Thermal stability of CeO_2/ZrO_2 multilayer thin films prepared by pulsed laser deposition

摘要

Multilayers of CeO_2/ZrO_2 thin films were deposited on Si (100) substrates using pulsed laser deposition at an optimized oxygen partial pressure of 3x10~(-2) mbar and at room temperature. The CeO_2 layer thickness was 10 nm, while the ZrO_2 layer thickness was varied as 10, 20 and 30 nm. CeO_2 and ZrO_2 layers were deposited alternately to obtain 25 bilayers. High temperature x-ray diffraction (HTXRD) results showed that the multilayer films had cubic ceria and tetragonal ZrO_2 Thermal expansion coefficients were calculated for CeO_2 and t-ZrO_2 and found to increase with the decrease of ZrO_2 layer thickness. The cross sectional transmission electron microscopy (XTEM) of CeO_2/ZrO_2 multilayer also indicated that ceria was found to be in cubic phase while zirconia contained predominantly tetragonal phase along with cubic phase in thermally annealed specimen.