bluuebunny/crossref_metadata_2025_split huggingface dataset:
Characteristics of Inkjet-Printed Separators in Graphene-Based Supercapacitors
Authors: Yang Yong Suk , You In-Kyu , Hong Sung-Hoon , Yun Ho-Gyeong 
Published: February 2020

Electrochemical capacitors such as a supercapacitor store electrical charge on high-surface-area conducting materials.1,2 Supercapacitors store energy by forming a double layer of electrolyte ions on the surface of conductive electrodes. They are not limited by the electrochemical charge transfer kinetics of batteries and thus can operate at very high charge and discharge rates. Graphene is a promising material for energy storage, especially for high performance supercapacitors. For real time high power applications, it is critical to have high specific capacitance with fast charging time at high current density.3,4

In this study, we prepared the separators of supercapacitors on cellulous films and papers by using an inkjet printing technology. Several different ink materials such as carbon nanotubes and metal oxides were introduced and the influence of the base materials used as separator was also investigated. The supercapacitors with a graphene nanoparticle composite as electrodes showed a specific capacitance of up to 100 F/g. The inkjet printing conditions such as pulse voltages and pressures were carefully controlled to maximize the performance of supercapacitors. The interface topologies and electric properties of the so formed supercapacitors were investigated by a scanning electron microscope and the measuring system of charge-discharge cycles, respectively.
References
1. R. Kotz and M. Carlen, Electrochimica Acta, 45(15-16), 2483-2498 (2000).
2. K. Sahay and B. Dwidevi, J. Elec. Systems, 5, P8 (2009).
3. X. Xie, L. Qu, C. Zhou, Y. Li, J. Zhu, H. Bai, G. Shi, and L. Dai, ACS Nano, 4, 6050 (2010).
4. C. Liu, Z. Yu, D. Neff, A. Zhamu, and B. Z. Jang, Nano Lett., 10, 4863 (2010).
Room-Temperature Defect-Enabled Spin Functionality in GaAs-Based Coumpound Semiconductors
Authors: Chen Weimin M , Buyanova Irina A 
Published: February 2020

Semiconductor spintronics is a newly emerging research field that explores the spin degree of freedom, in addition to charge of the electron, for future electronics, photonics and quantum information technology. The success of spintronics relies on our ability to create, maintain, manipulate and detect spin orientation and coherence at room temperature (RT). During recent years, we have witnessed impressive progresses in developments of novel concepts and innovative approaches in these areas. Unfortunately, a vast majority of earlier achievements have been restricted to cryogenic temperatures and with a rather low efficiency, often requiring an external magnetic field. Here, we present our recent work on a new and unconventional approach of RT defect-enabled spin functionality in a non-magnetic semiconductor without requiring a magnetic layer or external magnetic fields. We demonstrated efficient spin filtering in Ga(In)NAs thin films and nanostructures, enabled by Ga self-interstitials, which is capable of generating a remarkably high spin polarization degree (> 40%) of conduction electrons at RT [1]. We also provided the first experimental demonstration of an efficient RT spin amplifier based on defect engineered Ga(In)NAs with a spin gain up to 2700%! [2] Such a spin amplifier is shown to be capable of amplifying a fast-modulating input spin signal while truthfully maintaining its time variation of the spin-encoded information. By taking advantage of the spin amplification effect, we showed that Ga(In)NAs quantum structures can be employed as efficient RT optical spin detectors, with spin detection efficiency well exceeding 100%. Combining the spin-filtering effect and hyperfine coupling, we further achieved the first realization of RT nuclear spin hyperpolarization in semiconductors via conduction electrons [3], relevant to practical applications of future solid-state quantum computation using nuclear spin qubits and in highly sensitive magnetic resonance imaging. We also demonstrated the potential of such spin engineering to significantly improve performance of spin light-emitting devices and efficiency of photovoltaic devices. Such approaches could potentially provide an attractive, alternative solution to the current and important issues on RT spin-functional semiconductors for future spintronics and spin-photonics.
[1] X.J. Wang et al. Nature Materials 8, 198 (2009)
[2] Y. Puttisong et al. Adv. Materials 25, 738 (2013).
[3] Y. Puttisong et al., Nature Communications. 4, 1751 (2013).
The Role of Passivation Layer during Thermal Annealing for Oxide Semiconductor Thin Films
Authors: Hwang Chi-Sun , Park Sang-Hee Ko , Cho Sung-Heang , Ryu Min Ki , Oh Himchan , Lee Su Jae , Yang Jong-Heon , Byun Chunwon , Park Jonghyurk , Cho Kyung Ik , Chu Hye Yong 
Published: February 2020

