bluuebunny/crossref_metadata_2025 huggingface dataset:
(Invited) Liquid Phase Ion-Gun Technique for Degradation and Evaluation of Oxide Films
Authors: Fushimi Koji
Published: February 2020

Halide ions in environments destabilize oxide films on materials and lead to a local corrosion of the material. In order to investigate a quantitative effect of halide ions on oxide degradation, an electrochemical technique with a concentrating method of halide ions on the oxide in an experimental setup is necessary. Liquid phase ion-gun (LPIG), in which silver halide layer on a silver microelectrode is reduced in liquid phase, is one of the beneficial techniques to concentrate halide ions the vicinity of the material surface. Fushimi and Seo developed an LPIG as a chloride ion-generator and successfully applied in boric acid-borate buffers to degrade passive film on pure iron locally and to induce the local corrosion [1, 2]. Degradation reaction of the film was classified into three processes; depassivation induction, film depassivation, and corrosion propagation or repassivation, from electric charges consumed by both LPIG microelectrode and specimen electrode. Since an electric charge consumed on the microelectrode for the generation of chloride ions during the induction process corresponds to the amount of chloride ions needed for the degradation of passive film, the stability of passive films on different crystallographic grains were also evaluated. LPIG was also combined with electrochemical quartz crystal microbalance and used to investigate local corrosion of copper [3]. Lee and Fushimi have developed another type of LPIG, in which silver sulfide layer on the silver microelectrode is reduced to generate sulfur species, and applied to sulfide surface of silver electrode [4] and type 316L [5], 304, 430 and 443 [6] stainless steels.

In this paper, the beneficial features of LPIG technique for investigating the initiation of local corrosion on iron-based materials are reviewed. The quantitative analyses for the halide ions generated from LPIG microelectrode will also be discussed.

References

[1]  K. Fushimi, K. Azumi, M. Seo, J. Electrochem. Soc., 147(2), 552-557 (2000).

[2]  K. Fushimi, M. Seo, J. Electrochem. Soc., 148(11), B450-B456 (2001).

[3]  F. Falkenberg, K. Fushimi, M. Seo, Corros. Sci., 45(11), 2657-2670 (2003).

[4]  J.-S. Lee, K. Fushimi, Y. Kitagawa, T. Nakanishi, Y. Hasegawa, J. Electrochem. Soc., 162(4), C115-C120 (2015).

[5]  J.-S. Lee, Y. Kitagawa, T. Nakanishi, Y. Hasegawa, K. Fushimi, J. Electrochem. Soc., 162(14), C685-C692 (2015).

[6]  J.-S. Lee, Y. Kitagawa, T. Nakanishi, Y. Hasegawa, K. Fushimi, submitted.
Effect of Cr Content on Pit Initiation Behavior at MnS Inclusions in Fe-Cr Steels
Authors: Asano Shinpei , Muto Izumi , Sugawara Yu , Hara Nobuyoshi
Published: February 2020

It is well known that Cr improves the pitting corrosion resistance of stainless steels. In chloride-containing environments, MnS inclusions act as a preferential site for pit initiation of stainless steels. In this study, a microelectrochemical approach was applied to elucidating the effect of Cr addition on the corrosion resistance of pit initiation at MnS inclusions.

Fe-5Cr, Fe-12Cr, and Fe-18Cr steels, containing 0.027 mass% S, were prepared by vacuum induction melting. Heat treatment was performed at 1123 K for 600 s. After the heat treatment, the steels were water-quenched. Their surfaces were polished down to 1 μm diamond paste. Since the MnS inclusions are darker than the steel matrix, they are clearly visible in the as-polished condition without etching, and it was confirmed that the inclusions consisted of Mn, S, and a small amount of Cr. This type of inclusion was simply referred to as MnS inclusion.

In order to ascertain the dissolution potential of the MnS inclusion, the potentiodynamic polarization curves for the small areas with the inclusion were taken in a naturally aerated 0.1 M Na2SO4 solution at 298 K. As shown in Fig.1a, the increase in current density around 0.05 V was a characteristic common to all the specimens. After the polarization, the inclusions were observed by a field emission scanning electron microscope equipped with an X-ray energy-dispersive spectrometer, and it was concluded that the current increase around 0.05 V was due to the dissolution of the MnS inclusion.

Figure 1b shows the potentiodynamic polarization curves for the small areas with the inclusion in a naturally aerated 0.1 M NaCl solution at 298 K. In the cases of Fe-5Cr and Fe-12Cr, the large current increases were observed around 0.05 V. It was suggested that the MnS dissolution directly brings about the initiation of pit (Fig1c-e). On the other hand, no stable pit was initiated on Fe-18Cr. Moreover, even the initiation potential of meta-stable pit was higher than the inclusion dissolution potential. The addition of Cr in the steels was shown to improve the repassivation ability of the steel matrix.

Figure 1
Modeling the Effect of High-Temperature Alloys on Corrosion inside Molten Salt Systems
Authors: Tavakoli Bahareh Alsadat , Shimpalee Sirivatch , Weidner John W. , Garcia-Diaz Brenda L. , Martinez-Rodriguez Michael J. , Olson Luke Christopher
Published: February 2020

The corrosion of high-temperature alloys is a major challenge for the development of concentrated solar power (CSP) systems using molten halide salts. High-temperature alloys are usually iron-, cobalt- or nickel-based alloys containing more than 20% chromium (or 30% for cobalt), which is adequate to form a protective passive layer against further oxidation. Unlike the more conventional oxidizing media, most oxide films are chemically unstable and tend to be completely soluble in the corroding molten halide melts. Therefore, passivating oxides are not adequate and corrosion occurs primarily through the oxidation and subsequent dissolution of alloying elements into the melts.

