Physical study of Eu doped MoO3 thin films

This work highlights some physical properties on Eu-doped MoO3 thin films produced by spray pyrolysis. In practice an aqueous solution of ammonium Molybdate containing various concentration of Europium (0-2%) is sprayed on a glass substrate heated at 460 °C in air. X-ray diffraction (XRD) and Raman spectroscopy showed that all the produced films crystallized in the orthorhombic α-MoO3 like structure. Parallel to these structural studies, the X-ray Photoelectron Spectroscopy (XPS) spectra of the doped films were recorded and compared to that of their MoO3 parent. All exhibited the signature of Mo6+ and O2− species related to MoO3 phase while only the doped ones evidenced the signal of Eu3+ with a binding energy close to that Eu2O3 oxide. Scanning Electron Microscopy evidenced a dense coral-like surface morphology suggesting the formation of juxtaposed and superposed differently sized plates during the film growth. The optical properties of the films were also investigated. Transmission and reflection measurements were typically performed. They showed a transmission coefficient decrease when Eu doping increased (40-75%), making them more valuable for gas sensing application based on opto-electronic properties changes. Finally, these doped films having large specific surfaces may be of interest for possible sensitivity applications such as photocatalysis, gas sensors.