Oxide TFTs have been considered as a good candidate for the application to backplane device for high quality TFT-LCD and large area OLED panel. It is well known that the passivation play the very important role for the development of the high quality oxide TFTs. The criteria for good passivation layer can be a barrier for environmental factors, not having doping source during thermal annealing, and playing a role of curing the defective interface.
The evolution of the resistance of active films during thermal annealing was monitored under the split of passivation layers and active layers. ALD deposited Al2O3 layer and PECVD SiO2 layer were applied for the passivation layer and sputter deposited Al-doped InZnSnO and InGaZnO were applied for the active layer.
It is found that Al2O3 passivation layer supplies dopants to the active interface (possibly H) during high temperature annealing and the side wall of AIZTO pattern contains many defects, which become dopants during high temperature annealing through detailed measurement of resistance of patterned oxide thin films with various sizes.
It is suggested that PECVD SiO2 with proper pre-treatment (possibly N2O plasma treatment) will be best candidate for the passivation layer in the oxide TFTs, especially in the case of oxide TFTs with high mobility.
Hybrid Nonvolatile Memory Devices with Ferroelectric Copolymers Based on ZnO Nanowire Field Effect Transistors
Authors: Chun Young Tea , Chu Daping 
Published: February 2020

Zinc Oxide (ZnO) nanowire (NW) field effect transistors (FETs) have been increasingly popular recently as promising circuitry building blocks. ZnO NWs have a relatively good ohmic contact between the metal electrodes and semiconductor materials, which results in a high device performance and fabrication yield. At the same time, organic thin film transistors (OTFTs) with ferroelectric materials have been researched extensively owing to their nonvolatile memory effect, nondestructive readout and applications to flexible electronics [1, 2]. However, research works on ferroelectric memory devices based NW FETs are still limited [3, 4], while that on their thin film counterparts are relatively widespread [5].
We will first introduce the nonvolatile memory device arrangement based on a ZnO NW FET. Single NW and network NW FET configurations are compared in terms of their associated ferroelectric memory properties. We will show our previous work on the ZnO NWs grown by a chemical vapor transport method on glass substrates [6] together with that by a hydrothermal method on flexible substrates, with the dimensions ranging from 100-300 nm in diameter and up to 5-10 um in length. Our ZnO NW FETs grown on flexible substrates directly shows a high current on/off ratio of up to 105-107with an anticlockwise hysteresis loop present on the transfer curve. The top-gate and bottom-gate structures have been prepared by spin coating a 5 wt% solution of ferroelectric PDVF-TrFE powders in cyclohexane. After spin coating, the ZnO NW FETs with PVDF-TrFE thin films have been thermally cured in a vacuum oven at 150°C for 5 hours. The device showed a memory window of at least 10-20 volts depending on the type of the substrates, which can be tuned by varying the sweep range of the gate voltages.
[1] T. Sekitani et al., Science 326, 1516 (2009).
[2] S.K. Hwang et al., Adv. Mater. 24, 5910 (2012).
[3] D. Yeom et al., Nanotechnology 19, 395204 (2008).
[4] Y.T. Lee et al., Adv. Mater. 24, 3020 (2012).
[5] K.H. Lee et al., Adv. Mater. 21, 4287 (2009).
[6] S. Nedic, et al., Appl. Phys. Letts. 104, 033101 (2014).
Comparative Systematic Study of Covalent Effects for the Cr3+-, Mn4+- and Ni2+-Doped Optical Materials
Authors: Srivastava Alok M , Brik Mikhail G. 
Published: February 2020

