bluuebunny/crossref_metadata_2025 huggingface dataset:
Innovative Temperature Management of SOFC Stacks
Authors: Bossel Ulf
Published: February 2020

Solid Oxide Fuel Cells required a sensitive temperature control for the following reasons:

 

- Rapid heating of SOFC stacks to operating temperature

- Precise maintenance of the stack temperature

- Variation of the stack temperature with changing power demand.

 

An innovative system for the management of SOFC stack temperatures has been developed and will be presented at the conference. This system comprised four key elements.

 

- Some or all bipolar plates are equipped with electric heaters. Heat is supplied where heat is needed – directly to the ceramic SOFC elements;

- The stack temperature is precisely monitored by a thermocouple placed in the geometric center of the stack;

- Electric power is supplied to the heaters only when heating is needed (start-up or increased power demand);

- A temperature controller is used to supply power (AC or DC) from external sources to the heaters as needed to obtain or maintain desired SOFC stack temperatures.

 

This innovative SOFC stack temperature management system will be described in detail. Experimental results show that the innovative solution (patents pending) offers significant advantages compared to conventional methods of indirect stack heating combined with remote temperature measurements in the stack environment. With this innovative temperature management of SOFC stacks operational temperatures above 600°C are reached in a few minutes after cold start.
Sodium Doped Strontium Silicates as Electrolyte for Intermediate Temperature Solid Oxide Fuel Cells
Authors: Kundur Anjaneya Chandrappa , Singh Mahander Pratap , Sethuraman Vijay A.
Published: February 2020

Solid oxide fuel cells (SOFCs) are considered as important green energy devices for the 21st century due to its high chemical to electrical energy conversion efficiency, modular design and fuel flexibility. However, the widespread commercialization of SOFCs has not been realized due to its cost associated with cell fabrication, electrode/ electrolyte materials and its maintenance. The conventional electrolyte, Yttria-stabilized Zirconia requires high operating temperature (800 - 1000 0C) to achieve sufficient oxide-ion conductivity, which increases the cost and exacerbates the instability between the components [1]. Therefore, there is considerable interest in developing alternative electrolytes with oxide ion conductivity > 10−2 S/ cm at intermediate temperature (IT) (500 - 700 0C). Hence, here we successfully synthesized IT electrolytes Sr1−xNaxSiO3−
d (x = 0.0, 0.45) by solid state reactions. XRD, Solid state NMR, FE-SEM/ EDS and impedance spectroscopy are used for the structural and electrical studies. From the XRD, it is evident that both the samples can be indexed in monoclinic c2/c space group (15) [2]. 29Si solid state NMR reveals a sharp single peak at −86 ppm for SrSiO3. Broadening of the peak at ~ −89 ppm indicates the presence of glassy Na2Si2O5 phase in Sr0.55Na0.45SiO3−
d [3]. FE-SEM image of Sr0.55Na0.45SiO3−
d clearly shows the amorphous Na2Si2O5 dispersed in SrSiO3 insulating crystalline phase. EDS analysis confirms that grain is Na-deficient (SrSiO3) and grain boundary (GB) is Na-rich phase (Na2Si2O5). The doping of Na into SrSiO3 leads to the formation and segregation of glassy Na2Si2O5 along the GBs, which is the main reason for high electrical conductivity. Among, Sr1−xNaxSiO3−
d (x = 0.0, 0.45), SrSiO3 behaves as an insulator and Sr0.55Na0.45SiO3−
d exhibits highest conductivity in the measured temperature range, which makes it as electrolyte for intermediate temperature SOFCs.

Figure 1
Microstructure Variation of Ni-YSZ by Infiltration Using Urea Precipitation Method and Their Electrochemical Properties
Authors: Hong Jae-Woon , Son Chanjin , Kim In-Ho , Namgung Yeon , Song Sun-Ju
Published: February 2020

Impregnation or infiltration are terms used to describe the process of depositing nano particles into electrode structure. Using infiltration of nano particles, cell performance can be improved due to increased three phase boundary (TPB) where electrochemical reactions occur. So, by infiltration of dispersed particles, we can expect more performance due to increased surface area. But, many literatures related to infiltration for improving performance deal with almost air electrode infiltration. Commonly, Ni and electrolyte materials are used as fuel electrode. To infiltrate nano particles, fuel electrode needs appropriate porosity and maintains porous structure. But, it is hard for fuel side electrode to maintain its structure because Ni can be oxidized to NiO easily during heat treatments. So, not to be reoxidized, reduction of fuel electrode was done at the last process. And, one side reduction is necessary because air electrode can be decomposed in low pO2 condition. To infiltrate dispersed nano particles, we used urea precipitation method because it gives the solution precipitating ligands to whole solution so that precipitations occur homogeneously. Because urea needs decomposition time, urea concentration should be higher than cation concentration so as to precipitate whole cations. Thus, urea/cation concentration ratio and aging time were chosen as variables. Infiltration was conducted to Ni-YSZ support whose air electrode side was blocked by epoxy. After infiltration, epoxy was burned out at 600oC with fuel electrode flowed by H2. Finally, electrochemical properties were investigated by I-V curve, EIS and DRT.
(Invited) Heteroatom Enhanced Sodium Ion Capacity and Rate Capability in a Hydrogel Derived Carbon Give Record Performance in a Hybrid Ion Capacitor
Authors: Mitlin David , Ding Jia
Published: February 2020

