bluuebunny/crossref_metadata_2025 huggingface dataset:
Modeling and Characterization of Tissue/Electrode Interface in Capacitive µECoG Glassy Carbon Electrodes
Authors: Goshi Noah , Vomero Maria , Dryg Ian , Seidman Scott , Kassegne Sam
Published: February 2020

Understanding the chronic immune response to implanted neural electrodes is important from both a patient safety and long-term device functionality standpoint.  In this investigation, we focused on examining the effects of the chronic immune response on the long-term functionality of µECoG surface electrodes implanted under the dura matter of in vivo rat models over a period of six weeks.  We characterized the abio-bio interface of the explanted devices, and compared the biological layer adhered to capacitive (glassy carbon) electrodes to that of faradaic (Pt) electrodes.  In addition, in vitro electrical conductivity tests of the explanted devices were performed, and the results were compared to both previously recorded pre-implant and in vivo conductivity data.  Subsequently, the overall corrosion of the capacitive and faradaic electrodes were compared.  Because both electrode types were coated in the same insulating material (polyimide) formed in the same geometry, the differences in the chronic immune response to the implanted devices can be attributed to the presence of either capacitive or faradaic electrodes.  Further, we support the experimental observation with finite element modeling of the electrode/tissue interface where electric field, Nernst-Planck diffusion of charges, double layer capacitance, and pH distribution are evaluated qualitatively and quantitatively and correlated with experimental results.
Biosensing and Photoinactivation of S.Typhi in Water with ZnO-Rgo Hybridphotocatalysts
Authors: Abd Hamid Sharifah Bee , Lee pui Kee , Teh swee Jyan , Thong kwai Lin
Published: February 2020

Nanostructured metal oxides, especially zinc oxide, ZnO had attracted great attention for the construction of biosensor due to its high isoelectric point (IEC). This high IEP of ZnO made it a good material for immobilisation of DNA through electrostatic interaction. On the other hand, the good conductivity, large surface area and biocompatibility have made carbon based materials such as reduced graphene oxide, rGO  suitable candidate for electrochemical biosensor. In addition, rGO is an unique materials which has the ability to accept the electrons from the photocatalyst, ZnO and to slow down the recombination rate of electron-hole of ZnO. The limitation of ZnO as photocatalyts can be overcomed by forming hybrid with rGO. Thus, we used the rGO-ZnO thin film  for biosensing and as photocatalyst for photoinactivation for bacteria in water. In this paper, reduced graphene oxide (rGO) was utilised to form hybrid with zinc oxide (ZnO) by electrodeposition. This rGO-ZnO thin film electrode acted as a hybrid-platform both for electrochemical and photoelectrochemical biosensor for the detection of S.Typhi in water. After biosensing, the same rGO-ZnO thin film, as photocatalyts too, was used to accelerate the sunlight-mediated inactivation of S.Typhi in the water sample.

Acknowledgement

This research is supported by University Malaya Flagship Grant project FL001A-14AET, and Transdisciplinary Research Grant Scheme (TRGS TR002A-2014) from Malaysian Ministry of Higher Education.
High-Resolution Studies of Crevice Corrosion of Nickel and Aluminum with Real Time Multiple Beam Interferometry and Microscopy
Authors: Merola Claudia , Shrestha Buddha Ratna , Valtiner Markus
Published: February 2020

Crevice corrosion (CC) of engineering metals remains a serious concern for structural materials. Yet combining both, a real-time and high-resolution in-situ visualization of corrosion within confined geometries remains very challenging. In this contribution, we will discuss how multiple-beam interferometry (MBI) and simultaneous microscopy can be utilized to directly visualize corrosion processes in real-time and with Ångstrom resolution within well-defined confinement geometries. Here we will directly compare results of accelerated corrosion tests of confined Aluminum and Nickel surfaces in a modified surface forces apparatus1.

With MBI, we can detect and track active sites of aluminum corrosion in NaCl solution within confined geometries in real time. We find that CC of aluminum randomly initiates in the confined crevice mouth, where the distance between apposing surfaces is between 20-300 nm. We can directly track oxide dissolution/formation, and corrosion-rates as well as their retardation due to sodium vanadate inhibitors present in solution. Formation of a compacted oxide layer effectively inhibits CC in 5 mM NaCl solutions with 2.5 mM of added NaVO3, while inhibition rapidly breaks down at chloride concentrations above 50 mM. Breakdown of the inhibition-layers is initiated by rapid dissolution of the protective oxide within the confined zone.

Interestingly, Nickel CC shows distinctly different and unexpected corrosion mechanism depending on the NaCl concentration. We find that low Chloride concentration lead to “preferential pitting corrosion” inside of confined zones, while high Chloride concentrations lead to “crevice corrosion in the crevice mouth”. We will discuss these surprising results and we will show real time high-resolution videos of CC in confined geometries that detail this behavior.

