bluuebunny/crossref_metadata_2025 huggingface dataset:
Band-Diagram Framework for Materials Development in Cation Intercalation Charge Storage
Authors: Holder Aaron M. , Young Matthias , George Steven M. , Musgrave Charles
Published: February 2020

The next generation of batteries may employ ionic liquid or solid electrolytes with stability windows of more than 6 volts, and migrate from lithium ion chemistries to more earth-abundant cations such as sodium, potassium, or magnesium ions. In this work, we apply new theoretical and experimental approaches to lithium ion battery cathode materials to gain insight into the requisite properties for electrode materials in next-generation batteries, with particular emphasis on spinel lithium manganese oxide (LiMn2O4). Nanoscale spinel LiMn2O4 is of interest as a high-rate cathode material for advanced battery technologies among other electrochemical applications. We first demonstrate the synthesis of ultrathin films of spinel LiMn2O4 between 20 and 200 nm in thickness by room-temperature electrochemical conversion of MnO grown by atomic layer deposition (ALD). Next, we investigate the charge storage properties of LiMn2O4 thin films in electrolytes containing Li+ with Na+, K+, and Mg2+. Using a coupled electrochemical and band structure analysis of LiMn2O4 informed by screened hybrid density functional theory calculations we identify new features of the charge storage properties and stability of LiMn2O4. The accuracy and predictive power of this theoretical framework to determine the equilibrium potential(s) for charge-transfer in intercalated compounds is validated by comparison with experimental results. Furthermore, our CV experiments demonstrate that for sweep rates between 1 and 400 mV/s, up to 30% of the capacity of LiMn2O4 arises from bulk electronic charge-switching which does not require compensating cation mass transport. The hybrid ALD-electrochemical synthesis, coupled electrochemical and electronic structure analysis, and unique charge storage mechanism we describe provide a fundamental framework to guide the development of future nanoscale electrode materials for ion-incorporation charge storage.

Figure 1
Environmentally-Friendly Aqueous Li (or Na)-Ion Battery with Fast Electrode Kinetics and Super-Long Life
Authors: Dong Xiao-Li , Chen Long , Wang Yong-Gang , Xia Yong-Yao
Published: February 2020

Current rechargeable batteries generally display limited cycle life and slow electrode kinetics and contain environmentally unfriendly components. Furthermore, their operation depends on the redox reactions of metal elements. We present an original battery system that depends on the redox of I−/I3
− couple in liquid cathode and the reversible enolization in polyimide anode, accompanied by Li+ (or Na+) diffusion between cathode and anode through a Li+/Na+ exchange polymer membrane. There are no metal element–based redox reactions in this battery, and Li+ (or Na+) is only used for charge transfer. Moreover, the components (electrolyte/electrode) of this system are environment-friendly. Both electrodes are demonstrated to have very fast kinetics, which gives the battery a supercapacitor-like high power. It can even be cycled 50,000 times when operated within the electrochemical window of 0 to 1.6 V. Such a system might shed light on the design of high-safety and low-cost batteries for grid-scale energy storage.

References

G. L. Soloveichik, Electrochemistry: Metal-free energy storage. Nature
505, 163–165(2014).

X. Dong, L. Chen, J. Liu, S. Haller, Y. Wang, Y. Xia, Environmentally-friendly aqueous Li (or Na)-ion battery with fast electrode kinetics and super-long life. Sci. Adv.
2, e1501038 (2016).

Figure 1
Realizing 200mAh g-1 Lithium Manganese Oxide Spinel in Lithium Ion Battery with Prelithiated Anode
Authors: Noh Hyun Kuk , Jeon Yu Ju , Song Hyun-Kon
Published: February 2020

At present, the global market size of Li ion battery is dramatically increasing as its application in large scale system such as electric vehicle (EV) and energy storage system (ESS) expands intensely. Accordingly, the development of high-energy-density battery for their application is urgently needed. Today, energy density of Li ion battery largely depends on the specific capacity of cathode active material. The specific practical capacity of conventional cathode active materials such as LMO (Lithium Manganese Oxide Spinel, 4V region), LNMC (Lithium Nickel Manganese Cobalt Layered Oxide), and LFP (Lithium Iron Phosphate Olivine) is 100-170 mAh/g and the utilization of cathode active materials of even higher specific capacity is essential for the development of high-energy-density battery.

Cathode active materials such as sulfur, oxygen, LMO (3+4V region) have theoretically very high specific capacity (270 – 3800 mAh/g), however, cannot be adopted in today’s Li ion battery industry because in their structure they do not possess lithium which is vital for electrochemical reaction in Li ion battery. To utilize these non-lithiated cathode active materials, additional lithium must be provided to the cell. Li half-cell where Li-foil is used as the anode in the cell could be a candidate, however, the Li dendrite growth problem which might lead to battery explosion should be precedently solved for practical application. More desirable and rather easily applicable solution is the prelithiation strategy in which anode or cathode is chemically lithiated (via lithium intercalation or alloying) by short-circuit reaction between the electrode and lithium source such as lithium foil, gas or powder. The prelithiation of anode is preferred because the cathode prelithiation might yield safety problem with excessive generation of heat of reaction.

