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1
Li, Zhang, Xue Yu-Ming, Xu Chuan-Ming, He Qing, Liu Fang Fang, Li Chang-Jian, and Sun Yun. "Microstructural characterization of Cu-poor Cu (In, Ga)Se2 surface layer." Thin Solid Films 520, no. 7 (January 2012): 2873–77. http://dx.doi.org/10.1016/j.tsf.2011.11.077.
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Nishimura, Takahito, Yoshiaki Hirai, Yasuyoshi Kurokawa, and Akira Yamada. "Theoretical and experimental investigation of the recombination reduction at surface and grain boundaries in Cu(In,Ga)Se2 solar cells by valence band control." MRS Proceedings 1771 (2015): 125–31. http://dx.doi.org/10.1557/opl.2015.387.
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ABSTRACTWe carried out theoretical calculation for Cu(In,Ga)Se2 (CIGS) solar cells with energy bandgap of 1.4 eV assuming formation of a Cu-poor layer on the surface of CIGS films. This calculation result revealed that formation of a thinner Cu-poor layer such as a few nanometers leads to improvement of the solar cells performance. This is because interfacial recombination was suppressed due to repelling holes from the interface by valence band offset (ΔEV). Next, we investigated composition distribution in the cross section of CIGS solar cells with Ga contents of 30% and 70% by transmission electron microscopy (TEM) and energy dispersive X-ray analysis (EDX). It was revealed that the Cu-poor layer was formed on the surface and at the grain boundary (GB) in the case of conversion efficiency (η) of 17.3%, although it was not formed in the case of lower η of 13.8% for a Ga content of 30%. These results indicate that formation of the Cu-poor layer contributed to improvement of cell performance by suppression of carrier recombination. Moreover, it was also confirmed that although the Cu-poor layer was observed on the surface, it was not observed at the GB in the case of CIGS solar cells with a Ga content of 70% which had η of 12.7%. It is thought that the effect of repelling holes by ΔEV is not obtained at the GB and the solar cell performance in the Ga content of 70% is lower than that in the Ga content of 30%. Thus, we suggest importance of the Cu-poor layer at the GB for high efficiency of CIGS solar cells with high Ga contents.
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Zhang, Man, Yue Bin Lin, Jian Qiang Lv, and Hai Lin Jiang. "Effect of Al on Zn-Al Filler Metal Wettability on Pure Copper Surface." Advanced Materials Research 538-541 (June 2012): 196–99. http://dx.doi.org/10.4028/www.scientific.net/amr.538-541.196.
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Zn-Al filler metal wettability tests were performed. With the match of CsF-AlF3 flux, Zn-Al filler metal wettability is poor on pure copper surface. The Cu-Al-Zn intermetallic compound interface layer exits between Zn-Al filler metal and Cu base metal. When Al content is low in Zn-Al filler metal, the filler metal wettability is poor and the filler metal melting point is low. In the wettability test course, the time is long in which Cu base metal interacts with liquid Zn-Al filler metal. And the Cu-Al-Zn intermetallic compound interface layer grows thick between filler metal and base metal. With the increase of Al content in Zn-Al filler metal, the interaction strengthens between Zn-Al filler metal and Cu base metal. In the wettability test course, the time beocome short in which Cu base metal interacts with liquid Zn-Al filler metal. The Cu-Al-Zn intermetallic compound interface layer gets thin between filler metal and base metal. Meanwhile, Zn-Al filler metal wettability improves on pure copper surface. But the improvement is not remarkable. Its wettablility is still poor on pure copper surface.
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Sung, Po-Hsien, and Tei-Chen Chen. "Performance of Cu–Ag Thin Films as Diffusion Barrier Layer." Coatings 10, no. 11 (November 13, 2020): 1087. http://dx.doi.org/10.3390/coatings10111087.
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It is well-known that Cu–Sn intermetallic compounds are easily produced during reflow process and result in poor reliability of solder bump. Recently, amorphous metallic films have been considered to be the most effective barrier layer because of the absence of grain boundaries and immiscibility with copper. Since Cu–Ag alloys are characterized by their lower electrical resistivity and superior glass-forming ability, they are appropriate to be used as the diffusion barrier layers. In this study, molecular dynamics simulation was performed to investigate the effects of composition ratio and quenching rate on the internal microstructure, diffusion properties, and the strength of the interface between polycrystalline Cu and Cu–Ag barrier layers. The results showed that Cu40Ag60 and Cu60Ag40 present more than 95% of the amorphous at quenching rate between 0.25 and 25 K/ps, indicating a good glass-forming ability. Diffusion simulation showed that a better barrier performance can be achieved with higher amorphous ratio. For the sample of Cu20Ag80 with quenching rate of 25 K/ps, a void is initially generated in amorphous Cu–Ag layer during the tensile test. This indicates the strength of amorphous Cu–Ag is weaker than Cu–Ag/Cu interface and the polycrystalline Cu layer.
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Terajima, Takeshi. "Development of Cu-Clad Metallic Glass for Soldering." Materials Science Forum 706-709 (January 2012): 1343–47. http://dx.doi.org/10.4028/www.scientific.net/msf.706-709.1343.
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Soldering is a potential technique for joining metallic glasses. It can be performed at far below the crystallization temperature of various metallic glasses; thus, there is no possibility of crystallization. However, Cu-Zr-based metallic glass displays poor wettability to Pb-free solder, because a strong native oxide film prevents direct contact between the solder and the glass. To overcome this problem, Cu-Zr-based metallic glass clad with a thin film of Cu has been developed. This was produced by casting the melt of a Cu36Zr48Al8Ag8 pre-alloy into a Cu mold cavity, inside which a thin film of Cu with a thickness of 2 μm was placed. Cu36Zr48Al8Ag8 metallic glass was successfully formed and welded to the Cu thin film. From microstructure analysis, it was found that a reaction layer was formed at the interface between the Cu and the Cu36Zr48Al8Ag8 metallic glass. However, no oxide layer was observed in the Cu-clad layer. It was found that the Cu cladding played an important role in preventing the formation of the surface oxide film. Consequently, solderability to the Cu-Zr-based metallic glass was drastically improved.
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Jiang, N., and J. Silcox. "On The Formation Of Diffusion Layer Between Cr Film And Glass." Microscopy and Microanalysis 5, S2 (August 1999): 166–67. http://dx.doi.org/10.1017/s143192760001415x.
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Chromium films are commonly used as a metal “glue” layer because of good adhesion to glass. It is believed that an intermediate oxide layer is formed during deposition, since Cr has a very strong affinity for oxygen. For example, a graded Cu/Cr/CrOx/SiO2 structure ensures excellent adhesion of Cu to glass, whereas Cu exhibits poor adhesion to most dielectrics. In our recent study, however, a diffusion layer, Cr2O3+SiOy, was observed between CrOx and SiO2 (glass) substrate. It is quite likely that this diffusion layer is responsible for the good adhesion of Cr film to glass.The relative compositions of the major components across the interface are shown in Fig 1. A Cr film was evaporated on Corning Code 1737 glass (Al2O3-B2O3-SiO2 with ˜67at.% Si02) substrate at room temperature (RT) and subsequently covered with about lOnm Cu. A 5nm'wide diffusion layer is seen. The corresponding regions are also indicated in Fig 2, an Annular Dark Field (ADF) image whose contrast is approximately proportional to the density if the thickness is assumed uniform.
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TING, WU, T. EGI, R. ITTI, K. KURODA, N. KOSHIZUKA, and S. TANAKA. "IDENTIFICATION OF THE NATURAL TERMINATION LAYER ON THE SURFACES OF As-PREPARED Nd1Ba2Cu3Oy SINGLE CRYSTALS AND SURFACE DEFECT STRUCTURES." Modern Physics Letters B 09, no. 20 (August 30, 1995): 1297–301. http://dx.doi.org/10.1142/s0217984995001273.
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The natural termination layer has been identified to be the CuO chain layer on the surfaces of as-prepared high quality Nd 1 Ba 2 Cu 3 O 7−y (Nd123) single crystals, employing an ultrahigh vacuum scanning tunneling microscope (UHV-STM) system. It is found that the oxygen atoms of the CuO chain layer are unstable in the environment of UHV (~10−8 Pa). Oxygen loss occurs in some areas of the surfaces of Nd123 single crystals, leading to some localized surface defect structures. Such defect structures may be responsible for the poor reproducibility of the superconducting gap structure observed on the surface of Y 1 Ba 2 Cu 3 O y from low temperature tunneling measurements.
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Liu, Chung Ping, Ming Wei Chang, Chuan Lung Chuang, and Nien Po Chen. "Synthesis of Cu-Poor Copper-Indium-Gallium-Diselenide Nanoparticles by Solvothermal Route for Solar Cell Applications." International Journal of Photoenergy 2014 (2014): 1–6. http://dx.doi.org/10.1155/2014/976030.
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Copper-indium-gallium-diselenide (CIGS) thin films were fabricated using precursor nanoparticle ink and sintering technology. The precursor was a Cu-poor quaternary compound with constituent ratios ofCu/(In+Ga)=0.603,Ga/(In+Ga)=0.674, andSe/(Cu+In+Ga)=1.036. Cu-poor CIGS nanoparticles of chalcopyrite for solar cells were successfully synthesized using a relatively simple and convenient elemental solvothermal route. After a fixed reaction time of 36 h at 180°C, CIGS nanocrystals with diameters in the range of 20–70 nm were observed. The nanoparticle ink was fabricated by mixing CIGS nanoparticles, a solvent, and an organic polymer. Analytical results reveal that the Cu-poor CIGS absorption layer prepared from a nanoparticle-ink polymer by sintering has a chalcopyrite structure and a favorable composition. For this kind of sample, its mole ratio of Cu : In : Ga : Se is equal to 0.617 : 0.410 : 0.510 : 2.464 and related ratios ofGa/(In+Ga)andCu/(In+Ga)are 0.554 and 0.671, respectively. Under the condition of standard air mass 1.5 global illumination, the conversion efficiency of the solar cell fabricated by this kind of sample is 4.05%.