Literature

1.      Shrestha, B. R.; Hu, Q.; Baimpos, T.; Kristiansen, K.; Israelachvili, J. N.; Valtiner, M., Real-Time Monitoring of Aluminum Crevice Corrosion and Its Inhibition by Vanadates with Multiple Beam Interferometry in a Surface Forces Apparatus. Journal of the Electrochemical Society 162 2015, C327-C332
Corrosion and Surface Modification of Ti-6Al-4V Implant Alloy Under Various Simulated Biological Environments
Authors: Virtanen Sannakaisa
Published: February 2020

Ti and its alloys, for instance Ti-6Al-4V, are generally considered as highly corrosion resistant, due to the very stable passivity. These materials are widely used in biomedical applications for permanent implants, and they have an excellent reputation for biocompatibility. Some problems related to the chemical stability of Ti-based implants exist in the practical application, mainly due to the conjoint action of chemical and mechanical attack, i.e. fretting corrosion. This can lead to release and accumulation of Ti in tissue adjacent to titanium implants. However, it is also known that depassivation of Ti can take place under deaerated acidic conditions. Even though the typical chemistry in a "bulk" biological environment is pH-neutral (buffered to pH 7.4), under certain conditions, for instance in crevices, much more aggressive environments can be present. Local acidification is possible not only due to metal cation hydrolysis reactions, but in addition by possible inflammation reactions (such as following a surgery). Inflammation conditions also lead to presence of H2O2 in the surrounding. This is noteworthy in view of corrosion of Ti alloys, as H2O2 is known to complex Ti cations and hence acceleration of dissolution in possible.

This presentation will discuss dissolution of the Ti-6Al-4V implant alloy under different simulated biological environments, including simulation of inflammation conditions (pH decrease, presence of H2O2). Electrochemical measurements and metal release indicate drastically increased dissolution rates under simulated inflammation conditions. In addition, selective phase etching is observed. Various surface modification treatments for improved performance are being explored, such as anodization or TiO2 nanoparticle coating. In addition to corrosion studies, bioactivity of the surfaces in view of Ca-phosphate precipitation is being investigated.
Effects of Reclaimed Water Blending on the Pipe Corrosion in an Irrigation System
Authors: Woo Dalsik , Shin Taesub , Lee Jaekyeong , Shin Sunghoon , Lee Haksoo
Published: February 2020

Global climate change is a change in the statistical distribution of weather patterns when that change lasts for an extended period of time. Nowadays, this change has been affect to water source shortage. Usage of reclaimed water is one of the most important solutions for this problem. There are a lot of methodologies for using reclaimed water instead of fresh water. Especially, agriculture field uses a lot of water to grow crops. Many countries water usage amount in agriculture is to 40~60% of their total water capacity. Therefore, usage of reclaimed water is one of solutions for supplement water shortage. There are several efforts to saving and improving water usage in agricultural field.

In pipeline irrigation system, pipes were made of metallic or non-metallic materials. Depending on the case, the metallic pipes are used for following; large diameter, high pressure or loading. Because of the corrosion problem of metallic pipes by water, non-metallic pipes also used if there is concern about corrosion. There are various techniques in order to prevent corrosion. In these methods, sacrificial anode method and pipe lining are useful method for irrigation pipeline. For the effective application of corrosion prevention for usage of reclaimed water, it is necessary that the evaluation of corrosion pipes with various type of water blending (reclaimed water, surface water, etc.).

In this study, we evaluated about corrosion index for blending effect of surface water and reclaimed water in metallic pipeline. Based on blending ratio, pH, alkalinity, conductivity, hardness, nitrate, nitrite, phosphate, ammonium were measured and evaluated in batch reactor. Based on this research, it is expected that the usage of this data can be useful for usage of various type of water in agriculture field and many engineers related corrosion field can apply this data for their works.

Acknowledgement

This research was supported by a grant (12-TI-C01) from Advanced Water Management Research Program funded by Ministry of Land, Infrastructure and Transport of Korean government
The Effect of Plasma Electrolytic Oxidation Parameters on Coating Morphology and Corrosion Behavior
Authors: Cengiz Sezgin , Uzunoglu Aytekin , Tarakci Mehmet , Gencer Yucel , Stanciu Lia
Published: February 2020

Zirconium (Zr) and Zr-based materials have been widely used in biomedical and dental applications. Although these materials have better chemical and mechanical properties compared to titanium-based implants for biomedical applications, their poor bioactivity is still a challenge that needs to be overcome in order to increase the cell attachment properties [1-3]. In this study, the surface of Zr substrates was modified by plasma electrolytic oxidation (PEO) to induce a significant changing the surface chemistry and topology and thus increase bioactivity. The PEO processes were conducted at different current frequencies ranging from 80 to 420 Hz in a 30 g/l calcium acetate monohydrate (CA), 8 g/l β-glycerophosphate disodium salt pentahydrate (β-GP) and 2 g/l KOH containing electrolyte solution. The phase and chemical composition, as well as the morphology of the coatings were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), and optical surface profilometry (OSP) techniques. The corrosion performance of the fabricated coatings, which is also crucial for biomedical applications, were evaluated. The results revealed that the current frequency had a profound influence on the microstructure and the chemical composition of the fabricated coatings. The SEM and OSP experiments revealed that the increase in the current frequency resulted in rougher surface coatings with bigger pores. The corrosion behaviour of each samples conducted in simulated body fluid (SBF) at the temperature of 36.5 °C will be presented.

References

1-    V. Sollazzo, F. Pezzetti, A. Scarano, A. Piattelli, C.A. Bignozzi, L. Massari, G. Brunelli, F. Carinci, Zirconium oxide coating improves implant osseointegration in vivo, Dent Mater, 24 (2008) 357-361.

2-    P. Thomsen, C. Larsson, L.E. Ericson, L. Sennerby, J. Lausmaa, B. Kasemo, Structure of the interface between rabbit cortical bone and implants of gold, zirconium and titanium, J Mater Sci-Mater M, 8 (1997) 653-665.