In this study, we propose an elegant prelithiation mechanism in graphite anode based on the results of electrochemical reaction and physico-chemical analyses. We demonstrate the prelithiation methodology that is directly applicable in practice with high prelithiation yield (efficiency) by controlling the relevant important variables. We also show that the developed prelithiation methodology can be applied for designing and operating full cell battery in which non- (or partially) lithiated LMO is adopted as cathode active material, which delivers ~200 mAh/g in 3+4V region with good cycle capability.
New Lithium-Excess High-Capacity Positive Electrode Materials with Mo3+/Mo6+ three-Electron Redox
Authors: Hoshino Satoshi , Ichikawa Shinnosuke , Ozaki Tetsuya , Inamasu Tokuo , Yabuuchi Naoaki
Published: February 2020

The demand for the increase in energy density of lithium batteries are steadily growing. The use of three-electron redox of transition metals is expected to be a plausible strategy to further increase the energy density of positive electrode materials with less transition metal ions. Historically, three-electron redox reaction of transition metals is reported only for Cr3+/Cr6+, e.g., Li1.2Cr0.4Mn0.4O2.[1] In this study, the reaction of Mo3+/Mo6+ is targeted as electrode materials. Since conventional layered system, LiMo3+O2, has one mole of Li in the formula unit, only one-electron redox of Mo3+/Mo4+ is used. Therefore, Mo3+ is diluted in lithium-excess oxide, Li3NbO4 [2] as the model material, according to the chemical formula of x LiMoO2 – (1 – x) Li3NbO4 binary system. The highest reversible capacity based on Mo3+/Mo6+ is expected with x = 0.6 (Li9/7Nb2/7Mo3/7O2) in this binary system.

Our trials to synthesize Li9/7Nb2/7Mo3/7O2 were, however, failed by conventional solid-state reaction. Mixtures of LiMoO2 and Li3NbO4 were obtained regardless of different synthesis conditions. Therefore, Li9/7Nb2/7Mo3/7O2 was prepared by mechanochemical route from LiMoO2 and Li3NbO4 as precursors. A mixture of LiMoO2 and Li3NbO4 was mechanically ball-milled at room temperature with a ZrO2 container and balls. XRD patterns of LiMoO2, Li3NbO4, and Li9/7Nb2/7Mo3/7O2 prepared by ball-milling are compared in Figure 1a. An X-ray diffraction pattern of Li9/7Nb2/7Mo3/7O2 is assigned to a cation disordered rocksalt structure with low crystallinity. Electrochemical properties of Li9/7Nb2/7Mo3/7O2 before and after mechanical-milling were examined in Li cells as shown in Figure 1b. The sample before mechanical-milling shows initial discharge capacity of ca. 80 mAh g-1, and a voltage profile is the same with LiMoO2. On the other hand, the sample after mechanical-milling delivers a reversible capacity of ca. 290 mAh g-1, which nearly corresponds to that of theoretical capacity based on the redox reaction of Mo3+/Mo6+. Moreover, three-electron redox of Mo is supported by X-ray absorption spectroscopy without the contribution of Nb for charge compensation.

From these results, we will discuss the possibility of a new series of high-capacity positive electrode materials with three-electron redox of Mo3+/Mo6+ for rechargeable lithium batteries.

 

References

[1] B. Ammundsen et al., Journal of The Electrochemical Society, 149, A431 (2002).

[2] N Yabuuchi et al., Proceedings of the National Academy of Sciences, 112, 7650 (2015).

 

Figures

Figure 1
Integrated Layered YLi2MnO3-(1-y)LiNi1/2Mn1/2O2 Materials Applied to Lithium-Ion Batteries
Authors: Abdel-Ghany Ashraf , Mauger Alain , Groult Henri , Zaghib Karim , Julien Christian M
Published: February 2020

This paper presents recent progress in Li-ion batteries with the active sub-micron sized particles of the positive electrode chosen in the family of lamellar compounds LiMO2 where M stands for a mixture of Ni, Mn elements, and in the family of yLi2MnO3•(1-y)LiNi½Mn½O2 layered-layered integrated materials. The structural, physical and chemical properties of these cathode elements are reported and discussed as a function of all the synthesis parameters that include the choice of the precursors and of the chelating agent, and as a function of the relative concentrations of the M elements and composition y. Their electrochemical properties are also reported and discussed, to determine the optimum compositions in order to obtain the best electrochemical performance while maintaining the structural integrity of the electrode lattice during cycling.
Li3V2(PO4)3 Particles Anchored in Carbon Nanofiber As a Cathode Material for High-Power Lithium Rechargeable Battery
Authors: Shin Jeongyim , Yang Junghoon , Kang Yong-Mook
Published: February 2020

Lithium rechargeable battery has been rapidly developed for the applications in portable devices, electric vehicles (EV), and hybrid electric vehicles (HEV) due to their high energy density and durable cycle life. From the viewpoint of electrode, fast lithium ion and electron transport are essential to enhance its electrochemical performance. However, it is quite challenging to improve both properties at the same time, especially for cathode materials. Thus, no matter what we develop for new cathode materials, there have been severe limitations in terms of lithium ion diffusivity and electronic conductivity.

Phosphate (PO4)3--based materials have been attracting tremendous interests due to their competitive energy density and remarkable thermal stability. Among these phosphates, monoclinic Li3V2(PO4)3 (LVP) was proposed as a highly promising cathode material, owing to its high operating voltage and very high theoretical capacity of 197 mAh g-1 when all three lithium ions are extracted/inserted between 3.0 and 4.8 V. In particular, its three-dimensional structure framework consisting of slightly distorted VO6 octahedral and PO4 tetrahedral sharing oxygen vertex provides large interstitial space that makes lithium ions capable of moving fast inside the structure. However, just like the other metal phosphates, it shows a limited electron conductivity (10-8 - 10-9 S cm-1), which makes LVP to be difficult for practical applications.

