Z. Y. Pan, G. J. Shen, L. G. Zhang, Z. H. Lu and J. Z. Liu
Cadmium sulfide (CdS) particulate films, composed of highly oriented,
rod-like nanocrystals have been generatedin situ by the exposure
of stearic acid (SA) Langmuir monolayer-coated aqueous CdCl2
solutions to hydrogen sulfide (H2S). The SA-coated CdS
particulate films were transferred to a solid substrate and examined by
transmission electron microscopy (TEM) and Auger electron energy
spectroscopy. It was found for the first time that the electron
diffraction pattern was a composite one with six sets of diffraction
patterns which were contributed by the different oriented CdS nanocrystals
in these particulate films system. The epitaxial growth of rod-like CdS
nanocrystals has been rationalized in terms of matching the
d220 spacing of the cubic CdS crystals and the
d100 spacing of the hexagonal closed-packed SA
monolayer. The presence of a negatively charged monolayer at the air/water
interface was an essential requirement for the oriented growth of CdS
nanocrystals. This leads to a novel means of fabrication of highly
oriented semiconductor quantum wires.