bluuebunny/crossref_metadata_2025 huggingface dataset:
Ionic Conductivity and Electronic Insulation in a Nanoscale Interlayer for Improved Solid Electrolyte Performance
Authors: Hitz Emily , Xie Hua , Lin Yi , Connell John W. , Rubloff Gary W , Lin Chuan-Fu , Hu Liangbing
Published: December 2020

Growing demands for versatile, high-energy-density energy storage bring inorganic solid electrolytes to the forefront of research for future battery designs. Dendrite formation and subsequent electrical shorting in solid electrolytes, however, present a critical obstacle to their widespread implementation in energy storage devices. Based on research that suggests a dependence of dendrite formation on the electronic conductivity of a solid electrolyte, we propose the rational design of a thin (<100 nm), conformal layer of electronically insulating, ionically conductive material at the interface between garnet-type LLZO electrolyte and a metallic Li-Sn alloy anode. Selection of the solid electrolyte LiPON as the material for the electronically insulating layer facilitated application by atomic layer deposition, a technique which ensured continuity across the garnet substrate surface. The LiPON layer enabled dendrite inhibition while promoting ionic conductivity through the electrolyte matrix over a long cycle life. Potential step chronoamperometry and electrochemical impedance spectroscopy performed on the LiPON-coated LLZO electrolyte matrix demonstrate the excellent electronic insulating ability of the applied layer, as evidenced by a dramatic drop of over two orders of magnitude in the electronic leakage current while maintaining practical ionic conductivity. In a galvanostatic cycling protocol of over 200 h (100 cycles) using a maximum current of 0.1 mA⸱cm-2, symmetric coin cells consisting of LiPON-coated LLZO with Li alloy electrodes successfully demonstrated superior electrochemical stability and longer cycle life compared to a bare LLZO control. Our observations, confirmed by various spectroscopic techniques and post-cycling electron microscopy for visualization of Li dendrites and interface characteristics, support a new understanding of the possible failure mechanisms in LLZO solid electrolyte. Our simple and adaptable strategy yields new insight for the design of other dendrite-free solid-state electrolytes.
Introduction to Neocarbonix: Binderless Electrodes for Lithium-Ion Batteries
Authors: Brambilla Nicolo
Published: December 2020

Energy storage electrodes are often limited in their electrochemical stability and electrical performance by polymer binders used in the active material layer. Binders are also used to adhere the active material to the current collector. Binders are usually polymeric resins used in electrodes to mechanically hold active material powders together. Active materials may be graphite, silicon-carbon, silicon oxides for anodes, and lithium metal oxides for cathodes in the case of lithium-ion batteries (LIBs). They can also be high surface area activated carbons, in the case of EDLCs. The binders are a passive component in energy storage electrodes and they carry limitations in terms of electrical conductivity, thermal stability and chemical stability.

Capacity and C-rate capabilities in LIBs and ESR in EDLCs suffer because electrically insulating inactive binder material takes up space within the electrode material. Meanwhile lifetime at temperature and voltage can suffer as the binder material interacts with the internal electrochemical system of the energy storage device. Additionally, thermal stability of the electrode can be limited both by the electrochemical activity of the binder material as well as phase transitions of the binder material. Performance of energy storage systems using conventional electrodes in particularly high power applications may be limited by the thermal stability of the binder as well. Internal heat dissipation in those applications can be a serious concern when combined with ambient temperatures, especially in space-constrained environments or in applications where thermal management is at a premium. Energy density is also limited by the thickness of active materials that a standard coating process with binder-containing slurry can yield. Finally, cost of electrode production is dramatically impacted by the slurry drying step, as strong solvents with high boiling point (e.g. NMP) must be used to dissolve polymer binders, and are difficult to evaporate.

Nanoramic has developed an alternate solution - Neocarbonix - an electrode platform technology that effectively replaces polymer binders and primers. Results have been demonstrated for both LIB cathodes and EDLC electrodes. Nanoramic's Neocarbonix electrodes have significantly lower ESR, better C-rate capabilities, greater active material thickness for improved energy density, while also retaining or improving specific capacity. Lifetime at high temperature is also significantly improved, because of the increased thermal and chemical stability of the electrodes.

Electrode production cost is also dramatically reduced, as the Neocarbonix process is solvent-agnostic. The solvent can be selected to speed up the drying process during coating, which dramatically improves the production throughput.
Improving Performance of Cation-Disordered Rocksalt Oxyfluoride Cathodes
Authors: Ahn Juhyeon , Chen Dongchang , Chen Guoying
Published: December 2020

The development of next-generation rechargeable batteries requires cathode materials with elevated energy and power densities, increased lifespan and safety, as well as reduced cost. Lithium-rich cation-disordered rocksalt (DRX) compounds, composed of a redox-active transition-metal (TM) cation such as Mn3+ and a redox-inactive d
0 TM cation such as Ti4+, Nb5+ and Mo6+, are promising new cathode materials in meeting these requirements. The high capacity in this class of materials originates from the combined redox activities of Mn cations at lower voltages and oxygen anions at higher voltages, typically around 4.5 V. While the Mn redox process is fairly reversible, O redox often has limited reversibility which presents significant challenges in maintaining cathode cycling stability.

