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.