Fabrication of low-loss channel waveguides in Al2O3 and Y2O3 layers by inductively coupled plasma reactive ion etching

Etching of amorphous Al₂O₃ and polycrystalline Y₂O₃ films has been investigated using an inductively coupled reactive ion etch system. The etch behaviour has been studied by applying various common process gases and combinations of these gases, including CF₄/O₂, BCl₃, BCl₃/HBr, Cl₂, Cl₂/Ar and Ar. The observed etch rates of Al₂O₃ films were much higher than Y₂O₃ for all process gases except for Ar, indicating a much stronger chemical etching component for the Al₂O₃ layers. Based on analysis of the film etch rates and an investigation of the selectivity and patterning feasibility of possible mask materials, optimized optical channel-waveguide structures were fabricated in both materials. In Al₂O₃, channel waveguides were fabricated with BCl₃/HBr plasma and using a standard resist mask, while in Y₂O₃, channel waveguides were fabricated with Ar and using either a resist or a sputter deposited Al₂O₃ mask layer. The etched structures in both materials exhibit straight sidewalls with minimal roughness and sufficient etch depths (up to 530 nm for Al₂O₃ and 250 nm for Y₂O₃) for defining waveguides with strong optical confinement. Using the developed etch processes, low additional optical propagation losses (on the order of 0.1 dB/cm) were demonstrated in single-mode ridge waveguides in both Al₂O₃ and Y₂O₃ layers at 1550 nm. PACS 42.70.-a; 42.82.-m; 42.82.Cr     

Multiplet splitting patterns exhibited by the first row transition metal oxides in X-ray photoelectron spectroscopy

High resolution photoelectron spectra from transition metal ions in TiO₂, V₂O₅, VO₂, V₂O₃, MnO, Mn₂O₃, MnO₂, Cr₂O₃, FeO, CoO, NiO, CuO, Cu₂O, FeSrO₃, and Cu doped CaTiO₃ were re-examined using a constrained curve fitting approach. Effective fits of the multiplet splitting present could be attained for the oxides with unfilled 3d bands if multiple final states were assumed. The type of transitions implied, also suggest the classification of these oxides during core level photoelectron emission as either; Mott–Hubbard (V₂O₅, VO₂, V₂O₃, Cr₂O₃, and FeO), intermediate (MnO, Mn₂O₃, and MnO₂) or charge transfer type compounds (FeSrO₃, CoO, NiO, CuO and Cu doped CaTiO₃). These transitions along with relationships defining the splitting energy with respect to the total spin and binding energy are discussed.     

Metal oxide additives for the sintering of silicon carbide: Reactivity and densification

The effectiveness of sintering additives for β-SiC was examined based on thermodynamic calculations and experimental observations under hot pressing conditions of 1700–1800 °C. Various types of oxides, such as Al₂O₃, Fe₂O₃, MgO, TiO₂, WO₃ and Y₂O₃, were examined theoretically by considering the Gibbs formation free energy and vapor pressure. According to experimental observations expanded to their binary and ternary systems after hot pressing at 1750 °C and 20 MPa, Al₂O₃, MgO, Y₂O₃ and their mixed systems were found to be the only effective sintering additives that do not react with β-SiC at high temperatures. On the other hand, Fe₂O₃, TiO₂, WO₃ and their combinations with other oxides were not effective because of the reaction with β-SiC by forming the corresponding metal carbides and/or silicides, as predicted by thermodynamic simulations. Moreover, the experimental results for the additional possible components were also included.     

Luminescent characteristics of LiCaBo3:M (M=Eu, Sm, Tb, Ce, Dy) phosphor for white LED

LiCaBO₃:M (M=Eu³⁺, Sm³⁺, Tb³⁺, Ce³⁺, Dy³⁺) phosphors were synthesized by a normal solid-state reaction using CaCO₃, H₃BO₃, Li₂CO₃, Na₂CO₃, K₂CO₃, Eu₂O₃, Sm₂O₃, Tb₄O₇, CeO₂ and Dy₂O₃ as starting materials. The emission and excitation spectra were measured by a SHIMADZU RF-540 UV spectrophotometer. And the results show that these phosphors can be excited effectively by near-ultraviolet light-emitting diodes (UVLED), and emit red, green and blue light. Consequently, these phosphors are promising phosphors for white light-emitting diodes (LEDs). Under the condition of doping charge compensation Li⁺, Na⁺ and K⁺, the luminescence intensities of these phosphors were increased.     

