bluuebunny/crossref_metadata_2025_split huggingface dataset:
In-Situ Observation of Electrodeposition in a Microfluidic Device with through Silicon Via Model
Authors: Akita Takanori , Otsuka Yuki , Irita Masaru , Hayase Masanori 
Published: December 2020

Nowadays, the high performance of integrated circuits is due to packaging technologies, and 3d-packaging using TSVs (Through Silicon Vias) have entered use in commercial products. Copper electroplating is used to form TSVs, since bottom-up filling is available using a combination of several additives, but the filling mechanism is not clear yet. Recently, we have observed the adsorption and deactivation behavior of typical suppressing additives by using a disk electrode with a diameter of 100 μm in a microchannel that allows precise control of mass transport [1]. In this study, in order to understand the details of the TSV filling behavior, we propose a microfluidic device that has TSV feature in the channel, and in-situ observation of the electrodeposition behavior is enabled.
The microfluidic device was fabricated using the silicon substrate. First, Au is sputtered on the silicon substrate and the Au film is patterned by photolithography and wet etching. Then, the micro channel is defined by a 19 μm thick photoresist pattern on the silicon substrate. In the micro channel, a rectangular area on Au film is exposed. The exposed Au film and the surrounding resist pattern model the TSV. The width, height, and depth of the via are 20 μm, 19 μm and 100 μm, respectively. Finally, a glass cover plate is put on the substrate, and the microchannel is mounted on a base. A mercury sulfate electrode (MSE) is connected to the resin base and works as a reference electrode. A copper wire is inserted into the outlet tube and works as a counter electrode.
An acid copper sulfate plating solution was prepared as a VMS (Virgin Makeup Solution). Initially, additive-free VMS was supplied, and the working electrode was pre-plated with copper. Then, the solution was switched to the VMS + Leveler and open circuit potential was maintained for 120 s. Finally, -600 mV vs. MSE was applied on the working electrode, and plating behavior was observed. Figure 1 shows the appearance of the working electrode along time. At 5 s, clear interface was observed at the depth around 20 μm from the opening of the via. Below the interface, the working electrode became dark because the deposition proceeded. While no obvious change was observed above the interface and it was found that the deposition was strongly suppressed by the leveler adsorption. The interface line inclined and it was assumed that the leveler penetrated deeper in downstream side because of the solution flow.
Reference
[1] T. Akita, M. Tomie, R. Ikuta, H. Egoshi, and M. Hayase, J. Electrochem. Soc., 166(1), D3058 (2019).

Figure 1
Directly Visualized Mechanical Strain Distribution in Package Interconnect Using Digital Image Correlation
Authors: Lee Tae-Ik , Paik Kyung-Wook , Kim Taek-Soo 
Published: December 2020

For advanced package interconnects, analyzing strain distribution within the complex three-dimensional structure is important in order to design a mechanically reliable system. Electronic packages frequently undergo various types of deformation including tension, compression, bending, and thermal treatments. Failures under these loading modes can be prevented with accurate information of distribution and degree of the mechanical strains. This information, however, is difficult to obtain using conventional methods due to the small-sized packages with complex internal structures. It is also uncertain to rely on predictive results from analytical solutions because it is hard to theoretically calculate the complex strain mechanics, especially for the heterogeneously integrated structures. Therefore, experimental methods have been recently demanded for direct evaluation of mechanical deformation in the package interconnects.
In this study, a novel method that visualizes and accurately measures the internal strain distribution in package interconnects is developed. This method is based on digital image correlation (DIC), which utilizes microscopic images of the internal structure. The DIC method is adopted by taking advantage of non-contact and full-field analysis capability. Images from both optical microscopy and scanning electron microscopy are utilized for the non-contact strain evaluation method for the micro-scale deformation analysis. In order to obtain clear image of the internal structure, mechanical polish is conducted to form cross-section. For image pattern tracking, micro/ nano sized particles are deposited onto the cross-section to serve as speckle pattern of the DIC analysis. After the specimen preparation, the digital images are obtained before and after a mechanical loading at a same position. The consecutive images are then compared to execute image tracking analysis to result in the microscopic deformation contour. The results can be fully adopted in prediction of failure site or failure modes by providing essential data such as weak spot or intensity of deformation. Using the quantitative strain information, predicting the failure cycle could be also possible based on mechanics of fatigue fracture.
We demonstrate that this method is effectively utilized for various package interconnects including printed circuit boards (PCBs), flexible chip packages, and through-hole stress analysis in a 3-D stacked structure. Bending strain analysis of flexible packages and composite substrates, thermal strain analysis of the PCB interconnects are shown as applications of the thermo-mechanical reliability evaluation method. We believe that this experimental method will enable to fully understand the internal stress-strain behavior of the advanced package interconnects and flexible devices that require high mechanical reliability for commercialization.
Study of Refining and Purification Processing of Gallium Metal As a Raw Materials for Compound Semiconductor
Authors: Yoon Jaesik , Yang Jaeyeol 
Published: December 2020

