posted on 2024-03-15, 07:03authored byIvna Kavre Piltaver, Robert Peter, Kresimir Salamon, Maja Micetic, Mladen Petravic
The evolution of different W oxidation
states and the
oxide reduction
mechanism of polycrystalline WO3 thin films, induced by
low-energy H2+ bombardment at room temperature,
was investigated in situ by X-ray photoelectron spectroscopy around
W 4f and O 1s core levels and the valence band. A hydrogen tungsten
bronze is formed at the beginning of the reduction process, as is
evident from the development of the W5+ oxidation state
and the creation of the O–H bonds. With the higher H implantation
dose, reduction proceeds with the creation of H2O gas molecules,
whose evolution with the bombardment time correlates with the cumulative
concentration fractions of W4+, W2+, and W0 oxidation states. The generation of H2O molecules
removes O atoms from the WO3 matrix, inducing the reduction
of WO3 to lower oxides and, subsequently, metallic W, which
is the dominant phase on the surface after 180 min of bombardment.