Influence of samaria doping on the resistance of ceria thin films and its implications to the planar oxygen sensing devices

Journal Article · Wed May 27 00:00:00 EDT 2009 · Sensors and Actuators. B, Chemical, 139(2):380-386

DOI:https://doi.org/10.1016/j.snb.2009.03.021· OSTI ID:958449

Gupta, Shilpi; Engelhard, Mark H; Shutthanandan, V; Nachimuthu, Ponnusamy; Jiang, Weilin; Saraf, Laxmikant V; Thevuthasan, Suntharampillai; Prasad, Shalini

In order to evaluate and analyze the effect of samarium (Sm) doping on the resistance of cerium oxide, we have grown highly oriented samaria doped ceria (SDC) thin films on sapphire, Al2O3 (0001) substrates by using oxygen plasma-assisted molecular beam epitaxy (OPA-MBE). The film growth was monitored using reflection high-energy electron diffraction (RHEED) which shows two-dimensional growth throughout the deposition. Following growth, the thin films were characterized by X-ray photoelectron spectroscopy (XPS), high-resolution X-ray diffraction (HRXRD), and Rutherford backscattering spectrometry (RBS). XPS depth-profile shows Sm atoms are uniformly distributed in ceria lattice throughout the bulk of the film. The valence states of Ce and Sm in doped thin films are found to be Ce4+ and Sm3+, respectively. HRXRD shows the samaria doped ceria films on Al2O3(0001) exhibit (111) preferred orientation. Ion-channeling in RBS measurements confirms high quality of the thin films. The resistance of the samaria doped ceria films, obtained by two probe measurement capability under various oxygen pressure (1mTorr-100Torr) and temperatures (623K to 973K), is significantly lower than that of pure ceria under same conditions. The 6Sm% doped ceria film is the optimum composition for highest conductivity. This is attributed to the increased oxygen vacant sites in fluorite crystal structure of the epitaxial thin films which facilitate faster oxygen diffusion through hopping process.

• Research Organization: Pacific Northwest National Lab. (PNNL), Richland, WA (United States). Environmental Molecular Sciences Lab. (EMSL)
• Sponsoring Organization: USDOE
• DOE Contract Number: AC05-76RL01830
• OSTI ID: 958449
• Report Number(s): PNNL-SA-62921; 25414a; KP1504020; TRN: US201002%%150
• Journal Information: Sensors and Actuators. B, Chemical, 139(2):380-386, Vol. 139, Issue 2
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
CERIUM OXIDES
CRYSTAL STRUCTURE
ELECTRON DIFFRACTION
FLUORITE
GRAIN ORIENTATION
ION CHANNELING
MOLECULAR BEAM EPITAXY
OXYGEN
PROBES
REFLECTION
RUTHERFORD BACKSCATTERING SPECTROSCOPY
SAMARIUM
SAPPHIRE
SUBSTRATES
THIN FILMS
VALENCE
X-RAY DIFFRACTION
X-RAY PHOTOELECTRON SPECTROSCOPY
oxygen gas sensor
resistance
ionic conduction
samaria
ceria
thin films
OPA-MBE
Environmental Molecular Sciences Laboratory