bluuebunny/crossref_metadata_2025_split huggingface dataset:
(Invited) Rare Earth Doped Metal-Oxide-Semiconductor Structures: A Promising Material System or a Dead End of Optoelectronic Evolution?
Authors: Rebohle Lars , Berencén Yonder , Braun M. , Garrido Blas , Hiller Daniel , Liu B. , Ramírez Joan Manel , Sun Jiaming , Wutzler Rene , Helm Manfred , Skorupa Wolfgang 
Published: February 2020

Integrated photonics is a key technology of the 21st century, and the electrically driven, integrated light emitter is an important building block, but difficult to realize. Thus, an enormous variety of different materials and material systems have been investigated in the past, ranging from the various approaches to integrate III-V semiconductors to the different types of Si-based light emission. Within the latter group rare earth (RE) implanted MOS structures feature a high conformity with standard CMOS processes combined with the excellent optical properties of RE elements.
After more than 20 years of intense research in the field of Si-based light emission the results are mixed. With respect to important key parameters, most of all power efficiency, Si-based light emitters are not yet able to compete with their counterparts based on compound or organic semiconductors. The present contribution discusses the problems of Si-based light emitters at the example of RE-doped MOS structures, and compares various light emitter designs and their potential to overcome these problems.
In detail, the power efficiency, the operation lifetime and the operation voltage of Tb- and Er-doped MOS structures are investigated. The main electroluminescence excitation mechanism is impact excitation of hot electron which plays an ambivalent role: efficient excitation is often related with efficient defect creation. In addition, a dark zone close to the injecting interface limits the scalability towards low voltages. The excitation mechanism und thus the performance of the light emitter is affected by the structure and composition of the dielectric stack of the MOS structure. Within this study, several host materials for the RE ions, namely stoichiometric and Si-rich silicon oxide or silicon nitride; different fabrication methods, namely plasma enhanced chemical vapour deposition, ion implantation and atomic layer deposition; and the use of additional buffer or injection layers are investigated. Finally, a short perspective to potential applications is given.
Influence of Bound Metals on the Electrical Properties of Single Molecule Junction Porphyrin-Imides Linked to SWNTs
Authors: Handayani Murni , Gohda Shun , Tanaka Hirofumi , Tanaka Daisuke , Ogawa Takuji 
Published: February 2020

Since Aviram and Ratner proposed that a single molecule could act as a molecular rectifier, containing a donor and an acceptor separated by a sigma bond, many such molecules have been synthesized for use in devices. Among these, porphyrins are widely used as molecular electronic devices owing to their structural flexibility as well as their well-developed synthetic chemistry, which allows their physical and chemical properties to be adjusted, making them ideally suited for binding to metals. In this research, porphyrin-imide dyads with perpendicular arrangements containing different metals (zinc and rhodium) bound to porphyrin molecules have been synthesized (Figure 1) and the effect of these “center metals” on the electrical properties of single molecule junction porphyrin-imides connected to SWNTs have been investigated.
DFT calculations for porphyrin-imide dyads revealed that the HOMO and LUMO energy levels of the dyads were completely separated, indicating the absence of any intramolecular interactions between the donor and acceptor. Furthermore, these calculations also revealed that the molecular orbital of rhodium porphyrin-imide for HOMO-2, HOMO-3, and LUMO-1 were entirely localized on the rhodium center, whereas no localization on the zinc center of the molecular orbital for zinc porphyrin-imide was observed. Based on these DFT results, it was predicted that employing zinc and rhodium as center metals would result in the corresponding dyads having different electrical properties.
The connection of single molecule junctions for porphyrin-imides linked covalently to SWNTs was evidenced by the coordination of the rhodium porphyrin-imide dyad with pyridine-tert-dodec-AuNPs (~3 nm in size) used as a marker. AFM topography was employed in order to confirm that the AuNPs were attached to the molecule. Moreover, the topography revealed the presence of particles with a height of 2.6 nm, which subsequent TEM observations revealed to be part of a single-molecule junction (Figure 2c). The electrical properties of these dyads were measured by point-contact current imaging atomic force microscopy (PCI-AFM). The results for the rectification behavior of single molecule junction zinc porphyrin-imide revealed larger values, with an average rectification ratio of 26, compared to the rhodium porphyrin-imide that had an average rectification ratio of 6. This differential conductance indicated that the HOMO-LUMO gap can be controlled by changing the center metal.
References:

