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Rare-earth element-doped BiFeO3 has an ultrahigh piezoelectric response near the morphotropic phase boundary (MPB), making it a promising substitute for toxic lead-based piezoelectric materials. As a ferroelectric–antiferroelectric MPB, its microscopic mechanism, especially the contribution of each phase to the piezoelectric performance, is still unclear. In this work, the origin of the giant piezoelectric response of Sm-doped BiFeO3 thin films was studied by combining nanoscale in situ electric field experiments and atomic-resolution electron microscopy. Two independent reversible phase transitions were found under an external electric field: a phase transition between the polar and nonpolar phases and a phase transition between the polar and antipolar phases. Calculations indicated that the enhancement of the piezoelectric response at the MPB originated from these two reversible phase transitions, which were realized via the nucleation of the nanoscale new phase and the motion of the phase boundary under the external electric field. The above results provide deeper insight into the mechanism of the electromechanical response near the ferroelectric–antiferroelectric MPB in rare-earth element-doped BiFeO3 thin films. [ABSTRACT FROM AUTHOR]

Even though the great interest in studying the near-infrared light emission due to Er3+ ions for telecommunication purposes, efficient visible radiation can be achieved from many different rare-earth (RE) ions. In fact, visible and/or near-infrared light emission takes place in RE-doped wide bandgap semiconductors following either photon or electron excitation, suggesting their technological potential in devices such as light-emitting diodes (LED's) and flat-panel displays, for example. Taking into consideration these aspects, the present contribution reports on the investigation of AlN, BeN, GeN, and SiN thin films doped with samarium. The samples were prepared by sputtering and as a result of the deposition method and conditions they present an amorphous structure and Sm concentrations in the low 0.5 at. %. After deposition, the samples were submitted to thermal annealing treatments and investigated by different spectroscopic techniques. A detailed examination of the experimental data allowed to identify optical transitions due to Sm3+ and Sm2+ ions as well as differences in their mechanisms of photon excitation and recombination. Moreover, it is shown that the Sm-related spectral features and emission intensity are susceptible, respectively, to the atomic environment the Sm3+/Sm2+ ions experience and to the presence of non-radiative recombination centers. [ABSTRACT FROM AUTHOR]

We investigated the flat band voltage (VFB) modulation by insertion of lanthanum oxide (La2O3) into hafnium oxide (HfO2) gate dielectrics. The properties of La2O3/HfO2 nanolaminates were precisely modulated by controlling the position of La2O3 layer at bottom, middle, or top using atomic layer deposition. When the La2O3 layer was positioned closer to the interface (bottom), the reduction in VFB shift was more effective than the other two cases (middle and top). From our experimental results, we propose that the main mechanism of VFB modulation using La2O3 layer is dipole moment formation at an interfacial layer between high k gate dielectric and Si substrate. [ABSTRACT FROM AUTHOR]

The reproducible forming-free resistive switching (RS) behavior in rare-earth-oxide Gd2O3 polycrystalline thin film was demonstrated. The characteristic of this forming-free RS was similar to that of other forming-necessary binary RS materials except that its initial resistance starts from not the high resistance state (HRS) but the low resistance state (LRS). An ultrahigh resistance switching ratio from HRS to LRS of about six to seven orders of magnitude was achieved at a bias voltage of 0.6 V. Mechanism analysis indicated that the existence of metallic Gd in the Gd2O3 films plays an important role in the forming-free RS performance. Our work provides a novel material with interesting RS behavior, which is beneficial to deepen our understanding of the origin of RS phenomenon. [ABSTRACT FROM AUTHOR]

This article deals with strain relaxation in SmNiO3 epitaxial films deposited by chemical vapor deposition on SrTiO3 substrates. Thanks to x-ray reciprocal space mapping, we demonstrate that the strain relaxation is driven both “chemically” and “mechanically” by the formation of oxygen vacancies and misfit dislocations, respectively. Besides, a careful interpretation of the resistivity measurements allows us to highlight a correlation between the formation of oxygen vacancies, the stabilization of Ni3+, and the metal-insulator transition in the SmNiO3 films. Furthermore, using coplanar and grazing incidence diffraction, the shape of the strain gradient within the films is retrieved. This latter is calculated using a versatile scattering model involving B-spline functions. Finally, particular planar faults (Ruddlesden–Popper faults) that give rise to extended diffuse scattering on transverse scans are analyzed using a recent phenomenological model. [ABSTRACT FROM AUTHOR]

Rare-earth oxides are among the materials which are presently studied as possible replacements of amorphous silicon dioxide as gate insulators in nanometric Si devices; in fact, they generally exhibit high values of the dielectric constant (“high κ”), a necessary requirement to obtain a high capacitance with layer thickness greater than the value below which tunneling currents become unacceptably high. Lu2O3 is one of the rare-earth oxides which may have the required properties in view of its quite high values of κ and forbidden band gap. Since the envisaged dielectric layers are only a few nanometers thick, a description and a physical understanding of the atomic and electronic structure of the interface are of great importance. In this paper, we report a study by synchrotron radiation photoemission and transmission electron microscopy of the growth of Lu2O3 on Si(001). Thanks to the high spectral and spatial resolution, we provide clear evidence of a rather complex structure in which all silicon suboxides and SiO2 are present at the same time, along with a silicatelike phase and Lu2O3 itself; moreover, some grains and both crystalline and amorphous portions are present. In the photoemission experiment, the contribution of the Si surface to the core level line shapes has been taken into account; in the electron microscopy measurements, we present line scans on the nanometer scale of O, Si, and Lu concentrations and a Fourier transform discussion of the structure of the crystalline portions of the overlayer. The valence band discontinuity, which is measured in situ and is relative to the structurally well characterized interface, is found to be 3.16±0.16 eV. These findings are discussed in relation to the suitability of Lu2O3 as a high-κ dielectric and in the context of available theoretical predictions of thermodynamic stability versus the formation of silicon oxide, silicates, and silicides and of the band discontinuity problem. [ABSTRACT FROM AUTHOR]

