bluuebunny/crossref_metadata_2025_split huggingface dataset:
(Invited) Photoelectrochemical Water Splitting Devices By Electrochemical Processing
Authors: Xu Yin , Ahmed Rasin , Zangari Giovanni 
Published: February 2020

Photoelectrochemical (PEC) solar energy conversion utilizes sunlight to produce high purity hydrogen fuel via water splitting, thus providing clean energy on demand. In a PEC device at least one electrode (here the anode) is semiconducting in order to absorb radiation and generate electron/hole (e/h) pairs; holes are injected from the anode to the electrolyte, carrying out water oxidation, while electrons travel to the cathode, performing hydrogen reduction. In this talk we will discuss two distinct semiconductor photoanodes for solar water oxidation.
TiO2 nanotube arrays (NTs) made by electrochemical anodization are stable in operation and feature low cost, but the wide bandgap (3.2 eV) limits the photocurrent, and the low mean free path of the charge carriers increases recombination. In order to improve performance we carried out various modifications to the pristine material, including (i) Li intercalation to limit e/h pairs recombination[1], (ii) addition of electrocatalysts to amplify the water oxidation rate[2], (iii) formation of sub-stoichiometric TiO2-x by H2 annealing to enhance oxygen vacancies as active sites, or annealing in gaseous ammonia to implement nitrogen doping, resulting in visible absorption. All these modifications result in a significant increase in the PEC response, showing a sizeable cathodic shift of the photocurrent onset (~ 100 mV) and up to a 5-fold photoresponse increase at 1.23VRHE.
Gallium Arsenide (GaAs) on the other hand exhibits a direct bandgap of 1.43eV, resulting in efficient photon-to-electron conversion and excellent PEC performance. GaAs however suffers from fast photocorrosion in aqueous media, leading to semiconductor dissolution or oxidation. Electrodeposition of a thin Ni layer on GaAs using a chemistry that leads to self-terminating growth and affords continuous coverage at few nm thickness[3] provides a passivating layer through which electrons/holes may tunnel. The effect of Ni films of up to 4.4 nm on n-doped GaAs was studied; the dependence of thickness on the deposition time at 10 s and 60 s was observed via X-ray reflectometry, confirming growth inhibition during deposition. Ni-coated GaAs showed enhanced photocorrosion resistance compared to a bare GaAs substrate, while self-limiting Ni films on GaAs retains a high value of photocurrent (8.5mA cm-2 at 1.23V vs. RHE) compared to non-self-limited deposited sample (6.5 mA cm-2 at 1.23V vs. RHE), owed to a full coverage of the Ni layer and high photo-transmissivity due to a low coalescence thickness (~3.5nm).

References

[1] Tsui, L. K., Saito, M., Homma, T., & Zangari, G. (2015). Journal of Materials Chemistry A, 3(1), 360-367.
[2] Tsui, L. K., Xu, Y., Dawidowski, D., Cafiso, D., & Zangari, G. (2016). Journal of Materials Chemistry A, 4(48), 19070-19077.
[3] Vanpaemel, J. et al., (2015) Langmuir, 30, 2047–2053.
In-Situ SERS Analysis of SEI Formation at Graphite Electrode in Li Ion Battery Using Manipulated Plasmonic Sensor Element
Authors: Kunimoto Masahiro , Yanagisawa Masahiro , Homma Takayuki 
Published: February 2020