USC-Columbia and SRNL have developed a corrosion model that predicts corrosion rates and mechanisms of high-temperature alloys in contact with molten halide salt under conditions predicted for a prototypical high temperature CSP heat transfer system. The corrosion model is coupled to a computational fluid dynamics (CFD) component that considers temperature and fluid flow effects on the corrosion rates predictions. Several high-temperature alloys such as Incoly 800H, Haynes NS-163 and Haynes 230 are considered. Kinetic and mass transfer parameters for the alloys undergoing corrosion in the model are baselined to experimental corrosion measurements. Baseline corrosion measurements were conducted in static immersion cells at 850°C and in a thermosiphon designed to allow exposure of the coupons to flowing molten salt at a hot zone temperature of ~933°C and a cold zone of ~880°C. The model is also capable of considering the effect of magnesium cathodic protection for these alloys in contact with molten halide salts. The model has been validated against experimental investigations and good agreement has been achieved between model predictions and experimental observations.

Figure 1 shows a comparison of the model prediction and experimental results of corrosion rate, i(A/m2) at 850°C for different alloys in MgCl2-KCl molten salt.

Acknowledgements

The authors gratefully acknowledge the financial support for this work from the DOE EERE SunShot Initiative (DE-AC36-08GO28308) under a subcontract from SRNL to the University of South Carolina. The authors also thank the University of South Carolina Center for Fuel Cells and the CD-adapco group for their support. Figure caption: Comparison of the model prediction and experimental results of corrosion rate, i(A/m2) at 850°C for different alloys in MgCl2-KCl molten salt.   

Figure 1
The Effect of Environmental Stress Crazing on the Corrosion Performance of PET Coated Packaging Steel
Authors: Warren David , de Vooys Arnoud C.A. , McMurray Hamilton Neil
Published: February 2020

The market for polymer laminated packaging steel is currently growing due to the improved barrier performance, reduced processing by the can maker and increasingly as a result of environmental concerns associated with solvents and health concerns with bisphenol A (BPA), a major component in epoxy phenolic lacquers. Despite the benefits of these laminated systems a concern exists around environmental stress cracking/ crazing (ESC) of the polymer, a phenomenon that accounts for 15% of bulk polymer failures [1].

The primary aim of this paper was to examine the effect ESC has on the corrosion performance of Electro Chromium Coated Steel (ECCS) laminated with polyethylene terephthalate (PET). Electrochemical Impedance Spectroscopy (EIS) was used to characterise the ESC/corrosion phenomena. EIS is a recognised system for assessing organic coatings however it gives a global measure of coating performance thus dye penetrant and scanning vibrating electrode technique (SVET) have been used to spatially characterise the EIS signal.

EIS measurements were carried out over a 4 day period in aqueous 5 wt % NaCl to measure the drop in coating impedance as the coating degrades. This was fitted to an equivalent circuit that is correlated back to the coated system. Dye penetrant (figure 1) and SVET (figure 2) were subsequently used to characterise the influence the crazing has on the failure of the coating.

In brief, an argument is presented that two main features exist; initially there is the openness of the crazes at the surface that provide diffusion routes into the surface although a significant time delay occurs due to the complex diffusion routes offered by the crazes. After the time delay the second feature occurs as diffusion increases and then in turn the conductivity of the coating also increases until conditions become sufficient at the metal/polymer interface for the steel to be attacked. Due to the poor protection offered by the nano scale chromium coating corrosion then ensues.

[1] D. C. Wright, Environmental stress cracking of plastics Shrewsbury: Rapra Technology, 1996.

Figure 1
Effects of CNT-Zinc Hybrid Structure on Corrosion, Scratch and Adhesion Strength of Epoxy Composite Coating
Authors: Daneshvar Fatah Farhad , Sue Hung-Jue , Castaneda Homero
Published: February 2020

Metal-rich organic coatings are one of the most common methodes to hinder the corrosion in metals. These coatingsDue to environmental concerns and technical challenges there is an intrest in decreasing the required amount of these metals within the organic coatings. Conventionally graphite or carbon black is added to provide a conductive network and decrease the amount of metal within the coating. However due to high perculation thresholds for these filers, high amount of them is required which leads to inferior mechanical properties and promotion of galvanic corrosion. On the other hand it has been shown that Carbon nanotubes (CNT) can form a conductive network in very low amounts. Moreover, CNTs can improve the mechanical properties and tribological properties of the coatings. Damages such as scratch can significantly reduces the protective properties of organic coatings. In this work the effect of CNT-Zn addition and the dispersion method on the corrosion resistance and tribological properties of the epoxy-Zn/CNT hybrid coatings are studied.
Performance Improvement of Organic Solar Cells By the Integrated Antireflection System with Moth Eye Surface and High-Refractive-Index Glass
Authors: Kubota Shigeru , Harada Yoshiki , Sudo Takenari , Kanomata Kensaku , Ahmmad Bashir , Mizuno Jun , Hirose Fumihiko
Published: February 2020