The Cr3+, Mn4+ and Ni2+ ions are widely used transition metal dopants. Laser generation was obtained on the 2Eg-4A2g spin-forbidden emission transition in a number of crystals and ceramics containing trivalent chromium; the same transition of the Mn4+ ions is used for getting red emission; the 1Eg-3A2g spin-forbidden transition of the Ni2+ ions is also used for lasing in the infrared region.
In the present work we review the spectroscopic properties of the Cr3+, Mn4+ and Ni2+ ions in a number of solids. The crystal field strength Dq, Racah parameters B, C and position of the first excited state were all tabulated.
In an attempt to quantify the collected information, we used the model recently developed by us (1-3), which allows to link together the energy of the spin-forbidden 2Eg-4A2g transition of the Cr3+ and Mn4+ ions or the 1Eg-3A2g transition of the Ni2+ ions and covalent effects in the considered crystals. To rationalize the variation of energy of these spin-forbidden transitions, we introduced a non-dimensional parameter
ß1=((B/B0)2+α(C/C0)2)1/2 , (1)
where the subscript “0” refers to the values of the Racah parameters for a free ion, and B and C are the Racah parameters for the same ion in a given crystal. The value of α was 1 for the Mn4+ and Ni2+ ions, and 1.5 for the Cr3+ ions. An advantage of our model is that it takes into account reduction of both Racah parameters B and C.
Fig. 1 shows that the energy of the Ni2+
1Eg→3A2g transition is linearly related to β
1 value (3). This indicates that any description of the nephelauxetic effect for the Ni2+ containing hosts must consider both Racah parameters B and C; the dashed lines in Fig. 1 mark the ±489 cm-1 corridor from the central fit line (this value is the rms deviation of the data points).
Figs. 2-3 depict dependence of the Cr3+ and Mn4+
2Eg→4A2g transition on the β
1 parameter, respectively Again, a linear trend can be seen clearly. The ±σ range (where σ stands for the rms deviation) is shown in both figures. The reason for some data points to deviate from the straight line can be related to the difficulties of unambiguous experimental identification of the zero-phonon lines, which can be hidden by prominent vibronic progressions. Still the maximal difference between the fitting line and mostly deviated data points is a few hundred wave numbers, which is within a typical range of the phonon frequencies for the majority of optical materials.
Further studies of the transition metal doped materials are under way; the main aim of these studies is to elucidate the common and different features in the behavior of the spin-forbidden transitions and covalency effects experienced by the transition metal ions in solids.
REFERENCES
1. A.M. Srivastava, M.G. Brik, J. Lumin.
132, 579, (2012).
2. M.G. Brik, A.M. Srivastava, ECS J. Solid State Sci. Technol.
2, R148, (2013).
3. M.G. Brik, A.M. Srivastava, N.M. Avram, A. Suchocki, J. Lumin.
148, 338, (2014).
Self-Propelled Motion of Oil Droplets on Au Electrode during Sn Electrodeposition
Authors: Shiono Tetsuaki , Mukouyama Yoshiharu 
Published: February 2020