In this presentation, we report the excellent performance of a new Mn-rich DRX oxyfluoride cathode material based on the Li-Mn-Nb-O-F system. The phase-pure material was synthesized by using a fluoropolymer precursor in the solid-state reactions. The initial capacity contribution of the cathode was primarily attributed to Mn3+/Mn4+ redox with little O redox participation. The unique redox behavior, evidenced by the defined regions on the voltage profile (Figure 1a) and the dominating reduction peak near 3 V (Figure 1b), leads to a high discharge capacity and impressive cycling stability (Figure 1c). Stable cycling with a discharge capacity as high as 250 mAh g-1 was achieved. Combined with the high Mn content, the substitution of O anions with F likely increases the Mn migration barrier and consequently enhances overall stability.

Figure 1. Electrochemical performance of the Mn-rich DRX cathode: (a) charge and discharge voltage profile, (b) the corresponding differential capacity versus voltage profile, and (c) discharge capacity as a function of cycle number.

Figure 1
Silicon Nanoparticles in Li-Ion Batteries: Understanding the Role or Particle Size, Surface Oxidation, and Processing Conditions on Composite Electrode Longevity
Authors: Carroll Mike , Pach Gregory , Neale Nathan
Published: December 2020

The high theoretical gravimetric charge density (4200 mAhr g-1), low lithium storage voltage (0 – 0.4 V vs Li metal), elemental abundance, and existing expertise in manufacturing make silicon a promising candidate as an anode material for next generation lithium ion battery (LIB) technology. However, broad adoption of silicon is limited by the rapid electrode failure associated with irreversible process related to repeated charge and discharging. Because of the extreme volume changes of the silicon active material with lithium alloying (~300% at Li3.75Si) the electrode experiences large mechanical stressors. In addition, the highly reducing environment upon lithium silicide formation forces chemical reactions between the active material and electrolyte and other electrode components which result in a heterogeneous interfacial layer called the silicon-electrolyte-interphase (SEI). The role and composition of the SEI is complex, however, the SEI is hypothesized to passivate the Si surface against additional parasitic reactions but is also prone to mechanical degradation from repeated cycling. These aspects of lithium storage in silicon slow the on-ramp of silicon in LIB anodes.

To begin to alleviate these irreversible processes in silicon-based electrodes we study the effect of silicon particle size, processing conditions, and electrolyte formulation on the electrode’s cycle stability, rate capability, and calendar life. We find that upon exposure to water, all silicon in our single-nanometer scale particles are oxidized to SiO2, which, we show, has no reversible lithiation capacity in the electrochemical potential window of normal silicon lithiation. We find a very strong relationship between the silicon particle size and the cycle stability, where, smaller silicon particles show a profound improvement on the capacity retention, but, due to the high surface area-to-volume ratio, also have an increased rate of reaction with the electrolyte. These results help to build a more comprehensive understanding on the role the electrode processing conditions and silicon particle size, and provide a foundation for additional work to improve the longevity of silicon in lithium ion battery devices.
(Invited) New Structural Design and Synthesis of Sulfur-Carbon Composite Materials for Lithium-Sulfur Batteries
Authors: Suk Jungdon
Published: December 2020

The development of electric vehicles and smart grids necessitates the search for next-generation secondary batteries possessing increased energy densities, with the lithium-sulfur (Li-S) battery being one of the most promising candidates satisfying these demands. Specifically, Li-S batteries are promising energy storage and conversion systems owing to their high theoretical specific energy capacity (1675 mAh g-1) and energy density (2567 kWh kg-1) [1]. However, the practical use of Li-S batteries is hindered by their low specific capacity, low coulombic efficiency, poor rate capability, and poor cycling stability caused by the low conductivity of sulfur (5 x 10-30 S cm-1), dissolution of polysulfides (Li2Sx, 2≤ x ≤ 8) in the electrolyte and their redox shuttling/parasitic reactions and high volume expansion during discharge [2]. To overcome these drawbacks, many studies have focused on developing the design and materials of nanostructured host, electrolyte, interlayers, separators, additives, etc [3]. Interconnected three-dimensional frameworks comprising multi-walled carbon nanotubes, graphene, or carbon particles offer a combination of constituent advantages and can thus be used to achieve superior energy conversion and storage properties.

Herein, we designed and prepared various approaches for interconnected highly conductive carbon materials which enable to make sulfur composite materials for Li-S batteries. The resultant sulfur-carbon composite paper cathode exhibited high reversible specific capacity of 1386 mAhg-1, good rate capability up to 5C, and excellent cycling performance (a capacity retention 68% after 400 cycles), all of which are significantly improved from those of bare sulfur cathode or sulfur-GO composite only [5]. Rational design of cathode composition, structure, and a simple fabrication process can give insight into the development of various advanced cathode materials for high performance Li-S batteries.

References

[1] X. Ji, K.T. Lee, L.F. Nazar, Nat. Mater. 8 (2009) 500.

[2] Y. Yang, G.Y. Zheng, Y. Ciu, Chem. Soc. Rev. 42 (2013) 3018.

[3] Y.X. Yun, S. Xin, Y.G. Guo, L.J. Wan, Angew. Chem. Int. Ed. 52 (2013) 13186.