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Ghanta, Sivaprasad, Nilanjan Roy, and Partha Pratim Jana. "Crystal structures of two very similar 2 × 2 × 2 superstructures of γ-brass-related phases in ternary Ir–Cd–Cu system." Acta Crystallographica Section B Structural Science, Crystal Engineering and Materials 76, no. 1 (January 15, 2020): 47–55. http://dx.doi.org/10.1107/s2052520619015488.
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A binary phase Ir8Cd41 in the Ir–Cd binary system and novel ternary phases in the Ir–Cd–Cu system have been synthesized from the constituent elements using high-temperature solid-state synthesis. The structure of previously reported Ir8Cd41 and newly found ternary phases in the Ir–Cd–Cu system have been characterized by single crystal X-ray diffraction and EDS analysis. The structural analysis reveals that Ir8Cd41 adopts V8Ga41-type structure and ternary Ir–Cd–Cu phases adopt two 2 × 2 × 2-superstructures of the γ-brass-related phase. The structures of ternary Ir–Cd–Cu phases are associated with structural disorder (vacancies as well as mixed site occupancies). The crystal structures of the ternary phases are viewed using layer description and cluster concept. The 2 × 2 × 2-superstructure of γ-brass-related phases in the Cu-poor region are not isostructural with the phases in the Cu-rich region, and they are consistent with the absence of a continuous phase region between two 2 × 2 × 2-superstructures of γ-brass-related phases. In the Cu-poor region, the structures contain ∼404 atoms per unit cell, whereas in the Cu-rich phases the structures contain ∼411 atoms in their respective unit cells. The crystal structures in the Cu-poor region represent a new type in the 2 × 2 × 2-superstructure of γ-brass-related phases in view of the combination of constituent cluster types, whereas the structures in the Cu-rich region adopt the Rh7Mg44 structure type.
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Liu, Chih-Yi, Chao-Cheng Lin, Chun-Hung Lai, Shih-Kun Liu, Chang-Sin Ye, Wei-Chen Tien, and Meng-Ren Hsu. "Characteristics of GZO-based multilayer transparent conducting films." International Journal of Modern Physics B 35, no. 14n16 (June 30, 2021): 2140004. http://dx.doi.org/10.1142/s021797922140004x.
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Ga-doped ZnO (GZO)/metal/GZO structures were fabricated on glass substrates to be the transparent conducting layers in this study. GZO films and metal films were deposited at room-temperature by a radio-frequency sputter and a thermal evaporator, respectively. The GZO/Ag/GZO (GAG) structures had poor electrical and optical properties due to the formation of Ag islands on the GZO layer. A 1-nm Cu seed layer was deposited on the GZO layer to fabricate the GZO/Ag/Cu/GZO (GACG) structure to improve its electrical and optical properties. The GACG structure had sheet resistance of 9 [Formula: see text], average visible transmittance of 86% and figure of merit of [Formula: see text] [Formula: see text]. In addition, the sheet resistance of the GACG structure kept almost the same after annealing at [Formula: see text]C in atmosphere for more than 5 h, which showed good thermal stability.
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Yu, Ho-Chieh (Jay), and Jason Huang. "Investigation of the Direct Plating Copper (DPC) on Al2O3, BeO or AlN Ceramic Substrates for High Power Density Applications." International Symposium on Microelectronics 2016, no. 1 (October 1, 2016): 000079–86. http://dx.doi.org/10.4071/isom-2016-tp43.
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Abstract In the high power module applications, the power increasing and the size shrinking becomes one of the major topics for the power module design. Due to both the power increasing and the size decreasing, the power density of the device will be much increased. Therefore, not only the thermal conductivity and stability of the substrate material but the long-term material reliability of the substrate have to be seriously considered. For these reasons, the ceramic PCB becomes one of the best solutions. The ceramic substrates now used are normally based on Ag-printed or direct bonding copper (DBC) technology. In the case of the Ag-printed ceramic substrate, the pattern resolution and metallization thickness are limited by the Ag-printed process. Also the combination strength of the silver and ceramic substrate by glass (which is normally mixed in the silver paste) is normally not good enough. A thermal dissipation barrier will then be formed between silver and ceramic substrate due to the poor thermal conductivity of the glass material. For the DBC ceramic substrate, DBC substrates are manufactured at 1065°C by the diffusion between ceramic and Cu/CuO layer. A thicker Cu layer thickness of normally more than 300 um is required in the thermal compressing bonding process. The Cu pattern resolution will then be limited by the thickness of the Cu layer. However, the about 5~10% of the voids exist randomly between ceramic and Cu layer is the other major issue. The resolution issues of the Ag-printed and DBC ceramic substrates make the limitation for the device density design (fine line/width and flip-chip device design become very difficult). The glass material in the Ag printed ceramic substrate and the 5~10% voids existence in DBC ceramic substrate may cause the reliability issue operating at a high power density applications. For high power density module applications, we introduce the DPC technology on the ceramic substrate. In DPC ceramic substrate system, the sputtered Ti is used as the combination material between Cu and ceramic substrate. And the first copper is then sputtered on the top of Ti layer as seed-layer for the following Cu electrode plating (second cupper layer). By the material and the sputtering process control, several ceramic substrate raw materials can be used, such as Al2O3, AlN, BeO, Si3N4 and so on. The Ti combined/buffer layer provides good adhesion strength and material stability. The second copper layer is plated by electrode casting plating to 3 to 5 oz. (100~150um) in thickness. The key technology of the metal trace plating is the material control of the sputter layers and the second copper layer stress release during plating. In the DPC system, the double layers design is available. The laser drilled via holes on the various ceramic substrates is introduced. The conducting of the front and back side is connected by the following plating process. The key technology of this process is the stability of the via-holes. We have to make sure the via-holes cleaning, impurity removing and material stability during high temperature laser drilled is well controlled. DPC ceramic substrates provide a better metal/ceramic interface uniformity and material reliability due to the stable Ti combination material and much less voids in the metal/ceramic interface. Also, the DPC ceramic substrates provide a gold pattern resolution of 50 um line space with tight tolerance of 20 um min. We believe the material characteristic make DPC a very suitable substrate material for high power module applications.
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Rucki, A., and C. Lee. "A Copper Leadframe Oxidation Investigation by Electron Energy-Loss Spectroscopy." Microscopy and Microanalysis 6, S2 (August 2000): 1100–1101. http://dx.doi.org/10.1017/s1431927600037995.
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Copper alloys are widely used as a leadframe (chip carrier) material in plastic packaged semiconductor devices. The oxidation of Cu leadframes during the assembly process can result in poor adhesion between the moulding compound and the die-pad. This often leads to interfacial delamination and contributes to popcorn cracking during the component-board attachment process. The main cause of poor adhesion has been attributed to the weak Cu oxide(s) layer on the leadframe surface. Studies have shown that the moulding compound/leadframe adhesion decreases with increasing oxide thickness.The aim of this investigation is to give a detailed analysis of the phase formation of a CuNiSi alloy during oxidation and to identify the locus of failure for the interfacial delamination. The Cu leadframes were oxidized in an air oven at 240° C for up to 200 min exposures before encapsulation. A scanning acoustic microscope was used to locate delamination regions along the moulding compound/leadframe interface.
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Suganuma, Katsuaki, Koichi Niihara, Takeshi Shoutoku, and Yoshikazu Nakamura. "Wetting and interface microstructure between Sn–Zn binary alloys and Cu." Journal of Materials Research 13, no. 10 (October 1998): 2859–65. http://dx.doi.org/10.1557/jmr.1998.0391.
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Sn–Zn binary alloys have been examined as a lead-free solder. Zn distributes in a Sn matrix as platelets. The hypoeutectic alloys show two endothermic peaks in DTA, which correspond to the eutectic and the liquidus temperatures. Three reaction layers are formed at the Sn–Zn/Cu interface without containing Sn: the thick γ–Cu5Zn8 adjacent to the solder, the thin β′–CuZn in the middle, and the thinnest layer adjacent to Cu. Although many nonwetting regions and voids are formed at the interface because of poor wetting, soldering at 290 °C can form a rigid interface, and tensile strength reaches about 40 MPa.
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Ren, Keming, and Abasifreke Ebong. "Investigation of the Screen-printable Ag/Cu Contact for Si Solar Cells Using Microstructural, Optical and Electrical Analyses." MRS Advances 5, no. 8-9 (November 22, 2019): 431–39. http://dx.doi.org/10.1557/adv.2019.438.
