RBS/channeling studies on the heteroepitaxially grown Y2O3 film on Si(100)

The heteroepitaxially grown yttrium oxide layer by an ionized cluster beam (ICB) on a Si(100) substrate was investigated by Rutherford backscattering spectrometry (RBS)/channeling. The channeling minimum value (χ_min) of the Y₂O₃ layer on Si(100) is 0.28, and this is the smallest value among those reported. From the channeling polar plots, it is found that Y₂O₃ film grown on Si(100) oriented with (110) direction and has a double domain structure. The 110 axis of Y₂O₃ layer is exactly parallel to the 100 axis of the Si substrate. It is also observed that the interface region of Y₂O₃ film has more crystalline defects than the surface region.     

Yttrium sesquioxide, Y2O3, thin films deposited on Si by ion beam sputtering: microstructure and dielectric properties

Y₂O₃ thin films were in-situ deposited by ion beam sputtering on Si substrate. The influence of the deposition parameters are studied by X-ray diffraction, electrical measurements and high resolution transmission electron microscopy observations. The stress sate of the oxide layers is investigated by the sin²ψ method as a function of the deposition parameters and the post-annealing treatments. Oxygen ion beam assisted deposition process or post-annealing of as-deposited thin films lead to the same relaxation of the internal compressive stress within the oxide layer. An SiO₂ layer sandwiched between Si and Y₂O₃ is always observed and should play a role both in the growing process and electrical properties of the MOS structure based on Y₂O₃ oxide layer. The results are interpreted in terms of diffusional process in the oxide, which are directly related to the temperature and the oxygen partial pressure during the growth process.     

Ion beam assisted texturing of polycrystalline Y2O3 films deposited via electron-beam evaporation

Ion-beam assisted deposition of polycrystalline Y₂O₃ films using e-beam evaporation was investigated. For growth on non-crystalline substrates, low temperature growth yields randomly oriented polycrystalline material. At elevated temperature, surface energy anisotropy yields a (111) uniaxial texture. For film deposition with irradiation from an Ar ion beam, the out-of-plane texture remained (111) in orientation. The incident Ar ion beam induces an in-plane alignment of the Y₂O₃ films that is relatively broad. A six-fold symmetry in the out-of-plane X-ray diffraction phi-scans was observed for the (111) textured Y₂O₃ films, indicating a multi-variant in-plane texture and suggesting anisotropic damage along both the (110) and (100) projections. The lack of a sharp, single variant in-plane texture with ion beam irradiation is consistent with the relatively weak bond strength in Y₂O₃.     

纳米Al2O3和TiO2改性有机硅涂层对304不锈钢高温氧化行为的影响

本文以纳米Al₂O₃和TiO₂为主要填料,采用物理混合方法制备了两种纳米改性有机硅涂料,将涂料喷涂于马口铁和304不锈钢表面并室温干燥,获得了两种涂层样品。测试了两种涂层的常规机械性能,研究了600℃空气中涂层对304不锈钢抗氧化性能的影响。结果表明：两种涂层均具有良好的附着力、柔韧性和耐冲击性能。两种涂层均能有效减缓304不锈钢在600℃下的氧化;当纳米Al₂O₃和TiO₂含量比例为4:1时,纳米改性有机硅涂层对304不锈钢的防护效果最佳。     

The influence of substrate chemistry on the adhesion of electrolessly deposited Ni(P) on metal oxide coated ceramics

The adhesion of electrolessly deposited Ni(P) on alumina ceramic substrates which were coated with thin SiO₂, SnO₂, TiO₂, Al₂O₃, Y₂O₃, ZrO₂ and (In,Sn)O_x (ITO) films was studied. The adhesion was measured with the aid of the 90° peel test. Strong adhesion of Ni(P) was found for the substrates with ZrO₂ and Al₂O₃ coatings and weak adhesion for the substrates with SiO₂, TiO₂, SnO₂, Y₂O₃ and ITO coatings. The fracture path and the type of interfacial bonding were analysed using scanning electron microscopy, energy-dispersive analysis of X-rays and X-ray photoelectron spectroscopy. In the case of the strongly adhering samples, fracture took place through the metal layer and along the interface. In the case of the weakly adhering samples only interfacial failure was observed between the Ni(P) layer and the metal oxide coating. Cross-section transmission electron microscopy studies of the interfaces suggested that the differences in peel energy values are caused by differences in micromechanical interlocking at the metal oxide-Ni(P) interface. In addition, a weak boundary layer which was found to be present at the Ni(P)-alumina interface was absent in the case of the strongly adhering samples with the ZrO₂ substrate coating.     

