Ultrathin film growth of iron oxides on YSZ(001) and (111)

We use low energy electron microscopy (LEEM) and low energy electron diffraction (LEED) to study in real time the growth of iron oxides on the (001) and (111) surfaces of yttria{\-}stabilized zirconia (YSZ). Investigations of the FeO$_{x}$-YSZ system are motivated by its use as a working oxide for thermochemical fuel production via splitting of H$_{2}$O and CO$_{2}$. LEED patterns obtained from YSZ(001) during Fe deposition in $\sim $10$^{-6}$~Torr O$_{2}$ at 600\r{ }C and above indicate first-layer growth of FeO(111) and second-layer growth of Fe$_{2}$O$_{3}$(0001). LEEM imaging shows highly anisotropic first-layer growth into four non-equivalent domains (two rotations and two stacking orientations). Distinct LEEM-IV (intensity-voltage) spectra are obtained for the two stoichiometries providing unique fingerprints of the observed oxide phases. On YSZ(111), growth $>$800\r{ }C in O$_{2}$ is similar to (001) in that FeO is observed in the first layer and Fe$_{3}$O$_{4}$ in the second. Sandia is a multi{\-}program laboratory operated by Sandia Corporation, a subsidiary of Lockheed Martin, for the U.S. DOE's NNSA under contract DE{\-}AC0494AL85000. Funding was provided through Sandia's LDRD Office.