The structural, magnetic, and transport properties of La0.7(Ca1-ySry)0.3MnO3 films, deposited on a LaAlO3 (001) single crystalline substrate by rf-magnetron sputtering using “soft” (or powder) targets, have been investigated. It was found that at 0.3≤y≤0.5 both the rhombohedral (R3c) and the orthorhombic (Pnma) crystal phases in the form of nanoscale clusters are coexistent at room temperature. The observed structural clustering is accompanied by two-stage magnetic and electronic transitions, and governed by a nonuniform distribution of the lattice strain through the film. It was shown that for the films with 0≤y≤0.5 the nonlinear (almost parabolic) MR(H) dependence is typical while, for 0.65≤y≤1.0, the linear MR(H) behavior is observed at room temperature. The magnetotransport properties of films are explained within the framework of field-dependent activation-energy model. The magnetic phase diagram for La0.7(Ca1-ySry)0.3MnO3 thin-film system is also presented. [ABSTRACT FROM AUTHOR]

Polymer‐based hydrophobic coatings degrade in response to high temperatures or abrasion. Rare‐earth oxides (REOs) as a ceramic material may provide more robust surfaces whose hydrophobicity is maintained due to their specific electron configuration. It has been also shown that REO thin films are stable on the surface of bare materials used in the aerospace industry (i.e., aluminum and titanium alloys). Hence, coating or doping of Al2O3 and TiO2 surfaces with REO might be promising both theoretically and practically. Following our previous studies on cerium‐doped Al2O3 and TiO2, in this work, the density functional theory (DFT) method is applied to investigate the possibility of tuning the wettability of commonly used hydrophilic Al2O3 by surface doping with neodymium (Nd) and europium (Eu). The results indicate that Nd and Eu segregate to the (0001) surface of Al2O3 and thermodynamically stable oxygen termination of dopant is formed. A significant increase in the static water contact angle provide a valuable opportunity for the RE element surface modification of Al2O3, in order to achieve hydrophobicity. [ABSTRACT FROM AUTHOR]

The bulk polycrystalline samples with nominal compositions Mg1-x(Eu2O3)x/2B2 and Mg1-x(Pr6O11)x/6B2 (where x=0.0, 0.01, 0.02, 0.03, 0.04, and 0.05) have been prepared via standard solid-state reaction route. The x-ray diffraction (XRD) results of both series of materials reveal the presence of secondary phases MgO and REB6(RE=Eu/Pr) besides the main hexagonal phase of MgB2. The magnetic and electrical measurements show that transition temperatures (Tc) of both Eu2O3 and Pr6O11-doped MgB2 samples decrease from 39 to 37 K when values of x increase from 0.0 to 0.05. Improvement in critical current density (Jc) at 10 K has been observed at higher fields (>4 T) for Eu2O3-doped samples of composition x=0.04 and in entire field range (0–5 T) in the case of Pr6O11-doped samples of composition x=0.03 as compared to the Jc values of other compositions. The Jc values at 5 T field and 10 K of undoped, x=0.03 for Pr6O11-doped and x=0.04 for Eu2O3-doped MgB2 samples are 2.21×103, 1.15×104, and 1.10×104 A/cm2, respectively. Improvement in Hc2 and Hirr has also been observed in doped samples. [ABSTRACT FROM AUTHOR]

The interactions of gaseous hydrogen with rare earth oxides surfaces are important in certain practical processes such as hydrogenation reactions catalysis and metal hydrides formation (for "real life" metals coated with thin oxidation overlayers). It has experimentally been observed that such interactions are significantly affected by the presence of imperfections on these oxide surfaces, especially oxygen vacancies and hydroxyls. In the present DFT calculations, the effects of vacancies and of hydroxyl groups on the chemisorption process of H 2 were studied for the GdO 1.5 , as a model system. Two oxide plane orientations, the (110) and the (111) were compared. It was found that the presence of surface hydroxyls significantly impedes the dissociative chemisorptions step. For the perfect, defect-free oxide surface, hydrogen dissociates heterolytically, forming an hydroxyl and a negatively charged H −δ species. The latter is likely to be the more mobile moiety which penetrates the oxide overlayer and reacts with the metal beneath to form the hydride. However, accumulation of hydroxyls occurs during this chemisorptions step, which finally leads to the blocking of the H 2 heterolytic dissociation route. On the other hand, for the defected, vacancies containing, oxide surfaces, a new type of homolytic dissociation route has been found. This route yields two negatively charged H −δ moieties. This route does not produce any hydroxyls and therefore provides a sustainable channel for H 2 dissociation and penetration into the metal. The above calculation may account for some experimental observations regarding the initial steps of hydrides development. [ABSTRACT FROM AUTHOR]

Ni60 cladding layers added with different amounts of rare-earth CeO 2 , Y 2 O 3 , and La 2 O 3 were prepared on the surface of 6063 aluminum alloys through laser cladding. The effects of such cladding layers on the macroscopic morphology, section morphology, micro-hardness, phase composition, microstructure, and composition distribution of the laser clad Ni-based coating were investigated by performing metallographic microscopy, X-ray diffraction, scanning electron microscopy, energy dispersive spectroscopy, and micro-hardness test. Cladding layers with the optimum rare-earth contents were 4% CeO 2 + Ni60 cladding layer, 5% Y 2 O 3 + Ni60 cladding layer, and 5% La 2 O 3 +Ni60 cladding layer. The main phase composition of the cladding layers included β-NiAl (Cr), Al 3 Ni, AlNi 3 , and Al. The Ni60 cladding layers added with rare-earth oxides produced a chemical reaction that was involved in the cladding process to form stable rare-earth compounds. Ni60 cladding layers added with 4% CeO 2 , 5% Y 2 O 3 , and 5% La 2 O 3 were preferable over those without rare-earth oxides, as the former displayed smoother micro-morphologies without obvious pores and cracks. The dendritic structures of the Ni60 cladding layers were coarse; moreover, many grain segregations that were accompanied by a large number of pores were observed in the local area. By contrast, the Ni60 cladding layers added with rare-earth oxides displayed compact dendritic structures, and the grains were obviously refined. The hardness of the cladding layers from the surface to the substrate was gradually decreased as the cladding layer depth increased. Compared with Ni60 cladding layer, the transitions of Ni, Al, Cr, and other elements in the Ni60 cladding layers added with different amounts of CeO 2 , Y 2 O 3 , and La 2 O 3 were became more observable with increasing depth, and the dilution rate of the cladding layer was reduced. [ABSTRACT FROM AUTHOR]