3-    Y.Y. Yan, Y. Han, Structure and bioactivity of micro-arc oxidized zirconia films, Surf Coat Tech, 201 (2007) 5692-5695.
Corrosion Behavior of Austenitic Stainless Steel in Supercritical CO2 Containing O2 and H2o
Authors: Teeter Lucas , Huerta Nicolas , Dogan Omer , Ziomek-Moroz Margaret , Oleksak Richard , Oryshchyn Danylo
Published: February 2020

The corrosion behavior of 347H stainless steel was investigated in supercritical CO2 (sCO2) containing H2O and O2 to simulate heat exchanger conditions that would exist in direct sCO2 power cycles.  To understand the thermodynamic properties of oxygenated sCO2 aqueous systems related to the corrosion phenomena, thermodynamic modeling was performed using REFPROP software.  Samples were exposed to oxygenated water-containing CO2, and oxygenated CO2-containing H2O. The exposure tests were carried out at a pressure of 80 bar and two temperatures, 50 °C and 248 °C. The environmental conditions were simulated by filling each 1100 ml autoclave with 400 ml of deionized water, bringing each autoclave to its respective test temperature, and then pressurizing it with a CO2:O2mixture having a molar ratio of 95:1.

The corrosion rate of each sample was determined by mass loss measurements. The surface morphology and the composition of the corrosion product layers were analyzed using surface analysis techniques including X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), wavelength dispersive spectroscopy (WDS) for oxygen and chromium, and X-ray photoelectron spectroscopy (XPS).  Weight gain results reveal that the samples exposed to higher temperatures experience a significant increase in oxide growth compared to the lower temperature counterparts.  XRD results confirmed this result in that corrosion products present on the samples exposed to sCO2 containing H2O and O2 and H2O containing sCO2 and O2 at 50 °C were too thin for conventional Bragg-Brentano XRD to detect anything aside from the base material.  However, the samples exposed to the environments at 248 °C had sufficiently thick corrosion layers for this method.  The XRD results for the corrosion products on the sample surfaces formed in the oxygenated CO2-containing H2O and water-containing CO2 environments at 248 °C revealed the presence of primarily hematite (Fe2O3) and magnetite (Fe3O4), respectively. These results indicate that the corrosion degradation mechanism for 347H in oxygenated H2O containing sCO2 is different from the mechanism in oxygenated sCO2 containing H2O at 248 °C.
Investigation, Modeling and Design of a Cathodic Protection System for Hull Structures in Marine Environment
Authors: Aksu Rauf , Uguz Refik Onur , Erdogan Metehan , Meco Halim , Karakaya Ishak
Published: February 2020

Corrosion is a form of material deterioration process due to chemical interactions with surrounding environment. Metals must be isolated or protected to avoid corrosion. Metallic components of amphibious vehicles are exposed to aggressive conditions during their service lives. These components are coated with organic substances to isolate metal surface from corrosive species. Occasionally, protective layer on metallic components fails due to poor adhesion, chalking, peeling and delamination. Damaged areas on coated components may become exposed to seawater. Cathodic protection is an effective method to inhibit corrosion of metallic components of amphibious vehicles which are in direct contact with seawater.

Selected steel types and aluminum alloys [1], which are used in manufacturing the hulls of armored amphibious vehicles, were subjected to accelerated corrosion tests in synthetic seawater to collect data for simulation of cathodic protection. Typical Nyquist and Tafel plots are shown in Figure 1. COMSOL Multiphysics modeling software [2] was used to integrate electrochemical data obtained by both impedance spectroscopy and potentiostatic tests to simulate cathodic protection of the vehicle hulls under seawater. Potential and current density distributions in marine environment were evaluated to design the cathodic protection system that could impress the currents. The size, shape and locations of sacrificial anodes were optimized to enhance homogenous protection performance.

[1] National Research Council (U.S.). (2013). Materials for Lightweight Military Combat Vehicles: Report, Nabu Press

[2] COMSOL Multiphysics 5.1, Corrosion and Electrochemistry Modules

Figure 1
Degradation of Ir-Ta Oxide Coated Ti Anodes in Sulfuric Acid Solutions
Authors: Ma Dongni , Ngo Vanda , Raghavan Srini
Published: February 2020

Conductive ceramic oxides based onIr and Ta are commonly used in the fabrication of dimensionally stable anodes for many electrochemical systems requiring high chemical stability and electrocatalytic activity in aggressive environments. In this paper, the degradation of IrO2-Ta2O5 (35.6 wt%  Ir and 26.3 wt% Ta ) coated titanium mesh anodes in 2 M sulfuric acid solutions will be discussed. The Ir-Ta oxide coated electrodes were prepared by brush coating Ti mesh samples with an organic solvent system containing H2IrCl6 and TaCl5followed by firing at approximately 450 deg. C. The thickness of the oxide coating was ~ 4.8 to 6.9 microns.

The electrochemical properties of the prepared electrodes were studied by performing galvanostatic accelerated life tests and anodic polarization. The accelerated life test consisted of subjecting the sample to a current density in the range of 0.54 to 1 A/cm2 in 2 M sulfuric acid solution in a customized flow through cell with a titanium mesh cathode for a period lasting over five hundred hours. The degradation of the coating was followed by monitoring the cell potential. A PARSTAT 2273 Potentiostat system equipped with a PowerSuite®software was used for these experiments. The acid concentration was maintained at 2M by adding the required amount of water to compensate for the decomposition of water to oxygen at the anode. The lifetime test was interrupted periodically to conduct anodic polarization experiments and determine changes in the potential for oxygen evolution. The morphology and chemical composition of the coatings at different stages of the accelerated life test were characterized by SEM and energy dispersive X-ray spectroscopy (EDS).

