bluuebunny/crossref_metadata_2025 huggingface dataset:
Application of Double Resonance Sum Frequency Generation Spectroscopy to Characterize the Interfacial Electronic and Molecular Structure in Electrochemical Environment
Authors: Noguchi Hidenori , Yang Shuo , Uosaki Kohei
Published: February 2020

Absorbed CO on Pt surface has attracted much interest among scientists in surface science, catalysis, and electrochemistry. Information about oxidation mechanisms of CO on Pt, which depends on geometric and electronic structures of CO/Pt interface, is important to design and develop new catalysts for various reactions including H2-O2 and direct methanol fuel cells. Small amount of CO present in H2 produced from fossil fuel readily adsorbs on Pt and inhibits H2 oxidation. Adsorbed CO is also formed when Pt is in contact with methanol solution and inhibits the methanol oxidation reaction. Compared to extensive study on CO/Pt system under ultrahigh vacuum (UHV), interfacial electronic structure of CO/Pt interface in electrochemical environment is less understood due to the difficulty in determining it in solution. Accordingly, it is very important to investigate interfacial electronic structure of CO/Pt under electrochemical condition. Because of the presence of solution, it is not possible to use techniques with electron probes, which are most powerful in UHV. Double resonance sum frequency generation (DR-SFG) spectroscopy, which is a highly surface-sensitive nonlinear optical technique with the tunable frequencies of both incident fundamental lights, i.e., visible and IR, can provide information of surface molecular and electronic structures, which is not obtained by traditional surface vibrational technique. Here, we employed DR-SFG technique to probe potential-dependent electronic structure of CO/Pt interface in methanol solution. SFG signal due to C-O stretching was observed and was dependent on frequency of visible light as a result of the energetic coupling of electronic transition with the input visible photon and/or output SF photon, i.e., double resonance effect. Furthermore, resonant visible energy linearly depended on electrode potentials. Thus, the electronic resonance could be explained by the transition from Fermi energy, Ef, of Pt to the unoccupied 5anti-bonding state of CO.
Electron Transfer Kinetics at Co Porpyrin-Modified Electrodes with Controlled Interfaces
Authors: Ikeda Katsuyoshi , Sato Shino
Published: February 2020

Electrocatalysis has been extensively studied in the fields of both fundamental research and applications such as fuel cells. Chemical modification of an electrode surface is quite beneficial to non-catalytic metals to introduce catalytic activity for a particular electrochemical reaction. For example, metalloporphyrin-modified electrodes are known to act as electrocatalysts for oxygen reduction reaction (ORR). Chemical design of molecular catalysts is clearly one of key issues to realize highly efficient electrocatalysts. However, the electron transfer rate at such a chemically modified electrode is significantly affected by electronic coupling between the metal and molecular catalysts. In this work, a gold electrode surface was self-assembly modified with Cobalt porphyrin (CoTPP) having ORR activity. To control the connection between Au and CoTPPs, bridge monolayers were formed on the electrode using various thiol- or isocyanide-molecules, and CoTPPs were then immobilized on top of the bridge layers. For isocyanide-monolayers, the electrode-molecule junctions were also controlled by forming Pd- or Pt-atomic layers on the Au surface. The electron transfer rate for ORR was thoroughly investigated for such various CoTPP-modified electrodes using the rotating disk electrode (RDE) method.

The junction between the electrode and the molecular monolayers was controlled as shown in Fig. (a). The Pd monoatomic layer on an Au surface (Au/PdML) was prepared by the underpotential deposition (UPD) method. The Au and Au/PdML electrodes were self-assembly covered with TPDI (4,4’-terphenyl diisocyanide) molecules. As shown in Fig. (b), the adsorption geometry of TPDIs, measured by PM-IRRAS, was on-top configuration on Au and bridge on Au/PdML. The 2120 cm-1 peak found on both electrodes was attributed to be the unbound NC streching mode. Figure (c) shows Tafel plots for ORR on the TPDI-CoTPP monolayer formed on each electrode. Electron transfer rate on the Au/PdML was much faster than that on the Au. The elementary step of the electron transfer between O2molecule and CoTPP is not affected much by the presence of the Pd monolayer, as the Tafel slop is nearly identical for both plots. Therefore, this result indicates that the electron transfer rate at the electrode-molecule interface was significantly enhanced by controlling the adsorption geometry, leading to the enhancement of the ORR activity of the electrode.

Figure (a) Schematic illustration of TPDI-CoTPP monolayers on metal electrodes. (b) PM-IRRAS spectra of TPDI-SAMs on Au and Au/PdML electrodes. (c) Tafel plots for the ORR on TPDI-CoTPP monolayer formed on Au and Au/PdML electrodes.
Modifying Oxide Single Crystal Surfaces to Study Photoinduced Electron Transfer
Authors: Parkinson Bruce A
Published: February 2020

