RUI: Intercalation of Heavy Metal Iodides

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9312916 Coleman This research is concerned with the study of formation, characterization, optical properties and theoretical models of a new wide-gap semiconductor intercalation compound. This involves new host systems of layer structure heavy metal iodides. Preliminary data indicate unique large unexpected shifts of the optical band edges and the lack of charge transfer upon intercalation of lead iodide and bismuth iodide with hydrazine and methylhydrazines. A large increase in optical absorption above the band edge and a decrease in absorption below the band edge for the intercalated material produce sharp optical band edges which would have potential uses in modulation spectroscopic optical switching devices. Because this new intercalation system does not appear to follow the usual rigid band model, the proposed work intends to distinguish among the possible bonding models for the process which include polarization, hydrogen bonding, charge transfer, and donor/acceptor bonding. Determining the controlling factors in the bonding mechanism will allow optimization and tailoring of this system's unique optical properties. Specifically, intercalates will be varied to test for effects of polarizability, donor strength, number of hydrogen bonds, and intercalate size. Hosts will be varied to test for ionicity and structure dependence. Physical parameters tested will be the optical transmission and reflection to determine possible changes in the electronic band structure; modulation spectroscopy to determine band structure critical points and optical switching efficiency; weight gain to find the amount of intercalate per formula unit; x-ray analysis for lattice structure changes; magnetic resonance for intercalate mobility and vibrational spectra for phonon contributions. These goals are appropriate for research at an undergraduate institution. ***