bluuebunny/crossref_metadata_2025_split huggingface dataset:
Contact Resistivity of Highly Doped Si:P, Si:As, and Si:P:As Epi Layers for Source/Drain Epitaxy
Authors: Rosseel Erik , Porret Clement , Hikavyy Andriy Yakovitch , Loo Roger , Tirrito Matteo , Douhard Bastien , Richard Olivier , Horiguchi Naoto , Khazaka Rami 
Published: December 2020

With the downscaling of the CMOS transistor dimensions, the reduction of the external resistance is playing an important role in the overall device optimization. For NMOS devices, highly P-doped Si:P epitaxy is typically used to lower the source/drain and contact resistance [1]. In this work we report on the use of As as a dopant and compare the layer characteristics and contact resistivity of highly doped epitaxial Si:P, Si:As, Si:P:As layers and Si:As/Si:P bi-layers grown on 300 mm Si (100) substrates. As is found to incorporate more efficiently into the epi layer compared to P but gives rise to a lower tensile strain [2]. Good quality epitaxial layers can be obtained with As concentrations as high as 10% (Fig. 1). In comparison to Si:P a reduced diffusion is confirmed for Si:As after spike and laser anneal, making the layer an interesting candidate for an extension liner [2,3]. In general, the dopant activation and carrier mobility of the Si:As and Si:P:As layers after epitaxy is lower than that of Si:P as determined by micro-Hall measurements (Fig. 2a). Only in some specific cases (e.g. for concentrations below ~3% and non-selective processes), we can observe an enhanced activation due to the co-doping of P and As which we attribute to an energetically favorable AsxV vacancy complex formation at low As concentration [4]. The contact resistivity was extracted using a Multi-Ring Circular Transmission Line Model for a Ti based contacting scheme [5]. The contact resistivity of Si:P, Si:As and Si:P:As layers with different concentrations obtained by selective and non-selective epitaxy was compared and the effect of a post-epitaxy millisecond laser anneal was studied (Fig. 2b). Excellent contact resistivities down to ~2E-9 Ohm.cm2 could be found at high doping levels. A clear correlation was observed between the resistivity/contact resistivity and activation levels obtained by micro-Hall measurements. Within the set of studied processes, As doping is not bringing substantially lower contact resistivities compared to P doping, for comparable chemical doping concentrations. Still, As remains an attractive dopant for extension liners because of its lower diffusion constant.

References

[1] E. Rosseel et al., ECS Trans. 75(8), pp.347-359 (2016).
[2] E. Rosseel et al., ECS Trans. 93(1), pp. 11-15 (2019).
[3] S. Mochizuki et al.,IEEE Int. Electron Devices Meeting 2018, p. 811 (2019).
[4] N. Nakazaki et al., EMRS 2019 B.IX.3
[5] H. Yu et al., IEEE Electron Device Letters, 36(6), pp. 600-602 (2015).

Figure 1
(Invited) Stacking Faults in 3C-SiC: From the Crystal Structure, to the Electrical Behavior
Authors: La Via Francesco , Zimbone Massimo , Scuderi Viviana , Calabretta Cristiano , Bongiorno Corrado , Giannazzo Filippo , Fiorenza Patrick , Muoio Annamaria 
Published: December 2020

Many attractive mechanical and electrical properties make silicon carbide (SiC) a material of interest in both electronic devices and sensors for nowadays technology (sustainable energies, hybrid vehicles, low power loss inverters). Silicon carbide exists in nature in several crystalline structures, called polytypes, differentiated by the stacking sequence of the tetrahedrially bonded Si-C bilayers. The only possible cubic structure, 3C-SiC, is obtained when the bilayer stacking is of the kind ABCABC..., resulting in a pure zinc-blende structure. 3C-SiC growth on Si is allowed within chemical vapour deposition (CVD) reactors, which would ensure a very high purity of the resulting product. The interface between 3C-SiC and Si is the origin of a high density of planar and volume defects, such as microtwins, anti-phase boundaries and stacking faults in the epilayer and voids in Si underneath the hetero-interface. Most of these defects, considered killers for devices, however, reduce their density, and some are totally annihilated, when very thick (several tens of microns) 3C-SiC epitaxial films are realized. The main defects that remain also after the growth of several tens of microns are the Stacking Faults (SFs). Three main SFs have been observed in 3C-SiC: the intrinsic one where only one plane is shifted with respect to the lattice position and two extrinsic SFs where two or three layers are shifted. In these last cases we observe locally the same crystallographic structure of the hexagonal polytypes: 4H-SiC and 6H-SiC. In the last period a large investigation has been done on these defects to see the crystallographic structure of these defects, the interactions between different SFs, the influence of the SFs on the internal stress of the material, the effects of several growth parameters (temperature, doping, growth rate, ...) on the density and evolution of these defects. Finally also several local electrical measurements by C-AFM has been done to understand the effect of these defects on the electrical behaviour of the devices.
In Fig. 1 a three different HRTEM images of three different SFs are reported. It is possible to observe the different crystallographic structure of these defects. In Fig. 2 the interaction between these defects is reported. It is possible to observe that the SFs can annihilate or generate or close. The growth parameters have a large influence on the evolution of these defects. In Fig. 3 can be observed that, decreasing the growth rate and the growth temperature, the SFs density decreases. In Fig. 4 it is reported the effect of the doping on the SFs. Increasing the nitrogen concentration the SFs density decreases and the average length increases.
At the conference more details on the SFs structure, the effect of these defects on the stress and on the electrical characteristics of the devices will be given.

