bluuebunny/crossref_metadata_2025_split huggingface dataset:
Resistance Switching Phenomenon Associated with Anisotropic Magnetoresistance of the ReRAM Device with Ferromagnetic Electrodes
Authors: Ito Daisuke , Yoshida Hayato , Shimizu Tomohiro , Shingubara Shoso 
Published: February 2020

A resistive random access memory (ReRAM) is expected to be a next-generation nonvolatile memory substituting NAND Flash because of good scalability against downsizing, fast switching speed and low power consumption. ReRAM operation relies on the ability of the metal oxide to reversely change its resistance from high resistance to low resistance and vice versa by SET or RESET operation. The device structure is composed of a metal oxide layer sandwiched between two metal electrodes. In general, it is considered that resistive switching is caused by the formation and rupture of conductive filament (CF) such as metallic filaments or an oxygen vacancy filaments formed in the oxide layer. It is widely accepted that the type of filaments formed in the ReRAM devices depends on the combination of materials used as the electrodes and the oxide layer. The metallic filament is considered to be formed by metal ions migrated from the oxidizable electrode when a positive bias is applied to the oxidizable electrode. In the previous study, we found that ferromagnetic filament was formed at the on-state of the Ni/TiO2/Pt device [1]. Actually we observed a weak anisotropic magnetoresistance (MR) at room temperature. This study suggested that the conductive filament was formed with migration of Ni atoms from Ni electrode.
In this study, we fabricated ReRAM device having two ferromagnetic electrodes; Ni and Fe-Ni. Both electrodes may be active under the voltage stress. Figure 1 shows the MR characteristics measured for the Ni/HfOx/Fe-Ni device at the room temperature. MR ratio is defined as α = [R(H)-R(H0)/R(H0)]×100. The ferromagnetism of filament was confirmed because the resistance of filament changed against magnetic field. It is most likely that this behavior is categorized as anistropic magnetoresistance. From the results, it is suggested that the conductive filament of Ni/HfOx/Fe-Ni device is formed by ferromagnetic materials. Further discussions and analysis will be presented in the symposium.
References
[1] S. Otsuka, Y. Hamada, T.Shimizu, and S. Shingubara, Appl. Phys. A, 118 (2015) 613.

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Cathode Design for a Molten Salt Lithium-Oxygen Battery
Authors: Tozier Dylan , Giordani Vincent , Gallant Betar Maurkah , Burke Colin , McCloskey Bryan D , Greer Julia R , Chase Gregory V , Addison Dan 
Published: February 2020

The rechargeable lithium-oxygen battery has attracted attention due to its large theoretical energy density compared to modern lithium-ion batteries. This large energy density is attributed to the reaction of lithium with molecular oxygen to form lithium peroxide, which grows on the surface of the cathode. While this is a promising chemistry, there are many practical challenges that remain to be solved, such as the decomposition of organic electrolyte in the presence of superoxide anions and large overpotentials on charge. Additionally, the mechanism of lithium peroxide growth and its resulting morphologies is not fully understood.
Here we propose a system which inherently avoids many of the issues associated with organic electrolyte decomposition, while also forming lithium peroxide with a unique morphology. By using a molten salt (Li/K nitrate) in place of a conventional solvent/salt electrolyte, solvent decomposition is obviated. In addition, the elevated temperature of the molten salt as well as the large concentration of lithium ions encourage faster diffusion and kinetics.
In literature, the three commonly observed morphologies of electrochemically grown lithium peroxide are thin films, platelets, and “toroids” which are small stacks of platelets. While we do observe the platelet style growth of lithium peroxide, we also see much larger structures which appear to be stacks of hexagonal layers (see attached figure). We believe these stacks to be a new morphology of lithium peroxide growth. To substantiate this claim, we note that the Wulff construction for lithium peroxide is a short hexagonal prism, while also confirming the reaction product using XRD. This new morphology could be attributed to the fact that our cell operates with elevated temperature and large concentration of lithium and superoxide ions, making it easier to achieve an equilibrium (Wulff) structure.
We have shown a lithium-oxygen battery chemistry that produces a new morphology of lithium peroxide, and begun to develop a mechanism for why it forms. In addition, we have explored the effect of various cell parameters such as discharge rate on the morphology of the resulting lithium peroxide.