The as-prepared sample had numerous cracks and displayed amorphous and crystalline features. Localized thinning as well as complete removal of the oxide coating were evident in samples subjected to accelerated life testing (see Figure). EDS analysis indicated selective removal of IrO2 from the oxide coating. The presentation will discuss the results of the electrochemical and morphological investigations and propose a degradation mechanism for the Ir-Ta oxide coating in acidic environment.

Figure 1
The Utilization of Hydrophobic Coatings on Insulative Skirts to Galvanically Decouple Mechanically-Fastened Aluminum Alloy and Carbon-Fiber Reinforced Polymer-Matrix Composites
Authors: Srinivasan Raghu , Hihara Lloyd H.
Published: February 2020

In a quest to reduce weight and improve performance, aluminum (Al) alloys have been used in conjunction with lightweight materials such as carbon-fiber reinforced (CFR) polymer-matrix composites (PMCs). The mechanical contact of CFR PMCs (which serves as cathode) with Al alloys (which serves as anode) can result in galvanic corrosion of the Al alloys in a corrosive environment. The major objective of this research was on devising corrosion control strategies for couples of 6061-T6 Al that were mechanically fastened to CFR PMCs using Ti-6Al-4V bolts.

A typical method used to mitigate galvanic corrosion when bolting Al to CFR PMCs is to insert an insulating layer (G-10 fiberglass or E-glass–reinforced PMC) between the members. Although the direct contact between the aluminum and CFR PMC is eliminated, the aluminum and the CFR PMC are still galvanically coupled through the Ti fastener, and galvanic corrosion on Al will occur if the electrolyte bridges over the insulating layer. Galvanic corrosion can be mitigated by increasing the IR loss across the skirt, which can be achieved by lengthening the skirt or breaking up the continuity of the salt bridge that forms on the skirt.  The continuity of the salt bridge can be disrupted by applying hydrophobic coatings on the insulative skirt.

In this study, galvanic corrosion rates were monitored for 6061-T6 Al—CFR PMC couples (with insulating skirts) subjected to the following conditions:

1) Insulting skirts having coatings (silane-based coating, epoxy, polyurethane, or latex) of various levels of hydrophobicity

2) Salt solutions of various concentrations (0, 10, 100, 1000, 10000, and 20000 ppm of chlorides)

3) Various insulating skirt lengths (0.25 inch or 0.5 inch),

4) Various exposure conditions (controlled humidity laboratory exposure, outdoor exposure with sheltered and unsheltered conditions).

The effect on galvanic corrosion by the different coatings was studied as a function of hydrophobicity, as determined by the contact angle for wetting. The contact angle was measured on the coating surface before and after exposure to the outdoor test sites to study the effects of environmental degradation on hydrophobicity. The degradation of the coatings was also studied using other techniques such as Raman spectroscopy. The ingress of environmental constituents (i.e., chlorides, sodium ions, etc.,) towards the anode and cathode surfaces was analyzed using scanning electron microscopy (SEM) and energy dispersive-X-ray analysis (EDXA).
(Invited) High-k Materials and Embedded Nanocrystals for Electronic and Photonic Applications
Authors: Heitmann J.
Published: February 2020

High-k materials play a major role in semiconductor research and development. Semiconductor industry made a step towards high-k dielectrics like Al2O3, HfO2 and ZrO2 for MIM capacitors in DRAM and rf applications [1], as well as for gate dielectrics for sub 45 nm devices or in high electron mobility transistor in GaN based hetero structures. Implementing high-K materials into the process flow of a GaN based high electron mobility transistor needs to adapt the whole process sequence, like thermal budget of electrode formation etc. [2]. Furthermore, in solar industry the high-k material Al2O3 is discussed to replace SiN passivation layer for the newest PERC concept [3,4].

Beyond the already established applications routes high-k materials show superior properties as matrix material for semiconductor quantum dots – rare earth element alloys to enhance their optical and electrical properties. Embedded group IV nanocrystals like Si and Ge show superior charge storage properties in high-K matrix materials deposited via rf-magnetron sputtering. Ge nanocrystals embedded in an amorphous TaZrOx matrix as blocking oxide implemented in a metal-insulator-semiconductor capacitor show a voltage hysteresis in a capacitance-voltage slope of 5 V and a programming voltage – hysteresis voltage slope of nearly 1 [5]. In case of embedded Au nanoparticles in sol gel deposited Er doped ZrO2 films a temperature stability of the Au nanoparticle related surface plasmon resonance up to 1000°C annealing temperature could be shown [6].

In this contribution we will review our efforts to realize optimized properties of the high-K materials for the needs of the different applications as matrix material for nanocrystalline semiconductors for optical and electrical applications and as passivation layer for Si photovoltaics or nitride electronics.

[1] J. Heitmann, A. Avellan, T. Boescke, E. Erben, B. Hintze, S. Jakschik, S. Kudelka, and U. Schroeder, HfAlO and HfSiO Based Dielectrics for Future DRAM Application, ECS. Trans. 2 (2006) 217.