The comparative analysis of optical characteristics inherent to Er2O3/SiC and Er2O3/por-SiC/SiC structures has been performed. It has been shown that, regardless the substrate on which the Er2O3 film is formed, an increase in the rapid thermal annealing time leads to an improvement in the oxide film composition, with the composition of the Er2O3 film approaching to the stoichiometric one. At the same time, introduction of an additional porous SiC layer leads to a blurring of the oxide film/substrate interface and broadening the photoluminescence band measured in this structure. [ABSTRACT FROM AUTHOR]

An ultrathin gate oxide is needed for future nanoscale technology due to the density of integrated circuits will increase exponentially every two to three years as predicted by Moore's Law. Some problems were occurred in conventional silicon dioxide gate oxide during applications such as high leakage current density, low reliability issues, and undesirable power dissipation. Lanthanide rare earth oxides was attracted as one of potential candidates to replace conventional silicon dioxide due to their superior properties. Each rare earth oxides in lanthanide group was reviewed and discussed in terms of physical, chemical, and electrical properties and also its common deposition methods. Sm 2 O 3 is one of the promising candidate materials among rare earth oxides because of some outstanding properties such as high κ (7–22), high breakdown electric field (5–7 MV cm -1 ), relatively large bandgap (4.33 eV), low leakage current, large conduction offset with Si, high thermal stability, small frequency dispersion, low trapping rate, and low hygroscopic characteristic. The literatures of Sm 2 O 3 was paid particular attention in the last section. The previous deposition methods of the Sm 2 O 3 as gate oxide were reviewed and compared. [ABSTRACT FROM AUTHOR]

Various artificial multilayers consisting of YDy BaCuO/REO/YDyBaCuO films (RE = Y, Gd, Eu, etc.) about 1 μm in a sandwich-type structure are fabricated on oxide-buffered Hastelloy substrates using low-fluorine metalorganic deposition (MOD) method. Superconducting and microscopic performances are studied on composite YDyBaCuO multilayer films with and without intercalated YO, GdO, and EuO ultrathin films. X-ray diffraction (XRD) and field emission scanning electron microscopy (FE-SEM) are used to investigate growth orientation and surface morphology, revealing that multiple superconducting YDyBaCuO thin films separated by an ultrathin REO interlayer have better c-axis orientation, better in-plane and out-plane textures, as well as superior surface morphology. Using this interlayer technology, a significant enhancement of critical current density ( J ) both in self-field and under applied magnetic field is obtained. [ABSTRACT FROM AUTHOR]

Rare earth oxide materials, including thin film coatings, are critically important in magnetic, luminescent and microelectric devices, and few substitutes have been discovered with comparable performance. Thin film coatings from solution are almost unknown for rare earth oxides, likely due to their high activity towards hydrolysis which yields poor quality thin films. The hexamer [Ln6(O)(OH)8(H2O)12(NO3)6]2+ is a rare example of a metal-oxo cluster isolated and stabilized without additional supporting organic ligands. Herein we report a new method for both the preparation and stabilization in non-aqueous media, which makes these clusters valuable precursors for solution-processed thin films. Solution characterization (NMR, small-angle X-ray scattering and Raman spectroscopy) in wet organic solvents indicated that the clusters evolve via a fragmentation and reaggregation process. This is especially true for hexamers of the smaller Ln3+-ions: the higher charge density yields higher hydration rates. This process produced an entirely new hexadecameric cluster formulated Y16O3(OH)24(NO3)18(OSMe2)16(OCMe2)2(H2O)4. The new structure represents an intermediate hydrolysis product on the pathway from hexanuclear clusters to metal oxyhydroxide bulk solid. DMSO solvent ligands displace aqua ligands on the cluster and likely explain the additional stability observed for these clusters in organic solvents. The enhanced cluster stability in DMF and DMSO also enables solution-processing methods to create high quality thin films. [ABSTRACT FROM AUTHOR]

Thin films of rare-earth (RE) oxides (Y2O3, PrOx, Gd2O3, and Dy2O3) were deposited by atomic layer deposition from liquid heteroleptic RE(iPrCp)2(iPr-amd) precursors with either water or ozone as the oxygen source. Film thickness, crystallinity, morphology, and composition were studied. Saturation was achieved with Gd2O3 when O3 was used as the oxygen source at 225 °C and with Y2O3 with both oxygen sources at as high temperature as 350 °C. The growth rates were 0.90-1.3 Å/cycle for these processes. PrOx was challenging to deposit with both oxygen sources but with long, 20 s purges after the water pulses uniform films could be deposited. However, saturation was not achieved. With Dy2O3, uniform films could be deposited and the Dy(iPrCp)2(iPr-amd)/O3 process was close to saturation at 300 °C. The different oxygen sources had an effect on the crystallinity and impurity contents of the films in all the studied processes. Whether ozone or water was better choice for oxygen source depended on the metal oxide material that was deposited. [ABSTRACT FROM AUTHOR]

We report the structural and nonlinear optical properties of Gd 2 O 3 and Dy 2 O 3 doped (K 0.5 Na 0.5 )NbO 3 (KNN) lead-free thin films fabricated by pulsed laser deposition technique. The crystal structure of the films was analyzed by using Rietveld method. The higher tetragonality and improved surface morphology was observed for the rare-earth oxide doped films. The change in crystal structure and tetragonality with these dopants was explained in terms of change in the internal vibration modes of NbO 6 octahedra. The nonlinear optical properties of the films were measured by using single beam Z-scan technique with a continuous wave He–Ne laser (λ = 632.8 nm). All the films have shown a large third-order nonlinear susceptibility and observed to be enhanced for rare-earth doped KNN thin films (|χ (3) | = 2.69 × 10 −3 esu). The maximum nonlinear refractive index, n 2 = 2.02 × 10 −5 cm 2 /W, and nonlinear absorption coefficient, β = 3.48 cm/W, were obtained for Gd 2 O 3 , and Dy 2 O 3 doped films respectively. These results indicate that rare-earth doped KNN thin films are potential candidates for nonlinear photonic applications. [ABSTRACT FROM AUTHOR]