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High Capacity Magnesium Metal Rechargeable Battery Enabled By Dual Ion Chemistry
Authors: Gao Tao , Noked Malachi , Suo Liumin , Han Fudong , Zhu Yujie , Luo Chao , Xu Kang , Wang Chunsheng 
Published: February 2020

Electrochemical energy storage is the core technology for the success of green transportation and renewable energy. Among existing energy storage chemistries, magnesium metal rechargeable batteries (MRB) are receiving growing attention due to the abundance of magnesium and its highly reversible and dendrite-free deposition/dissolution in Grignard–based complex electrolyte, which enables the exploit of the high capacity magnesium anode(2233 mAh/g).These merits have made MRB a promising candidate system to store electrochemical energy. However, the strong coulombic interaction between an intercalation host and the bivalent Mg2+ makes the solid state diffusion of the latter rather sluggish, resulting in low Mg2+intercalation level, large polarization during charge/discharge and/or rapid capacity decay for common cathode materials.
To solve the problem, we developed a high capacity MRB by coupling TiS2 with magnesium foil in a dual-ion chemistry(Mg2+/Li+). The battery operates by Li+ insertion/extraction at cathode and Mg deposition/dissolution at anode. The battery simultaneously combines high-capacity/high-voltage, fast Li+ intercalation of TiS2 and the high-capacity/dendrite-free deposition of Mg anode.
Compared to other MRBs, the theoretical specific capacity and specific energy of the dual-ion battery is 161.0 mAh/g and 209.3 Wh/kg even when the weight of lithium salt was taken into account, which are 32.2% and 56.2% higher than 121.8 mAh/g and 134 Wh/kg of the state-of-the-art MRB(with Mo6X8 cathode). Noteworthily, there is still a huge potential to be exploited for this dual-ion battery concept. If a high voltage/capacity cathode compatible to electrolyte can be found, the specific energy could be increased largely. This could make it an alternative even competitive to the mainstream LIB technology, not mentioning the advantages of a dendrite-free Mg anode that is free of inert masses (current collector, binder, and conductive additives) and first cycle irreversible reaction associated with SEI formation.

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Characterization of InN - In0.25Ga0.75N Quantum Well Laser Structure for 1330 nm Wavelength
Authors: Polash Md. Mobarak Hossain , Alam M. Shah 
Published: February 2020

In this work, a nitride based wurtzite-strained single quantum well laser has been designed and characterized at 1330 nm wavelength. Here, 12Å InN layer has been used as well material and 15Å In0.25Ga0.75N layer has been used as barrier material along with GaN as separate confinement heterostructure for better carrier and optical confinement. To determine the electronic properties of the designed structure, a developed self-consistent method has been solved. Conduction subband calculation has been performed with the solution of Schrodinger equation formed by single band Hamiltonian followed by Poisson's equation. 6-bands k . p Hamiltonian for wurtzite semiconductor has been solved for valence band Schrodinger's equation with Poisson's equation considering band mixing effect, strain due to lattice mismatch and spontaneous and piezoelectric polarization. The interband momentum matrix elements, optical gain, spontaneous emission rate, spontaneous radiative recombination rate and radiative current density have been calculated to analyze the optical properties of the designed laser and a good agreement with previously published works is obtained. All analysis has been performed using injection carrier density of 6×10-19 cm-3 at T = 300 K. Due to the strain effect, the wave-function overlap integral has been obtained as 43.27%. From the electronic properties analysis, it has been found that, the designed structure is TE polarized with C1-HH1 and C1-LH1 dominating transitions. From the analysis of optical properties, the obtained spontaneous emission rate is 5945.2 s-1 at 1329.55 nm and spontaneous emission rate per energy interval per unit volume is 7.21×1027 s-1cm-3eV-1 at same wavelength. The obtained radiative recombination rate is 7.77×1029 s-1cm-3 and radiative current density is 149.19 Acm-2. The optical gain for TE polarization of the designed QW structure is 5261.52cm-1 at 1336.7 nm.

