Oxygen-Vacancy-Endurable Conductors with Enhanced Transparency Using Correlated 4d² SrMoO₃ Thin Films

Degenerately doped wide-bandgap semiconductors, e.g., Sn-doped In₂O₃, are the most conventional transparent conductors (TCs), but degradation of the TC performance by a doping bottleneck or instability due to oxygen vacancies is encountered. Recently, nondoped correlated metals have attracted great attention as a new strategy for developing next-generation TCs. To date, most studies of this brand-new type of TC have been biased toward 3d¹ vanadates. Here, compared with 3d¹ SrVO₃, it is found that the 4d² SrMoO₃ thin films show promising TC properties: higher ultraviolet–visible transmittance of 80% and extremely low resistivity of 100 µΩ cm at room temperature. This enhancement in the SrMoO₃ is ascribed to a p-4d transition occurring at higher photon energy and a higher number of electrons in the outermost 4d orbitals, respectively. In addition, the TC properties of the correlated SrMoO₃ are resistive to oxygen vacancies. Using spectroscopic ellipsometry, it is found that this robustness is attributed to the lack of formation of defect states near the Fermi level, which is different from the observation in conventional TCs. Taken together, the correlated 4d² SrMoO₃ is appealing for next-generation oxygen-vacancy-endurable conductors with enhanced transparency.