Independent Tuning of Optical Transparency Window and Electrical Properties of Epitaxial SrVO3 Thin Films by Substrate Mismatch

Abstract

Transparent metallic oxides are pivotal materials in information technology, photovoltaics, or even in architecture. They display the rare combination of metallicity and transparency in the visible range because of weak interband photon absorption and weak screening of free carriers to impinging light. However, the workhorse of current technology, indium tin oxide (ITO), is facing severe limitations and alternative approaches are needed. AMO perovskites, M being a nd transition metal, and A an alkaline earth, have a genuine metallic character and, in contrast to conventional metals, the electron-electron correlations within the nd band enhance the carriers effective mass (m*) and bring the transparency window limit (marked by the plasma frequency, ω*) down to the infrared. Here, it is shown that epitaxial strain and carrier concentration allow fine tuning of optical properties (ω*) of SrVO films by modulating m* due to strain-induced selective symmetry breaking of 3d-t(xy, yz, xz) orbitals. Interestingly, the DC electrical properties can be varied by a large extent depending on growth conditions whereas the optical transparency window in the visible is basically preserved. These observations suggest that the harsh conditions required to grow optimal SrVO films may not be a bottleneck for their future application.