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(Invited) Triboelectric Nanogenerators for Self-Powering Small Electronics
Authors: Kim Sang-Woo 
Published: February 2020

Recently autonomous smart systems met a large success. Especially, the internet of things is a key driving force for the development of wireless, sustainable and independent smart systems. Therefore, their autonomy is critical and despite the progresses in low power electronics and battery, it is not enough and energy harvesters are becoming increasingly important. For this, harvesting mechanical energy is essential as it is widespread and abundant in our daily life environment. Among harvesters, flexible triboelectric nanogenerators (TENG) have good performances and are easy to integrate which make it the perfect candidate for many applications, and so crucial to develop. In this presentation, I first briefly introduce the fundamentals of TENGs, including the four basic operation modes. Then I discuss the different improvement parameters. I will also address some progresses made in terms of performances and integration which have been realized through the understanding of each operation mode and the development of innovative structures. Finally I present the last trends, structures and materials in view of better performances and applications.
Thin-Film Vapor-Liquid-Solid Growth of Compound Semiconductors on Heteroepitaxial and Amorphous Substrates
Authors: Kapadia Rehan 
Published: February 2020

We demonstrate the versatility of a previously developed low-cost thin-film vapor-liquid-solid (TF-VLS) compound semiconductor growth technique. Specifically, we show that the quality of compound semiconductors grown via this technique enables a variety of optoelectronic and energy devices with geometries and material combinations unavailable to traditional vapor-phase growth techniques. Critically, this is enabled by the confinement of a liquid metal solvent layer, enabling precise control over the position and shape of nuclei on non-epitaxial and hetero-epitaxial substrates simply by controlling the shape of the solvent. Unlike vapor-phase processes, in which control over the shape of a growing nuclei is extremely challenging and primarily defined by the growth rates of various crystal facets, the TF-VLS process enables full control over nuclei, enabling fabrication of single crystal and ultra-large grain polycrystalline compound semiconductors regardless of substrate microstructure. This control over the material is then utilized to demonstrate compound semiconductor devices for energy harvesting, photon generation, and photon detection.
Measurement of Optical Emission from Gesn Waveguides
Authors: Zhao Yun , Gallagher James , Li Zairui , Agha Imad , Menendez Jose , Kouvetakis John , Mathews Jay 
Published: February 2020

The development of Si-based lasers has been a goal of the photonics industry for many years. A number of methods have been explored for achieving lasers on Si platforms, and a few attempts, such as the Si Raman laser, have achieved marginal success, but typically suffer from low efficiency. The silicon photonics problem requires the realization of high-efficiency lasers on CMOS-compatible platforms.
One possible solution to this problem is to employ the use of direct band gap materials that can be grown on Si. Of course, the epitaxial growth of such materials has been extremely difficult, and the efforts have mostly concentrated on the use of III-V materials like InGaAs. These materials typically suffer from high defect densities when grown directly on silicon, making them unsuitable for use in lasers. Additionally, the introduction of Group III and Group V materials into a CMOS fabrication facility can cause severe problems in device production due the electronic properties of these atoms, which are typically used as dopants in Si.
GeSn alloys present a possible path forward for the realization of Si-based lasers, as these materials are grown directly on Si or Ge-buffered Si and have a band structure that is more suited for efficient optical emission. A laser based on tensile strained Ge grown directly on Si has been demonstrated at room temperature, but the efficiency is limited by the indirect nature of the Ge band gap. More recently, demonstration of lasing at low temperature in GeSn (12.6% Sn) was achieved using optical pumping of a GeSn waveguide. While this represents a first step to the actualization of GeSn lasers, room temperature operation is a necessary condition for widespread adoption and incorporation into everyday devices.
The approach for demonstration of lasing in GeSn and Ge-on-Si has typically relied on measuring the optical emission spectrum at very high resolution to see the narrowing of the emission linewidth and the presence of cavity modes while optically-pumping a waveguide with a pulsed laser via topside illumination. We have designed a new system for optically pumping waveguides by coupling into the waveguide edge, which increases the absorption length by orders of magnitude, thereby increasing optical emission intensity and relaxing the constraints under which lasing is achieved. We employ a CW laser and erbium-doped fiber amplifier at 1550 nm as the pump source, which serves to decrease the cost of the experiment and increase the pump power. The edge emission from the waveguide is sent into a Fabry-Perot cavity with an InGaAs detector, and the optical pump power is increased until coherence is achieved, which results in the observance of modes in the Fabry-Perot cavity. This measurement can be performed with much lower pump power than a measurement using a high-resolution spectrometer. In this work, we demonstrate the use of this method for measuring the optical emission from GeSn waveguides with Sn concentrations of 4-7%.
TEMPO-Modified Linear Poly(ethylenimine) for Immobilization-Enhanced Electrocatalytic Oxidation of Alcohol
Authors: Hickey David P , Milton Ross D , Chen Dayi , Sigman Matthew S , Minteer Shelley D. 
Published: February 2020