Large-sized (ca. 40 nm) mesoporous Er2O3 thin films are synthesized by using a triblock copolymer poly- (styrene-b-2-vinyl pyridine-b-ethylene oxide) (PS-b-P2VP-b- PEO) as a pore directing agent. Each block makes different contributions and the molar ratio of PVP/Er3+ is crucial to guide the resultant mesoporous structure. An easy and general method is proposed and used to prepare a series of mesoporous rare-earth oxide (Sm2O3, Dy2 O3, Tb2 O3, Ho2O3, Yb2O3, and Lu2O3) thin films with potential uses in electronics and optical devices. [ABSTRACT FROM AUTHOR]

Epitaxial Gd2O3 thin layers with the cubic structure were irradiated with 4-MeV Au2+ ions in the 1013-1015 cm-2 fluence range. X-ray diffraction indicates that ion irradiation induces a cubic to monoclinic phase change. Strikingly, although the energy-deposition profile of the Au2+ ions is constant over the layer thickness, this phase transformation is depth-dependent, as revealed by a combined X-ray diffraction and ion channeling analysis. In fact, the transition initiates very close to the surface and propagates inwards, which can be explained by an assisted migration process of irradiation-induced defects. This result is promising for developing a method to control the thickness of the rare-earth oxide crystalline phases. [ABSTRACT FROM AUTHOR]

By the compound-source molecular beam epitaxy (CS-MBE), GaN:Eu and AlGaN films grown on both Al2O3(0001) and GaAs(100) substrates were prepared. Under RHEED observation, streak RHEED patterns from GaN were observed. This result shows that the surface of the film grown by CS-MBE is atomically flat. From the XRD measurements, for GaN:Eu/Al2O3(0001), the film was oriented to c-axis. On the other hands, for GaN:Eu/GaAs(100), the layer includes both the hexagonal and cubic phases. From the PL measurements, the PL spectra of both GaN:Eu/Al2O3 and GaN:Eu/GaAs(100) showed PL peaks related to Eu3+ ion. For GaN:Eu/GaAs(100), it is possible that part of Eu atom incorporates cubic-GaN site (© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [ABSTRACT FROM AUTHOR]

Low-temperature synthetic methods (the molecular layering and pyrolysis of a liquid aerosol) for the nanostructured oxide films for the gas sensors based on zirconium dioxides and rare earth element (Ce, Y, and Tb) oxides sensitive to the oxygen-impoverished media and ozone have been suggested. It has been shown that the films based on the CeO-ZrO and TbO-YO systems possess the largest sensitivity and a strong response rate (5-6 s) to the reducing media (CO + CO), while the film sensors based on CeO, to ozone. Metal-oxide-semiconductor (MOS) structures that find wide application in semiconductor microelectronics have been obtained based on the synthesized films of rare earth element oxides. [ABSTRACT FROM AUTHOR]

Abstract: This work studies the effects of the deposition parameters on the microstructure and the related residual stress in a rare earth oxide thin film. This study is focused on the yttrium sesquioxide (Y2O3) thin films deposited on Si (100) substrates using the ion beam sputtering technique. This technique allows the control of the microstructure and the related residual stress in the thin films by monitoring the energy of the argon beam used in the deposition process. Measurements of the stresses within the oxide layer were performed by the X-ray diffraction-sin2Ψ method. The results show that the classic model of a pure biaxial in-plane model of stress, generally proposed in thin films, is not satisfying. A model that includes a hydrostatic stress due to the crystalline defects generated during the deposition process and a biaxial stress called a fixation stress, gives a good agreement with the experimental results. This modeling of the residual stress, based on nanometer-scale inclusions (point, extended defects) inducing a hydrostatic stress field, leads to a quantitative analysis of the nature and the concentration of the defects. This work shows results that establish a relationship between residual stress, defects and non-equilibrium phase stabilization during growth. [Copyright &y& Elsevier]

We describe the general synthesis of submicrometer-thick rare-earth/lanthanide sesquioxide (RE2O3) films with tailorable pore and grain sizes via polymer templating of hydrated chloride salt precursors. Mesostructured RE2O3 (RE = Sm, Tb-Lu) ceramics with cubic pore symmetry and high surface area (SBET ≥ 50 m² g-1) were prepared using different diblock copolymer structure-directing agents and were characterized by a combination of electron microscopy, in situ and ex situ grazing incidence small-angle X-ray scattering, N2 physisorption, X-ray photoelectron spectroscopy, X-ray diffraction including Rietveld refinement, and ultraviolet-visible spectroscopy. In the present work, we specifically focus on Dy2O3 and Yb2O3 and use both of these materials as model systems to study, among other things, the film formation and microstructure. Our research data collectively demonstrate that (1) record pore sizes of up to 42 nm in diameter can be achieved without the need for swelling agents, (2) the nanostructure can be preserved up to 1000 °C for the heavier oxides, (3) the sizes of the optical band gaps (4.9-5.6 eV) are comparable to those reported for single crystals, (4) the sol-gel-derived materials are single phase and adopt the C-type crystal structure, and (5) the grain growth is virtually linear, with domain sizes in the range of 3-16 nm. We also show that, except for Yb2O3, all of the samples have a fiber texture and the preferred orientation is significant in Sm2O3 and Lu2O3 films (March parameter G2 < 0.1). Overall, the synthesis parameters described in this work provide a blueprint for the preparation of thermally stable rare-earth oxide ceramics with both a mesoporous morphology and iso-oriented nanocrystalline walls. [ABSTRACT FROM AUTHOR]

A new concept to achieve the generalized synthesis of crystalline mesoporous rare earth (RE) oxide thin films templated with an ionic amphiphilic block copolymer is developed. Mesoporous La2O3, Eu2O3, Tb2O3, and Yb2O3 thin films as representatives of the light and heavy RE groups are synthesized by using polystyrene- block-poly(acrylic acid) (PS- b-PAA) as a templating agent. The impact of the concentration of PS- b-PAA on the morphologies of the mesopores is investigated. The local and long-range lateral structures, vertical structures, and crystallinities of the mesoporous thin films are probed by scanning electron microscopy, atomic force microscopy, grazing-incidence small-angle X-ray scattering, X-ray reflectivity, and transmission electron microscopy. The mechanism of formation of the mesoporous RE oxide thin films is discussed. [ABSTRACT FROM AUTHOR]

