Novel silicon surface passivation by porous silicon combined with an ultrathin Al2O3 film

We report on a dual passivation approach of monocrystalline-silicon (c-Si), which combines porous silicon (PS) treatment and pulsed laser deposition (PLD) of Al₂O₃ ultrathin layer. Al₂O₃ ultrathin films were deposited, under an oxygen background pressure of 10 mTorr. In this work we demonstrate that the dual treatment Al₂O₃/PS provide excellent passivation quality of c-Si surfaces. Surface passivation and reflectivity properties are investigated before and after heat treatment at 700 °C. The level of surface passivation is quantified using photoconductance and Fourier-transform infra-red absorption techniques. X-ray diffraction analysis suggested that the heat treatment leads to an average crystallite size decrease which help the diffusion of the Al₂O₃ NPs along the wafer surface. As a result, the effective minority carrier lifetime increases from 2 to 7 μs. Our results demonstrate that this dual treatment not only provides strong passivation of the c-Si substrate but decreases also the total surface reflectivity at 500 nm (from 28 % for untreated c-Si samples to ～7 % for Al₂O₃/PS treated ones).     

Influence of surface modification of alumina on bond strength in Al2O3/Al/Al2O3 joints

The subject of the work was to study the effect of Ti thin film on alumina ceramic on mechanical strength and fracture character of Al₂O₃/Al/Al₂O₃ joints. The joints were formed by liquid state bonding of alumina substrates covered with titanium thin film of 800 nm thickness using Al interlayer of 30μm thickness at temperature of 973 K in a vacuum of 0.2 mPa for 5 min. The bend strength was measured by four–point bending test at room temperature. Scanning and transmission electron microscopy were applied for detailed characterization of interface structure and failure character of fractured joint surfaces. Result analysis has shown that application of the Ti thin film on alumina leads to decrease of bond strength properties of Al₂O₃/Al/Al₂O₃ joints along with the change either of structure and chemistry of interface or of failure character.     

Surface passivation of multicrystalline silicon wafers by porous silicon combined with an ultrathin nanoparticles aluminum coating film

In this paper, we demonstrate that we may efficiently improve surface passivation of multi-crystalline silicon (mc-Si) while combining formation of porous silicon (PS) and deposition of ultrathin aluminum (Al) film. Aluminum Nanoparticles were deposited by thermal evaporation onto PS formed on mc-Si wafers. Optoelectronic properties of Al/PS/mc-Si and Al/mc-Si treated samples were investigated before and after annealing in the 400–700 °C temperature range. The surface passivation effectiveness was pointed out based on minority carrier lifetime and photoluminescence measurements. It was found that, at a minority carrier density Δn = 10¹⁵ cm^?3, the effective minority carrier lifetime increases from 1.5 μs (for the bare mc-Si wafer) to about 6 and 14 μs before and after thermal annealing, respectively. FTIR analyses show strong correlation between the minority carrier lifetime values and hydrogen and Al passivation. Major beneficial effect of the co-presence of Al and Al–O on the optoelectronic properties is also demonstrated. The reflectivity of Al/PS treated mc-Si decrease significantly at 500 nm as compared to untreated mc-Si (from 31 % for untreated mc-Si wafers to 8 % for Al/PS treated ones), which is due to the roughly ordered structure and to the Al nanoparticles.     

Al2O3/silicon nanoISFET with near ideal nernstian response

Nanoscale ISFET (ion sensitive field-effect transistor) pH sensors are presented that produce the well-known sub-nernstian pH-response for silicon dioxide (SiO(2)) surfaces and near ideal nernstian sensitivity for alumina (Al(2)O(3)) surfaces. Titration experiments of SiO(2) surfaces resulted in a varying pH sensitivity ～20 mV/pH for pH near 2 and >45 mV/pH for pH > 5. Measured pH responses from titrations of thin (15 nm) atomic layer deposited (ALD) alumina (Al(2)O(3)) surfaces on the nanoISFETs resulted in near ideal nernstian pH sensitivity of 57.8 ± 1.2 mV/pH (pH range: 2-10; T = 22 °C) and temperature sensitivity of 0.19 mV/pH °C (22 °C ≤ T ≤ 40 °C). A comprehensive analytical model of the nanoISFET sensor, which is based on the combined Gouy-Chapman-Stern and Site-Binding (GCS-SB) model, accompanies the experimental results and an extracted ΔpK ≈ 1.5 from the measured responses further supports the near ideal nernstian pH sensitivity.     