TiAl合金表面Si-Al-Y共渗层的组织及高温抗氧化性能

通过在1050℃下Si-Al-Y扩散共渗0~4 h在TiAl合金表面制备了Al、Y改性的硅化物抗氧化渗层, 分析了共渗层的结构及相组成, 并对其组织形成机理及高温抗氧化性能进行了研究。结果表明: 1050℃共渗4 h所制备的共渗层具有多层结构, 由外向内依次为TiSi₂外层、(Ti,X)₅Si₄及(Ti,X)₅Si₃(X表示Nb, Cr)中间层、TiAl₂和γ-TiAl内层及富Al的过渡层, 其中Y元素主要富集于共渗层的外层和中间层。不同时间共渗的结果表明, Si-Al-Y共渗层的形成是一个在基体表面先沉积Al, 后沉积Si的有序过程。经1000℃高温氧化20 h后共渗层表面形成了由TiO₂外层及SiO₂·Al₂O₃次外层组成的致密氧化膜; Y的氧化物主要存在于氧化膜与残余共渗层的界面处, 能够有效地增强膜层的附着力。     

Atomic layer deposition of calcium oxide and calcium hafnium oxide films using calcium cyclopentadienyl precursor

Calcium oxide and calcium hafnium oxide thin films were grown by atomic layer deposition on borosilicate glass and silicon substrates in the temperature range of 205–300 °C. The calcium oxide films were grown from novel calcium cyclopentadienyl precursor and water. Calcium oxide films possessed refractive index 1.75–1.80. Calcium oxide films grown without Al₂O₃ capping layer occurred hygroscopic and converted to Ca(OH)₂ after exposure to air. As-deposited CaO films were (200)-oriented. CaO covered with Al₂O₃ capping layers contained relatively low amounts of hydrogen and re-oriented into (111) direction upon annealing at 900 °C. In order to examine the application of CaO in high-permittivity dielectric layers, mixtures of Ca and Hf oxides were grown by alternate CaO and HfO₂ growth cycles at 230 and 300 °C. HfCl₄ was used as a hafnium precursor. When grown at 230 °C, the films were amorphous with equal amounts of Ca and Hf constituents (15 at.%). These films crystallized upon annealing at 750 °C, showing X-ray diffraction peaks characteristic of hafnium-rich phases such as Ca₂Hf₇O₁₆ or Ca₆Hf₁₉O₄₄. At 300 °C, the relative Ca content remained below 8 at.%. The crystallized phase well matched with rhombohedral Ca₂Hf₇O₁₆. The dielectric films grown on Si(100) substrates possessed effective permittivity values in the range of 12.8–14.2.     

Ultraviolet emitting (Y1−xGdx)2O3−δ thin films deposited by radio frequency magnetron sputtering: Combinatorial modeling, synthesis, and rapid characterization

Gadolinium-doped, yttrium oxide thin films have been deposited on silicon (001) substrates by radio-frequency (RF) magnetron reactive sputtering that exhibit cathodoluminescence (CL) at ultraviolet frequencies. The maximum CL brightness occurred at λ314–315 nm characteristic of the ⁶P_3 / 2 → ⁸S (λ = 314 nm) transition observed in Gd-doped, yttrium oxide powders. The radiative recombination takes place at the rare earth activator Gd³⁺ site embedded in the Y₂O_3−δ host; the optical transition resides within the band gap of the Y₂O_3−δ host and the transition observed is characteristic of atomic gadolinium. A combinatorial approach to sputtering was used to deposit a film of variable composition from 1 to 23 at.% Gd in Y₂O_3−δ in order to rapidly discern the composition node of optimal CL brightness. A simulation was created for the purpose of predicting the film combinatorial composition for binary and ternary alloys prior to sputtering experiments in order to facilitate our combinatorial thin film synthesis technique. The model prediction varied from the real experimental composition profile by only 2.2 at.% Gd ± 1.6 at.% proving the predictor as a useful aide to complement combinatorial thin film experiments. A film of composition Y_1.56Gd_0.44O_3.25 (8.3 at.% Gd) yielded the maximum CL brightness. CL brightness increased continuously up to the 8.3 at.% Gd composition due to the increased number of activators present in the host. Beyond this composition the brightness drastically decreased. The oxygen composition in the combinatorial film was strongly dependent on the Gd composition; films were sub-stoichiometric δ > 0 below 6 at.% Gd and was over-stoichiometric δ < 0 beyond this composition.     