We employed a polypyrrole hydrogel precursor to create a carbon framework that possesses both huge heteroatom content (13 wt% nitrogen and 11 wt% oxygen) and high surface area (945 m2g-1) that is equally divided between micropores and mesopores. A sodium ion capacitor (NIC, HIC) electrode fabricated from this N and O Functionalized Carbon (NOFC) has tremendous reversible capacity and rate capability, e.g. 437 mAh g-1 at 100 mA g-1, and 185 mAh g-1 at 1600 mA g-1. This is among the most favorable reported, and is due to copious nanoporosity that enables fast ion sorption at the many N and O moieties and graphene defects. The NOFC imbues a NIC device with energy-power characteristics that are not only state-of-the-art for Na hybrids, but also rival Li systems: Ragone chart placement is 111 Wh kg-1 and 38 Wh kg-1 at 67 W kg-1 and 14,550 W kg-1, respectively, with 90% capacity retention at over 5,000 charge/discharge cycles.
(Invited) Aggregation-Induced Emission in Lamellar Solids of Colloidal Perovskite Quantum Wells
Authors: Jagielski Jakub , Kumar Sudhir , Shih Chih-Jen
Published: February 2020

The outstanding excitonic properties, including photoluminescence quantum yield (η
PL), of individual, quantum-confined semiconductor nanoparticles are often significantly quenched upon aggregation, representing the main obstacle towards scalable photonic devices. Here we report aggregation-induced emission (AIE) phenomena in the lamellar solids containing layer-controlled colloidal quantum wells (CQWs) of hybrid organic-inorganic lead bromide perovskites, resulting in anomalously high solid-state of up to 94%. Upon forming the QW solids, we observe an inverse correlation between exciton lifetime and , clearly distinct from that in typical quantum dot solid systems. Our multiscale theoretical analysis reveals that in a lamellar solid, the collective motion of the surface organic cations are more restricted to orient along the [100] direction, thereby inducing a more direct bandgap that facilitates radiative recombination. Using the QW solids, we demonstrate ultra-pure green emission by completely downconverting a blue GaN light emitting diode (LED) at room temperature, with a luminous efficacy higher than 90 lm/W at 5,000 cd/m2, which has never been reached in any nanomaterial assemblies by far [1].

[1] Jagielski et al., Science Advances, accepted manuscript (2017)
Correlation of Band Electronic Structure to Efficiency in Perovskite Solar Cells with Vanadium Oxide Buffers
Authors: Eom Kiryung , Yoo Il-han , Han Hoseong , Seo Hyungtak
Published: February 2020

Over the past few years, solar cells with an organo metal halide perovskite structure have been well studied and attracted attention due to their excellent basic properties such as diffusion length of long charge carriers, good electrical properties, and light absorption coefficient, as well as easy and inexpensive solution processability. According to the efficiency chart, perovskite solar cells have achieved efficiencies of 22.1% in 2016 through rapid development with efficiency starting at 3.8%. However, despite these high efficiencies, one of the biggest problems of perovskite solar cells is the low stability and reliability of the devices in the atmosphere. For commercialization of perovskite solar cells, it is necessary to analyze and improve stability and efficiency. In the structure of the device, the electron transporting layer (ETL) and the hole transporting layer (HTL) transport charges, respectively, and mainly organic materials are used. The stability of the device can be enhanced by inserting a charge transporting layer of an inorganic material such as NiOx, ZnO, and VOx, which is superior in stability to organic materials such as PEDOT: PSS and Spiro-OMeTAD. Among them, p-type VOx with wide bandgap is used as HTL and can replace PEDOT: PSS. It is also important to note that in such a stacked heterojunction solar cell structure, band bending occurs due to different band gaps. Due to the non-optimization of conduction band offset (CBO) and valence band offset (VBO) at the interface between the absorption layer and the charge transport layer, it is possible to secure a smooth movement path of electrons and holes, and conversely, recombination of electrons and holes can be a cause of reduction in efficiency. Perovskite solar cells are also attracting attention as a strategy for improving efficiency at the interface between the charge transporting layer and the absorber layer. In this study, the efficiency difference and electronic structure analysis were carried out in planar heterojunction structure with ITO/VOx/Perovskite/PCBM/ZnO/Al structure fabricated by two process methods. The VOx buffer layer was deposited by vacuum deposition using RF magnetron sputtering and spin casting method. The VBM and core levels at the interface were measured using optical bandgap and depth profile x-ray photoelectron spectroscopy. After that, CBO and VBO values were derived from the calculations and the mechanism of electron and hole transport was clarified. As a result, it has been confirmed that the perovskite solar cell fabricated by the RF sputter process has an efficiency of about 13% and the device manufactured by the spin casting method has an efficiency of about 8%, and the reason for the difference efficiency is explained in relation to the electronic band structure.
Design of Bodipy-Based Triplet Photosensitizers and Applications in Triplet-Triplet Annihilation Upconversions
Authors: Zhao Jianzhang
Published: February 2020

Triplet photosensitizers (PSs) are the compounds showing strong absorption of visible light, efficient intersystem crossing (ISC) thus high triplet state yield and good photostability.1 Triplet PSs are widely used in photocatalysis, photodynamic therapy (PDT), and recently the triplet-triplet annihilation upconversion (TTA UC).2 However, the conventional triplet photosensitizers are limited to the porphyrin complexes and Ru(II), Pt(II) complexes, and some halogenated xanthane dyes, such as Eosin Y. It is still a major challenge to design a new triplet photosensitizer which show predictable ISC, especially for those contain no heavy atoms because the intersystem crossing (ISC) of metal-free organic chromophores is usually unpredictable.