ZrO2/Al2O3多孔陶瓷的制备与力学性能

采用凝胶-发泡法制备了ZrO2/Al2O3多孔陶瓷,研究了陶瓷浆料的流变性,固相含量对多孔陶瓷坯体显微结构与力学性能的影响,以及烧结助剂MgO含量与多孔陶瓷抗压强度及气孔率之间的关系.结果表明,在分散剂含量为0.4％(质量分数),球磨4 h,pH值为4的条件下,陶瓷浆料的黏度较低,有利于凝胶注模.固相含量增加,坯体气孔率下降.过高的固相含量使浆料流动困难,注模时引入空气导致坯体内形成较大的气孔甚至裂纹,使坯体抗压强度下降.由ZrO2引起的相变增韧及微裂纹增韧可有效改善多孔陶瓷的力学性能.随烧结助剂含量增加,多孔陶瓷气孔支撑体致密化程度增大,气孔率降低,抗压强度明显升高.多孔陶瓷的抗压强度最高达30 MPa.引入适量的ZrO2及烧结助剂,可制备气孔率适中、抗压强度高的多孔陶瓷.     

Al2O3/Al2O3 Joint Brazed with Al2O3-particulate-contained Composite Ag-Cu-Ti Filler Material

1.IntroductionTo improve the mechanical properties and relieve mis-matches between the filler metals and base materials,the particulates of superalloys,ceramic or carbon fiberswere added into the conventional brazing filler metal toform composite filler material.The method has beenused in aero-engine component repairing[1,2],fine castcomponent joining[3],wide clearance butt jointing[4],ce-ramic brazing[5,6]and electronic package[7].However,the method was used mostly in metal brazing.The mi-cro…     

Al2O3/TiO2 multilayer passivation layers grown at low temperature for flexible organic devices

In this study, the permeability of passivation layers consisting of aluminum oxide (Al2O3) and titanium oxide (TiO2) was examined. The films were deposited on poly(ether sulfone) (PES) substrates via electron cyclotron resonance atomic layer deposition (ECR-ALD) at various deposition temperatures. The optimum plasma power and deposition temperature were investigated through measurements of the refractive index and packing density of the Al2O3 and TiO2 films. A buffer layer/multilayer structure was proposed in this study to improve the passivation barrier performance. A low water vapor transmission rate (WVTR) of approximately 5 x 10(-3) g/m2 x day was achieved with two Al2O3/TiO2 stacks with thicknesses of 40 nm deposited at 80 degrees C. Based on the Arrhenius rate equation, the activation energy of water vapor transmission through different passivation structures was examined. The activation energies of Al2O3, Al2O3/TiO2, and two Al2O3/TiO2 stacks with thicknesses of 40 nm were 51.8, 63.9, and 74.7 kJ/mol, respectively.     

光悬浮区熔定向凝固Al2O3/Er3Al5O12和Al2O3/Yb3Al5O12共晶陶瓷的制备与性能研究

本研究探索了光悬浮区熔法制备Al₂O₃/Er₃Al₅O₁₂(ErAG)和Al₂O₃/Yb₃Al₅O₁₂(YbAG) 定向凝固共晶陶瓷。在10 mm/h的抽拉速率下成功获得了凝固组织均匀、内部无裂纹或孔洞的高质量共晶陶瓷。通过高分辨三维X射线衍射仪研究了Al₂O₃和RE₃Al₅O₁₂在三维空间的分布与组织结构; 利用电子背散射衍射技术分析了定向凝固末期Al₂O₃和RE₃Al₅O₁₂两相的晶体学择优取向和相界面关系。力学性能表征结果显示, Al₂O₃/ErAG和Al₂O₃/YbAG具有优异的力学性能, 二者的维氏硬度分别为(13.5±0.4)和(12.8±0.1) GPa;断裂韧性分别为(3.0±0.2)和(3.2±0.1) MPa·m^1/2。     

Alumina gels that form porous transparent Al2O3

Formation of a porous transparent Al₂O₃ from aluminium alkoxides has been previously reported. During the process, alkoxides are hydrolyzed and the resultant hydroxide is peptized to a clear sol. The sol then must be gelled and pyrolyzed to 500° C to obtain the aluminium oxide. This paper discusses the gel state and the requirements for the system to retain its integrity during the drying and pyrolysis. Influence of electrolytes on the sol-gel transformation shows that there is a critical electrolyte concentration at which the gelling volume goes through a pronounced minimum. Deviation in either direction of this electrolyte concentration causes a sharp increase in the relative gelling volume and detrimentally effects the capability of the gel to retain its integrity. The sols that gel at concentrations less than ～4 g equivalent oxide per 100 ml do not retain their integrity during pyrolysis.     

