STUDIES OF THE FORMATION AND GROWTH OF Q-STATE CADMIUM SELENIDE PARTICLES IN CADMIUM ARACHIDATE LANGMUIR-BLODGETT-FILMS

The formation and growth of Q-state CdSe particles during exposure of Langmuir-Blodgett films of cadmium arachidate (CdAr) to hydrogen selen ide has been studied using UV-visible absorption, grazing angle FTIR, X-ray photoelectron spectroscopy (XPS), and quartz crystal microbalanc e (QCM) measurements. UV-visible absorbance measurements showed an opt ical blue shift typical of particles between 1.1 and 1.3 nn in radius. In addition to the formation of Q-state CdSe particles, elemental sel enium (formed by the decomposition of H2Se) was present in the films. Grazing angle FTIR and XPS measurements (after subtraction of the cont ributions due to elemental selenium) were consistent with Q-state part icle formation involving quantitative conversion of the Cd2+ ions in t he films to CdSe and the corresponding conversion of CdAr to arachidic acid. Changes in the orientation of the surfactant molecules were als o found to be a consequence of particle growth in the films. QCM measu rements on films exposed to H2Se showed large apparent mass uptakes wh ich were inconsistent with the trends observed using other techniques. This behavior was ascribed to anomalous interactions between H2Se gas and the QCM electrodes.