Herein, we present a sagacious design of LVP/carbon nanofiber with a distinctive morphology where LVP nanoparticles are anchored in the surface of carbon nanofiber. In general carbon-coated LVP 1D materials, there has been a problem that the carbon coating layer additionally interferes with lithium ion diffusion into LVP bulk. However, in our structure, LVP particles can directly contact with electrolytes leading to an improved lithium ion conductivity. Furthermore, carbon nanofiber can provide fast electron transport along its 1D pathway. As a result, it was demonstrated that this unique structure is favorable for simultaneously maximizing Li ion conductivity and electronic conductivity for great electrochemical improvement of LVP materials.

Figure 1
Electrochemical Performance of Ti- and Zr-Doped LiCoO2 Film Cathodes Prepared By Rf-Magnetron Sputtering for Lithium Microbatteries
Authors: Sivajee-Ganesh Kapu , Purusottam-Reddy Bommireddy , Hussain Obili M , Mauger Alain , Zaghib Karim , Julien Christian M
Published: February 2020

In an attempt to enhance the microstructural and electrochemical (EC) properties, LiCoO2 thin films were doped with titanium or zirconium. RF magnetron sputtering technique has been employed for the deposition of films on Au/Ti/SiO2/Si substrates from lithium-rich LiCoO2 target with mosaic configuration. The as-deposited and Ti- and Zr-doped LiCoO2 thin films at lower doping concentration exhibited the α-NaFeO2 structure with R-3
m symmetry as confirm from X-ray diffraction and Raman studies. The cyclic voltammogram of micro-electrodes in aqueous electrolyte exhibited perfect redox peaks with good reversibility. The chronopotentiometry studies revealed that the discharge capacity of pure LiCoO2 was 64 µAh cm-2 µm-1, while 2% Ti- and Zr-doped films showed enhanced capacities 69 and 68 µAh cm-2 µm-1 (248 mC cm-2 µm-1, 245 mC cm-2 µm-1) respectively. The Zr-doped films exhibited good structural stability even after 25 cycles with the capacity retention of 95%. The kinetics of lithium ions in pure and Ti/Zr-doped LiCoO2 thin film cathodes and their cycleability are studied using both aqueous Pt//LiCoO2and and non-aqueous Li//LiCoO2 cells and the results will be presented.
Effects of Environmental Humidity on Self-Discharging Behaviour and Electrochemical Performance of Lithium-Ion Batteries
Authors: Byun Seoungwoo , Park Joonam , Appiah Williams Agyei , Park Jinkyu , Ryou Myung-Hyun , Lee Yong Min
Published: February 2020

The application of lithium ion batteries (LIBs) have been widen from IT devices to electric vehicles (EVs). To be precise, EVs adopting LIBs are being increased because LIBs guarantee high energy density and cycle life. LIBs are also sensitive to external environmental factors such as temperature, humidity, vibration, etc. In order words, these conditions should be controlled for better battery performance and reliability. Most of the studies on LIBs have been focused on temperature as the key environmental factor, however, other variables such as humidity should be also considered carefully for EV application. Hence, this work focuses on the effect of humidity on self-discharging and battery degradation behaviour.

Herein, we try to unveil the effect of relative humidity on self-discharging behaviour of fully charged LIBs by monitoring open-circuit voltages (OCVs), capacity and power retention, and electrochemical impedance before and after storage. Pouch-type LIBs having LiNi1/3Co1/3Mn1/3O2/graphite chemistry are fabricated, and then stored at room temperature under high humidity condition (>90%). As a result, the OCV drop is much higher at high humidity condition, which causes more degradation of capacity and power than expected. This abnormal result will be discussed in more detail via various case studies and analysis.

References

1. R. Yazami and Y.F. Reynier,  Electrochemica Acta, 47, 1217 (2002)

2. I. Bloom et al., Journal of Power Sources, 15, 238 (2001)

Acknowledgements

This work was supported by the Human Resource Training Program for Regional Innovation and Creativity through the Ministry of Education and National Research Foundation of Korea (NRF-2014H1C1A1066977).

Figure 1
Enhanced Performance of Li-Ion Battery Cathodes By Polymeric Artificial Solid Electrolyte Interphases
Authors: Wu Nae-Lih
Published: February 2020

The development of advanced Li-ion battery (LIB) cathodes has been directed toward high capacity, high voltage and good cycle life. The ability for high-temperature operation is also desired for certain applications, such as electric vehicles. Unfortunately, the cycle stability of typical LIB cathodes deteriorates rapidly either under high voltage or high temperature because of strong interaction at the solid-electrolyte interface causing rapid SEI formation and dissolution of the transitional metal ions of the cathode oxides. Particularly at elevated temperatures, the LiPF6 based electrolyte can readily decompose and reacts with residual water in the electrolyte to generate HF, which readily attacks the cathode surface causing side reactions and cathode dissolution. To solve these problems, researchers in the past have proposed to apply oxide coatings, such as MgO, TiO2, ZrO2, ZnO, Al2O3, etc., to reduce direct contact of the cathode with the electrolyte solution. Unfortunately, these approaches also lead to additional drawbacks, such as the crack of oxide layers, decrease of ion-conductivity, or involve more complex high temperature calcination steps, which may increase the processing costs. In this research, a simple approach using polymeric artificial SEIs to modify the surface of cathode materials to enhance the cyclic and rate performance of the Li-ion batteries at elevated temperatures or high potential is proposed in this work. Various polymeric blends were employed for modification of the cathode surface. The result showed that the polymeric SEIs could substantially suppress the deteriorating reactions between the electrolyte and electrode, improve the structural stability and decrease the polarization of the material during the electrochemical operations. Compared to the pristine cell, the modified cells show better performance both in cycle life and rate capability, maintaining lower cell impedance due to the reduced electrolyte decomposition and enhanced structure stability. The underlying mechanism is discussed.