Single crystal oxide semiconductor electrodes provide an ideal experimental system for the elucidation of the models and parameters that control light absorption, charge separation, and transport at semiconductor/liquid interfaces. Such fundamental investigations can prove very valuable in the understanding of dye sensitized nanocrystalline solar cells. The single crystal experimental system is much less complex than its nanocrystalline counterpart and the study of well-defined crystallographic surfaces allows for more definitive conclusions to be made concerning the relation between sensitizer attachment and surface structure and the sensitizer’s performance. I will report recent work on the sensitization of low index faces of both anatase and rutile forms of TiO2 and ZnO single crystals with dyes, quantum dots and polymers. We employ atomic force microscopy (AFM) to verify that atomically flat terraced oxide surfaces are prepared and to elucidate the structure of the sensitizers adsorbed on these surfaces. Photocurrent spectroscopy and attenuated reflection spectroscopy are used to correlate the photocurrent response with the optical absorption of the sensitizing species and the relative electron injection efficiencies of for instance dye monomers and aggregates. We have also recently begun to grow homoepitaxial layers on both anatase and rutile using atomic layer deposition (ALD). These layers can have superior electronic properties compared to the substrate crystal and allows us to control the doping density in the near surface region. The primary focus of this talk will be on CdSe and PbS quantum dots as sensitizers. PbS quantum dots adsorbed on anatase (001) surfaces irradiated with light of >2.5 times their band gap have been shown to produce more than one injected electron per incident photon (1), a process known as carrier multiplication or multiple exciton generation (MEG). Harnessing MEG may result in more efficient solar conversion devices.

1. Justin B. Sambur, Thomas Novet and B. A. Parkinson, “Multiple Exciton Collection in a Sensitized Photovoltaic System”, Science, 330, 63-66, (2010)
Electrochemical Characterization of a 2-Hydroxypropyl b-Cyclodextrin Membrane with Tenoxicam
Authors: Guzmán-Hernández Dafne Sarahia , Ramirez-Silva Maria Teresa , Palomar-Pardavé Manuel , Romero-Romo Mario A. , Corona-Avendaño Silvia
Published: February 2020

The electrochemical characterization of an nonsteroidal anti inflammatory drug named Tenoxicam was performed with a carbon paste electrode modified with 2-hydroxypropyl b-cyclodextrin, that led to observing a single oxidation peak for the different Tenoxicam species without reduction processes, which involved an adsorption process as responsible for the formation of the single, fine oxidation peak.
Electrochemical Behaviour of Dissolved Iron Chloride in KCl+LiCl+NaCl Melt at 550ºC
Authors: Khalaghi Babak , Kvalheim Eirin , Tokushige Manabu , Teng Lidong , Seetharaman Seshadri , Haarberg Geir Martin
Published: February 2020

Knowing the electrochemical behaviour of metallic ions in molten salts is crucial for electrometallurgical processes [1]. These processes include both extraction of metals from primary sources and recovery from wastes. Recently there has been a growing interest in developing an electrolytic process for iron production [2-3]. Furthermore, while an electrolytic process is used for treatment of wastes, iron is quite often present. Although, many studies have been done on iron in chloride melts [4-6], it seems little attention has been paid to FeCl3 behaviour and stability in these electrolytes.

In this study the electrochemical behaviour of iron in a salt bath composed of KCl+LiCl+NaCl was studied at 550°C by cyclic voltammetry and chronoamperometry. The working electrode was glassy carbon and iron was introduced to the melt by adding dehydrated FeCl3. Although FeCl3 is not fully stable in these types of solutions, both FeCl2 and FeCl3 showed to exist in the salt bath. Based on cyclic voltammograms the Fe (II)/Fe (0) electron exchange is a soluble/insoluble diffusion controlled process, although it cannot be considered fully reversible. The nucleation of metallic iron on glassy carbon electrode showed instantaneous characteristics. From the cyclic voltammetry results, the calculated value for Fe (II) diffusion coefficient is equal to 1.4×10-5 cm2 s-1. Although FeCl3 is not fully stable in these types of solutions, the Fe (II)/Fe (III) exchange reaction was observed at potentials near the chlorine evolution reaction. The oxidation of Fe (II) to Fe (III) is followed by a chemical reaction consuming the as generated FeCl3 ions. The equilibrium between FeCl3 and FeCl2 is also briefly discussed.

References:

D. Inman, S.H. White, The production of refractory metals by electrolysis of molten salts design factors and limitations, Journal of Applied Electrochemistry 8 (1978) 375.

G.M. Haarberg, E. Kvalheim, S. Rolseth, T. Murakami, S. Pietrzyk, S. Wang, Electrodeposition of Iron from Molten Mixed Chloride/Fluoride Electrolytes, ECS Transactions 35 (2007) 341.

D. Wang, A.J. Gmitter, D.R. Sadoway, Production of oxygen gas and liquid metal by electrochemical decomposition of molten iron oxide, Journal of the Electrochemical Society, 158 (2011) 51.

D. Inman, J.C. Legey, R. Spencer, A chronopotentiometric study of iron in LiCl-KCl, Journal of Applied Electrochemistry 8 (1978) 269.

Y. Castrillejo, A.M. Martínez, M. Vega, P. Sanchez Batanero, Electrochemical reduction of Fe(II) ions on different solid electrodes in fused ZnCl2-2NaCl mixture, Journal of Applied Electrochemistry 26 (1996) 1279.

A. Lugovskoy, M. Zinigrad, D. Aurbach, Z. Unger, Electrodeposition of iron(II) on platinum in chloride melts at 700–750°C, Electrochimica Acta 54 (2009) 1904.
Electrodeposition of Mg-Ni-Al Alloy in Low Temperature Molten Salts
Authors: Xu Junli , Zhang Xia , Shi Zhongning , Haarberg Geir Martin
Published: February 2020

Mg-Al-Ni alloys were prepared in urea-acetamide-NaBr low temperature molten salts by electrodeposition method. The results show that Mg2+ could not be electrochemically reduced in this molten salt independently. However, it could be co-deposits with Ni. Effects of electrodeposition parameters such as temperature and electrodeposition time on the composition and microstructure of coatings were investigated. Also, the kinetic process was investigated using electrochemical methods.
The Utilization of Ionic Liquid Technology for the Degradation of Biopolymers
Authors: Reichert William Matthew , Goodie Taylor , Pischek Andrew M , Stenson Alexandra C. , Gayton Jacqueline
Published: February 2020

Chitin, a polymer of N-acetyl-D-glucosamine, is the second most abundant in the world and makes up the exoskeleton of various arthropods and cell walls in various fungi. The structure of chitin makes it insoluble in common solvents and hinders development of applications of chitin. With the discovery that ionic liquids can dissolve chitin, the restrictions on the utilization of this unique biopolymer have been removed.