Organic photovoltaics (OPVs) are considered to have a great potential to solve future energy supply scenarios due to their advantages such as low production and material costs. The power conversion efficacy and lifetime of bulk heterojunction OPVs have been significantly increasing in the last decade, although further improvements will be required for the large-scale commercialization. Because the OPV cell includes a stack of several thin layers, a certain percentages of light energy is always lost by the reflection at the interfaces between the different materials and the absorption in the layers different from the photoactive layer. In addition, due to a low carrier mobility of organic semiconductors, the active layer of OPVs should be very thin (around 100 nm), which makes it difficult to fully absorb incident light. To enhance light absorption in the thin active layer, it is important to adequately design antireflection (AR) system that can trap light into OPVs. Recently, many studies on the AR technique have applied the moth eye texture, which is a nanostructure inspired by the corneal surface of moth’s eyes. In the moth eye coating, the device surface is covered with two-dimensional array of cones with a period and height of a few hundred nanometers. Since the effective refractive index (RI) within the moth eye gradually changes in the direction of the cone axis, the level of reflection can be significantly weakened. In cases where the moth eye texturing is applied to OPVs, it is required that the material used in the texture should have compatibility with the advantage of the OPVs, such as low costs. Therefore, in this study, we employ moth eye structure made by organic polymers, since the textured pattern can be fabricated cost-effectively by nanoimprint lithography with polymeric resists. To reduce the effects of optical mismatch between the low-RI organic polymers and high-RI materials in the OPV cell (e.g., indium-doped tin oxide), we propose a new design of AR system. In this system, the hybrid AR structure, which is composed of the moth eye and multilayer interference coatings, is integrated with a high-RI glass substrate. We numerically investigate the optical properties of OPVs and demonstrate that the proposed AR system is quite useful for attaining broadband and omnidirectional antireflection. In addition, we experimentally measure the effect of the integrated AR design on the photocurrent generation of OPVs to verify the simulation results.

Acknowledgement: This study was partially supported by KAKENHI (26390025) from the Japanese government, and by JST, CREST.
Modeling and Mechanistic Analyses of Electrochemical Impedance Spectroscopy of Ion Transport in Photovoltaic Devices Containing Perovskite Active Layers
Authors: Tuominen Mark T , Adhikari Ramesh Y , Xu Zhou , Bag Monojit , Renna Lawrence A , Cutting Christie L , Venkataraman Dhandapani
Published: February 2020

Easy to make photovoltaic devices incorporating perovskite active-layer materials have been observed to exhibit high efficiency energy conversion. Unfortunately, the performance of these devices degrade over time, especially with regards to continued exposure of light. Recent work using electrochemical impedance spectroscopy (EIS) measurements at systematic values of dc voltage bias reveals that the degradation is related to photo-induced diffusive ionic motion in the perovskite layer [M. Bag, et al. J. Am. Chem. Soc 2015, 137, 13130]. This behavior is revealed in the EIS data as a distinct Warburg impedance, easily seen in Nyquist plots. In this work the perovskite active layers used are alkyl ammonium metal halides, containing either methylammonium (MA) or formamidinium (FA) ions, or MAxFA1-x mixtures thereof, with lead triiodide. Importantly and fortunately, the experiments have several independent variables to control to probe the underlying physics: dc bias voltage, temperature, and light/dark conditions. Here we present detailed modeling and analyses of the EIS behavior for these perovskite systems, providing deeper understanding of the physical basis for the ionic motion, investigating the dependence of ionic motion on temperature and light intensity. This is particularly important to unpack physically, given that these are multilayered, multi-material devices (containing interfaces) in which both electron and ionic mobilities contribute to the net impedance. The insights and models discussed here yield guidance for the design of new perovskite and related materials for better device stability.
Characterization of Cu-Based I-V-VI Thin Films Using Hybrid Inks
Authors: Cho Ara
Published: February 2020

Cu(In,Ga)Se2 (CIGS) and Cu2ZnSnSe4 (CZTSe) have been studied as the most promising materials in solar cell research and production area. Until now, CIGS solar cell has already reported over 21 % conversion efficiency. Despite the real progress of efficiency, however, CIGS and CZTS absorbers in photovoltaic cells have been challenged by many problems, such as elemental scarcity, toxicity and structural complexity. Especially, complex stoichiometry and high process temperature are important obstacles to overcome because the elemental ratio of absorbers is hard to control and the bottom-cell can be easily degraded for fabricating high efficient tandem solar cell while the top-cell process is carrying on.

Recently, Cu-based I-V-Vl materials, especially Cu-Sb-S phases, have been highlighted because of their characters, such as a band gap and a high optical absorption co-efficient. In the Cu-Sb-S phases, there are four major phases (CuSbS2, Cu3SbS3, Cu3SbS4, Cu12Sb4S13) but most of research have reported only about synthesis and characterization of nanocrystals.

