The Experts below are selected from a list of 258 Experts worldwide ranked by ideXlab platform
Pinggen Rao - One of the best experts on this subject based on the ideXlab platform.
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Improved fracture toughness of CNTs/SiC composites by HF treatment
Journal of Alloys and Compounds, 2018Co-Authors: Chen Pengcheng, Jing Siyi, Yanhui Chu, Pinggen RaoAbstract:Abstract Residual Oxide impurities in high-temperature structural ceramics containing carbon-based reinforcements can react with the reinforcements during sintering to weaken their toughening effect. To eliminate such effect, a simple HF treatment technique is proposed. In this work, SiC ceramics and carbon nanotubes (CNTs)/SiC ceramic composites were fabricated by spark plasma sintering. The results showed that, after HF treatment, the structure of incorporated CNTs in the composites was unaffected and a slight improvement of relative density was fulfilled. The fracture toughness improvement of the composites from 4.4 ± 0.4 MPa m1/2 to 5.4 ± 0.5 MPa m1/2 with indentation method (IM) after HF treatment was also observed due to crack branching, CNT pull-out and crack bridging.
Boong-joo Lee - One of the best experts on this subject based on the ideXlab platform.
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removal of Residual Oxide layer formed during chemical mechanical planarization process for lowering contact resistance
Surface & Coatings Technology, 2012Co-Authors: Sunwoo Lee, Boong-joo LeeAbstract:Abstract In the present work, we report the formation of Residual Oxide layer during chemical–mechanical-planarization (CMP) process in the carbon nanotube (CNT) via interconnects and some feasible solutions for its removal. Residual Oxide layer makes electrically poor contact between CNTs and metal resulting in high contact resistance in CNT via interconnects. We adopt post-CMP processes such as hydrofluoric acid (HF) or Ar plasma treatment to remove the Residual Oxide layer. X-ray photoelectron spectroscopy (XPS) was used to confirm the chemical state of samples before and after the post-CMP process. Silicon and oxygen peaks from silicon-based Oxide layer observed after the CMP process were disappeared and reduced in its intensity by the post-CMP process, respectively. Furthermore, via resistance decreased more than 1 order of magnitude after the post-CMP process. It is found that the post-CMP process provides good electrical contact between CNTs and metal by removing the Residual Oxide layer.
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Removal of Residual Oxide layer formed during chemical–mechanical-planarization process for lowering contact resistance
Surface and Coatings Technology, 2012Co-Authors: Sunwoo Lee, Boong-joo LeeAbstract:Abstract In the present work, we report the formation of Residual Oxide layer during chemical–mechanical-planarization (CMP) process in the carbon nanotube (CNT) via interconnects and some feasible solutions for its removal. Residual Oxide layer makes electrically poor contact between CNTs and metal resulting in high contact resistance in CNT via interconnects. We adopt post-CMP processes such as hydrofluoric acid (HF) or Ar plasma treatment to remove the Residual Oxide layer. X-ray photoelectron spectroscopy (XPS) was used to confirm the chemical state of samples before and after the post-CMP process. Silicon and oxygen peaks from silicon-based Oxide layer observed after the CMP process were disappeared and reduced in its intensity by the post-CMP process, respectively. Furthermore, via resistance decreased more than 1 order of magnitude after the post-CMP process. It is found that the post-CMP process provides good electrical contact between CNTs and metal by removing the Residual Oxide layer.
Ts. Marinova - One of the best experts on this subject based on the ideXlab platform.
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XPS study of Residual Oxide layers on p-GaAs surfaces
Applied Surface Science, 1997Co-Authors: Ts. Mihailova, N. Velchev, V. Krastev, Ts. MarinovaAbstract:Abstract The total thickness and composition of a Residual Oxide layer after chemical etching of p-GaAs:Zn + In has been studied by X-ray photoelectron spectroscopy (XPS). The variation of the Ga to As Oxides ratio along the depth has been determined. A concentration correlation of doping isovalent impurity and the dislocation density with the composition of Residual Oxides is looked for. The total thickness of the Residual Oxide layer on p- and semi-insulating GaAs is about 5–6A. It is found that the Ga2O3 quantity in the Oxide bulk is greater than the same value of As2O3 in highly In-doped samples. In-doping in concentrations over 1.5 × 1019cm−3 increases the Ga2O3 content and the density of the Residual Oxide. This influence is determined by reducing the dislocation density and changing the point defect environment. The presence of As-rich precipitates on the dislocations and in the matrix decreases the sputtering time and changes the composition of the Residual Oxide. The correlation between the type of high temperature dislocations revealed by Abrahams-Buiocchi (AB) etching and the Oxide layer composition is shown. The results obtained could be used in the first stages of epitaxial growth, metallization and other technological processes of semiconductor device and ICs fabrication.