[4] H.J. Peng, J.Q. Huang, X.B. Cheng, Q. Zhang, Adv. Energy Mater. 7 (2017) 1700260

[5] J. Kim, Y. Kang, S.-W. Song, J. Suk, Electrochimica Acta 299 (2019) 27.
Improved Mass Transfer of Methyl Viologen By the Nitrate As Counter Anion for Aqueous Redox Flow
Authors: Jin Chang Soo , Jang Sang Soon , Park Se-Kook , Yeon Sun-Hwa , Jung Yoon Seok , Shin Kyoung Hee
Published: December 2020

Among the redox active materials, viologen compounds are the most promising redox species, featuring the stable redox reaction MV2+/MV+ and the tunability of the substituents and counter anion, indicating that its electrochemical properties (i.e., diffusion coefficient and electron transfer rate constant) are significantly influenced by the substituents and counter anions[1-8]. Herein, we present the viologen compound employing nitrate as counter anion (MV2+*2NO3
-) as an aqueous redox active material. The MV2+ 2NO3
- was synthesized and characterized by elemental analysis, nuclear magnetic resonance (NMR) spectroscopy, and Raman spectroscopy, and then, the electrochemical properties were studied using cyclic voltammetry and rotating disk electrode techniques. Compared with MV2+ 2Cl- using chloride as the counter anion, which is commonly used an anolyte, it was demonstrated that MV2+ 2NO3
- featured fast mass transfer properties (D = 5.13 x 10-5 cm2 s-1) and comparable kinetics (Ket = 9.68 x 10-3 cms-1.

Reference

[1] B. Hu, Y. Tang, J. Luo, G. Grove, Y. Guo, T.L. Liu, Improved radical stability of viologen anolytes in aqueous organic redox flow batteries, Chemical communications 54(50) (2018) 6871-6874.

[2] B. Hu, C. DeBruler, Z. Rhodes, T.L. Liu, Long-cycling aqueous organic redox flow battery (AORFB) toward sustainable and safe energy storage, Journal of the American Chemical Society 139(3) (2017) 1207-1214.

[3] T. Liu, X. Wei, Z. Nie, V. Sprenkle, W. Wang, A total organic aqueous redox flow battery employing a low cost and sustainable methyl viologen anolyte and 4‐HO‐TEMPO catholyte, Advanced Energy Materials 6(3) (2016) 1501449.

[4] T. Janoschka, N. Martin, U. Martin, C. Friebe, S. Morgenstern, H. Hiller, M.D. Hager, U.S. Schubert, An aqueous, polymer-based redox-flow battery using non-corrosive, safe, and low-cost materials, Nature 527(7576) (2015) 78-81.

[5] B. Dunn, H. Kamath, J.-M. Tarascon, Electrical energy storage for the grid: a battery of choices, Science 334(6058) (2011) 928-935.

[6] P.M. Monk, N.M. Hodgkinson, Charge-transfer complexes of the viologens: effects of complexation and the rate of electron transfer to methyl viologen, Electrochimica acta 43(3-4) (1998) 245-255.

[7] P. Monk, viologens, Wiley1998.

[8] C. Bird, A. Kuhn, Electrochemistry of the viologens, Chemical Society Reviews 10(1) (1981) 49-82.
Synthesis and Electocatalytic Activity of MnO2/RuO2/Carbon Nanocomposites to Enhance Lithium-Oxygen Battery Performance
Authors: Nahm Kee Suk
Published: December 2020

Lithium-oxygen battery has received much attention as a potential energy storage system because of its ultra-high theoretical energy density (5,200 Wh kg−1), which remains to be the most promising future technology. However, there are several scientific/technical hurdles that must be overcome in order for a rechargeable Li–air battery to be commercialized in the market. In particular, the incomplete decomposition of solid discharge products such as Li2O2 etc. formed during discharge process passivates the cathode surface by clogging pores of the porous carbon cathode, resulting in diminishing the overall performance of battery. In order to solve these issues, great effort has been devoted to designing and developing novel electrocatalysts. It has been reported that electrocatalysts play an important role in ORR and OER, and hence improve the kinetics and efficiency of the Li–air battery.

In this work, a suitable bifunctional catalyst was synthesized with MnO2 and RuO2, which are the well-known catalysts for oxygen reduction reaction(ORR) and oxygen evolution reaction(OER), respectively, by supporting on two different carbon supports such as graphite nanofiber(GNF) and graphene oxide(GO) for the application to oxygen cathode bifunctional catalysts of lithium-air batteries. MnO2/GNF was first prepared by a simple hydrothermal synthesis and was then decorated with various decorating ratios of RuO2 using a simple redox reaction technique. A good electrocatalytic performance was observed from a weight ratio of RuO2:MnO2/GNF=5:5. The Li-oxygen battery fabricated with the synthesized catalyst composition delivered a reduced overpotential with good cyclability and high specific capacity. In order to understand the effect of carbon, urchin-shaped α-MnO2/RuO2 nanostructures was first synthesized by a hydrothermal synthesis and was then loaded on GO with a weight ratio of 5:5 using a redox reaction technique. The synthesized α-MnO2/RuO2@GO (5:5) composite delivered high specific capacity with excellent electrocatalytic activity. Between the two different carbon supported composites, RuO2@MnO2/GNF showed excellent catalytic activity than α-MnO2/RuO2@GO. The increase in the surface area of carbon supports greatly influenced the performance of Li-air battery. Catalysts with carbon supports showed higher activity than without carbon. RuO2@MnO2/GNF was found to be the best catalyst which has two or tree times larger surface area than α-MnO2/RuO2@GO. Thus, RuO2@MnO2/GNF with 5:5 weight percentage was found to be the best electrocatalyst than all other synthesized catalysts.
(Invited) Development of High-performance Si Anodes and O3-type Metal Oxide Cathodes for Next Generation Li-ion Batteries and Beyond
Authors: Li Xiaolin
Published: December 2020