Al2O3/Ti-Al复合材料中Al2O3晶须的原位合成

利用氧对金属Ti、Al粉的部分氧化,原位合成了含有氧化铝晶须的Al2O3/Ti-Al复合材料,通过XRD和SEM等测试手段,发现Al2O3晶须呈网状交叉分布于基体内部的孔隙中.分析了晶须的生成机理,认为氧化铝晶须是通过VLS机理生成,复合材料的原始组成和温度对晶须的显微型貌有直接的影响:随原始组成中铝含量的增加,产物中晶须的数量总体上是在递增的,且发达程度逐渐提高;热处理温度对晶须直径有直接影响,温度升高可以增加晶须直径.     

硅基HA/Al2O3复合生物涂层的制备与表征

通过磁控溅射沉积、阳极氧化与溶胶-凝胶结合的多步技术在Si(100)表面制备了HA/Al2O3复合生物涂层材料.采用TG-DSC测定了复合涂层中HA外层的烧成温度,采用XRD、FT-IR以及EDS分析了Si(100)基HA/Al2O3复合生物涂层的组成,并借助SEM研究了复合涂层的表面与截面的微观形貌.研究表明,凝胶完全转变为HA外层的最低温度约为550℃,凝胶经600℃处理30min后可在Si(100)-Al2O3基上形成具有一定数量纳米细孔且含有少量CO3的HA外层;A外层嵌入Si(100)基阳极氧化Al2O3多孔层的孔洞中构成HA/Al2O3复合生物涂层.     

Slip casting of Al2O3 and Al2O3/ZrO2 composites

Al₂O₃ and Al₂O₃/ZrO₂ composites have been fabricated by slip casting from aqueous suspensions. The physical and structural characteristics of the starting powders, composition of the suspensions, casting behaviour, microstructure of the green and fired bodies and the mechanical properties of the products were investigated. The addition of ZrO₂ to Al₂O₃ leads to a significant increase in fracture toughness when ZrO₂ particles are retained in the tetragonal form (transformation-toughening mechanism) but when microcracking (due to the spontaneous transformation of ZrO₂ from the tetragonal phase to the monoclinic one) is dominant, an excellent toughness value is accompanied by a drastic drop in strength and hardness.     

Physical properties of slip casting of high pure Al2O3 slurry using porous Al2O3-glass mold

Physical properties of advanced ceramics are influenced by impurities produced in the forming process. The forming compacts produced by slip casting using gypsum molds contain calcium and sulfur in green bodies. Therefore, a porous Al₂O₃-glass mold was produced and slip casting was performed in the present study. Porous Al₂O₃ ceramics as casting molds were examined in comparison with gypsum mold from viewpoints of free energy for wettability and rate of filter cake buildup. The sintered compact of Al₂O₃ produced by slip casting using the porous Al₂O₃-glass mold was compared with those using the gypsum mold. Transmittance of the sintered Al₂O₃ compacts using the porous Al₂O₃-glass molds was increased in comparison with that using the gypsum mold.     

XRCT characterisation of Ti particles inside porous Al2O3

Computed X-ray tomography was used to characterise distribution and sphericity of Ti granules within highly porous (> 35%) Al₂O₃ powder compacts, as they are key parameters for a successful infiltration by Fe-based alloys. Setting of reconstruction constraints, image editing as well as data processing are the most challenging parts of computed X-ray tomography and principal sources of errors that bias the generated data. Thus, corrective measures have to be applied and the reliability of generated data has to be proved with respect to statistical, stereological and volumetric aspects. Combining an adapted Interface Particle Treatment Algorithm with the Marching Cube Method, Equilibrium Random State Model, cluster splitting and conventional laser diffraction measurements a significant improvement of the three-dimensional reconstructed data was achieved. This study points out the need of the applied algorithms for the proof and improvement of generated data by computed X-ray tomography and gives a short survey of methods that can be applied.     

Al2 O3/Al 复合涂层对贫铀的保护性能研究

为探讨Al2O3/Al复合涂层在贫铀表面保护中应用的可行性,采用盐雾腐蚀试验和磨损试验方法,结合SEM/EDS和XRD表征,分析了贫铀表面Al2O3/Al复合涂层的保护性能.结果表明,贫铀表面反应磁控溅射Al2O3/Al涂层没有明显的腐蚀特征,而等离子喷涂Al2O3/Al涂层发生了严重的腐蚀剥落现象.Al2O3/Al涂层表现为磨粒磨损行为,抗磨损性好.作为对比样的贫铀表面Al涂层则表现为粘着磨损行为,抗磨损性差.讨论了贫铀表面涂层的腐蚀和磨损行为.