Structural analyses and reverse Monte Carlo modeling of niobium oxide amorphous film prepared by sputtering method

Structural analyses of niobium oxide (NbO_x) amorphous film prepared with a sputtering method have been performed by using synchrotron X-ray radiation at SPring-8. The composition was determined as Nb₂O₅·0.8H₂O from the measurements of Rutherford back scattering, X-ray fluorescence, X-ray absorption near edge structure, and thermal desorption spectroscopy. Structural information was obtained by extended X-ray absorption fine structure and high energy X-ray diffraction measurements. It was supposed from the experimental data that NbO_x consisted of distorted NbO_n polyhedra connected by corner- and edge-sharing. Structural models were constructed with reverse Monte Carlo (RMC) simulations. In the RMC models, the structural characteristics were successfully reproduced, and H atoms were, however, randomly distributed. Then, bond valence sum (BVS) constraint was introduced to the RMC simulation. As the results, narrower distribution in BVS was achieved for all the constituent atoms, and distinct OH bonds were effectively generated in the RMC model.