TTA UC has attracted much attention, due to the strong absorption of the photoexcitation energy, high upconversion quantum yields, and low photoexcitation threshold (excitation light power density can be as low as 5 mW cm-2. Solar light is sufficient). However, most of the conventional triplet photosensitizers are Pt(II)/Pd(II) porphyrin complexes.1 These complexes are difficult to prepare and to purify, and the molecular structures are unable to be modified feasibly. We proposed a few new approaches to prepare triplet PSs, such as to use Bodipy as the chromophore in heavy atom-containing compounds, or with C60 as the electron spin converter heavy atom-free organic photosensitizers.3

Scheme 1. A strategy to prepare heavy-atom-free organic triplet photosensitizer.

Reference

(a) Singh-Rachford, T. N.; Castellano, F. N. Coord. Chem. Rev. 2010, 254, 2560−2573. Zhao, J.; Wu, W.; Sun, J.; Guo, S.; Chem. Soc. Rev.
2013, 42, 5323; (b) Kamkaew, A.; Lim, S. H.; Lee, H. B.; Kiew, L. V.; Chung, L. Y.; Burgess, K. Chem. Soc. Rev.
2013, 42, 77.

(a) Zhao, J.; Ji, S.; Guo, H. RSC Adv., 2011, 1, 937. (b) Zhao, J.; Ji, S.; Wu, W.; et al., RSC Adv., 2012, 2, 1712.

(a) Zhang, C.; Zhao, J.; Wu, S.; et al, J. Am. Chem. Soc.
2013, 135, 10566; (b) Wu, W.; Zhao, J., et al., J. Org.
Chem.
2012, 77, 5305−5312; (c) Wu, W.; Zhao, J., et al., J. Org.
Chem., 2011, 76, 7056–7064; (d) Guo, S.; Zhao, J., et al., Chem. Sci., 2015, 6, 3724–3737. (e) Chen, Y., Zhao, J., et al., RSC Adv., 2012, 2, 3942–3953.

Figure 1
Probing Local Corrosion Performance of Sol-Gel/MAO Composite Coating on Mg Alloy Using Svet and Leis
Authors: Gu Yanhong , Zheng Xinhua
Published: February 2020

Sol-gel technique was used to prepare Ca10 (PO4)6(OH)2 (HA) coating on Microarc oxidation (MAO) coated Mg alloy to improve its corrosion resistance in simulated body fluid (SBF). The microstructure and phase composition of the coating samples were analyzed using scanning electron microscopy (SEM) and X-ray diffraction (XRD). The hardness and adhesion strength of the coating were investigated by micro-hardness tester and scratch tester. The results show that HA was detected in the MAO and sol-gel/MAO composite coating, and the critical load of the MAO and sol-gel/MAO coatings were about 3.8N and 8.3N, respectively. In order to probe the corrosion behavior of sol-gel/MAO HA coating on magnesium alloy, global and local corrosion characteristics were both evaluated. Potentiodynamic polarization (PDP) and electrochemical impedance spectroscopy (EIS) were used to evaluate the global corrosion behavior of these coatings in SBF. Scanning vibrating electrode technique (SVET) and local electrochemical impedance spectroscopy (LEIS) were applied to evaluate the potential distribution and impedance differences among the different zones. The global measurements show that the sol-gel/MAO coating has much better corrosion resistance than MAO coating, resulting from the fact that sol-gel coating sealed the pores produced in the MAO process. In SVET measurement, the coating area has much lower current density than the artificial scratch. The corrosion current density in the scratch of the sample decreases until 3h immersion, and then the value increases when the immersion time reaches 6h. The impedance value from LEIS has the opposite trend with the current density, which is consistent with the result of SVET. The artificial defect influenced the corrosion behavior of the coatings significantly. The post-corrosion microstructures of the samples have the consistent results with local corrosion performance. A phenomenological model for the mechanism of the localized corrosion of sol-gel/MAO composite coating on magnesium alloy was proposed.
Distribution of Corrosion Potentials across Galvanically Coupled Interfaces Exposed in Drinking Water
Authors: Fabbricino Massimiliano , Korshin Gregory V
Published: February 2020

Control of lead release from lead-containing materials galvanically coupled with copper or bronze represent a challenge for corrosion engineers and water treatment practitioners. Currently available data show that in some situations galvanically coupled lead remains passivated and releases little metal while in other cases, for instance those associated with changes of ambient water chemistry, previously passive coupled lead becomes active with resultant episodes of elevated lead release.

While this problem has been thoroughly investigated on a phenomenological level, current understanding of the electrochemistry of galvanic stimulation of lead corrosion and release in drinking water remains insufficient. The goal of this study was to quantify changes of the open circuit corrosion potential (Ecorr(x)) across lead/copper interfaces as a function of the distance from the galvanic juncture and concentrations of background salts such sodium chloride, carbonate and others. The theory developed by Song et al. 2010 provides a detailed mathematical description of the distribution of Ecorr across galvanic interfaces but this theory has been developed and rested for systems that are notably different from those typical for drinking water. Measurements of trans-galvanic interface Ecorr profiles performed in this study showed that Ecorr(x) profiles conformed to predictions made based on the existing theory and the effective length of the longitudinal penetration of ionic currents increased as a square root of solution conductivity. The effective length of the coupled ionic currents was notably different for copper and lead. The data demonstrate that short- and long-term changes of properties of ambient water can cause Ecorr(x) to undergo considerable changes. This can potentially induce shifts of the galvanically affected zone in which accelerated lead release takes place. Further studies are needed to examine actual effects of such Ecorr(x) shifts on spatially localized lead release from galvanically coupled lead-containing materials.

