Spectroscopic Studies of Layered Solids

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The lamellar transition metal phosphorus trichalcogenides form an important family of two-dimensional semiconducting materials. These compounds are of interest to researchers because of their highly two-dimensional physical properties and their unusual solid-state chemistry. The layered lattices exhibit solid-state "intercalation" reactions in which molecules insert between lattice planes. The process of intercalation often results in dramatic and unpredictable modification of the chemical and physical properties of the host lattice. Although the intercalation reactions have been studied for more than two decades, many interesting questions of mechanism and structure in the solid-state intercalation chemistry of these materials remain unresolved. The research described in this proposal is directed toward an improved understanding of the mechanism of intercalation in these materials. Charge balance is an important constraint to the intercalation of cationic species and may be achieved by elimination of lattice cations. It is proposed to utilize electron spin resonance (ESR) spectroscopy to study the complex equilibrium between inter- lamellar and intra-lamellar cations. In many reactions a mechanism is involved in which an electron is transferred to an unidentified site in the host lattice. They propose to utilize photoluminescence and optically detected magnetic resonance (ODMR) spectroscopy to determine the lattice reduction site.