bluuebunny/crossref_metadata_2025_split huggingface dataset:
Surface Analysis of Composite Cathodes in Li-Ion Batteries: SEI Composition As a Function of Spatial Origin and Cycling Protocol
Authors: Schulz Natalia , Hausbrand René , Jaegermann Wolfram 
Published: February 2020

With respect to stationary applications the demand of suitable storage technologies for electrical energy originates from discontinuous renewable primary energy sources has increased the interest in Li-ion batteries. In order to develop long lasting and cost efficient energy storage systems a comprehensive understanding of battery degradation mechanisms plays a fundamental role. Particularly the formation (and properties) of the cathodic solid electrolyte interface (SEI) under specific cycling conditions and its consequences on the mechanical fatigue has not been fully understood yet. Among the reasons are the limited number of studies published concerning the rudimentary analysis of composite electrodes. In this connection the analysis of the SEI layer on particles inside the electrode has not been performed yet. The main purpose of this work is a surface analysis of particles on the top and inside of the composite cathode after electrochemical cycling following a specific protocol.
This work deals with post mortem analysis of LiCoO2-composite cathodes by X-ray photoelectron spectroscopy (XPS). The electrodes were taken from 18650 type Li-ion cells, which were galvanostatically cycled under specific protocols. Analysis was performed of the top surface of the cathode and of material buried inside the cathode. To analyze the surfaces of buried material the top part of the cathodes has been mechanically removed. To improve the assignment of the XP-spectral features we used reference materials like LiCoO2 and SEI related components. We also performed experiments with pure LiCoO2-cathodes to analyze the SEI layer on the active material without interference from layers formed on other constituents of a composite cathode.
The surface analysis of electrochemically treated LiCoO2-composite cathodes showed a lower SEI thickness on buried material than on the top layer of the cathode. In both investigated locations of the electrode the same organic and inorganic (e.g. LixPOyFz-type) surface compounds were observed. We could determine that the proportion of the species in the SEI depends on the applied cycling protocol. Furthermore, the evaluated LiCoO2 of the composite showed changes in the electronic structure compared to the XP-spectral feature of the LiCoO2-reference material.
Systematic Variation of Sulfur Cathode Chemistry and Its Effects on Cell Performance
Authors: Perdue Brian Robert , Height Hannah E. , McBrayer Josefine , Apblett Christopher A. 
Published: February 2020

In recent years, tremendous effort has been invested into researching energy storage chemistries that will replace lithium ion. New strategies with higher capacities must be considered, such as a chemical conversion cathode. The lithium sulfur chemistry is a promising candidate as it uses earth abundant, inexpensive, high capacity sulfur as its cathode. Conversion cathodes like sulfur are much more challenging as a secondary battery, and behave differently than intercalation cathodes. Because of this, different design criteria must be applied to conversion cathodes to maximize power and capacity. The interplay of conductive network, insulating active cathode, and binder all give rise to differences in performance for the dissolution and precipitation of the cathode material. This work attempts to identify key design criteria for sulfur cathodes by systemically varying the basic components of cathode chemistry and structure. A matrix of ~110 different cathode formulations were fabricated by varying conducting carbon, % active material, binder system, and sulfur loading. Performance of these cathodes was evaluated by means of 2032 coin cell tests under constant current and pulsed loads. First discharge capacity, capacity retention, coulombic efficiency, impedance, cathode surface area, and cathode porosity are utilized to gauge the effectiveness of the cathode and explain trends observed in cycling tests. The effects of cathode rheology on porosity surface area and overall cathode utilization was also investigated. Observed differences in performance between different electronically conductive elements and different cathode support elements were observed, with nuanced changes in morphology resulting in significant performance changes.
Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-AC04-94AL85000.