Song, G. L. (2010). Potential and current distributions of one-dimensional galvanic corrosion systems. Corrosion Science, 52(2), 455-480
Influence of Heat Input on Corrosion Resistance of Welded UNS S32205 Investigated By EIS
Authors: Franco Juliana Panceri , Penna Kirlene Salgado Fernandes , Ribeiro Josimar
Published: February 2020

The corrosive behavior of the UNS S32205 duplex stainless steel (DSS), as base metal and welded by the welding of inert gas of tungsten (IGT) process with pulsed current, was investigated using different heat inputs. The corrosion evaluation was performed by means of electrochemical tests such as Potentiodynamic Polarization and Electrochemical Impedance Spectroscopy in a solution of 3.5% NaCl. The change in microstructure was visualized by optical microscopy revealing the presence of metastable pits that did not have the time or the favorable conditions for growth. The results indicate that welding processes with higher heat inputs generate a lower cooling rate in the welding region, guaranteeing a higher austenite phase precipitation, making the microstructure more balanced, thus increasing the corrosion resistance compared to samples welded with lower heat inputs.

Figure 1
Effect of Hot-Dip Aluminizing on High-Temperature Corrosion of Fe-Cr Steels
Authors: Lee Dongbok , Kim Min Jung
Published: February 2020

Hot-dip aluminizing is a simple, cost-effective diffusion coating technique that can coat aluminum on diverse substrates with complicated shapes. It is carried out by dipping the substrate into molten Al bath for a certain period, and pulling out of the bath into the air. The employed substrates were mostly carbon steels, low alloyed steels, Fe-(Si, Cr) alloys. During hot-dipping, inter-diffusion between the steel substrate and molten Al occurs to produces the Al-rich topcoat, the outer FeAl3 layer, and the inner Fe2Al5 layer. The property of these aluminized layers depends on various hot-dipping parameters such as bath composition, time, temperature, and substrate. In this study, hot-dipping was performed on Fe-Cr alloys, and the corrosion behavior of aluminized Fe-Cr alloys at high temperatures was studied. The corrosion tests were performed in air, SO2-containing atmospheres, and H2S-containing atmospheres. Hot-dip aluminizing was found as an effective coating technique, which could form protective α-Al2O3 scales not only in air but also in (SO2, H2S)-containing aggressive corrosive environments due to high thermodynamic stability of Al2O3. ACKNOWLEDGEMENT. This work was supported by the project “Development of the High-Efficiency Low-Emission Future Energy Production Technology (EO15580)” of National Research Council of Science & Technology (NST) grant by the Korea government (MSIP) (No. CRC-15-07-KIER).
Anodic Oxidation of Bismuth Towards Various Nanostructures
Authors: Sopha Hanna , Macak Jan M.
Published: February 2020

The synthesis of highly-ordered nanostructures of valve metal oxides has recently attracted huge scientific and technological interest motivated by their possible use in many applications. The two most established members of this group of materials are nanoporous Al2O3 and TiO2 nanotubes [1,2]. While Al2O3 membranes have been since than widely used as template material of choice for a range of materials [3-5] due to the flexibility of the pore diameter/length and the relative ease of the Al2O3 dissolution, TiO2 nanotubes received high attention because of their applications in e.g. photocatalysis, water splitting, solar cells and biomedical uses [6].

Bismuth oxide is another interesting material and its nanostructures show an enhanced photoelectrochemical performance [7,8]. However, the formation of bismuth nanostructures, such as bismuth oxide nanopores [7, 8] or bismuth phosphate nanorods [9], by anodization is not well explored by now.

Similar to the formation of nanoporous Al2O3, nanostructured Bi2O3 can be produced in acidic, F--free electrolytes [10]. In this presentation, we will demonstrate the anodization of bismuth in various electrolytes towards morphologically very interesting Bi2O3 nanostructures with many potential applications.

References

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J.M. Macak et al., Curr. Opin. Solid State Mater. Sci. 1-2 (2007) 3.

K. Nielsch, F. Müller, A.-P. Li, U. Gösele, Adv. Mater. 12 (2000) 582.

H. Asoh et al., J. Electrochem. Soc. 148 (2001) B152.

J. Kolar, J. M. Macak, K. Terabe, T. Wagner, J. Mater. Chem. C, 2 (2014) 349.

K. Lee, A. Mazare, P. Schmuki, Chem. Rev. 114 (2014) 9385.

X. Lv, J. Zhao, X. Wang, X. Xu, L. Bai, B. Wang, J. Solid. Stat Electrochem. 17 (2013) 1215.

K.C. Chitrada, K. S. Raja, R. Gakhar, D. Chidambaram, J. Electrochem. Soc. 162 (2015) H380.