Figure 1
Thermal Silicidation of Ni/SiGe and Characterization of Resulting Silicide Films Using Raman Spectroscopy and X-ray Diffraction
Authors: Yoo Woo Sik , Kang Kitaek , Ishigaki Toshikazu , Kim Jung Gon , Hasuike Noriyuki , Harima Hiroshi , Yoshimoto Masahiro 
Published: December 2020

For advanced application specific devices, combinations of Si/Ge, Ge/Si, Si1-xGex/Si are frequently introduced in the device fabrication process. Epitaxy, condensation and annealing processes are commonly used for controlling the Ge content to a desired level. Strain and crystallinity can be affected by a small variation in composition or Ge content, which can result in device performance deterioration or failure. Thus, the composition, strain and crystallinity must be carefully monitored and controlled throughout the manufacturing process. The electrode formation process is also very critical for successful device fabrication. Any spikes and/or electrically active defects near junctions can be fatal to the device yield. Silicidation processes and resulting silicides must be investigated as much as possible using various non-invasive material characterization techniques.
In this study, we report the thermal silicidation characteristics of Ni/Si1-xGex with various Ge content under different annealing temperatures in the range of 225oC ~ 400oC in N2 ambient. Thermal silicidation was performed in a stacked hotplate-based SAO-302LP system designed for 300mm wafers. For resulting silicide characterization, measurements of sheet resistance, Raman spectra, X-ray diffraction curves as well as scanning electron microscopy (SEM) observations were performed. We have studied Ge content and annealing temperature dependence on the resulting electrical and crystallographic silicide characteristics.
Figure 1 shows 647nm excited Raman spectra and X-ray diffraction (XRD) curves from reference Si, and resulting silicide from Ni/Si0.75Ge0.25 before and after annealing under at 235oC, 310oC and 400oC.
Raman spectra and sheet resistance measurements showed silicide formation and silicide layer thickening with increasing annealing temperature. XRD curves clearly indicated the change of crystalline phase of resulting silicide with annealing temperature increase. Various aspects of thermal silicidation and its characterization will be discussed at the conference.

Figure 1
Rationally Designed 3D Graphene Hollow Spheres Towards Building High Energy – High Power Energy Storage System with Long Durability
Authors: Thangavel Ranjith , Oh Woong , Jeong Mihee , Yun Soyeong , Choi Munhyeok , Lee Yun-Sung , Yoon Won-Sub 
Published: December 2020