Figure 1
(Battery Division Research Award) Activating Oxygen Chemistry for Energy Storage
Authors: Shao-Horn Yang
Published: February 2020

A critical element in realizing sustainable energy is to have efficient energy conversion and storage. Activating oxygen chemistry is central to enable efficient redox of small molecules of energy consequence, including (photo)electrochemical water-splitting, regenerative fuel cells, and metal-air batteries, and enhance lithium ion storage. Establishing a fundamental “design” principle” or function descriptor that links electronic structure to functions such as the catalytic activity can guide the design of materials that are cost effective. Recent advances in identifying the design principles of transition metal oxides for of oxygen electrocatalysis and lithium intercalation will be presented. We will also discuss how oxide bulk electronic structures can influence the reaction mechanisms. Lastly, connecting bulk electronic structure to surface chemistry is challenging but much needed, and some in-situ synchrotron X-ray measurements will be discussed at the end.
Coronene-Based Conductive and Ductile Polymer Binder for Lithium-Ion Batteries
Authors: Taskin Omer Suat , Yuca Neslihan , Cetintasoglu Mehmet Emre , Dogdu Murat Ferhat , Avci Ipek
Published: February 2020

Lithium-ion batteries (LIP) are becoming more common in portable electronic devices due to their high energy density, lack of memory effect, and high charge and discharge rate capabilities. Li-ion batteries are a relatively new technology, first marketed in the early 1990s, and research and development work is ongoing to improve safety and increase capacity, charge/discharge rate, and lifetime.

In this work, the development of a synthetic process for the next generation of coronene-based polymeric binders with high conjugation and very ductile backbone structures along the chains was showed. The reaction proceeds through the free-radical polymerization of the acrylate backbone. The polymerization process does not require the transition metal catalyst and has relaxed requirements to the experimental condition.

In summary, a new type of side-chain electron-conducting polymer binder was developed and it showed the stable and high capacities at a C/3 cycle rate.

Figure 1
The Effect of Polymer Binder on the Electrochemical Performance of Si/C Anodes
Authors: Terborg Lydia , Ling Min , Nie Kaiqi , Dahi Antoine , Wu Chenghao , Guo Jinghua , Ross Philip N , Liu Gao , Kostecki Robert
Published: February 2020

Silicon with its theoretical capacity of 4200 mAh/g is an attractive alternative to graphitic carbon in lithium ion batteries.[1] However, silicon suffers from poor passivating behavior in organic electrolytes electrolyte side reactions, which both result in large irreversible capacity loss and gradual electrolyte consumption with a lithium inventory shift in the Li-ion cell. Furthermore, large crystallographic volume changes (~320%) occur during cycling, which leads to particle decrepitation, particle isolation, and electrode delamination. This has negative impact on the interfacial stability and the composite electrode mechanical integrity.

To assure electronic connectivity and mechanical integrity of the composite Si/C electrode during extended charge-discharge cycles, the polymer binder needs to exhibit unique physic-chemical properties. Therefore it is essential to understand the basic properties and the polymer binder and its effect on the electrochemical performance of Si/C anodes.

Chemical changes in polymer binders during cycling are carefully monitored and evaluated. Thin films (20 nm) of binder polymers like, polyacrylic acid lithium salt (PAALi), poly-1,1-difluroethane (PVdF) and poly(1-pyrenemethyl methacrylate) (PPY), are spin coated onto B-doped Si (100) wafers, which reproduce the thickness of the polymer films in the composite Si electrode if the polymer coats the Si particles uniformly. Electrochemical studies provide information about Li+ doping, possible polymer reduction, interfacial reactions and surface layer formation. The surface chemistry at the electrolyte side as well as the substrate/binder interphase is carefully analyzed and evaluated. These basic phenomena are then linked with the Si/C electrode electrochemical performance and electrode/cell life.

This study also focuses on the determination of the mechanical properties of various binders before and with cycling. Stress-strain curves, indentation measurements and adhesion tests give information about properties needed to withstand the large volume changes during cycling. Furthermore, possible chemical deterioration of binders and possible its adverse effects on adhesion, crack initiation, growth, and particle delamination are monitored. These results can be used to develop and/or select effective binder candidates, which can lead to more efficient Si-based high-energy Li-ion battery systems.

Acknowledgements

This work was supported by the Assistant Secretary for Energy Efficiency and Renewable Energy, Office of Vehicle Technologies of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231, under the Applied Battery Research for Transportation (ABR) Program and Award Number DE-EE0006443.

[1] T. D. Hatchard, J. R. Dahn, Journal of the Electrochemical Society 2004, 151, A838.
Polyanion Glass Cathodes -- a Clearer Picture
Authors: Kercher Andrew Keith , Kolopus James A. , Sacci Robert L , Ruther Rose Emily , Carroll Kyler J. , Boatner Lynn A. , Dudney Nancy J
Published: February 2020

Polyanion glasses are a relatively unexplored class of high capacity cathode materials (250-500 mAh/g) for applications in lithium ion batteries that can undergo intercalation and/or conversion electrochemical reactions. Unlike most crystalline polyanionic materials, polyanion glass materials can be varied widely in both the cation and polyanion composition. This huge compositional space presents an opportunity and a challenge: how do you tailor the glass composition to obtain optimal electrochemical performance?