M. Yang, N. K. Shrestha, R. Hahn, P. Schmuki, Electrochem. Solid-State Lett. 13 (2010) C5.

H. Sopha, V. Podzemna, L. Hromadko, J. M. Macak, Electrochem. Commun. 84 (2017) 6-9.
Pt-Rh Alloy Corrosion By Phosphorous Diffusion
Authors: Nakano Anna , Nakano Jinichiro , Bennett James P , Morral John
Published: February 2020

In addition to arsenic, silicon, and sulfur; phosphorous is also known to cause severe degradation of platinum-based alloys, leading to thermocouple failure or erroneous EMF output during industrial operation at elevated temperatures. The alloy behaviors in contact with phosphorous, an element commonly present in gasification carbon feedstock, industrial ores, and certain refractory bricks used in glass, metallurgical and gasification processes, are, however, not well documented. In this work, diffusion of phosphorous from a gaseous source that interacts with a Pt-30 wt.% Rh alloy was isothermally investigated at 1285 K. Interdiffusion of P and Rh through the fcc alloy led to the formation of two layers with distinguishable microstructures consisting of (Pt, Rh)2P, liquid, platelets, and fcc. The Pt-Rh alloy corrosion mechanism will be explained using microstructural evolutions.
Auxiliary Electrodes for Chromium Vapor Sensors
Authors: Fergus Jeffrey , Shahzad Moaiz , Britt Tommy
Published: February 2020

Measurement of chromia-containing vapors in solid oxide fuel cell systems is useful for monitoring and addressing cell degradation caused by oxidation of the chomia scale formed on alloys for interconnects and balance-of-plant components. One approach to measuring chomium is to use a solid electrolyte with an auxiliary electrode that relates the partial pressure of the chromium-containing species to the mobile species in the electrolyte. One example is YCrO3 which can equilibrate with the chromium-containing vapor and yttrium in yttria stabilized zirconia to establish an oxygen activity. Another is Na2CrO4 which can equilibrate with the chromium-containing vapor to establish a sodium activity. In this paper, results on the use of these systems in chromium sensors will be presented.
Thermal, High and Low Cycle Fatigue Life of 80 Micron Thick Graded Alumina PVD Coatings for Oxidation Resistance Application
Authors: K H Thulasi Raman
Published: February 2020

In this study, to accommodate higher interfacial shear stress between alumina coating system and metallic substrate, coating modulus and compressive stresses are graded from interface to 80 µm thickness. . The modulus gradient is achieved by varying Al to O ratio by tuning the oxygen flow and compressive stresses are varied from 0.1GPa to 2.5GPa by changing bias voltage during the reactive sputtering process. Static thermal fatigue life of coated samples were evaluated using simple heating and cooling cycles, significant change in microstructures and mechanical properties were observed. Room temperature high fatigue cycle (HCF) was evaluated using vibration testing and the coating fatigue life was evaluated as 2.0X106 cycles. Low cycle fatigue was evaluated using axial compressive and tensile mode and the coatings were cracked beyond 10,000 cycles. The Micro tensile testing revelled that modulus and compressive stress graded coatings are failed at 1.1% tensile strain and which is higher tensile load bearing capacity than the monolithic stoichiometric alumina coating. Hardness and modulus of the 80 µm thickness is 34GPa and 240 GPa. At higher strain coating started cracking and post-microscopy analysis shows variation of crack width at different zones of the tensile specimen. .
(Keynote) Surface Capping and the Shape Evolution of Colloidal Metal Nanocrystals
Authors: Xia Younan
Published: February 2020

Surface capping plays a critical role in determining the final shape taken by colloidal metals nanocrystals. However, the mechanism is not always clear as it is still a challenging task to even determine the coverage density of capping agents on the final nanocrystals. In this talk, I will use a few examples from our own research to illustrate the critical importance of a quantitative measure of surface capping in understanding the shape evolution of colloidal metal nanocrystals, as well as in predicting the shape evolution process. The examples include bromide ions for the Pd system and poly(vinyl pyrrolidone) for the Ag system. In addition to experimental measurements, computational simulation also offers insightful guidance for the identification of effective capping agents for shape-controlled synthesis.
(Invited) Additives in Cu Plating for Microelectronics Applications
Authors: Radisic Aleksandar , Ross Frances M , Haesevoets Karel P , Struyf Herbert , Vereecken Philippe M.
Published: February 2020

Electrodeposition is a prevailing method in fabrication of Cu interconnects in microelectronics due to its ability to fill complex structures having a wide range of critical dimensions. A typical acidified Cu electrolyte contains a number of additives, organic and inorganic species in ppm amounts, with a specific role in the plating process. The additives in Cu plating have been extensively studied in the past couple of decades, and grouped according to their role in filling/creating features for microelectronics applications. This categorization is not a uniform one, and it might differ from author to author. In one popular convention, organic additives in the so-called three-component plating bath are named accelerator, suppressor and leveler, with their names hinting at how they influence Cu deposition. Ultimately, it is thanks to these additives that defect-free Cu features ranging from tens of nanometers to hundreds of micrometers can be economically fabricated.

However, it is not enough to successfully fill a given single feature. The same has to be done for all the features on a 300 mm wafer, and then performed reproducibly over and over again. So, one needs to monitor the state of the electrolyte, i.e. of all the bath constituents, and either replace or replenish the electrolyte when the need arises. Additives could also have a strong influence on the physical properties of the deposit and therefore have a strong influence on the post-plating processing results. An additive that promotes void-free deposition of Cu structures in the end might not be used in a production line if it creates issues in the processing steps following electrodeposition.

