bluuebunny/crossref_metadata_2025_split huggingface dataset:
(Invited) SiGe BiCMOS Heterogeneous Integration Using Wafer Bonding Technologies
Authors: Wietstruck Matthias , Kaynak Mehmet , Mai Andreas 
Published: February 2020

Heterogeneous integration has been a very attractive research topic for the last decades. Due to the limitations for further device scaling the More-than-Moore approach based on heterogeneous integration has been pointed out as the key integration path for future smart system integration [1]. Temporary and permanent wafer bonding technologies are one of the key enabling technologies for heterogeneous integration. Temporary wafer bonding is a well-established bonding technique to provide a stable handling and fabrication of ultra-thin silicon wafers. Permanent wafer bonding with various electrical isolating or conductive bonding interfaces is applied for wafer-level heterogeneous device integration [2]. Making available both temporary and permanent wafer bonding technologies together with a high performance SiGe BiCMOS technology will pave the way for new applications like millimeter-wave packaging, 3D-integration and smart sensors to realize multi-functional and miniaturized systems.
The potential of temporary and permanent wafer bonding techniques for heterogeneous integration of a high performance SiGe BiCMOS technology with additional devices and technology modules will be presented by three different application examples namely BiCMOS embedded Through-Silicon Vias (TSV), silicon interposer including substrate-integrated waveguides and BiCMOS embedded microfluidics. With respect to the different applications the potential and the main technology obstacles for SiGe BiCMOS temporary and permanent wafer bonding will be highlighted. While the temporary wafer bonding process with subsequent wafer thinning and thin wafer backside fabrication is mainly limited by the robustness of adhesives against high temperature and high vacuum process conditions, the permanent wafer bonding based on SiO2-SiO2 fusion bonding is mainly limited by the demanding surface requirements in terms of roughness and wafer bow which has been optimized to fulfill the requirements. By optimizing the SiGe BiCMOS technology both temporary and permanent wafer bonding together with subsequent semiconductor fabrication becomes feasible.
In summary, the development of wafer bonding application together with an industrial-level BiCMOS process will be presented. By the use of temporary and permanent wafer bonding new applications in the area of heterogeneous integration becomes feasible making SiGe BiCMOS technologies more attractive for future smart system applications.
(Invited) Molten Semiconductors for High Temperature Thermoelectricity
Authors: Zhao Youyang , Rinzler Charles Cooper , Allanore Antoine 
Published: February 2020

High temperature (>900°C) industrial waste heat recovery remains at the frontier in thermoelectric materials. The high temperature (greater than 1200°C), low heat-flux, and large surface area encountered in high temperature industrial reactors imply that materials cost dictates deployment. Molten semiconductors are one cost-effective material option that remains understudied. Here we report the performance of a laboratory-scale device based on molten SnS, in particular the Figure of Merit (ZT) and the conversion efficiency of this first generation of material. Furthermore, a discussion of the Seebeck and transport properties of molten SnS is proposed [1]. It is found that electronic properties of molten semiconductors are promising, and that the remaining question lies in the thermal transport properties. Recent experimental results show that thermal transport in molten SnS involves drastically different mechanisms than in the solid-state , and it calls for advances in the prediction and evaluation of physical properties of molten materials. The results with SnS highlight the materials and engineering challenges that will allow the next generation of molten semiconductors to be developed.
[1] Youyang Zhao, Charles Rinzler, and Antoine Allanore, Molten Semiconductors for High Temperature Thermoelectricity, ECS J. Solid State Sci. Technol. 2017 6(3): N3010-N3016; doi:10.1149/2.0031703jss
(Invited) Template Assisted Electrochemical Deposition and High Power Factor Materials for Integrated Thermoelectric Devices
Authors: Schierning Gabi , Li Guodong , Barati Vida , Lara Ramos David Alberto , Sieger Tom , Garcia Javier , Perez Rodriguez Nicolas , Mohn Melanie , Schlörb Heike , Freudenberger Jens , Reith Heiko , Nielsch Kornelius 
Published: February 2020

