Radio frequency dielectric dissipation measurements on yttrium oxide thin films

The dielectric dissipation factor (tan δ) of evaporated thin film Al-Y₂-O₃-Au capacitors has been measured in the frequency range 1 kHz-40 MHz. The yttrium oxide films (≈ 5000 Å) were fabricated by the direct electron-beam evaporation of 99.9% Y₂O₃ powder. The geometry of these capacitors (≈ 40 pF) deposited on alumina substrates provided large contact pads for direct attachment to the measuring bridges. Lead inductance was minimal while lead and contact resistance was less than 0.2 ω. Tan δ measurements were made at 20°C with a capacitance bridge, a Wayne Kerr bridge and a Q-meter at appropriate frequencies. At 1 kHz, tan δ values of various specimens varied from 0.004–0.009. These values decreased rapidly with increasingly frequency, however, to a resistance-corrected constant value tan δ≦0.004 over the range 100 kHz-40 MHz.     

Transparent yttrium oxide ceramics

Transparent discs of yttrium oxide, one centimeter in diameter by several millimeters thick, have been produced by hot forging under vacuum at 950°C and 10,000–12,000 psi for 48 hours. Lithium fluoride, required to produce full transparency, is eliminated during the sintering process. Optical absorption spectra of the hot-forged samples are nearly identical to those reported for single crystals.     

Synthesis of europium-doped yttrium hydroxide and yttrium oxide nanosheets

A new approach has been developed for the preparation of Y(OH)₃:Eu and Y₂O₃:Eu nanosheets using the sol–gel method and hydrothermal reactions. XRD patterns showed that the product was purely hexagonal-phase Y(OH)₃. TEM images revealed that the nanosheets are square shaped (1 × 1 μm²) with a thickness of several tens of nanometers. In addition, it was found that cubic-phase Y₂O₃ nanosheets can be obtained by calcination of Y(OH)₃ at 900 °C for 1 h. More importantly, the thus-prepared Y(OH)₃:Eu and Y₂O₃:Eu nanosheet phosphors were found to exhibit a relatively high photoluminescence (PL) intensity.     

氧化钇纳米粉体材料的制备

以YCl3为原料 ,以Na2 CO3为添加剂 ,聚乙二醇 4 0 0为分散剂 ,首先制备出晶粒细小的碳酸钇前驱体。在 70 0℃焙烧 1h后制得Y2 O3纳米粉体材料 ,经XRD和TEM检测 ,粒径为 5 0nm ,粒度均匀     

Dielectric properties of polycrystalline CaTiO3 doped with yttrium oxide

Y³⁺ was substituted for Ca²⁺ in polycrystalline CaTiO₃ in amounts up to 15 at %. Sintering conditions (1450° C, 15 h) were such that grain sizes were > 25 m. Stoichiometry was adjusted on the assumption that the excess charge of the dopant was compensated by the creation of calcium vacancies. This assumption was supported by measurements of the Ca/Ti ratio in the grains by electron-probe microanalysis. Unlike yttrium-doped SrTiO₃, material sintered in air was light-coloured with no evidence of semiconductivity. On the other hand, when sintering was done in nitrogen, dielectric relaxation characteristic of boundary layers was observed for dopant levels > 1 mol %. The experimental data support the view that dielectric relaxation in SrTiO₃ and CaTiO₃ results from semiconducting grains with resistive surface layers and that the semiconductivity arises because oxygen loss from the grains during sintering is increased by donor doping.     

Silicon structures with dielectric insulation obtained by vertical anisotropic etching

Silicon structures with vertical insulating walls were prepared for multielement devices with high element packing density requiring deep pockets in silicon single crystals. The technology is based on the anisotropic etching of (110)-oriented silicon crystals and filling the etch grooves with an organosilicon polymer based suspension.     