The temperature-dependent adsorption and reaction of acetaldehyde (CH3CHO) on a fully oxidized and a highly reduced thin-film CeO2(111) surface have been investigated using a combination of reflection-absorption infrared spectroscopy (RAIRS) and periodic density functional theory (DFT+U) calculations. On the fully oxidized surface, acetaldehyde adsorbs weakly through its carbonyl O interacting with a lattice Ce4+ cation in the η1-O configuration. This state desorbs at 210 K without reaction. On the highly reduced surface, new vibrational signatures appear below 220 K. They are identified by RAIRS and DFT as a dimer state formed from the coupling of the carbonyl O and the acyl C of two acetaldehyde molecules. This dimer state remains up to 400 K before decomposing to produce another distinct set of vibrational signatures, which are identified as the enolate form of acetaldehyde (CH2CHO-). Furthermore, the calculated activation barriers for the coupling of acetaldehyde, the decomposition of the dimer state, and the recombinative desorption of enolate and H as acetaldehyde are in good agreement with previously reported TPD results for acetaldehyde adsorbed on reduced CeO2(111) [Chen et al. J. Phys. Chem. C2011, 115, 3385]. The present findings demonstrate that surface oxygen vacancies alter the reactivity of the CeO2(111) surface and play a crucial role in stabilizing and activating acetaldehyde for coupling reactions. [ABSTRACT FROM AUTHOR]

Abstract: Dense yttria, erbia and dysprosia films with thicknesses of 44.8±1.7, 51.6±0.9 and 36.8±3.1μm, respectively, were deposited on plasma sprayed alumina coating by aerosol deposition (AD). The rare earth oxide films remarkably enhanced the erosion resistance of the plasma sprayed alumina coating upon exposure to the halogen gas plasma. The enhanced plasma erosion resistances were related to their low surface porosity as well as the low vapor pressures of the rare earth fluorides and chlorides compared with those of corresponding aluminum halogenides. Electrical breakdown voltages of the samples with yttria, erbia and dysprosia films on the plasma sprayed alumina coating were 5.5, 6.2 and 5.3kV, respectively, at room temperature and 4.0, 4.2 and 3.9kV, respectively, at 573K. The breakdown voltages at RT and 573K were more than double that of the plasma sprayed alumina coating without the AD films. [Copyright &y& Elsevier]

Ternary rare earth oxides are expected to be more promising high-k dielectric materials than conventional binary rare earth oxides due to higher band gap, higher permittivity and good interfacial stability. In the present study, the band alignment and atom thermal diffusion of LaYbO3, a new ternary rare earth oxide, are studied by X-ray photoelectron spectrum (XPS) and angle-resolved XPS, respectively. The band gap value for LaYbO3 crystalline film rises to 6.7 eV compared with 6.2 eV for amorphous film. Valence (ΔEv) and conduction band (ΔEc) offset are ΔEv = 3.5 eV, ΔEc = 1.6 eV for the amorphous film and ΔEv = 3.3 eV, ΔEc = 2.3 eV for the crystalline film. From elemental depth profile through high-k layer and silicon substrate, it is shown that La atom tends to diffuse into silicon substrate and piles up at oxide/silicon interface at high annealing temperature ~1000°C. [ABSTRACT FROM AUTHOR]

Abstract: The design, fabrication and microwave properties of distributed coplanar waveguide (CPW) phase shifters using etched Ba0.6Sr0.4TiO3 (BST) thin films on Ф 3″ LaAlO3 (100) substrates were investigated. The BST thin films employed in the circuits are deposited by RF magnetron sputtering, and then annealed at 800 °C for 30 min in air. BST thin films parallel-plate capacitors were fabricated by photolithography and etching process. At 10 kHz and 600 kV/cm electric field, the dielectric tunability, remanent polarization (2Pr ) and the coercive electric field (2EC ) of BST film were 28.7%, 2.265 μC/cm2 and 38.8 kV/cm, respectively. The loss tangent was 0.005 at zero electric field. The CPW phase-shifter designed was subsequently fabricated by optimum BST thin films and thickened top electrodes. At 21.3 GHz and 35 V, 360° phase shift was achieved, the insertion loss was −8.5 dB, the figure-of-merit (FOM) was 42.4°/dB, and the return loss was −12.1 dB. [Copyright &y& Elsevier]

Abstract: Digital epitaxial rare-earth oxide layers are grown on Si(111) substrates by molecular beam epitaxy at substrate temperatures as low as 200°C. It is demonstrated by X-ray diffraction and transmission electron microscopy that coherent digital layers form with an abrupt interface to the substrate. Theoretical investigations employing density functional theory demonstrate the potential in designing physical properties by strain. The large lattice mismatch of 9% between La2O3 and Lu2O3 allows for an intentional variation of the internal strain in the layers over a wide range. [Copyright &y& Elsevier]

Abstract: In this work, nano silver clusters incorporated into europium oxide thin films at a level of 3.8% and 12.5% have been prepared by a vacuum evaporation method on glass and silicon substrates. Samples were investigated by X-ray fluorescence, X-ray diffraction, and linear and nonlinear optical absorption methods. The X-ray diffraction reveals that the Eu oxide of these samples remains amorphous after pre-annealing at 400°C. The linear optical absorption of the samples shows surface plasmon resonance (SPR) phenomena, which varies with the Ag content of the samples. The optical nonlinear absorption properties of the prepared filmswere investigated using an open Z-scan technique with cw laser at wavelengths 476nm and 514nm. A changeover from reverse saturation absorption (RSA) to saturation absorption (SA) was observed. RSA is attributed to interband transition via two photon absorption. SA is attributed to plasmon bleach. [ABSTRACT FROM AUTHOR]