Gallium is used in III-V compound semiconductors according to the development of the semiconductor industry, and increasingly requires high purity gallium metal, and the amount of use is also increasing. The rare earth metal, gallium, has low reserves, which makes it difficult to supply raw materials. Therefore, process waste containing gallium is used to secure raw materials.
In this study, high-purity gallium metal was fabricated from process wastes by electrolytic refining and Czochralski(CZ). The CZ device was operated in a clean room of 400 class or less for a high purity environment, and the source crucible was controlled with oxidation of metal using sodium hydroxide and mineral oil. Gallium has a low melting point of 303 K, so the seed portion was cooled to 260 K to make an ingot.
The impurity elements in the highly purified gallium metal of about 8N grade was quantitatively analyzed using a glow discharge mass spectrometer(GD-MS). In quantitative analysis using GD-MS, relative sensitivity factors(RSF) are used. For RSF of each element, a standard sample containing gallium as an impurity in an aluminum matrix was used. By analyzing the aluminum matrix CRM, quantitative analysis is possible for a total of 17 elements: Mg, Si, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Zr, Ag, Cd, Sn, Pb, Bi, etc. Lastly, in the analysis of gallium crystallized using the CZ method, four of impurity elements were detected: Al, Si, Cr, and Fe, and all other elements were below the detection limit. In the quantitative analysis of impurities in the gallium metal, the total impurity element was 5.58 ppbw, and the final purity of gallium was about 99.9999994% (8N).
(Invited) Design Hybrid Nanocomposites As Electrode Materials for High Performance Na-Ion Batteries
Authors: Yu Yan 
Published: December 2020

Sodium-ion batteries are of major importance, especially for large-scale energy storage devices, due to low cost and abundant source of sodium. As for the anode side, commercial graphite shows a limited capacity for sodium storage. Compared to graphite based intercalation, the electrode materials based on conversion and alloy have been identified as promising anode candidates for sodium storage due to high theoretical capacity. However, poor kinetics and large volume change result in a low reversible capacity and fast capacity decay.
In order to address the above problems, we have designed a series of carbon-based hybrid materials with hierarchical structures, such as carbon nanowire-encapsulated selenides, carbon nanosheet-supported sulfides, and mesoporous carbon-encapsulated phosphorus. These multi-scale and hierarchically organized structures construct a highly efficient and stable mixed conductive network around the nano-active components. At the same time, they can keep the electrode integrity on cycling. These lead to excellent electrochemical performance.
(Invited) Complex Phase Transitions in Layered Sodium Transition Metal Oxides
Authors: Kim Jae Chul , Kwon Deok-Hwang , Yang Julia , Ceder Gerbrand 
Published: December 2020

