Selective deposition of Mo₅O₁₄/MoO₃ composite onto MoO₂ surfaces induced by MoO₃/MoO₂ interfacial reaction

This study presents the deposition of a Mo₅O₁₄/MoO₃ composite onto the surface of a pre-grown MoO₂ film by exposing the MoO₂ surface to MoO₃ vapours under low vacuum. Significant surface selectivity was observed, with the formation of a Mo₅O₁₄/MoO₃ composite occurring exclusively on the MoO₂ surface. In contrast, pure MoO₃ was deposited directly onto the uncovered part of the used SiO₂/Si substrate. The formation of the composite was revealed by X-ray diffraction, Raman spectra, and Energy Dispersive Spectroscopy. The selective deposition of the composite is attributed to the solid-state reaction between MoO₃ and MoO₂ at their interface, which is facilitated by the porous structure of the MoO₂ film (as confirmed by scanning electron microscopy). Thermodynamic considerations support this reaction mechanism and predict the temperature range in which the reaction can occur.