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ABSTRACTIn a bid to further reduce the cost of the front Ag contact metallization in Si solar cells, Cu is the potential alternative to replace the Ag in the Ag paste. However, this requires an understanding of the contact mechanism of screen-printable Ag/Cu paste in Si solar cell through rapid thermal process. The pastes with different weight percent of Cu (0 wt%, 25 wt% and 50 wt%) were used and the Voc of the cells was reduced with the increasing weight percent of Cu. This is because the presence of Cu in the paste changed the microstructure of the Ag/Cu/Si contact through Cu doping of the glass frits and hence increasing the Tg of the glass. The increased Tg of the glass impeded the uniform spreading of the molten glass and resulted in poor wetting and etching of the SiNx, which impacted the contact as evident in ideality factor of less than unity. This also led to the formation of agglomerated Ag crystallites with features of 700 nm in length and 200 nm in depth, which is close to the p-n junction, of which depth is ∼300 nm. However, the interface glass layer acted as an effective diffusion barrier layer to prevent Cu atoms from diffusing into the Si emitter, which is quite remarkable for Cu not to diffuse into silicon at high temperature. Further investigation of the Ag/Cu contacts with the conductive AFM in conjunction with the SEM and STEM analyses revealed that the growth of Ag crystallites in the Si emitter is responsible for carrier conduction the gridlines as with the pure Ag paste.
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Lee, Alvin, Jay Su, Baron Huang, Ram Trichur, Dongshun Bai, Xiao Liu, Wen-Wei Shen, et al. "Optimization of laser release layer, glass carrier, and organic build-up layer to enable RDL-first fan-out wafer-level packaging." International Symposium on Microelectronics 2016, no. 1 (October 1, 2016): 000190–95. http://dx.doi.org/10.4071/isom-2016-wa34.
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Abstract With increasing demand for mobile devices to be lighter and thinner and consume less power while operating at high speed and high bandwidth, many equipment suppliers and assembly participants have invested great efforts to achieve fine-line fan-out wafer-level packaging (FOWLP). However, the inherent warp of reconstituted wafers, which can contribute to poor die placement accuracy and/or delamination at the interface of the build-up layer and carrier, remains a major challenge. In this study, the interactions among laser release layer, glass carrier, and build-up layer were evaluated for optimization of redistribution layer (RDL)–first FOWLP as a foundation to move toward fine-line FOWLP. In this study, a series of experiments incorporating glass carrier, laser release layer, and build-up layers were carried out to determine the optimal setup for RDL-first FOWLP. First, glass carriers (300 mm × 300 mm × 0.7 mm) with coefficients of thermal expansion of 3 and 8 ppm/°C were treated with 150-nm laser release layers. After deposition of 0.1 μm of sacrificial material on the glass carrier, 8-μm build-up layers were coated and patterned by lithography to electroplate Cu interconnections with a density of approximately 10% of the surface area. Subsequent to die attachment, molding compound was applied on top to form a 200-μm protective overcoat. The reconstituted wafer was then separated from the glass carrier through a laser ablation process using a 308-nm laser to complete the design of experiments (DOE). An experiment to study the correlation of glass carrier, laser release layer, build-up layers, and molding compound in RDL-first FOWLP processes is discussed to address full process integration on 300-mm glass substrates. The combination of glass carrier, laser release layer, build-up layer, and molding compound will pave the way for realizing cost-effective RDL-first FOWLP on panel-size substrates.
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Zhuk, Siarhei, Terence Kin Shun Wong, Elizaveta Tyukalova, Asim Guchhait, Debbie Hwee Leng Seng, Sudhiranjan Tripathy, Ten It Wong, et al. "Effect of TaN intermediate layer on the back contact reaction of sputter-deposited Cu poor Cu2ZnSnS4 and Mo." Applied Surface Science 471 (March 2019): 277–88. http://dx.doi.org/10.1016/j.apsusc.2018.11.227.
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Yap, Boon Kar, Cai Hui Tan, and Chou Yong Tan. "Solder Ball Robustness Comparison between SAC 387 and Polymer Solder Balls under AC and TC Reliability Test." Applied Mechanics and Materials 789-790 (September 2015): 61–65. http://dx.doi.org/10.4028/www.scientific.net/amm.789-790.61.
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Environment and the health concerns due to the hazardous effects of lead resulted in significant activities to find a replacement for lead-contained solders for electronics industrial. Majority of the semiconductor industrial are now replacing lead solders with Tin-Silver-Copper (SAC 387) solder balls. However, dropped balls in SAC 387 for Ball Grid Array (BGA) products due to poor solder joint strength caused by high thermal stress are a major concern in the semiconductor industries. Polymer core inside the solder ball (polymer core/Cu/Sn) is thus integrated to improve the solder ball joint strength. The function of polymer core inside the solder ball is to absorb and released the stress better as compared to the SAC 387 solder ball. Since the diffusion rate of Cu is faster than the diffusion rate of Sn, hence, this could caused the Kirkendall voids tends to form in between the Cu and Sn IMC layer. This would affect the solder ball joint strength and causing drop balls issue. By implement with an extra of Ni layer to the polymer core solder ball (core/Cu/Ni/Sn), could reduce the diffusion from Cu to Sn, thus to overcome the Kirkendall voids and to further improve the solder ball joint strength. This research work studies the performance of the solder ball shear strength of the two types of solder balls applied to MAPBGA device. In this research, both SAC 387 and polymer solder balls were went through under AC (Autoclave) and TC (Temperature Cycle) reliability test up to 144 hours and 1000 cycles, respectively. Solder ball shear strength test was conducted via Dage 4000 series bond tester. From the research work results of the two types of solder balls, the ball shear strength were decreased with an increased of aging and cycles. Overall, it can be concluded that the polymer core solder ball with an additional of Ni layer showed better performance than the polymer core without Ni layer and SAC 387 solder balls, after subjected to the AC and TC reliability test.
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Wang, Nan, Yong-Nan Chen, Long Zhang, Yao Li, Shuang-Shuang Liu, Hai-Fei Zhan, Li-Xia Zhu, Shi-Dong Zhu, and Yong-Qing Zhao. "Isothermal Diffusion Behavior and Surface Performance of Cu/Ni Coating on TC4 Alloy." Materials 12, no. 23 (November 24, 2019): 3884. http://dx.doi.org/10.3390/ma12233884.
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The poor surface performance of titanium alloys substantially limits their application in many fields, such as the petrochemical industry. To overcome this weakness, the Cu and Ni double layers were deposited on the surface of TC4 alloy by the electroplating method, and the isothermal diffusion process was performed at 700 °C to enhance the binding ability between Cu and Ni layers. The isothermal diffusion behavior and microstructure of the coating were systematically analyzed, and tribological property and corrosion resistance of the coating were also evaluated to reveal the influence of isothermal diffusion on the surface performance. It was shown that multiple diffusion layers appeared on the Cu/Ni and Ni/Ti interface, and that NixTiy and CuxTiy phases were formed in the coating with the increase of diffusion time. More importantly, Kirkendall diffusion occurred when the diffusion time increased, which led to the formation of continuous microvoids and cracks in the diffusion layer, weakening the surface performance of the Cu/Ni coatings. This paper unveils the relationship between the microstructure of the Cu/Ni coatings and isothermal diffusion behavior, providing guidelines in preparing high performance surface coatings.
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Ma, Tao, Huirong Li, Jianxin Gao, and Yungang Li. "Corrosion Behaviour of Cu/Carbon Steel Gradient Material." Crystals 11, no. 9 (September 7, 2021): 1091. http://dx.doi.org/10.3390/cryst11091091.
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Research on improving the corrosion resistance of carbon steel has become a hot topic in the iron and steel field in recent years. Copper plating on the surface of carbon steel is considered an effective means to improve its corrosion resistance, but the copper-plated carbon steel material prepared by this method has the problems of poor abrasion resistance, easy delamination of copper layer and similar issues, which affect the service performance of the copper-plated carbon steel material. To solve this problem, a new type of material whose surface is copper and the copper element is gradually diffused into carbon steel was developed by a plating-diffusion method, which is defined as a copper-carbon steel gradient material. Carbon steel with a copper plated surface and the Cu-Fe/carbon steel gradient material with 80% Cu content on the surface were prepared by the same method. The cross-sectional microstructure and composition of different samples were analysed, and the corrosion behaviors of samples in 3.5% NaCl solution were studied by the linear polarization curve method and electrochemical impedance spectroscopy. The cross-sectional microstructure result shows that the diffusion of copper in carbon is mainly carried out along its grain boundary, and the diffusion of copper will inhibit the growth of grains during heat treatment. As shown in the results of corrosion behaviors, there is no pitting corrosion in the corrosion process of all samples, as well as the stable passive film. All samples showed active dissolution. Compared with carbon steel, the corrosion potential of the Cu/carbon steel gradient material becomes more positive from −600 mV to −362 mV, the corrosion current density decreases from 53.0 μA/cm2 to 30.6 μA/cm2 and the radius of electrochemical impedance spectroscopy enlarges while the corrosion resistance is improved, and the corrosion resistance is mainly obtained by its surface copper layer. The corrosion resistance of Cu-Fe/carbon steel gradient material is lower than that of Cu/carbon steel gradient material, while it is still better than carbon steel, and it shows a clear passivation trend during corrosion. Therefore, the copper/carbon steel gradient material can significantly improve the corrosion resistance of carbon steel. Even after the surface copper layer is destroyed, the gradient material can protect the matrix and improve the service life of the material.
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Chen, Rongrong, Jiandong Fan, Hongliang Li, Chong Liu, and Yaohua Mai. "Efficiency enhancement of Cu 2 ZnSnS 4 solar cells via surface treatment engineering." Royal Society Open Science 5, no. 1 (January 2018): 171163. http://dx.doi.org/10.1098/rsos.171163.