In our presentation we focus on a number of specific examples showing the effect of additives on nucleation and growth of Cu, propagation of Cu fronts on resistive substrates, post-plating processing, and their use in substrate surface modifications. A closer look is taken into in situ microscopic and electrochemical techniques and their use in studies of electrochemical nucleation and growth of Cu. We discuss advantages and drawbacks of potential step and galvanostatic deposition techniques in determining nucleation and growth parameters, and selection criteria for additive sets for a given plating task. We demonstrate that substrate surface modifications prior to plating could help simplify bath composition, i.e. eliminate need for some additives in the electrolyte, or improve the filling performance of the given plating bath. We also give examples of additives that promoted void-free filling of features but also influenced physical/mechanical properties of the final product in such a way that rendered it unusable in a specific application.
Superconformal Cu Electrodeposition: Seiras and STM Study of the Polyether-SPS-Cl System
Authors: Liu Guokun , Zou Shouzhong , Ou Yang Liang Yueh , Josell Daniel , Richter Lee , Moffat Thomas P.
Published: February 2020

State of the art manufacturing of semiconductor devices involves electrodeposition of copper for device wiring and chip stacking. The success of the electroplating process depends on electrolyte additives that affect the local deposition rate to yield void-free superconformal, or bottom–up filling of trenches and vias that comprise 3D interconnects. Quantitative chemical process models have been shown to be effective in describing the filling of high aspect ratio features that range from nanometers to millimeters in scale. Nevertheless, much remains to be known about the molecular nature of the additives and the competitive, co-adsorption dynamics involved in both suppression and acceleration of metal deposition. Accordingly, a variety of surface science tools, such as STM and SEIRAS, are being used to investigate additive function. These studies point to controlling interface hydrophilicity as a key principle in the design and operation of additives used for superconformal film growth.
Observation of Additive Behavior in Copper Electroplating Using Microfluidic Device
Authors: Tomie Mineyoshi , Akita Takanori , Ikuta Ryo , Hayase Masanori
Published: February 2020

Nowadays, high performance of integrated circuits is owing three-dimensional packaging technologies and TSV (through silicon via) came into use in commercial products. TSV is formed by bottom-up filling of conductor in the deep hole and copper electroplating with several additives is usually employed for the filling. However, many trial-and-error processes are needed to obtain optimal recipe for the filling and understanding of the bottom-up filling is not satisfying yet.

Suppression behavior of additive is considered as an essential factor for the bottom-up filling, but critical suppression behavior is not well observed by conventional electrochemical measurements. Desorption of suppressing additive from plating surface seems to have important role, because suppression breakdown occurs from the TSV bottoms where the additive supply is most limited. In this study, we made a microfluidic device to realize precise mass transport and quick switching of plating solutions, and in-situ observation of plating surface was performed. Figure 1 shows a result with a commercial leveler. Initially, VMS (virgin make-up solution) with no additive was supplied into the micro channel, and copper plating was performed on Pt working electrode with 100μm in diameter for 5 s. Then, the solution containing leveler was supplied for 10 s. Finally, the solution was switched to VMS again and additive desorption was monitored. With small overpotential (-550 mV vs. MSE), plating surface was covered by the leveler and strong suppression was observed. After the plating solution was switched to VMS with no additives, localized depositions were observed all over the plating surface. While with large overpotential (-600 mV vs. MSE), strong suppression was observed only on up-stream region of the plating surface where bright smooth surface was kept during the leveler supply. After the solution change, suppression breakdown with localized depositions were observed gradually from the lower-stream region. Identical experimental procedure was applied to several additives and the behaviors were compared.

Figure 1
Selective Metalization of Non-Conductive Materials By Macropatterning of Catalytic Particles and the Application of a Gradient Magnetic Field
Authors: Danilova Sofya , Graves John Edward , Pellicer Eva , Sort Jordi , Cobley Andrew J
Published: February 2020

Photolithography is commonly used in various manufacturing sectors to achieve metal patterning of non-conductive materials. However, the high cost and toxicity of reagents used in this process have prompted the investigation of alternative approaches to selective metallisation. The present work shows a novel approach that utilizes a gradient magnetic field to achieve selective metallization on the millimeter scale. The magnetic field is applied during the seeding (catalysation) stage, which is required to initiate electroless copper deposition. Subsequent copper deposition occurs selectively according to the pre-defined pattern of the magnetic field.

The modified approach uses a new type of magnetic catalyst i.e. a Fe­3O4-Ag composite material, which was obtained by a wet chemical synthesis method. The Fe component of these particles enables them to be arranged on the substrate in a way that directly corresponds to the pattern of the magnetic field and therefore subsequent electroless copper plating will follow this pattern. The magnetic and catalytic properties of particles for the initiation of electroless copper deposition were characterised by vibrating sample magnetometry and cyclic voltammetry measurements. The Fe3O4-Ag composite colloid solution was optimized by varying the pH, mixing approach and particle concentration.

This paper will demonstrate the potential for selective catalysation in a magnetic field to compete with the commonly used photolithography and ink-jet printing approaches for macroscale selective metallisation of non-conductive materials.

Figure 1. The schematic representation of standard electroless copper plating process and modified process of selective metalization in a gradient magnetic field.

