Metal-insulator transitions in (V1-xCrx)2O3 thin films deposited by reactive direct current magnetron co-sputtering

Vanadium oxides are promising candidates for application in memory devices based on the control of their various metal-insulator transitions. We report here on the thin films deposition of the strongly correlated system (V1-xCrx)2O3 over a wide range of composition 0 ≤ x ≤ 0.60 by reactive DC magnetron co-sputtering of pure V and Cr targets. Thin films were characterized by Scanning Electron Microscopy, Energy Dispersive X-ray spectroscopy, X-ray diffraction and transport measurements. These studies demonstrates the existence of compressive stress reaching 0.8 GPa in 200 nm thick films, whereas thicker 1 μm films exhibit lower internal stress. This compressive stress modifies significantly the phase diagram of the 200 nm films, shifting the critical chromium content triggering the bandwidth-controlled metal-insulator transition from x = 0.011 in unstressed films to more than 0.04. This work highlights the need for an accurate control of the Cr content and of the compressive stress to stabilize the Mott insulator phase in (V1-xCrx)2O3 thin films.