In this study, thin films of Cu-Sb-S phases were formed using non-vacuum process which is cost-effective. To form thin films of Cu-Sb-S using a non-vacuum hybrid ink, Cu and Sb precursors were coated and sulfurized with a rapid thermal annealing (RTA) process. However, each optimum sulfurization condition is needed to obtain single phase thin films of each material. The fabricating thin films were analyzed and confirmed as target phases. The characteristics of each Cu-Sb-S absorber and photovoltaic performances of fabricated cells will be presented.
Effects of Naf Post-Deposition Treatment on Defect Chemistry and Surface Properties in CIGS Thin Film Solar Cells
Authors: Kim Suncheul , Kim Seungtae , Ahn Byungtae , Park Joongkeun
Published: February 2020

The high temperature process at the 2nd stage of co-evaporation easily leads to the formation of the point defects such as Se vacancy and antisite defects in CIGS absorber layers. To passivate such defects, NaF post-deposition treatment (PDT) was carried out. After the NaF PDT at 300°C, Se vacancy and antisite defects were significantly reduced. In addition, out-diffusion of Cu to surface was suppressed, thereby improving the overall performance of CIGS thin film solar cells. Here, we report on the influence of NaF PDT on the defect chemistry as revealed by low-temperature photoluminescence (LT-PL) and X-ray photoelectron spectroscopy (XPS).
Highly Efficient and Stable Perovskite Solar Cells with a p-I-n Type Planar Geometry
Authors: Park Ik Jae , Kim Jin Young
Published: February 2020

Perovskite solar cells based on the organometal halides (e.g. methylammonium lead iodide; MAPbI3) have been investigated very intensively owing to their skyrocketing conversion efficiencies. The perovskite solar cells can be classified either as a n-i-p type or as a p-i-n type depending on the direction of charge collection. Among them, the p-i-n type devices especially with a planar structure have advantages such as simple and low-temperature processes compatible with flexible substrates, negligible hysteresis effect, and potential tandem configuration with other highly efficient inorganic solar cells. However, the p-i-n type planar devices have issues of lower conversion efficiency compared with the n-i-p type counterparts and poor stability resulting from the use of organic hole-extraction layers. In this study, we successfully demonstrate highly efficient p-i-n type planar perovskite solar cells with inorganic NiO-based hole-extraction layer. Factors that govern the solar cell performance of the NiO-based perovskite solar cells have been investigated systematically, especially regarding their influences on the fill factor. It has been found that the conductivity of the hole-extraction layer and its physical/electrical contact with the perovskite layer are very important for the device performance. It has been also found that the long-term stability of the perovskite solar cells has been significantly enhanced by replacing the conventional organic PEDOT:PSS layer with the inorganic hole-extraction layer. As a result, the best NiO-based device exhibits a high conversion efficiency of ~ 18% with no hysteresis effect, which is the best efficiency among the p-i-n type planar devices.
Nanostructure Provides a Major Breakthrough in Properties of Transparent Polymer, and Solar Cells, Which Are Encapsulated By Nanopolymer
Authors: Shembel Elena M , Redko Vlad I , Klyui Nikolai I , Yashchenko Larisa , Yarova Nataly
Published: February 2020

Enerize nanostructured transparent polymer for encapsulation the solar cells provides a new achievements, including the increasing the efficiency of the solar cells even under conditions when the illumination falls on the surface of the polymer coating at an angle; transparency 20% even in the wavelength 250 nm. Additional advantages include reduced weight, increased resistance to degradation by UV and high mechanical strength, stability under prolonged exposure to high and low temperatures, thermal-cycling, mechanical impact, and high relative humidity. Enerize nanostructured polymers are promicing for encapsulation other optical devices including organic light-emitting diodes (OLED).

The nanostructure of the proprietary transparent polymer include the nano clusters and micro-domains in the volume of the polymer. This results in micro lenses, which improve the optical properties of transparent polymer, and add the novelty and feature for solar cells and other optical devices. Composition of the initial materials for the polymer synthesis, parameters of the encapsulation, nature of the semiconductor material of the solar cell provide the synergetic effect on the efficiency of the solar cells after encapsulation. Results of the testing of the properties of the nanopolymer film, including light absorption and reflection; and different types of solar cell based on the silicon, thin film flexible non - silicon solar cell will be discussed during presentation
Perpendicular Stt-Mram Scaling Challenges and Potential Solutions
Authors: Zhong Tom , Thomas Luc , Jan Guenole , Zhu Jian , Liu Huanlong , Lee Yuan-jen , Le Son , Tong Yu-Ring , Shen Dongna , He Renren , Haq Jesmin , Teng Jeffrey , Guisan Santiago Serrano , Iwata-Harms Jodi , Patel Sahil , Lam Vinh , Wang Yu-jen , Torng Terry , Wang Pokang
Published: February 2020

Significant progresses have been made in recent years in perpendicular spin torque transfer magnetic random access memory (pSTT-MRAM) technology development by many companies or organizations. Commercialization of pSTT-MRAM is more real today than ever in the long history of MRAM technology development. We have recently reported fully functional pSTT-MRAM chips and macros with sub-5ns writing speed based on 90nm and 40nm node CMOS technologies [1,2]. These technologies can be potentially used to replace current embedded non-volatile memories such as embedded flash memories or SRAM and be applies to energy efficient applications such as internet of thing (IOT). In this presentation, we will review recent progresses and discuss STT-MRAM scaling challenges for product at 28nm technology node and beyond in terms of integration schemes as well as magnetic and electrical transport properties. We will also discuss the potential solutions that we see for these challenges.

References:

[1] G. Jan, Symp VLSI Tech, 2014. pp 50-51.