Figure 1
(Invited) Point-of-Care Based System Development for Urolithiasis Recurrence Prevention
Authors: Chung Wen-Yaw , Heythem Salhi , Silverio Angelito , Tsai Vincent , Cheng Cheanyeh , Wu Guan-Wei , Chang Syuan-kai , Yen Lin-Chen , Yang Chia Ming , Lo I-Wen , Chang Shu-Yu
Published: February 2020

Point-of-care (POC) based system becomes more important for aging society and modern life. In Taiwan or globally, most of patients who have a history of urinary stone, the chance of recurrence is about 70 – 80% within 7 years. So, the cost of urinary stone treatment consumes a significant percent of health care insurance. A platform for measuring key parameters of morning spot urine (random urine) to predict the onset of urolithiasis was implemented in this study. This research presents a POC test system developed for urolithiasis recurrence prevention. The system can be used to assist a patient in assessing the condition of his urinary system through urine quality indicators pH, Ca2+, uric acid, conductivity, color and crystallization, etc. Several major types of sensors were used to monitor core parameters in human’s urine. Ion Sensitive Field Effect Transistor and Extended Gate Field Effect Transistor potentiometric-type sensors are used for pH and Ca2+ monitoring, the enzyme based two or three-electrode amperometric type sensor is used for urine’s uric acid sensing, and the self-developed electrodes are used for conductivity measuring. The wireless based prototype with these sensors and CMOS readout circuits were integrated and tested in the laboratory and clinically. In this research, the integrated circuit designs for sub-sensing system implementation were fabricated through TSMC 0.35um and 0.18um CMOS processes. The test results on key parameters monitored by the proposed prototype and fabricated integrated circuits show an acceptable and promising performance referred to corresponding commercial meters for individual parameter sensing. In addition, the prototype system with blue tooth transceiver was developed for wireless communication. Through the data analysis and risk assessment made by urologists, this system can provide a regular urine quality monitoring to patients with urinary stone, the eating and life styles can be consulted or adjusted according to the data base collected from the proposed system and patient individually. The development of this POCT platform will be also useful for improving the life quality of patient with urolithiasis, extending applications in aging societies and reducing an unnecessary cost of health care insurance.

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Ultra-High Sensitivity for Lead Ion Detection Beyond the Ideal Nernst Response with AlGaN/GaN High Electron Mobility Transistors (HEMTs)
Authors: Hsieh Ching-Yen , Chen Yi-Ting , Sukesan Revathi , Wang Yu-Lin
Published: February 2020

Lead is one among the most hazardous heavy metals. Heavy metal cannot be metabolized or digested by human body, therefore, heavy metal accumulates in our body through time. Lead in human body damages the nervous system, impairs vision, hearing and even cause joint and muscle pain. Mostly lead ions get in to human body by ingestion, so detecting lead ion in drinking water, tap water and liquid form of food is very important. However, traditional laboratory detection methods of lead ion are complex and time consuming and requires heavy and expensive machinery. Though the electrochemical ion selective electrode is easy to use, its poor stability and larger detection limit are huge disadvantages. In this research, we devised a small size, highly sensitive, low detection limit, short response time and easy to fabricate lead ion selective high electron mobility transistors (ISHEMT). This device is easy to use and can measure the lead concentration in water quickly with the combination of ion-selective membrane and AlGaN/GaN HEMT. The sensing mechanism depends on electrical double layer (EDL) gating coupled with high electric field to enhance the sensitivity of ISHEMT beyond the limit of ideal Nernst sensitivity. World Health Orgnization (WHO) suggests that lead ion in drinking water should be lower than 10ppb, equal to 4.8310-8 M. This device can detect lead ion concentration form 10-5 M to 10-10 M, covering the wide dynamic range according to WHO’s suggestion and even higher sensitivity can be achieved by optimizing sensor design. Such high sensitivity and low detection limits are highly desirable for consumers who intend to regularly monitor the water quality, for food and environmental safety. In contrast, testing lead ion in water by ICP-MS takes several hours and the instrument occupies larger space. With this lead ISHEMT, we can determine the lead concentration in water in 10 minutes and even get better sensitivity and lower detection limit, in comparison with conventional laboratory based techniques. Not only lead, but also other heavy metals, for example mercury and cadmium, can use similar methodology to get better sensitivity and detection limit. This design makes quality monitoring of water we consume in daily life become much easier and convenient.

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Preparation and Biological Applications of Naphthalimide Benzothiazole As DNA-Targeted Anticancer Agents
Authors: Li Xiaolian , Chen Xuehui
Published: February 2020

Cancer is a major extensive health problem which is the second leading cause of mortality in developed countries and most frightening disease in humans. DNA, as the carriers of genetic information of the living body, is not only the basis of biological growth, development, reproduction and other important life activities, but also closely related with tumor, viral infection and genetic diseases. The DNA is becoming one of the most promising biological targets of developing antitumor agents to constrain tumor cell growth.

The structure of precursor 1,8-naphthalimide was used as parent compound, and the triazole pharmacophore and benzothiazole was linked to naphthalene at 4 site by Click reaction. Based on this, we synthesized a series of novel “non-fused” naphthalimide derivatives first. Their structures were proved by TOF MS and 1HNMR. Then we used UV-vis spectra, Fluorescence spectra, CD spectra and viscosity assay to discuss their action modes on DNA. Finally we employed MTT assay to further evaluate their antitumor activities.

