Structural and electrical study of samarium doped cerium oxide thin films prepared by e-beam evaporation

Abstract

Samarium doped cerium oxide (Sm0.15Ce0.85O1.925, SDC) thin films were grown on the Alloy 600 (Fe–Ni–Cr) and optical quartz (SiO2) substrates using e-beam deposition technique. Formed SDC thin films were characterized using different X-ray diffraction (XRD) techniques, scanning electron microscope (SEM), energy-dispersive spectrometry (EDS) and impedance spectroscopy. The deposition rate of formed SDC thin films was changed from 2Å/s to 16Å/s.XRD analysis shows that all thin films have a cubic (FCC) structure and repeat the crystallographic orientation of the initial powders evaporated with different deposition rate and on different substrates. The crystallite size increases from 7.7nm to 10.3nm and from 7.2nm to 9.2nm on Alloy 600 substrate and optical quartz (SiO2) substrate respectively as the thin film deposition rate increases. SEM images indicate a dense and homogeneous structure of all formed SDC thin films.The ionic conductivity depends on thin films density and blocking factor. The best ionic conductivity (σg=1.34Sm−1 and σgb=2.29Sm−1 at 873K temperature, activation energy ΔEg=0.91eV and ΔEgb=0.99eV) was achieved for SDC thin films formed at 4Å/s deposition rate. It was found that the highest density (5.25g/cm3) and the lowest relaxation time in grain (τg =9.83×10−7s), and the lowest blocking factor (0.39) is in SDC thin films formed at 4Å/s deposition rate. The deposition rate influences the stoichiometry of the formed SDC thin ceramic films.