Small molecule electrooxidation catalysts such as (2,2,6,6-tetramethylpiperidin-1-yl)oxyl (TEMPO) are capable of electrochemically oxidizing short chain alcohols and various sugars to the corresponding aldehydes and carboxylic acids under physiological aqueous conditions. This makes them ideal alternatives to enzymatic catalysts when deeper oxidation of a fuel is desired in the anodic compartment of a biofuel cell. While enzymes are capable of very fast rates of electrochemical alcohol oxidation (when compared to that of either transition metal catalysts or small organic catalysts), their activity is often limited to a small range of substrates. Therefore multiple oxidative reactions with a single molecule of fuel requires that several redox enzymes be immobilized at an electrode surface simultaneously, which results in additional complexity as well as diffusional limitations as substrate travel between a specific sequence of active sites.
Alternatively, TEMPO has been recently shown to catalyze multiple sequential oxidations in situ of the biofuel glycerol thereby allowing for the collection of up to 12 electrons per molecule of fuel. However, in order to utilize TEMPO in a fuel cell application, the catalyst must be immobilized at the electrode surface, and previous methods for TEMPO immobilization have resulted in a dramatic loss of catalytic activity due to diffusional restrictions. Thus there is still a need for immobilization techniques that do not result in activity loss.
We have developed a method to immobilize a TEMPO catalyst in a cross-linked hydrogel film at the surface of a carbon electrode that allows for a dramatic increase in the rate of electrocatalytic oxidation of several sugars and short-chain alcohols. A TEMPO derivative was covalently attached to a linear poly(ethylenimine) backbone, and the modified polymer was cross-linked onto the surface of a glassy carbon electrode. The use of a hydrogel film allows for a porous network through which substrate can freely diffuse and the use of a polyamine provides a high localized concentration of base necessary for the catalytic cycle of TEMPO.
Oxidation Characteristics with Various Fuels in a Molten Carbonate Fuel Cell
Authors: Kim Tae-Kyun , Kim Yoo-Jeong , Lee Sang-Woo , Lee Choong-Gon 
Published: February 2020

This work has been focused on the effect of CO2 and H2O on the overpotential at the cell performance. A reference of Ang and Sammells, the reaction of hydrogen oxidation in molten carbonate has positive orders with the partial pressures of H2, CO2, and H2O. Therefore, the anode requires three gases for H2 oxidation. When the conventional H2 gas (H2:CO2:H2O=0.69:0.17:0.14atm) is used, then the overpotential is expected due to a lack of the CO2 and H2O. Ash free coal (AFC) was employed which was produced by a microwave method with a polar solvent of NMP. Adding CO2 to the AFC fuel in a coin type molten carbonate fuel cell (MCFC), the cell performance was analyzed with electrochemical method of steady state polarization and step chronopotentiometry. It was found that lack of CO2 and H2O induced significant overpotential in the MCFC and generation of them at polarization state mitigated the overpotential.
Effect of Water Adsorption on Conductivity in Epitaxial Sm0.1Ce0.9O2
-δ Thin Film for Micro Solid Oxide Fuel Cells Applications
Authors: Yang Nan , Strelcov Evgheni , Belianinov Alex , Tebano Antonello , Foglietti Vittorio , Schlueter Christoph , Lee Tien-Lin , Jesse Stephen , Kalinin Sergei V. , Balestrino Giuseppe , Aruta Carmela 
Published: February 2020