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Pure-sulphide Cu 2 ZnSnS 4 (CZTS) thin film solar cells were prepared by a low-cost, non-toxic and high-throughput method based on the thermal decomposition and reaction of sol–gel precursor solution, followed by a high temperature sulfurization process in sulphur atmosphere, which usually gave rise to the unexpected Cu-poor and Zn-rich phase after sulfurization. In order to remove the formation of detrimental secondary phases, e.g. ZnS, a novel method with hydrochloric acid solution treatment to the CZTS absorber layer surface was employed. By using this method, a competitive power conversion efficiency as high as 4.73% was obtained, which is a factor of 4.8 of that of the control CZTS solar cell without surface treatment. This presents a customized process for CZTS photovoltaic technologies that is more environmentally friendly and considerably less toxic than the widely used KCN etching approach.
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Li, Gang, Shengyu Xu, Xiaofeng Lu, Xiaolei Zhu, Yupeng Guo, and Jufeng Song. "Effect of welding speed on microstructure and mechanical properties of titanium alloy/stainless steel lap joints during cold metal transfer method." Metallurgical Research & Technology 117, no. 5 (2020): 506. http://dx.doi.org/10.1051/metal/2020052.
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Cold metal transfer (CMT) technique is developed for lap joining of titanium (Ti) alloy to stainless steel (SS) with CuSi3 filler wire. The effect of welding speed on the microstructure and mechanical properties of Ti/SS lap joints is investigated. The results indicate that the wetting angle of the lap joints gradually increases and the weld width decreases with increasing the welding speed. It is found that many coarse phases in the fusion zone are rich in Ti, Fe and Si etc, inferring as Fe–Si–Ti ternary phase and/or Fe2Ti phase at low welding speed. Many fine spherical particles in the fusion zone are considered as iron-rich particles at high welding speed. The transition layer are exhibited at the Ti–Cu interface. With increasing the heat input, the intermetallic layer becomes thicker. A variety of brittle intermetallic compounds (IMCs) are identified in the lap joints. The shear strength of the joints increases with increasing the welding speed. Two fracture modes occur in the lap joints at low welding speed. Thicker reaction layer causes brittle fracture and poor joint strength. The Fe–Ti–Si and Fe2Ti phase within the fusion zone are detrimental to the joint strength. The fracture surface of the joints is dominated by smooth surface and tear pattern at high welding speed. The fracture mode of the joints is merely along the Ti–Cu interface.
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Singh, Inderjit, Shin Low, Syu Fu Song, Chen Shih Jung, Lin Ming San, Ivy Qin, Cuong Huynh, et al. "Pd-coated Cu Wire Bonding Reliability Requirement for Device Design, Process Optimization and Testing." International Symposium on Microelectronics 2012, no. 1 (January 1, 2012): 000396–404. http://dx.doi.org/10.4071/isom-2012-tp42.
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One of the biggest technology drivers in the semiconductor industry today is the fast transition from Au wire bonding to Cu wire bonding. The fast adaptation of Cu and Pd-coated Cu (PCC) wire has focused the whole packaging industry to develop understanding, equipment and processes that can produce a more reliable and robust Cu wire bonding technology. Although the fundamentals of wire bonding technology are very similar between Au and Cu wire bonding, there are a lot of new challenges in Cu wire bonding. Compared to Au wire bonding, Cu wire bonding needs different bond quality measures and metrology. Traditional ball diameter, ball height and shear measurements are not adequate to quantify a Cu wire bonding process. Some of the additional bond quality measures include pad material push out (pad splash), Al layer peel off (pad peel) and crack in the barrier and dielectric layer (pad crack). Another area that is quite different between Au and Cu is the reliability test requirement. In Au wire bonding, because of the fast intermetallic compound (IMC) growth rate, the HTS test is normally the hardest to pass. Due to the corrosion of Cu wire, the HAST test is the most challenging in Cu wire bonding. Reliability requirements still need more knowledge. In this paper, we conduct reliability tests for devices with 3 sets of wire bonding parameters. The bonded samples have IMC coverage between 94% and 97%, well above the industry level of 80%. The reliability (HAST) test passed for all samples at 96 hours. However, there are some failures in the HAST test at 192 hr. There are many factors that can influence reliability outcome including wire bonding and non-wire bonding related factors. The failure analysis identified two potential causes in our case. In one failure case, an abnormally high Chlorine level and void in molding compound were detected next to the failed bond while no Chlorine and void were detected elsewhere. In the 2nd failure case, the bonded ball seems to be off centered and results in poor bonded ball to pad interface. These two factors will be more tightly controlled in future tests to verify the reliability outcome. Intermetallic growth and phase transformation, aluminum oxide, and behavior of palladium in PdCu wire bonds are analyzed using transmission electron microscopy (TEM) of dual beam focused ion beam (FIB) thinned specimens. Results are compared to wire bonding measurement and reliability outcome.
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Ossig, Christina, Christian Strelow, Jan Flügge, Andreas Kolditz, Jan Siebels, Jan Garrevoet, Kathryn Spiers, et al. "Four-Fold Multi-Modal X-ray Microscopy Measurements of a Cu(In,Ga)Se2 Solar Cell." Materials 14, no. 1 (January 5, 2021): 228. http://dx.doi.org/10.3390/ma14010228.
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Inhomogeneities and defects often limit the overall performance of thin-film solar cells. Therefore, sophisticated microscopy approaches are sought to characterize performance and defects at the nanoscale. Here, we demonstrate, for the first time, the simultaneous assessment of composition, structure, and performance in four-fold multi-modality. Using scanning X-ray microscopy of a Cu(In,Ga)Se2 (CIGS) solar cell, we measured the elemental distribution of the key absorber elements, the electrical and optical response, and the phase shift of the coherent X-rays with nanoscale resolution. We found structural features in the absorber layer—interpreted as voids—that correlate with poor electrical performance and point towards defects that limit the overall solar cell efficiency.
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Cheng, Weiren, Huabin Zhang, Deyan Luan, and Xiong Wen (David) Lou. "Exposing unsaturated Cu1-O2 sites in nanoscale Cu-MOF for efficient electrocatalytic hydrogen evolution." Science Advances 7, no. 18 (April 2021): eabg2580. http://dx.doi.org/10.1126/sciadv.abg2580.
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Conductive metal-organic framework (MOF) materials have been recently considered as effective electrocatalysts. However, they usually suffer from two major drawbacks, poor electrochemical stability and low electrocatalytic activity in bulk form. Here, we have developed a rational strategy to fabricate a promising electrocatalyst composed of a nanoscale conductive copper-based MOF (Cu-MOF) layer fully supported over synergetic iron hydr(oxy)oxide [Fe(OH)x] nanoboxes. Owing to the highly exposed active centers, enhanced charge transfer, and robust hollow nanostructure, the obtained Fe(OH)x@Cu-MOF nanoboxes exhibit superior activity and stability for the electrocatalytic hydrogen evolution reaction (HER). Specifically, it needs an overpotential of 112 mV to reach a current density of 10 mA cm−2 with a small Tafel slope of 76 mV dec−1. X-ray absorption fine structure spectroscopy combined with density functional theory calculations unravels that the highly exposed coordinatively unsaturated Cu1-O2 centers could effectively accelerate the formation of key *H intermediates toward fast HER kinetics.
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Menon, E. S. K., M. Saunders, and I. Dutta. "Interface Characterization of Metallized CVD Diamond." Microscopy and Microanalysis 4, S2 (July 1998): 778–79. http://dx.doi.org/10.1017/s1431927600024016.
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Progress towards the large scale integration of active devices within electronics packages has imposed stringent heat dissipation requirements necessitating the development of innovative materials solutions. One possibility being considered is the use of chemically vapor deposited diamond (CVDD) thin films as heat sinks. However, there are technological challenges which must be overcome before these materials become commercially viable. For example, the CVDD substrate must be metallized to provide interconnections between the various devices in the package. Conventional metallizations, such as Au, Cu or Al, display poor adhesion to the diamond causing problems associated with the reliability and stability of metallized diamond packages. A novel solution has been proposed involving the consecutive deposition of a thin layer of Cr and an electrically insulating layer of alumina on the diamond substrate such that the thermal conductivity of the treated substrate is not degraded significantly.
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Niehus, Horst, Ralf-Peter Blum, and Dirk Ahlbehrendt. "Structure of Vanadium Oxide (V2O3) Grown on Cu3Au(100)." Surface Review and Letters 10, no. 02n03 (April 2003): 353–59. http://dx.doi.org/10.1142/s0218625x03004962.
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The epitaxial growth of vanadium oxide (V2O3) has been investigated by scanning tunneling microscopy (STM), low energy ion back-scattering (ISS) and low energy electron diffraction (LEED). Direct evaporation of vanadium onto metal surfaces (Cu, Au or Cu3Au) gives rise to massive surface alloying. The attempt to oxidize the vanadium film by consequent oxygen exposure leads to the formation of rough VO x films of poor quality and mixed valency. A new way of oxide formation has been developed by preoxidation of a Cu3Au substrate, which acts positively in two ways since it prevents completely alloy formation and also forces strong surface wetting of the vanadium oxide. As a result, two-dimensional layer growth of good quality has been achieved. Depending on the preoxygen content at Cu3Au(100), the amount of V deposition and annealing temperature, different epitaxial layers of vanadium oxides can be prepared. In particular, the surface structure of V2O3(0001) was investigated. The surface structure appears completely different from the half layer metal termination at Cr2O3(0001). Specifically, the full vanadium layer stabilized by one third of an oxygen layer located in pseudo bridge positions close to regular oxygen positions of a next layer. Close to defects the full vanadium layer appears also without oxygen stabilization.
