Facile synthesis, characterization, and photoluminescence of lamellar α-MoO3 thin films

In this research, molybdenum trioxide (MoO3) thin films were coated on glass substrates using the spray pyrolysis technique. 0.05 M ammonium heptamolybdate tetrahydrate was used as a precursor and deionized water as a solvent. Four different samples were synthesized by varying carrier gas pressure during the spray process. The morphological, structural and optical properties of thin films were investigated. XRD results revealed the formation of alpha-MoO3 phase and the best crystalline quality was found for films grown at the carrier gas pressure of 2.0 bar, which exhibited a strong peak at (0 2 0). The result of XRD analysis was further confirmed by Raman spectroscopy which showed the formation of alpha-MoO3 thin films with the most intense peak at 818 cm(-1). SEM images showed that MoO3 films have lamellar morphology. UV-Vis spectroscopy results showed that the sample prepared under the carrier gas pressure of 2.5 bar has the highest optical absorption. Bandgaps of samples were calculated to be in the range of about 3.48-3.66 eV. Synthesized samples show intense photoluminescence emission at room temperature with the four prominent peaks located at 345, 396, 418 and 436 nm in accordance with the degree of crystallinity.