Influence of Doping on Hybrid Organic–Inorganic WO3(4,4′-bipyridyl)0.5 Materials

Abstract

In an effort to develop hybrid organic–inorganic tungstates as novel functional electronic materials, single crystals and films of WO3(4,4′-bipyridyl)0.5 have been prepared. These materials are then doped with Na+, Ca2+, and K+ ions by ion implantation. For cross-comparison, all the materials were characterized before and after ion implantation using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, and resistivity measurements. Single-crystal XRD reveals the formation of a layered material where atomic layers of corner-shared WO5N octahedra are linked by bipyridyls that define cage structures potentially to accommodate intercalated ions. A considerable amount of intercalated species, absent in the original samples, was observed in the XPS spectra of WO3(4,4′-bipyridyl)0.5-coated films after ion implantation, as well as the formation of reduced tungsten species. The appearance of new modes in Raman spectra after ion implantation arises from symmetry reduction due to the intercalant, and an associated drop in electrical resistance can be attributed to the injection of charge carriers into the conduction band.