Like traditional salts, ionic liquids (ILs) are compounds composed entirely of ions. However, unlike traditional salts, ILs are composed of bulky ions, commonly large organic cations paired with either organic or inorganic anions. The size of the ions leads to a decreased melting point for the ILs, defining them as a compound composed entirely of ions with a melting point below 100°C. In addition to possessing lower melting points, ILs have demonstrated unique physical and chemical properties. Among these properties are a large liquid range, low vapor pressures, low flammability, and the ability to dissolve a variety of materials. These properties make ILs appealing to use in various chemical processes.

The unique property of ILs that is of interest to this research is their ability to dissolve various biopolymers, such as cellulose and chitin.1-4 The dissolution of these biopolymers has opened up new areas of research, including efficient degradation and processing the biopolymers for new materials. This study will investigate the effects of alkyl chain tether on catalyst behavior. This research will also observe the effects from varying the anion, temperature, and catalyst loading as well as utilizing minerals acids instead of IL catalysts.

(1) Qin, Y.; Lu, X.; Sun, N.; Rogers, R. D. Green Chemistry
2010, 12, 968.

(2) Xie, H.; Zhang, S.; Li, S. Green Chemistry
2006, 8, 630.

(3) Swatloski, R. P.; Rogers, R. D.; Holbrey, J. D. 2002, p 59.

(4) El Seoud, O. A.; Koschella, A.; Fidale, L. C.; Dorn, S.; Heinze, T. Biomacromolecules
2007, 8, 2629.
Electroreduction of Oxygen on Electrochemically Deposited Palladium-Gold Alloys on Glassy Carbon
Authors: Erikson Heiki , Sarapuu Ave , Kozlova Jekaterina , Matisen Leonard , Sammelselg Väino , Tammeveski Kaido
Published: February 2020

In pursuit to find cheaper alternative catalyst material to replace platinum in low temperature fuel cells palladium has gained much attention due to the similar properties with Pt.1 Previously we have shown that electrodeposited palladium has higher electrocatalytic activity towards the oxygen reduction reaction (ORR) on gold substrate than on glassy carbon.2,3

The aim of this work was to study how gold supplement affects the ORR activity on electrodeposited palladium. In order to achieve this goal palladium and gold were co-deposited onto glassy carbon (GC) substrate at a constant potential. The precursor concentration ratio was varied in deposition solution to achieve different Au-Pd coatings. The surface morphology of Pd-Au alloys was studied with scanning electron microscopy and it was observed that the particle size does not change with changing palladium-to-gold ratio. Though there were some larger agglomerates but the average particle size was approximately 10 nm.

Electrochemical experiments were carried out in sulfuric acid and in potassium hydroxide solutions. From cyclic voltammograms the features of Pd and Au were observed.

The rotating disk electrode (RDE) method was employed for the oxygen reduction studies. In acid media the ORR activity depended strongly on palladium content and the half-wave potential of O2 reduction shifted positive with increasing Pd content in the deposition bath (Fig. 1a). The Tafel analysis was carried out which showed that the rate determining step is the sluggish transfer of first electron to O2 molecule (Fig. 1b). In alkaline media palladium and gold are both more active than in acid solution (Fig. 2a). The polarization curves of O2reduction for the Pd-Au coatings were similar whereas the ORR activity only slightly decreases with decreasing Pd content in the deposition bath. The Tafel behavior of ORR in alkaline solution is shown in Fig. 2b.

The RDE data were used to carry out the Koutecky-Levich analysis which showed that O2 reduction proceeds mainly through 4-electron pathway with some additional peroxide formation in sulfuric acid. The number of electrons transferred per O2 molecule (n) did not depend on potential for Pd-Au coatings, in contrast to bare gold electrode for which the value of n depends on potential.

In addition to the oxygen reduction studies, the process of hydrogen peroxide reduction in alkaline media has been also explored. The activity for peroxide reduction did not depend on the Pd content in the catalyst. The polarization curves were similar for all the Pd-Au coatings studied.

References

1. E. Antolini, Energy Environ. Sci., 2, 915, 2009.

2. H. Erikson, M. Liik, A. Sarapuu, M. Marandi, V. Sammelselg, and K. Tammeveski, J. Electroanal. Chem.,
691, 35, 2013.

3. H. Erikson, M. Liik, A. Sarapuu, J. Kozlova, V. Sammelselg, and K. Tammeveski, Electrochim. Acta,
88, 513, 2013.
Novel Non-Carbon Support Compositions and Architectures: Elaboration, Characterisation, Integration and Fuel Cell Testing
Authors: Jones Deborah J , Roziere Jacques , Cavaliere Sara , Subianto Surya
Published: February 2020

One of the major issues concerning durability of PEMFC (Proton Exchange Membrane Fuel Cells) is the electrode degradation over time. Indeed, conventional electrocatalyst supports, based on carbon blacks, in fuel cell conditions suffer from corrosion leading to the aggregation, migration and detachment of the electrocatalyst nanoparticles with loss of performance. One strategy to overcome this issue is the replacement of carbon with more (electro)chemically stable supports. Recently, materials such as conducting oxides, nitrides and carbides have been shown promising applications as alternative supports. We are currently developing novel nanofibre and nanoparticle based PEMFC electrodes using non-conventional materials including niobium, tantalum and tungsten carbides, and doped titanium and tin oxides.