The UV-vis spectra, fluorescence spectra, CD spectra and viscosity assay showed that the compounds could intercalate into DNA. The changes of UV-Vis spectra and enhancement of fluorescence intensity proved that the compounds could intercalate into the DNA effectively. CD spectra results indicated that M3 could turn the conformation of DNA from B to A-like, M4 could change the B-DNA to C-DNA, and M5, M6 stabilized the B-DNA. According to the bioactivities assays, the compounds exhibited efficient toxicity against tumor cells in vitro, in particular M3 and M4, whose IC50 values against MCF-7 cells and Hela cells were 0.35μM, 0.12 μM and 0.66 μM, 0.19 μM, respectively. Moreover, both of them had better selectivity against MCF-7 cells and Hela cells than 7721 cells. When two nitrogen atoms of the side chain of the compounds separated by two carbon atoms, it showed significant inhibitory activity, such as M1, whose IC50 values against MCF-7 cells, Hela cells and 7721 cells were 2.33 μM, 0.35 μM and 0.49 μM, respectively.Fig. 1 CD spectra of naphthalimide derivatives

Introducing various flexible side chains amine has great impact on biological activities of naphthalimide derivatives. It has vast importance to expand and develop new and efficient antitumor drugs of naphthalimide. It’s an effective way to improve the efficacy of antitumor activity by introducing the structure of triazole and benzothiazole to naphthalimide in the para position.

Acknowledgements

We are grateful to the National Natural Science Foundation of China (21576043), supported by “the Fundamental Research Funds for the Central Universities”.

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(Invited) Imperceptible Graphene Based Electronic Tattoo Sensors
Authors: Kabiri Ameri Shideh , Lu Nanshu , Akinwande Deji
Published: February 2020

During last decade, there have been advances in wearables with applications in mobile healthcare, athletic, assistive technology, human machine interface and internet of things. However, current wearable sensors and systems have at least one or more of the following drawbacks: they are bulky, expensive, distractive, unsuitable for long term measurement or prone to motion artifact.

We present ultrathin graphene based electronic tattoo (GET) sensors with the overall thickness of less than 500 nm. Presented e-tattoo sensors can be laminated on skin like as temporary tattoo and form conformal contact to microscopic texture of the skin. GET is a set of dry sensors with electrode-skin interface impedance comparable to wet gel electrodes that are gold standard in medical applications. Low electrode-skin interface impedance of these e-tattoo sensors results in high signal to noise ratio and high sensing quality. Due to low areal mass density of GET, it attaches to skin without any adhesive or tape, just by Van der Waals force. Presented e-tattoos are both optically and mechanically imperceptible, therefore, they are desirable for applications in prominent areas of appearance such as face. We present the successful demonstration of GET applications for electrocardiography (EEG), electroencephalography (EEG), electromyography (EMG), electrooculography (EOG), skin temperature sensing, skin hydration sensing and human robot interface.
MgTFSI2/MgCl2 /DME Solution Structure Analysis
Authors: Salama Michael , Shterenberg Ivgeni , Gofer Yosef , Aurbach Doron
Published: February 2020

Recently, MgTFSI2/MgCl2 electrolyte solutions in dimethoxyethane (DME) have been shown to function as viable electrolyte solutions for secondary Mg batteries that can facilitate reversible magnesium deposition/dissolution1. MgCl2 is a crucial component in these solutions. On its own, however, it is practically insoluble in DME. Therefore, the fact that it is readily dissolved in MgTFSI2/DME solution is remarkable. Addition of MgCl2 greatly improves the electrochemical performance of MgTFSI2/DME electrolyte solutions. MgTFSI2 /DME electrolyte show large overpotential for deposition (-0.6 V vs Mg) and dissolution (1.5V vs Mg). Furthermore this electrolyte exhibit poor magnesium deposition reversibility. Adding MgCl2 to this electrolyte reduces the overpotentials for both deposition and dissolution and showed 98% columbic efficiency. Thus, identifying the species formed in MgTFSI2/MgCl2 solutions are very intriguing. In this study, we identified numerus solution species that some of them were not previously identified. We believe that the newly discovered MgxCly complexes play a crucial rule in the improved electrochemical performance of the MgTFSI2 /DME electrolyte solutions. The complexes that were identified were Mg3Cl4
2+
(figure 1)2, Mg2Cl2
2+.Furthermore we showed that the hexacoordinated nature of magnesium effectively dictate the solution structure. We showed that in THF based electrolyte Mg2Cl3
+ is the dominant solution specie and we didn’t see any evidence for its existence in DME based electrolytes(. We implemented a wide variety of analytical tools, including single crystal X-ray diffraction, multinuclear NMR, and Raman spectroscopy, to elucidate the structure of these solutions. Various solution species were determined, and a suitable reaction scheme is suggested(figure 1). We believe that this type of fundamental study is essential for designing new and improved electrolyte solutions for secondary magnesium batteries.

Shterenberg, I.; Salama, M.; Yoo, H. D.; Gofer, Y.; Park, J.-B.; Sun, Y.-K.; Aurbach, D. Evaluation of (CF3SO2) 2N−(TFSI) based electrolyte solutions for Mg batteries. J. Electrochem. Soc.
2015, 162, A7118-A7128.

Salama, M.; Shterenberg, I.; JW Shimon, L.; Keinan-Adamsky, K.; Afri, M.; Gofer, Y.; Aurbach, D. Structural Analysis of Magnesium-Chloride Complexes in Dimethoxyethane Solutions in the Context of Mg Batteries Research. The Journal of Physical Chemistry C
2017.

Figure 1