In order to improve the performance of Li ion rechargeable batteries, solid-liquid interfacial phenomena taking place at the electrode during the operation should be well understood. For example, detailed analysis of solid electrolyte interphase (SEI) thin films formed at the electrode surface, which plays the key role to determine the battery’s properties, is a crucial issue. We have developed precise spectroscopy technique using surface enhanced Raman scattering (SERS), to realize highly selective interfacial analyses [1,2]. Here, transparent micro lens, partially covered with nano particles of plasmonic metals, such as Ag, Au, etc., is an essential component, which is called as “plasmonic sensor”. The sensor situated onto a particular sample enhances Raman signals from its surface, allowing us to get information only about the chemical state of the surface.
To employ this technique for in-situ analysis of SEI film formation on the electrode surface in Li ion rechargeable battery, this study optimizes the equipment and employs it for the analyses of solvent species dependence of SEI properties. The organic solvents employed here were the mixture of ethylene carbonate (EC) and ethyl methyl carbonate (EMC) with 1:1 (volume), and that of propylene carbonate (PC) and EMC with 1:1. The graphite and LiCoO2 films were used for anode and cathode, respectively. 1.0 mol/L of LiPF6 was contained in each solvent. The design of plasmonic sensor implemented in the measurement cell was optimized so as to be movable by magnetic manipulation, which can avoid obstruction by the sensor to the diffusion of species during the reaction, realizing highly selective interfacial analyses. This setup was shown to serve also in effective Raman signal enhancement; the greater magnetic force to properly press down the sensor provides more significant signal enhancement. The SERS measurement results suggested that SEI formation depended on the solvent species employed: Li2O3 product was detected only in the case of PC-EMC. The time-dependent behavior of SEI formation was also obtained, indicating the mechanism of SEI formation.
Acknowledgements
This research was partially supported by the “Development of Systems and Technology for Advanced Measurement and Analysis”, and the “Research & Development Initiative for Scientific Innovation of New Generation Batteries (RISING 2)” from the New Energy and Industrial Technology Development Organization (NEDO) of Japan.
References:
[1] M. Yanagisawa, M. Saito, M. Kunimoto, T. Homma, Appl. Phys. Express, 9, 122002 (2016) .
[2] M. Kunimoto, Y. Sun, M. Yanagisawa, T. Homma, ECS Meeting Abstracts, MA2017-02, 131 (2017).
(Invited) Electrochemical Micromachining Based on Confined Etching
Authors: Zhan Dong-Ping , Han Lianhuan , Tian Zhong-Qun , Tian Zhao-Wu 
Published: February 2020

Micromachining is becoming the cutting-edge of high-tech manufacturing because of the increasing industrial demand for supersmooth surfaces and functional three-dimensional micro/nano-structures in microelectromechanical systems, ultra-large scale integrated circuits, miniaturized total analysis systems, precision optics and so on. Taking advantage of no tool wear, no surface stress, environmental friendliness, simple operation, and low cost, electrochemical micromachining (ECM) has an irreplaceable role in micromachining.
We present here our perseverant research in the last two decades on how to “confine” the ECM processes to occur at micrometer or even nanometer scale, that is, to ensure ECM with nanoscale accuracy. We have been developing the confined etchant layer technique (CELT) to fabricate three-dimensional micro- and nanostructures (3D-MNS) on different metals and semiconductor materials since 1992. In general, there are three procedures in CELT: (1) generating the etchant on the surface of the tool electrode by electrochemical or photoelectrochemical reactions; (2) confining the etchant in a depleted layer with a thickness of micro- or nanometer scale; (3) feeding the tool electrode to etch the workpiece. Scavengers, which can react with the etchant, are usually adopted to form a confined etchant layer. Through the subsequent homogeneous reaction between the scavenger and the photo or electrogenerated etchant in the electrolyte solution, the diffusion distance of the etchant is confined to micro- or nanometer scale, which ensures the nanoscale accuracy of electrochemical machining.
However, because the thickness of the electrolyte solution between the tool electrode and the workpiece are usually at micro/nano-meter scale, it is a challenge to solve the problems of potential distribution and mass transfer in the ultra-thin layer electrolyte cell. In this presentation, we will introduce our recent work on the external physical field induced electrochemical reactions in which there is no need of 2-electrode or 3-electrode system in the conventional electrochemical system.
Mathematical Modelling of the Electrochemical Degradation of Dyeing Wastewaters in Presence of Chloride Ion in a FM01-LC Reactor with Expanded Meshes Anodes (DSA)
Authors: Cruz-Díaz Martin Rogelio , Rodríguez Francisca Alicia , Rivero Eligio Pastor , González Ignacio 
Published: February 2020