The challenges to be addressed are related to the development of nanofibres and nanoparticles having sufficient surface area to support and well disperse the electrocatalyst nanoparticles, while ensuring adequate electronic conductivity. We will review current progress in this area, and focus on morphology and physical-chemical properties of non-carbon supports prepared by electrospinning and hydrothermal methods, and the challenges of electrode development from them. Electrocatalytic activity of these systems will be addressed, in particular towards the oxygen reduction reaction, and the results of testing under accelerated ageing protocols will be described in order to compare their resistance to corrosion to that exhibited by conventional carbon based supports and assess their greater stability, and to underline the importance of a strong catalyst support interaction.
The Electro-Oxidation of H2, CO in a Model PEM Fuel Cell: Oscillations, Chaos, Pulses
Authors: Kirsch Sebastian , Hanke-Rauschenbach Richard , Sundmacher Kai
Published: February 2020

H2, CO electro-oxidation in a model PEM Fuel Cell (PEMFC) is investigated at 37°C with the help of distributed current measurements. The main purpose of the experiments is to verify the formation of spatio-temporal patterns that have been predicted for a PEMFC with straight channels and a H2evolving cathode. For galvanostatic operation and a high feed flow rate well expressed globally coupled oscillations are found. For decreasing feed flow rate a period doubling bifurcation cascade appears. Potentiostatic control provokes the breakage of the strict phase relation between adjacent oscillators and the appearance of pulses as well as turbulence is seen. The turbulence is enhanced if an oxygen reducing cathode is introduced instead of a hydrogen evolving cathode. The findings are compared to existing predictions. The study of the patterns is of interest for PEMFC engineers as they directly determine the CO tolerance behavior of the PEMFC.

[1] R. Hanke-Rauschenbach et al. J. Electrochem. Soc. 157, B1521 (2010).

[2] S. Kirsch et al. J. Electrochem. Soc. 158, B44 (2011).

[3] S. Kirsch, et al. J. Electrochem. Soc. 160, F436 (2013).

Figure caption: Upper row - The segmented anode flow field with 80 segments per channel (channel length: 14.4 cm). The both inner channels are used for current distribution measurement, while the outer channels serve for homogenization. Each segment consists of two sub-segments that face across the channel. Lower row - As seen in the spatio-temporal plots of the measured current signal (corrected for its temporal space dependent average), the system behaves chaotically after a step into the voltage regime at which CO can be oxidized. In this potentiostatic experiment, the cathode was fed with air.
Electrochemical Micro-Oscillator Networks
Authors: Jia Yanxin , Kiss Istvan Z
Published: February 2020

Stationary and oscillatory patterns can arise on the surface of a single electrode [1] and assemblies of discrete electrodes [2]. In traditional macrocells, the geometry of the arrangement of the cathode, anode, and the reference electrodes determines the strength and length-scale of the effective coupling that affects the features of the observed self-organized pattern formation.

To explore the temporal and spatial features of pattern formation in electrochemical devices with micro-electrodes, we have constructed epoxy-embedded electrodes with a poly-dimethyl siloxane (PDMS) flow cell. [3-4] It is shown that the microcell design typically used in electroanalytical chemistry produces large ohmic drops that can induce oscillations during the uniform corrosion of Ni electrodissolution.

Furthermore, the dynamical features of oscillatory Ni dissolution in sulfuric acid are investigated with 2-10 micro-electrode arrays. Equivalent circuit analysis is applied to formulate a theory for the electrical coupling strength between the electrodes as a function of the cell parameters: electrode surface area, length of the flow channel, and total cell resistance. The theory predicts a wide range of bidirectional positive, unidirectional negative, or unidirectional positive coupling depending on cell geometry. The predictions are tested in experiments with an on-chip integrated electrochemical cell that uses an epoxy-based substrate for 2-10 embedded metal wires with the PDMS fluidics. The network topology is extracted from the experiments with a phase model based coupling analysis. The results are discussed and design rules are formulated for tuning the dynamical characteristics of the chemical reaction system through intensifying or minimizing the coupling strength between the electrodes.

[1] K. Krischer, Principles of temporal and spatial pattern formation in electrochemical systems, in: B.E. Conway, O.M. Bockris, R.E. White (Eds.) Modern Aspects of Electrochemistry, vol. 32, Kluwer Academic, New York, 1999.

[2] I.Z. Kiss, T. Nagy, V. Gáspár, Dynamical Instabilities in Electrochemical Processes, in: V.V. Kharton (Ed.) Solid State Electrochemistry II, Wiley-VCH, Weinheim, 2011.

[3] I.Z. Kiss, N. Munjal, R.S. Martin, Electrochim. Acta, 55 (2009) 395-403.

[4] A.G. Cioffi, R.S. Martin, I.Z. Kiss, J. Electroanal. Chem., 659 (2011) 92-100.
Rotational Waves in Rings of Electrochemical Oscillators
Authors: Sebek Michael L , Kiss Istvan Z
Published: February 2020

Chemical and biological systems exhibit network properties dependent upon the behavior of individual units and the interactions between units.[1] The presence or absence of interactions and the strength of the interactions determine the topology of the network and in turn the network properties. From a mathematical perspective, a variety of non-rotating and rotating waves can exist for a ring of locally coupled units[2] and the non-rotating solutions are the dominant outcome when coupling is the only mean of interactions regardless of the initial conditions.[3] Therefore, engineering is required to achieve solutions aside from the dominant non-rotating state.

