Properties Of CeO2 Thin Films Research Articles

First-principles quantum analysis of structural, optoelectronic, and thermophysical properties of Co/Ni doped ceria Ce1−xTmxO2 (Tm=Co, Ni) for solar cell applications

The properties of CeO2 thin films, such as their memory store capabilities, visual transparency, chemical and thermal durability, adjustable energy band topologies, and high oxygen storage capacity have captured the attention of scientists. The energy band dispersions for Ce1−xTmxO2 (Tm = Co, Ni; x = 12.5%) are calculated to get insight into the characteristics of the materials under investigation. The anticipated energy bandgaps for Ce1−xCoxO2 and Ce1−xNixO2 are 2.6 and 2.7 eV, respectively, in the spin ↑ channel. However, both compounds show metallic character in inspin ↓ channel. The phenomena of photon absorption/dispersion by the host materials can be elucidated using dielectric function εω of Ce1−xTmxO2 (Tm = Co, Ni; x = 12.5%). Significant photon absorption can be noted in UV and IR regions for Ce1−xTmxO2 (Tm = Co, Ni; x = 12.5%) in spin ↑ and spin ↓ channels, respectively. Ce1−xTmxO2 (Tm = Co, Ni; x = 12.5%) exhibits a minimal photon reflection, approximately 15%. Ce1−xNixO2 shows excellent thermoelectric characteristics as its ZT value is high (1.8 at 1000K) compared to Ce1−xCoxO2. Based on their thermodynamic properties, Ce1−xTmxO2 (Tm = Co, Ni; x = 12.5%) are thermodynamically stable compounds.

Crack formation and optical properties in 175 MeV Au13+ ion beam irradiated CeO2 thin films

CeO2 thin films have been deposited on fused silica substrates using RF-sputtering technique. 175 MeV Au13+ ions beam with two different fluences, 1 × 1012 ions/cm2 and 5 × 1012 ions/cm2, have been applied to modify the structural, surface and optical properties of CeO2 thin films. X-ray diffraction (XRD), atomic force microscopy (AFM), UV–visible absorption and photoluminescence (PL) measurements have been performed to investigate the 175 MeV Au13+ ion-irradiation induced changes in CeO2 thin films. The irradiated films show the formation of nanocrystalline granulizes on the film surface. The mud like cracks have been evolved at the ion-fluence of 5 × 1012 ion/cm2. The modifications in the optical and structural properties and the formation of cracks have been studied under the light of 175 MeV Au13+ ion irradiation and energy loss process into CeO2 lattice.

Impact of Molarity on the Structural, Morphological and Optical Properties of CeO2 Thin Films Prepared by Spray Pyrolysis Technique

Impact of Molarity on the Structural, Morphological and Optical Properties of CeO2 Thin Films Prepared by Spray Pyrolysis Technique

Influence of manganese rate on structural, optical and electrochemical properties of CeO2 thin films deposited by spray pyrolysis: Supercapacitor applications

The present work aimed to investigate the electrochemical properties of ITO substrates in propylene carbonate (PC) with 0.5 mol/L lithium perchlorate (LiClO4) medium in the presence of elaborated thin films of cerium dioxide pure and doped with manganese at varying percentages. Ce1–xMnxO2 (x = 0 wt%, 2 wt%, 4 wt% and 6 wt%) were successfully deposited by the spray pyrolysis (SP) technique on the glass substrate and ITO at 450 °C. The effects of manganese (Mn) doped thin films Ce1–xMnxO2 were studied and investigated by using different analyses namely X-ray diffraction (XRD) analysis, Raman spectroscopy method, UV–Vis spectrophotometer technique, atomic force microscopy (AFM) analysis and electrochemical properties. XRD data obtained present a polycrystalline with a face-centred cubic structure of fluorite type. Raman results of undoped and Mn doped thin films show two peaks at 465 and 600 cm−1, due to the formation of extrinsic oxygen vacancies by the incorporation of Mn into Ce1–xMnxO2 matrix. Energy dispersive spectroscopy (EDS) data show the presence of Ce, O, and Mn elements in the elaborated films. The AFM results reveal that the surface roughness decreases with increasing Mn rate. Further, band gap energy of thin films decreases with increasing in Mn rate due to the formation of defect state between valence and conduction band. The storage capacity of the elaborated Ce1–xMnxO2/ITO/PC + LiClO4 electrode reaches a maximum of 1.997 mF in the presence of 6 wt% of Mn.

