EPITAXIAL-GROWTH OF SIZE-QUANTIZED CADMIUM-SULFIDE CRYSTALS UNDER ARACHIDIC ACID MONOLAYERS

Cadmium sulfide crystals were grown under arachidic acid monolayers at room (20 degrees C) and low (3-4 degrees C) temperature via the slow infusion of hydrogen sulfide gas into the closed environment surrounding a trough containing the monolayer-coated aqueous cadmium chloride solution subphase. Transmission electron microscopy and atomic force microscopy revealed that the crystals were rodlike in morphology with widths of 5-15 nm and that extensive twinning, apparent as dendritic outgrowths from the main crystal, was present. Selected-area diffraction patterns possessed 6-fold geometry and demonstrated that the CdS crystals grew epitaxially with respect to the monolayer. Analysis of the patterns showed that only CdS of hexagonal structure precipitated and that nucleation principally occurred on the {01.0} and {0001} faces. Reduction in the temperature of the experiment dramatically decreased the rate of crystallization, yielded thinner crystals, and blue shifted the absorption edge from 520 to 480 nm.