Mixed lattice disorder in ionic materials

This paper reports fundamental defect energies in CsF, β-CsCl, CaBr₂, CaI₂, Ga₂O₃, Ti₂O₃, Rh₂O₃ and V₂O₃ obtained by simple extrapolation procedures, and in CaCl₂ by direct atomistic simulation. It is suggested that CsF, β-CsCl and CaBr₂ will exhibit mixed lattice disorder, and that in Ti₂O₃, Rh₂O₃ and V₂O₃ Schottky and anion Frenkel energies differ by less than 1 eV. The implications of mixed disorder for the interpretation of Arrhenius energies of diffusion are examined. For CsF and β-CsCl these are shown to be of the usual type, whereas the temperature dependence of the diffusion coefficients in CaBr₂ is predicted to be more complicated.     

Preparation and characterization of inorganic colored coating layers on lamellar mica-titania substrate

The inorganic colored composite pigments, such as Fe₂O₃-, Bi₄Ti₃O₁₂-, and CoAl₂O₄-coated mica-titania composites, were prepared by hydrolysis of FeCl₃, Bi(NO₃)₃, and Co(NO₃)₂/Al(NO₃)₃ in the presence of mica-titania substrate and calcination at different temperatures. The inorganic coating layers on mica-titania substrate surfaces were explored by X-ray diffraction, scanning electron microscopy, Fourier transform infrared, and X-ray photoelectron spectroscopy. Dense and uniform Fe₂O₃ coating layers were formed on the surfaces of mica-titania substrates. At lower Bi₂O₃ loading, Bi₄Ti₃O₁₂ nanoparticles were formed on the surfaces of mica-titania substrates. But at higher Bi₂O₃ loading, Bi₄Ti₃O₁₂ nanosheets were formed and perpendicularly oriented to the substrate surfaces. CoAl₂O₄ nanosheets were formed on the mica-titania substrates and perpendicularly oriented to the substrate surfaces. The pigmentary performances of the inorganic composite pigments were analyzed by CIE, indicating that red, yellow, and blue colored pigments were achieved by coating Fe₂O₃, Bi₄Ti₃O₁₂, and CoAl₂O₄ on mica-titania substrate surfaces, respectively. The pigmentary performances of the inorganic composite pigments were significantly affected by the morphology and loading of inorganic coating layers.     

Effect of some additions on the sinterability and magnetic properties of barium hexaferrite

The effect of additions on the densification of previously prepared stoichiometric barium hexaferrite, during the initial and intermediate stages of sintering, as well as on the coercivity and remanence were studied. The effect of non-stoichiometry, SiO₂, Al₂O₃, Cr₂O₃, TiO₂, SnO₂, MnO₂, MgO, NiO and Bi₂O₃ is included.While SiO₂ and Bi₂O₃ form liquid phases that increase the density, Al₂O₃, Cr₂O₃ and MnO₂ form a limited solid solution and are generally beneficial when added in the proper amounts. At 1300 SiO₂ up to 0.55% and Al₂O₃ up to 1% gave better magnetic properties. On the other hand addition of TiO₂, MgO, NiO or SnO₂ has a deleterious effect.     

An AES analysis of oxide films on iron

The Auger spectra of the iron oxides have been investigated. The relative amplitudes of the Auger lines from oxygen and iron have been determined for FeO, Fe₃O₄, α-Fe₂O₃, γ-Fe₂O₃, and FeOOH. It was found that the amplitude ratio s of the O (510 eV)/Fe (703 eV) lines was, to a first approximation, directly proportional to the ratio of oxygen and iron in the chemical formula. Structure was observed in the spectra resulting from the Fe M_2,3 VV transition. Different spectra were observed for Fe, FeO, Fe₃O₄, Fe₃O₃, and FeOOH; however, the same spectra were obtained for α- and γ-Fe₂O₃.     

