Off-Stoichiometry Engineering of the Electrical and Optical Properties of SrNbO3 Using Oxide Molecular Beam Epitaxy

Abstract

The highly conducting and transparent inorganic perovskites SrBO₃ with V, Nb, Mo, and their mixtures at the B-site have recently attracted the attention of the oxide electronics community as novel alternative transparent conducting oxides. For different applications, from solar cells to transparent electronics, it is desirable to tune the optical transmission window in the ultraviolet, visible, and infrared (IR) range. The conventional approach is substitutional design at the A- and/or B-site. Here, a method of engineering the off-stoichiometry of the perovskite SrNbO₃ is used, opening new pathways to broaden the range of applications without adding additional elements. For oxide molecular beam epitaxy (MBE) grown SrNbO₃ on GdScO₃ substrates, it shows that controlled Sr deficiency shifts the plasma edge from ∼2 eV in the visible range into the near-IR region, 1.37 eV (similar to stoichiometric SrVO₃). The epitaxial growth using MBE allows going beyond the limitations of phase stability set by thermodynamics. This work includes controlled vacancy sites as quasi-substitutional virtual elements and advances the stoichiometry engineering of perovskite oxides using an oxide MBE.