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CHOU, H., H. S. CHEN, E. M. GYORGY, A. R. KORTAN, L. C. KIMERLING, F. A. THIEL, and M. K. Wu. "SUPERCONDUCTING PROPERTIES OF (Tl0.64Bi0.16Pb0.2)Ba2−xSrxCa3Cu4Oy BY LIQUID-GAS-SOLIDIFICATION PROCESSING." Modern Physics Letters B 05, no. 26 (November 10, 1991): 1735–43. http://dx.doi.org/10.1142/s0217984991002082.
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The effect of Sr substitution in (Tl0.64Bi0.16Pb0.2)Ba2−xSrxCa3Cu4Oy(x=0, 1, 2) superconductors is studied by liquid-gas-solidification process. (Tl0.64Bi0.16Pb0.2)Ba2−x SrxCa3Cu4Oy forms a tetragonal structure, with a c axis decreasing with Sr content. The substitution of Sr tends to suppress Cu-O layer formation. It also slows down the phase transformation from Tl-rich to Tl-poor phases which may be attributed to a phase equilibration of kinetic origin. The superconducting crystals grow under non-equilibrium and anisotropic conditions, and exhibit platelet and dentritic morphologies. The resistivity measurements indicate percolation effects with a percolation limit of just above 8% of the high Tc phase.
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Catledge, Shane A., Yogesh K. Vohra, Damon D. Jackson, and Samuel T. Weir. "Adhesion of nanostructured diamond film on a copper–beryllium alloy." Journal of Materials Research 23, no. 9 (September 2008): 2373–81. http://dx.doi.org/10.1557/jmr.2008.0287.
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Microwave plasma chemical vapor deposition (CVD) was used to coat nanostructured diamond onto a copper–beryllium alloy (∼1.7 wt% Be) commonly used as a nonmagnetic gasket material in diamond anvil cell devices. The coating is expected to be useful in preventing plastic flow of Cu–Be gaskets in diamond anvil cell devices, thus allowing for increased sample volume at high pressures and leading to improved sensitivity of magnetic measurements. The coatings were characterized by Raman spectroscopy, glancing-angle x-ray diffraction, microscopy (optical, scanning electron, and atomic force), Rockwell indentation, and nanoindentation. CVD diamond deposition on pure copper substrates has historically resulted in poor coating adhesion caused by the very large thermal expansion mismatch between the substrate and coating as well as the inability of copper to form a carbide phase at the interface. While an interfacial graphite layer formed on the pure copper substrates and resulted in complete film delamination, well-adhered 12.5 μm thick nanostructured diamond coatings were produced on the copper–beryllium (Cu–Be) alloy. The nanostructured diamond coatings on Cu–Be exhibit hardness of up to 84 GPa and can withstand strains from Rockwell indentation loads up to 150 kg without delamination.
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Dale, Phillip J., Monika Arasimowicz, Diego Colombara, Alexandre Crossay, Erika Robert, and Aidan A. Taylor. "Is it Possible to Grow Thin Films of Phase Pure Kesterite Semiconductor? A ZnSe case study." MRS Proceedings 1538 (2013): 83–94. http://dx.doi.org/10.1557/opl.2013.1006.
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ABSTRACTThe kesterite semiconductor Cu2ZnSnS(e)4 is seen as a suitable absorber layer to replace Cu(In,Ga)Se2 in thin film solar cells, if thin film photovoltaics are to be deployed on the terawatt scale. Currently the best devices, and hence the best kesterite absorber layers are grown away from stoichiometry and are zinc rich and copper poor, presumably leading to the formation of ZnS(e). However, it has been shown that secondary phases present in an absorber layer reduce device performance. If growth in Zn rich conditions seems to be mandatory, then any secondary phases formed should be grown on the surface of the absorber layer so that they may be easily removed by etching. Therefore, it is important to know how and why secondary phases form, and if possible, how to segregate them to the surface of the absorber layer.Here we show that ZnSe is formed at the initial stages of absorber formation from annealing metal stacks in selenium vapor. Further we demonstrate that the way the precursor metals are distributed on the substrate leads to different absorber layer performances in full devices. The importance of selenium vapor pressure is highlighted in respect to the order of selenisation of the metals, Zn before Cu. Additionally, the importance of selenium and tin selenide vapor pressure during annealing is reviewed with regard to avoiding a decomposition of the Cu2ZnSnSe4 to ZnSe and Cu2Se phases. Regardless of the atmosphere above the absorber, the reaction of the absorber with molybdenum appears unavoidable without the use of a passivation strategy. Counter-intuitively, it is demonstrated that for our absorber layers grown under Zn-rich conditions, removal of the ZnSe is harmful for device performance.
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Gao, Zeng, Congxin Yin, Dongfeng Cheng, Jianguang Feng, Peng He, Jitai Niu, and Josip Brnic. "Sintering Bonding of SiC Particulate Reinforced Aluminum Metal Matrix Composites by Using Cu Nanoparticles and Liquid Ga in Air." Nanomaterials 11, no. 7 (July 10, 2021): 1800. http://dx.doi.org/10.3390/nano11071800.
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SiC particulate reinforced aluminum metal matrix composites (SiCp/Al MMCs) are characterized by controllable thermal expansion, high thermal conductivity and lightness. These properties, in fact, define the new promotional material in areas and industries such as the aerospace, automotive and electrocommunication industries. However, the poor weldability of this material becomes its key problem for large-scale applications. Sintering bonding technology was developed to join SiCp/Al MMCs. Cu nanoparticles and liquid Ga were employed as self-fluxing filler metal in air under joining temperatures ranging from 400 °C to 500 °C, with soaking time of 2 h and pressure of 3 MPa. The mechanical properties, microstructure and gas tightness of the joint were investigated. The microstructure analysis demonstrated that the joint was achieved by metallurgical bonding at contact interface, and the sintered layer was composed of polycrystals. The distribution of Ga was quite homogenous in both of sintered layer and joint area. The maximum level of joint shear strength of 56.2 MPa has been obtained at bonding temperature of 450 °C. The specimens sintering bonded in temperature range of 440 °C to 460 °C had qualified gas tightness during the service, which can remain 10−10 Pa·m3/s.
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Lu, Yuzhen, Xiaoming Qiu, Ye Ruan, Cui Luo, and Fei Xing. "Effect of Ti on Microstructure and Properties of Tungsten Heavy Alloy Joint Brazed by CuAgTi Filler Metal." Materials 12, no. 7 (March 30, 2019): 1057. http://dx.doi.org/10.3390/ma12071057.
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In this paper, scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and X-ray diffractometer (XRD) were used to comprehensively analyze the microstructure and brazing performance of a CuAgTi filler metal with braze tungsten heavy alloys. The association of microstructure, wettability and shear strength of brazing joints was also investigated. With the addition of Ti, the Ti3Cu4 phase appeared in the microstructure of filler metal. Ti is active element that promotes the reaction of filler with tungsten. Therefore, the Ti element is enriched around tungsten and forms a Ti2Cu layer at the interface, leaving a Cu-rich/Ti-poor area on the side. Remaining Ti and Cu elements form the acicular Ti3Cu4 structure at the center of the brazing zone. The wettability of filler metal is improved, and the spreading area is increased from 120.3 mm2 to 320.9 mm2 with the addition of 10 wt.% Ti. The shear strength of joint reaches the highest level at a Ti content of 2.5 wt.%, the highest shear strength is 245.6 MPa at room temperature and 142.2 MPa at 400 °C.
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Cheng, Sirui, Jiang Ma, Feng Gong, and Jun Shen. "Thermoplastic Forming of a Hydrophilic Surface with a Nanostructure Array on Zr-Cu-Ni-Al-Y Bulk Metallic Glass." Metals 11, no. 10 (September 24, 2021): 1520. http://dx.doi.org/10.3390/met11101520.
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The poor thermoplastic formability of reactive Zr-based bulk metallic glass becomes the main limiting factor for replacing the noble-metal-based and Be-rich bulk metallic glasses in nanostructure fabrication. In our work, a (Zr50.7Cu28Ni9Al12.3)98.5Y1.5 bulk metallic glass with good thermoplastic formability has been developed by alloying, where Y addition enlarges the processing window and decreases the viscous resistance of supercooled liquid caused by the high free volume density. The prepared Zr-Cu-Ni-Al-Y bulk metallic glass nanostructure retains the amorphous characteristic and generates the complex oxidization products in the surface layer. The enhanced hydrophilicity of the as-embossed surface follows a Wenzel-impregnating wetting regime, and it can be attributed to the large roughness coefficient induced by the capillary effect. This study provides a low-cost and environmentally friendly bulk metallic glass system to manufacture the nanostructure with a broad prospect in the field of electrocatalysis.
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Kádár, Imre. "Effect of P, Zn and Cu Fertilization on Crops on a Calcareous Chernozem Soil." Agrokémia és Talajtan 51, no. 1-2 (March 1, 2002): 185–92. http://dx.doi.org/10.1556/agrokem.51.2002.1-2.22.
