Preparation and characterization of molybdenum oxide thin films by sol-gel process

This paper presents a new sol-gel process to prepare molybdenum oxide thin films. A molybdenum acetylacetonate sol was prepared by employing the system CH3COCH2COCH3/MoO3/C6H5CH3/HOCH2CH2 OCH3. A molybdenum acetylacetonate gel was prepared by addition of aqueous NH3. Thermal gravimetry (TG) and differential thermal analyses (DTA) of the gel suggested that crystallization of MoO3 occurs in a 140 K temperature range around 508degreesC. MoO3 films were prepared on fused silica, Si (111) and Al2O3 (012) substrates by annealing spin coating films of the sol in oxygen environment at 508degreesC. X-ray diffraction (XRD) showed that all films crystallize in alpha-MoO3 structure, and crystallites on fused silica substrate are arbitrarily oriented while those on Si (111) and Al2O3(012) substrates oriented in the (010) direction. SEM investigations showed that MoO3 grains of all films are randomly distributed, with a longitudinal dimension of about 1 - 5 mum and the film thickness is about 1 mum.