Figure 1
(Invited) Emerging Ferroelectric Devices
Authors: Gruverman Alexei 
Published: February 2020

Ferroelectrics comprise a class of polar materials with an electrically switchable spontaneous polarization allowing their use as binary data storage media in nonvolatile ferroelectric random access memories (FeRAMs). Currently available FeRAMs utilize a destructive read process of stored information, which requires the memory cells to be re-written by a relatively high voltage, increases the read time and limits the scalability. An alternative approach to the read operation is based on the polarization-driven resistive switching, known as the tunneling electroresistance (TER) effect. If the ferroelectric film is sufficiently thin (of the order of several nanometers), conduction electrons can quantum-mechanically tunnel through the ferroelectric barrier. By flipping the polarization of the ferroelectric barrier it is possible to change an internal electronic potential profile and, hence, alter the transmission probability and produce the TER effect. Using this effect, reading of the polarization state can be performed in a non-destructive manner by measuring the resistance of the memory cell to a relatively low voltage. Since TER does not depend on the amount of the stored charge it allows a much better scalability. In addition to being highly relevant to technological applications, the TER effect concerns the fundamental issues of the critical behavior and switching dynamics in ultrathin ferroelectric films, role of structural defects and interfacial properties in the transport behavior. Maintaining a stable polarization in ultrathin ferroelectric films is essential for exploiting the functionality of these materials in nonvolatile memory applications.
This talk will focus on investigation of the polarization-controlled tunneling conductance in the FTJ devices that incorporate both ferroelectric films and 2D transition metal dichalcogenides (TMD). In addition, the in-plane transport of the TMD conducting channel in the ferroelectric field effect transistor (FE-FET) devices modulated by polarization reversal will be discussed. We show that interface engineering in these hybrid TMD-FE systems provides a possibility of successfully addressing the most serious challenges relevant to ferroelectric device performance, such as ON/OFF ratio, lifetime, operation endurance and reliability.
A Thermal Method to Reduce the Polysilicon Resistance for Deep Submicron Integration Process
Authors: Li Xiang , Liu Shi Xiang , Liu Xu Li , Foong Mun Loong , Ye Wei qiang 
Published: February 2020

In the ultra-large-scale integration (ULSI) technologies, polysilicon resistors are usually employed in the integrated circuits as a precise analog resistor element for a variety of applications, such as DAC (digital resistor give the solution of the linearity and Rs concerns to analog converter) in analogue circuits [1-3]. Conventionally the polysilicon resistance can be adjusted by ion implantation and post annealing process [4]. For the self-aligned implantation process, the dosage changes which are always utilized to adjust the resistance are feasible to induce the MOS characteristics changes, especially in the submicron process whose short-channel effects (SCE) are much more sensitive to the dosages [5]. In this work, we propose a new inner anneal process in N2ambient after polysilicon re-oxidation to reduce the polysilicon resistance by changing the polysilicon grain size.
The test patterns are manufactured on 300mm-diameter wafer by 65-nm 1-poly 7-metal standard CMOS technology. After polysilicon re-oxidation to form oxide film on polysilicon surface, the wafers are annealed at 800oC, 900oC, 950oC and 1000oC in N2ambient, respectively. Fig. 1 shows the process flow and annealing process steps in the flow. After anneal, the polysilicon grain size is measured by X-ray powder diffraction (XRD). And the electric characteristics for NMOS, PMOS and polysilicon resistance are tested.
Fig. 2 shows the poly resistance reduction proportion and poly grain size after anneal at 800oC, 900oC, and 1000oC for 5min, and 950oC for 20min in N2 ambient, respectively. Only after annealing at 950oC or above for 5min, the resistance can be obviously reduced, due to the poly grain size increasing. Fig. 3 shows threshold voltages (Vt) variation proportions of NMOS and PMOS owning gate length of 65nm and width 0.12µm after utilizing annealing process at different temperatures. PMOS is more sensitive to the anneal process than NMOS. But after anneal at 950oC or below, the threshold variation for both NMOS and PMOS is less than 5%, which is acceptable for the integration process manufacturing.
A new anneal process at N2 ambient to adjust the polysilicon resistance has been proposed. It has been verified that utilizing anneal process at 950oC or below, the 65nm MOS performances can be maintained almost same as before. Consequently, it is considered that the anneal method can be to be applied to the deep submicron integration process.