Glass bead with minimized amount (11 mg) of sample for X‐ray fluorescence determination of archaeological ceramics

By using very small amount – 11‐mg – of sample powder, major oxides (Na₂O, MgO, Al₂O₃, SiO₂, P₂O₅, K₂O, CaO, TiO₂, MnO, and total Fe₂O₃) in ancient pottery (and igneous rocks) were determined with X‐ray fluorescence spectrometry. This minimized amount of sample was used to prepare a fused glass bead with 300 times the weight of lithium tetraborate as an alkali flux. Calibration standards were obtained by compounding chemical reagents (Na₂CO₃, MgO, Al₂O₃, SiO₂, Na₄P₂O₇, K₂CO₃, CaCO₃, TiO₂, MnO₂, and Fe₂O₃) and the flux. Fewer 11 mg of reagents as oxides were able to give reliable calibration curves with good linearity (correlation coefficient: r > 0.995). Fewer 11 mg of sample was able to give reliable analytical results with good precision (relative standard deviation: <3% for more than 10.0 mass% of analyte, <10% for 1.0–10.0 mass% of analyte, and <20% for 0.1–1.0 mass% of analyte). Lower limits of detection were roughly a sub‐percentage of analyte in an unprepared sample (e.g. 0.3 mass% for Na₂O, 0.5 mass% for MgO, 1.0 mass% for Al₂O₃, and 0.01 mass% for MnO). Composition of major oxides in artificial and natural aluminosilicate materials (including rock, stone, sand, sediment, and clay; and their products) should be fundamental information to be considered in detail. The present X‐ray determination based on very small amount of sample might be made readily accessible for destructive analysis of precious samples for archaeology (and geochemistry). Copyright © 2011 John Wiley & Sons, Ltd.     

Synthesis, characterization and catalytic properties of sol-gel derived mixed oxides

Alumina and 1:1 mixed oxides of Al₂O₃-ZrO₂, Al₂O₃-TiO₂, SiO₂-TiO₂ and ZrO₂-TiO₂ were synthesized via a sol-gel process by the so-called neutral amine route, followed by calcination at 600 °C. The mixed oxides were characterized before calcination by X-ray diffraction, revealing ordered hexagonal (Al₂O₃, Al₂O₃-ZrO₂, ZrO₂-TiO₂) and lamellar (SiO₂-TiO₂, Al₂O₃-TiO₂) structures. After calcination, all samples exhibited amorphous structures. Surface areas and pore characteristics of all materials were determined by nitrogen adsorption isotherms. The calcined oxides are active catalysts in the epoxidation of cyclooctene with tert-butyl hydroperoxide as oxidant. Epoxide yields from 14 to 45% were found for reaction times of 24 h. The titanium oxide containing catalysts are the most active and selective ones. On the other hand, the poisoning of acidic centers yields a decreasing activity while increasing selectivity.     

The synthesis of polycrystalline H3O+β″βAl2O3 ceramics from conventional precursor NaKβ″/βAl2O3 powders

H₃O⁺β″Al₂O₃, H₃O⁺/βAl₂O₃ and H₃O⁺β″/βAl₂O₃ /ZrO₂ ceramics of equiaxed, fine-grained microstructure were prepared by conventional synthesis techniques, gas-phase and vapour-phase ion exchange to the potassium form and field-assisted ion exchange in dilute HCl vapour to the hydronium form. The bend strength of the polycrystalline H₃O⁺β″Al₂O₃ and H₃O⁺β″/βAl₂O₃ was > 200 MPa. The conductivity of H₃O⁺β″Al₂O₃, H₃O⁺β″/βAl₂O₃ ZrO₂ was 8×10⁻⁶, 2×10⁻⁶ and 9×10⁻⁷ (Ω cm)⁻¹, respectively, at 25°C. The materials were demonstrated to perform in steam electrolysis cells at 100°C.     