Glass composition is often discussed in terms of: glass formers, stabilizers, and fluxes. In our polyanion glass cathodes, glass formers (borate, phosphate, vanadate, and molybdate) provided the overall amorphous network of the glass and can be tailored to improve the conductivity and ionic transport. Our “stabilizers” typically contained the electrochemically active cation (iron, copper, cobalt, nickel, silver, antimony). Fluxes typically are associated with alkali ions and tend to reduce the chemical stability of the glass, and interestingly, flux cations include the lithium ions that diffuse into and out of the glass during cycling. Compositional substitution in the glass former, stabilizer, and flux of a polyanion glass cathode were shown to affect the 1st cycle reversibility, long-term cycleability, and energy efficiency.

Characterization was performed on as-produced glass, glass cathodes at different states of charge, and glass cathodes at different amounts of cycling to understand the fundamentals of the glass cathode structure and its associated electrochemical performance. X-ray absorption spectroscopy performed on glass cathodes at different states of charge showed valence changes in both the stabilizer cation and a glass former (vanadate) during electrochemical reactions. The valence change in the vanadate was identified as the primary source of 1st cycle irreversible loss, whereas the valence changes in the stabilizer cation were typically reversible and were associated with gradual capacity fade during cycling. Transmission electron microscopy showed that metal nanoparticles formed uniformly throughout glass particles during the glass-state conversion reaction. IR & Raman spectroscopies of mixed polyanion glasses were used to identify key functional groups that were associated with reduced 1st cycle irreversible loss and improved energy efficiency during cycling.

This work was supported by the Assistant Secretary for Energy Efficiency and Renewable Energy, Office of Vehicle Technologies of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231, under the Advanced Battery Materials Research (BMR) Program.
Flexible, Three-Dimensional Ordered Macroporous TiO2 Electrode with Enhanced Electrode-Electrolyte Interaction in High-Power Li-Ionbatteries
Authors: Lui Gregory , Li Ge , Wang Xiaolei , Jiang Gaopeng , Lin Edric , Fowler Michael , Yu Aiping , Chen Zhongwei
Published: February 2020

A simple methodology is developed for the in-situ preparation of flexible, three-dimensional ordered macroporous (3DOM) TiO₂ electrodes with greatly enhanced mass transfer. The 3DOM electrode is fabricated using a polystyrene colloidal crystal templated carbon cloth, and provides significant improvements over conventional nanoparticle electrodes without the use of binder or other additive. When evaluated as an anode in a Li-ion battery, the 3DOM electrode provides outstanding high rate performance. The electrode provides a specific capacity of 174 mAh g-1 at a current density of 2 A g-1, which is 2.6 times greater than that achieved with a nanoparticle electrode (68 mAh g-1). The 3DOM electrode also achieves excellent cycling stability, with a capacity retention of 94.8% (181 mAh g-1) over 1000 cycles at 10C (1.7 A g-1) compared to 93.7% (67 mAh g-1) for the nanoparticle electrode. To the best of our knowledge, the performance of our 3DOM electrode is among the highest of binder-free, flexible TiO₂ electrodes. We believe that this methodology is highly useful and is easily transferable to other materials and applications.
(Invited) Electron Channeling Contrast Imaging: Potential for Future Metrology in Semiconductor Industry
Authors: Vystavel Tomas , Prokhodtseva Anna , Schulze Andreas , Caymax Matty
Published: February 2020

For future scaling of CMOS technology beyond the 10 nm node it is necessary to integrate high mobility semiconductors including (Si)Ge and III/V compounds on silicon substrates. The lattice mismatch between these materials and the Silicon platform can lead to the formation of defects which will cause a degradation of the final device performance. Therefore, a metrology technique is needed to monitor the presence and density of defects in blanket layer as well as in patterned structures such as fins. There are several techniques for defect metrology including optical methods, X-ray diffraction or transmission electron microscopy, however, expected defect densities (<105 cm-2) make them ineffective for this task.

Electron channeling contrast imaging (ECCI) is scanning electron microscopy (SEM) technique used for the visualization and characterization of crystalline defects including dislocations or stacking faults. Distortions of the crystal lattice of a material due to the presence of such defects cause the variation of the backscattered electron intensity allowing for the visualization of the defects. Application of ECCI proved to be a consistent method for assessing the density and Burgers vector of different defect types in various materials with reliability comparable to that of transmission electron microscopy (TEM). Moreover, TEM limitations related to the destructive sample preparation necessity, limited viewed area accessible for each sample and possible difference in the behavior of thin samples compared to bulk ones brings SEM based ECCI as excellent candidate for non-destructive investigation of large sample areas with low defect densities. For such an analysis, areas exceeding 105 μm2 in size need to be examined to ensure proper statistics. Therefore, automated acquisition of a set of tiles that can be stitched into a single image with a resolution allowing for the detection of single threading dislocations is required. Important parameter for high contrast ECCI of crystalline defects is the sample orientation with respect to the electron beam. The sample should be oriented close to the Bragg condition. This is facilitated by the acquisition of Electron Channeling Patterns and simultaneous sample tilting and/or rotation. For the majority of samples based on silicon wafers only require a couple of degrees tilt from the zone axis. Hence, the technique can be applied to 300 mm wafers easily.