[2] Schmid, A.; Schröter, Ch.; Otto, R.; Schuster, M.; Klemm, V.; Rafaja, D.; Heitmann, J., Appl. Phys. Lett. 106, 053509 (2015)

[3] Benick et al. Applied Physics Letters 2008; 92; 253504

[4] F. Kersten, A. Schmid, S. Bordihn, J. W. Müller, J. Heitmann, Energy Procedia, 38, p. 843, (2013)

[5] D. Lehninger, P. Seidel, M. Geyer, F. Schneider, V. Klemm, D. Rafaja, J. von Borany, J. Heitmann, Appl. Phys. Lett. 106, 023116 (2015)

[6] S. Seidel, A. Sabelfeld, R. Strohmeyer, G. Schreiber, V. Klemm, D. Rafaja, Y. Joseph, and J. Heitmann, J. of Appl. Phys., submitted for publication.
Effect of Cu Drift on Dielectric Breakdown for Porous Low Dielectric Constant Film under Static and Dynamic Stress
Authors: Cheng Yi-Lung , Huang Yao-Liang , Sun Chung-Ren , Lee Wen-Hsi , Chen Giin-Shan , Fang Jau-Shiung
Published: February 2020

Cu-ion-migration-induced the porous low-k dielectric breakdown was studied in alternating polarity-bias conditions using a metal–insulator–metal (MIM) structure with Cu as a top electrode. The experimental results indicated that Cu ions migrate into a dielectric film under a positive polarity stress, leading to a shorter time to failure (TTF). Additionally, the TTF obtained in the alternating-polarity test increased with decreasing the stressing frequency, indicating that the backward migration of Cu ions during the reverse-bias stress. Meanwhile, this Cu backward migration effect is effective as the stressing time of a negative polarity stress is larger than 0.1 s. When the frequency is decreased to 10-2 Hz, the measured TTFs were higher as compared to a direct-current (DC) stress condition. Finally, the electric-field acceleration factor of porous low-k dielectric breakdown became larger under  Cu-ion-migration case.
(Invited) Combined Gas Cluster Ion Beam (GCIB) and Chemical-Mechanical Planarization (CMP) Process for Replacement Metal Gate (RMG) Application
Authors: Tseng Wei-Tsu , Long Justin , Mohan Kaushik , Wu Changhong , Kagalwala Taher
Published: February 2020

The introduction of high-k metal gate (HK/MG) stack has enabled the resumption of Moore’s Law at the 45/32nm nodes, when the conventional Poly/SiON gate stacks failed to meet the required scaled-down performance targets. Despite the well demonstrated benefits such as reduced gate leakage, HK/MG integration scheme itself brings about new challenges in Si-based semiconductor process technologies. Among them, the most critical and stringent step is RMG CMP, which is tasked to deliver gate height uniformity within the range of a few nanometers on all chips across the entire 300mm wafer for 14nm technology nodes and beyond.

Conventional approaches to CMP planarity and uniformity often include the optimization of carrier zone pressure, platen/carrier rotation, slurry flow, conditioning sweep profileetc. Advances in CMP equipment technologies have also enabled new possibility such as multi-zone carrier pressure control through APC for within-wafer non-uniformity (WiWNU) reduction. Another widely-adopted approach is to rely on the high-selectivity of slurries to “stop dead” on the final layer of interests (e.g., tungsten in the case of RMG) without creating excessive local topography due to oxide erosion. While all the above approaches prove effective to certain degree, they are, by nature, wafer-level to sub wafer-level processes. As a consequence, it is difficult for them to differentiate between dies locally, for example, and correct the non-uniformity accordingly to the range of a few nanometers.

In this contribution, an alternative planarization scheme for RMG is presented to enable nano-scale gate height uniformity control across all dies on 300mm wafers. The new scheme begins with conventional high-selectivity CMP process (pass-1 W-CMP) to remove overburden and polish the gate height down to a few nanometers thicker than the final target, followed by all-die gate height measurement on all wafers. Then the gate height data are fed forward to a GCIB tool, where location-specific process (LSP) takes place to trim the oxide down to a pre-determined target, die by die, through high-energy raster ion beam with high oxide-to-tungsten selectivity. This is followed by a final tungsten touch-up CMP process with high tungsten-to-oxide selectivity to level off the protruded metal patterns and drive the gate height to final target.

Applied to SOI-based deep-trench (DT) and FINFET integrated wafers based on 14nm ground rule, the new RMG planarization scheme above demonstrates supreme gate height uniformity. Gate height WiWNU reduces continuously from ~ 2.95% post pass-1 W-CMP to 1.85% post GCIB, and to 1.51% post T/U CMP. The 3sigma of gate height across all dies on 300mm wafers is less than 3nm. The underlying mechanism to achieve nano-scale planarity and uniformity control by this new planarization method will be discussed.
(Invited) Microwave Plasmas Applied for Synthesis of Free-Standing Carbon Nanostructures at Atmospheric Pressure Conditions
Authors: Tatarova Elena , Henriques Julio , Dias Ana , Abrashev Miroslav , Bundaleski Nenad , Felizardo Edgar
Published: February 2020

A microwave plasma-assisted method for synthesis of advanced carbon nanostructures is presented. The method is based on the injection of gas/liquid carbon precursors into a surface-wave sustained argon plasma environment, where the decomposition of molecules takes place. Gas-phase carbon atoms and molecules created in the "hot" plasma diffuse into colder zones of plasma reactor and aggregate into solid carbon nuclei. The main part of the solid carbon is gradually withdrawn from the "hot" plasma region in the outlet plasma stream where flowing carbon nanostructures assemble and grow. Selective synthesis of free-standing graphene sheets and diamond-like nanostructures was achieved. The engineering of the graphene sheets’ structural qualities and the control of the number of atomic layers per sheet is achieved via synergistic tailoring of the "hot"plasma environment and thermodynamic conditions in the post-discharge zone. The produced sheets (1-5 atomic layers) are stable and present much better qualities than those of graphene assembled via conventional methods, while being synthesized without the need of metal/crystal substrates. The synthesized structures have been analyzed by Raman spectroscopy, scanning electron microscopy, high-resolution transmission electron microscopy and X-ray photoelectron spectroscopy. It is worth noting that milligrams of high quality self-standing graphene sheets in a readily dispersive form can be obtained within a minute, through a single step process at atmospheric pressure conditions. The method is widely open for scale-up by using large-scale configurations of wave driven plasmas.