Mechanical behavior of zirconium dioxide crystals partially stabilized with yttrium oxide

The results are given of a composite investigation of the mechanical behavior of single crystals of zirconium dioxide partially stabilized with yttrium oxide and ytterbium oxide at temperatures up to 1400°C. It is shown that the elastic modulus of these materials lies in the 150–350 GPa range and their tensile strengths may reach 1,688 MPa. These materials have a nonincreasing relationship of the stress intensity factor to crack length (flat R-curves). The stress intensity factors determined on specimens with a sharp crack are significantly lower than on specimens with a notch. The picture of fracture of single crystals in penetration of an indentor, etc. differs significantly in relation to the stabilizing addition.Translated from Problemy Prochnosti, No. 1, pp. 73–77, January, 1991.     

Silicon metal-semiconductor-metal photodetector with zinc oxide transparent conducting electrodes

Transparent conducting oxides thin layers, due to their optical and electrical properties, can be used as transparent electrodes in various optoelectronic devices. We present a metal-semiconductor-metal photodiode (MSM-PD) on silicon as optically active layer with zinc oxide (ZnO) thin layer as interdigitated Schottky transparent electrodes. The advantage of using a ZnO thin layer as Schottky electrodes consists in the improvement of the photoresponse by eliminating the shadowing of the active area by opaque metallic electrodes. ZnO thin layers were deposited on 10 Ω cm resistivity silicon epitaxial wafers by the vacuum thermal evaporation method. High purity metallic powders were mixed with an (Al + Sn)/Zn ratio of 0.03. In order to obtain transparent layers the metallic depositions were thermally treated at 450 °C for 2 h. The Al, Sn co-doped ZnO layers of 0.5-0.8 μm were investigated regarding structural, optical and electrical properties and surface morphology. The obtained thin layers have a high transparency (T > 85%) over a large spectral range and the resistivity is quite low, ρ ~ 10^− 4 Ω cm. The interdigitated Schottky contacts of ZnO were configurated onto the optically active Si layer providing an MSM-PD structure of 0.143 mm² active area and finger spacing and finger width of 6 μm. The optoelectronic characteristics were measured and the Schottky barrier height of 0.62 eV was determined from the current-voltage characteristic. A responsivity of 0.2 A/W at 475 nm and a capacitance of 1.4 pF at 10 V bias were obtained for the MSM-PD structure with transparent conducting ZnO Schottky electrodes.     

Evaluation of the uncertainty budget in analyzing yttrium and its oxide using atomic-emission spectrometry with an inductively coupled plasma

The uncertainty budget for the results of analyzing yttrium and its oxide by atomic-emission spectrometry with an inductively coupled plasma is estimated. The main factors are revealed that make a contribution to the overall uncertainty of results: sample weight of the analyzed material, sample solution volume, and concentration of the element determined. A special method is used to study the effect of yttrium in the analytical signal of the impurities determined.     

Sub-micrometer sized yttrium oxide fibers prepared through hydrothermal reaction

Yttrium oxide fibers have been synthesized via hydrothermal reaction and subsequent thermal treatment using yttrium chloride as precursor. The products before and after the thermal treatment were characterized by powder X-ray diffractions (XRD), scanning electron microscopy (SEM), ion-chromatograph analysis, and thermogravimetry and differential thermal analysis (TG-DTA). The fiber diameter ranged from 100 to 300 nm, while the length was up to tens of microns. It was found that the chemical composition and morphology of the products were closely related to the pH value of reaction solution, and fibrous products could be obtained at pH 9.5-10.25. These oxide fibers exhibited outstanding high-temperature stability, which maintained their morphology at temperature up to 1400 °C.     

Templated synthesis of nanostructured europium-doped yttrium oxide thin films

An evaporation-assisted templating method was developed for the synthesis of nanostructured europium-doped yttrium oxide (Y₂O₃:Eu³⁺, YEO) thin films. The method involves spin-coating a solution containing yttrium salt and block copolymer followed by thermal oxidation. Uniform films with controllable thickness ranging from 100 to 500 nm were obtained by tuning the composition of the precursor solution and the processing conditions. However, the method was not completely general as extremes in salt or polymer concentration triggered uncontrolled cracking and texturing of the film. The photoluminescence was proportional to both the thickness and surface roughness. Nanocrystalline, porous YEO particles produced using the evaporation method exhibited an intrinsic quantum efficiency approximately 25% of that of particles with micron-sized crystallites.     

