Self-regulated growth of CaVO3 by hybrid molecular beam epitaxy

Abstract

The authors report on the growth of stoichiometric CaVO3 thin films on LaSrAlO4 (001) using hybrid molecular beam epitaxy approach, whereby the metalorganic vanadium oxytriisopropoxide (VTIP) and Ca was cosupplied from a gas injector and a conventional effusion cell, respectively. Films were grown using a fixed Ca flux while varying the VTIP flux. Reflection high energy electron diffraction, x-ray diffraction, atomic force microscopy, energy-dispersive x-ray spectroscopy, and high resolution transmission electron microscopy were employed to relate film quality to growth conditions. A wide growth window was discovered in which the films were stoichiometric and film lattice parameter was found independent of the Ca/VTIP flux ratio, allowing more than 10% unintentional deviation in the Ca flux while maintaining stoichiometric growth conditions. Films grown within the growth window showed atomically smooth surfaces with stepped terrace morphology and narrow rocking curves in x-ray diffraction with a full width of half maximum of 8 arc sec, similar to that of the substrate. For growth conditions outside of this window, excess Ca and V nonstoichiometric defects were incorporated into the lattice. The effect of film microstructure and stoichiometry on temperature dependent electrical conductivity is discussed. The ability to produce high quality CaVO3 films without precise control of cation fluxes opens a robust synthesis route to explore the intrinsic physics of strongly correlated metals with reduced dimensionality.