Silicon is the most promising anode material for next generation high energy Li-ion batteries. While Na-ion battery is one of the closest beyond Li-ion technologies to commercial production and O3-type metal oxide cathodes are expected to deliver high performance in terms of specific capacity and energy density. In this talk, we will discuss the progress of our recent development on porous structured Si materials and localized high concentration electrolyte towards practical applications. For the development of O3-type layered cathode for Na-ion batteries, we will report the synthesis of O3-NaNi0.68Mn0.22Co0.10O2 cathode, which delivers a specific capacity of ~196 mAh/g and a specific energy of ~612 Wh/kg (based on the cathode). By controlling the surface phase transition and chemical reactivity with localized high concentration electrolyte, the Ni-rich NMC cathode demonstrated >83% capacity retention over 100 cycles between 2-4.2V (vs. Na/Na+). The cathode has a specific capacity of ~151 mAh/g between 2-4V and ~80% capacity retention over 1000 cycles. NaNi0.68Mn0.22Co0.10O2-hard carbon full-cells with practical loading (>2.5 mAh/cm2) and lean electrolyte (~40 µL) also were demonstrated. The capacity retention is ~82% after 450 cycles.
Welcome Remarks - G02: Atomic Layer Deposition Applications 16
Authors: Roozeboom Fred
Published: December 2020

Welcome to G01: Atomic Layer Deposition Applications 16! Take a moment to listen to welcome remarks from the lead organizer, Fred Roozeboom.
Fabrication of Yolk-Shell Silicon@Carbon Anode Via Iodination Treatment
Authors: Park Jonghyun , Song Hyeonjun , Cakmakci Nilüfer , Bang Daesuk , Jeong Youngjin
Published: December 2020

As the demand for lithium ion batteries (LIBs) with high energy density increases, silicon has attracted great attention as a next-generation anode material due to its high theoretical capacity of 4200mAh/g. However, silicon has been suffered from poor cycleability due to a large volume change during the lithiation process. To tackle this critical problem, some methods have been used, such as nano-sized silicon, porous silicon, and a hollow carbon/silicon composite. However, nano-sized silicon is expensive for commercialization. In addition, the harmful hydrogen fluoride (HF) acid is commonly used to etch silicon oxides for porous structure. In this study, a yolk-shell structure with a space between the carbon shell and micro-sized silicon was made without HF. The poly(vinyl alcohol) (PVA) coated silicon was treated with an iodine followed by stabilization at 200 oC. The iodination process converts the chemical structure of PVA to polyene structure and enhances the carbon yield. The yolk-shell structure was formed by the eliminating an untreated PVA layer during the carbonization process. The prepared yolk-shell silicon/carbon composite worked well as an anode electrode and showed a high initial discharge capacity of 3266 mAh/g and maintained 1700 mAh/g until 200 cycles.
Application of Stabilized Lithium Metal Powder (SLMP®) in Silicon Anodes for Advanced Lithium-Sulfur Batteries
Authors: Mahlendorf Falko , Meyer Thomas , Heinzel Angelika
Published: December 2020

Silicon is a potential anode material for lithium-sulfur batteries. This future energy storage system has an essential higher energy density and significantly lower costs compared to lithium-ion batteries. However, a big problem by using silicon is the high volume expansion of 280 %. The volume expansion and contraction results in a break-up of the solid electrolyte interface (SEI). The SEI has to be reformed continuously during cycling, which leads to a continuous loss of lithium. One approach to compensate the lithium loss during cycling is the prelithiation of silicon anode with a stabilized lithium metal powder (SLMP
®
). SLMP can serve as an additional lithium source to mitigate the capacity loss during the first and the following cycles and improve the energy density significantly.

Adding SLMP directly into the slurry during electrode production is problematic because it is incompatible with many conventional electrode components. Therefore the application of SLMP on the finished electrode as an additional layer is advantageous. For this purpose, the SLMP can be mixed in a solvent and applied to the electrode. After drying, the SLMP must still be activated by a pressing process, since the protective carbonate shell must be broken open. One problem here is the rapid separation of SLMP and solvent. A possible solution is the addition of a binder, like styrene-butadiene rubber (SBR).

