bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effects of Doping, Strain and Size on the Electrical Properties of MoS2 Nanoribbons
Authors: Yu Sheng , Li Qiliang , Eshun Kwesi 
Published: February 2020

Two-dimensional (2D) transition metal dichalcogenides (TMDs), such as isolated monolayers or few-layers of MoS2 and WSe2, have recently gained intensive interest for their potential in future electronics [1]. The bulk of TMDs usually have a layer structure which is similar to graphene. Because the layers are bound together by weak van der Waals forces, an isolated monolayer of TMDs can be easily obtained by cleaving technique. Unlike graphene, these 2D materials have a significant band gap and exhibit attractive semiconductor properties. Therefore, the 2D TMDs have been widely considered for the ultimately thin channel materials in future Metal-Oxide-Semiconductor Field Effect Transistors (MOSFETs) to suppress short channel effects. Especially, TMD monolayers usually have a direct band gap, very attractive for the mixed electronic and photonic application in future logic and memory devices [2].
During the integration of these 2D materials into electronic devices, e.g., as the channel materials in MOSFETs, they will be defined by lithography into nanoribbons, doped into n- or p-type, and stressed by the strain induced from the metal contacts and dielectric interface. In this work, we have studied the effects of these factors on the band structure and electrical properties of MoS2monolayers by using a numerical simulation method based on density functional theory. We found that the doping, strain and size could induce significant variation in the electrical properties of these 2D materials. These will be very challenging issues for the 2D materials.
In this work, we first studied the size effect on the properties of MoS2 monolayer nanoribbons. We found that the band gap of MoS2 nanoribbons changed from 1.8 eV of an infinite MoS2 sheet to 1.2 eV of a 10×10 (in molecule) MoS2 nanoribbons or 0.5 eV of a 5×10 MoS2 nanoribbons. We also found that the doping level and dopant position have a significant effect on the electrical properties of MoS2 nanoribbons. The doping level and dopant position can induce large variation (30%) in sheet resistance. This variation in electrical properties may post a serious challenge on the application in logic and memory devices. In addition, we found that the strain will also significantly affect the electrical and carrier transport properties of MoS2 monolayer. Under different strain, the MoS2 will change from direct band-gap to indirect band-gap semiconductor. As the strain further increases to certain value, the MoS2will become metallic.
In summary, this work demonstrated that the size, doping and strain have a significant effect on the 2D materials and will induce large variation in electrical properties. Therefore, the future integration of such 2D materials for logic or memory circuit application, the size, doping and strain must be well engineered and controlled in order to minimize the device variation.
References:
1. B. Radisavljevic et al., Nat. Nano. 6, 147 (2011)
2. Z. Yin et al., ACS Nano. 6, 74 (2012)
1D Photonic and Electrochromic Nanomaterials Applications
Authors: Redel Engelbert 
Published: February 2020

Porous hierarchical and photonic materials assemblies will be presented from a library of different metal oxide nanomaterials and hierarchical multilayer constructions. Potential applications of such materials will be presented, reaching from optical and tune able and porous 1D photonic crystals (PCs) to transparent and conductive oxides (TCOs) porous thin films, white light broad-band bragg reflectors as well as electrochromo-photonic switches. Furthermore, the optical and dielectric properties of single porous SURMOF thin films as well as multilayered photonic SURMOF-Hybrid and electrochromic SURMOF materials will be presented.
1 a) E. REDEL, C. HUAI, M. RENNER, G. V. FREYMANN, G. A. OZIN SMALL 2011, 7, 3465-3471. b) E. REDEL, P. MIRTCHEV, C. HUAI, S. PETROV, G. A. OZIN ACS NANO, 2011, 5, 2861-2869.
2 E. REDEL, C. HUAI, S. PETROV, D. OMER, P. O'BRIEN, M. G. HELANDER, J.MLYNARSKI, G. A. OZIN, SMALL 2012, 8, 3806-3809.
3 E. REDEL, J. MLYNARSKI, J. MOIR, A. JELLE, C. HUAI, S. PETROV, M. G. HELANDER, F. C. PEIRIS, G. V. FREYMANN, G. A. OZIN Adv. Materials 2012, 24, OP265-OP269.
4 E. REDEL, Z. WANG, S. WALHEIM, J. LIU, H. GLIEMANN, C. WOELL, Appl. Phys. Lett. 2013, 103, 091903; doi: 10.1063/1.4819836
5 J. LIE, E. REDEL, S. WALHEIM, Z. WANG, V. OBERST, J. LIU, S. HEISSLER, A. WELLE, T. SCHERER, M. BRUNS, H. GLIEMANN, C. WOELL Adv. Materials 2014, doi: adma.201402505
Micro-Fabrication of a Compact Air-Breathing Microfluidic Fuel Cell and Its Electrochemical Evaluation for Formic Acid and Glucose
Authors: Chávez Ulises , Dector Andres , Moreno Alonso , Ledesma-García Janet , Arriaga Luis Gerardo 
Published: February 2020

