Rare Earth Oxide Films Research Articles

Biocompatibility of Cerium Oxide Films Synthesized by Dual Plasma Deposition

Cerium oxide films have been fabricated using dual plasma deposition. X-ray diffraction. (XRD) reveals a crystalline phase and X-ray photoelectron spectroscopy (XPS) shows that La exists predominantly in the +4 oxidation state. The activated partial thromboplastin time is longer than that of blood plasma and stainless steel. Furthermore, the numbers of adhered, aggregated and morphologically changed platelets are reduced compared to low-temperature isotropic carbon (LTIC). HUVEC cells exhibit good adhesion and proliferation behavior on cerium oxide films. This study suggests rare earth oxide films are potential blood-contacting biomedical materials.

Rare-earth gate oxides for GaAs MOSFET application

Rare-earth oxide films for gate dielectric on n-GaAs have been investigated. The oxide films were e-beam evaporated on S-passivated GaAs, considering interfacial chemical bonding state and energy band structure. Rare-earth oxides such as Gd 2O 3, (Gd x La 1− x ) 2O 3, and Gd-silicate were employed due to high resistivity and no chemical reaction with GaAs. Structural and bonding properties were characterized by X-ray photoemission, absorption, and diffraction. The electrical characteristics of metal-oxide-semiconductor (MOS) diodes were correlated with material properties and energy band structures to guarantee the feasibility for MOS field effect transistor (FET) application. Gd 2O 3 films were grown epitaxially on S-passivated GaAs (0 0 1) at 400 °C. The passivation induced a lowering of crystallization temperature with an epitaxial relationship of Gd 2O 3 (4 4 0) and GaAs (0 0 1). A better lattice matching relation between Gd 2O 3 and GaAs substrate was accomplished by the substitution of Gd with La, which has larger ionic radius. The in-plane relationship of (Gd x La 1− x ) 2O 3 (4 4 0) with GaAs (0 0 1) was found and the epitaxial films showed an improved crystalline quality. Amorphous Gd-silicate film was synthesized by the incorporation of SiO 2 into Gd 2O 3. These amorphous Gd-silicate films excluded defect traps or current flow path due to grain boundaries and showed a relatively larger energy band gap dependent on the contents of SiO 2. Energy band parameters such as Δ E C, Δ E V, and E g were effectively controlled by the film composition.

Structural and optical properties of polycrystalline thin films of rare earth oxides grown on fused quartz by low pressure MOCVD

We report the structural and optical properties of oriented polycrystalline thin films of rare earth oxides (REO), namely Er 2O 3, Gd 2O 3, Eu 2O 3, and Yb 2O 3 grown on fused quartz by low-pressure metalorganic chemical vapour deposition (MOCVD) in the temperature range of 450–800 °C, using adducted β -diketonate complexes of rare earth metals as precursors. The films were characterized by X-ray diffraction (XRD) and UV–visible spectrophotometry. While the films grown at low temperatures (∼500 °C) are poorly crystalline, those grown on or above 525 °C display a significant (1 1 1) texture. Growth of textured cubic REO in (1 1 1) direction on amorphous substrate is interpreted in terms of minimization of surface energy at the film–substrate interface. The degree of misfit between the interatomic distances in the disordered fused quartz substrate and those in the crystalline REO is invoked to explain the presence (absence) of low-intensity reflections other than (1 1 1). The incorporation of carbon (from the precursor) into the films affects the optical properties of REO, as examined by UV–visible spectroscopy.

Bayesian group analysis of plasma-enhanced chemical vapour deposition data

A ubiquitous goal in plasma-enhanced chemical vapour deposition (PECVD) is to describe the correlation between film properties and categorical and quantitative input variables. The correlations within the high-dimensional parameter space are described using a multivariate model. Bayesian group analysis is employed to assess the grouping structures of the set of data vectors. This allows to identify sub-groups or meta-groups of predefined groups of data sets, e.g. with respect to source gases. Outliers can be identified by the necessity to form a separate group. The Bayesian approach consistently allows the handling of missing data. The grouping probabilities were compared with classical approaches such as likelihood ratio tests, the Akaike information criterion and a Bayesian variant called Bayesian information criterion. The method was applied to PECVD data of rare-earth oxide film deposition and hydrocarbon film deposition to study the evidence of grouping structures attributed to categorical quantities such as rare-earth components or source gases and quantitative variates such as bias voltage.

Composition, chemical structure, and electronic band structure of rare earth oxide/Si(1 0 0) interfacial transition layer

The experimental data for Gd 2O 3, as a typical example of rare earth oxide films, clearly indicate that combination of high resolution RBS and high resolution XPS studies is powerful for the determination of composition and chemical structures of high- k dielectric films. Conduction and valence band discontinuities at rare earth oxide/Si(1 0 0) interfaces were also determined by measuring the O 1s photoelectron energy loss and valence band spectra.