Analysis of gamma dose dependent nanostructure, morphological, optical and electrical properties of CeO2 thin films

The structural, morphological, optical and electrical properties of CeO2 thin films deposited on glass substrate using spin coating technique are studied with and without gamma irradiation. The prepared samples were gamma irradiated with 60Co at room temperature with dose range from 0 to 100 kGy. The pristine and gamma exposed samples were analyzed by X-ray diffraction (XRD), field emission scanning electron microscope (FESEM), energy dispersive X-rays (EDX), UV–Vis Spectroscopy, photoluminescence (PL) and Hall measurements. XRD results confirmed the face-centered cubic phase of CeO2 for all samples and showing the decreased in the crystallinity with gamma irradiation dose values. The FESEM images shows that after gamma exposure, the CeO2 thin films surface became compressed, smooth and uniform. UV–Vis Spectroscopy determined that the shifting of energy band gap values accredited by creating or eradication of induced defects inside the energy band gap. PL peaks appeared in pristine and irradiated thin films can be allocated to the oxygen related defects. The mobility, electrical resistivity and carrier concentration were estimated for all sample by Hall measurements. It was found that the electrical properties, such as an increase in the number of carrier concentration and the decrease in the resistivity, of the CeO2 thin films were improved with gamma rays irradiation. The study successfully demonstrates that CeO2 thin films is a potential candidate to detect gamma radiation for dosemetric application.

Tuning of structural, optical, and impedance properties of CeO2 thin films by incorporation palladium ions

Thin films of pure and Pd-doped CeO2 with different doping concentrations deposited via sol gel spin coating technique. The influence of Pd doping level (0, 2, 4 and 8%) on the physical characteristics was investigated of nanocrystalline CeO2 thin films. From X-ray diffraction (XRD) pattern, the (111) preferred oriented CeO2 cubic structure was observed in all thin films. Crystallite size decreased with increasing Pd doping from 67.41 to 41.67 nm, whereas the crystallinity of thin film increased with doping level. The field emission scanning electron microscopy (FESEM) analyses showed the uniform distribution of nanospherical grains, decreased in size and agglomerated of nanocrystallite with increasing Pd doping. Energy-dispersive X-ray (EDX) results revealed that the weight percentage of un-doped and Pd-doped CeO2 thin films was confirmed and very close to that in mixed precursor. The energy bandgap values of prepared thin films were measured as a function of Pd doping centration using UV–Vis spectroscopy. Energy bandgap as well as the transmission of CeO2 were increased with Pd doping level. The PL spectra show noticeable variations in intensity and red shift of the emission peaks upon Pd doping. These effects have been associated with structural modifications and defect states Pd-doped CeO2 thin films. The Nyquist plots suggest that the ionic conductivity through the grains is responsible in the conduction mechanism of the thin films.

Effect of annealing temperature on the structural and magnetic properties of CeO2 thin films

