisotropic arrays of aligned semiconductor nano-wires with dia
meters in the range 9-22 nm and lengths up to 1 mu m were fabricated b
y electrodepositing CdS into the pores of anodic aluminum oxide, The v
alue of the exciton energy of the semiconductor nano-wires was determi
ned as a function of wire diameter from the excitation wavelength depe
ndence of their polarized resonance Raman spectra in the vicinity of t
he CdS absorption edge, The resonance Raman (RR) spectra were dominate
d by a progression in the longitudinal optical phonon mode, The relati
ve intensities of the members of the progression are both excitation-w
avelength and particle-size dependent. The LO phonon frequency was als
o found to be wire-diameter dependent. The RR spectra were found to be
almost independent of the polarization of the light exciting them. Th
e optical exciton energy was determined to vary from 2.36 eV for the l
argest diameter wires to 2.42 eV for the smallest. The absence of pola
rization dependence is interpreted to be in part due to the fact that
the nano-wires consist of strings of semiconductor crystallites so tha
t the local aspect ratio of the crystallites is both not very great an
d not uniform in the axial direction. For the smallest nano-wires the
radial size uniformity is, however, very high. The dependence of the b
and-gap energy on the diameter of the nano-wires is in good agreement
with theory.