The growing demand for miniaturized systems for energy conversion and storage has prompted extensive research aimed at fabricating electrochemical devices, such as solid oxide fuel cells for portable applications (μ-SOFCs). This goal requires reducing the operating temperature by producing components as thin films. Nowadays, there is a huge gap between macroscopic device-level electrochemical techniques and microscopic electrochemical techniques to study atomic-level diffusion and transport process.
Recently, a new scanning probe microscopy technique, named electrochemical strain microscopy (ESM) has been developed in order to study the structure and physical properties on the microscopic level. After applying the dc bias to the tip, the oxygen vacancies and protons injection or annihilation can occur, depending on the working conditions and the material properties. The subsequent oxygen ion or proton movement results in localized strain under the tip, which can be detected through dynamic surface displacement.[1] This technique can be very useful to investigate the electrochemical activity at the nano-scale in ionic or proton conductors.
In this presentation, I will discuss several examples of high-resolution studies of pure and Sm-doped CeO2 epitaxial thin films surfaces which allowed to understand water interaction and conductivity mechanisms on the nanoscale. In particular I will show:
(1) The effect of the different doping concentrations on Sm1-xCexO2-a in terms of different transport mechanism and different type of charge carriers [2].
(2) The role of granularity and porosity on the oxygen ion or proton conduction 20% Sm doped CeO2 nanocrystalline films [3].
(3) The bias dependent mechanisms of irreversible cathodic and anodic processes on a pure CeO2 film.[4]
[1] A. Kumar et al. Nature Chemistry, 2011, 3,707.
[2] Nan Yang et al. ACS Nano DOI: 10.1021/nn505345c (2014)
[3] S. Doria, Nan Yang, et al. Appl. Phys. Lett. 103, 171605 (2013)
[4] Nan Yang et al. Nanotechnology 25, 075701 (2014).
Highly Confined Electronic and Ionic Conduction in Oxide Heterostructures
Authors: Pryds Nini 
Published: February 2020

The conductance confined at the interface of complex oxide heterostructures provides new opportunities to explore nanoelectronic as well as nanoionic devices. In this talk I will present our recent results both on ionic and electronic conductivity at different heterostructures systems.
In the first part of my talk I will show some of our resent results that we demonstrated the possibility of stabilizing δ-Bi2O3 using highly coherent interfaces of alternating layers. Remarkably, an exceptionally high chemical stability in reducing conditions and redox cycles at high temperature, usually unattainable for Bi2O3-based materials, is achieved[1]. These confined heterostructures provide a playground not only for new high ionic conductivity phenomena that are sufficiently stable but also uncover a large variety of possible technological perspectives.
At the second part, I will discuss and show our recent results of high mobile samples realized by, interface confined redox reactions
[2]
, strain induced polarization
[3]
and modulation doping at complex oxide interfaces. This collection of samples offers unique opportunities for a wide range of rich world of mesoscopic physics.

[1] S. Sanne et al. “Enhancement of the chemical stability in confined δ-Bi2O3”. Nature Materials (2015) doi:10.1038/nmat4266
[2] Y. Z. Chen et al. “A high-mobility two-dimensional electron gas at the spinel/perovskite interface of γ-Al2O3/SrTiO3”. Nature Commun. 4, 1371 (2013)
[3] Y. Z. Chen et al. “Creation of High Mobility Two-Dimensional Electron Gases via Strain Induced Polarization at an Otherwise Nonpolar Complex Oxide Interface” Nano Letters. 3774-3778 (2015) 10.1021/nl504622w