X-RAY PHOTOELECTRON-SPECTROSCOPY, ATTENUATED TOTAL REFLECTANCE FOURIER-TRANSFORM IR SPECTROSCOPY AND TRANSMISSION ELECTRON-DIFFRACTION STUDIES OF ORIENTED CADMIUM IODIDE PREPARED IN A LANGMUIR-BLODGETT TEMPLATE

Oriented CdI2 has been prepared in a deposited Langmuir-Blodgett (LB) film by the reaction of gaseous HI with a 20-layer LB film of cadmium arachidate. Attenuated total reflectance Fourier transform IR spectros copy shows that the conversion goes to completion, while X-ray photoel ectron spectroscopy analysis of the HI-exposed cadmium arachidate film reveals a Cd:I ratio consistent with the CdI2 Stoichiometry. Electron diffraction shows that the CdI2 is oriented exclusively with its [001 ] axis normal to the LB film basal plane and for domains ranging up to several microns has a preferred alignment about the [001] axis. The r esults suggest that the organic template plays a role in orienting the CdI2 within the LB plane and that some degree of lattice matching exi sts between the LB template and the (001) face of CdI2. The oriented s ynthesis described here is in contrast with previous attempts at templ ate-directed syntheses using deposited LB films which have resulted in the mediation of particle size only and not particle orientation. The difference here may be that CdI2 has a layered structure in the bulk, crystalline phase which complements the LB film structure.