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Both deficiency and excess of P, Zn and Cu are common in soils and crops of Hungary. The excess and deficiency of P occurring in agricultural soils and crops is a consequence of previous fertilization practice. Zn deficiency occurs mainly on calcareous soils well fertilized with P under maize, while Cu deficiency is often detected on poor sandy soils and on organic soils under other crops. Zn and Cu excess has been measured in city soils, in soils near highways and industrial areas. In the present paper the effect of P supply is shown on yield and P/Zn ratios of crops, presenting the phenomena of the P-induced Zn deficiency on a calcareous loamy chernozem soil. In an other long-term field trial on the same soil, the effect of Cu and Zn loads was studied on soil and crop. The main conclusions drawn from these long-term field experiments are as follows: 1. An excess of available P in the plough layer of this soil might be detected by the ammonium lactate (AL) method when the soil analysis shows concentrations higher than 150-200 mg/kg P 2 O 5 . The P/Zn ratios of 6-leaf stage shoots and harvested straw of maize grown on these plots might be higher than 200, while that of grain 150-200. 2. In the frame of a fertilization program, P-induced Zn deficiency can be counterbalanced effectively on such calcareous chernozem soils with the application of P and Zn fertilizers in a ratio around 10:1. 3. The Cu content of crops could not be markedly raised by using CuSO 4 fertilizer, even with rates as high as 270 or 810 kg/ha Cu. However, as an effect of increased NxP fertilization, the Cu content of maize grain doubled, or that of maize straw was 4-times higher. This is an important tool for the Cu enrichment of animal diet, when maize straw is also used for animal feeding. 4. The soil and plant analysis data are proper means of controlling soil fertility and crop nutritional status when the soil and plant data are previously calibrated in long-term field experiments.
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Duguet, Thomas, Samuel Kenzari, Valérie Demange, Thierry Belmonte, Jean-Marie Dubois, and Vincent Fournée. "Structurally complex metallic coatings in the Al-Cu system and their orientation relationships with an icosahedral quasicrystal." Journal of Materials Research 25, no. 4 (April 2010): 764–72. http://dx.doi.org/10.1557/jmr.2010.0101.
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Quasicrystals have been identified as alloys possessing unusually low surface energy. This results in poor adhesion properties of quasicrystalline coatings when deposited on metallic substrates, hindering the development of these new materials for technological applications. Here we investigate the possible use of complex Al-Cu metallic phases as interface layers to accommodate the structural and electronic mismatch between a quasicrystalline coating and a metallic substrate and improve adhesion. First, we show that all stable low-temperature phases of the Al-Cu system can be grown as thin films using DC magnetron sputtering. Among the various possible phases, we select the γ-brass γ-Al4Cu9 as a promising candidate for the interface layer. Then the γ-Al4Cu9 phase is grown on the fivefold surface of an icosahedral (i-) Al-Pd-Mn quasicrystal. The interface is investigated by transmission electron microscopy and shows a clear texturing of the film. The grains exhibit rotational epitaxy with the substrate. We find that the interface is mainly composed of a β-phase of unknown chemical composition and sometimes exhibits γ grains in direct contact with the quasicrystalline substrate. Occasionally, we observe a fourth phase at the β/γ interface, identified as β1, possessing a lattice parameter aβ1 equal to 2aβ and 2/3aγ.
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Bae, Sung, Sungsoon Kim, Seong Yi, Injoon Son, Kyung Kim, and Hoyong Chung. "Effect of Surface Roughness and Electroless Ni–P Plating on the Bonding Strength of Bi–Te-based Thermoelectric Modules." Coatings 9, no. 3 (March 26, 2019): 213. http://dx.doi.org/10.3390/coatings9030213.
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In this study, electroless-plating of a nickel-phosphor (Ni–P) thin film on surface-controlled thermoelectric elements was developed to significantly increase the bonding strength between Bi–Te materials and copper (Cu) electrodes in thermoelectric modules. Without electroless Ni–P plating, the effect of surface roughness on the bonding strength was negligible. Brittle SnTe intermetallic compounds were formed at the bonding interface of the thermoelectric elements and defects such as pores were generated at the bonding interface owing to poor wettability with the solder. However, defects were not present at the bonding interface of the specimen subjected to electroless Ni–P plating, and the electroless Ni–P plating layer acted as a diffusion barrier toward Sn and Te. The bonding strength was higher when the specimen was subjected to Ni–P plating compared with that without Ni–P plating, and it improved with increasing surface roughness. As electroless Ni–P plating improved the wettability with molten solder, the increase in bonding strength was attributed to the formation of a thicker solder reaction layer below the bonding interface owing to an increase in the bonding interface with the solder at higher surface roughness.
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Kötschau, I. M., and H. W. Schock. "Depth profile of the lattice constant of the Cu-poor surface layer in (Cu2Se)1−x(In2Se3)x evidenced by grazing incidence X-ray diffraction." Journal of Physics and Chemistry of Solids 64, no. 9-10 (September 2003): 1559–63. http://dx.doi.org/10.1016/s0022-3697(03)00074-x.
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Theodore, N. David, Vida Ilderem, and Ming Pan. "Oxide-induced deterioration of TiSi2 source/drain MOSFET contacts." Proceedings, annual meeting, Electron Microscopy Society of America 52 (1994): 862–63. http://dx.doi.org/10.1017/s0424820100172048.
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A simple process for formation of a metal-oxide-semiconductor field-effect transistor (MOSFET) involves fabrication of a polysilicon/oxide gate between source and drain regions. Contact is made to source/drain regions by use of TiSi2 layers followed by Al(Cu) metal lines. A silicide layeris used toreduce contact resistance. TiSi2 is chosen as a contact layer because in the C54phase, the silicide has a lower resistivity (~12 μΏ-cm) than most other silicides (except for CoSi2 ~10-15 μΏ-cm). During formation of TiSi2 contact layers to MOSFET source/drain regions, a deterioration of the TiSi2 is occasionally observed. The deterioration typically consists of buckling and delamination of Ti(TiSi2) films from the source/drain regions. When buckling occurs, electrical contact between Al metal and MOSFET source/drain regions is quite poor. The present study investigates the microstructure and behavior of TiSi2 contact layers used at source/drain regions of MOSFETs. The cause of deterioration of contact-layers is investigated and a potential solution to this problem is explored.
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Guo, Zhi Qiang, Xiang Li, Xiao Guang Yuan, and Hong Jun Huang. "Effects of Extrusion Methods and Powder Carriers on Powder Forming and Precursor Foaming Behavior in the Preparation Process of Aluminum Foam." Advanced Materials Research 634-638 (January 2013): 1734–39. http://dx.doi.org/10.4028/www.scientific.net/amr.634-638.1734.
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Aluminum foam is a new type of material that can be used in many fields. Compaction conditions are the most important parameters that have influence on foam preparation process. So in this paper, detailed researches about extrusion methods and powder carriers are conducted. The results show that: compare with direct extrusion, pre-pressing can effectively eliminate the influences of hydrogen, obtain high density precursors. However, when the flank of the precursor is wrapped with copper, H2 can escape from the combination parts of Al and Cu, in early foaming stage. The minimum density is only 0.75g/cm3, pore structures are almost round and nearly no plateau borders exist, so the quality of aluminum foam is still poor. When there is no copper wrapped, an oxide layer can be formed in the whole body of the precursor and limit the escaping of H2. The minimum density can reach 0.45g/cm3, pore structures are polygonal with thin cell walls about 0.08mm. Thus high quality aluminum foams can be obtained by using pre-pressing and then extruding method and precursor sheet powder carrier.
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Chen, Jin, Fengchao Wang, Bobo Yang, Xiaogai Peng, Qinmiao Chen, Jun Zou, and Xiaoming Dou. "Fabrication of Cu2ZnSnS4 Thin Films Based on Facile Nanocrystals-Printing Approach with Rapid Thermal Annealing (RTA) Process." Coatings 9, no. 2 (February 19, 2019): 130. http://dx.doi.org/10.3390/coatings9020130.
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In the current study, Cu2ZnSnS4 (CZTS) thin film was successfully fabricated by the facile nanocrystals (NCs)-printing approach combined with rapid thermal annealing (RTA) process. Firstly, the CZTS NCs were synthesized by a thermal solution method and the possible formation mechanism was analyzed briefly. Then the influences of RTA toleration temperature and duration time on the various properties of as-printed thin films were examined via XRD, Raman, FE-SEM, UV-vis-IR spectroscopy, EDS and XPS treatments in detail. As observed, the RTA factors of temperature and time had significant impacts on the structure and morphology of as-prepared thin films, while there were no obvious effects on the band gap energy in studied conditions. The results showed that the obtained thin film at optimal RTA conditions of (600 °C, 20 min) featured a kesterite structure in pure phase and an irregular morphology consisting of large grains. Moreover, the satisfactory composition of a Cu-poor, Zn-rich state and an ideal band gap energy of 1.4 eV suggests that as-fabricated CZTS thin film is a suitable light-absorbing layer candidate for the application in thin film solar cells.
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Gladyshevskii, R. E., and R. Flükiger. "Modulated structure of Bi2Sr2CaCu2O8+δ, a high-T c superconductor with monoclinic symmetry." Acta Crystallographica Section B Structural Science 52, no. 1 (February 1, 1996): 38–53. http://dx.doi.org/10.1107/s0108768195007075.