Here we present a silicon/graphene-based anode prelithiated with SLMP in the electrolyte systems 1 M LiTFSI, 0.2 M LiNO3 in dimethoxy ethane (DME) and 1,3-dioxolane (DOL). For this work, we used a commercially available Si/C composite material with a PAA binder. The silicon content of the electrode is 25 %. SLMP is loaded on the top of the electrode and activated by a pressing process. The advantage of a binder in the SLMP - solvent mixture will be shown, and also that the binder has no negative effect on the electrochemical properties. The electrodes are examined by galvanostatic cycling and show high coulomb efficiency of over 85 % in the first cycle. Also, the SLMP of the anode compensates the lithium loss over at least 300 cycles. We will show the improvements of the anode prelithiated with SLMP compared to pure Si/C anodes.
Case Study of Li-S Batteries with Prolonged Life Performance
Authors: Cho Won-Il , Do Vandung
Published: December 2020

Li-S battery system has been investigated by large number of researchers due to its high gravimetric and volumetric energy densities. The system consists of lithium metal anode and sulfur-carbon composite cathode separated by polyolefin separators with ether-based electrolytes. Lithium metal is arguably one of the most promising anode materials in secondary lithium battery technologies due to its exceptionally high theoretical capacity of 3860 mAh g-1 and low electrochemical potential of 3.01 V vs SHE. However, high reactivity of lithium metal anode often leads to form problematic Li dendrites and causes coulombic instabilities that curtail cycle life and safety especially when sulfur is used as cathode. Here, we report how Li-S battery system has been studied in my group and synergistic approaches to protect the Li anode and stabilize the sulfur cathode to enhance electrochemical stability of the Li-S cell. In the first place, based on our strategy of CASE Study for reducing over-charge phenomena due to polysulfides dissolution into an electrolyte, various C-S composite cathode materials, modified separators with functionalized reduced graphene oxide and phosphorous graphitic carbon nitride, and modified electrolytes of high salt concentration are adapted. We show that protecting the lithium anode via direct creation of designed artificial solid electrolyte interphases (ASEI) on Li composed of negatively charged metal-oxide nanoparticle film that stabilizes electrodeposition and dissolution of Li. We suggest that CASE Study is very critical to facilitates high sulfur reutilization by interception of dissolved lithium polysulfides and facilitated electron transport, which enhance electrochemical stability of the electrodes. Finally we insist that high S loading electrode is a key to incarnate Li-S battery and our new binder is very effective for flexible cathode electrode to be processed.

Figure 1
(Invited) Tensile Strain Engineering and Defects Management in GeSn Laser Cavities
Authors: EL Kurdi Moustafa , Elbaz Anas , Wang Binbin , Sakat Emilie , Herth Etienne , Patriarche Gilles , Pantzas Konstantinos , Sagnes Isabelle , Sauvage Sebastien , Checoury Xavier , Chelnokov Alexei , Reboud Vincent , Chretien Jeremie , Pauc Nicolas , Calvo Vincent , Boeuf Frédéric , Boucaud Philippe , von den Driesch Nils , Grützmacher Detlev , Hartmann Jean-Michel , Buca Dan
Published: December 2020

We present GeSn material engineering to address both defect managements and band structure via tensile strain in laser cavities. We show that GeSnOI technologies allow to address both issues, with drastic reduction of power density thresholds in lasing devices at 2-3 µm wavelengths range.

First set of analysis were performed on GeSn micro-disks with removed defects from their active region. The GeSn layers, grown on Ge strain-relaxed-buffers (SRBs) on silicon, were etched into micro-disks cavities. A specific chemistry were used to remove the dense misfit dislocation array from the suspended area of the GeSn disk, which constitutes the laser gain media. We obtained reduced lasing thresholds from hundreds of kW/cm2, as commonly obtained in the literature at low temperature, to around 10 kW/cm2 in pulsed regime with Sn content as low as 7 % to 10.5 %.

In a second set of analysis we demonstrate a new approach relied on GeSn layers transfer on insulator, GeSnOI, with the aim to introduce SiNx stressor layers in an all-around geometry. [1,2] Tensile strain transfer from the stressor layers to GeSn micro-disks of 1.6% were reached, homogenously distributed in the disks volume. The defective interface were removed from the GeSn layer once it has been transferred on the host Si-substrate. This approach was applied to a GeSn layer with only 5.4% of Sn-content, which is nominally an indirect band gap semiconductor that cannot support lasing. The applied tensile strain transformed the Ge0.95Sn0.05 alloy into a direct-band gap material which support lasing with dramatically reduced thresholds, to 0.8 kW/cm2 at low temperature [3]. Tensile strain indeed yields to reduction of the valence band density of state by lifting the HH-LH degeneracy at the Γ-point, and thus contributes to reduce the lasing thresholds. The tensile strained GeSn lasers operate under continuous-wave-pumping up to 70 K thanks to further thermal management of the GeSnOI devices [3]. These results show the potential of new GeSn material engineering for future integration of laser sources on silicon platform using fully CMOS-compatible technology.

[1] M. El Kurdi, M. Prost, A. Ghrib, et.al. ACS Photonics 3, 443 (2016).

[2] A. Ghrib, M. El Kurdi, M. Prost, et. al. Adv. Opt. Mater. 3, 353 (2015).

