Synthesis and optical spectroscopic studies of semiconducting cadmium sulfide nanowires.

Optical properties of cadmium sulfide nanowires of 50-100 nm diameter prepared by the pulsed-laser vaporization method have been studied using photoacoustic, UV-Vis, Raman, and photoluminescence spectroscopy. The photoacoustic (PA) technique yielded clean spectra with a steeper absorption edge for as-prepared opaque semiconducting CdS nanowires when compared to the corresponding conventional optical absorption spectra. The PA signal intensity was also significantly higher for nanowires. The Raman spectrum revealed increased exciton-longitudinal-optical-phonon coupling. The appearance of a narrow photoluminescence peak at 491 nm (FWHM approximately 9 nm) and the absence of emission above 500 nm demonstrate the high quality of nanowires. High-resolution transmission electron microscopy showed excellent ordering of the atoms in the [001] planes perpendicular to the growth direction.