References

[1] C. D. Parikh, and R. M. Patrikar, Solid-state Electronics, 43, 683 (1999).
[2] R. Murii, and M. J. Deen,, IEEE Trans. Electron Devices, 49, 187 (2002).
[3] C. Uang, H. Chuang, S. Tsai, K. Thei, P. Lai, S. Fu, Y. Tsai, W. Liu, IWJT, 293 (2004).
[4] S. Gupta, J. Electrochem. Soc. 149, G271 (2002).
[5] R. H. Dennard, F. J. Gasensslen, H. M. Yu, V. L. Rideout, E. Bassous, A. R. Leblanc, Solid-state Circuits Soc Mag. IEEE, 87, 668 (1999).

Figure 1
(Invited) Semiconductor Nanowires for Optoelectronics and Energy Applications
Authors: Jagadish Chennupati 
Published: February 2020

Semiconductors have played an important role in the development of information and communications technology, solar cells, solid state lighting. Nanowires are considered as building blocks for the next generation electronics and optoelectronics. In this talk, I will introduce the importance of nanowires and their potential applications and discuss about how these nanowires can be synthesized and how the shape, size and composition of the nanowires influence their structural and optical properties. I will present results on axial and radial heterostructures and how one can engineer the optical properties to obtain high performance optoelectronic devices such as lasers, THz detectors, solar cells. Future prospects of the semiconductor nanowires will be discussed.
Luminescence of Eu3+ in a Mullite-Type Host Material Bi2Ga2Al2O9
Authors: Tiwari Hansnath , Varadaraju U V 
Published: February 2020

The escalating energy demand coupled with limited conventional energy resources led to a widening gap between supply and demand, making it inevitable to look for novel energy efficient technologies. Solid state lighting is one of the promising areas where a significant amount of energy consumed can be conserved without compromising on the sophistications of conventional lighting. Solid state lighting kindled the interest of researchers owing to their impressive energy efficiency, longer life time, greater reliability, eco-friendly nature and the reasonable ease of fabricating the white light emitting diodes (WLEDs). Typically blue light emitting chip in combination with yellow light emitting phosphor1, Y3Al5O12:Ce3+ (YAG:Ce3+) have been used to produce the white light. However, the obtained white light has poor light quality and low color rendering index (CRI >80), due to lack of red component in the obtained white light spectrum. Tricolor phosphors (red, green and blue) in combination with near ultra violet (NUV) emitting source (InGaN chip) were considered to be an alternative to get better lighting properties and the generated white light by this technique has similarity to sun light and a good CRI value2
,
3. The commercially used red phosphor Y2O2S:Eu3+ is sensitive towards moisture and decomposed under high temperature which is harmful to the environment. Nitrides, CaAlSiN3:Eu2+ can be used as a substitute but its preparation needs greater care and highly controlled preparation conditions. Therefore, the red phosphors with thermal, chemical stability and high luminous intensity became an essential need for lighting industries.
Recently, mullite and mullite-type ceramics have attracted attention because of their interesting optical properties4, high thermal and chemical stability5. In this context, we report Eu3+ activated mullite-type Bi(1-x)2Ga2Al2O9:xEu3+ (x = 0.00, 0.025, 0.05, 0.10, 0.20 and 0.30) solid solution which were prepared by simple solid state method. The prepared samples were characterized by x-ray diffraction and luminescence properties were measured under near UV and blue light excitation. The europium dopped Bi2Ga2Al2O9 (BGAO) showed characteristic excitation peaks between 250 nm and 500 nm. The chromaticity coordinates (0.61, 0.37) calculated under blue light excitation for 20% Eu3+ doped BGAO, located in orange-red region of chromaticity graph. The coordinates were close to the reference red phosphors and the results indicate that it have potential application in the field of lighting and displays under blue LED excitation.
References:
1. S. Nakamura, MRS Bull., 22, 29–35 (1997).
2. J. S. Kim et al., Appl. Phys. Lett., 85, 3696–3698 (2004).
3. C. K. Chang and T. M. Chen, Appl. Phys. Lett., 91, 081902 (2007).
4. G. Blasse and O. B. Ho, J. Lumin., 21, 165–168 (1980).
5. M. M. Murshed and T. M. Gesing, Mater. Res. Bull., 48, 3284–3291 (2013).