The presented technique allows the visualizing and analyzing the density and distribution of threading dislocations in blanket SiGe layers of different defect densities, strain relaxed buffers as well as on (Si)Ge and III/V fin structures. Therefore we are able to demonstrate that automated image acquisition of ECCI has big potential as possible metrology tool for future semiconductor devices process.
(Invited) Negative Capacitance Transistors
Authors: Salahuddin Sayeef
Published: February 2020

Phase transition materials have long been investigated for fundamental physics and also for potential application in electronics. In this presentation, I shall discuss how a controlled manipulation of the stored energy of phase transition can lead to a state of negative capacitance, especially within the context of ferroelectric materials. Our recent experiments with ferroelectric materials have shown that such a state of negative capacitance can actually be achieved. Negative capacitance can be combined with conventional transistors to achieve steep subthreshold swing. We have recently demonstrated this effect in a scaled transistor. These results and their implications will be discussed.
(Invited) Beyond CMOS Spintronics
Authors: Radu Iuliana
Published: February 2020

Beyond CMOS devices are being intensively studied to expand functionally for future technology nodes. Amongst them, those based on spintronic effects are very interesting for logic applications as they can provide new functionality and revolutionize circuit design. Spintronic logic devices are expected to be non-volatility and because of the physics involver they are expect to provide ultra-low power operation. Additionally, by using majority gate devices, improved circuit efficiency could be achieved. Majority gates are devices that can have a large number of inputs, a large number of outputs and a certain number of control gates. The simplest majority gates have 3 inputs and one output and the state of the output is given by the majority of the inputs. Spin devices are particularly amenable to building majority gates, unlike transistor devices. If majority gates are used, many arithmetic circuits could be built more efficiently. In this paper, we will review different types of spintronic majority gates and discuss materials and circuits implications from using these devices.
The Effect of H-Implantation Energy on the Annealing Kinetics of Germanium Surface Blistering
Authors: Yang Fan , Zhang Xuan Xiong , Shen Yuming , Ou Yi , Jiao Jiwei , Meng Hua
Published: February 2020

The impact of implantation energy on hydrogen-induced blistering in germanium is investigated. The results demonstrated that the kinetic plots (shown in Figure 1) were not only shifted through translation with the variation of H-implanted energy but also a break point occurred for H-implanted Ge with a low energy or low dose in the plot, which is a straight line accorfing to the Arrhenius formula. The dynamic plots of Ge blistering after a H-implanted Ge wafer were modified into a single straight-line with increasing H implantation energy similar to the fluence increasing. The characterizations of the cross-section transmission electron microscopy (XTEM) indicated that <001> H-platelets parallel to germanium surface played a main role in the subsequent exfoliation. According to the observation of optical microscopy for different H implantation fluences (shown in Figure 2) and the analysis of the critical statistic dimension (i.e. broken blisters) (shown in Figure 3), we propose a model (shown in Figure 4) that can reasonably explain the critical dimension variation with H-implantation energy even though the same dimension <001> H-platelets is viewed.

Figure 1
(Invited) SiGe Applications in Automotive Radars
Authors: Liebl Wolfgang , Boeck Josef , Aufinger Klaus , Manger Dirk , Hartner Walter , Heinemann Bernd , Lachner Rudolf
Published: February 2020

An overview of the SiGe technologies used at Infineon Technologies for radar applications will be given. The production of bare-die chips started in 2009 using the bipolar technology B7HF200. Since 2012 packaged MMICs in an embedded wafer level ball grid array (eWLB) are available. Process challenges and solutions for radar chips in an eWLB package are presented. Examples of commercial SiGe radar chips in production are shown. Furthermore Infineon’s next generation BiCMOS technology B11HFC with fT of 250 GHz and fmax of 370 GHz is described. In addition, significant improvements of the cut-off frequencies can be achieved by replacing the currently used double poly self-aligned configuration by a more advanced SiGe HBT architecture like IHP’s transistor module with selective base link epitaxy. The capability of this transistor cell for future BiCMOS generations was demonstrated by integrating it into Infineon’s 130nm CMOS process. A transistor performance with fmax of 500GHz was achieved.
Growth Rate and Temperature Dependence of Oxygen Incorporation in Si1-XGex Thin Films
Authors: Jackson Clayton Adam , Williams Adam J , Deelman Peter W
Published: February 2020

A series of Si1-xGex heterostructures were grown at different substrate temperatures using molecular beam epitaxy (MBE) on Si (100) substrates, where the composition x was varied in a “staircase” pattern by stepping down the germanium flux between constant composition layers while maintaining a constant silicon flux, and vice versa. The silicon flux was supplied with an e-beam evaporator, while the germanium flux was provided with an effusion cell. The germanium composition and oxygen concentration of these staircase structures were then measured using secondary ion mass spectroscopy (SIMS). From the SIMS profiles, it is evident that the oxygen concentration is inversely proportional to and linear with growth rate, regardless of how that rate is changed (either fixing silicon and varying germanium or vice versa). This implies that the dominant source of oxygen contamination in a clean growth system does not originate from either the silicon or germanium, in which case the concentration would be exponential with individual source rate or source flux, but instead comes from the residual background in the MBE chamber. Further, the oxygen concentration retains its linearity in growth rate when changing substrate growth temperature, and shows an exponential dependence in substrate growth temperature for a given rate, where the oxygen concentration increases at lower growth temperature.
Micro-Raman Characterization of Cluster Carbon Implanted Si before and after Rapid Thermal Annealing
Authors: Yoo Woo Sik , Kang Kitaek , Nishigaki Hiroshi , Hasuike Noriyuki , Harima Hiroshi , Yoshimoto Masahiro , Sekar Karuppanan
Published: February 2020

To meet various physical property requirements of materials for advanced high performance devices, combinations of Si1-xGex and Si:C have been introduced for strain control in PMOS and NMOS regions of devices. Two types of carbon (C) doping techniques have been explored for tensile stress generation in the NMOS device region. Carbon-doped Si epitaxial growth with C doping and C-implantation into Si are two major approaches. Carbon implanted Si requires annealing for recrystallization, damage recovery and tensile strain control.