L. Hong, H. Tanaka, T. Ogawa, J. Mater. Chem. C, 1137 (2013)

H. Tanaka, L. Hong, M. Fukumori, R. Negishi, Y. Kobayashi, D. Tanaka, and T. Ogawa
Nanotechnology, 23, 215701 (2012).

H. Ozawa, M. Kawao, H. Tanaka, Langmuir 2007, 23, 6365-6371
In Situ Surface Enhanced Raman Spectroscopic Studies on Manganese Oxide
Authors: Pavlovic Zoran Miroslav , Ranjan Chinmoy 
Published: February 2020

Non noble metal "earth abundant" electrocatalysts will significantly reduce the costs and make it possible to use electrochemical water splitting on a very large scale. Non noble metal catalysts can be an effective replacement even if their electrochemical activities are a fraction of their noble metal counterparts. If these catalysts can be developed to an extent where their operational lifetime would become comparable to their noble metal counterparts, a large part of the problem would be solved.
Whether in acidic, alkaline or neutral media, catalyst corrosion remains a significant challenge to oxygen evolution. MnO2 is earth abundant and well known for catalyzing oxygen evolution. A form of MnOxcluster is known to catalyze water oxidation in photosynthesis. The problem is that the catalyst comes with a significant corrosion problem.
MnO2 + 2H2O --> MnO4
- + 4H+ + 3e- E0= 1.69V vs. NHE
Besides that MnO2-xnaturally exists in various polymorphs, with various amounts of defects each of which is known to have a different electrocatalytic performance. Poor ballistic electronic conduction (important for good electrode materials) is also a prevalent issue with these oxides. These catalysts although with immense potential remain a long way from successful implementation within electrolysers. In order to understand the limitations of this catalyst under the operational conditions, it is important to study this material in situ.
Setup for in situ Surface Enhanced Raman Spectroscopy is used for tracking the structural changes of hydrous MnOx while changing the potential in the range of 0 - 2,0 V. Electrodeposition of MnOx on the surface of Au was achieved by passing an anodic current of 50 mC/cm2 at 1,6V. The resulting MnO2 phase could be termed as the alpha/MnO2 phase. The structural integrity of the MnOx was studied by following the Mn-O-Mn stretching various potential ranges in various electrolytes. Onset of phase changes and corrosion could be clearly established.
Trends in Adsorption Characteristics of Organic Molecules on Transition Metal Surfaces: Role of Surface Chemistry and Van Der Waals Interactions
Authors: Yildirim Handan , Kara Abdelkader 
Published: February 2020

The accurate description of interface characteristics between organic molecules and metal surfaces has long been debated in theoretical studies. A well-founded description of interface geometry and adsorption energy is highly desirable for these systems. Using first principles calculations with the inclusion of van der Waals interactions, we examine adsorption characteristics of few organic molecules on several transition metal surfaces. Our aim is to obtain insights into the role of vdW interactions in the adsorption characteristics as well as to build understanding how these functional treat the adsorption in varying surface chemistries. Furthermore, the comparisons made between the results obtained using different vdW functionals for each organic molecule type provide the means to assess their performance.
This work is funded by the U.S. Department of Energy Basic Energy Science under Contract No DE-FG02-11ER16243
The Effect of Different Gel Electrolytes on Graphene Based Solid-State Supercapacitors （oral)
Authors: Chen Qiao 
Published: February 2020