Co对Ti45Al-8Nb-0.3Y合金组织结构和高温抗氧化性能的影响EI北大核心CSCD

采用真空电弧非自耗熔炼方法制备Ti45Al-8Nb-0.3Y-m Co(m=0,0.5,1,2,原子分数/%,下同)合金,研究合金的组织和高温抗氧化性能。结果表明:Co能够明显细化TiAl-Nb合金组织,但对合金中α_(2)+γ片层组织的形成具有较强烈的抑制作用,并且会促进富Co的B_(2)相析出。Ti45Al-8Nb-0.3Y-mCo合金在1000℃空气中氧化100 h后形成的氧化膜均主要由较为疏松的TiO_(2)和Al_(2)O_(3)混合组成,且TiAl-Nb-0.3Y合金的氧化增重随Co含量增加而增大,但氧化膜的抗剥落能力随Co含量增加而明显提高;添加Co能够在一定程度上降低氧化膜的内应力,对提高其抗剥落性能有益,但引起的粗大B_(2)相析出削弱了合金的高温抗氧化性能。     

层状硅酸钇改性SiCf/SiC复合材料湿氧化行为研究

研究了层状硅酸钇的引入对SiC_f/SiC复合材料湿氧化行为的影响。首先通过硝酸钇乙醇溶液浸渍热解法向碳化硅纤维引入Y₂O₃, 再采用化学气相渗透法沉积SiC。层状Y₂Si₂O₇主要通过Y₂O₃与沉积过程中的SiC反应转化而成。研究发现, Y₂Si₂O₇在1400 ℃湿氧环境条件下发生富集, 在氧化层表面形成保护层。氧化80 h后, 单层和多层Y₂Si₂O₇改性的SiC_f/SiC复合材料强度保留率分别达到60.38%和71.93%, 而没有改性的SiC_f/SiC复合材料强度保留率仅为50.11%。结果表明: 层状Y₂Si₂O₇的引入可显著提升SiC_f/SiC复合材料在湿氧环境的抗氧化性能。     

Growth of calcium carbonate by the atomic layer chemical vapour deposition technique

Thin films of CaCO₃ (calcite) have been grown with the atomic layer chemical vapour deposition (ALCVD) technique, using Ca(thd)₂ (Hthd=2,2,6,6-tetramethylheptan-3,5-dione), CO₂, and ozone as precursors. Pulse parameters for the ALCVD-type growth are found and self-limiting reaction conditions are established between 200 and 400 °C. Calcium carbonate films have been deposited on soda-lime glass, Si(100), -Al₂O₃(001), -Al₂O₃(012), -SiO₂(001), and MgO(100) substrates. The observed textures were: in-plane oriented films with [100](001)CaCO₃ [100](001)Al₂O₃ and [100](001)CaCO₃[110](001)Al₂O₃ on -Al₂O₃(001), amorphous films on -Al₂O₃(012) when grown at 250 °C, and columnar oriented films on soda-lime glass, Si(001), -SiO₂(001), and MgO(100) substrates with (00l) and (104) parallel to the substrate plane at 250 and 350 °C, respectively. The film topography was studied by atomic force microscopy and AC impedance characteristics were measured on as-deposited films at room temperature. The films were found to be insulating with a dielectric constant (_r) typically approximately 8. Thin films of CaO were obtained by heat treatment of the carbonate films at 670 °C in a CO₂-free atmosphere, but the thermal decomposition led to a significant increase in surface roughness.     