The formation of waves is examined in oscillatory nickel dissolution where units of individual oscillators interact through external resistance which controls the strength of interaction. An experimental technique using a locally coupled twenty nickel electrode ring is presented in which through a combination of temporary alterations in topology and the application of global feedback provides all possible rotational solutions.

There are four rotational waves which can propagate about the ring and are distinguished by the velocity and the number of waves. The propagation rate is inversely proportional to the number of waves in the rotation (m) for all rotations. Solutions with no rotation have an m value of zero while rotational solutions are obtained for m=1,2,3,4. Larger m values (m ≥ 5) are shown to not be stable in the network. The results thus indicate that while network plasticity is thought to be significant in the operation of neural systems, it can also play a role in pattern selection of chemical systems.

References:

[1] J. L. Hudson, I. Z. Kiss, H. Kori, C. G. Rusin, Science 2007, 316, 1886-1889.

[2] G. B. Ermentrout, J. Math. Biol. 1985, 23, 55-74.

[3] D. A. Wiley, S. H. Strogatz, M. Girvan, Chaos 2006, 16, 1054-1500.
Perylenediimide-Graphene Donor-Acceptor Nanoensembles: Synthesis, Characterization and Photophysics
Authors: Karousis Nikolaos , Martin-Gomis Luis , Ohkubo Kei , Hasobe Taku , Sastre-Santos Angela , Fukuzumi S. , Tagmatarchis Nikos
Published: February 2020

Graphene is an outstanding material, consisting of a two-dimensional (2D) single layer of sp2-hybridized carbon atoms bonded together in a hexagonal “honeycomb” lattice and presents remarkable electronic and mechanical properties, like quantum hall effect at room temperature, an ambipolar effect along with ballistic conduction of charge carriers, tunable bandgap and high elasticity.1 These exceptional properties of graphene make it an ideal candidate in construction of transparent conducting electrodes that could be used in energy conversion and storage systems. However, the preparation of high quality few-layered graphene materials is still an issue that must be circumvented and solvent assisted exfoliation using flat aromatic organic molecules as exfoliating assistants reveals as an extraordinary tool for that purpose.2

Herein, we present the liquid exfoliation of graphite to few layered graphene sheets together with the non-covalent supramolecular functionalization of exfoliated graphene sheets by the custom synthesized 1-N-methylpiperazinyl-N,N’-di(2-ethylhexyl)-perylene-3,4,9,10-tetracarboxydiimide (Pip-PDI).3 The planar aromatic Pip-PDI has the ability to non-covalently interact with exfoliated graphene sheets, stabilizing them and preventing their reassembly. On the other hand, the presence of the piperazine moiety on the bay position of the PDI core in the Pip-PDI makes it an ideal electron donor, nicely coupled with electron accepting exfoliated graphene, hence forming a novel donor-acceptor nanoensemble. The new PDI-graphene ensemble was characterized by complementary spectroscopic and microscopy techniques. Furthermore, electronic communication between the counterparts of the PDI-graphene nanoensemble was identified and probed by photophysical and redox assays, while prototype photoelectrochemical cells were constructed and evaluated.

Financial support from GSRT/NSRF 2007-2013 through action “ARISTEIA ΙΙ” project FUNGRAPH (3150) and CTQ2011-26455 and Prometeo 2012/010 is acknowledged.

References

A. K. Geim, K. S. Novoselov, Nat. Mater.
2007, 6, 183.

S. P. Economopoulos, N. Tagmatarchis, Chem. Eur. J. 2013, 19, 12930.

N. Karousis, L. Martin-Gomis, K. Ohkubo, T. Hasobe, A. Sastre-Santos, S. Fukuzumi, N. Tagmatarchis, Manuscript in preparation, 2014.
On-Chip Micro-supercapacitors Based on Nanoporous-Gold/ MnO2 Hybrid Electrodes
Authors: Zeng Zhigang , Zhou Haijun , Long Xiao , Hu Zhiyu
Published: February 2020

Development of miniaturized electronics has stimulated demand for integration of energy storage units with electronic circuits. Micro-supercapacitors can be a promising strategy for future application in microelectric devices because of their properties of high power density, high-rate capability, long lifetime and high-frequency response. Progress in micro-fabrication technology has enabled on-chip micro-supercapacitors in an interdigitated planar form be compatible with integrated circuit. From a material perspective, nanostructured carbon-based materials are commonly used in electric double-layer micro-supercapacitors. In addition, transition metal oxides such as ruthenium oxide and manganese oxide, and some conducting polymers such as polypyrrole and polyaniline have been used as electrodes for pseudo-capacitive micro-supercapacitors.

MnO2-based pseudocapacitive electrodes have been considered as a promising candidate because of their high theoretical specific capacitance (1,370 F/g), environmentally friendly nature and low cost of raw materials. The main drawback of MnO2 is that the poor conductivity may limit the charge/discharge rate for high-power applications. However, Lang et al. have show that hybrid structures made of nanoporous gold and nanocrystalline MnO2 have enhanced conductivity, resulting in a specific capacitance close to the theoretical value (~1,145 F/g)[1]. The nanoporous gold not only plays a role as a double-layer capacitor, but also promotes electron transport through the MnO2 and benefits fast ion diffusion between the MnO2 and the electrolytes. Besides, the excellent mechanical properties enable nanoporous gold to be amenable to micro-fabrication processes[2]. The high specific capacitances and charge/discharge rates offered by such nanoporous gold/MnO2 hybrid structures make them promising candidates as electrodes in micro-supercapacitors.