Eu3+ site characterization in solution-grown yttrium oxide

The site symmetry of impurity ions greatly influences the energy levels responsible for optical emission. The crystallographic sites that impurities occupy in a host material are largely determined by the ionic radius and charge of the impurity relative to the host cations. Solution processing provides a lower energy environment for the incorporation of impurity ions than melt-grown processes, raising questions regarding how optically active impurity ions are incorporated into solution processed materials. In the present report, trivalent europium impurity ions have been incorporated into yttrium oxide (Y₂O₃) powders via an alkoxide-hydrolysis technique. The europium impurities were incorporated into the hosts during the hydrolysis stage of the process. X-ray diffraction measurements confirm the yttrium oxide is of the same cubic form as the bulk crystal after heat treating to 800 °C. All samples emit bright luminescence at room temperature associated with the ⁵D₀ → ⁷F₂ transitions, with 394 nm excitation. Comparison of the emission and excitation spectra of the solution-grown samples to those of bulk materials, confirms that the optically active impurity ions are incorporated into the Y₂O₃ structure on the usual, C₂, cation sites.     

Preparation,characterization and dielectric behaviour of some yttrium doped strontium stannates

Samples of Sr_{(1− 3x/2)}YxSnO₃ are prepared by usual solid state reaction route. X- ray diffraction studies confirm the formation of single cubic perovskite single phase. The dielectric constant and dielectric loss at 1 kHz were measured in the temperature range from room temperature up to -150†C. The dielectric constant decreases and losses increase with increased yttrium content in the samples. The percentage porosity and unit cell parameters are also calculated for the samples.     

High-performance amorphous indium-gallium-zinc oxide thin-film transistors with polymer gate dielectric

The fabrication of amorphous indium-gallium-zinc oxide (a-IGZO) thin-film transistors (TFTs) with a spin-coated polymer gate dielectric on a glass substrate is reported. The interface state density at the poly(4-vinylphenol)/a-IGZO interface is only around 4.05 × 10¹¹ cm^− 2. The TFTs' threshold voltage, subthreshold swing, on-off current ratio, and carrier mobility are 2.6 V, 1.3 V/decade, 1 × 10⁵, and 21.8 cm²/V s, respectively. These characteristics indicate that the TFTs are suitable for use as nonvolatile memory devices and in flexible electronic applications.     

Preparation of porous yttrium oxide microparticles by gelation of ammonium alginate in aqueous solution containing yttrium ions

Porous Y₂O₃ microparticles 500 μm in size were obtained, when 1 wt%-ammonium alginate aqueous solution was dropped into 0.5 M-YCl₃ aqueous solution by a Pasteur pipette and the resultant gel microparticles were heat-treated at 1100°C. Small pores less than 1 μm were formed in the microparticles by the heat treatment. The bulk density of the heat-treated microparticle was as low as 0.66 g cm^?3. The chemical durability of the heat-treated microparticles in simulated body fluid at pH = 6 and 7 was high enough for clinical application of in situ radiotherapy. Although the size of the microparticles should be decreased to around 25 μm using atomizing device such as spray gun for clinical application, we found that the porous Y₂O₃ microparticles with high chemical durability and low density can be obtained by utilizing gelation of ammonium alginate in YCl₃ aqueous solution in this study.     

The effect of hydrogen on the electric conductivity of tin oxide doped with yttrium

Amorphous films of tin oxide doped with yttrium were obtained by ion beam sputter deposition. After crystallization, the films acquired a nanocrystalline structure. The introduction of yttrium leads to an increase in the crystallization temperature of tin oxide. The electric conductivity of films containing yttrium in excess of 1 at. % is highly sensitive to hydrogen. Nanocrystalline films of tin oxide doped with yttrium may serve as hydrogen-sensitive media.