Properties of high κ gate dielectrics Gd2O3 and Y2O3 for Si

We present the materials growth and properties of both epitaxial and amorphous films of Gd2O3 (κ=14) and Y2O3 (κ=18) as the alternative gate dielectrics for Si. The rare earth oxide films were prepared by ultrahigh vacuum vapor deposition from an oxide source. The use of vicinal Si (100) substrates is key to the growth of (110) oriented, single domain films in the Mn2O3 structure. Compared to SiO2 gate oxide, the crystalline Gd2O3 and Y2O3 oxide films show a reduction of electrical leakage at 1 V by four orders of magnitude over an equivalent oxide thickness range of 10–20 Å. The leakage of amorphous Y2O3 films is about six orders of magnitude better than SiO2 due to a smooth morphology and abrupt interface with Si. The absence of SiO2 segregation at the dielectric/Si interface is established from infrared absorption spectroscopy and scanning transmission electron microscopy. The amorphous Gd2O3 and Y2O3 films withstand the high temperature anneals to 850 °C and remain electrically and chemically intact.

Solution Synthesis of Epitaxial Rare-Earth Oxide Thin Films on Roll-Textured Nickel

ABSTRACTUsing solution chemistry, epitaxial films of rare-earth oxides of the general formula RE2O3 (where RE = Sm to Lu) were prepared on cubic-textured nickel tapes. Solutions of metal methoxyethoxides or metal acetate/methoxyethoxides in 2-methoxyethanol were used to coat rolltextured nickel tapes using either spin-coating or dip-coating. Coated tapes were subsequently heated in a reducing atmosphere at temperatures between 950 °C and 1160 °C for varying lengths of time. Film quality was determined using X-ray diffraction and electron and surface probe microscopy. Films were found to be oriented both in and out-of-plane of the substrate, free of pinholes and gross defects, and of sufficient quality for use as substrates for high Tc, superconductors.

Preparation of rare-earth oxide films by a pyrolysis technique from acetylacetonates

(1 1 1) oriented Nd doped and nondoped Y 2O 3 thin films were prepared on the fused quartz substrates by a pyrolysis technique using acetylacetonate complexes coated through a vacuum deposition process. Acetylacetonates, which were evaporated in vacuum (2×10 −5 Torr) on to the fused quartz substrates, were oxidized and crystallized at various temperatures in air. Cubic Y 2O 3 films with (1 1 1) orientation were formed on the SiO 2 by annealing above 600°C.

Fabrication and Ellipsometric Investigation of Thin Films of Rare-Earth Oxides

Fabrication and Ellipsometric Investigation of Thin Films of Rare-Earth Oxides

Recombination properties of silicon passivated with rare-earth oxide films

The recombination properties of silicon passivated with films of rare-earth oxides were investigated. The films were obtained by thermal resistive sputtering of a rare-earth metal followed by thermal oxidation of the obtained layer in air at 400 °C. It was established that the effective nonequilibrium charge-carrier lifetime measured by photoconductivity relaxation is 2–3 times higher after deposition of the rare-earth oxide film. Surface recombination rates at the silicon-rare-earth oxide interface were determined to be 290–730 cm/s for different rare-earth oxides. The combination of high optical transmittance of the experimental materials and low recombination losses in silicon coated with a rare-earth oxide film makes it possible to recommend rare-earth oxide films as optical antireflection and passivating coatings for silicon photoelectric devices.

Ultrathin layers of rare earth oxides from langmuir-blodgett films

Ultrathin rare earth oxide films have been fabricated using Langmuir-Blodgett films of rare earth arachidates as precursors. Irradiation of these films with UV light and subsequent heating of the films (350°C) result in oxide films exhibiting a smoothness comparable to that of the Si-wafers used as substrates (roughness R ≈ 0.3 nm). The film thickness can easily be adjusted via the number of Langmuir-Blodgett monolayers deposited onto the substrate.

Application of screen‐printed rare earth oxide protective film to alternating‐current plasma display panels

AbstractScreen‐printed protective film of rare earth oxides (La2O3, Gd2O3, Dy2O3, Y2O3, and Yb2O3) was applied to ac‐plasma display panels. Screen‐printed rare earth protective films have higher luminous efficiencies than a sputtered MgO protective film. However, it is difficult to obtain a low firing voltage (Vf) from screen‐printed rare earth oxide protective films.Only the La2O3 protective film has a lower firing voltage than the sputtered MgO protective film. Gd2O3 has the lowest sustaining voltage (VS) which is 54 V lower than that of the sputtered MgO protective film. Since rare earth oxide powders with high crystallinity exhibit superior discharge characteristics, it is necessary to improve the crystallinity of the powders. In order to obtain a high luminous efficiency, it is necessary to have a low discharge current. Both Y2O3 and La2O3 have a high current‐limiting effect. The current‐limiting effect is related closely to cell resistance. Since Dy2O3 has a low cell resistance, its current‐limiting effect is low. Gd2O3 has the highest luminance per unit discharge current. If it is possible to reduce the discharge current of Gd2O3 further, it is possible to obtain a higher luminous efficiency. Every screen‐printed rare earth oxide film has an excellent protective effect. However, from the viewpoint of low discharge voltage and high luminous efficiency, La2O3 and Gd2O3 are superior to all other rare earth oxides due to their low discharge voltage and high luminous efficiency.