Figure 1
Recent Advances on the Optical Properties of Zinc-Doped Antimony Sulphide (Sb2S3) Thin Films
Authors: Nwofe Patrick AKATA , Ozibo Cyril Ozibo , Agbo Peter Ekuma 
Published: February 2020

The influence of zinc (Zn) impurities at different concentrations on the properties of antimony sulphide (Sb2S3) thin films grown using the solution growth technique is reported. The films were grown at room temperature of 28oC, a deposition time of 2 h, and an initial pH of 4.40. The films were then doped with different concentrations of Zinc impurities (0.25 -1.0M) and then annealed at annealing temperatures ≤ 400 oC. The films were characterised using optical spectroscopy and Fourier transform infrared spectroscopy (FTIR) to investigate the transmittance, absorbance and reflectance versus wavelength measurements, X-ray diffractometry (XRD) to study the structural properties, Scanning electron microscopy (SEM) to investigate the morphological properties, and Rutherford Backscattering (RBS) techniques for the compositional analysis. The results indicate that the film thickness was in the range 0.3 -1.5μm, with an increase in the film thicknesses of the doped layers compared to the as-deposited films. The transmittances of the doped layers were found to be reduced compared to the as-deposited films. The results of the optical analysis show that the films had direct energy band gap with optical absorption coefficient (α) > 104 cm-1 in both the doped and as-grown layers. The refractive index was typically ≤ 3.6, with higher values obtained from the doped layers. The values of the energy band gap were in the range suitable for application in solar photovoltaic and photonic devices.
Top Seeded Solution Growth of 4H-SiC Bulk Crystal Using Graphite Block for Long-Term Growth
Authors: Ha Minh-Tan , Byeon Dae-Seop , Yoon Ji-Young , Lee Myung-Hyun , Seo Won Seon , Lee Won-Jae , Kim Cheol-Jin , Jeong Seong Min 
Published: February 2020

Solution growth method of SiC is assumed to be a promising technique to grow high quality SiC bulk crystal. Solution growth of SiC are based on the liquid phase growth from an incongruent melt composed of Si and C. Among various solution growth techniques, top seeded solution growth (TSSG) method for SiC has been widely studied for a next generation SiC growing technique. In TSSG method, the crystal growth on seed crystals is accomplished by the precipitation of solid SiC from C dissolved a Si melt on a seed crystal located at the top of the liquid. Because of the low solubility of C in liquid Si, SiC crystal growth on seed crystals using TSSG involves the use of a Si-rich Si-C solution. Therefore, in the TSSG method, high C solubility is required to increase the growth rate of SiC. Hence, there have been lots of studies how to increase the C solubility of Si melt. Eventually, several metallic solvents were proved to enhance the carbon solubility, so that the growth rate of SiC using TSSG were remarkably increased up to 2 mm/h. So, it is very optimistic to increase the thickness of grown crystal.
However, TSSG has critical issue to increase crystal thickness because the C is supplied from the graphite crucible which is also the reservoir of Si melt. As growing time goes, therefore, the crucible will be dissolved to Si melt and the dissolved carbon will be consumed to grow single crystalline SiC crystal. Eventually, the thickness of SiC grown layer will be limited the volume size of graphite crucible. The reduction of graphite crucible will bring about the change of temperature distribution in the solid and liquid inside the reactor. Mechanical failure during crystal growth could be happened.
Therefore, in this study, we applied a graphite block inside graphite crucible for elongate the growing time limit using graphite crucible for TSSG. Several graphite blocks with different design and materials properties were evaluated using finite element analysis using COMSOL multiphysics. The simulated results were then applied to the real experimental growth using small seed samples. Finally, the durability of graphite crucible and the crystal quality were comparatively evaluated with and without graphite blocks using several characterizations techniques.
Optical and Electric Properties of Cu-Doped ZnO Films Grown on MgO (100) Substrate
Authors: Ho Ming-Yuan , Wen Meng Chieh , Chang Liuwen , Chou Mitch 
Published: February 2020

