(T = Mn, Ru)

Double-layered Ruddlesden-Popper oxides are known to exhibit a strong correlation between octahedral distortion and physical properties. Using low-energy electron diffraction (LEED) and high-resolution electron energy loss spectroscopy (HREELS), we have investigated the surface structural and physical properties of Sr₃T₂O₇ (T = Mn, Ru). While surface RuO₆ octahedron in Sr₃Ru₂O₇ has both rotation (~ 12°) and tilt (~ 3°), our LEED – IV analysis reveals that MnO₆ octahedron in Sr₃Mn₂O₇ has a similiar rotation (~ 11°) but no tilt. HREELS data suggest that both the surface of Sr₃Mn₂O₇ and Sr₃Ru₂O₇ are semiconducting but for different reasons. The implication of these findings will be discussed.