[2] Yu Lu et al, IDEM Technical Digest, 2015 (in press)
Charge Trap Memory Based on Few-Layer Black Phosphorus and High-K Materials
Authors: Wang Kaiyou
Published: February 2020

Due to the unique properties of the two dimensional material, it has great potential for future information technology devices. Based on field-effect transistors with large hysteresis, consisting of a few-layer black phosphorus channel and a three dimensional (3D) Al2O3/HfO2/Al2O3, we successfully made the nonvolatile charge-trap memory devices. Because of the extraordinary trapping ability of the high-k HfO2, an unprecedented memory window exceeding 12 V is obtained. The device shows a high endurance of over 120 cycles and a stable retention of ∼30% charge loss after 10 years, even lower than the reported MoS2 flash memory. The high program/erase current ratio, large memory window, stable retention and high on/off current ratio, provide a promising route towards flexible and transparent memory devices utilizing atomically thin two-dimensional materials. The combination of 2D materials with traditional high-k charge-trap gate stacks opens up an exciting field of nonvolatile memory devices[1].

References

(1)   Qi Feng, Faguang Yan, Wengang Luo and Kaiyou Wang, Nanoscale, 8(2016)2686.
Tomography of Intrinsic Filamentation in Silica and Hsq Based Reram Devices with Conductive Atomic Force Microscopy
Authors: Buckwell Mark , Zarudnyi Konstantin , Montesi Luca , Ng Wing Hung , Hudziak Stephen , Mehonic Adnan , Kenyon Anthony Joseph
Published: February 2020

Resistive RAM (ReRAM) devices have shown promise in delivering the next generation of electronic memories as flash approaches its scaling limit. Their low operating voltages, small sizes and simple structure enable low power consumption and dense device packing. Although many dielectric materials such as transition metal oxides and perovskites have demonstrated desirable properties in ReRAM architectures, silicon based memories facilitate the route for integration into existing CMOS infrastructures. This makes them particularly suited for investigation and optimisation. In recent work we have specifically looked at devices sandwiching amorphous silicon suboxide or hydrogen silsesquioxane (HSQ) active layers between different electrode materials, including platinum and titanium nitride. We here present characterisation results probing the three-dimensional structure of conducting filaments in our silicon memories. These filaments are thought to be composed of oxygen vacancies and govern the switching mechanism that enables dielectric materials to operate in ReRAM devices. Imaging these features with conventional topographical and cross-sectioning techniques is difficult, owing to the low contrast with the background pristine material. Our results demonstrate the importance of conductive atomic force microscopy in three-dimensional device analysis and show that filament growth conforms closely to the pristine dielectric structure. Formation pathways follow the intrinsic film inhomogeneities, a feature that may produce defect clustering and promote oxygen vacancy generation under electrical stress. We are also able to demonstrate, for the first time in intrinsic switching devices, the competition between multiple growths in which only a single pathway find success.
(Invited) Multifunctional Materials for Electronics and Photonics
Authors: Rosei Federico
Published: February 2020

The bottom–up approach is considered a potential alternative for low cost manufacturing of nanostructured materials. It is based on the concept of self–assembly of nanostructures on a substrate, and is emerging as an alternative paradigm for traditional top down fabrication used in the semiconductor industry. We demonstrate various strategies to control nanostructure assembly (both organic and inorganic) at the nanoscale. We study, in particular, multifunctional materials, namely materials that exhibit more than one functionality, and structure/property relationships in such systems, including for example: (i) control of size and luminescence properties of semiconductor nanostructures, synthesized by reactive laser ablation; (ii) we developed new experimental tools and comparison with simulations are presented to gain atomic scale insight into the surface processes that govern nucleation, growth and assembly; (iii) we devised new strategies for synthesizing multifunctional nanoscale materials to be used for electronics and photovoltaics.
Potential CCP Pulsed Plasma Application at Beol AIO Etch Process
Authors: Zhang Cheng-Long , He Qi-Yang , Zhang Hai-Yang
Published: February 2020

Plasma etching has been extensively used for more than 30 years in semiconductor manufacturing industry [1]. Typically, plasma reactor RF power sources have constant average power to excite the plasma in a vacuum chamber. Such mode of operation is termed as continuous-wave (CW) RF mode [2]. As COMS is being scaled down to 28nm node and beyond, CW plasmas etching processes are reaching their limits to satisfy the multiply stringent requirements, such as better uniformity, higher selectivity, less plasma induced damage, tighter critical dimension and profile control.

The RF pulsed plasma is one of promising knobs to increase the flexibility of plasma processing by enlarging the range of operating conditions [3-5]. There are two main parameters characterizing the RF pulse: one is the pulsed frequency at which the RF power is turned on and off per second; the other is the pulse duty cycle, which is defined as the ratio between the pulse on time and the total pulse duration. As the multiple-frequency RF powers have been introduced for the better control plasma flux and energy in CCP system, the effect of different RF power pulsing varies, bias only, source only and synchronized pulsed plasmas also shows quite different performances.

In this work, self-aligned via (SAV) based all-in-one (AIO) etch processes were performed in one commercial etcher, and the effects of pulsed plasmas on the etch process were analyzed. The different pulsed mode, pulsed duty cycle, pulsed frequency on CCP chamber were tested on the SAV based AIO etching process in BEOL copper interconnect system. We compared the bias only, source only and synchronized pulsed plasma performances, checked the duty cycle effects, which varies from 10% to 90%. The Physical performances were analyzed by CDSEM, SEM, TEM, and TK. Compared with conventional CW plasmas, the performances of AIO etching process could be significantly improved via pulsed plasma, such as more rounding chamfer profile, via bottom CD control, and better SAC process with higher selectivity to metal hard mask.