As an alternative to Li-based technologies to develop stationary energy storage systems, Na-ion batteries have attracted substantial interest. Unlike the Li-ion, layered sodium transition metal oxide (NaTMO2) cathodes can diversify their redox centers from expensive Co to cheap Mn and Fe to achieve high energy density, offering a wide variety of chemistry selection to design low-cost, high-performance batteries.1 These cathode materials often undergo discontinuous, yet reversible, phase transitions upon Na intercalation due to complex interatomic interactions, which result in multiple plateau-like features in their voltage profiles. However, large desodiation of Fe-containing Na-ion cathodes often leads to an unclarified, irreversible phase transition at high voltage, hindering the full use of Fe redox.2

In this talk, we will discuss how transition metal selection affects the thermodynamic stability of desodiated structures of NaTMO2. First, we demonstrate this insight by comparing two prototypical compositions, NaNi0.5Co0.5O2 and NaNi0.5Fe0.5O2, with detailed experimental and computational investigation.3 The Na intercalation processes of the two compounds are carefully investigated by electrochemical methods and in situ X-ray diffraction. We confirm that although the two materials share the same Ni3+/Ni4+ redox, their structural changes are very different from each other. Na
x
Ni0.5Co0.5O2 goes through multiple phase transitions including three different O3-type and three different P3-type structures. In contrast, Na
x
Ni0.5Fe0.5O2 only undergoes a generic O3-P3 transition with no sign of monoclinicity, leading to a smoothly increasing voltage profile. Second, our recent findings on a quaternary transition metal system, NaTi0.25Fe0.25Co0.25Ni0.25O2,4 will be underlined. We will present structural evidence and characterization of the highly-desodiated, high-voltage phase that exhibits peculiar oxygen stacking. This phase consists of alternating octahedral and prismatic Na layers, namely OP2 stacking, in which formation is afforded by distortion-tolerant Ti and Jahn-Teller-active Fe. Moreover, we will demonstrate that this new phase participates in redox reaction reversibly, fundamentally distinct from inactive high-voltage phases in many Na-ion cathodes. Finally, a strategy to stabilize Fe-containing NaTMO2 materials to create layered cathodes with high reversible Na capacity will be briefly discussed. Our results demonstrate that we can manipulate the redox reaction and associated structure change by transition metal mixing.
References

Yabuuchi, K. Kubota, M. Dahbi, and S. Komaba, Chem. Rev., 2014, 114, 11636−11682

Jeong, H. Lee, J. Yoon, and W.-S. Yoon, J. Power Sources, 2019, 439, 227064

Vassilaras, D.-H. Kwon, S. T. Dacek, T. Shi, D. -H. Seo, G. Ceder, and J. C. Kim, J. Mater. Chem. A, 2017, 5, 4596–4606

Vassilaras, S. T. Dacek, H. Kim, T. T. Fister, S. Kim, G. Ceder, and J. C. Kim, J. Electrochem. Soc., 164, 2017, A3484–A3486
(Invited) Challenges of Today for Na Based Batteries of the Future
Authors: Casas-Cabanas Montserrat 
Published: December 2020

The global rise of Li-ion battery (LIB) production is linked with a number of challenges. From one side, the growing risks of demand-supply mismatch and supply constraints of the raw materials. From the other, environmental and social challenges linked with the mass production of LIBs become increasingly important as the market expands. Indeed, LIBs contain a number of critical raw (and/or toxic) materials, such as cobalt and natural graphite, whose suppliers concentrate in a number of third countries, including conflict zones. Within this scenario, Na-based batteries are rising as potential alternative technology to Li-ion batteries, as the combination of attractive properties potentially NIBs offer (i.e., low cost, sustainable precursors and secure raw material supplies), fill a niche and could represent an important step forward towards beyond Li technologies in certain applications where energy density is less critical.
Na-ion chemistry suffers however from some intrinsic drawbacks compared to Li-ion (heavier and larger alkali ion, 0.33V larger standard potential) which tend to lower cell voltage and capacity. Nevertheless, with ongoing development, materials available for Na-ion cells should allow approaching the energy density of the present generation of Li-ion commercial cells.
In this talk, the potential of Na-ion batteries will be thoroughly analyzed and our recent research regarding positive and negative electrode materials will be reviewed. Results related to several phosphate-based families of cathode materials will be shown, together with the challenges of developing competitive anode materials. Finally, a high-throughput screening approach capable of quickly revealing the possible existence of good ionic conductor materials in the huge structural and compositional space of existing explored databases will be discussed.
(Invited) SiC and GaN High Aspect Ratio Nanostructures By Plasma-Free Photo-Assisted Inverse-Macetch
Authors: Michaels Julian , Chan Clarence , Li Xiuling 
Published: December 2020