[3] A. Elbaz et. al. Nature Photonics, March (2020) doi.org/10.1038/s41566-020-0601-5
(Invited) Engineering SiGeSn Semiconductors for MIR and THz Opto-electronic Devices
Authors: Assali Simone , Attiaoui Anis , Atalla Mahmoud , Alain Dijkstra , Kumar Aashish , Mukherjee Samik , Nicolas Jérôme , Koelling Sebastian , Moutanabbir Oussama
Published: December 2020

Sn-containing group IV semiconductors (Si)GeSn represent a versatile platform to implement a variety of Si-compatible photonic, optoelectronic, and photovoltaic devices operating from SWIR to MIR wavelengths. This class of semiconductors provides two degrees of freedom, strain and composition, to tailor the band structure and lattice parameter thus enabling a variety of heterostructures and low-dimensional systems on a Si substrate.[1]

In this presentation, the recent progress in the epitaxial growth and opto-electronic properties of metastable (Si)GeSn semiconductors with Sn contents above 15 at.% will be discussed. The growth of the (Si)GeSn multi-layer heterostructure is performed in a chemical vapor deposition (CVD) reactor on a Si wafer. By reducing the growth temperature, the Sn content in the alloy is increased, while preserving a high degree of crystal purity for the heterostructure in the topmost Sn-rich layer. Atom probe tomography (APT) measurements will be discussed to address the abruptness of the interfaces and the compositional profile across the GeSn multi-layer heterostructure.[2-4]

By tailoring the strain relaxation in Ge0.83Sn0.17 room-temperature photoluminescence (PL) emission wavelength above 4.0 μm upon is achieved.[2,5] The absence of defect- and impurity-related emission and limited carrier losses into non-radiative recombination channels will be addressed using temperature-dependent PL measurements. Direct band gap absorption will be shown using transmission measurements performed at room-temperature, with energies closely matching the PL data. These observations will be discussed in the light of photocurrent measurements on GeSn photodetectors operating up to ~4.6 μm at room-temperature. The integration of p-i-n heterostructures in GeSn photodetectors will be investigated by correlating structural and opto-electronics properties of the fabricated devices.

In addition, strategies to further extend the operational wavelength range of (Si)GeSn devices toward THz wavelengths will be discussed.

[1] S. Wirths, et al., Prog. Cryst. Growth Charact. Mater. 62, 1 (2016)

[2] S. Assali, et al., Appl. Phys. Lett. 112, 251903 (2018).

[3] S. Assali, et al., J. Appl. Phys. 125, 025304 (2019).

[4] S. Assali, et al., Appl. Phys. Lett. 114, 251907 (2019)

[5] S. Assali, et al., arxiv:2004.13858
Capturing the Effects of Free Surfaces on Threading Dislocation Density Reduction
Authors: Bioud Youcef Ataellah , Boucherif Abderraouf , Patriarche Gilles , Drouin Dominique , Arès Richard
Published: December 2020

The big concern with using silicon as a substrate for making Ge and III-V devices is the dislocation density in the epilayers. Dislocations degrade device performance by trapping the photo-generated carriers, dragging down efficiency.

In this presentation, we show that dislocation engineering using nanovoids in the heteroepitaxy of Ge/Si can be a plausible path for monolithic integration of high-quality GaAs on Si platform. Possible mechanisms responsible for threading dislocation (TD) density reduction through free surfaces located, either in the Ge layer or in Si substrate that lead to their annihilation or fusion are discussed. By combining various scanning and transmission electron microscopy techniques, it has been possible to link different effects of either of the free wedge surfaces on dislocation, particularly, threading arm pinning by nanovoids. The results suggest that introducing nanovoids favors recombination of TDs by increasing the characteristic interaction distance between neighboring dislocations. In fact, the creation of free surfaces could facilitate interactions between dislocations, enabling the dislocation network to change its connectivity in a way, which facilitates the subsequent annihilation of TD segments. In addition, the voids formed in the silicon substrate could potentially capture and thereby combine many more TDs. The TDs bend towards the voids in Si in order to minimize their length, causing their recombination and elimination at the nearest free surface thus leading to the creation of an almost defect-free Ge layer on Si [1].

The use of such a simple, industry friendly, inexpensive and self-organised process through electrochemical etching and thermal annealing could be crucial in cutting manufacturing costs and enabling market penetration of III–V on Si-based devices.

[1] Y. A. Bioud et al., “Uprooting defects to enable high-performance III–V optoelectronic devices on silicon,” Nat. Commun., vol. 10, no. 1, 2019.
(Invited) GaN Optoelectronic Devices Based on Local Strain Engineering
Authors: Ku Peicheng
Published: December 2020

Controlling strain is an important topic for the design of modern optoelectronic devices based on compound semiconductors. Excessive strain leads to defects and lowers device performance. But an adequate amount of strain can profoundly modify optoelectronic properties, resulting in new device capabilities. In this work, the strain in gallium nitride based heterostructures and its effects on optoelectronic properties are systematically studied. Specifically, strain is locally controlled and isolated using nanostructures. The effects of strain on the optical properties were obtained including emission wavelength, radiative efficiency, absorption, and polarization. Applications resulting from local strain engineering are proposed and demonstrated including single photon sources, microdisplays, spectrometers, and tactile sensing.

This study focuses on GaN disk-in-wire nanopillars fabricated using a top-down process although the results are expected to be applicable to similar structures obtained by bottom-up fabrication. The strain profile is modified due to the relaxation of strain around the perimeter of the nanopillar. A radial confinement potential ~hsec(r) is formed in a compressively strained layer, such as InGaN sandwiched by GaN. This radial confinement potential can help confine the electrons and holes toward the center of the nanopillar and reduce the impact of nonradiative recombinations on the surface. Moreover, the radial confinement potential enhances quantum confinement, enabling single photon emission to be observed from a nanopillar with a diameter as large as 37nm. In comparison, the exciton Bohr radius is only 3nm.