Next generation integrated micro-scale thermoelectric devices are envisioned for spot cooling of active electronic parts or as independent power supply units to exploit small hot spots within electronic circuits. In the first case, a thermoelectric cooler is added to manage the temperature stability of sensitive electronic or photonic devices, hence to remove high density heat fluxes from these critical parts. In the second case, a thermoelectric generator is intended to recover a proportion of waste heat of a hot spot, i.e. a small, but otherwise unlimited heat source, in the electronic circuits. Both cases are technologically challenging since they request for a fabrication route that is compatible with a CMOS back-end processing. But especially the latter application provides also novel requirements to the thermoelectric material. The typical paradigm of thermoelectric material's development aims towards low thermal conductivity. This is not necessarily helpful for the given example of application where the heat has to be efficiently removed from the active electronic part, utilizing a proportion of this heat for thermoelectric power generation. Hence, this paradigm has to shift towards the development of high power factor materials, rather than low thermal conductivity materials.
A processing that, at least in principle, can be fully compatible with CMOS back-end technology is given by the combination of lithographic structuring and the electrochemical deposition of the functional thick films into pre-structured cavities. A material class that provides both, high power factors and sufficiently high thermal conductivity for the removal of waste heat, is given by metallic alloys. This paper will therefore provide experimental details of the processing technology of integrated micro-scale thermoelectric devices and a discussion of high power factor materials for thermoelectric devices.
(Invited) IV-VI Monochalcogenide Nanostructures: Synthesis, Doping and Thermoelectric Properties
Authors: Gao Xuan 
Published: February 2020

Recently IV-VI monochalcogenide SnSe or SnS has been proposed as a promising two-dimensional (2D) material for valleytronics and thermoelectrics. Despite much theoretical interest and many experimental reports on the thermoelectric characterizations of SnSe single crystals, experimental studies on SnSe and SnS in the nanostructured form are still limited. We report the synthesis of SnSe nanoflakes and thin films with chemical vapor deposition (CVD) and their thermoelectric properties. As grown SnSe nanostructures are found to be intrinsically p-type and different types of dopants (In, Pb and Ag) were explored to control the carrier density. We will present the electrical transport property of SnSe nanoflake field effect transistor devices and the effects of doping on the electrical conductivity, Seebeck coefficient, power factor and anisotropy in SnSe films. By doping, the power factor of SnSe films can be improved by at least one order of magnitude compared to the "intrinsic" as grown materials. If time permits, we will also discuss the transport properties of SnS nanoflakes obtained by mechanical exfoliation to compare with the chemically grown SnSe nanostructures. Our work provides an initial step in the pursuit of IV-VI monochalcogenide nanostructures as novel 2D semiconductors for electronics and thermoelectrics.
(Invited) Formation of Conducting Filaments in TaOx-Based Resistive Switching Devices
Authors: Ma Yuanzhi , Herzing Andrew , Li Dasheng , Nuhfer Noel T. , Bain James A. , Skowronski Marek 
Published: February 2020

Resistive switching phenomenon and resistive switching devices could form the basis for the next generation non-volatile solid state memories. Particularly promising are structures based on dielectric oxides such as TaOx and HfOx which have been demonstrated to large OFF/ON ratio, low energy dissipation per switching cycle, long endurance, and sub-nanosecond switching times. It is widely accepted that the first switching cycle, referred to as electroforming, results in formation of a conducting small diameter filament within the highly resistive matrix. This is due to the electric field which induces the transfer of oxygen ions across the interfaces and into the metal electrodes producing locally oxygen-deficient conducting oxide. Most of the structural changes induced during electroforming and switching have been reported in devices that experienced high current levels during switching cycle.
The devices used in this study were 500×500 nm2 crossbar structures with 20 nm thick TiN electrodes and 100 nm of reactively sputtered amorphous TaOx. The devices were electroformed and electroformed/switched with the current compliance of 10-20 μA. The data have been gathered in several imaging modes of electron microscopy including bright field, High Angle Annular Dark Field (HAADF), Energy Dispersive X-ray Spectroscopy, and low loss and core regions of Electron Energy Loss Spectroscopy (EELS). The entire volume of the functional layer remained amorphous with no signs of crystallization. It contained only one area of bright contrast in HAADF images corresponding to the conductive filament with the diameter of approximately 50 nm. The maps produced by all techniques clearly indicate an increase of [Ta]/[O] ratio within the filament. In addition to overall change of the composition, the core of the filament shows a fine structure of the composition on the scale of 5-10 nm. We interpret the changes in distribution as due to thermodiffusion in the temperature gradient induced by current constriction when the device enters the negative differential resistance region of its I-V. The temperature distribution during this process has been estimated using a self-consistent finite element model.
(Invited) Unconventional Computing with Memristors
Authors: Strukov Dmitri 
Published: February 2020