Etching wide bandgap semiconductors including SiC and GaN, has been challenging. Achieving damage-free device quality high aspect ratio nanostructures is even more difficult. Currently, to produce SiC or high aspect ratio structures, ICP-RIE is generally used, which often results in high energy ion induced damages.
Metal-assisted chemical etching (MacEtch) defies the isotropic nature of chemical etch by utilizing a patterned metal catalyst for spatially defined etching of semiconductors. MacEtch has been successfully demonstrated for various types of semiconductors, including Si, GaAs, InGaAs, AlGaAs, InP, InGaP, GaN, b-Ga2O3, SiC. The metal catalyst type that has been proven to be effective include Au, Pt, Ir, Ru, TiN, CNTs, and graphene. Aspect ratios produced using MacEtch can readily exceed 100:1 in some cases, while limited in other cases. The resulted tapering and porosity are strong function of the etch kinetics for the particular semiconductor material, metal catalyst type and pattern, and etchant condition. The loading effect is determined by the local carrier generation rate and mass transport rate. Depending on how the etching evolves relative to the catalyst pattern and additional assistance, we classify MacEtch into forward, inverse (i-MacEtch), magnetic-fielded guided (h-MacEtch), self-anchored-catalyst (SAC-MacEtch), vapor phase (VP-MacEtch), and UV assisted (UV-MacEtch).
In this work, we report the successful demonstration of SiC and GaN nanostructures with various sidewall morphologies using UV-assisted i-MacEtch. Produced structures are characterized as a function of etch conditions by SEM, 3D profilometer, AFM, reflection and Raman spectroscopy, as well as the interface properties using Schottky barrier diodes and MOSCAP structures. This work lays the foundation for producing 3D wide bandgap device structures with damage-free pristine surfaces and interfaces, as well as controlled defect engineering for quantum states.
Characterization of Hazy Morphology on AlInP/GaAs Epitaxial Wafers Grown by Organometallic Vapor Phase Epitaxy
Authors: Peng Hongyu , Ailihumaer Tuerxun , Liu Yafei , Raghothamachar Balaji , Dudley Michael 
Published: December 2020