Acknowledgement

This work is sponsored by Shanghai Rising-Star Program (B type).

REFERENCES

[1] S. Banna, A. Agarwal, G. Cunge, M. Darnon, E. Pargon, and O. Joubert. J. Vac. Sci. Technol. A, vol. 30, 2012, pp. 040801.

[2] S. Banna, A. Agarwal, K. Tokashiki, H. Cho, S. Rauf, V. Todorow, K. Ramaswamy, K. Collins, P. Stout, J. Y. Lee, J. Yoon, K. Shin, S. J. Choi, H. S. Cho, H. J. Kim, C. H. Lee, and D. Lymberopoulos. IEEE Trans. Plasma Sci., vol. 37, 2009, pp. 1730-1746.

[3] R. W. Boswell and D. Henry. Appl. Phys. Lett., vol. 47, 1985, pp. 1095-1097.

[4] P. Subramonium and M. J. Kushner. Appl. Phys. Lett., vol. 79, 2001, pp. 2145-2147.

[5] A. Rousseau, E. Teboul, N. Lang, M. Hannemann, and J. Ropcke. J. Appl. Phys., vol. 92, 2002, pp. 3463-3471.
Galvanic Displaced Nickel-Silicon and Copper-Silicon Interfaces: A DFT Investigation
Authors: Pedrazzetti Lorenzo , Soltani Peiman , Mezzi Alessio , Kaciulis Saulius , Nobili Luca , Magagnin Luca , Tommasini Matteo Maria Saverio
Published: February 2020

Galvanic displacement from fluoride containing solution is a well established technique for the deposition of metals on semiconductor substrates, with a very broad plethora of applications in the electronic, photovoltaic and MEMS industries, due to the film conformal nature and process high selectivity towards silicon surfaces. Immersion plating is able to produce very homogeneous thickness metal seeds. Particularly, Copper and Nickel were the chosen species for silicon plating due to their wide application range and variety of different exploitable properties, also in thin films engineering. Copper has a very good electrical conductivity and charge mobility, while Nickel has good electron transport properties too as well as magnetic features that are exploited in several micro- and nano-devices. Very good results have already been achieved in the past years for Copper and Nickel systems in terms of metal film homogeneity and aspect ratio. In order to have a complete substrates characterization, newly adapted plating baths were used for p-doped Silicon wafers metallization just after a suitable surface cleaning step was performed. The resulting metallic layers showed high homogeneity and high reflectivity, achieving mirror-like appearances as well as very low mean surface roughness. SEM characterization was also used to appreciate the metal layer thickness control achieved by the proposed processes, as well as gathering information about the different metals growth rate. Subsequently, X-rays photoelectrons spectroscopy has been employed to understand the surface state of Silicon, Nickel and Copper in the plated substrate; furthermore X-rays diffraction analysis was used to characterize the crystalline structure of the metallic thin films on top of the semiconductor. The collected data have been employed as input for Density Functional Theory calculations on the Nickel-Silicon and Copper-Silicon interfaces, aiming at the description of the interactions at the interfaces from an atomistic point of view.
Effects of Additives on Ag Nanoparticles Catalyzed Electroless Copper Deposition Using Glyoxylic Acid As a Reducing Agent
Authors: Chang Yu-Chen , Chou Shih-Cheng , Wu Pu-Wei , Chen Po-Chun , Huang Meng-Chi , Wang Yu-Ming , Hsueh Chang-Jung
Published: February 2020

By using nanoparticulate Ag as the activator to replace Pd, glyoxylic acid to replace formaldehyde as the reducing agent, 2,2’–bipyridine, K4Fe(CN)6, PEG-2000, Ascorbic acid, and Bis-(3-sodiumsulfopropyl disulfide) (SPS) as additives, we develop a Cu electroless plating bath to deposit Cu on activated polyimide substrates for flexible electronic devices. Polarization curves are recorded to elucidate the effect of additives over anodic behaviors of glyoxylic acid on activated substrates. Cyclic voltammetric measurements are carried out to clarify the responses of additives on both anodic and cathodic reactions occurring during electroless Cu deposition. SEM is used for observing the morphology of Cu deposition on Ag nanoparticle catalyzed polyimide substrates. XRD is adopted to determine the crystalline structure of Cu deposit. The quality of Cu deposit is inferred from electrical resistivity measurements. We demonstrate an optimized formula for relatively smooth Cu film with strong adhesion to the substrate.
Imaging the Surface of LiMn2O4 with Low-Dose STEM
Authors: Amos Charles Dallas , Ferreira Paulo Jorge , Goodenough John B.
Published: February 2020

