Substrate and annealing temperature effects on the crystallographic and optical properties of MoO_3 thin films prepared by laser assisted evaporation

摘要

MoO_3 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 ℃ in all samples from the amorphous to the β phase with a small percentage of a phase, and another one was found around 500 ℃ from the a + β to the a phase. The percentage errors between the lattice parameter a_0 of the crystallographic index card for the MoO_3 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 M0O_3 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.