Multi-stoichiometric quasi-two-dimensional W_nO_3n−1 tungsten oxides

Abstract

<p>Quasi-two-dimensional tungsten oxide stoichiometric phases, W₁₈O₅₃, W₁₇O₅₀, W₁₆O₄₇, W₁₅O₄₄, W₁₄O₄₁, W₁₀O₂₉, and W₉O₂₆ were identified. It was determined that they nucleate by epitaxial growth on the W₁₉O₅₅ nanowires and grow as thin platelets.</p>

Synthesis and Characterization of Tungsten Suboxide WnO3n−1 Nanotiles

“…The dependency of the Raman spectra on orientation is a dire idence of material anisotropy. Similarly to the previously reported spectra, [20] the trum where the polarisation is parallel to the b axis has sharper and more pronou peaks, pointing to a crystal structure with fewer defects and a higher number of bonds with well-defined lengths. The Raman spectrum recorded with the polaris perpendicularly to the b axis has a greater number of peaks in the lattice (<200 cm − bending mode (200-400 cm −1 ) region, while the peaks associated with W-O stret modes (600-900 cm −1 ) are broader, indicating that multiple bond lengths are pr [27,28].…”

“…The reported nanotiles are composed of multiple W n O 3n−1 phases, with three of those not observed to date. As previously reported, the multiphase nature of a single nanotile could stabilize the W n O 3n−1 phases [20]. In our previous report, the similar multi-stoichiometric platelets had a flat, corrugation-free surface, while the nanotiles have distinct corrugations with tens of nm in depth.…”

“…The change in the morphology could be explained with a slightly different overall stoichiometry. Another reason for this change may be because the nanotiles did not have a template from which to grow, while the platelets grew epitaxially from a nanowire [20]. Similar corrugations are also present in other tungsten suboxides [31][32][33] and could contribute to the stabilization of different phases.…”

“…Only {102} r CS planes were observed, indicating that only W n O 3n−1 structures grow inside the nanotiles [12,19]. Six stoichiometries were determined by measuring the unit cell parameters a, c, and β: [20]. The unit cell parameters a, c, and β of the observed phases are presented in Table 1.…”

“…Only {102}r CS planes wer served, indicating that only WnO3n−1 structures grow inside the nanotiles [12,19]. Six chiometries were determined by measuring the unit cell parameters a, c, and β: W (WO2.938), W15O44 (WO2.933), W14O41 (WO2.928), W13O38 (WO2.923), W12O35 (WO2.917), and W (WO2.909), of which the last three were not experimentally observed to date [20]. The cell parameters a, c, and β of the observed phases are presented in Table 1.…”