The surface of materials is one of the most important aspects of electrochemistry. The surface is where all critical charge transfers and catalytic interactions occur. For Li-ion batteries, the surface of the electrodes dictates the reactivity with the electrolyte, the ability for Li-ions to shuttle between the bulk and the electrolyte, and the rate at which the ions can transfer, all of which has an effect on rate-capability and cyclability. LiMn2O4 (LMO) is a promising cathode material with a high-energy density and a high-rate capability, but it is plagued with a cyclability problem based on a surface effect. In the LMO system the main contributor to cycling degradation is the Mn disproportionation reaction (2Mn3+ = Mn2+ + Mn4+) which creates soluble Mn2+ that is lost to solution. We have used a combination of high-angle annular dark-field (HAADF) aberration-corrected scanning transmission electron microscopy (STEM) and electron energy loss spectroscopy (EELS) to confirm the underlying spinel structure, and we have found, in as-processed LMO, a surface structure composed of Mn3O4 and a lithium-rich Li1+xMn2O4 subsurface layer which occurs as a result of surface reconstruction. We have also identified that oxygen loss is the mechanism by which the surface reconstruction occurs, but the question still remains, is the reconstruction of the material native or is it an effect of the electron beam? Oxide materials can be sensitive to electron-beam-induced phase changes so it is important to lower the electron dose low enough so that a determination can be made whether any impurity phases observed are an effect of the material or an effect of the electron beam. This research answers that question by imaging the surface of LMO with low-dose STEM by reducing the electron beam to pseudo-non-destructive levels. This work serves as an example of the importance of low-dose STEM as a critical technique for correctly identifying transformations and reconstructions in oxide or related materials.
in Situ Transmission Electron Microscopy Studies on Silicon Anodes in Lithium Ion Batteries
Authors: Lee Hyun-Wook , Lee Seok Woo , Cui Yi
Published: February 2020

Extensive research for new energy storage materials has created a high demand for experimental techniques that can provide real-time, single-particle-level information on the dynamic electrochemical processes taking place at the electrode materials during battery charge/discharge cycles. In situ transmission electron microscopy (TEM) on lithium ion batteries has been offered exceptional opportunities for monitoring the dynamic processes of electrode materials during electrochemical reaction at both spatial and temporal resolution.

In this talk, I will introduce in situ TEM studies on Si anodes which suffers the anomalous volumetric changes and fracture during lithiation process. Previously, the lithiation behaviour of a single Si particle has been explained in detail by simulation data and experimental observation. However, in real batteries, since lithiation occurs simultaneously in clusters of Si in a confined medium, understanding how the individual Si structures interact during lithiation in a closed space is necessary. In this regard, I demonstrated physical and mechanical interactions of swelling Si structures during lithiation using well-defined Si nanopillar pairs. Ex situ SEM and in situ TEM studies reveal that compressive stresses change the reaction kinetics so that preferential lithiation occurs on free surfaces when the pillars are mechanically clamped. Such mechanical interactions enhance the fracture resistance of lithiated Si by lessening the tensile stress concentrations in Si structures. This experiment reveals the surprising effects of nanostructure shape, size, and void space for lithiation and the results will contribute to improved design of Si structures at the electrode level for high-performance Li-ion batteries.
(Invited) In-Situ Spectroscopic Observation of Lithium Sulfur Batteries upon Cycling
Authors: Hwang Bing Joe , Tsai Mon-Che , Lee Felix , Lin Ming-Hsien , Cheng Ju-Hsiang , Su Wei-Nien , Huang Chen-Jui , Partovi-Azar Pouya , Kaghazchi Payam
Published: February 2020

Sulfur, with its a high theoretical specific capacity (1675 mAh/g), is an abundant, low cost, and environmentally friendly element that has been extensively studied as a promising electrode material for rechargeable lithium batteries. However, low sulfur utilization and a poor cycle life are among the issues limiting its commercialization. Several of these issues are related to the electronically insulating nature of elemental sulfur and the dissolution of the resulting lithium polysulfides (Li2Sn, 2 ≤ n ≤ 8) formed during the discharge process, especially in a battery comprising of liquid electrolytes. As a result, these polysulfide species readily diffuse to the anode side causing formation of a highly resistant layer on the lithium metal anode that leads to the reduction of Li+ ion mobility and rapid capacity fading during cycling. The interactions between the support and elemental sulfur/lithium polysulfides play an important role in sulfur utilization and cycling stability. To obtain a better understanding of the interactions, in situ Raman and X-ray absorption Spectroscopic techniques together with DFT computation were developed and employed in this work. The Raman peaks observed were assigned successfully by the conjunction with the computational and experimental approaches. The results based on the spectroscopic characterization of the different components reveal that the undesired shuttle mechanism causing the passivation of Li anode can be suppressed due to the preferential interaction between elemental sulfur/lithium polysulfides with the designed supports or polymer electrolytes. This work has opened a new path towards the development of new supports and polymer electrolytes for lithium sulfur battery applications.
(Invited) To Understand Local Structure Evolution and Ion Dynamics of the Electrode/Electrolyte Materials Combined with Different Spectroscopic Techniques
Authors: Yang Yong
Published: February 2020

Li-ion battery has become the most important energy systems for portable electronics, power tools and automobile applications such as hybrid and plug-in electric vehicles. However, it is still necessary to enhance their electrochemical performance such as energy density and cycle life, for promoting their competition capability as vehicle power system. Obviously, electrode materials, especially positive electrode materials either working voltage or reversible capacity determine the energy density of the Li-ion batteries at mostly[1,2].

In the presentation, some recent work about in-situ or ex-situ characterization of local structural evolution and Li-ion dynamics of new electrode/electrolyte materials combined with different techniques, such as synchtron X-ray diffraction, X-ray absorption spectroscopy (XAS), neutron diffraction, High-resolution transmision microscopy and solid state NMR techniques. The investigated electrode/electrolyte systems include Ti-doped LiMn2O4, FeF3, Na3V2(PO4)2F3
, Zn2+-doped P2- Na0.66Ni0.33Mn0.67O2and Garnet-type electrolytes.

