Solid-state photochemistry of dirhenium carboxylates and the deposition of rhenium oxide thin films

Rhenium carboxylates of general formula Re2(O2CnH2n+1)Cl2 where n = 5–8, were studied as precursors for the photochemical deposition of rhenium trioxide thin films. Solutions of the inorganic complexes were spin coated on p-type silicon(1 0 0) substrates and the solid-state photochemistry studied at room temperature. These compounds were deposited by spin coating onto silicon(1 0 0) forming crystalline thin films with lamellar, bilayers structures with planes of rhenium(III) coordinated to the carboxylate group as demonstrated by X-ray diffraction experiments. The carboxylates complexes underwent a photochemical reaction, consistent with the decarboxylation of carboxylate ligand to generate CO2 and the radical disproportionation products. The photolyzed films showed sensitivity towards atmospheric water, transforming into a rhenium bronze structure of the type HxReO3. Auger electron spectroscopy indicated that the final film is carbon free and composed only of Re and O. The same behavior was observed in all the rhenium carboxylates independent of the alkyl chain length. The 2-ethylhexanoate complex did form amorphous thin films which also show the highest quantum yield (Φ = 0.004).