In the present work a mathematical model to describe the indirect electrochemical oxidation of dyeing wastewaters in presence of chloride ion in a FM01-LC reactor in undivided mode coupled to Continuous Stirring Tank (CST) was implemented. The FM01-LC reactor was modeled with the Nernst-Planck equations in order to takes into account the dispersion, migration, and convection terms; the Poisson equations (through flow mode) for describe the potential distribution in solution, and the electro-oxidation (pseudo first order kinetic) of chloride ions in the anode side (CCl
-), the electrochemical reduction of chlorine oxidizing species (Cox) under mass transport control (mass transfer coefficient) in cathode side; while in the CST the chemical oxidation reactions between active chlorine species and organic matter through homogeneous second order kinetics were considered, which were evaluated through consumption of the chemical oxygen demand (CCOD) and the color decay (Ccol). The reactor operated as a batch recirculation system under galvanostatic conditions, the electrolyses were carried out at two current densities, 132 and 200 A m-2, with 1.0 mM of indigo carmine dye and 0.05 M of NaCl; four liquid flow rates: 0.9, 1.8, 2.7, and 3.6 L min-1 were used. As anode five titanium expanded meshes coated with IrO2-SnO2 doped with Sb2O5 and five stainless steel expanded meshes as cathode were used [1].
Figure 1(a) shows the simulation of the (a) chlorine oxidizing species (Cox) without the presence of dye, and the experimental and mathematical prediction: (b) the chloride ion, CCl
-, consumption; (c) the color, Ccol, removal, and (d) the chemical oxygen demand, CCOD, decay at four liquid flow rates: 0.9, 1.8, 2.7, 3.6 L min-1 and a current density of 132 A m-2 (i=5.0 A).
It can be observed that the proposed mathematical model describe adequately the experimental evolution of different chemical species (Cox, CCl
-, CCOD, and Ccol).

Figure 1
Anodic-like Wafer Bonding of Copper/Silicon Done at Room Temperature by Schottky Barrier Structure
Authors: Lee Benjamin T. -H. , Cheng Lin 
Published: February 2020

Metal, e.g. copper or aluminum, is difficult to be firmly bonded with silicon if only thermally treated at room temperature, because the surface status of the silicon substrate is usually in covalent bonds.
However, the low temerature Cu/Si bonding structure is usually achieved by pre-depositing Cu layer on the surfaces of the silicon at relative high temperature prior to bonding. In practice, this bonding is one type of copper-to-copper bonding. In this kind of bonding case, annealing temperature is normally at several hundred °C as well. Another way is to employ a so-called “low temperature” (400°C or below) thermo-compression bonding technique to create the Si/Cu structure. The first step is to deposit a Cu layer on the surface of blanket silicon wafer. Then, in practice, the two Cu surfaces were joined together with mechanical pressing and heating simultaneously for tens of minutes.
In the study, we demonstrated the copper-silicon bonding pair formed via an electrochemical processing at room temperature. The silicon substrates were double-side polished, phosphorus- doped, N-type (100) silicon wafer with resistivity of 1−10 Ω cm. The surface of copper plate was also polished. Prior to electrochemical processing, all the silicon specimens were cleaned at 80 °C in the following solutions: NH4OH:H2O2:H2O = 1:1:5 and HCl:H2O2:H2O = 1:1:6. Then silicon specimens were dipped in 0.5% HF solution for 30 seconds to remove all native oxide layer. Via a hydrophobic wafer bonding processing with HF dipping, the silicon specimen was bonded with the polished copper plate which is also as an anode electrode. The electrochemical anodization was performed in darkroom at a constant current density of 50 mA/cm2 with a platinum cathode in the electrolyte. After the electrochemical processing, we found copper was teared off and then firmly attached on the silicon surface when we tried to separate the bonded pair. We proposed that the carrier-mediated rectification through the Schottky junction of metal-semiconductor contact allows electrons drain to the copper electrode, thereby greatly increasing the hole density at the interface on the side of silicon substrate, i.e. activating the silicon dangling bonds. Once the electrons drained off to the copper electrode from silicon surface, the bonds formed on the Cu surface were also greatly activated to be bonded to silicon bonds. This kind of bonding technique of copper/silicon or metal/ceramic materials may be applied to the additive manufacturing for 3-D microstructure.
Figure 1: The copper layer was directly teared from bulk copper and then transferred onto silicon after electrochemical processing at room temperature for two hours. It appears the bonding strength between copper and silicon is stronger than the bond strength of copper.

Figure 1
Influence of Composition of SiCN Film for Surface Activated Bonding
Authors: Inoue Fumihiro , Peng Lan , Iacovo Serena , Phommahaxay Alain , Visker Jakob , Verdonck Patrick , Meersschaut Johan , Dara Praveen , Sleeckx Erik , Miller Andy , Beyne Eric 
Published: February 2020