Characterization of thin solid films of rare earth oxides formed by the metallo-organic chemical vapour deposition technique, for high temperature corrosion applications

Thin films of rare earth oxides (REOs) have been deposited on stainless steel and quartz substrates by the metallo-organic chemical vapour deposition technique, using β-diketonate precursors. The structure and characteristics of the REO films were determined by scanning electron microscopy, X-ray diffraction, Auger electron spectroscopy, Secondary ion mass spectroscopy and X-ray photoelectron spectroscopy. The thicknesses of the coatings were determined by highly accurate weighing and by profilometry after a laser impact. Coated steel samples were oxidized at high temperature in isothermal and cyclic conditions to study the deposited rare earth element effect.

Characterization of thin solid films of rare earth oxides formed by the metallo-organic chemical vapour deposition technique, for high temperature corrosion applications

Thin films of rare earth oxides (REOs) have been deposited on stainless steel and quartz substrates by the metallo-organic chemical vapour deposition technique, using β-diketonate precursors. The structure and characteristics of the REO films were determined by scanning electron microscopy, X-ray diffraction, Auger electron spectroscopy, Secondary ion mass spectroscopy and X-ray photoelectron spectroscopy. The thicknesses of the coatings were determined by highly accurate weighing and by profilometry after a laser impact. Coated steel samples were oxidized at high temperature in isothermal and cyclic conditions to study the deposited rare earth element effect.

The Effect of Deposited Rare Earth Oxide Films on High Temperature Corrosion Behaviour of Different Metals and Alloys

The Effect of Deposited Rare Earth Oxide Films on High Temperature Corrosion Behaviour of Different Metals and Alloys

Thin films of rare-earth (Y, La, Ce, Pr, Nd, Sm) oxides formed by the spray-ICP technique

Thin films of Y 2O 3, La 2O 3, CeO 2, PrO 2, Nd 2O 3 and Sm 2O 3 were synthesized by injecting ultrasonically atomized metal nitrate solutions into a high temperature inductively coupled RF plasma above 5000 K generated under atmospheric pressure (the spray-ICP technique). Fused quartz plates and single crystal sapphire plates giving no background X-ray reflection peaks were used as substrates. About 0.4 μm thick transparent films could be prepared by 10 min of running. The films of CeO 2 and PrO 2, both belonging to the cubic flourite type, revealed (100) and (111) orientations, respectively. With the remaining oxides having A (hexagonal), B (monoclinic) and C (cubic) rare-earth structures, film orientations were A (001) for La 2O 3, A (001)+C (111) for Nd 2O 3, and C (111) for Y 2O 3. Sm 2O 3 films were composed of a phase with C (111) and an extra phase with an orientation close to (001) of A-Sm 2O 3 or its equivalent, (20 1 ) of B-Sm 2O 3.

Thin yttrium and rare earth oxide films produced by plasma enhanced CVD of novel organometallic ?-complexes

Novel volatile cyclooctatetraenyl-pentamethylcyclopentadienyl sandwich complexes have been used as precursors to deposit thin yttrium and rare earth oxide films by means of PECVD. These compounds form pure oxide films in plasmas of argon/oxygen or argon/water-vapour, in nitrous oxide, and carbon dioxide at substrate temperatures of 350–400° C and power densities of 1.0–1.5 W/cm2. The films were characterized by metal analysis, carbon analysis, XPS, CTEM electron diffraction, SEM micrographs, and FTIR spectra.

THIN LANTHANUM OXIDE AND RARE-EARTH OXIDE FILMS BY PECVD OF β-DIKETONATE CHELATE COMPLEXES

A method for the deposition of lanthanum oxide and rare-earth (Re) oxide films using the tris[2,2,6,6-tetramethyl-3,5-heptanedionato] chelate complexes is reported. The films were characterized by metal analysis, carbon analysis, FTIR spectra, XPS and SEM micrographs. The film composition strongly depends on experimental parameters. Films deposited in an oxygen plasma at a substrate temperature of 400°C and a power density of 1.5 W/cm 2 are amorphous, transparent and show carbon contents of < 2%. If argon or hydrogen is used as carrier gas, films contain ≈ 5% carbon. With substrate temperatures < 400° C or power densities < 1.5 W/cm 2, films containing trivalent Re metal ions and considerable contamination by polymeric material are formed.

Films of rare earth oxides formed by electron beam evaporation

Films of rare earth oxides formed by electron beam evaporation

Films of rare earth oxides formed by electron beam evaporation

Rare earth oxides can effectively be deposited by electron beam evaporation. The films thus formed are dense and non-porous and adhere to various metal substrates. The strength of the bond between the films and the substrates is greatly affected by the treatment of the substrate prior to deposition (the substrate needs to be roughened). The structure of the films is affected to a small degree by the substrate condition and deposition parameters. The orientation of the films is dependent on the substrate temperature. The characteristics of erbium oxide and yttrium oxide films are presented.