INTRODUCTION
It was reported that macroscopic contact angles of an oil droplet put on an electrode surface decreased during electrodeposition of metals, such as Sn, Pb and Sb [1]. It was also reported that the difference in the contact angle between the front and rear sides of the droplet caused self-propelled lateral motion of the droplet [1]. This motion has attracted much interest from the viewpoint of the emergence of mechanical motion induced by chemical or electrochemical reactions.
Little has been reported about the factors affecting the velocity of the motion. It has only been reported that the velocity increases with a negative shift in the electrode potential [1]. In this work, we studied the factors affecting the velocity and the mechanism of the motion.
EXPERIMENTAL
The self-propelled motion of a nitrobenzene droplet on an Au ring electrode was observed during Sn electrodeposition (Sn2+ + 2e- → Sn) in H2SO4 + 0.01 M SnSO4. The volume of the droplet was about 1.0 μL. Figure 1 shows schematic of the experimental setup. In order to study the dependence of the velocity on the density of the aqueous electrolyte, K2SO4was added to the electrolyte to increase the density.
RESULTS and DISCUSSION
We studied the dependence of the velocity on the electrode potential when the concentration of H2SO4was 0.5 M. As shown in Figure 2, the droplet did not move, i.e., the velocity was zero, in the potential region above ca. -0.44 V, though the Sn electrodeposition occurred. On the other hand, the droplet moved in the potential region below ca. -0.44 V where both the Sn electrodeposition and hydrogen evolution reaction (HER) occurred. The velocity increased with a negative shift in the electrode potential.
In the potential region where the droplet moved, the Sn electrodeposition was limited by the mass-transport of Sn2+ions to the electrode surface, and hence the rate of electrodeposition was constant independently of the potential. We, therefore, think the velocity increase with a negative shift in the potential is probably attributed to the increase in the rate of the HER. Based on this idea, we suggest that the droplet motion is driven by the interaction between the Sn electrodeposition and the HER.
We also studied the dependence of the velocity on the density of the aqueous electrolyte. As shown in Figure 3, the velocity observed at -0.66 V vs. SHE increased as the concentration of K2SO4increased. That is, the velocity increased as the density increased. The buoyancy of the droplet increased with the increasing density, which probably led to the increase in the velocity.
This work is partially supported by the Research Institute for Science and Technology of Tokyo Denki University under Grants Q12E-02.
REFERENCES
[1] S. Nakanishi, T. Nagai, D. Ihara, Y. Nakato, Chemphyschem, 9 (2008) 2302-2304.
New Computational Insights to Describe the Oxygen Reduction Reaction on Graphene Containing Multiple Nitrogen Functional Groups
Authors: Ortiz-García H. , Vazquez-Arenas J. , Galano Annia , González Ignacio 
Published: February 2020

The development of new cathodes for low temperature fuel cells has spurred the research of low cost and durable materials, particularly non-noble materials displaying a similar performance as Platinum [1]. To this concern, metal-free nitrogen doped graphene containing various nitrogen functional groups (quaternary, pyrollic, and pyridinic species) have been found to facilitate the electrocatalysis of Oxygen Reduction Reaction (ORR) as in traditional Pt-based catalysts [2]. Atomistic simulations have been conducted to describe the ORR mechanism on different carbonaceous materials. However, these analysis have mostly been dedicated to Platinum (Pt)-based catalysts, and single nitrogen groups on Carbon nanotubes (CNTs) [3]. Thus, this study is oriented to account for the quantum mechanics interactions arising during the ORR on N-doped graphene structures containing pyridinic, pyrollic and quaternary species. Density functional theory is utilized to compute the Gibbs energy of the adsorbed intermediates and chemical species (e.g. H, OOH, H2O2, OH, O, and O2) formed during the course of the ORR mechanism. The calculations evaluate the scale-up of the cluster in order to screen out local effects due to dimensions, and the reactivity of the aforementioned species on all possible catalytic sites (refer to positions a,b,c, adjacent to C1, C2, PR, PD in figure 1a). It was found that H, OOH, OH, O, and O2 preferentially chemisorb or physorb on the quaternary site C1-a, whereas H2O2 species reacts favorably on C2-b.

Keywords: ORR, DFT, Pyridinic, Pyrollic, and Quaternary Species.
[1] Gong, K.; Du, F.; Xia, Z.; Durstock, M.; Dai, L., Science
2009, 323, 760.
[2] Biddinger, E.; Deak, D. v.; Ozkan, U., Top. Catal.
2009, 52, 1566.
[3] Hyman, M. P.; Medlin, J. W., J. Phys. Chem. B
2006, 110, 15338–15344.
LiCoPO4 Based High Energy Li-Ion Cathodes
Authors: Allen Jan L. , Wolfenstine Jeff , Allen Joshua L. , Jow T. Richard 
Published: February 2020

There is an ongoing need for higher energy batteries that operate with the highest safety margin. LiCoPO4 is a 4.8 V cathode material with potentially better abuse tolerance and energy density than the current state of art Li-ion battery chemistries. The intense development of high voltage electrolytes1 and strategies that improve the cycle life2, discharge capacity2 and rate capability3have increased the interest in this material.
This paper will review our recent efforts on LiCoPO4 electrode development for improving the energy and abuse tolerance of Li-ion batteries. We will discuss synthesis methods, transport measurements,3 substitutional chemistry of LiCoPO4 and performance enhancements that result from reformulating the electrolyte.
References

