The Effect of Substrate Temperature on the Optical Properties of MoO3 Nano-crystals Prepared Using Spray Pyrolysis

In this study, thin films of molybdenum oxide were prepared by spray pyrolysis technique on glass substrates. The influence of substrate temperature on their crystallographic structure, surface morphology, and optical properties was studied. The formation of a MoO3 film on the substrate was confirmed through XRD analysis. Furthermore, the presence of the two phases α and β in each of the films was evident. The percentage of phase α varied from 55 % for the film deposited at 200 °C up to 97 % for the film deposited at 400 °C. According to SEM images, MoO3 films have a sponge-type structure on the order of nanometers. Both the optical gap and the refraction index strongly depend on substrate temperature. The optical gap decreases from 3.63 eV for the film deposited at 150 °C up to 3.30 eV for the one prepared at 400 °C. On the contrary, the refraction index measured at 800 nm increases from 1.54 up to 1.61 for the films prepared at 150 °C and 400 °C, respectively.