6-inch AlInP/GaAs epitaxial wafers grown by organometallic vapor phase epitaxy (OMVPE) technique are being developed for light emitting diodes (LEDs) applications [1]. Recently, dislocation configurations in the GaAs substrates and AlInP epilayers have been characterized and conditions for relaxation and formation of misfit dislocations were analyzed [2,3]. Apart from defects such as dislocations, epilayer surface reveals a hazy morphology formed when the epitaxial growth pressure is increased. It is observed that the epilayer surface is rougher compared to regular clear regions as revealed by both optical microscopy and atomic force microscopy. Additionally, the size of the hazy regions increases with growth pressure but other growth parameters such as growth temperature, V/III ratio, likely influence the onset of hazy morphology. Previous research on the formation of hazy features reports that these can be caused by the deficiency of phosphorus [4], lowered V/III ratio [5] or stacking faults [6]. However, the hazy features in our case, are different from the ones reported. Synchrotron X-ray topographs of the hazy regions showed blurred contrast, indicating disordered lattice arrangement. Moreover, internal structure of the hazy regions was studied by reciprocal space mapping (RSM), where weakened and broadened peaks around the clear epilayer peak were observed using 004 reflection, indicating continuously varying strain and tilt between the hazy region and the clear region. The thickness of the hazy regions was also analyzed by employing the 002 RSM, where the X-ray penetration depth is lower. Comparison of the 002 and 004 RSMs reveals that at the beginning of epitaxial growth, the epilayers do not suffer from lattice distortion and the formation of the hazy morphology occurs when a critical thickness is exceeded.
Reference:
[1] C. H. Chen, S. A. Stockman, M. J. Peanasky, C. P. Kuo. Brightness Light Emitting Diodes Semiconductors and Semimetals, SEMICONDUCT SEMIMET, 48 (1997) pp. 97–144
[2] Hongyu Peng, Tuerxun Ailihumaer, Yafei Liu, Balaji Raghothamachar and Michael Dudley, J. Cryst. Growth, 533 (2020) 125458
[3] Hongyu Peng, Tuerxun Ailihumaer, Balaji Raghothamachar and Michael Dudley, J. Electron. Mater. 49, 3472–3480 (2020)
[4] H. H. Ryu, M. H. Jeon, J. Y. Leem, H. J. Song, L. P. Sadwick, G. B. Stringfellow, J Mater Sci (2006) 41:8265–8270
[5] D. S. Cao and G. B. Stringfellow, Journal of Electronic Materials, Vol. 20, No. 1, 1991
[6] Yoshihiro Hiraya, Fumiya Ishizaka, Katsuhiro Tomioka and Takashi Fukui, Applied Physics Express 9, 035502 (2016)

Figure 1
Rapid Annealing of Perovskite Solar Cells through Intense Pulsed Light
Authors: Druffel Thad 
Published: December 2020

The perovskite solar technology has managed a fair amount of excitement since it was first introduced nearly ten years ago by Miyasaka’s group. The efficiency of small devices has increased rapidly from the 3.8% reported by Miyasaka to well over 20%. The efficiency now stands near that of the market dom,inated crystalline silicon solar cell, and the durability has been demonstrated for upwards of 1,000 hours. The organo-metal halide perovskite that is the core layer of the perovskite solar cell can be deposited using simple solution phase processes at low temperatures. The materials tend to have very high defect tolerances and hence have long excited charge carrier lifetimes. The excitement in the research and manufacturing communities’ centers around the simplicity of the device fabrication. Other layers within the stack also lead to simple solution phase deposition and low temperature processing.
The deposition of the perovskite material generally involves a precursor chemistry that undergoes evaporation and crystallization. The crystallization typically involves thermal energy often at temperatures less than 100 oC. The activation energy of the organo-metal halide perovskite crystallization is very low especially when compared to that of amorphous silicon. Thus annealing is typically accomplished using low temperatures conduction (hot plates); however, several studies using radiative processes inducing much higher temperatures have also been established.
These radiative processes include the intense pulsed light process (IPL). The IPL process involves the absorption of light energy into a thin film from an intense rapid pulse with a broad spectrum that can cover large areas. A thin film with absorptivity within the spectrum of light will absorb the energy, which is then rapidly transformed into thermal energy. The technology has been utilized in processing polymers, metals, metal oxides and semiconductors since the 1970’s and was recently reviewed specifically for materials in the photovoltaic technologies. The advantage of this technique for plastic substrates is that it can initiate very high temperatures within a thin film without damage to the underlying substrate.
In this work we will describe the intense pulsed light process as it relates to the annealing of perovskite solar cells on plastic substrates on a roll-to-roll manufacturing line. The work will include the description of careful control of the IPL process parameters and the impact on the crystallization of the perovskite layer. The talk will concentrate on the tuning the IPL parameters to fit into high speed roll-to-roll applications. The films are characterized using UV-Vis spectroscopy, x-ray diffraction and scanning electron microscopy. Finally, devices built on the roll-to-roll platform will be discussed.