FeCr-ODS铁素体合金的氧化+粉锻工艺制备及其微观结构

提出一种氧化+粉锻(粉末锻造)新工艺并用其制备了FeCr-ODS铁素体合金。使用SEM、XPS、EPMA和TEM等手段对其表征,研究了粉末表面和内部氧化物的生成、演变以及合金中纳米氧化物弥散相的种类和分布特征。结果表明,在低温氧化过程中粉末表面生成了一层Fe的氧化膜,在随后的加热过程中粉末表面的O元素转移并与Y和Ti元素反应生成了Y-Ti-O纳米氧化物弥散相。通过纳米氧化物弥散相在粉末成型过程中的演变,阐明了粉锻对位错和纳米氧化物析出相形成的贡献。用这种工艺制备的ODS铁素体合金,大量细小的Y₂TiO₅析出相均匀地分布在基体中,晶界上只有少量大颗粒Y₂O₃。     

Multi-composition oxidation resistant coating for SiC-coated carbon/carbon composites at high temperature

This work proposes a multi-composition oxidation resistant coating for SiC-coated carbon/carbon (C/C) composites by slurry method using the mixture of Y₂O₃, ZrO₂, Al₂O₃, Si and C. XRD analysis shows that the phases of the composite coating are composed of SiC, Al₂O₃, Y₂O₃, ZrO₂, Al₄SiC₄ and Y₃Al₂(AlO₄)₃. SEM analysis of the cross section of the coating displays the microstructure with 500 μm thickness which filled the porous SiC. Oxidation test shows that, after 19 h oxidation in air at 1873 K, the weight loss of the coated SiC-C/C is only 1.76%. The oxidation of the coated C/C composites was primarily due to the reaction of C/C matrix and oxygen diffusing through the penetrable cracks and bubble holes in the coating.     

不锈钢表面阴极微弧电沉积氧化铝膜层的性能

以0.4 mol/L Al（NO₃）₃乙醇溶液为电解液,用阴极微弧电沉积方法在304不锈钢表面制备了80μm厚的氧化铝膜层。分析了膜层的形貌、成分和相组成,测试了膜层的抗高温氧化和电化学腐蚀性能。结果表明.电沉积膜层由γ-Al₂O₃和α-Al₂O₃组成。膜层中含有少量的Fe、Cr、Ni元素,表明膜/基界面附近的不锈钢基体在微弧放电作用下也参与氧化铝膜层的沉积和烧结过程。氧化铝膜层使不锈钢在800℃恒温氧化速率明显降低,表明其抗高温氧化性能得到提高。同时,其腐蚀电位正向移动,腐蚀电流密度降低1个数量级,表明其耐腐蚀性能得到提高。     

Aqueous solution-based synthesis of rare earth-doped metal oxide thin films

Rare earth-doped TiO₂ thin films have been successfully formed on glass and Si wafer substrates from aqueous solution through equilibrium reaction between metal–fluoro complex and metal oxide, in which Ln³⁺–ethylenediaminetetraacetic acid (EDTA) complex (Ln: rare earth metal) was added into the reaction solution. Ln/Ti ratio and crystalline structure of the film could be controlled by varying the initial concentration of Ln³⁺–EDTA complex solution. The obtained Ln-doped films were densely-packed and had no cracks.     

Formation of a highly oriented FeO thin film by phase transition of Fe3O4 and Fe nanocrystallines

A highly oriented FeO thin film was formed from a Fe₃O₄ thin film containing Fe nanocrystallines by post-annealing at 600°C. Fe₃O₄ thin films were grown on Si(100) substrates by ion beam sputter deposition under oxygen ambient. The stoichiometry of the iron oxide thin film could be precisely controlled by in situ X-ray photoelectron spectroscopy (XPS). X-ray diffraction (XRD) pattern of the Fe₃O₄ thin film grown at substrate temperature of 300°C showed a mixed phase of Fe₃O₄ and Fe nanocrystallines with a preferred orientation (110). However, the mixed phase was converted to a highly oriented FeO(200) phase by post-annealing at 600°C. This could be inverted as a result of Ostwald ripening of the Fe₃O₄ and Fe nanocrystallines.     