CeO2 thin films were deposited on silicon(100) substrates via a radio frequency magnetron sputtering technique and subsequently annealed with a 10 °C/min-heating step in a vacuum tube furnace between 400 °C and 800 °C under an argon atmosphere for 2 h to generate a higher concentration of oxygen vacancies. All samples were characterized to determine their phase, morphology, valence states and magnetic properties using grazing incidence X-ray diffraction, Raman spectroscopy, field emission scanning electron microscopy, X-ray photoelectron spectroscopy (XPS) and vibrating sample magnetometry. All samples showed X-ray diffraction peaks corresponding to a cubic fluorite structure with no evidence of impurities. The cubic structure was further confirmed by observation of the Ce-O8 vibrational unit stretching mode of F2g associated with the CeO2 structure. Evidence for defect/oxygen vacancies was found in the Raman results. The morphology of all films showed aggregated nanoparticles amongst columnar structures with average particle sizes increasing from ~59 nm to ~68 nm when annealed at temperatures from 400 °C to 800 °C. The thicknesses of the CeO2 films decreased from 327 ± 5 nm to 295 ± 4 nm with increasing annealing temperature. The presence of Ce4+ and Ce3+/oxygen vacancies in all samples was confirmed using XPS. All CeO2 thin film samples showed weak ferromagnetic behavior with a maximum magnetization value of 27.3 × 103 A/m for a sample annealed at 700 °C. This was approximately 7 times better than that of the as-grown material before annealing. The relationship between higher magnetization values and higher concentrations of oxygen vacancies mediating an exchange mechanism via ferromagnetic coupling was investigated.

Structural, optical and electrical properties of CeO2 thin films simultaneously prepared by anodic and cathodic electrodeposition

CeO2 thin films were deposited on stainless steel (SS) and indium tin oxide (ITO)-coated glass by simultaneous anodic and cathodic electrodeposition, and the influence of negative potential on the formation of ceria films was studied with scanning electron microscopy, X-ray diffraction, Raman spectroscopy, van der Pauw measurements, UV-visible spectroscopy and X-ray photoelectron spectroscopy. The results show that CeO2 films on the anode are slightly affected by the potential, but the particle size, crystal orientation, strain, film thickness, resistivity and Ce(III) content of the films on the cathode increases with increasing potential on the SS substrate. Contradictory to the results of the SS cathode, redshift (Ed changed from 3.95 eV to 3.56 eV and Ei changed from 3.42 eV to 3.04 eV) occurring in the absorption spectrum of CeO2 deposited on the ITO-coated glass cathode indicates that the content of Ce3+ in the cathodic films is dependent on the adopted substrates and decreases as the applied potential is increased.

Role of C Ion Implantation on Structural and Optical Properties of Ceo2 thin Films Deposited on Quartz Substrates

Role of C Ion Implantation on Structural and Optical Properties of Ceo2 thin Films Deposited on Quartz Substrates

Effect of annealing temperature on structural, morphological and optical properties of CeO2 thin films obtained from a simple precursor solution

CeO2 thin films were obtained starting from a simple precursor solution by the sol–gel technique. The precursor solution was prepared by dissolving cerium nitrate in ethanol with lactic acid as stabilizer at room temperature. The as-deposited films were annealed at different temperatures from 250 to 550 °C, in open atmosphere. The effect of annealing temperature on structural, morphological, and optical properties of the films were studied by X-ray diffraction, UV-vis absorbance spectroscopy, Raman spectroscopy, scanning electron microscopy and atomic force microscopy. The results revealed that the annealing temperature plays an important role for improving film properties. X-ray diffraction shows that all films annealed exhibit fluorite cubic structure and increase in the crystalline size from 4.8 to 18.6 nm as the annealing temperature is increased. Raman spectra show a mode at around 463 cm−1, which is attributed to a symmetrical stretching mode of the Ce-8O vibrational unit. Atomic force microscopy images reveal that CeO2 films with higher surface roughness as the annealing temperature increases. The UV-vis spectra show that all the films have high optical transmittance, ~75% in the visible region. In addition, an increase of the band gap energy from 2.96 to 3.24 eV is obtained when the annealing temperature was raised. Fig. a XRD patterns of CeO2 thin films annealed at different temperatures. b (111) interplanar spacing as a function of AT.