Microfluidic fuel cells (μFFC) are emerging as a promising solution for small-scale power demands. Some fuels frequently used in microfluidic fuel cells are formic acid [9–13], methanol [14,15] and glucose [16–18]. This work reports the air-breathing μFFC evaluation using 1.5 M formic acid in 0.5 M H2SO4 or 5 mM Glucose in KOH as fuels and the integration of an air-exposed electrode as cathode enabling oxygen delivery directly from air.
The formic acid μFFC employed Pd/XC-72 and Pt/XC-72 as electrocatalyst for anode and cathode respectively. Moreover, Au/C and Pt/XC-72 were employed as anode and cathode respectively for the glucose μFFC.
Both μFFCs were assembled using a polymethylmethacrylate (PMMA) plate where the microfluidic channel was engraved as shown in figure 1. Polarization curves were obtained from an Epsilon/Bas potentiostate 1.40.67 (Bioanalytical Systems).
Fig. 1. Schematic diagram of the air-breathing μFFC. All elements were assembled and tightened homogeneously by screws. The μFFC microchannel is 900 µm wide, 2 cm long and 50 µm depth; the electrode active area is 0.09 cm2.
The maximum power densities achieved were 27 mW cm-2 for the formic acid μFFC and 1.63 mW cm-2 in the case of glucose μFFC. These results have shown that the oxygen reduction reaction have been enhanced by the air-breathing adaptation in comparison with similar acid formic or glucose-μFFCs which operate with an oxygen-saturated aqueous stream.
Study on a Microchip-Integrated Hemorrheology Analysis System
Authors: Chen Li , Zheng Xiao-lin , Hu Ning , Jiang Fan , Lin Bing-wen , Yang Jun , Liao Yan-jian , Luo Hong-yan 
Published: February 2020

Blood circulation disorders are usually caused by abnormal blood rheology properties, among which blood viscosity is the most important physiological parameter. The level of blood viscosity can reflect blood transportation situation and blood supply. Along with the increase of viscosity and circulation resistance, blood flow velocity slows down. Blood flow to organs and tissues, especially microcirculation perfusion is inevitably reduced. Thus, ischemia hypoxia will result in tissue metabolism and function, even further symptoms of disease.
Although there are many pathogenic factors, such as hypertension, coronary heart disease, diabetes, cancer, peripheral vascular disease and anxiety, they are all related to abnormal blood viscosity. Currently most blood viscosity measuring instruments are single-purpose, expensive and non-portable, which can't fully satisfy patients’ requirements. In this paper, a rapid, accurate and versatile rheological analysis based on microfluidic systems is designed and realized. The system consists of micro-injection module, microchip module, image acquisition module and data analysis module. First, diluted blood was injected into a chip via micro-injection module. Furthermore, image acquisition module collected pictures of flowing liquid. By the analysis of data analysis module, we could obtain the viscosity of blood.
It’s worth mentioning that a novel lensless imaging device was designed and applied to image acquisition module compared with conventional microscopy at high magnification observation method. This device offers a relatively good image quality and has some obvious advantages as simple, low cost, small volume. Our experiment was carried on by using microscope imaging system, lensless imaging device and a commercial rheometer. Relative parameters were obtained and analyzed carefully.
Influence of Electrolytes on the Electronic Transfer in Electrode Materials: Ex- and In-Situ Dielectric Spectroscopy Study between 103 and 1010 Hz
Authors: Badot Jean-Claude , Seid Kalid Ahmed , Perca Cristian , Dubrunfaut Olivier , Soudan Patrick , Guyomard Dominique , Lestriez Bernard 
Published: February 2020