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Investigation of Residual Oxide Layers on GaAs Surfaces
Crystal Research and Technology, 1992Co-Authors: Ts. Marinova, V. Krastev, Rositza YakimovaAbstract:GaAs(100) and (111) oriented samples, treated by means of different chemical procedures, are studied by X-ray photoelectron spectroscopy (XPS). The thickness and composition of the Residual Oxide layers are estimated using the intensity ration of Ga 3d and As 3d core levels from the substrate and the Oxide overlayers, respectively. Residual Oxides containing As2 O3 and Ga2 O3 on GaAs surface are observed. The thickness of the Oxide layers is found to range from 3A to 15 A. Optimal conditions for pre-epitaxial surface preparation of GaAs substrates are suggested. [Russian Text Ignored.]
Hongyou Chen - One of the best experts on this subject based on the ideXlab platform.
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Microstructure and Properties of Joint Interface of Semisolid Stirring Brazing of Composites
Journal of Materials Science & Technology, 2012Co-Authors: Bofang Zhou, Du Changhua, Quanxiang Luo, Hongyou ChenAbstract:Stirring assisted brazing of SiCp/A356 composites in air was investigated. A stirring was applied on one of the samples to be bonded at 455 °C during brazing. The filler metal was extruded and impacted intensively on the two surfaces of the base materials during stirring. It can be found that Oxide film on the surface of the composites can be disrupted and removed through the observation by scanning electron microscopy (SEM). The metallurgical bonds formed between the filler metal and the base materials. However, continuous Residual Oxide film was found at bottom joint interface, which limited the lift of joint strength. A stirring was applied once more after the samples were continuously heated up to 470 and 500 °C, respectively. At this time, Residual Oxide film after the first of stirring can be broken by once more stirring. The bonds are mainly composed of a new alloy, which have a higher content of aluminum and are free of continuous Oxide film, showing higher shear strength of 113 MPa than that of the base materials.
Kazuya Yamamura - One of the best experts on this subject based on the ideXlab platform.
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Obtaining Atomically Smooth 4H–SiC (0001) Surface by Controlling Balance Between Anodizing and Polishing in Electrochemical Mechanical Polishing
Nanomanufacturing and Metrology, 2019Co-Authors: Xu Yang, Rongyan Sun, Kentaro Kawai, Kenta Arima, Xiaozhe Yang, Kazuya YamamuraAbstract:Single-crystal 4H–SiC is a promising next-generation semiconductor material for high-power and low-loss power devices. Electrochemical mechanical polishing (ECMP) is a very promising polishing technique for the manufacture of SiC wafers owing to its high efficiency and low cost. In this study, the effects of the balance between the anodic oxidation rate and the polishing rate of the Oxide layer on the polishing performance of slurryless ECMP were studied in an attempt to obtain an atomically smooth surface efficiently. The polishing performance of ECMP was evaluated from the viewpoints of surface roughness, Residual Oxide, and material removal rate. It was found that the balance between the anodic oxidation rate and the polishing rate of the Oxide layer strongly affects the surface roughness; the polishing rate of the Oxide layer should be greater than the anodic oxidation rate to obtain an atomically smooth surface. By controlling this balance at a current density of 10 mA/cm2, we were able to decrease the surface roughness of a diamond-lapped 4H–SiC (0001) surface from Sq 4.290 to 0.577 nm and obtained a high material removal rate of about 10 μm/h. This study provides a promising way of obtaining atomically flat surfaces by slurryless ECMP.
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Highly efficient planarization of sliced 4H–SiC (0001) wafer by slurryless electrochemical mechanical polishing
International Journal of Machine Tools and Manufacture, 2019Co-Authors: Xu Yang, Kenta Arima, Kentaro Kawai, Xiaozhe Yang, Kazuya YamamuraAbstract:Abstract Slurryless electrochemical mechanical polishing (ECMP) was proposed and directly applied to sliced 4H–SiC (0001) surfaces. After ECMP for 2 h at a current density of 10 mA/cm2 in sodium chloride aqueous solution using a #8000 ceria vitrified grinding stone, a scratch-free mirror surface was obtained, and the Sq roughness of the SiC surface decreased from 286 to 1.352 nm. The material removal rate was about 23 μm/h, and the saw marks and surface damage on the sliced surface were completely removed. Raman spectroscopy and X-ray photoelectron spectroscopy showed no subsurface damage or Residual Oxide on the ECMP-processed surface, and the quality of the surface was much higher than that obtained by conventional lapping. The results of this study suggest that the manufacturing process for SiC can be simplified by applying slurryless ECMP with a high material removal rate and low cost.
