Epitaxial growth of tin(II) niobate with a pyrochlore structure

Tin(II) niobate with a pyrochlore structure has a unique valence electronic structure associated with the hybridization of the O-2p and Sn-5sp orbitals. It is represented as the chemical formula of Sn2Nb2O7 for the ideal stoichiometry while reported to have a highly non-stoichiometric tendency. In this study, we have fabricated tin(II) niobate films with a pyrochlore structure on yttria-stabilized zirconia (100) substrates by means of pulsed laser deposition and investigated their optical properties. The single pyrochlore phase has been obtained for the films with Sn/Nb ratios of 0.5 and 0.9. The film with the higher Sn/Nb ratio of 0.9 is epitaxially grown on the substrate with a cube-on-cube orientation relationship. It has a flat surface comparable to that of the substrate. The absorption coefficient of the film is evaluated from optical transmittance and reflectance measurements. The optical direct band gap is estimated to be 2.6 eV and its absorption coefficient reaches 1.0×105 cm−1 at about 3.0 eV above the absorption threshold.