Abstract: Nanocrystalline thin films of mixed rare earth oxides (Y 1-x Er x ) 2 O 3 (0.1 ≤ x ≤ 1) were deposited by electron beam evaporation technique on polished fused silica glass at different substrate temperatures (200-500°C). The effect of the substrate temperature as well as the mixing parameter (x) on the structural and optical properties of these films has been investigated by using X-ray diffraction (XRD), energy dispersive x-ray analysis and optical spectrophotometry. XRD investigation shows that mixed rare earth oxides film (Y 1-x Er x ) 2 O 3 grown at lower substrate temperature (T s ≤300°C) are poorly crystalline, whereas films grown at higher substrate temperatures (T s ≥400°C) tend to have better crystallinity. Furthermore, the mixing parameter (x) was found to stabilize the cubic phase over the entire of 0.1 ≤ x ≤ 1. The crystallite size of the films was found to vary in the range from 25 to 39nm. Optical band gap of the films was deterimined by analysis of the absoprtion coeffifcient. For films deposited at different substrate temperatures direct and indirect transitions occur with energies varied from 5.29 to 5.94eV and from 4.23 to 4.51eV, respectively. However, films of different composition x, give optical band gap varied from 6.14 to 5.86eV for direct transition and from 5.23 to 4.22eV for indirect transitions. Consequently, one may conclude that it is possible to tune the energy band gap by relative fraction of constituent oxides. It was found that optical constants increase with increasing the substrate temperature. Nevertheless, the values of n and k decrease with increasing the mixing parameter, x. [Copyright &y& Elsevier]

Abstract: Buffer layers with 100% lattice match with YBa2Cu3O7 − δ (YBCO) were prepared from mixed rare-earth-oxides applying a simple sol–gel process and dip-coating method. Structural analysis of the sol–gel derived powder by X-ray diffraction revealed that the mixing parameter, which eliminates the lattice mismatch with YBCO, is x =0.2382, 0.1852, 0.1252, 0.0906, 0.0793 and 0.0395 in (Eu1 − x Ho x )2O3, (Eu1 − x Er x )2O3, (Eu1 − x Yb x )2O3, (Gd1 − x Ho x )2O3, (Gd1 − x Y x )2O3 and (Gd1 − x Yb x )2O3, respectively. Microstructural investigations were carried out for Gd1.819Ho0.181O3 films epitaxially grown on cube-textured Ni (100) substrates by sol–gel dip-coating process. X-ray diffraction of the buffer showed strong out-of-plane orientation on Ni tape. The (Gd1 − x Ho x )2O3 (222) pole figure indicated a single cube-on-cube textured structure. The omega and phi scans revealed good out-of-plane and in-plane alignments. The full-width at half-maximum values of omega and phi scan of (Gd1 − x Ho x )2O3 films was observed at 4.21° and 6.81°, respectively. Micrographs of the film obtained by using environmental scanning electron microscope and atomic force microscope revealed pinhole-free, crack-free, smooth and dense microstructures. [Copyright &y& Elsevier]

Abstract: Glassy thin films of [TeO2–GeO2–K2O] co-doped with rare earth oxides Sm2O3/Yb2O3 were prepared by electron beam evaporation technique on polished fused silica glass substrate. The effect of Sm2O3/Yb2O3 rare earth sub-oxides co-doping on optical properties of glasses 80TeO2–10GeO2–8K2O thin films has been investigated using optical spectrophotometry measurements in the wavelength range 200–2500nm. The structural characteristics studied by X-ray diffraction (XRD) showed that all the films are amorphous. The fundamental optical parameters like band gap and absorption coefficient are calculated in the strong absorption region of transmittance and reflectance spectrum. The possible optical transition in these films is found to be allowed indirect transition with energy gap decreases from 1.27 to 1.06eV with increasing Yb2O3 at expense of Sm2O3. The decreasing in can be interpreted in terms of the non-stoichiometry of the films. The refractive indices have been evaluated in term of envelope method suggested by Swanepoel in the transparent region. The refractive index, n, can be extrapolated by Cauchy dispersion relationship over the whole spectra range. It is observed that the refractive index, n increases with increasing Yb2O3 at expense of Sm2O3 which might be related to the changes in the compositions of TeO2 and GeO2 sub-oxides in the films. [Copyright &y& Elsevier]

Abstract: Effect of the deposition temperature (200 and 500°C) and composition of Sm x Ce1−x O2−x/2 (x =0, 10.9–15.9mol%) thin films prepared by electron beam physical vapor deposition (EB-PVD) and Ar+ ion beam assisted deposition (IBAD) combined with EB-PVD on structural characteristics and morphology/microstructure was investigated. The X-ray photoelectron spectroscopy (XPS) of the surface and electron probe microanalysis (EPMA) of the bulk of the film revealed the dominant occurrence of Ce4+ oxidation state, suggesting the presence of CeO2 phase, which was confirmed by X-ray diffraction (XRD). The Ce3+ oxidation states corresponding to Ce2O3 phase were in minority. The XRD and scanning electron microscopy (SEM) showed the polycrystalline columnar structure and a rooftop morphology of the surface. Effects of the preparation conditions (temperature, composition, IBAD) on the lattice parameter, grain size, perfection of the columnar growth and its impact on the surface morphology are analyzed and discussed. [Copyright &y& Elsevier]

Abstract: Nanostructured Gd2O3:Eu3+ and Li+ doped Gd2O3:Eu3+ thin films were prepared by pulsed laser ablation technique. The effects of annealing and Li+ doping on the structural, morphological, optical and luminescent properties are discussed. X-ray diffraction and Micro-Raman investigations indicate a phase transformation from amorphous to nanocrystalline phase and an early crystallization was observed in Li+ doped Gd2O3:Eu3+ thin films on annealing. AFM images of Li+ doped Gd2O3:Eu3+ films annealed at different temperatures especially at 973K show a spontaneous ordering of the nanocrystals distributed uniformly all over the surface, with a hillocks (or tips) like self-assembly of nanoparticles driven by thermodynamic and kinetic considerations. Enhanced photoemission from locations corresponding to the tips suggest their use in high resolution display devices. An investigation on the photoluminescence of Gd2−x Eu x O3 () and Gd2−x−y Eu x Li y O3 (, ) thin films annealed at 973K reveals that the enhancement in luminescence intensity of about 3.04 times on Li+ doping is solely due to the increase in oxygen vacancies and the flux effect of Li+ ions. The observed decrease in the values of asymmetric ratio from the luminescence spectra of Li+ doped Gd2O3:Eu3+ films at high temperature region is discussed in terms of increased Eungth as a result of Li+ doping. [Copyright &y& Elsevier]