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The structure of the bismuth strontium calcium cuprate Bi2.09Sr1.90Ca1.00Cu2O8.22 (Tc = 90 K) was studied by single-crystal X-ray diffraction. A two-component modulation vector was found with respect to the C-centred orthorhombic cell of the average structure [a = 5.4112 (7), b = 30.873 (7), c = 5.4161 (20) Å, q = 0.21 c * + 0.14 b *]. Refinement was performed in a ninefold supercell [Mr = 902, monoclinic, mS548-0.4, Cc (No. 9), a = 37.754 (7), b = 5.4109 (8), c = 41.070 (9) Å, β = 103.58 (2)°, V = 8155 (2) Å3, Z = 36, Dx = 6.61 Mg m−3] to wR = 0.057. As in orthorhombic Bi2Sr2CaCu2O8+δ, the structure of this new monoclinic variant contains perovskite-derived slabs delimited by a BiO layer on each side. All metal atoms show a transverse displacement wave which has the largest amplitude for the Cu and Ca atoms. In addition, the Bi and Sr atoms are displaced longitudinally. Bi-rich regions with a distorted rocksalt-type atom arrangement and Bi-poor regions with chains of corner-linked BiO3 ψ-tetrahedra are formed. One additional oxygen site per translation unit of the modulation wave was detected in the Bi-poor regions of the chains, giving the composition Bi9O10. Approximately 10% of Bi substitution was found on the Ca sites, but no clear indication of preferential sites was observed. A partial substitution by Ca was refined at Sr sites situated near the regions where the additional O atoms are located. The monoclinic symmetry corresponds to a systematic shift of the modulation waves of consecutive slabs by π/9 with respect to orthorhombic Bi2Sr2CaCu2O8+δ.
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Eizenberg, M. "Chemical Vapor Deposition of TiN for Sub-0.5 μm ULSI Circuits." MRS Bulletin 20, no. 11 (November 1995): 38–41. http://dx.doi.org/10.1557/s0883769400045541.
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Titanium nitride (TiN) has been recognized as an excellent barrier material in various metallization structures of advanced microelectronic devices. TiN serves as a nucleation/glue layer as well as a barrier against WF6 attack in W plug filling. It serves as a diffusion barrier during or after high-temperature Al reflow processing for contact and via filling. TiN is considered as a diffusion-barrier material for Cu metallization as well. In addition, it is utilized as an antireflection coating layer, especially on top of Al, an application that will not be discussed in this article.TiN films must conform to the extreme topographies used in devices in order to guarantee void-free plug formation as well as Jow junction leakage. This should be achieved with the thinnest films possible in order to reduce interconnect stack thickness and to lower contact or via resistance. (The TiN resistivity is higher than that of the other components of the metallization—Ti, Al, or W.) In addition, the good barrier properties must be retained following various thermal cycles used in multilevel metallization. Finally, the metallization must be manufacturing-worthy, namely, it should be reliable and reproducible, it should have a very low particle content, and it should have a low cost of ownership.At present, TiN is mainly deposited by physical vapor deposition (PVD) via reactive sputtering. However, the poor conformality of sputtered TiN films over extreme topography limits the use of this deposition technique for deep sub-0.5 μm applications, especially those with features that have high aspect ratios.
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Camprubí, Antoni, Edith Fuentes-Guzmán, Pilar Ortega-Larrocea, María Colín-García, Janet Gabites, Luis F. Auqué, Vanessa Colás, and Eduardo González-Partida. "The Pliocene Ixtacamaxtitlán low sulfidation epithermal deposit (Puebla, Mexico): A case of fossil fungi consortia in a steam-heated environment." Boletín de la Sociedad Geológica Mexicana 72, no. 3 (November 28, 2020): A140420. http://dx.doi.org/10.18268/bsgm2020v72n3a140420.
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The Ixtacamaxtitlán area in northern Puebla (central Mexico) contains middle Miocene Cu-Mo-Au porphyry/skarn and Pliocene low-sulfidation Au-Ag epithermal deposits that are geologically associated with the evolution of the Trans-Mexican Volcanic Belt (TMVB). In this paper, a new 40Ar/39Ar age (2.87 ± 0.41 Ma) is provided for rhombohedral alunite from a kaolinite + alunite ± opal ± cristobalite ± smectite advanced argillic alteration assemblage. This age contributes to the definition of a metallogenic province that is confined to the TMVB, a relevant feature for regional exploration. A ~12 My gap is established between the formation of the Cu-Mo-Au porphyry/skarn and low-sulfidation Au-Ag epithermal deposits, which rules out the possibility that their overlapping was the result of telescoping. Advanced argillic alteration is conspicuous throughout the mineralized area. This alteration assemblage consists of a widespread kaolinite-rich blanket that underlies silica sinters, polymictic hydrothermal breccias, and an alunite-rich spongy layer that consists of vertical tubular structures that are interpreted as the result of gas venting in a subaerial environment. The above indicate a shallow hypogene origin for the advanced argillic alteration assemblage—that is, formation by the partial condensation within a phreatic paleoaquifer of acidic vapors that were boiled-off along fractures that host epithermal veins at depth. The formation of the spongy alunite layer and silica sinters is interpreted to have been synchronous. Within the alunite-rich spongy layer, tubular structures hosted microbial consortia dominated by fungi and possible prokaryote (Bacteria or Archaea) biofilms. Such consortia were developed on previously formed alunite and kaolinite and were preserved due to their replacement by opal, kaolinite, or alunite. This means that the proliferation of fungi and prokaryotes occurred during a lull in acidic gas venting during which other organisms (i.e., algae) might have also prospered. Periodic acidic gas venting is compatible with a multi-stage hydrothermal system with several boiling episodes, a feature typical of active geothermal systems and of low-sulfidation epithermal deposits. The microstructures, typical for fungi, are mycelia, hyphae with septa, anastomoses between branches, and cord-like groupings of hyphae. Possible evidence for skeletal remains of prokaryote biofilms is constituted by cobweb-like microstructures composed of <1 µm thick interwoven filaments in close association with hyphae (about 2.5 µm thick). Bioweathering of previously precipitated minerals is shown by penetrative biobrecciation due to extensive dissolution of kaolinite by mycelia and by dissolution grooves from hyphae on alunite surfaces. Such bioweathering was possibly predated by inorganically driven partial dissolution of alunite, which suggests a lull in acidic gas venting that allowed living organisms to thrive. This interpretation is sustained by the occurrence of geometrical dissolution pits in alunite covered by hyphae. Fungal bioweathering is particularly aggressive on kaolinite due to its relatively poor nutrient potential. Such delicate microstructures are not commonly preserved in the geological record. In addition, numerous chalcopyrite microcrystals or microaggregates are found within the alunite layer, which could be related to sulfate reduction due to bacterial activity from the sulfate previously released by fungal bioweathering of alunite. Hydrogeochemical modeling constrains pH to between ~3.2 and ~3.6 and temperature to between 53 and 75 °C during the stage in which fungi and other organisms thrived. These waters were cooler and more alkaline than in earlier and later stages, which were characterized dominantly by steam-heated waters. The most likely process to account for this interlude would be mixing with meteoric water or with upwelling mature water that did not undergo boiling.
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Rehan, Muhammad, Hyeonmin Jeon, Yunae Cho, Ara Cho, Kihwan Kim, Jun-Sik Cho, Jae Ho Yun, Seungkyu Ahn, Jihye Gwak, and Donghyeop Shin. "Fabrication and Characterization of Cu2ZnSnSe4 Thin-Film Solar Cells using a Single-Stage Co-Evaporation Method: Effects of Film Growth Temperatures on Device Performances." Energies 13, no. 6 (March 12, 2020): 1316. http://dx.doi.org/10.3390/en13061316.
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Kesterite-structured Cu2ZnSnSe4 (CZTSe) is considered as one of the Earth-abundant and non-toxic photovoltaic materials. CZTSe films have been prepared using a single-step co-evaporation method at a relatively low temperature (i.e., below 500 °C). Due to the volatile nature of tin-selenide, the control over substrate temperature (i.e., growth temperature) is very important in terms of the deposition of high-quality CZTSe films. In this regard, the effects of growth temperatures on the CZTSe film morphology were investigated. The suitable temperature range to deposit CZTSe films with Cu-poor and Zn-rich compositions was 380–480 °C. As the temperature increased, the surface roughness of the CZTSe film decreased, which could improve p/n junction properties and associated device performances. Particularly, according to capacitance-voltage (C-V) and derived-level capacitance profiling (DLCP) measurements, the density of interfacial defects of CZTSe film grown at 480 °C showed the lowest value, of the order of ~3 × 1015 cm−3. Regardless of applied growth temperatures, the formation of a MoSe2 layer was rarely observed, since the growth temperature was not high enough to have a reaction between Mo back contact layers and CZTSe absorber layers. As a result, the photovoltaic (PV) device with CZTSe film grown at 480 °C yielded the best power conversion efficiency of 6.47%. It is evident that the control over film growth temperature is a critical factor for obtaining high-quality CZTSe film prepared by one-step process.
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Li, Yan, Feng-Jun Nie, Li-Cheng Jia, Sheng-Jun Lu, and Zhao-Bin Yan. "Geochemical Characteristics, Palaeoenvironment and Provenance of Uranium-Bearing Sandstone in the Sifangtai Formation, Northern Songliao Basin, Northeast China." Minerals 11, no. 9 (September 18, 2021): 1019. http://dx.doi.org/10.3390/min11091019.