Impact of microwave annealing on CeO2 thin films sputtered on (1 1 1) Si

The impact of the microwave annealing (MA) on the crystallinity and on the electrical properties of CeO2 thin films has been investigated by Raman Spectroscopy, capacitance–voltage (C–V) measurements and current–voltage (I–V) measurements. This paper highlights the influence of the temperature, time, and atmosphere used for the MA on the crystallinity, the surface quality, and the oxidation state of Ce of CeO2 thin films. At the same time, the impact of microwave annealing on the flatband voltage (VFB) and the interface traps density (Dit) is studied by C–V measurements. Moreover, the leakage current is compared before and after the microwave annealing. Therefore, this paper shows a sharp improvement of the CeO2 film crystallinity and a decrease in leakage current after a microwave annealing performed at 900°C for 5min under nitrogen atmosphere. To our knowledge, it is the first time that the impact of MA on CeO2 films is reported.

Rapid thermal annealing of cerium dioxide thin films sputtered onto silicon (111) substrates: Influence of heating rate on microstructure and electrical properties

The impact of the heating rate (HR) of a Rapid Thermal Annealing (RTA) on the crystallinity and on the morphology of CeO2 thin films has been investigated by Raman Spectroscopy (RS), Photoluminescence (PL), Scanning Electron Microscopy (SEM), Energy Dispersive Spectroscopy (EDS), and tapping mode Atomic Force Microscopy (AFM). The electrical properties of CeO2 thin films have also been studied with the Conductive AFM mode. This paper highlights the importance of the heating rate value used during an RTA on crystalline quality, morphology and on the electrical properties of the CeO2 layer. In fact, the best crystallinity with a good morphology and a high resistivity has been obtained for a CeO2 layer sputtered on (111) Si substrate and post-annealed at 1000°C for 30s with an HR of 25°C/s.

Influence of Surface Pre-Treatment On Electrochemical Properties of CeO2 thin Films Deposited by R.F. Sputtering On AA7075 Aluminum Alloy

Nanocrystalline CeO2 coatings were grown on AA7075 aluminum alloy substrates using RF magnetron sputtering and analyzed as protective barriers inhibiting the pitting corrosion reactions in chloride medium. Special attention was placed in the effect of alkaline and acid pretreatments on structural, morphological and electrochemical properties of CeO2 coatings. For this purpose, a CeO2 target under Ar atmosphere was used at room temperature employing different powers. The as-prepared films were characterized by Spectroscopic Ellipsometry (SE), X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM) and electrochemical techniques such as polarization resistance (Rp) and potentiodynamic curves. The thickness of the as-deposited samples was quite different varying from 114 to 1575 nm for 40 and 120 W, respectively. The obtained coatings were composed of CeO2 particles with uniform, porous and crack-free film and the typical crystalline face centered cubic structure. The corrosion resistance of CeO2 coatings increases proportionally to the applied chemical pretreatment. Additionally, it was found that the electrochemical behavior has a direct relation with the pretreatment concentration but not with the thickness coatings.

The influence of Er3+ doping on the structural and optical properties of CeO2 thin films grown by PED

Erbium doped CeO2 thin films were deposited on both Corning glass substrates and indium doped tin oxide (ITO) coated glass substrates by pulsed e-beam deposition (PED) method at room temperature. Structural features of Er doped CeO2 thin films were studied with X-ray diffraction (XRD) and micro-Raman spectra. The XRD patterns of all films showed polycrystalline nature and cubic crystalline structure. Raman active peaks for both undoped CeO2 and Er doped CeO2 films were determined at ∼465cm−1. The Raman shift observed in this study can also be assigned to Raman active modes of CeO2 that are shifted from the original position due to different doping concentration. The optical properties of CeO2 films and Er doped CeO2 films, which were determined from transmittance and reflectance measurements at room temperature, were very similar in character. The refractive indices and extinction coefficients, which were calculated from 3.5 to 1.25eV (300–1000nm), were between 1.5–3 and 0.05–0.2, respectively. The optical band gaps were deduced from the absorption coefficient according to solid band theory. The electrochromic measurements revealed that 2% Er doped CeO2 films grown on ITO+WO3 substrates had highest charge density compared to the other samples. Long-time cyclic voltammetry (CV) and chronoamperometry (CA) measurements were carried out to investigate the stability of this film.