Top-down fabrication of GaN disk-in-wire nanopillars is enabled by a two-stage dry/wet etching process. A vertical sidewall with a high aspect ratio ~10 can be obtained. The top-down fabrication strategy has the unique advantage of allowing the cross-sectional shape of the nanopillar to be lithographically defined. Specifically, elliptically-shaped nanopillars were extensively studied. The asymmetric shape changes the light polarization properties, as shown by both theoretical and experimental studies.

Device applications were also studied. Because controlling the strain changes the emission wavelength, microdisplay devices comprising of multiple GaN light-emitting diodes of different colors can be monolithically integrated. In addition, similar multi-wavelength absorption properties can be achieved. In this talk, several device applications will be discussed including single photon sources, microdisplays, spectrometers, and tactile sensors.
(Invited) Probing Semiconductor Heterostructures from the Atomic to the Micrometer Scale
Authors: Koelling Sebastian , Assali Simone , Atalla Mahmoud , Kumar Aashish , Attiaoui Anis , Lodari Mario , Sammak Amir , Scappucci Giordano , Moutanabbir Oussama
Published: December 2020

Probing the quality of interfaces, dopant distribution, layer thicknesses, and crystalline quality in buried layers and volumes has been critical for developing new semiconductor materials and devices. These challenges have been addressed by a combination of techniques based on Electron Microscopy (EM) and Atom Probe Tomography (APT) for new transistor architecture1. We have extended their applicability to materials and devices developed for quantum information processing2 and photonic applications3-5 with significantly larger dimensionsaddressing the need for atomic scale metrology of heterostructures with thicknesses of up to several micrometers (Fig. 1).

For example, CMOS compatible Quantum cascade lasers based on superlattices of n-type Ge/Si1-xGex QWs are predicted to be operable at room temperature and to emit throughout the entire THz spectral region (300GHz-1THz, 1mm-30µm) solving a key challenge in solid-state optoelectronics5. In a QCLs charged carriers travel through the superlattice alternating between emitting radiation when traversing between the subbands of the superlattice and tunneling from one period of the cascade to the next3,5. In order to act as a laser, the underlying material structure has to allow for coherent radiation, population inversion, efficient tunneling and propagation of the emitted radiation. This implies the need to develop the growth of superlattices up to 1000s of periods that are highly uniform in thickness, strain compensated, of high crystalline quality, and have well controlled doping levels and steep interfaces reaching a thickness of several micrometers3,5.

Here we will show how we combine X-Ray Diffraction, EM and APT to characterize Ge/Si1-xGex superlattices and SiGe-, GeSn- and SiGeSn heterostructures to investigate interface properties, determine layer thicknesses, and map the distribution of dopants and isotopes6 in structures with micrometer dimensions. These studies are of compelling importance to enable a progressive improvement of these material systems towards their respective applications.

References:

1W. Vandervorst et al., Phys. Status Solidi C 11, 121 (2014)

2N.W. Hendrickx et al., Nature 577, 487 (2020)

3D.J. Paul, Laser Photonics Rev. 4, 610-632 (2010)

4S. Assali et al. Appl. Phys. Lett. 112, 251903 (2018)

5T. Grange et al., Appl.
Phys. Lett. 114, 111102 (2019)

6D. Sabbagh et al., Phys. Rev. Appl. 12, 014013 (2019)

Figure 1
Synthesis and Electrochemical Properties of Carbon Foam/SnS/C Composite for Flexible Lithium Ion Batteries
Authors: Yang Hae-Ri , Kim Jae-Hun
Published: December 2020

With the rapid development of flexible mobile electronics and wearable devices, the demand for flexible power sources continues to rise. Among various power sources, Li ion batteries (LIBs) have attracted a lot of interest as the power source of flexible devices due to their high energy density, reasonable cost, and long cycle life. However, conventional electrode fabrication process of LIBs is insufficient to satisfy flexibility of the flexible devices. Besides flexibility, there is still a challenge to increase energy density for long-lasting batteries. Currently, carbonaceous materials are used as commercial anode materials because of their good cycle performance. However, commercial graphite anode has limited capacity (372mAh·g–1), which cannot meet the requirements of high-performance LIBs. Therefore, development of high-capacity anode materials is critical. To increase the reversible capacity of an anode, Li-alloy type or conversion type materials have been intensively studied. Tin sulfide (SnS), which exhibits conversion reaction with Li ions, is one of the attractive anode materials because of its high theoretical specific capacity and large interlayer spacing. Despite these many advantages of SnS, SnS anodes cannot be commercially used due to some drawbacks. The poor electric conductivity of SnS and the fatal volume change during the discharge/charge cycles cause the poor electrochemical performance. To resolve these issues, there are many efforts such as introduction of carbon-based materials and use of SnS nanostructure. This study proposes a flexible carbon foam/SnS nano sheets/C composite as anode materials for flexible LIBs. An elastic carbon foam can be simply obtained by carbonization of commercially available and low-cost melamine foam. Carbon foam/SnS nano sheets structure was prepared by a simple solvothermal method. Then, a carbon coating on the composite was performed to further improve the cyclic performance. The prepared materials were investigated by various materials and electrochemical analysis tools. The obtained composite electrode exhibited excellent lithium storage performance.
Improved Initial Coulombic Efficiency of Optimized SiOx Via Simple Magnesiothermic Reduction As High-Performance Anode Material for Lithium-Ion Battery
Authors: Lee Sang-Min , Raza Asif
Published: December 2020

With the increasing demands of portable electronics and electric vehicles, rechargeable lithium-ion batteries are strongly considered from the utility standpoint due to their high energy density. Lithium-ion batteries have become a leading technology [1]. Silicon-based materials have gained tremendous attention due to their great importance in various techniques such as electronic devices, solar energy conversion and high capacity anode for LIBs [2]. Low cost, high energy density, SiO considered one of the most promising anode material for lithium-ion batteries. However low initial Coulombic efficiency is a serious limitation for the practical application of SiO. The intrinsic low Coulombic efficiency (ICE) caused by the side reactions between Li-ions and Si as well as the formation of Solid Electrolyte interphase (SEI) [3].