Acknowledgements: This work was supported by Fundação para a Ciência e a Tecnologia, under 2015 Strategic Project.
(Invited) Deep Silicon Etching Increasingly Relevant >20 Years on!
Authors: Thomas Dave , Muggeridge Matthew , Hopkins Janet , Launay Nicolas , Ashraf Huma , Barrass Tony
Published: February 2020

In the early 1990’s researchers at the Robert Bosch facility in Stuttgart invented a novel method of etching very deep features into silicon.  This led to a patent being granted in 1994.   Subsequently (and still) referred to as the ‘Bosch’ process it was first licensed to SPTS who shipped the first commercial systems in 1995.  Originally intended as a method of fabricating devices for the then emerging automotive MEMS sector, its use has since diversified to cover virtually all other MEMS markets. Most recently the use of the Bosch Process has expanded into through silicon via (TSV) etching in 3D packaging applications. In 2014 in Amsterdam the inventors (Franz Laermer and Andrea Urban) were awarded the IEEE Jun-Ichi Nishizawa Medal for revolutionising MEMS by enabling the proliferation of many of the everyday devices that surround us today (such as the inertial sensors in airbags and various chip-sets in smart phones, gaming consoles and laptop computers).

This paper will describe what is possible today using the Bosch process and will consider future applications and uses.  The diversity of the approach will be illustrated through various examples including cavities etched at high rates, features with aspect ratios of 90:1, profile tilt to <0.2°, TSVs for wafer stacking and the increasing demand for more precise control including end-point detection below 0.5% open area. The types of devices that require such performance will also be discussed – everything from inertial MEMS, integrated passives, microphones, power semiconductors, microphones, interposers and stacked memory die. The relevance of the Bosch process to newer application areas such as die singulation and BioMEMS will be discussed.  The developments in reactor designs necessary in achieving these advancements will also be reviewed.

The longevity of the Bosch approach is in part due to the lack of alternative methods able to achieve the same results in Si.  A brief comparison with the competing technologies of wet chemical etching, single step plasma etching, cryogenic etching and LASER drilling will be presented.

300mm wafers are in routine use for Bosch etching of TSVs as part of advanced wafer level packaging integration schemes.  However 300mm wafers are now also being considered for MEMS to maximise the die per wafer or to allow direct bonding and integration of MEMS functionality with the best available CMOS chip-sets.  The latest results for deep silicon etching of 300mm will also be presented.
(Invited) Impact of Spark Plasma Sintering on the Thermoelectric Properties of Advanced Nanostructured Materials for Waste Heat Recovery
Authors: Wu Yue
Published: February 2020

The rapid development of nanomaterials in the past decade has provided a possibility of directly converting waste heat back to electricity based on the thermoelectric Seebeck effect. In the past four years, we have developed a transformative approach to pioneered low cost and scalable solution-phase growth methods to mass produce thermoelectric nanowires and nanowire heterostructures to match the physical and economic magnitudes of energy use and economical entertainment in the manufacture/recycling. We have studied how spark plasma sintering can help to improve the density, mechanical strength, and electrical conductivity of these nanowires and nanowire heterostructures while minimizing the phase impurity and grain growth. These nanostructured thermoelectric materials show a significantly enhanced performance compared to the bulk crystals based on the quantum confinement and energy filtering.
Li2CO3 As an n-Type Dopant in Enhancing the Electron Injection of Organic Light-Emitting Devices
Authors: Liu Ya-han , Tsai Chi-Ting , Chu Sheng-Yuan
Published: February 2020

In this article, we demonstrated the OLED incorporating a transport layer composed of lithium carbonate (Li2CO3) doped into the 2-methyl-9, 10-di (2-naphthyl) anthracene (MADN) as electron injection material. In our devices, an OLED with n-doping structure ITO/NPB (40nm)/Alq3 (40nm)/Li2CO3: MADN (5nm, 25%)/LiF (1nm)/Al (140nm) accomplished maximum luminance of 20760 cd/m2 and current efficiency of 4.878 cd/A. By contrast, the device without doping Li2CO3 ITO/NPB(40nm)/Alq3 (40nm)/ MADN (5nm)/LiF (1nm)/Al (140nm) achieved a maximum luminance of 15530 cd/m2 and current efficiency of 3.922 cd/A. The device of the standard one ITO/NPB(40nm)/Alq3 (40nm)/LiF (1nm)/Al (140nm) only achieved a maximum luminance of 18450 cd/m2 and current efficiency of 3.134 cd/A.

The experiment results show that the transport layer with appropriate doping can efficiently enhance the electron injection, leading to more balanced concentration of electrons and holes. Compared with the standard sample, the maximum luminance and current efficiency are increased by12.5% and 55.6%, respectively.

