The properties of nonstoichiometric lanthanum niobium oxide thin films formed using an e-beam deposition technique

Lanthanum niobium oxide thin films were prepared using electron beam physical vapour deposition (EB-PVD). The composition, crystal structure, morphology and optical properties of the films formed were studied. The results indicated that La2O3 and Nb2O5 have different deposition rates, i.e., the stoichiometry of the elements in the thin films is different to the initial evaporated powder. The stoichiometry of 1 La:1 Nb was achieved when the molar ratio of the initial oxides was 1.3 La2O3:1 Nb2O5. The thin films formed were amorphous in all samples, and the molar mixing ratio of the La2O3 and Nb2O5 powders did not have an influence on the crystallinity of the thin films formed in our experiments. Swanepoelʹs method was used for the optical parameter calculations. It was found that the refractive indexes were dependent on the quantity of lanthanum in the thin films and had a tendency to decrease with an increasing amount of lanthanum. The calculated optical band gaps were from 3.69 to 3.9 eV.