Formation pathways of HO2 and OH changing as a function of temperature in photolytically initiated oxidation of dimethyl ether

The time resolved product formation in oxidation of dimethyl ether (DME) has been studied between 298-625 K and 20-90 torr total pressure. Near-infrared frequency modulation spectroscopy (FMS) with Herriott type multi pass optics and UV absorption spectroscopy (UV) were conducted in the same cell. The reaction was initiated by pulsed photolysis in a mixture of Cl₂, O₂, and DME via CH₃OCH₂ radical formation. The reaction process was investigated through FMS measurement of HO₂ and OH, and UV measurement of CH₃OCH₂O₂. The yields of HO₂ and OH are obtained by comparison with reference mixtures, Cl₂, O₂, and CH₃OH for HO₂, and Cl₂, O₂, CH₃OH, and NO for OH, which convert 100% of initial Cl to HO₂ and OH. The CH₃OCH₂O₂ yield is also obtained. It was found that the HO₂ yield increases sharply over 500 K mainly with a longer time constant than that of R + O₂ reaction, while a prompt component exists throughout the temperature range at a few percent yield. OH was found to be produced promptly at a yield considerably larger than that known for the simplest alkanes. The CH₃OCH₂O₂ profile has a prompt rise followed by a gradual decay whose rate is consistent with the slow HO₂ formation. The species profiles were successfully predicted with a model constructed by modifying the existing one to suit the reduced pressure condition. After modification, it was inferred that the HO₂ formation over 500 K is secondary from HCHO + OH and HCO + O₂ and a part of HCO is formed directly from the O₂ adduct, whereas the HO₂ formation below 500 K is governed by CH₃OCH₂O₂ chemistry. The HCO forming pathway via isomerization-decomposition of the O₂ adduct, which was not included in the former models, was supported by our quantum-chemical calculations.     

Eu<Superscript>3+</Superscript> As a Luminescent Probe for Studying the Structure of R<Subscript>2</Subscript>O<Subscript>3</Subscript> Materials (R = Y,Eu, and Gd)

Spectra of Eu³⁺ in various dielectric matrices (Gd₂O₃:Eu³⁺, Y₂O₃:Eu³⁺, Eu₂O₃, and mSiO₂/Gd₂O₃:Eu³⁺ mesoporous particles) are studied by local cathodoluminescence. The results allowed identification of the local environment of Er³⁺ ions in amorphous samples and detection of the monoclinic Eu₂O₃ phase impurity in samples with yttrium oxide. The cathodoluminescence spectra of chemically pure Y₂O₃, Eu₂O₃, and Gd₂O₃ are recorded. Conclusions about the structural features of the materials are made and confirmed by other methods (XRD and EPMA).     

少量稀土元素氧化物对于一种矩磁铁氧体磁心性能的影响

本文报导了少量稀土元素氧化物(La₂O₃,CeO₂,Sm₂O₃,Gd₂O₃和Y₂O₃)对于一种含ZnO和CuO的Mg-Mn矩磁铁氧体磁心性能的影响,简要地叙述了样品的制备过程。测量了磁心的静态磁滞迴线,饱和磁化强度,居里点和讯号杂音比。实验结果表明:加La₂O₃或Gd₂O₃可以增加矩形比和(B-H_m/2)/B_m和讯号杂音比,并使后者的分布往高比值移动,但加CeO₂,Sm₂O₃或Y₂O₃却没有使这些性能改善,甚至有所降低。文中举例说明了磁心尺寸对于矩形比、淬火温度和稀土元素氧化物的含量对于讯号杂音比的影响。最后指出:这种方法可能提供一种改善磁心某些性能而不显著改变其居里点的途径。     

Thermoluminescent properties of Sr2P2O7 doped with copper and some rare earth elements

In this study, Sr₂P₂O₇ was doped with some rare earth oxides (Pr₆O₁₁, Nd₂O₃, Dy₂O₃, Ho₂O₃, Er₂O₃, and Tm₂O₃) at 0.5%, 1%, 2%, 3%, 4%, 5%, 10%, and 15% (by weight) and co-doped with CuO by heating at 900 °C for 10 h. Structural analysis of the products was carried out by powder X-ray diffraction (XRD). XRD patterns of the samples showed that doping did not alter the orthorhombic structure of the Sr₂P₂O₇. Thermoluminescence (TL) glow curve measurements were obtained and these showed that Pr and Cu-doped Sr₂P₂O₇ exhibit very significant thermoluminescence glow peaks, suggesting these could be promising dosimetric materials. Bearing this in mind, some TL dosimetric properties of Sr₂P₂O₇:Cu,Pr compounds are presented in this paper, confirming they are promising for this application.     