Current voltage characteristics were measured for Cd3Se97 and Cd3Se76S21 thin film samples as a function of temperature and thickness. Static I-V curves of the investigated samples are typical for a memory switch. The mean value of the threshold voltage V¯th increases with film thickness (in the range ≈ (200 - 700nm)) and decreases with increasing temperature (in the range (303 - 365k)) and increases with the addition of sulfur S . The obtained mean value≈ 0.48 of the ratio ϵ/ΔEσ(where e is the threshold voltage activation energy & ?Es, the conduction activation energy) for the investigated compositions agree with the value of 0.5 obtained theoretically on the basis of an electrothermal model. Moreover, the obtained value of ?Tbreakdown for most of the investigated compositions are in the same order with those obtained before. Therefore the switching phenomenon in the investigated compositions can be explained according to the electrothermal model. [ABSTRACT FROM AUTHOR]

Abstract: In this contribution we present results on the structural and electrical properties of amorphous REScO3 (RE =La, Gd, Tb, Sm) and LaLuO3 thin films. The study reveals that these oxides are potential candidates for so-called higher-k dielectrics for forthcoming MOSFET generations. High dielectric constants up to 32, low leakage currents and low interface trap densities are determined for amorphous thin films prepared by pulsed-laser deposition, molecular beam deposition and e-gun evaporation. Moreover, we show that LaLuO3 gate stacks annealed up to 1050°C maintain low leakage current densities without substantial EOT increase. Finally, promising results for n-MOSFETs with GdScO3 as gate dielectric processed on strained silicon-on-insulator substrates are also shown. [Copyright &y& Elsevier]

Bowknot-like CeO2 bundles crystals were successfully prepared from a single precursor via a thermal decomposition route. The precursor was synthesized by a hydrothermal reaction using Ce(NO3)3 · 6H2O with CO(NH2)2 at 150 °C in a water-glycerol complex solution. Glycerol plays a very important role for the formation of precursor bowknot-like structures. The morphology of the precursor was maintained during the heating process. The optical absorption spectrum indicates that the CeO2 dendrites have a direct band gap of 3.42 eV, which is mostly larger than values of bulk powders due to the quantum size effect. The electrochemical characters of the CeO2 bundles structures are studied by their investigation of cyclic voltammetry (CV). It was found that the CeO2 bundles can greatly improve the electron transfer ability. [ABSTRACT FROM AUTHOR]

Ceria-based oxides are of interest as electrolyte and electrode materials in intermediate-temperature solid-oxide fuel cell (SOFCs). A sol−gel strategy has been developed for the production of mesoporous, nanostructured, single phase Ln0.1Ce0.9O2, Ln = La, Y, Sm, Gd, Dy thin films. The ceria-based mesoporous thin films exhibit high specific area, periodic through-connected networks of mesopores (∼20 nm), and continuous networks of nonagglomerated nanoparticles (15 nm). Calcination at relatively mild temperature for this oxide (300 °C) converts the amorphous films to nanocrystalline fluorine Ln0.1Ce0.9O2. Although densified during calcination, the mesoporous nanoarchitectures retain porosity, high surface area, and limited particle agglomeration. The electrical properties of mesoporous thin films are evaluated from 400 to 500 °C in air. The conductivity of these mesoporous thin films is comparable to the one observed for dense ceramic containing particles in the nanometer range, reflecting that the interparticulate junctions are not restrictive for the transport of oxide-ion vacancies. A high degree of interconnectivity has been established between the nanocrystallites (<15 nm) in these mesoporous thin films, yielding electroceramic films where the grain boundaries are not restrictive for the oxygen ion transport. This study provides processing guideline to achieve fabrication of 3-D mesostructured thin films for efficient interface in SOFC. [ABSTRACT FROM AUTHOR]

Abstract: The rare-earth mixed oxide (Gd1−x Ho x )2O3 and the superconductor YbBa2Cu3O7−x were prepared by sol–gel synthesis using metal–organic precursors. Textured Gd1.802Ho0.198O3 buffer layers were grown on biaxially textured Ni (100) substrates. YbBa2Cu3O7−x layers were epitaxially grown on the Gd1.802Ho0.198O3-coated Ni substrates using the reel-to-reel sol–gel dip coating system. Different thicknesses of superconducting layers, annealed at various temperatures, were tried to observe the effects of thickness and temperature on residual stress and microstructure properties. Residual stress in the YbBCO/Gd1.802Ho0.198O3/Ni was calculated analytically. The results showed that variation of residual stress along the thickness of structure (Ni substrate, buffer layer and YbBCO film) was constant. We also observed that the Ni substrate is under tension while buffer layer was under compression in the case of without YbBCO layer. However the residual stress was under compression in the case of YbBCO in all layers. The surface morphologies and microstructure of all samples were characterized by environmental scanning electron microscope (ESEM), atomic force microscope (AFM) and X-ray diffraction (XRD). The pole figure texture analyses of Ni substrate, Gd1.802Ho0.198O3 buffer layers and YbBCO film have shown a single cube-on-cube textured structure. [Copyright &y& Elsevier]

High-κ films are currently deposited on Ge substrates to compensate the mobility loss, as Ge offers higher mobility compared with that of silicon. This paper deals with the reliability characteristics of cerium oxide films grown by molecular beam deposition on n-type Ge (100) substrates. MOS capacitors with Pt gate electrodes were subjected to constant voltage stress conditions at accumulation. The correlation of the charge-trapping characteristics and the stress-induced leakage current (SILC) to the applied field is observed and analyzed. The results suggest that one major problem for the potential use of rare earth oxides in future MOS technology is the existence of relaxation effects. The cross-sectional value of the bulk oxide traps is on the order of 10-18 cm², thus indicating neutral defects. Direct comparison to reported results on high-κ/Si and SiO2 /Si structures shows that SILC properties are related to the quality of the dielectric layers; the semiconductor substrate is immaterial. [ABSTRACT FROM AUTHOR]