Herein, we make our efforts in preparing high-performance nanoporous gold/MnO2 hybrid electrodes by electrodepositon method and fabricating micro-supercapacitors in interdigitated planar form. Our electrodeposited nanoporous gold/MnO2hybrid electrodes also have a specific capacitance close to the theoretical value (>1,000 F/g). The preparation and performance of hybrid electrodes and micro-supercapacitors will be presented.

1. Lang, X.Y., et al., . Nature Nanotechnology, 2011. 6(4): p. 232-236.

2. Jin, H.J. and J. Weissmüller, Science, 2011. 332: p. 1179-1182.
Enhanced Visible-Light Photoelectrochemical Performance of Titana Nanotubes Modified by Atomic Layer Deposited Cobalt Oxide
Authors: Huang Bin , Wen Yanwei , Shan Bin , Chen Rong
Published: February 2020

TiO2 is widely considered as one of the promising materials to fulfill photoelectrochemical water splitting requirements for its low cost, nontoxicity, photostablity, and strong photo oxidation ability. Several synthesis approaches have been reported to fabricate TiO2 nanostructures, including template assisted hydrothermal, anodization, and sol-gel. Among them, anodization method is capable of producing highly ordered, well aligned TiO2 nanotubes (NTs) with controlled diameters and tube length. The unidirectional tubular structure provides the charge transport channels from electrolyte/photoanode interface to conductive substrate.

The intrinsic band gap of TiO2 (3.2eV for anatase and 3.0eV for rutile), however, limits its optical absorption only within UV region. The rapid recombination rate of photo-excited electrons and holes also severely hinders its practical application.1 Many approaches have been developed to promote the photo response of TiO2 in visible light region. For example, by hetero coupling, the holes and electrons can be photo excited from the narrow-gap semiconductor and separated effectively, which significantly promotes the visible light response. To form hetero coupling, cobalt oxide, a typical P-type semiconductor with band gap of ~2.1eV is chosen. Recent report shows cobalt oxide coupled with TiO2 exhibit could enhance the photo oxidation activity under visible light illumination.2 CoOx/TiO2 nanoparticles also show great photocatalytic activity on water splitting.

Here we report the formation of CoOx/TiO2 NTs hetero coupling by atomic layer deposition (ALD). ALD is ultrathin film deposition technique to have sub-nanometer control of film thickness. As a promising method to passivate and modify photoanode,3 ALD could form chemical bonds on substrate and operate at a relatively low temperature. We will show that by uniformly depositing a layer of cobalt oxide film onto the TiO2 nanotubes, CoOx/TiO2 NTs system exhibits one fold improvement on photocurrent response under visible light illumination compared with pristine TiO2 NTs, and about two times the efficiency of CoOx/TiO2 synthesized via wet-chemistry method. The structure was detailed studied and optimized, and mechanism will also be discussed.

References:

1. S. Kurian, H. Seo and H. Jeon, The Journal of Physical Chemistry C, 2013, 117, 16811-16819.

2. T. Q. Ngo, A. Posadas, H. Seo, S. Hoang, M. D. McDaniel, D. Utess, D. H. Triyoso, C. B. Mullins, A. A. Demkov and J. G. Ekerdt, Journal of Applied Physics, 2013, 114, 084901-084908.

3. S. C. Riha, B. M. Klahr, E. C. Tyo, S. Seifert, S. Vajda, M. J. Pellin, T. W. Hamann and A. B. F. Martinson, Acs Nano, 2013, 7, 2396-2405.
R&D Overview of 3D Integration Technology Using TSV in Japan
Authors: Kada Morihiro
Published: February 2020

The electronic industry which towed Japanese industry is making a desperate effort for the second prosperity. The past several years a decline of Japanese electronic industry, especially semiconductor industry is severe and must come back again.

3D Integration Technology using Thorough Si Via (TSV) is expected as the engine for strengthening of global competitiveness. This technology, as a core technology of More than Moore, that importance has been recognized and development has been performed all over the world. However, full-scale volume production is not started yet, since killer applications which can accept the higher cost are not found. But the adoption to High band memory such as HMC, HBM, Wide/IO SDR, NAND memory, FPGA products, Logic+ Memory, CIS and so on including 3D and 2.5D will be expected in the near future.

In this presentation, the history of R&D of 3D Integration Technology using TSV in the world and the latest R&D are overviewed. Then, R&D results of Japanese national R&D project "Development on Functionally Innovative 3D-Integrated Circuit (Dream Chip)” which had been conducted through FY2008 to FY2012 is introduced. These consisted of six following subjects which lead to volume production were developed.

-Thermal Management & Chip Stacking Technology

-Thin Wafer Technology

-Ultra-wide Bus SiP 3D Integration Technology

-Digital-Analog 3D Integration Technology Heterogeneous 3D Integration Technology

-3D-Integration Basic Technology

Moreover, is explained the outline of "Next Generation Smart Device Project" newly started by the schedule of from FY2013 to FY2017. These are development of the key device of the system for grasping the circumference information on a car and realizing safe driving support.

-In-vehicle obstacle sensing device

-Obstacle detection and a risk cognition application-processor
Electrodeposited Copper Wire for Transparent Conductive Film
Authors: Kondo Kazuo , Ikeda Yuichi , Yokoi Masayuki , Okamoto Naoki , Saito Takeyasu
Published: February 2020

Introduction

ITO(indium tin oxide) is the most common transparent conductive film used for touch panel and solar cell. However, the Indium is the rare metal and sputtering tool is expensive. Hence there are drastic demands for the ITO substitutes.