A comparison of electronic structure and optical properties between N-doped β-Ga2O3 and N-Zn co-doped β-Ga2O3

The electronic structure and optical properties of N-doped β-Ga₂O₃ and N-Zn co-doped β-Ga₂O₃ are investigated by the first-principles calculation. In the N-Zn co-doped β-Ga₂O₃ system, the lattice parameters of a, b, c, V decrease and the formation energy of N-Zn co-doped β-Ga₂O₃ is smaller in comparison with N-doped β-Ga₂O₃. There are two shallower acceptor impurity levels in N-Zn co-doped β-Ga₂O₃. Comparing with N-doped β-Ga₂O₃, the major absorption peak is red-shifted and the impurity absorption edge is blue-shifted for N-Zn co-doped β-Ga₂O₃. The results show that the N-Zn co-doped β-Ga₂O₃ is found to be a better method to push p-type conductivity in β-Ga₂O₃.     

γ-Fe2O3中的氢含量

利用热中子透射法测定γ-Fe₂O₃的氢含量。利用差热分析、磁分析以及穆斯堡尔效应研究γ-Fe₂O₃的相变,实验结果表明在γ-Fe₂O₃结构中确实含有一定量的氢,当γ-Fe₂O₃结构中的阳离子空位被H¹⁺,Co²⁺,Si⁴⁺,P⁵⁺等离子占据时,将 关键词：     

Analysis of XPS spectra of Fe and Fe ions in oxide materials

Samples of the iron oxides Fe_0.94O, Fe₃O₄, Fe₂O₃, and Fe₂SiO₄ were prepared by high temperature equilibration in controlled gas atmospheres. The samples were fractured in vacuum and high resolution XPS spectra of the fractured surfaces were measured. The peak positions and peak shape parameters of Fe 3p for Fe²⁺ and Fe³⁺ were derived from the Fe 3p XPS spectra of the standard samples of 2FeO·SiO₂ and Fe₂O₃, respectively. Using these parameters, the Fe 3p peaks of Fe₃O₄ and Fe_1−yO are analysed. The results indicate that high resolution XPS techniques can be used to determine the Fe²⁺/Fe³⁺ ratios in metal oxides. The technique has the potential for application to other transition metal oxide systems.     

Evaluation of ligand field stablization in spinels using mössbauer determined cation distributions

The Mössbauer determined cation distributions of FeV₂O₄, FeCr₂O₄, FeMn₂O₄, Fe₃O₄, FeCo₂O₄, CoV₂O₄, CoCr₂O₄, CoMn₂O₄, CoFe₂O₄ and Co₃O₄ are compared with the quantitative d-orbital stablization energies of McClure and of Dunitz and Orgel. They are also compared with the qualitative ligand field stabilization energies of Cotton. These theories do not account for observation in the cases of FeMn₂O₄, FeCo₂O₄ and CoFe₂O₄.     

Effect of nano-Y2O3 on microstructure of laser cladding cobalt-based alloy coatings

Cobalt-based alloy coatings with and without nano-Y₂O₃ particles produced by a 5 kW CO₂ laser on Ni-based superalloy were introduced. Solidified microstructure, phase compositions and distribution of nano-particles were investigated by using optical microscope, SEM, TEM and XRD. The results showed that metastable phases, such as γ-Co and Cr₂₃C₆ existed in cobalt-based alloy coatings. Another two phases (Y₂O₃ and ?-Co) were found by adding nano-Y₂O₃. Without nano-Y₂O₃, rapid directional solidified microstructure of columnar dendrite appeared. Fine and short dendritic microstructure and columnar to equiaxed transition (CET) occurred by adding nano-Y₂O₃ particles. With the increase in amount of nano-Y₂O₃, fully equiaxed crystallization appeared and the formation mechanism was analyzed. The results also showed that the sub-microstructure of the coatings changed from dislocation to stacking fault by adding nano-Y₂O₃.