A. V. Cresce, A.V and K. Xu, J. Electrochem. Soc. 158, A337, 2011.

J. L. Allen, T. R. Jow, J. Wolfenstine, J. Power Sources 2011, 196, 8656.

J.L. Allen, T. Thompson, J. Sakamoto, C.R. Becker, T.R. Jow and J. Wolfenstine, J. Power Sources 254, 204 (2014).
Graphite-Based Negative Electrodes: Correlation of Electrode Expansion and Cyclability
Authors: Bünzli Christa , Cericola Dario , Hucke Thomas , Spahr Michael , Novák Petr , Gomez-Camer Juan Luis 
Published: February 2020

Silicon is the most attractive candidate to upgrade carbon as negative electrode material in lithium-ion batteries, due to its large specific charge and low reaction potential. However, the volume changes of silicon upon lithiation and delithiation lead to mechanical stress and poor performance, hindering the commercial use of silicon particles in lithium-ion battery negative electrodes. Many attempts to reduce the volume changes and achieve stable cyclability for silicon electrodes involve the use of carbon and/or graphite as electrochemically active matrix. Here we study the effect of silicon addition to graphite based electrodes and explore the differences in electrochemical response by means of in situ electrochemical dilatometry.
Electrodes based on TIMCAL graphites, TIMREX® KS6 and TIMREX® SLP30, and silicon nanoparticles have been prepared by a simple mixture procedure and coated on Cu foil by standard doctor blade coating technique. Electrochemical performance and cycling stability of the composite electrodes was explored in coin type cells cycled in EC:DMC 1:1w:w, 1M LiPF6 electrolyte using metallic lithium as counter electrode. Different parameters such as the nature of the binder, the effect of graphite morphology, and the use of electrolyte additives are studied in long term cycling experiments.
The expansion of electrode layers was measured in a special dilatometry setup using three-electrode configuration, with both counter and reference electrodes of metallic lithium. A similar cycling program was used to explore the electrode’s expansion, however only during the first few cycles. Differences observed in the expansion of the composite electrode layers help us to understand the distinct electrochemical behaviour of each graphite based system, with and without silicon particles.
Visualizing Longitudinal and Transversal Strain Effects in High-Energy NMC Cathodes Induced By Intense Calendering
Authors: Schünemann Jan-Hinnerk , Petri Ralf , Kwade Arno 
Published: February 2020

One of several challenges in improving the performance of lithium-ion batteries is the enhancement of energy density. Apart from the development of ever better active materials, considerable potential for improvement can be found in the complex manufacturing process. The manufacturing of lithium-ion battery cells exhibits a long, mostly sequential process chain with numerous interdependent parameters and quality-determining characteristics. Among slurry mixing and coating, calendering is the most challenging process step and considered of superior importance to the quality of the electrode. Calendering refers to compressing the porous coating layers of the electrode to a predetermined thickness. To obtain the desired energy density and to prepare a homogeneous electrode thickness it is necessary to densify the coating of the electrodes. In this, more electrochemically active material can be accommodated in every unit of electrode volume. In essence, this defines the potential energy density of the cell. As for high-energy battery cells energy density is one of the most important optimization criteria to achieve ambitious requirements for automotive applications calendering is of crucial importance.
However, compression of the electrode is not merely beneficial to the overall performance of the cell. It is a trade-off between achieving high energy density and, on the contrary, damaging the electrode’s structure by applying high mechanical forces. An effect rarely taken into account is mechanical strain induced to the electrode’s metal foil underlying the coating, which can lead to serious issues in manufacturing and malfunction of the battery cell.
This paper addresses macroscopic changes in electrode’s metal foils resulting from intense calendering procedures of high-energy NMC cathodes. Figure 1 exemplarily depicts an area-resolved longitudinal strain map showing irreversible deformation from calendering. The left green section reflects an uncoated edge of the electrode which is not deformed during calendering. The coated section of the specimen is deformed significantly. The data is derived from before/after comparison of the electrode’s surface, conducted with a non-contact optical 3D deformation measuring system. To minimize undesired strain inducement, multi-calendering strategies are assessed which gently apply loads and at the same time still provide for highly compressed electrodes.