The fruitful contribution of Broadband Dielectric Spectroscopy (BDS) to study hierarchical materials applied to batteries electrodes has been previously shown [1-5]. The results demonstrate that the broadband dielectric spectroscopy technique is very sensitive to the different scales of the electrode architecture involved in the electronic transport, from interatomic distances to macroscopic sizes, as well as to the morphology at these scales, coarse or fine distribution of the constituents. When the frequency increases, different kinds of polarizations appear from interatomic distances to macroscopic sizes (Fig. 1) and give rise to dielectric relaxations in the following order: (a) space-charge polarization (low-frequency range) due to the interface sample/current collector; (b) polarization of clusters of particles (micronic scale) and (c) polarization of particles due to the existence of resistive junctions between them; d) electron transfers (nanometric or interatomic scale).
The BDS measurement was up to now ex situ measurement, on dry electrode. They provide a fundamental insight into the conduction properties at all scales of the materials before being integrated in a real battery. An innovative device (measurement cell) has been developed to make synchronized BDS measurements and electrochemical cycling. The frequency range is about 103 - 1010 Hz. In this work, data acquisitions were made on dry electrode (LiNi1/3Co1/3Mn1/3O2 / Carbon black / PVdF) and then on the same electrode wetted with an electrolyte. Short- and long-range motions of ions are evidenced in the low-frequency region. At higher frequencies, the study shows for the first time the influence of the ions of the electrolyte on the transfer of the electronic charges (holes) in LiNi1/3Co1/3Mn1/3O2at the micronic scale.

Acknowledgements

Financial funding from CNRS, Université de Nantes, UMICORE, and the ANR program n° ANR-09-STOCK-E-02-01 is acknowledged.

References

1. J.C. Badot, E. Ligneel, O. Dubrunfaut, D. Guyomard, and B. Lestriez, Adv. Funct. Mater. 2009, 19, 2749.
2. J.C. Badot, E. Ligneel, O. Dubrunfaut, J. Gaubicher, D. Guyomard, B. Lestriez, Phys. Chem. Chem. Phys. 2012, 14, 9500.
3. K. Seid, J.C. Badot, O. Dubrunfaut, S. Levasseur, D. Guyomard, B. Lestriez, J. Mater. Chem. 2012, 22, 2641.
4. K. Seid, J.C. Badot, O. Dubrunfaut, S. Levasseur, D. Guyomard, B. Lestriez, J. Mater. Chem. 2012, 22, 24057.
5. K. Seid, J.-C. Badot, O. Dubrunfaut, M.T. Caldes, N. Stephant, L. Gautier, D. Guyomard B. Lestriez. Phys. Chem. Chem. Phys. 2013, 15, 19790.

Figure 1. Schematic description of a hierarchical architecture at different scales of a powdered material: different sources of polarizations vs. frequency and size.
State-of-Charge Mapping with Spatially Resolved XPS in Patterned Thin Film Battery Electrodes
Authors: Pearse Alexander J , Gillette Eleanor , Rubloff Gary W 
Published: February 2020

Nanostructures offer the opportunity to design-in higher power capability and cycling robustness, but their spatial distribution of active ion storage material can pose major challenges in transporting electrons to all regions of active material. For example, high aspect ratio nanowire or nanotube electrodes on a planar current collector may require electrons to diffuse 10’s – 100’s μm though highly resistive oxide material before meeting an incoming lithium ion. While adding a conformal or coaxial current collector can improve performance at high rates, the characterization of this improvement must typically be inferred though bulk electrochemical measurements.
In this work, we develop a model system with which to directly measure the spatial distribution of state-of-charge (SOC) for a poorly conductive cathode material as a function of distance from a current collector and discharge rate using spatially resolved x-ray photoelectron spectroscopy (XPS). Our system includes a geometrically restricted electrode/current collector interface but a relatively unrestricted electrode/electrolyte interface. We fabricate electrodes with patterned planar current collectors using standard microfabrication techniques and deposit pinhole-free ultrathin films of the cathode material V2O5 using atomic layer deposition. These cathodes are then discharged in a liquid electrolyte under different rates and conditions, and the resulting SOC distribution is mapped using XPS with a lateral resolution as good as 15µm. Unlike microspot Raman or XRD, XPS provides a direct quantitative measurement of the SOC through the concentration of lithium ions and/or reduced vanadium ions (Figure 1). The latter is particularly appealing in that it is independent of surface contamination, providing an avenue towards SOC characterization even in the presence of a thin SEI layer. We also explore the depth dependence of the SOC using angle resolved XPS and ion beam depth profiling. Our measurements demonstrate that the electrode SOC decreases over a distance of order millimeters from the current collector at moderate rates, and that the shape and magnitude of the SOC gradient depends on the discharge rate. Finally, we compare our observations with simulations of the structure using COMSOL Multiphysics, and attempt to resolve discrepancies between the two. We believe this approach can provide design guidance for heterogeneous nanostructures applied to electrical energy storage. We anticipate this technique to be broadly applicable to other electrode materials and active ions.
Bis(fluorosulfonyl)Amide Anion Transfer at Graphite Electrode
Authors: Abe Takeshi , Miyazaki Kohei , Fukutsuka Tomokazu 
Published: February 2020