Homogeneous and ultrafine eutectic like microstructures without coarse primary crystals were formed by a crystallisation of amorphous phases for several rare earth (RE) oxide–Al2O3 eutectic systems with the off eutectic compositions. Mixtures of RE oxide and Al2O3 powders with the off eutectic compositions were melted and quenched rapidly to form the amorphous phases. A heat treatment of the amorphous phases at 1000 and 1300°C for 30 min formed RE3Al5O12/Al2O3 (or REAlO3/Al2O3) phases. This method utilises a low migration rate in the amorphous phases. SEM observation of these materials heat treated at 1300°C showed homogeneous eutectic like microstructures. Formation of primary crystals, which are always formed in the ordinal off eutectic microstructure, was absolutely suppressed. Furthermore, the microstructures were much finer than those of materials ordinarily prepared from eutectic melts. [ABSTRACT FROM AUTHOR]

Abstract: Rare-earth oxide-doped titania nanocomposites (RE3+/TiO2, where RE=Eu3+, Pr3+, Gd3+, Nd3+, and Y3+) were prepared by a one-step sol–gel-solvothermal method. The products exhibited anatase phase structure, mesoporosity, and interesting surface compositions with three oxygen species and two titanium species. The products were used as the photocatalysts to degrade a partially hydrolysis polyacrylamide (HPAM) under UV-light irradiation, a very useful polymer in oil recovery. For comparison, Degussa P25 and as-prepared pure TiO2 were also tested under the same conditions. The enhanced photocatalytic activity was obtained on as-prepared Eu3+ (Gd3+, Pr3+)/TiO2 composites, and the reasons were explained. Finally, the degradation pathway of HPAM over the RE3+/TiO2 composite was put forward based on the intermediates produced during the photocatalysis procedure. [Copyright &y& Elsevier]

Abstract: La2O3–Mo, Y2O3–Mo, Gd2O3–Mo and Ce2O3–Mo were prepared by liquid–liquid doping combined with spark plasma sintering. The microstructure and surface behaviour of rare earth oxide of the cathode have been studied by microscope, Auger Electron Spectroscopy (AES) and X-ray Photoelectron Spectroscopy (XPS) methods. Among these four kinds of cathode, Y2O3–Mo cathode exhibits the best secondary emission property, i.e., the maximum secondary emission yield could reach 5.24. The penetration depth of primary electrons and escape depth of secondary electrons have been calculated and the energy distribution of primary electrons in the cathode has been simulated by Monte Carlo method. Y2O3–Mo cathode has the largest penetration depth and escape depth, which could be attributed to the highest secondary electron emission yield of the cathode. [Copyright &y& Elsevier]

Eight novel homoleptic tris-guanidinato complexes M[(NiPr)2CNR2)3 [M = Y (a), Gd (b), Dy (c) and R = Me (1), Et (2), iPr (3)] have been synthesized and characterized by NMR, CHN-analysis, mass spectrometry and infrared spectroscopy. Single crystal structure analysis revealed that all the compounds are monomers with the rare-earth metal center coordinated to six nitrogen atoms of the three chelating guanidinato ligands in a distorted trigonal prism geometry. With the use of TGNDTA and isothermal TGA analysis, the thermal characteristics of all the complexes were studied in detail to evaluate their suitability as precursors for thin film deposition by MOCVD and ALD. The iPr-Me2N-guanidinates of Y, Gd and Dy (1a-c) showed excellent thermal characteristics in terms of thermal stability and volatility. Additionally, the thermal stability of the iPr-Me2N-guanidinates of Y and Dy (1a, C) in solution was investigated by carrying out NMR decomposition experiments and both the compounds were found to be remarkably stable. All these studies indicate that iPr-Me2N-guanidinates of Y, Gd and Dy (1a-c) have the prerequisites for MOCVD and ALD applications which were confirmed by the successful deposition of Gd2O3 and Dy2O3 thin films on Si(100) substrates. The MOCVD grown films of Gd2O3 and Dy2O3 were highly oriented in the cubic phase, while the ALD grown films were amorphous. [ABSTRACT FROM AUTHOR]

Abstract: Using an unconventional approach, single crystalline Si-nanoclusters (Si-NCs) with uniform size and higher density were embedded into epitaxial rare earth oxide with two-dimensional spatial arrangements at a defined distance from the substrate using solid source molecular beam epitaxy (MBE) technique. The incorporated Si-NCs with average size of 5nm and density of 2×1012 cm−2 exhibit charge storage capacity with promising retention (∼107 s) and endurance (105 write/erase cycles) characteristics. The Pt/Gd2O3 (Si-NC)/Si (MOS) basic memory cells with embedded Si-nanoclusters display large programming window (∼1.5–2V) and fast writing speed. With such properties demonstrated, we believe that the Si-NCs embedded in epitaxial Gd2O3 could be potential candidate for high density nonvolatile memory devices in the future. [Copyright &y& Elsevier]

Abstract: The reaction of yttrium acetate hydrate in 1,2-propanediol at 300°C yielded a product containing acetate groups and glycol moieties. From this product, Y2O3 was directly crystallized at 400°C without the formation of a carbonate oxide phase. The thus-obtained Y2O3 samples had a small crystallite size (2.2nm) and significantly large surface area (280m2/g). Other nanocrystalline rare earth (Gd–Yb) oxides were also obtained by this method. [Copyright &y& Elsevier]

Scheelite type LiGdF4, LiLuF4, and mixtures of both end members were prepared by a hydrofluorination route from the rare earth oxides and commercial LiF. The samples were purified by melting in HFAr mixtures, and were investigated by differential scanning calorimetry DSC, scanning electron microscopy SEM, and energy dispersive Xray spectroscopy EDX techniques. Both end members show unlimited miscibility in the solid phase. Mixed crystals containing at least 65 mol LiLuF4melt under direct formation of the liquid phase. The gap between solidus and liquidus is narrow. LiGdF4and mixed crystals with less then 65 mol LiLuF4decompose peritectically under formation of Gd,LuF3. Crystal growth is expected to be possible either from Lurich melts with the appropriate scheelite composition or from Gdrich melts containing an excess of LiF. © 2008 WILEYVCH Verlag GmbH & Co. KGaA, Weinheim [ABSTRACT FROM AUTHOR]

Abstract  A number of physicochemical properties of samples are investigated. Changes in the electrical resistance of films based on the yttrium, terbium, and praseodymium oxides in an air atmosphere and upon interaction with different gaseous media (ozone, argon, methanol, ethanol) are studied. The ranges of operating temperatures and the maximum relative sensitivity coefficients of the films under investigation are determined. [ABSTRACT FROM AUTHOR]