Conductivity of Oriented Samaria-Doped Ceria Thin Films Grown by Oxygen-Plasma-Assisted Molecular Beam Epitaxy

We have used oxygen-plasma-assisted molecular beam epitaxy to grow highly oriented Ce 1-x Sm x O 2-δ films on single-crystal c-Al 2 O 3 . The samarium concentration x was varied in the range of 1-33 atom %. It was observed that dominant (111) orientation in Ce 1-x Sm x O 2-δ films can be maintained up to about 10 atom % samarium concentration. Films higher than 10 atom % Sm concentration started to show polycrystalline features. The highest conductivity of 0.04 S cm -1 at 600°C was observed for films with ∼5 atom % Sm concentration. A loss of orientation, triggering an enhanced grain-boundary scattering, appears to be responsible for the decrease in conductivity at higher dopant concentrations.