As is well-known, many atoms and molecules can enter into graphite to form graphite intercalation compounds GICs). The application of GICs ranges from lithium-ion batteries to hybrid capacitors. The hybrid capacitor, which utilizes anion intercalation/de-intercalation at graphite positive electrode, can possess higher energy densities than electric double layer capacitors whose capacity is dominated by the amount of cation and anion adsorbed (desorbed) on activated carbons.
To increase the capacities of hybrid capacitors, it is necessary to increase the amount of anions intercalated into graphite. In other words, low-stage graphite intercalation compounds (GICs) must be formed. For the electrochemical anion intercalation, low-stage GICs are synthesized at higher potential exceeding 4.5 V vs. Li+/Li and therefore, oxidative decomposition of electrolyte solutions are not negligible at such high-potential region. Here we report electrochemical intercalation/de-intercalation properties of various anions at graphite electrodes, and show the anion intercalation kinetics.
XPS Study of the Porous Carbonaceous Positive Electrode Interface in Li-O2 Batteries upon Cycling
Authors: Guéguen Aurélie , Berg Erik J. , Novák Petr 
Published: February 2020

Deep understanding of the reactions taking place upon cycling between the reduced oxygen species and the electrolyte and the porous electrode components is required in order to improve the electrochemical performance of Li-O2 batteries. Electrochemically formed products deposit in nano-meter thin layers on the cathode. X-ray Photoelectron Spectroscopy (XPS) is the most suitable characterization technique to investigate the extreme surface of materials.
0.2 M LiTFSI in diglyme was chosen as electrolyte for our study. In order to evaluate the influence of the nature of the carbon cathode on the electrochemical properties of the cell, electrodes containing different carbons (graphite SFG6 (TIMCAL), amorphous carbons Super C65 (TIMCAL)) were prepared by mechanical rolling using PTFE as a binder. The specific charge at the end of the 1st discharge was lower for graphite SFG6 (76-96 mAh/g) than for Super C65 (~ 350 mAh/g). It is consistent with the lower specific surface area of the graphite SFG6 (16 m2/g) compared to Super C65 (60 m2/g).
XPS data were collected on the carbonaceous electrodes at the end of the first discharge. For all electrodes the component belonging to the carbon backbone dominates the C 1s spectra (Figure 1c), indicating a thin interface layer (≤5 nm). LiF was detected at the surface of both electrodes but in a higher amount for graphite SFG6 (Figure 1a). Components at 54.8 and 531.7 eV on the Li 1s and O 1s spectra for the electrode containing amorphous carbon Super C65 can be attributed to the presence of Li2O2 (Figure 1a and 1b), but were not observed for graphite SFG6. Hence the type of carbon has an influence on the chemical composition of the interface layer formed on its surface upon discharge. In both cases, electrolyte degradation could be evidenced by presence of components on the C 1s spectrum at 287, 289 and 290 eV resulting from degradation of the diglyme. Upon the following charge, most of the discharge products disappear.
Mesoscopic Li Distribution Analysis on an All Solid Battery
Authors: Saito Toshiya , Yamazaki Akiyoshi , Kamiya Tomihiro , Fujita Kazuhisa , Mima Kunioki , Kato Yoshiaki , Iba Hideki 
Published: February 2020