Surface activated dielectric bonding is more and more attractive as a key technology to achieve further high-performance CMOS based devices independent on scaling. The major challenge of dielectric bonding is to decrease the process temperature in order to be compatible with CMOS processing. Although the conventional SiO2-SiO2 bonding has already been comprehensively investigated, there might be some limitations in terms of thermal budget. In the past, we have demonstrated low temperature bonding using PECVD-SiCN as interfacial layer, where we have obtained more than 2200 mJ/m2 of adhesion energy at 250 oC of post annealing temperature [1].
In this work, the composition of SiCN has been tuned aiming at the identification of the key elements taking part in the bonding mechanism and to further increase the adhesion energy.
The SiCN composition was successfully controlled by tuning the CVD deposition process, as it is proven by elastic recoil detection (ERD) measurements which enable us to monitor the ratio of the different elements (C,N,H,O, Si) in the different films. A table with ERD results is reported below. Also, the film densities are determined by using the mass differences of the processed wafers. The density becomes lower with increasing carbon concentration. The density variation impacts the CMP removal rate, which is critical for actual hybrid bonding process. On the other hand, no difference on the roughness is seen for all SiCN films.
After film planarization by CMP, wafer bonding test were done on 300 mm wafers by combining a pair of the same films as interfacial layer. Prior to bonding, N2 plasmas were applied on the both surfaces. No voids were observed for all the pairs, even after post bond annealing. The highest bonding strength is obtained from the carbon rich SiCN (SiCN #2). This indicates that the higher adhesion by SiCN may be attributed to the carbon dangling bond formed by plasma activation, rather than hydrogen or nitrogen.
Further mechanisms are discussed to understand the present low-temperature bonding technique.
[1] E. Beyne et.al., “Scalable, sub 2µm Pitch, Cu/SiCN to Cu/SiCN Hybrid Wafer-to-Wafer Bonding Technology” IEEE IEDM 2017, 32.4.1 (2017)

Figure 1
Pseudocapacitive Behavior of Polycationic Oxides for Electrochemical Capacitors
Authors: Crosnier Olivier , Goubard Nicolas , Buvat Gaëtan , Favier Frederic , Douard Camille , Brousse Thierry 
Published: February 2020

Electrochemical double-layer capacitors (EDLCs) represent the most important family of today’s commercially available Electrochemical Capacitors (ECs). Such systems can store charges electrostatically in the electrochemical double-layer that arises from the separation of charges at the electrode / organic electrolyte interfaces when polarizing the electrodes, and exhibit an excellent cycling stability combined with fair gravimetric and volumetric energy densities. Other types of ECs use “pseudocapacitive” materials, i.e. materials that use fast and reversible surface redox (faradaic) reactions to store energy. To combine the advantages of both organic EDLCs and aqueous symmetric systems, the design of aqueous asymmetric supercapacitors was proposed. These devices comprise either two pseudocapacitive materials, or a pseudocapacitive and a capacitive carbon-based material which exhibit complementary electroactive windows. As a result, operating cell voltages approaching 2 V can be obtained, leading to competitive energy densities without the disadvantages of using an organic electrolyte.
Both specific energy and power densities have to be increased and improving the volumetric capacitance of supercapacitors, which is one of the limiting factors of today’s stationary applications, is essential. In order to meet these requirements, solid state chemistry is an powerful tool to design new materials. Our strategy was based on the study of polycationic oxide materials. They can combine transition metals such as Fe or Mn, that are known to be electrochemically active in aqueous media, with dense elements such as W, Bi,… The Fe/W/O has a peculiar interest since our recent studies have shown that FeWO4 exhibit excellent electrochemical properties [1,2]. Its pseudocapacitive behaviour has been demonstrated by operando XAS experiments with the use of a special cell designed in our lab [3].
The use of low-temperature synthesis methods in order to get nanosized particles with high specific surface areas is also required. Synthesis conditions and materials characterizations of the electrodes and also of full devices will be detailed in the presentation, highlighting the crucial role of the electroactive elements, the crystallographic structure, and the morphology of the synthesized materials on their electrochemical performance.
[1] N. Goubard-Bretesché, O. Crosnier, C. Payen, F. Favier, T. Brousse, Electrochem.
Commun. 57 (2015) 61.
[2] N. Goubard-Bretesché, O. Crosnier, F. Favier, T. Brousse, Electrochim. Acta 206 (2016), 458.
[3] N. Goubard-Bretesché, O. Crosnier, C. Douard, A. Iadecola, R. Retoux, C. Payen, F. Favier, M.-L. Doublet, T. Brousse, in preparation.
A New Type of Tetragonal LixMn2O4 Electrode Exhibiting Combined Pseudocapacitance and Battery Behaviors and Self-Healing Cycle Stability in Aqueous Electrolytes
Authors: Abdollahifar Mozaffar , Wu Nae-Lih 
Published: February 2020

