Substrate and annealing temperature effects on the crystallographic and optical properties of MoO3 thin films prepared by laser assisted evaporation

MoO3 thin Films were prepared using the assisted laser evaporation technique. Samples were grown on glass and silicon substrates at different substrates temperatures. The effect on structural and optical properties of the substrate and on annealing temperatures was evaluated. A phase transition was found around 200 degrees C in all samples from the amorphous to the beta phase with a small percentage of alpha phase, and another one was found around 500 degrees C from the alpha+beta to the alpha phase. The percentage errors between the lattice parameter a(0) of the crystallographic index card for the MoO3 alpha phase and the indexed lattice parameters were 1.4% and 0.3% for the samples deposited on glass and silicon respectively, indicating the crystalline structure of the silicon substrate favors the formation of the MoO3 alpha orthorhombic phase. The spectral variation of the refractive index and the absorption coefficient were theoretically determined. The amorphous samples presented a constant gap of 3.2 eV while the optical properties critically depended on the substrate and annealing temperatures. (c) 2011 Elsevier B.V. All rights reserved.