Silver nano-wire is a good candidate for the ITO substitute(1), however, cost is 60 times expensive than copper. Furthermore, the resistivity of copper is almost same as silver. Most conventional copper wire is produced by etching of photo lithographed copper foil(2), however, etching consumes most of the copper area, since we need high transparent film.

By using the chromium electrodeposited mold, the copper electrodeposits preferentially into the mold cracks and forms copper wire. Hence, the copper wires have been electrodeposited into the mold cracks and their characteristics as the transparent conductive film have been measured.

2.Experimantal

The electrodeposits substrate is SUS 304. The chromium mold has been electrodeposited onto this SUS 304 with Sargent bath at 600mA/cm2 for 72min. Then annealed at 150℃ for 5hours. The copper wire has been electrodeposited preferentially into the chromium mold crack. The bath consist of 25g/l of H2SO4, 200g/l of CuSO4・5H2O and the additive. The current density is 10 to 50mA/cm2with 5 to 150s at room temperature.

The openings of copper wire(=Transparency) has been measured on the chromium mold. The wire width, wire resistance and transmittance have been measured by removing the copper wire from the chromium mold. Chromium etching solution has been used to remove the copper wire.

3.Results

1.Figue 1 shows the top view of copper wire and chromium mold. Numerous numbers of copper wires are running along the chromium mold cracks.

2.For the copper wire of 30second electrodeposition time, the wire resistance is 0.18Ω/□ , wire width is 9.8μm and the transmittance is 84%. These wire resistance, width and transmittance satisfy the requirements for the transparent conductive film.

3.Figure 2 shows the photo of display with the copper wire has been placed on the LCD. Our copper wire have enough transmittance

References

http://www.cambrios.com/technology

http://panasonic.co.jp/news/topics/2013/112371.html

Nikkei Electronics,7-22,P14(2013)
Cu Displacement Plating on Electroless Plated CoWB Layer on SiO2 and Its Adhesion Property
Authors: Ohta Kohei , Inoue Fumihiro , Shimizu Tomohiro , Shingubara Shoso
Published: February 2020

Fabrication of TSV is one of key technology for 3D-ICs. For realizing conformal barrier layers against Cu diffusion with a low temperature process is important to achieve highly reliable TSVs. Electroless plated metals such as CoW-alloy and NiW-alloy are widely studied as a capping layer on Cu, and they are also considered to have a high potential as a barrier layer.

We succeeded in conformal electroless plating of CoWB on SiO2, using DMAB as a reducing agent after forming self-assembled monolayer (SAM) of silane coupling agent on SiO2 [1-3], assisted with Pd nanoparticle catalyst. Electroless Cu plating on CoWB using reducing agent showed insufficient adhesion strength. The adhesion strength of CoWB decreased with an increase in film thickness [1], which might be due to an increase of film stress with increasing film stress. In this study, we tried to form electroless Cu seed layer by displacement plating without reducing agent, and investigated improvement of adhesion property.

The Cu plating bath composed of sulfuric acid and copper sulfate , and its pH were varied between 1.5 to 3.5. Fig.1 shows cross-sectional SEM view after the Cu displacement plating in the case of pH 2.5 on CoWB film. Initially CoWB thickness was 70 nm (Fig.1-a), and 60 nm Cu layer was formed on the CoWB, while the thickness was decreased to 25 nm due to replacement reaction. Oxidation of Co atoms and reduction of Cu ions occurred concomitantly by displacement plating.

The adhesion strength were evaluated by a stud-pull test. Table 1 shows the adhesion strengths of various films such as CoWB (70nm), displacement plated Cu/CoWB, electroless Cu plated with reducing agent on CoWB. The adhesion strength of the 70 nm CoWB film was 20MPa. That of displacement plated Cu/CoWB was 50 MPa. The adhesion strength of electroless plated Cu reducing agent was very poor. We were able to get enough adhesion strength with displacement plating.

We are going to examine Cu displacement plating of various pH conditions. Furthermore, application of this process to TSV structure is in progress.

References

[1] F. Inoue, T. Shimizu, H. Miyake, R. Arima,T. Ito, H.Seki,Y. Shinozaki, T. Yamamoto, and S.Shingubara, Microelectronic Engineering, 106(2013) 164–167.

[2] F.Inoue, T.Shimizu, T. Yokoyama, H. Miyake, K. Kondo, T. Saito, T. Hayashi, S. Tanaka, T. Terui and S. Shingubara, Electrochimica Acta, 56-17 ,6245-6250, (2011).