Microstructure, crystallinity, and properties of low-pressure MOCVD-grown europium oxide films

A study of growth, structure, and properties of Eu₂O₃ thin films were carried out. Films were grown at 500–600 °C temperature range on Si(1 0 0) and fused quartz from the complex of Eu(acac)₃·Phen by low pressure metalorganic chemical vapor deposition technique which has been rarely used for Eu₂O₃ deposition. These films were polycrystalline. Depending on growth conditions and substrates employed, these films had also possessed a parasitic phase. This phase can be removed by post-deposition annealing in oxidizing ambient. Morphology of the films was characterized by well-packed spherical mounds. Optical measurements exhibited that the bandgap of pure Eu₂O₃ phase was 4.4 eV. High frequency 1 MHz capacitance–voltage (C–V) measurements showed that the dielectric constant of pure Eu₂O₃ film was about 12. Possible effects of cation and oxygen deficiency and parasitic phase on the optical and electrical properties of Eu₂O₃ films have been briefly discussed.     

Preparation of strontium titanate thin films by mirror-confinement-type electron cyclotron resonance plasma sputtering

Using mirror-confinement-type electron cyclotron resonance (ECR) plasma sputtering method, strontium titanate (SrTiO₃) thin films have been prepared on Si and Pt/Ti/SiO₂/Si substrates at a low substrate temperature (below 450 K) in a low pressure (2.7×10⁻² Pa) environment of pure Ar and Ar/O₂ mixture. Prepared film surfaces were very smooth regardless of high deposition rate (8.5 nm/min). The composition ratio Sr/Ti of Sr to Ti in the films varied with the distance between the target and the substrate. All as-deposited films on Si substrates were found to be amorphous and were crystallized by post-deposition annealing using an electric furnace at 650 K, i.e. approximately 250 K lower than annealing for films obtained by conventional RF magnetron sputtering. Post-deposition annealing of these films using millimeter-wave radiation decreased the crystallization temperature to a value of 550 K. Furthermore, all as-deposited films on Pt/Ti/SiO₂/Si substrates by a plasma of Ar and O₂ gas mixture were found to be crystallized regardless of no substrate heating.     

Deposition of Sm2O3 doped CeO2 thin films from Ce(DPM)4 and Sm(DPM)3 (DPM=2,2,6,6-tetramethyl-3,5-heptanedionato) by aerosol-assisted metal–organic chemical vapor deposition

Samarium-doped ceria (SDC) thin films were prepared from Sm(DPM)₃ (DPM = 2,2,6,6-tetramethyl-3,5-heptanedionato) and Ce(DPM)₄ using the aerosol-assisted metal–organic chemical vapor deposition method. -Al₂O₃ and NiO-YSZ (YSZ = Y₂O₃-stabilized ZrO₂) disks were chosen as substrates in order to investigate the difference in the growth process on the two substrates. Single cubic structure could be obtained on either -Al₂O₃ or NiO-YSZ substrates at deposition temperatures above 450 °C; the similar structure between YSZ and SDC results in matching growth compared with the deposition on -Al₂O₃ substrate. A typical columnar structure could be obtained at 650 °C on -Al₂O₃ substrate and a more uniform surface was produced on NiO-YSZ substrate at 500 °C. The composition of SDC film deposited at 450 °C is close to that of precursor solution (Sm : Ce = 1 : 4), higher or lower deposition temperature will both lead to sharp deviation from this elemental ratio. The different thermal properties of Sm(DPM)₃ and Ce(DPM)₄ may be the key reason for the variation in composition with the increase of deposition temperature.     

Epitaxial and polycrystalline BaFe12O19 thin films grown by chemical vapour deposition

Epitaxial and polycrystalline barium hexaferrite BaFe₁₂O₁₉ thin films were prepared by metalorganic chemical vapour deposition (MOCVD). Films were grown by a liquid MOCVD technique which aim is to control precisely the precursor vapour pressures. Two kinds of substrates were used: sapphire (001) and silicon thermally oxidized. On Si/SiO₂ films are polycrystalline and the magnetization is isotropic. On Al₂O₃ (001), structural studies reveal the films to be predominantly single phase, well crystallized without annealing procedure and with the c-axis perpendicular to the film plane; epitaxial relationships between the film and the substrate were determined. The magnetic parameters, deduced from vibrating sample magnetometer measurements, show a high dependence of the magnetization with the orientation of the field with respect to the surface of the film.