Figure 1
(Invited) Employing Electrophoretic Deposition in Biomaterial Processing
Authors: Tayebi Lobat
Published: February 2020

Manipulation of biomaterials including biomedical polymers/ceramics, collides, cells, proteins and enzymes using electrophoresis deposition (EPD) method is the focus of this presentation.

The deposited layers by EPD can be highly homogeneous with microstructural uniformity. Their thickness is controllable and the coating can be applied in complex three-dimensional (3D) structures such as the 3D-printed scaffolds produced for tissue engineering applications.  

Three characteristics of EPD make this technique very attractive for different biomedical applications: 1) high adaptability, 2) low cost and simple experimental set up and procedure, and 3) scaling up capability.

The interest in the general applications of EPD in material processing has been extensively increased during the last decade, with emphasis on employing EPD for nanomaterials and biomaterials.

Coating of hydroxyapatite (HA) Ca10(PO4)6(OH)2 on Titanium substrate by Ducheyne et al. in 1986 can be considered as an initial step toward employment of EPD in biomaterial processing. Since then, there were valuable attempts for developing various nanocomposite coatings on biomedical constructs including 3D porous structures. Most of these constructs were originally designed for orthopaedic applications.

Recent expansion of the EPD biomedical application includes improvements in tissue engineering scaffolds, biosensors, drug delivery systems and different functional thin films. The use of EPD to produce biofilms is being progressively investigated recently.

EPD as an advanced electric field-assisted deposition method can now be employed for coating of carbon nanotubes (CNTs), bioactive particles, and biological objects such as proteins on biomedical constructs and devices.

This talk will present a summary of the relevant works during the last decade describing the use of EPD in biomaterial processing and biomedical applications.
Reversible Assembly of Colloidal Particles Using Low Frequency Pulsed DC Electric Fields
Authors: Lee Elaine , Dudoff Jessica , Coe Hannah , Giera Brian , Pascall Andrew J. , Worsley Marcus A. , Kuntz Joshua D. , Zepeda-Ruiz Luis
Published: February 2020

We present the reversible assembly of colloidal nanoparticles in organic solvents using low voltage and low frequency pulsed DC electric fields. Commercially available and custom nanoparticles (diameter ~ 50-200 nm) were suspended in organic solvents at concentrations of 0.25-50 wt% and sandwiched between indium tin oxide (ITO) electrodes of spacing 25 μm-2mm. Using square waves of frequency 0.25-5 Hz, voltages 0.5-5V, and DC offset 0.25-2.5V, colloidal suspensions were actuated for switchable contrast. Upon switching off the electric field, the assembled nanoparticles are able to resuspend within seconds. Using patterned electrodes, lateral electromigration of the particles was demonstrated. Depletion of the particles to the electrode regions resulted in transparency in the non-patterned regions. The distinct contrast generated can be exploited for tunable display applications.

This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344. LLNL-ABS-679931.
Enhanced Rate Performance of Li-S Batteries Enabled By Polysulfide Reactions
Authors: Wu Nae-Lih , Lee Rung-Chuan , Jin Jian-Ting , Fang Jason
Published: February 2020

Lithium-sulfur (Li-S) battery is a promising rechargeable battery system that has both high theoretical capacity and energy density. Moreover, sulfur (S) is inexpensive and nontoxic, making Li-S suitable for large-scale energy storage applications. Sulfur (S8) lithiation during the operation of Li-S battery is a multi-step electrochemical process that involves different lithium polysulfide (Li2Sn, 1…n…8) intermediates. The long-chain polysulfides (PSs) are highly soluble in the aprotic organic electrolyte. There has been a broad consensus that PS dissolution is directly linked to the deterioration of several key performance indexes, such as cycle life, self-discharge and coulombic efficiency, of the battery. However, it is demonstrated in this presentation that the PS dissolution process could have a profound effect on the rate capability of the Li-S battery.

It is shown that solution reactions among the PSs take place concurrently with the electrochemical reactions occurring at the solid surfaces. Surprisingly, with properly designing the electrode structure, one can take advantage of the PS solution reaction pathways to substantially enhance the rate capability of a Li-S battery. The following figure compares the rate performance of two Li-S cells that contain the same S-C composite particles having 45% S content but different electrode design. The two electrodes showed dramatically different  rate performance.

Figure 1
Characterization and Electrochemical Performance of Nanostructured Transition Metal (M= Fe, V, Mn) Oxides for Sodium-Ion Batteries Oral Presentation
Authors: Ellis-Terrell Carol Ann , Rhodes Christopher , Perera Sanjaya , Niu Sibo , Archer Randall
Published: February 2020

As the battery technology field continues to grow rapidly into applications such as electric vehicles and stationary energy storage, there is a need for alternative rechargeable batteries.  Although lithium-ion batteries have recently dominated the rechargeable battery market, there are serious concerns regarding the limited availability and cost of lithium. (1)  Sodium-ion batteries (SIB) offer an alternative to traditional lithium-ion batteries (LIB) as they have the potential to be lower cost and provide comparable capacities.  Electrodes that provide high capacities, voltages and reversibility are required for developing high performance SIBs.  The larger ionic radius of Na-ions compared to Li-ions requires electrode materials that can reversibly accommodate the larger Na-ions.  Nanoscale materials have been shown to be a promising route to provide improved electrodes for Na-ion batteries.(2)  Our group has investigated transition metal compounds (MXy, M=V, Fe and Mn and X=O) where the nanoscale structure presents a unique structural design in which two-dimensional materials are produced.  The shape, sizes and composition of the metal oxide materials can be controlled.  In this talk, we will present the synthesis, structure and electrochemical performance of nanostructured metal oxide cathodes for sodium-ion batteries.