Strain characterization, monitoring and control are as important as material preparation. Non-contact, non-destructive strain and crystallinity characterization techniques with high spatial resolution and virtual depth profiling capability are strongly desired for in-line monitoring.

In this study, we report the micro-Raman characterization results on cluster C-implanted Si for tensile strain generation before and after various rapid thermal annealing (RTA) techniques and conditions. Phosphorous ion clusters (P4) (8 keV, 4x1015 cm-2) were implanted with carbon ion clusters (C7) targeting 1.3% and 1.5% flat C profile (~50 nm from the surface). Various excitation wavelength laser beams were used in Raman characterization for virtual strain depth profiling. Flash anneal (fRTP) at 1200oC and impulse spike anneal (iRTP) at 1000oC and 1050oC were used as annealing conditions. As-implanted Si wafers showed almost no Raman signal due to the crystalline lattice damage from high dose cluster ion beam implantation. After RTA of implanted Si wafers under different techniques and conditions, significant broadening and shift of Raman peaks towards the lower wavenumber side was measured, indicating the presence of tensile strain and crystallinity alterations. X-ray diffraction (XRD), secondary ion mass spectroscopy (SIMS) depth profiling and transmission electron microscopy (TEM) analysis results will be reported along with multiwavelength micro-Raman characterization results.

Figure 1 shows 363.8nm excited micro-Raman spectra from reference Si and cluster C implanted Si wafers before and after rapid thermal annealing (RTA).

Figure 1
High Thermal Stability of Tensile Strained Direct Gap GeSn Crystallized on Amorphous Layers
Authors: Li Haofeng , Cuervo Covian Alejandra , Wang Xiaoxin , Liu Jifeng
Published: February 2020

In this paper, we systematically research the thermal evolution of substitutional Sn composition, tensile strain, and the direct bandgap of highly (111) textured, direct-gap Ge1-xSnx (0.075<x<0.085) thin films crystallized on amorphous SiO2 layers. We are able to demonstrate highly effective strain induced band-engineering in Ge1-xSnx as high performance optoelectronic materials for monolithic 3D electronic-photonic integration. For a Ge0.913Sn0.087 thin film, xSn stays at 8.7 at. % without any Sn segregation even after 2 hours of annealing at the crystallization temperature of 464 oC, indicating that the material is thermally stable in the entire back-end-of-the-line processing temperature range (<450 oC). We then sequentially anneal the Ge0.913Sn0.087 sample from 500 oC to 700 oC at a step of 50 oC, for 15 min each step, and selectively etch away any surface segregated Sn after each step. After analyzing the materials using a combination of X-ray Diffraction (XRD) and Raman spectroscopy, we determine that the crystallinity improves with the increase of annealing temperature, as evidenced by decreased full width at half maximum of both Raman and XRD peaks. The GeSn film maintained its strong (111) texture, as evidenced by the >270 ratio of the strongest to second strongest XRD peak. The xSn only decreases slightly from 8.3 at. % at 500 oC to 7.4 at. % at 700 oC, still ~7 times higher than the equilibrium solubility limit of ~1 at. % whereas the in-plane tensile strain e|| increases by nearly 4 times from 0.12% to 0.44%. By measuring and fitting the absorption spectra, we find that remarkably, the 0.44% thermally induced biaxial tensile strain reduces the direct bandgap by as much as 0.125 eV, twice as effective as the tensile strain in Ge(100) films. Due to a smaller Poisson’s ratio under biaxial tensile stress, the (111) oriented films experience larger volume dilatation than their (100) oriented counterparts under the same in-plane tensile strain, thereby enhancing the beneficial effects of tensile strain on the indirect-to-direct gap transition. By fitting the data with deformation potential theory, we derive a dilatational deformation potential of -12.8+/-0.8 eV for Ge1-xSnx thin films with xSn=8 at.%. Despite of the slight decrease in Sn composition at high annealing temperatures, the tensile-strain-induced direct-gap shrinkage, not only extends the optical response to λ = 2.8 um for MIR applications but also leads to stronger direct-gap semiconductor behavior. These results indicate that tensile strained GeSn crystallized on amorphous layers offers both excellent direct-gap optoelectronic properties and fabrication/operation robustness for integrated photonics. The same concept can also be readily applied to epitaxial GeSn on (111) substrates to achieve more effective strain-induced band engineering.

