  Water-soluble sacrificial layers based on epitaxially-grown, single
crystalline (Ca, Sr, Ba)3Al2O6 layer are widely used for creating free-standing
perovskite oxide membranes. However, obtaining these sacrificial layers with
intricate stoichiometry remains a challenge, especially for molecular beam
epitaxy (MBE). In this study, we demonstrate the hybrid MBE growth of
epitaxial, single crystalline SrTiO3 films using a solution processed,
amorphous SrCa2Al2O6 sacrificial layer onto SrTiO3 (001) substrates. Prior to
the growth, the oxygen plasma exposure was used to first create the crystalline
SrCa2Al2O6 layer with well-defined surface crystallinity. Utilizing reflection
high energy electron diffraction, x-ray diffraction, and atomic force
microscopy, we observe an atomic layer-by-layer growth of epitaxial, single
crystalline SrTiO3 film on the SrCa2Al2O6 layer with atomically smooth
surfaces. The SrCa2Al2O6 layer was subsequently dissolved in de-ionized water
to create free-standing SrTiO3 membranes that were transferred onto a
metal-coated Si wafer. Membranes created with Sr-deficiency revealed
ferroelectric-like behavior measured using piezo force microscopy whereas
stoichiometric films remained paraelectric-like. These findings underscore the
viability of using ex-situ deposited amorphous SrCa2Al2O6 for epitaxial, single
crystalline growth, as well as the importance of point defects in determining
the ferroic properties in membranes.
