Growth of novel α-MoO3 hierarchical nanostructured thin films for ethanol sensing

In this research, thin films of molybdenum trioxide (MoO3) with hierarchical microsphere morphology were deposited on glass substrates via the facile hydrothermal technique, using ammonium heptamolybdate tetra hydrate as a precursor. The morphology, elemental composition, crystal structure and optical properties of the synthesized thin films were studied using FESEM, EDS and Raman spectroscopy, XRD pattern analysis and UV-Vis spectroscopy, respectively. The XRD pattern indicates the formation of the alpha-MoO3 phase with a polycrystalline nature. Raman spectra confirm that the films are orthorhombic. FESEM exhibits the successful growth of thin films with a hierarchical microsphere structure. The gold interdigital connection employed as an electrode for the fabrication of the gas sensor. The thin layer sample was exposed to various concentrations (100-1000 ppm) of ethanol vapor at 210-300 degrees C. The response values at an optimum temperature of 260 degrees C were recorded to be about 23% for 100 ppm and 76% for 1000 ppm of ethanol vapor. The response and the recovery times of the sensor at 260 degrees C, when it was exposed to the lowest gas concentration of 100 ppm, were recorded to be about 111 and 66 s, respectively.