All solid batteries (ASB) are one of the most promising candidates for post Li-ion battery, especially for large scale applications such as electric vehicle, plug-in hybrid vehicle and stationary use. The most characteristic feature of ASB is that organic solvent in a Li-ion battery is replaced by inorganic solid electrolyte. It is generally expected wider operation temperature and higher thermal stability than conventional liquid Li-ion battery derived from nature of solid electrolyte.
On the other hand, there are several obstacles for the practical application of ASB. One of the major drawbacks is the poor power density of the ABS. We sometimes face to large “interfacial resistance” of electrodes in the ASB. The origin of interfacial resistance is cracks and/or resistive layer between active material and solid electrolyte. To figure out a quantitative view of the poor power density, it is useful to observe Li ion distribution in an electrode especially under working condition, i. e. in-situ observation of Li distribution in an ASB.
Recently, it was reported that the ion beam analysis is applicable to observe Li atom distributions in an electrode of Li-ion battery [1]. The principle of this method is to analyze Li and/or other elements by detecting γ-ray, X-ray or charged particles. When a high energy proton beam is irradiated on an electrode, characteristic X-rays are emitted from transition metal elements through ionization interaction, and , γ-ray or α-particles from 7Li through nuclear reaction of 7Li(p, p’γ)7Li or 7Li(p, α)4He, respectively. At the Takasaki Institute of Japan Atomic Energy Agency, high energy proton micro-beam was irradiated on samples. The minimum diameter of the beam was focused down to about 1 μm. This means that 2D elemental images of a sample including Li can be obtained with μm resolution. We’ve tried to apply this new analysis technique to an ASB. The result will be shown in the conference and the possibility of in-situ observation will be discussed.
Acknowledgement:
This work was supported by funding received from the CONCERT-Japan Joint Call on Efficient Energy Storage and Distribution, and by the Japan Science and Technology Agency, the Spanish Ministry of Economy and Competitiveness, the German Federal Ministry of Education and Research and the German State of North Rhine-Westphalia.
Reference:
[1] K.Mima, et al.," Distribution characterization in Li-ion batteries positive electrodes containing LixNi0.8Co0.15Al0.05O2 secondary particles", Nucl. Instr. Meth. B, 290 (2012) 79-84
Effect of Asymmetric Performance of Ionic Liquid Electrolyte Ions on Maximum Operation Potential of Symmetric Supercapacitors
Authors: Van Aken Katherine L , Beidaghi Majid , Gogotsi Yury 
Published: February 2020

While known for their high-power performance compared to batteries, supercapacitors
lack the energy density capability for some energy storage applications. Since the
energy density of the device is proportional to the square of operating potential window,
increasing the potential window is an effective way to increase energy density of the
device. Ionic liquid electrolytes are beneficial for this reason since they can theoretically
operate at up to 6 V, though experimentally, the value is between 3-4 V depending on
the properties of electrode materials. By employing a novel electrochemical technique to
study symmetric supercapacitors of carbon electrodes and ionic liquid electrolytes, we
have found one of the possible reasons for smaller operation potential of ionic liquids
in practical applications. We observed that even for a symmetric device with electrodes
similar in size and weight, the different properties of cations and anions of the electrolyte
results in an asymmetric performance of the two similar electrodes. By performing a
systematical study on model electrode materials and ionic liquid electrolyte systems, we
show that a symmetric behavior of the electrode can be achieved by mixing ionic liquids
with different cation and anion properties. This ultimately results in a higher operation
potential window of the device and higher energy density. In our model electrochemical
device, onions like carbons (OLCs) were used to fabricate the device electrodes and two
ionic liquids EMI-TFSI and EMI-BF4 and their mixtures were used as electrolytes.
Digital Control of DC-DC Converters Employing Wide Band Gap (WBG) Power Devices
Authors: Guo Liping , Pozo Arribas Alejandro , Krishnamurthy Mahesh , Shenai Krishna , Wang Ju 
Published: February 2020

DC-DC converters are used at the Advanced Photon Source (APS) at Argonne National Laboratory to power electromagnets. The electromagnets guide the photon beams, therefore the control system of the DC-DC converters should be highly accurate to provide minimum spatial spread of the beam. Currently the converters have all been regulated by analog control systems. An upgrade to digital control system is being evaluated to resolve the aging and obsolescence issues.
This paper describes the design and evaluation of a digital control system to regulate the output current and reduce noise coupled in the system. A digital controller is first designed based on the small signal model of the converter. Experimental data of the output current is analyzed. Digital filters are then designed to reduce the noise in the output current. The complete control system is then simulated and results are evaluated. Wide Band Gap (WBG) power devices enable the development of smaller and more durable power converters with higher performance and less power consumptions than traditional silicon devices. Performance of the digital controlled DC-DC converters using WBG power switching devices including silicon carbide (SiC) power MOSFETs and gallium nitride (GaN) power transistorswill be evaluated, in comparison with the converters using traditional silicon power switching devices.