1). M.D. Slater, D. Kim, E. Lee, C.S. Johnson, Adv. Funct. Mater.
2013, 23, 947-958.

2). J. Zhu, D. Deng, Angew. Chem. Int. Ed.
2015, 54, 3079-3083.
Transition Metal Oxide Nanosheets for Improved Performance Li-Ion and Mg-Ion Cathodes
Authors: Rhodes Christopher , Perera Sanjaya , Archer Randall , Niu Sibo , Ly Carol
Published: February 2020

Next generation batteries needed for numerous consumer and vehicular applications require improved electrochemical charge storage materials that have higher capacities, improved rate capabilities, and longer cycle lives.  Nanosheets consisting of atomic two-dimensional (2D) layers have a number of key features for cathodes including rapid surface-based charge storage rather than intercalation, quantum confinement in two dimensions, and the ability to accommodate substantial structural changes during insertion/de-insertion.  We have explored transition metal (M=V, Fe, Mn) oxide nanosheets to provide improved cathodes for Li-ion and Mg-ion batteries.  Synthesis conditions were controlled to obtain nanosheets with controlled sheet sizes, phase, and aggregation.  Temperature treatments were found to significantly affect the electrochemical charge and discharge capacities with in some cases lower temperature treatments providing improved performance over higher temperature treatments.   Using different drying conditions was explored as a route to maintain largely distinct nanosheets and prevent nanosheet restacking which facilitates the storage of larger cations (e.g. Mg-ions).  Obtaining oriented nanosheets through using substrate interactions and applied fields was investigated to increase the electronic conductivity and improve the rate capabilities.   The ability to control the structure and properties of transition metal oxide nanosheets provides a route to cathodes with improved capacities, rates and cycle life.
Stabilization and Functionalization of P4332 Type LiNi0.5Mn1.5O4 By Incorporation with Cu2+ Substitution and Characterization of Their Electrochemical Properties
Authors: Zettsu Nobuyuki , Shiiba Hiromasa , Satoshi Kida , Teshima Katsuya
Published: February 2020

We studied the phase stability of P4332-type LiNi0.5Mn1.5O4-

d

phase through the substitution of transition-metals by using ab initio DFT calculations as well as flux growth of their single crystals. Computational studies reveal that small quantities of Cu2+ substitution into Mn2+ site stabilizes LiNi0.5Mn1.5O4-

d

  crystalized into P4332 lattice as compared to that of Fd-3m. Furthermore, Cu2+ substitution enhances its electronic conductivity through the d-electron doping effect and reduces activation energy for the Li+ transfer. As predict computationally, flux grown LiNi0.49Cu0.01Mn1.49O3.62 single crystalline particle-based composite electrodes show flat plateau in their charge-discharge curves at around 4.7V (vs Li+/Li) arose from the Ni2+/Ni4+ redox couples, and showed higher specific capacity of ca. 140 mAh/g under operation with current density of 0.2 C. And cyclic voltammetry, Raman spectroscopy, TEM coupled with SAED, and Rietvelt confinement reveals the LiNi0.49Cu0.01Mn1.49O3.62 particles are crystallized into highly ordered P4332 lattice. Interestingly, C rate and high voltage capability are also enhanced significantly with no any assistance of additives. More than 70% of original discharge capacity is retained under operation with current density of 10C. And 96 % of original discharge capacity is retained after 100 cycle charge-discharge test with cut-off voltage of 4.8-3.5V.
Molten Salt Synthesis of Transition Metal Oxides Modified Li4Ti5O12 As Anode Material of Li-Ion Battery
Authors: Guo Qingjun , Li Bing
Published: February 2020

In order to meet the requirement for the rapid development of electric vehicles (EVs) and hybrid electric vehicles (HEVs), lithium-ion batteries (LIBs) with high safety, high stability and high energy are urgently needed. Spinel-type Li4Ti5O12 (LTO) has become the most promising anode material of the LIBs used in EVs and HEVs as its’ zero variation. However, LTO intrinsically insulative character, and large polarization at high rates restrict its high energy and power density. Our study focuses on increasing the specific surface area and electron conduction through thimbleful transition metal oxides (Fe2O3, Fe3O4, Co3O4) modifying LTO bymolten salts synthesis method.

Transition metal oxides not only decrease greatly on particle size, but also enhance the electrochemical performances of LTO and the reaction mechanism is investigated. Transition metal atoms as the interstitial and substitutional atoms homogenously distributes in the crystal lattice of LTO. The optimal modified LTO exhibits a excellent first discharge capacity of 269.3 mAh g-1 at the 0.1 C and 201.3 mAh g-1 at 1 C; good high rate capability (123.4 mAh g-1 at 12 C). Doping increases nucleation sites during LTO formation in molten salts which reduces the particle size of LTO. Substituted atoms expand the paths for Li+ de/ intercalation and cause O32e or Li8a,16d vacant sites which improves the electronic conductivity of LTO. These findings indicate thimbleful metal oxides doping as an effective method to improve LTO performance by use of molten salt method which can use on the industrial production.

 

KEYWORDS:
molten salt, transition metal oxides, Li4Ti5O12, anode material, lithium-ion battery