Acknowledgement: Financial support from National Natural Science Foundation of China ( Grant No. 21233004, 21473148, 21428303) are gratefully acknowledged

References

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S. H. Wang, et al ; J. Power Sources, 2014, 245, 570-578

W. Zhang, et al, J Phys. Chem.C, 2013, 117(22), 11498-11505

Z. G. Liu et al , Chem. Mater.; 2014, 26(8), 2513-2521

X. H. Wu, et al, to be submitted

D. W. Wang, et al Chem. Mater.; 2015, 27, 6650−6659
Layer Number Dependence of Li+ Intercalation on Few-Layer Graphene and Electrochemical Imaging of Its Solid-Electrolyte Interphase Evolution
Authors: Hui Jingshu , Burgess Mark , Zhang Jiarui , Rodríguez-López Joaquín
Published: February 2020

Bulk and surface electrochemical reactivity converge on ultrathin electrochemical interfaces such as few-layer graphene (FLG). In spite of the many recent works regarding the use of exfoliated graphene materials for charge storage, we still lack a detailed mechanistic understanding of how Li+ intercalates in FLG. Li+ intercalation in graphitic carbon is known to proceed through a staging mechanism, where intercalation occurs at selected interlayers at a time, rather than randomly on any available empty interlayer galleries, until reaching the nominal composition LiC6. Thus, on graphite this process is strongly dependent on the number of neighboring empty galleries at any given time. FLG naturally displays a limited number of galleries, therefore, we hypothesize that this process will also necessarily be distributed unevenly.

In this study, we applied FLG (1-10 layers) to explore the alkaline ion uptake mechanisms. Chemical vapor deposition methods with varies recipes were applied to grow double and multilayer graphene. By multicycle wet transfer of bilayer graphene, 2-8 layer graphene with well-defined area and low defect density. Direct growth of multilayer graphene (>10 layers) serves as control group. Photolithography method was used to generate micro patterns on graphene as “point of entry” for Li+intercalation.

Lithium ion intercalation on FLG, as measured via cyclic voltammetry, shows a staging-type process, which has strong dependence on the number of layers of graphene sheets that compose the electrode. On a graphene electrode with less than five layers, the numbers of intercalation/de-intercalation peaks were limited due to the lack of graphene interlayer galleries to stabilize Li ions. Those peaks broaden and increase in number as the layer number increases to six. Despite these mechanistic differences on ion intercalation, the formation of a solid-electrolyte interphase (SEI) was observed on all electrodes. Scanning electrochemical microscopy (SECM) in the feedback mode was used to demonstrate spatial resolved changes in the surface conductivity of FLG during SEI evolution. The fabrication of “ionic channels” on the FLG electrode provided preferential positions for Li ion insertion. The role of these channels can be evidenced using a Li-ion sensitive SECM imaging technique through localized flux measurements. This work highlights the impact of nano-structure and micro-structure on macroscopic electrochemical behavior and provides guidance to the mechanistic control of ion intercalation using atomically thin graphene interface.

Figure 1
Liquid Phase Scanning Electron Microscopy: A New Approach to Investigate Lithium Dendrite Formation in Liquid Electrolytes
Authors: Zhang Yuegang
Published: February 2020

Scanning electron microscopy (SEM) is a widely used tool for investigating the surface morphology of materials with a reasonable spatial resolution. Comparing with the high-resolution transmission electron microscopy (TEM), the beam-induced damage is much less in a SEM. With a proper scan rate, some relatively slow dynamic process, such as the lithium dendrite growth, can be observed in real time using a SEM. To mimic the real environment of a lithium battery, we designed a micro-liquid-electrochemical cell in which organic electrolytes could be introduced. We investigated the lithium deposition and dissolution processes in such a cell using electrolytes with different additives, and studied their effects on suppressing dendrite growth during lithium deposition. The results should shed light on developing more stable batteries using lithium metal as the anode material.
Investigation of Interfacial Phenomena of High-Voltage Li-Ion Battery with Li-Rich Layered Oxide Cathode
Authors: Pham Hieu Quang , Kwon Young-Gil , Hwang Eui-Hyung , Song Seung-Wan
Published: February 2020

Enabling the high energy density Li-ion batteries requires the use of high-capacity cathode material such as Li-rich layered oxide cathode (xLi2MnO3·(1-x)LiMO2 (M=Mn,Ni,Co)) that can be charged to high-voltage above 4.5 V vs. Li/Li+. A critical limiting factor for high-voltage battery operation is however the anodic and thermal instability of conventional electrolyte, which causes rapid performance fade and safety issue, in particular, at elevated temperatures. Our recent research results have shown that the use of functional additives enables the cell operation in such harsh conditions. Spectroscopic surface analysis data indicated that structural degradation of both Li-rich layered oxide cathode and graphite anode materials and instability of surface film at cathode during cycling in the conventional electrolyte were the main reasons for the rise of interfacial resistance and performance fade. Nonetheless, those problems can be resolved through interfacial stabilization using appropriate electrolyte additives. In this presentation, we report the interfacial phenomena and high-energy performance of Li-rich layered oxide cathode under a harsh condition of high charge cut-off voltage above 4.6 V vs. Li/Li+. The mechanistic studies of surface film/solid electrolyte interphase (SEI) layer formation and composition of cathode and anode using ex situ ATR FTIR spectroscopy combined with X-ray photoelectron spectroscopy and scanning electron microscopy, and structural changes using Raman spectroscopy, and the correlation between interfacial phenomena and high-voltage cycling performance would be discussed.