Mapping growth windows in strongly-correlated quaternary perovskite oxide systems by hybrid molecular beam epitaxy

Metal-insulator transitions, high-temperature superconductivity and colossal magnetoresistance represent a few of the many phenomena that emerge in the solid solution $A$'$_{\mathrm{1-x}}A_{\mathrm{x}}B$O$_{\mathrm{3}}$. Growing these in thin film form is, however, a challenge due to the precise control required for the composition, $x$, as well as the stoichiometry ($A+A')$:$B$. The hybrid metal-organic \quad molecular beam epitaxy (hMBE) technique has been shown to exactly control stoichiometry, but requires understanding how to interpolate the growth conditions between the end members $A$'$B$O$_{\mathrm{3}}$ and \textit{AB}O$_{\mathrm{3}}$. Using the example of La$_{\mathrm{1-x}}$Sr$_{\mathrm{x}}$VO$_{\mathrm{3}}$, the two-dimensional growth parameter space spanned by the flux of the metal-organic precursor vanadium oxytriisopropoxide and composition, $x$, can be mapped quickly with a single calibration sample using \textit{in situ} reflection high-energy electron (RHEED), which is corroborated by X-ray diffraction and atomic force microscopy.[1] This strategy enables the identification of growth conditions that allow the deposition of stoichiometric perovskite oxide films with random $A$-site cation mixing. In particular, at the quantum critical point that separates the Mott-insulator (LaVO$_{\mathrm{3}})$ from a strongly-correlated Fermi-liquid (SrVO$_{\mathrm{3}})$ this ability to produce ultrahigh quality films allows the novel competition between disorder-effects and electron-electron interactions to be revealed. This work was supported by the Dept. of Energy (DE-SC0012375). [1] M. Brahlek, \textit{et al} Appl. Phys. Lett. 109, 101903 (2016)