Influence of substrate temperature on the properties of CeO2 thin films by simple nebulizer spray pyrolysis technique

Cerium oxide thin films are coated on glass substrates by nebulizer spray pyrolysis technique using cerium nitrate as a source material. Their crystallographic structures, surface morphology, optical properties and I–V characteristics are studied as a function of substrate temperature (300–500 °C). XRD is used to estimate the crystallographic texture, grain size, strain and lattice constants. All the films exhibit a cubic fluorite structure with different preferred orientations depending on the preparation conditions. Optical analysis reveals that the films are transparent (70%) in the visible region. The optical bandgap (Eg) is calculated in the range 3.28–3.52 eV. The optical parameters like absorption coefficient, extinction coefficient, packing density and refractive index are calculated for different substrate temperatures. SEM images exhibit golf-ball like morphology with small cracks and pores. The maximum conductivity obtained is 2.90×10−6 S/cm at 400 °C.

Structural Characterizations and Optical Properties of CeO2 Thin Films Prepared by Laser Molecular-Beam Epitaxy

Epitaxial CeO2 thin films were deposited on Si (111) substrates by laser molecular-beam epitaxy (LMBE). Surface roughness, crystalline structure and optical constants were characterized by in situ reflection high energy electron diffraction (RHEED), atomic force microscopy (AFM), Raman spectroscopy and spectroscopic ellipsometry. AFM showed that the epitaxial CeO2 film has a quite smooth surface with a root mean square roughness of 0.563 nm over a 2 μm × 2 μm area. Raman spectroscopy results indicated good crystallinity of the thin film. Refractive index n and extinction coefficient k of the thin films were calculated in the wavelength region of 370–1000 nm and the values were found to gradually decrease from 2.90 and 0.0321 at 370 nm to 2.35 and 0.0017 at 1000 nm, respectively. The direct and indirect optical band gaps of the film were estimated to be around 3.17 and 2.64 eV, respectively.

Improvement of the surface roughness and sensing properties of cerium dioxide thin film by chemical mechanical polishing

Cerium dioxide (CeO2) is one of the most widely used materials for oxygen gas sensors. The surface roughness of CeO2 thin films must be improved because the electrical and sensing properties of CeO2 thin films are determined by these characteristics. The authors selected chemical mechanical polishing (CMP) processing for improving the surface roughness of CeO2 thin films. The authors examined the removal rate and surface roughness of spin coated CeO2 thin films with a change of CMP process parameters such as pressure (down force) and velocity (table speed). An optimized process condition, reflected by not only the surface roughness with a hillock-free surface but also an excellent removal rate with good uniformity, was obtained. The effects of the improved surface roughness on the sensing property of CeO2 thin films were also confirmed. The authors obtained improved sensitivity of CeO2 thin films for oxygen sensors after the CMP process by the improved surface morphology. Therefore, the authors concluded that the sensing property of CeO2 thin film was strongly dependent on the surface roughness of CeO2 thin films by using a CMP process.

Electrical Conductivities of (CeO2)1−x(Y2O3)x Thin Films

Electrical properties of CeO2 thin films of different Y2O3 dopant concentration as prepared earlier were studied using impedance spectroscopy. The ionic conductivities of the films were found to be dominated by grain boundaries of high conductivity as compared with that of the bulk ceramic of the same dopant concentration sintered at 1500°C. The film grain‐boundary conductivities were investigated with regard to grain size, grain‐boundary impurity segregation, space charge at grain boundaries, and grain‐boundary microstructures. Because of the large grain boundary and surface area in thin films, the impurity concentration is insufficient to form a continuous highly resistive Si‐rich glassy phase at grain boundaries, such that the resistivity associated with space‐charge layers becomes important. The grain‐boundary resistance may originate from oxygen‐vacancy‐trapping near grain boundaries from space‐charge layers. High‐resolution transmission electron microscopy coupled with a trans‐boundary profile of electron energy loss spectroscopy gives strong credence to the space‐charged layers. Since the conductivities of the films were observed to be independent of crystallographic texture, the interface misorientation contribution to the grain‐boundary resistance is considered to be negligible with respect to those of the impurity layer and space‐charge layers.