Oxygen K-edge x-ray absorption near-edge structure in crystalline and amorphous molybdenum trioxides

Abstract

X-ray absorption near-edge structure (XANES) signals at the oxygen K edge in polycrystalline α-MoO 3 and amorphous a-MoO 3 thin film were analysed within the full-multiple-scattering (FMS) formalism. Significantly different XANES signals were found for non-equivalent oxygen atoms in low-symmetry layered-type α-MoO 3 structure. The obtained results are in agreement with the experimental data and allow us to interpret all XANES peaks for α-MoO 3 . Besides, the FMS XANES simulations, performed for several fragments of α-MoO 3 structure, allowed us to explain the O K-edge XANES in amorphous a-MoO 3 thin film. We found that although the crystallographic structures of α-MoO 3 and a-MoO 3 are strongly different, a cluster consisting of six MoO 6 octahedra joined by vertices produces the main contribution to both XANES signals.

Investigating the Local Structure of Lanthanoid Hafnates Ln2Hf2O7 via Diffraction and Spectroscopy

“…However, as the Ln cation radius decreases, peaks A 1 –A 3 merge into a single broad peak. Peak broadening tends to suggest an increase in disorder, and a similar trend was observed in amorphous HfO 2 and MoO 6 . , Peak broadening can be attributed to a breakdown of long-range ordering. , The width of peak B, representing the transition of a 1s electron into hybridized O 2p/Hf e g /Ln 6p states, increases as the size of the Ln cation increases. A temperature-induced pyrochlore–fluorite phase transition caused similar broadening in the O K-edge XANES of Gd 2 Zr 2 O 7 .…”

Quantitative use of electron energy-loss spectroscopy Mo-M2,3 edges for the study of molybdenum oxides

“…Such study is still lacking even if previous studies on MoO 3 and MoO 2 interpreted the peaks near the absorption threshold as resulting from transitions of oxygen s core states to oxygen p states hybridized with the transitions metal t 2g and e g states [41,50,52]. The ELNES of Mo-M 2,3 edges for the two compounds are shown in Fig.…”

Magnetic Field-Assisted Chemical Vapor Deposition of Iron Oxide Thin Films: Influence of Field–Matter Interactions on Phase Composition and Morphology

“…This variation cannot necessarily be attributed to the Fe 4sp/O 2p hybrids usually found in that energy region, but it stems here from the X-ray absorption fine structure (XAFS) originating from multiple scattering paths in the absorption processes. Specifically, in transition metal oxides, this feature has been found to indicate changes in the long-range order as, for example, found in the amorphization of MoO 3 , where a dampening of this feature was associated with a loss of crystallinity. Theoretical multiple scattering calculations of the O-K edge XAS of Fe 3 O 4 clusters also showed a decreased intensity of this feature with decreasing cluster size .…”