Growth and Characterization of Transition Metal Phosphochalcogenide Compounds, Alloys, and Superlattices

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9308854 Kevan The goal of the proposed research is to apply a variant of molecular beam epitaxy called van der Waals epitaxy to synthesize novel compounds and superlattices based upon transition metal phosphochalcogenide (MPX3) compounds. The primary motivation to pursue this area is a qualitative similarity to the high temperature cuprate superconductors. Alternative high Tc materials will thus be sought. The currently known transition metal MPX3 compounds are all correlated antiferromagnetic insulaators and have a quasi-two-dimensional layered structure similar to MX2 compounds. The synthetic flexibility allowed by vapor phase epitaxy will allow systematic variation of effective one-electron band widths and effective on-site correlation energies to induce an insulator-metal transition, thereby producing materials with novel and potentially useful transport, optical, and magnetic properties. Specifically, i) the number of known MPX3 compounds will be increased to include 4d and 5d metals, ii) random alloys M'yM1-yPX3 will be grown to induce n- or p-type doping, and iii) superlattices combining MPX3 compounds with a variety of layered maaaaterials having divergent dielectric properties will be produced. These new materials and structures will be characterized by a variety of techniques. ***