Among several energy storage technologies, supercapacitors have achieved considerable attention because of their rapid charge-discharge rates, high power density, and excellent cycling stability, but low energy density and fast self-discharge are some of serious disadvantages for the supercapacitors. Electrodes with combination of battery and pseudocapacitance behaviors offer the advantages of both supercapacitors and the advanced batteries, it shows higher energy density and the same time maintains the extended cycle life and fast charge capability. In this study, a new type of tetragonal LixMn2O4 (LMO) electrode exhibiting combined pseudocapacitance and battery behaviors in aqueous electrolytes has been synthesized by electrochemical cation-exchange conversion from ZnMn2O4 (ZMO) [1]. It is shown that the Zn+ ion in ZMO can be replaced by the Li+ ion, resulting in the formation of LMO in aqueous Li2SO4 electrolytes by cyclic voltammetry. The resulting LMO electrode is in tetragonal structure but yet exhibits redox potentials essentially the same as those of the cubic LMO (Fig. a), delivering a redox capacity over 100 mAh/g under low current rate or a specific capacitance of nearly 300 F/g when behaving as a pseudocapacitor at higher current rates. Despite its tetragonal structure, the electrode shows outstanding cycle stability, exhibiting an interesting self-healing structure transformation process to the cubic structure and retaining 100% capacity after 40, 000 cycles. Using the high-concentration LiTFSI electrolyte enables the expansion of operating potential window to 1.55 V. The material synthesis process and charge-transfer mechanism are characterized in detail.
[1] M. Abdollahifar, S.S. Huang, Y.H. Lin, Y.C. Lin, B.Y. Shih, H.S. Sheu, Y.F. Liao, N.L. Wu, J. Power Sources 378, 90, 2018.

Figure 1
(Invited) Atomic Layer Processing from an Etching Perspective
Authors: Lill Thorsten , Berry Ivan , Fischer Andreas , Shen Meihua , Vahedi Vahid 
Published: February 2020

Atomic Layer Etching (ALE) transitioned to manufacturing because of unique performance benefits which come from self-saturation of the steps and the use of very low ion energies or just thermal means to remove material. The former property gives uniformity across all lengths scales on the wafer. Reduced aspect ratio dependent etching (ARDE) and surface smoothness are very attractive benefits. Low level removal energies deliver selectivity which is a key requirement for etching with atomic scale fidelity.
In this talk, a conceptual framework for directional and isotropic ALE will be compared to other etching technologies for semiconductor devices. Recent experimental and theoretical results as well as applications examples will be presented to illustrate the concepts.
(Invited) Atomic/Molecular Layer Deposition for Thin-Film Lithium-Ion Batteries
Authors: Nisula Mikko 
Published: February 2020

All-solid-state thin-film batteries are seen as viable technologies for powering a wide variety of miniature electronic devices, for instance microelectronics, medical implants, and radio-frequency identification tags, due to their safety, and flexibility in size and design. In order to increase the energy density while preserving the power density of the cells, increasing the effective surface area through microstructuring of the substrate is seen as a promising option. This concept of all-solid-state 3D-microbattery places an apparent need for a thin-film deposition method capable of manufacturing the electrode and electrolyte materials on high aspect ratio substrates; a formidable challenge given the limitations of the currently used thin-film deposition methods. A strong candidate for the task is the atomic layer deposition (ALD) technique, which is based on sequential surface reactions of gaseous precursors. The surface saturation limited growth results in excellent conformality over complex surface features. As the basic research on new ALD processes for Li-containing thin films is only in early stage, the true impact of the ALD technique in the Li-ion battery field is yet to be demonstrated.
This talk focuses on the use of ALD on depositing lithium-containing materials and on the aspects of manufacturing an all-ALD thin-film battery. As the all-solid-state thin-film layout enables unconventional approaches, a special emphasis is placed on fully organic electrode materials. Conjugated carbonyls are a promising group of redox active materials that in conventional bulk-format batteries suffer from solubility issues as well as from their inherently poor electronic conductivity. Here, the all-solid-state thin-film setup should mitigate both issues allowing for the full utilization of their perceived high redox reaction kinetics. The deposition of both positive and negative electrode materials is demonstrated by utilizing the combined atomic/molecular layer deposition (ALD/MLD) technique. In comparison to the conventional inorganic materials, this approach allows for simple, binary deposition processes, low deposition temperatures, and environmentally benign constituents. As well as enabling ultrafast redox kinetics, the thin-film approach might provide new information on the conduction mechanisms of the conjugated carbonyl based materials.