By now, there have been many demonstrations of resistive switching (“memristive”) devices based on organic, chalcogenide, transition metal-oxide and silicon materials and involving different physical switching mechanisms, such as phase-change transitions and modulation of the ionic concentration profiles by electrical and/or thermal forces. The conductance of some properly engineered memristors can be continuously tuned with relatively large electrical bias, and retained, effectively indefinitely, when small stress is applied. Such analog nonvolatile memory functionality combined with potentially very high device density, achieved by lateral scaling and/or monolithical vertical integration, enable many new exciting applications of memristors in neuromorphic and other types of computing.
In my talk, I will review several such applications based on metal-oxide memristors which were a recent focus of my group. I will start with stateful material implication logic, which was originally suggested by HPL group. In our work, we showed that 3D version of this logic allows resolving Feynman grand challenge of implementing 8-bit adder in a volume smaller than 50-nm cube. I will then review our experimental work on memristor-based security primitives, in which we utilized device variations and their nonlinear I-Vs to demonstrate functionality and physical performance superior to those of conventional approaches. Finally, I will discuss Race Logic, a novel computing paradigm in which information is encoded in timing of the signals, so that a particular problem is mapped to a circuit with controllable memristor-based delay elements, and the solution is provided by measuring the time for the injected signals to propagate via circuit. Due to direct encoding of the computation to the underlying physics, Race Logic is extremely energy efficient for a variety of problems, such as bioinformatics and neurocomputing. I will conclude my talk with a summary on the device/material challenges, and potential future work, specific to the discussed applications.
An Improved Li-Ion Battery Model to Study the Effect of Electrode Thickness
Authors: Xu Meng , Wang Xia 
Published: February 2020

Battery modeling and simulation are efficient tools for optimizing cell design parameters and aiding in material selection. Researchers studied how design parameters affect battery performance by conducting parametric studies using physics-based models. Meanwhile some internal parameters such as the lithium-ion concentration and the local electrical potential can also be predicted through the simulation, while it is near-impossible to measure these variables.
One challenge of battery model development is that many parameters necessary for the battery model are difficult to measure or quantify. For example, the effective diffusion coefficient of lithium ions within the cell is affected by the electrode thickness. This diffusion coefficient, however, was usually treated as a constant in previous work.
This work develops an improved physics-based battery model. The model is developed based on the principles of mass and charge conservation, as well as the electrochemical kinetics for an NCM111 half-cell. The model treats the lithium ion diffusion coefficient as a function of the electrode thickness. The relationship between the lithium ion diffusion coefficient and the electrode thickness is determined by fitting the model with the experimental data. Four half cells are fabricated and tested, and the positive electrode for each cell has a thickness of 46um, 64um, 73um, and 130um, respectively. The lithium diffusion coefficient is found to increase linearly with the electrode thickness. The model is validated at various discharge rates for the cells with different positive electrode thicknesses. It is found that, the utilization of the cell capacity decreases slowly with the increase of the electrode thickness at a low discharge rate. At high discharge rates, the cell with a thick electrode has much poorer rate capability than that with the thin electrode. The physics-based model proposed in the research can be extended to include more cell design parameters. Thus it allows for a better understanding of the influence of cell design parameters on battery performance, and will enable the engineer to more easily design a cell with optimal performance.
Improved Performance of Silicon Anodes Using Copper Nanoparticle Additive
Authors: Bachand Gabrielle , Chidambaram Dev 
Published: February 2020

Silicon continues to be an attractive anode material for use in lithium-based battery systems due to its high theoretical capacity and natural abundance. However, the widespread application of the silicon anode remains impeded due to notable, unfavorable characteristics observed during charge/discharge cycling. One such hindrance is the relatively poor electrical conductivity of silicon. Approaches to mitigating this issue often involve increasing the amount of conductive additive, but the additives are usually carbon-based or process-intensive. The focus of this research is the improvement of the electrical conductivity of the anode active layer by introducing nanoscale copper additive to the silicon structure. The fabrication of these anodes involved a simple, cost-effective procedure where the copper nanoparticle additive was homogeneously dispersed within the silicon active layer, and the anodes were tested using CR2032 type coin cells. The results of this research indicate excellent stability and improvements in the charge capacity of the cells with additive as a function of cycle testing. Surface characterization was performed using spectroscopy and imaging methods for comparison of anodes before and after charge/discharge cycling tests. SEM images show the successful integration of the copper nanoparticles within the silicon layer. Acknowledgement: This research was supported by the Office of Vice President for Research Innovation at the University of Nevada, Reno via an AIRE grant. Characterization of electrodes was conducted by Materials Characterization Nevada.
Graphene Coated Ni Foam As a Current Collector for N-Type Doped Si Thin Film Anode for Li-Ion Batteries
Authors: Zharbossyn Assem , Mukanova Aliya , Nurpeissova Arailym , Urazbayev Arshat , Kim Sung-Soo , Bakenov Zhumabay 
Published: February 2020