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During the Cretaceous period of the northern Songliao Basin (northeast of China), a 100 m thick layer of fluvial-phase sandstone (Sifangtai Formation) with uranium potential was widely deposited, but its geochemical characteristics, paleoenvironment, and provenance remain unknown. This research proposes a new set of relevant geochemical data for sandstones to investigate their paleoenvironment, provenance and tectonic setting. The results revealed that: (1) The sandstone of the Sifangtai Formation was dominated by feldspar lithic sandstone. Geochemical signatures demonstrate that these sandstones have a high silicon content (SiO2 = 68.30~83.60 wt%) and total alkali content, but are poor in magnesium and calcium. They are also enriched in Rb, Th, U, K and LREE, and depleted HFSE (e.g., Nb, Ta), with crustal magmatic source. (2) The paleoclimate discriminant indicated that the rocks of the Sifangtai Formation might that the climate of Sifangtai Formation is semi-arid, and the chemical weathering of the source rocks is weak under the semi-arid climate environment. (3) The combination of element Sr/Ba, 100 MgO/Al2O3 and the combination of v/v + Ni, V/Cr, Ni/Co, and Sr/Cu indicated that the paleo-water medium was deposited in an oxygen-rich freshwater environment when the Sifangtai Formation was deposited. (4) The discriminate diagrams showed that almost all the sandstones of the Sifangtai Formation fell in the range of the active continental margin, indicating that the source area of the sandstones of Sifangtai Formations is an active continental margin tectonic environment, and the source is a felsic rock developed in the Xiaoxing’an Ridge and Zhangguangcailing area.
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Sun, H., and K. M. Flores. "Laser deposition of a Cu-based metallic glass powder on a Zr-based glass substrate." Journal of Materials Research 23, no. 10 (October 2008): 2692–703. http://dx.doi.org/10.1557/jmr.2008.0329.
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Laser Engineered Net Shaping (LENS™) is a laser-assisted manufacturing process that offers the possibility of producing metallic coatings and components with highly nonequilibrium microstructures. In this work, the microstructure developed by LENS deposition of Cu47Ti33Zr11Ni8Si1 powder on a bulk metallic glass substrate, with nominal composition Zr58.5Nb2.8Cu15.6Ni12.8Al10.3, is investigated. Single-layer deposition results in the formation of an inhomogeneous but partially amorphous layer above a crystalline heat-affected zone. Elemental analysis of the deposited layer indicates incomplete mixing of the powder with the melt pool. The as-deposited alloy exhibits a single glass transition event and its primary crystallization event is consistent with the first crystallization temperature of the Cu-based powder. Subsequent remelting of this layer results in a still partially amorphous deposit with a uniform composition of (Zr + Nb)51.8Cu24.7Ti3.4Ni16.4Al3.7. The remelted layer exhibits a structural rearrangement immediately prior to the primary crystallization event, possibly associated with the formation of a quasicrystalline phase.
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Babbe, Finn, Leo Choubrac, and Susanne Siebentritt. "Quasi Fermi level splitting of Cu-rich and Cu-poor Cu(In,Ga)Se2absorber layers." Applied Physics Letters 109, no. 8 (August 22, 2016): 082105. http://dx.doi.org/10.1063/1.4961530.
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Sawyer, Victoria, Xiao Tao, Huan Dong, Behnam Dashtbozorg, Xiaoying Li, Rachel Sammons, and Han-Shan Dong. "Improving the Tribological Properties and Biocompatibility of Zr-Based Bulk Metallic Glass for Potential Biomedical Applications." Materials 13, no. 8 (April 22, 2020): 1960. http://dx.doi.org/10.3390/ma13081960.
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Zr-based bulk metallic glasses (Zr-BMGs) are potentially the next generation of metallic biomaterials for orthopaedic fixation devices and joint implants owing to their attractive bulk material properties. However, their poor tribological properties and long-term biocompatibility present major concerns for orthopaedic applications. To this end, a novel surface modification technology, based on ceramic conversion treatment (CCT) in an oxidising medium between the glass transition temperature and the crystallisation temperature, has been developed to convert the surface of commercially available Zr44Ti11Cu10Ni11Be25 (Vitreloy 1b) BMG into ceramic layers. The engineered surfaces were fully characterised by in-situ X-ray diffraction, glow-discharge optical emission spectroscopy, scanning electron microscopy, transmission electron microscopy, and scanning transmission electron microscopy. The mechanical, chemical, and tribological properties were evaluated respectively by nano-indentation, electrochemical corrosion testing, tribological testing and the potential biocompatibility assessed by a cell proliferation assay. The results have demonstrated that after CCT at 350 °C for 40 h and at 380 °C for 4.5 h the original surfaces were converted into to a uniform 35–55-nm-thick oxide layer (with significantly reduced Ni and Cu concentration) followed by a 200–400-nm-thick oxygen-diffusion hardened case. The surface nano hardness was increased from 7.75 ± 0.36 to 18.32 ± 0.21 GPa, the coefficient of friction reduced from 0.5–0.6 to 0.1–0.2 and the wear resistance improved by more than 60 times. After 24 h of contact, SAOS-2 human osteoblast-like cells had increased surface coverage from 18% for the untreated surface to 46% and 54% for the 350 °C/40 h and 380 °C/4.5 h treated surfaces, respectively. The significantly improved tribological properties and biocompatibility have shown the potential of the ceramic conversion treated Zr-BMG for orthopaedic applications.
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Marciniak, Monika, Michael Meagher, Jon Davis, and Jack Josefowicz. "FAILURE ANALYSIS OF DISCOLORED ENIG PADS IN THE MANUFACTURING ENVIRONMENT." International Symposium on Microelectronics 2014, no. 1 (October 1, 2014): 000653–61. http://dx.doi.org/10.4071/isom-wp24.
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Manufacturing of electronic assemblies using printed circuit boards (PCBs) with electroless nickel/immersion gold (ENIG) surface finishes requires front-end PCB evaluation that will guarantee that good quality product enters the assembly line. The most common is an IPC-4552 mandated plating thicknesses verification of 3-6μm and a minimum of 0.05μm for nickel and gold, respectively. Coupled with visual examination, this verification method suffices for general PCB acceptance but may not be robust enough in cases where ENIG plating in PCBs is compromised. That poses challenges in the manufacturing environment, where resulting latent defects are detected in downstream processes but not at upfront incoming inspection. Manifestation of such latent anomaly was observed in the form of ENIG pad discoloration with variations from yellow, red or grey discolored surfaces to a more pronounced plating degradation, such as corrosive pitting. The launched failure analysis involved evaluation of manufacturing processes suspected to contribute to the cause of the condition. Effects of thermal processes, cleaning methods, soldering, parylene deposition and factory cleanliness were examined thoroughly. Concurrently, metallurgical analysis of ENIG pads was performed, where samples were subjected to scanning electron microscopic/energy dispersive x-ray spectroscopic (SEM/EDX) cross section analysis, Auger electron spectroscopy (AES) and gold (Au) and electroless nickel (Ni) surface examination. The resulting analysis revealed a highly porous electroless nickel coating with deep crevasses and fissures penetrating down to the base copper (Cu) layer. These open nickel boundaries were attributed to the corrosive environment within ENIG plating, which resulted in the pad surface discoloration. The root cause of ENIG pad discoloration and pitting was traced back to poor ENIG line process controls. Subsequent introduction of a nickel controller into the ENIG line were the implemented countermeasures. To mitigate the effects of discoloration at the electronic assembly level, a tinning process was implemented to prevent nickel plating oxidation and to ensure that good wettability for reliable solder joints was maintained.
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Kozlovskyy, V., and N. Romanyuk. "The impact of pine self-afforestation on podzolization process in semi-natural grassland areas of Volyn Polissya (Ukraine)." Studia Biologica 15, no. 2 (2021): 47–62. http://dx.doi.org/10.30970/sbi.1502.651.
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Background. Several theories have been proposed to explain the podzolization process. Currently, the role of organic matter in both weathering and immobilization in the illuvial horizon is clearly stated. The origin of soil organic matter and, accordingly, the various mechanisms of its influence on the soil material, create the basis of these theories. We assume that in the base-poor sandy soils under rich herbaceous vegetation with a well developed sod layer, the process of podzolization may also depend on CO2 soil formation agent . Materials and Methods. Four localities along a Pinus sylvestris L. self-afforestation chronosequence with pine stands of 10, 20, 40 yrs and an adjacent semi-natural grassland area were investigated in order to determine the patterns of podzolization process on sandy glacial till deposits. Soil pH, exchangeable base, soil cation exchange capacity, total content of soil organic carbon, amorphous Fe, Si and Al and total contents of Al, Fe, Mn, Zn, Cd, Pb, Cu, Co, Ni, Na, K were determined. Statistical analysis of the results was performed using LibreOffice for Linux. Results. During the pine succession, a previously well differentiated into horizons podzolic soil under the grassland vegetation community gradually degrades. Previously well-defined albic and spodic diagnostic horizons disappear, the soil profile becomes more acidic, the soil organic carbon, the base cation content and the base cation saturation decrease, the leaching rate of aluminium and iron increases. Secondary podzolization features in the soil profiles were detected 40 years after the onset of afforestation. The podzolization has not been intensive enough to develop fully fledged albic and spodic diagnostic horizons over such a short period. Conclusions. Based on the obtained soil morphological, physical and chemical properties, three most important agents of podzolization are proposed as principal for the studied area. The main gent under pine forest is fulvic acids that are produced during coniferous litter decomposition. Low molecular weight organic acids and carbon dioxide produced to the rhizosphere by roots and a root associated microbiota are mainly involved in the podzolization process under the grassland ecosystem.
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Aydin, Remzi, and Idris Akyuz. "Two-stage production and characterization of Cu-poor kesterite CZTS absorber layers." Optik 200 (January 2020): 163407. http://dx.doi.org/10.1016/j.ijleo.2019.163407.
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