Graphene is a good candidate for the electrode materials for supercapacitors, as it’s excellent electrical, mechanical and optical properties. A all solid-state supercapacitors based on graphene was designed to study the effect of different electrically conductive substance (H3PO4, H2SO4, KOH, NaOH, KCl, NaCl) in polymer polyethylene terephthalate (PVA) gel electrolytes on the electrochemical performance of this supercapacitor,
Large multilayer graphene films were grown on copper foils by chemical vapor deposition (CVD) method. The few-layer graphene film grown by chemical vapor deposition was cut into squares with sides of 7~10 centimeters and was transferred onto the PET substrate directly. This supercapacitor is easily assembled through binding the two graphene electrodes together by gel electrolyte. Thus the device simply contains two film electrodes separated by solid electrolyte (gel electrolyte solidifies by water loss) and two flexible substrates, so it is ultrathin and high flexible.
The experiment demonstrated the specific capacitance of this graphene based solid-state supercapacitors varies with different electrically conductive substance in gel electrolytes with tremendous dissimilar cyclic voltammetry curves. The supercapacitors used PVA-H2SO4 electrolyte show higher device specific capacitance of 0.82mF/cm2 at a scanning rate of 100mV/s than other electrolyte. By optimization the concentration of H3PO4 from 0.01mol to 0.09mol in equal amount of PVA gel, the device specific capacitance of this supercapacitors was elevated from 0.07mF/cm2 to 2.64mF/cm2. At the same time the internal resistance decreased with the adding of H3PO4. The graphene-based supercapacitors provided imponderable changes of electrochemical properties during bend to 180-degree. This supercapacitors also possess great stability after 5000 circulations with more than 92% specific capacitance retained.
The Influence of the High Temperature Oxidation Regime on Residual Stresses in Oxide Scales on Fecral-Type Alloys
Authors: Jedlinski Jerzy , Grosseau Poussard Jean Luc , Dubiel Marcin , Zurek Zbigniew , Dąbek Jarosław 
Published: February 2020

The alumina-forming FeCrAl-type commercial alloys manufactured in different ways, conventional melting (Kanthal AF), mechanical alloying (MA956) and powder metallurgy (Kanthal APM), were oxidized at 1100⁰C, in air for 5 hours under isothermal and thermal cycling conditions. Subsequently, after final cooling down the samples to the room temperature, the residual stresses in oxide scales as well at their phase composition and morphology were determined using Photoluminescence Spectroscopy and/or Scanning Electron Microscopy.
Different residual stresses were found in scales growing on various materials, under different regimes. Moreover, they depended on the region of the scale. These differences are discussed in terms of the response of the scale-substrate system to growth, structural and thermal stresses.
An Investigation of the Discharge Rate Capabilities of Electrodes for Printed Nickel Based Batteries
Authors: Mabbett Ian , Glover Carol , Marinaccio Jordan , Worsley David A , Williams Geraint 
Published: February 2020

Printed micro-batteries could be used in a variety of small electric circuits such as RFID and sensors. Printing techniques can facilitate high volume manufacture in economical processes that have much to offer in energy storage applications. Utility scale electrochemical energy storage will also become an important topic as countries across the globe set targets for highly distributed electricity generation from renewable sources. Time shifting via appropriate energy storage installations as well as peak shaving to stabilise national grids will become an important part of future electricity infrastructures where electrification of transport and heating become commonplace. To meet the demands of such a market stationary, utility scale energy storage technologies must be safe, offer long lifetimes and have inherently low cost. This can be achieved by the use of earth abundant materials and by employing rapid, roll-to-roll, solution coating or printing processes.
Micro-batteries and utility scale energy storage solutions all have different demands in terms of capacity and rate capabilities. Design of electrodes to optimise energy storage can hinder the ability to deliver power and achieve high current densities.
This study describes how print parameters and sinter conditions can be varied to find compromises between kWh capacity stored and kW power that can be delivered on demand. Typical strategies to reduce activation polarisation and increase conductivity of electrode pastes usually result in less available active material to support charge transfer, thus lowering the useful capacity of the cell. This work describes how optimising printing processes to deliver a balance of active material availability and high rate capability can produce versatile electrodes. Sinter conditions are also investigated to strike a balance between the adhesion of the sintered electrode material to the substrate and controlled highly porous sintered structures required to promote adequate mass transport through the porous network of the electrode.
Physical characteristics of the printed electrodes are confirmed by SEM micrographs, profilometery and BET surface area and porosity measurements with the rate capabilities and capacities assessed galvanostatically. EIS and novel scanning electrochemical techniques shed further light on the impact of print and sinter parameters in electrochemical performance.
A Carbon-Free, Precious-Metal-Free, High-Performance O2 Electrode for Regenerative Fuel Cells and Metal-Air Batteries
Authors: Ng Desmond , Tang Maureen Han-Mei , Gorlin Yelena , Hatsukade Toru , Jaramillo Thomas Francisco 
Published: February 2020