This work studied the luminescent and electric properties of Cu-doped ZnO films grown on MgO (100) substrate by plasma-assisted molecular beam epitaxy. The doping quantity was controlled by regulating Cu Kundsen cell temperature. The crystallinity and surface morphology of the Cu-doped ZnO films were characterized by high resolution X-ray diffraction, atomic force microscopy, and scanning electron microscopy. The chemical state and elemental compositions was analyzed by X-ray photoelectron spectroscopy (XPS). The near-band-edge emission (NBE) and defect-related emission (DLE) were analyzed by photoluminescence spectroscopy. The electric properties were determined by Hall measurement and four-point probe measurement.
The experimental results revealed that ZnO films grown epitaxially on MgO substrate with (10-10)ZnO//(100)MgO. X-ray rocking curve measurements showed that the (10-10)ZnO reflection exhibits a full width at half maximum value of about 0.7o-1.0o. The XPS analysis showed that the doped copper atoms have a monovalent state in the ZnO films grown at Cu Kundsen cell temperatures lower than 900oC. The amount of Cu incorporation was estimated to be in the range of 1x1019 to 1x1021 atoms/cm3. The NBE peak of the Cu-doped ZnO films can be deconvoluted into three sub-peaks: a free exciton emission at 3.29 eV, a basal-plane stacking fault emission at 3.19 eV, and a third peak at 3.25 eV. The third peak might be related to an acceptor-bound excitons due to the doping of copper, since it disappeared after annealing. Hall measurement indicated that both pure and Cu-doped ZnO films are n-type semiconductor. The electron concentration of undoped ZnO film is 1x1018 cm-3, whereas that of the Cu-doped ZnO films are in the range of 5x1015~5x1016 cm-3. Obviously, the electron concentration of ZnO is compensated by the substitution of Cu+ to Zn2+ which generates acceptor levels. However, the electron concentration of the Cu-doped ZnO films rose back to the order of magnitudes 1018 cm-3 after annealed in oxygen or hygrogen, indicating the acceptor states were eliminated. Moreover, in this study, the incorporation of copper in ZnO does not result in an increase of the yellow-green luminescence.
Thermal-Structural Optimization of Light with LED Packaging
Authors: Zhang Liqiang , Li Yongli , Ge Daohan , Zhu X.D. 
Published: February 2020

At present, the light-emitting-diode (LED) has been a tremendous surge in its application as a new type of generation lighting source. The thermal performance and structural reliability of LED system have been investigated by different conditions in electronic package [1]. With the minimization of the LED packaging, the reliability problem, especially, the thermal reliability becomes more and more seriously. Hence the heat dissipation for LED system becomes much crucial. Lots of heat management methods have been investigated for LED system designing and manufacturing. The most popular cooling method used in the LED system is the passive cooling, however, its cooling efficiency is very low. It is very significant to develop the heat dissipation method [2, 3].
A systematic numerical and experimental method is developed to optimize a caution lamp with multichips LEDs in this paper. Here we intend to describe the thermal performance of LED caution lamp with multiple LED chips through the structural optimization by the finite element method. And to understand the thermal characteristics of the caution lamp with difference structural parameters. After the optimization, one type of caution lamp was made and the highest temperatures of LED chips have been test. This optimization method is useful for design and manufacturing of caution lamps with multiple LED chips.
After numerical simulation, we prepared the caution lamp sample with six LED chips according to the results. The Thermalcouples are used to test the temperature of the lamp. Compared with the simulation and the experiment data, the high temperature of LEDs were reduced by choosing fitting parameters. It indicates that the results and methods used in this paper can provide the guidance in the understanding of thermal management for LED lamps design.
Figure 1 show temperature distribution of light structures before and after thermal-structural optimization.
Figure 2 show the test principle connection and test system.

Figure 1