[3]W. J. Dressick, C. D. Dukey, J. H. Georger. Jr, G. S. Carabrese, and J. M. Calvert, J Electrochem. Soc., 141 (1) 210 (1994)
Contact Behavior among Vertical Aligned Carbon Nanotube Bumps under Compression for Flexible Multilayer Substrates
Authors: Fujino Masahisa , Terasaka Hidenori , Suga Tadatomo
Published: February 2020

Carbon nanotubes (CNTs) are expected to be a substitutional wiring material instead of copper, because of the properties of high maximum allowable current density, and the low resistivity. Especially, bundled vertically aligned CNTs (VA-CNTs) have the flexible structure and it is considered that VA-CNTs are suitable for vertical interconnect among flexible substrates.In this research, we fabricated VA-CNTs as bump shaped structures and located on flexible substrates for flexible multilayer substrates and their electrical property was investigated.At first, VA-CNT bumps were synthesized on SOI substrate by the thermal chemical vapor deposition method using Fe as catalyst and acetylene gas as source gas. Secondly, Au was sputtered on the substrate of VA-CNT bumps by magnetron sputter. In this process, surface shells of top of VA-CNT were torn by plasma energy and sputtered Au particle was directly contacted to the edges of torn layer of VA-CNTs and inner layers of CNTs for low contact resistance. Subsequently, the substrate of VA-CNT bumps was bonded to Au electrodes on polyimide substrate by surface activated bonding method, that surfaces of specimens were cleaned and activated by Ar ion beam or Ar plasma in vacuum, then they were bonded each other.After bonding, the SOI substrate was removed from VA-CNTs and polyimide substrate, then sputtering process and surface activated bonding to polyimide substrate process were performed again to opposite side. The bonded substrates have a flexible structure and its flexibility against the electrical property was evaluated.As a result, the bonded structure was confirmed to be tolerant of bending 2 to 3 mm curvature. Furthermore, the resistivity of VA-CNT bumps was decreased from 106 to 7.8 Ω under more than 0.75 MPa compression.Thereafter, the VA-CNT bump were required to be bonded more than 0.75 MPa for good conductivity, and the conductivity was stable under the compression more than 0.75 MPa.It indicates that the flexibility of VA-CNT/polyimide substrates were effective on condition of preload to VA-CNT bumps.
Enhancement of Bonding Strength for Low Temperature Si3N4/Si3N4 Direct Wafer Bonding by Nitrogen-Plasma Activation and Hydrofluoric Pre-dip
Authors: Lo F. -S. , Chiang C. -C. , Li C. , Lee T. -H.
Published: February 2020

Applying the hydrofluoric (HF) pre-dip treatment on the surfaces of one pair of bare silicon wafers before performing plasma-activation wafer bonding approach, the annealing temperature for achieving silicon fracture bonding strength can be drastically reduced as low as 75°C. In comparison, the annealing temperature is 700°C or higher in the case of a conventional HF-dip hydrophobic wafer bonding or 300-400°C through the assistance of hydrogen trapping defective surface layer caused by boron ion implantation.

Applying the same bonding approach to the Si3N4/Si3N4 wafer bonding, we found the bonding strength reaches the level of silicon fracture through a 200°C annealing less than 24 hours compared with 400 hours done by HF-dip only. The bonding mechanism is proposed as following: the HF-dip treatment passivated the Si dangling bonds on the Si surface or the broken Si-N network of the Si3N4 surface to form sufficient high density of Si-H bonds. And then the application of N2 plasma treatment increases the density of Si-H-N bonds for forming hydrogen bonds which bridges the two bonding surfaces resulting in high bonding strength after annealing.
Formic Acid Treatment with Pt Catalyst for Cu Direct Bonding at Low Temperature
Authors: Suga Tadatomo
Published: February 2020

The paper describes a new process of Cu-Cu direct bonding at a temperature lower than 200ºC in atmospheric pressure. The method consists of reduction process of Cu oxide using formic acid treatment and subsequent generation of Cu nano-particles by means of Pt catalyst. The main idea of the proposed method is that due to Pt catalytic effect, combined to the conventional formic acid treatment, a part of the formic acid is decomposed to generate hydrogen radicals to reduce the oxide of the Cu surface, CuO and produce Cu formats very effectively. As the result, nano-particles of Cu are precipitated from the formats on the Cu surface and a tight bonded interface can be formed at a temperature below a 200ºC. Cu surface was heated in water vapor to enhance the oxidation process and compared regarding to the precipitation of the Cu nano-particles.

The mechanism of precipitation of Cu nano-particles and Cu direct bonding at low temperature using formic acid treatment was investigated. It was assumed that the top of the oxide layer of Cu surface, probably CuO, is reduced effectively by H radicals which are generated from formic acid by means of Pt catalyst. The surface layer of Cu after the reduction, probably Cu2O, is reduced subsequently by formic acid, leading to precipitation of Cu nano-particles according the conditions of the heat treatment and the formic acid treatment. It was shown also that the precipitation of Cu nano-particles may contribute the direct bonding of Cu surfaces at low temperature.
Fermi-Level Depinning of Ge Schottky Junction Using Se Treatment
Authors: Lim Yi-Rang , Lee Ye-Ji , Shim Ku-Hwan , Janardhanam V. , Choi Chel-Jong
Published: February 2020

Depinning of the Fermi-level at metal/Ge Schottky junctions was achieved by Se treatment at room temperature. Due to the strong Fermi-level pinning close to the valence band edge in Ge, Schottky and Ohmic behaviors were observed in conventional Al Schottky contacts to n- and p-type Ge, respectively. However, Al Schottky contacts to n- and p-type Ge with Se treatment became Ohmic and Schottky, respectively. Electron and hole barrier heights calculated using Richardson plots were found to be 0.15 eV for of Al contacts to Se-treated n- type Ge, and 0.33 eV for Al contacts to Se-treated p-type Ge, respectively. The transmission electron microscopy (TEM) examination combined with X-ray photoemission spectroscopy (XPS) analysis showed that Se treatment at room temperature yielded the formation of a fairly uniform Se-Ge alloy film with partially ionic binding nature caused by the chemical reaction between Se and Ge. This led to the reduction of surface states of Ge surface along with the passivation of dangling bonds by the incorporation of Se atoms, which was responsible for Fermi-level depinning at Al/Ge junctions.