bluuebunny/crossref_metadata_2025_split huggingface dataset:
(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
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.
Fast and Reversible Four-Electron Storage Enabled By Ethyl Viologen for Rechargeable Magnesium Batteries
Authors: Sun Yue , Lu Yi-Chun 
Published: December 2020

Magnesium (Mg) batteries have been considered one of the most promising “post-lithium-ion” energy storage technologies owing to their high theoretical energy density, earth abundance, and intrinsic safety with air and moisture. However, the cell performance of Mg batteries has been limited to cathode materials leading to sluggish kinetics, low reversible energy density, and poor cycling stability. The development of Mg intercalation cathode materials[1–3] has been impeded by slow Mg2+ solid diffusion due to high charge density, sluggish charge redistribution, and strong electrostatic interaction with host and anions.[4] Many of the Li+-intercalation cathodes are not suitable for Mg2+ insertion.[5] Organic materials with high tunability have attracted significant attention,[6] but it has been challenging to achieve organic Mg batteries with a satisfactory energy density as the commercial lithium-ion battery (100-170 Wh kg-1
[7]) with high power and long cycle life. Here, a new organic cathode for rechargeable Mg batteries is reported based on ethyl viologen (EV), which not only has a fast redox couple EV2+/EV0 but also is capable of coupling with redox-active anions, such as iodide (I-), achieving a total four-electron storage. The EV2+/EV0 redox couple demonstrates a stable cycle life (500 cycles) with a superior rate performance (10 C) owing to intrinsic fast electrode kinetics, and a high material utilization (>80%) was achieved at 1.0 C under a high areal loading of 5 mg cm−2. When coupling with iodide I-, a reversible four-electron storage is achieved with a high energy density (304.2 Wh kg-1) and a stable cycle life (>100 cycles). This study provides effective strategies for designing reversible multielectron storage for high-rate and high-energy rechargeable Mg batteries.[8]

Reference
s
:

[1] X. Sun, P. Bonnick, V. Duffort, M. Liu, Z. Rong, K. A. Persson, G. Ceder, L. F. Nazar, Energy Environ. Sci. 9 (2016) 2273-2277.
[2] X. Sun, P. Bonnick, L. F. Nazar, ACS Energy Lett. 1 (2016) 297-301.
[3] B. Liu, T. Luo, G. Mu, X. Wang, D. Chen, G. Shen, ACS nano 7 (2013) 8051-8058.
[4] E. Levi, M. D. Levi, O. Chasid, D. Aurbach, J Electroceram. 22 (2009) 13-19.
[5] M. Bouroushian, Electrochemistry of metal chalcogenides, Springer Science & Business Media, Heidelberg, Berlin, 2010.
[6] M. Mao, T. Gao, S. Hou, C. Wang, Chem. Soc. Rev. 47 (2018) 8804-8841.
[7] J.-M. Tarascon, M. Armand, in: V. Dusastre (Ed.), Materials for Sustainable Energy: A Collection of Peer-Reviewed Research and Review Articles from Nature Publishing Group, World Scientific, Singapore, 2011, pp. 171–179.
[8] Y. Sun, Q. Zou, Y. Lu, Adv. Energy Mater. 9 (2019) 1903002.

Acknowledgements
:

This work was supported by a grant from the Research Grants Council (RGC) of the Hong Kong Administrative Region, China, under an RGC project No. T23-601/17-R.
Oxygen Reduction Pathways in the Li-O2 Battery: Understanding Solvent-Water Interactions
Authors: McNulty Rory , Holc Conrad , Walsh Darren Anthony , Rogers David , Newton Graham N. , Bruce Peter G. , Johnson Lee R 
Published: December 2020

Li-ion and related battery technologies will be important for years to come. However, society needs energy storage that exceeds the capacity of Li-ion batteries. We must explore alternatives to Li-ion if we are to have any hope of meeting the long-term requirements for energy storage. One such alternative technology is the Li-air (O2) battery; its theoretical specific energy exceeds that of Li-ion five-fold, but many obstacles face its realisation.1–4

It is assumed that H2O in the Li-O2 battery will result in irreversible formation of LiOH and thus gas streams must be dried before entering the battery. Projections have suggested that this would sacrifice one third of the pack weight to a gas filtration unit required to bring atmospheric H2O content to functional levels (<1 ppm).5–9 Understanding the specific solvent properties that are associated with H2O tolerance, or distinct lack of, can guide rational selection of solvents able to tolerate wet air streams and reduce the requirements of the gas filtration unit, increasing the practical energy density.
Here we consider competition between reversible 2e- O2 reduction and proton coupled irreversible 4e- O2 reduction. The predisposition to favour one of these O2 reduction pathways is largely solvent dependent. We have combined a range of methods including cyclic voltammetry, operando pressure analysis, NMR, FTIR, Raman, UV-vis spectroscopy and SEM to investigate the O2 reduction pathways in four common Li-air electrolytes containing H2O.10 H2O concentrations spanning 0–36% were employed to understand the onset and of the irreversible 4e- O2 reduction process across these solvents, with specific solvent properties being attributed to their performance. The results of these studies will be presented, along with their implications on rational future solvent development for rechargeable Li-O2 battery electrolytes.

Reference
s
:

[1] X. Gao, Y. Chen, L. Johnson and P. G. Bruce, Nat. Mater. 15 (2016) 882–888.
[2] N. Feng, P. He and H. Zhou, Adv. Energy Mater. 6 (2016) 1502303.
[3] L. Ma, T. Yu, E. Tzoganakis, K. Amine, T. Wu, Z. Chen and J. Lu, Adv. Energy Mater. 8 (2018) 1–13.
[4] D. Aurbach, B. D. McCloskey, L. F. Nazar and P. G. Bruce, Nat. Energy 1 (2016) 16128.
[5] K. G. Gallagher, S. Goebel, T. Greszler, M. Mathias, W. Oelerich, D. Eroglu and V. Srinivasan, Energy Environ. Sci. 7 (2014) 1555-1563.
[6] P. Tan, W. Shyy, T. S. Zhao, R. H. Zhang and X. B. Zhu, Appl. Energy 182 (2016) 569–575.
[7] C. Shu, J. Wang, J. Long, H. K. Liu and S. X. Dou, Adv. Mater. 31 (2019) 1–43.
[8] A. Dai, Q. Li, T. Liu, K. Amine and J. Lu, Adv. Mater. 31 (2018) 1805602.
[9] D. G. Kwabi, T. P. Batcho, S. Feng, L. Giordano, C. V. Thompson and Y. Shao-Horn, Phys. Chem. Chem. Phys., 18 (2016) 24944–24953.
[10] H. Guo, W. Luo, J. Chen, S. Chou, H. Liu and J. Wang, Adv. Sustain. Syst. 2 (2018) 1700183.