Thin film silicon (Si) has gained a significant attention as an anode material for Li-ion batteries (LIBs), since its nanostructure retains structural integrity through minimizing the volume variation. However, 2D Si thin film experiences delamination from the current collector, and loss of electrical contact leads to further capacity fading. To overcome this issue, recent scientific investigations have shown that the 3D structure of electrodes (porous, rough-surface, etc.) is capable of suppressing volume changes upon lithiation/delithiation and providing large contact area between active material and current collector.
Here, we propose a novel electrode material for LIBs that comprises of Si on graphene coated Ni foam (G-Ni). Porous Ni foam serves as 3D structured highly electroconductive network, and graphene layer was employed with the purpose of improving adhesion and electrochemical stability of Si thin film electrode. Magnetron sputtering was used to deposit n-type doped amorphous Si thin film on G-Ni. Chemical vapor deposition (CVD) was applied to obtain a few layer graphene (FLG) on catalytic Ni foam. The as-grown anode material was tested in a half-cell configuration with metallic lithium as a counter and reference electrode. The results were compared with n-type doped amorphous Si thin film on pristine Ni foam. Galvanostatic cycling performance was evaluated in the voltage range from 0.1 to 1.5 V at a current density of ~ 32 µA cm-2. Si-G-Ni anode exhibited the initial areal capacity of around 141 µA cm-2 and the stable reversible areal capacity of around 80 µA cm-2 over 100 cycles. Si-Ni anode shows an initial capacity of 91 µA/cm-2 with a rapid capacity fading to approximately 30 µA cm-2 at 100th cycle. The results of characterization and electrochemical tests will be presented at the conference.

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Modified Electrodes for Improved Performance of Redox Flow Batteries
Authors: Emmett Robert Keathley , Roberts Mark E. 
Published: February 2020

Redox Flow Batteries (RFBs) are an emerging electrochemical energy storage technology well-suited for intermittent energy sources, such as wind and solar. Integrated RFBs into grid-level energy systems would provide the storage necessary for alternative energy with only slight infrastructure changes. Currently, RFBs are limited by high material costs – from the use of precious metals – and/or low electrochemical activity. This work aims at improving power and energy of low-cost RFB electrolyte systems by doping carbon electrodes to facilitate Faradaic charge transfer at the interface, thereby decreasing costs and increasing accessibility of RFB systems. Carbon electrodes are modified with redox mediators to decrease the voltage drop and to increase charge transfer. Simulated half-cell experiments are conducted using carbon modified electrodes soaked with redox electrolytes s that are separated from pure base electrolytes by alkaline modified Nafion. Full cell testing is performed with modified Nafion separating the catholyte (0.7M Fe(CN)6 •3H2O and 1M NaOH) and the anolyte (0.35M Fe2SO4, 0.4M NaCl, Triethanolamine, and 3M NaOH). These electrolytes provide a test bed for evaluating all Iron RFBs as a cheaper alternative to Vanadium, therefore decreasing raw material cost and environmental impact.
Incorporating redox mediators into carbon electrodes improves kinetics elevating voltage efficiency and allowing higher current densities without ebbing discharge voltage. Power is modeled with current and voltage by Ohm’s Law (P=IE). Electrolytes with low inherit voltage efficiency display increased energy density due to fully capturing the redox behavior at raised current densities. Our alkaline discharge voltage difference has a maximum of 1.5 V with our modified electrodes. These electrodes showed a ~10x increase in power with catholyte half-cell testing (305 to 32W/Kg) and a ~4x increase in power with the anolyte (990 to 227Wh/Kg). Energy density improvements were observed for the catholyte (232%) and the anolyte (41%), lowering the volume of electrolyte needed. Long term stability experimentation revealed consistent, coulombic and voltage efficiencies for 1400 cycles (~4 years of daily use). These adaptations to RFB electrodes could also be applied to current RFBs to increase their performance, thereby decreasing material costs and improving cheaper alternatives.

Figure 1
Novel Electrode Materials By Modification Route of Negative Thermal Expansion Materials
Authors: Liu Junnan , Schulz Bernd , Sharma Neeraj 
Published: February 2020

Until now and most likely for the next few decades, lithium-ion batteries (LIBs) are likely to remain as one of the best energy storage devices. However, the price of lithium metal is increasing dramatically and some safety issues have been reported, which leads research towards alternative battery chemistries like sodium-ion and potassium-ion batteries to potentially alleviate some of these issues. Unfortunately, due to the larger size of sodium and potassium ions compared with lithium ion, they typically require electrode materials with larger voids to allow reversible insertion. In this project, we illustrate how some negative thermal expansion (NTE) materials fit these requirements and thus may be a candidate electrode for next-generation batteries. At the same time, we find that cation insertion into the voids changes the properties of the NTE materials. Modified NTE materials that tend towards zero thermal expansion (ZTE) materials could have significant advantages in use for industrial applications, for example, in fibre optic systems and as packaging materials for refractive index gratings or in high-value engineering industries. So in this research, we have investigated a new electrode material for next-generation batteries and manipulated their properties for applications in other fields.
Here we present the results on Sc2-xAlxW3-yMoyO12 as electrodes in Li, Na and K-ion batteries and the change in properties post ion-insertion.