Many methods have been approached to solve this challenge, pre-lithiation, metal reduction, graphene coating, Nano-sizing, nanotubes, and fabrication of silicon and carbon composite. Among these methods, the metallothermic reduction has gained significant attention. The reducing metal should be inexpensive, convenient to handle and easily removable by-product, therefore Mg has been widely used metal to reduce Si oxides [4].

Herein, we report an affordable low temperature and low-cost synthesis method to synthesize SiOx by partial reduction of SiO via Magnesiothermic reduction. To find out the optimum amount of Mg to reduce SiO, various amount of Mg has been investigated. The ICE was gradually increased with the amount of Mg increased. The electrochemical performance was tested by cyclic voltammetry (CV) and discharge-charge measurement. The results show the sample prepared at 85% (mole) of Mg exhibited the larger storage capacity of 1656.47 mAh g-1 and outstanding high initial Coulombic efficiency of 83.09%, and better cyclic property as compare to Bare SiO.

[1] M. Armand and J.-M. Tarascon, “Building better batteries,” Nature, vol. 451, p. 652, Feb. 2008.

[2] N. Lin et al., “A low temperature molten salt process for aluminothermic reduction of silicon oxides to crystalline Si for Li-ion batteries,” Energy Environ. Sci., vol. 8, no. 11, pp. 3187–3191, 2015.

[3] Y. Zhang et al., “An affordable manufacturing method to boost the initial Coulombic efficiency of disproportionated SiO lithium-ion battery anodes,” J. Power Sources, vol. 426, pp. 116–123, 2019.

[4] Y. Lai, J. R. Thompson, and M. Dasog, “Metallothermic Reduction of Silica Nanoparticles to Porous Silicon for Drug Delivery Using New and Existing Reductants,” Chem. Eur. J., vol. 24, no. 31, pp. 7913–7920, 2018.
Bismuth Sulfide-Carbon Nanotube Composite As a High Capacity Anode for K-Ion Batteries
Authors: Hwang Jang-Yeon , Sun Yang-Kook
Published: December 2020

K-ion batteries (KIBs) have attracted attention as a promising alternative to commercial Li-ion batteries (LIBs) because of their low cost, earth abundance, and low redox potential (Li: -3.04 V and K: -2.93 V vs. standard hydrogen electrode), along with the similar chemical properties between K and Li. [1] KIBs also possess an electrical energy storage mechanism similar to LIBs, which has accelerated the development of KIBs.[2] To date, alloys of group 14 or 15 elements in the periodic table, as defined by their corresponding alloying reactions, have been considered as potential candidates for high-capacity anodes in KIBs.[3] In the previously reported LIB and sodium-ion battery (SIB) system, bismuth sulfide (Bi2S3) was considered a potential electrode material for high capacity and low-cost electrode materials; however, their development is still infancy. In addition, to the best of our knowledge, K-storage capability in Bi2S3 has not yet been reported.

In this presentation, we synthesize nanostructured Bi2S3 carbon nanotube (CNT) composites and investigate their possible electrochemical K-ion storage behaviors in KIBs for the first time. [4] A combination of experimental and first-principles calculations was used to investigate the overall K-storage mechanism of Bi2S3. The CNT matrix in this composite anode not only provides electronic conductivity but also decreases the absolute stress/strain, and accommodates a period of large volume changes during the potassiation–depotassiation process. Compared to Bi2S3, the Bi2S3-CNT composite electrode delivered much higher discharge–charge capacity of and 750 mA h g-1 and good cycling stability. It should be noted that the CNT encapsulants provided a strong buffer effect that mitigated the large volume changes and pulverizations of Bi2S3 particles upon cycling, and enabled more efficient electronic conduction of the whole electrode during cycling. The XRD, SEM, TEM and EIS results clearly demonstrate the superior structural stability of the Bi2S3-CNT composite and its enhanced electrochemical K-storage performance.

Reference
s
:

[1] J.-Y. Hwang, S.-T. Myung, Y.-K. Sun, Adv. Funct. Mater., 2 (2018) 182938.

[2] K. Kubota, M. Dahbi, T. Hosaka, H. Kumakura, S. Komaba, Chem. Rec., 18 (2018) 459-479.

[3] W. Zhang, W. K. Pang, V. Sencadas and Z. Guo, Joule, 2 (2018) 1534-1547.

[4] J.-Y. Hwang, R. Kumar, H. M. Kim, M. H. Alfaruqi, J. Kim, Y.-K. Sun, RSC Adv., 10 (2020) 6536–6539.