Ultrathin transparent conductive oxides tunable over visible and near-infrared by orbital overlap engineering

Elemental substitution is a traditional step to fabricate transparent conductive oxides (TCO). In the case of the most popular TCO, In x Sn[Formula: see text]O (ITO), further improvement of the material is limited by the segregation of Sn, and from the viewpoint of economy, the limited reserve of rare elements like indium makes these TCOs expensive and unsustainable. Here we demonstrate an excellent alternative, ultrathin tunable visible and near-infrared transparent conductive films fabricated with correlated metal oxides, strontium niobate and vanadate. The optical and electronic transport properties of these correlated metal oxide epitaxial thin films can be tuned by engineering the d-orbital overlap with the 2p electrons of the oxygen by changing the ratio of niobium (4d) and vanadium (3d) atoms. The transparent edges at both ultraviolet and near infrared sides have a blueshift with increasing concentration of niobium, which can be attributed to increased band overlap and a resultant decrease in correlation. The resistivity increases in the alloy reaching a maximum near where niobium and vanadium are at 50% concentration due to the decrease of translational symmetry of the lattice. The optimum thickness for the best figure of merit as a TCO of this correlated system is one tenth (10[Formula: see text]nm) that of ITO (100[Formula: see text]nm).