There have been extensive research efforts focusing on developing technologies for renewable electricity, particularly solar photovoltaics and wind turbines. However, the intermittent and localized nature of wind and solar energy necessitates the development of a cost-effective way to balance energy supply and demand and to deliver electricity from remote places to cities.[1] The short-term option is the electricity grid; however, it can only support intermittent renewable electricity in a stable fashion up to approximately 20 % of grid capacity which means that fossil resources would still account for the remaining 80 % of grid electricity.[2] Clearly, the development of cost-effective energy storage devices is needed to establish a path toward fossil-free energy.
The development of high-performance and cost-effective electrodes for oxygen evolution and oxygen reduction is critical for enabling the use of energy storage devices based on O2-H2O chemistries such as metal-air batteries and unitized regenerative fuel cells (URFCs).[3] Herein, we report a precious-metal-free and carbon-free O2 electrode synthesized via electrodeposition of manganese oxide (MnOx) on a stainless steel (SS) substrate followed by high-temperature calcination at 480 oC. The MnOx-SS electrode displays high oxygen reduction and water oxidation activities when tested in an electrochemical cell, comparable to that of a precious-metal based electrode, Pt/C-SS. Accelerated durability testing reveals the excellent stability of the MnOx-SS electrode compared to both the Pt/C-SS electrode and a carbon-based electrode with MnOx and Ni catalysts. This can be rationalized by the carbon-free nature of the MnOx-SS electrode which circumvents carbon corrosion at the high electrochemical potentials during water oxidation and O2 reduction. Integrating the MnOx-SS electrode as the O2 electrode in an anion exchange membrane (AEM) URFC produces round trip efficiencies of 42-45 % at 20 mA.cm-2 over 10 cycles, and exhibits significantly enhanced durability compared to the carbon-based analogue. This work demonstrates the MnOx-SS electrode’s potential for use as a high performance, scalable, precious-metal-free and carbon-free O2 electrode in AEM-URFCs and metal-air batteries.

References

[1] Z. Zhan, W. Kobsiriphat, J.R. Wilson, M. Pillai, I. Kim, S.A. Barnett, Energ. Fuel.
2009, 23, 3089.
[2] W. Kempton, J. Tomić, J. Power Sources
2005, 144, 280.
[3] J.W.D. Ng, Y. Gorlin, T. Hatsukade, T.F. Jaramillo, Adv. Energy Mater.
2013, 3, 1545.
Integration of PVDF (Polyvinylidene Fluoride) in MEMS Production
Authors: Holz Stephanie , Kiricenko Sergej , Rissing Lutz 
Published: February 2020

Introduction

The combination of materials with new processing setups often leads to new opportunities in well-known technologies. Polyvinylidene fluoride (PVDF) is widely used because of its chemical resistance and thermal properties. Usually, it is shaped by spray casting to produce plumber components. PVDF is also known for its piezoelectric behavior, which can be measured in PVDF films, like it was shown by Kawai [1] and others long ago. Nevertheless, piezoelectric materials are used in MEMS production, PVDF is not. Therefore, the main idea is to evaluate the possibilities and afterwards creating a way for the integration of PVDF in MEMS production for example as membrane for flexible parts with piezoelectric behavior.

Solubility and Spin coating

As a substrate with a high chemical resistance, PVDF is only soluble in a few solvents. However, to use PVDF films does not seem promising, because of the inclosed gas bubbles, the difficulties to produce thin films and the need to reach a bond between film and wafer.
Spin coating was chosen to get PVDF films on wafer substrates. To obtain a photoresist like solution of PVDF, three different solvents (DMF, DMAc, NMP) were tested. Each showed good solution result, even though it took up to several days to get a homogeneous solution.
Spin coating was performed with each solution. Afterwards the reached thickness of the PVDF layer was measured. A connection between amounts of PVDF in solution and thickness could be found as well as between the different solvents used for the solutions.