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Surface Activation and Planarization with Gas Cluster Ion Beam for Wafer Bonding
Authors: Toyoda Noriaki , Sasaki Tomoya , Yamada Isao , Suga Tadatomo
Published: February 2020

Surface activated bonding (SAB) has been widely used for various semiconductor wafers. In the SAB process, atomic Ar ions bombard wafer surface to form activated surface. In order to form activated surface on materials which are susceptible to irradiation damage, we have been investigating the gas cluster ion beam (GCIB) as an alternative to atomic ion beams. Gas clusters are aggregates of several thousands of gaseous atoms. Therefore, energy per atom of a gas cluster ion can be easily reduced to several eV. Although energy/atom of a gas cluster ion is low, thousands of low-energy atoms bombard a target surface at the same location simultaneously. As a result, the energy density on the target surface became extremely high and non-linear collisions of atoms are induced. They induces unique irradiation effects of GCIB such as high-yield sputtering, surface analysis of organic materials, thin film deposition at low temperature, and surface smoothing, which are beneficial for surface activated bonding. In this paper, preliminary irradiation effects of surface activation and planarization with glancing incidence GCIBs will be reported. From in-situ XPS analysis of O1s peak intensity on Si(100) with native oxide, Ar-GCIB irradiation at 70o removed native oxide efficiently. On the contrary, mixing of native oxide by normal incidence GCIB might occur, which caused residual oxide layer formation. In addition, the surface roughness at oblique incidence showed lowest value (Ra < 0.5 nm) without ripple formations. Cross-sectional TEM observation with oblique incidence GCIB irradiation showed that the sub-surface damage was almost negligible. These results indicated the possibility of use of GCIB as low-energy ions for wafer bonding.
High Performance OTFTs with CNT/Metal Hybrid Electrodes and Their Application to Amoled Panel
Authors: Song Chung Kun , Kim Jae Sun
Published: February 2020

The contact resistance is an important factor to significantly affect performance of organic thin film transistors (OTFTs). In this paper, a new carbon nanotube (CNT) based hybrid electrodes are introduced for a low contact resistance of source and drain electrodes of OTFTs. The hybrid electrodes consist of the solution-processed CNTs and a metal (Al; CNT/Al or Au; CNT/Au) evaporated on the CNTs. The contact resistance of CNT/Al and CNT/Au hybrid electrodes was varied depending upon the thickness of Al and Au, as shown in Fig.1. For CNT/Al hybrid electrodes, the contact resistance exhibited the minimum of 2.9 KW∙cm (VGS = -30 V) at the Al thickness of 5 nm, which was smaller than 13 KW∙cm of the bare CNT electrodes and tremendously smaller than 4 MW∙cm of Au electrode. It was noticeable that the minimum contact resistance of CNT/Au was 0.9 KW∙cm at the Au thickness of 5 nm which was the lowest value ever reported. The mobility of OTFTs, which used pentacene as the semiconductor and polyvinylphenol as the gate dielectric, also followed the same metal thickness dependence as the contact resistance. The maximum mobility of OTFTs using CNT/Al and CNT/Au electrodes was 0.78 cm2/V∙sec and 1.0 cm2/V∙sec, respectively, at the same thickness of 5 nm, which was larger than 0.3 cm2/V∙sec of the bare CNT electrodes. A major origin of such enhancements was identified to be the smallest energy difference, which was obtained at the metal thickness of 5 nm, between the work function of the CNT/metal hybrid electrodes and pentacene HOMO (5.1 eV).

The CNT/Au electrodes were applied to OTFTs in AMOLED panel. The AMOLED panel consisted of 64 x 64 pixels where each pixel was composed of 2 OTFTs (switching and driving OTFT), 1 capacitor, and 1 OLED. A shown in Fig.2, the AMOLED panel successfully worked to display some patterns.

Figure 1
(Invited) The Compact Models and Parameter Extraction for Thin Film Transistors
Authors: Shur Michael
Published: February 2020

The challenge in the compact modeling of Thin Film Transistors (TFTs) is to accurately reproduce all regimes of operation (leakage, subthreshold, and above threshold) and account for short channel and non-ideal effects. The models should be suitable for the device characterization and parameter extraction. The non-ideal effects (which might be specific to a particular TFT type) include mobility degradation at high gate biases, velocity saturation (in poly-Si TFTs), drain-induced barrier lowering, self- heating, effects of the series resistance, and the floating-body effects. The self-heating and kink effects might become important in short channel devices [1]). The unified and universal charge control models [2] that describe both the above and below threshold characteristics with one generalized charge control equation are the basic FET models that have the advantages of a better convergence (avoiding the binning problem) and a relatively small number of parameters (simplifying the parameter extraction). These models have been augmented with the AC models that account for the RC constants represented by the fractions of the channel resistances in series with the gate-to-source and gate-to-drain capacitances for reproducing the frequency dispersion. The non-linear contacts have been modeled as non-linear transmission lines and/or non-ideal diodes. [3] Such compact TFT models have been implemented in circuit simulators [3] and, with certain modifications, they are suitable for the simulation of amorphous Si, poly-Si, monocrystalline silicon, and even organic TFTs. [4]

[1] L. Wang, T.A. Fjeldly, B. Iniguez, and M.S. Shur, Self-heating and Kink Effects in a-Si:H Thin Film Transistors, IEEE Trans. Electron Devices, Vol. 47, p. 387, February 2000

[2] T. A. Fjeldly, T. Ytterdal and M. Shur, `Introduction to device modeling and circuit simulation,' Wiley, NY 1997.

[3] B. Iniguez, L. Wang, Z. Xu, T.A. Fjeldly and M.S. Shur, Short Channel AIM-Spice Models for Amorphous and Polysilicon Thin Film Transistors, in Future Trends in Microelectronics. The Road Ahead, John Wiley and Sons, 1999, p. 213

[4] P.V. Necliudov, M.S. Shur, D.J. Gundlach, T.N. Jackson, Modeling of organic thin _lm transistors of different designs, J. Appl. Phys., December 15 (2000)

Figure 1