Synthesis and electronic structure of epitaxially stabilized Sr2−xLaxVO4 (0⩽x⩽1) thin films

We have synthesized a-axis-oriented epitaxial thin films of layered vanadate Sr2−xLaxVO4 on LaSrAlO4 (100) substrates using a pulsed-laser deposition technique. Epitaxial interface energy stabilizes compounds from V4+ (x=0) to V3+ (x=1), for which none of bulk single crystal has been synthesized. The transport property including its anisotropy has been studied to reveal metallic conduction for x=0.15 and 0.2. The two-dimensional nature of the crystals gives insulating behavior along the c axis for all the compositions. Optical measurements indicate that the doped electrons are responsible for the insulator-to-metal transition as well as for the systematic variation of electronic structure from V4+ to V3+-based Mott insulators.