Measurement and cumulation of the piezoelectric behavior

For the following experiments, several wafers were prepared with PVDF by spin coating. Some were dried under standard conditions (95°C, 5 min). The others were dried in an electric field, to reach an increasing in the piezoelectric behaviour. These PVDF film were compared to PVDF films that were exposed to an electric field in solid state. The setup for that is shown in picture A.
The setup for the exposure of the liquid PVDF is far more complex because a defined air gap is needed during the baking process. Therefore, the setup was changed. The wafer is placed on the heating plate, which is used as on electrode. The other electrode is located parallel to the wafer with a small air gap of at least 4 mm.
A relation between electric field and piezoelectric behavior could be shown. Therefore the method seems promising. Picture B shows the results of the first spin coating tests with PVDF as membrane material for flexible parts.
[1] H. Kawai, “Piezoelectric Effect in Polarized Poly (vinylidene Fluoride)”, Japan. J. Appl. Phys., 8, 975, 1969
Ångstrom Resolved Real-Time Monitoring of Oxide Growth and Reduction on Noble and Engineering Metals
Authors: Valtiner Markus , Cheng Hsiu-Wei , Shrestha Buddha Ratna , Baimpos Theodoros , Raman Sangeetha 
Published: February 2020

Structure and dynamics at electrochemical metal/liquid interfaces determine lifetime and stability of advanced and structural materials, and are fundamental to corrosive processes. Here, we present recent experiments with the newly developed and unique electrochemical surface force apparatus1,2, which allow us to unravel electrochemical oxidation and reduction processes in real-time at well-defined and nano-confined electrodes. In particular, we monitor metal-oxide thin film formation with Å-accuracy during potentiostatic and potentiodynamic polarizations. In confined spaces we find unexpectedly strong electrochemical depletion forces acting between apposing surfaces during active electrochemical processes. Depending on the conditions, these forces are repulsive and can strongly overpower attractive Van der Waals forces, and the associated electric-field gradients might have significant effects in corrosive processes occurring in nano-confined spaces (such as crevices or pits). In addition, using the EC-SFA we have, for the first time, monitored oxide growth and reduction on noble metals (Au, Pt, Pd and Ir) in sulfuric acid solutions, as well as Nickel and Aluminum corrosion in confinement situations, with Ångstrom resolution in thickness and in real time with milliseconds resolution. Our experiments reveal stark differences of oxide thickness and its electronic properties during potentio-dynamic and potentio-static oxide growth, which will be discussed in the presentation.
1. Valtiner, M. et al. The Electrochemical Surface Forces Apparatus: The Effect of Surface Roughness, Electrostatic Surface Potentials, and Anodic Oxide Growth on Interaction Forces, and Friction between Dissimilar Surfaces in Aqueous Solutions. Langmuir
2012,
28(36), 13080-13093.
2. Israelachvili, J. N. et al The Intersection of Interfacial Forces and Electrochemical Reactions. J. Phys. Chem B, 2013, 117 (51), 16369–16387.
Study of the Hydrodynamic Conditions of the 2-Mercaptoimidazole Inhibitor Derivatives for Mild STEEL Immersed in NaCl at Neutral pH
Authors: Espinoza Araceli , Palomar Manuel , Romero Mario Alberto , Buendia Erika 
Published: February 2020

Introduction

Recently, our research group has demonstrated that some organic molecules such as 2-MBI derivatives can be also considered as an effective corrosion inhibitors for carbon steels in acidic media.

Results

Fig. 1 shows the variation of the corrosion inhibition efficiency, which indicates that at low concentrations the best inhibitor was the 2-mercaptoimidazole (2MI) giving 90% IE at 10 ppm, thus being the least efficient the 5-nitro-2-mercaptobenzimidazole (5N-2MBI) with an efficiency of 80% inhibition at 200 ppm.
Moreover, this compound follows an adsorption mechanism, which can be adequately described by the Langmuir isotherm thereby pointing to a physisorption process on the metal surface.