Functional materials with high energy density – high rate capabilities have continued to gain importance, and are extensively studied for next-generation energy storage applications.[1] The ongoing challenge is to elevate the power density of batteries on par with capacitors, while holding the energy density and cycle life.[2] The sluggish intercalation kinetics, and continuous transition metal dissolution in conventional electrodes hampers the realization of high power, and highly stable devices.[3] To overcome the kinetic issues, we rationally designed graphene hollow nanospheres (GHNS) with dual heteroatoms (nitrogen and sulfur) as both anode and cathode for Na-ion based energy storage system. The self-assembly of 2D graphene into a highly connected 3D architecture facilitates facile Na-ion storage, while the nitrogen and sulfur hetero atoms infiltrated in the carbonaceous matrix elevates the kinetics of the GHNS. The full-cell based on GHNS electrodes displays a high operating voltage, high energy density (121 Wh kg−1 at 100 W kg−1), and high power density (51 kW kg-1). Further, the sodium-ion storage system can render remarkable cycling stability of ~85% retention after 10,000 cycles (~0.0015% decay per cycle). Development of such nanostructured functional materials could establish a trade‐off relationship between high energy and high power devices.
References
[1] J. R. Miller, P. Simon, Science 2008, 321, 651.
[2] H. Jiang, P. S. Lee, C. Li, Energy Environ. Sci. 2013, 6, 41.
[3] R. Thangavel, B. Moorthy, D.K. Kim, Y.-S. Lee, Adv. Energy Mater. 2017, 7, 1602654.
Observation of an Unidentified Phonon Peak in SiGe Alloys and Superlattices Using Molecular Dynamics Simulation
Authors: Chung Sylvia Yuk Yee , Tomita Motohiro , Yokogawa Ryo , Ogura Atsushi , Watanabe Takanobu 
Published: December 2020

Advancements in semiconductor technology coincide with an increasing need for better understanding of thermal transport and phonon behaviour in such devices. The difficulty lies with observing and measuring these phonon properties, oftentimes proving to be a challenge due to the limitations posed by instrumental capabilities. Yokogawa et al [1] obtained inelastic X-ray scattering results for SiGe alloys, and found an unidentified phonon mode (~ 50 – 150 cm-1) within the phonon spectra. Determining the possible conditions for producing this unknown mode drove the motivation for this current study and thus, forms the theme for this project.
A variety of SiGe structures consisting of alloys, a compound and superlattices, were simulated using molecular dynamics to obtain the phonon dispersion relations in order to observe the unknown mode. All of the SiGe alloys produced the unknown mode, but the SiGe compound did not. The alloys are configured with a random atomic configuration, but the SiGe compound is given an Si-Ge-Si-Ge atomic configuration, indicating that the unknown mode has a tendency to only show for structures of an alloy nature. Regarding the superlattices, structures consisting of periodic layer widths did not produce the unknown mode, whereas aperiodic structures did. This tendency increased as the layer widths reduced.
The origin of this unknown mode is still yet to be determined, but what we can conclude so far, is that this mode will only appear when the structure adopts a random atomic configuration, with a preference leaning away from periodicity.

Acknowledgements

This work was supported by a CREST grant (JPMJCR19Q5) from the Japan Science and Technology Agency (JST).

References

[1] R. Yokogawa, Oyanagi, H. Uchiyama, S.Tsutsui, I. Yonenaga, A. Ogura, Phonon Dispersion Measurements for Bulk Si1-xGex (x=0.72) Crystal by Inelastic X-ray Scattering, The 80th JSAP Autumn Meeting, Hokkaido Univ. Japan, 19/09/2019

Figure 1
Solution-Phase Synthesis and Electrochemical Properties of Lepidocrocite Titanate-Reduced Graphene Oxide Composites
Authors: Barim Gözde , Lin Jason , Doeff Marca M 
Published: December 2020

Stepped layered titanates can be used as anodes for lithium, sodium or potassium batteries in conventional or flow cell configurations. They are attractive due to their low cost, low toxicity, and high abundancy. However, their low conductivity and poor cycling performance are major hurdles for these materials.The addition of carbon can be used to overcome electronic transport limitations to some extent, but for nonconventional configurations, it is preferable to build in the conductivity by manipulating the structure. For example, in the case of layered materials, this can be done by incorporating a conductive component such as reduced graphene oxide (rGO) in the van der Waals gaps to make 2D heterostructures, the approach we are using here.
In this presentation, solution-phase synthesis of K0.8[Ti1.73Li0.27]O4 (lepidocrocite titanate, LT)- rGO composite is demonstrated. After synthesis by conventional solid-state routes, K0.8[Ti1.73Li0.27]O4 is proton exchanged and ion-exchanged with bulky cations, causing expansion of the structure, and exfoliated by mechanical shaking. Exfoliated layered titania sheets are combined with reduced graphene oxide (rGO) to assemble into heterostructures through flocculation. Counter cations (e.g. Mg2+, Na+) are used for the self-assembly of negatively charged LT and rGO nanosheets via flocculation. Mg2+-coagulated composites with 15 wt% rGO have higher capacities than Na+-coagulated composites with the same rGO content in the lithium half-cell configurations, whereas Na+-coagulated composites deliver higher capacity than that of Mg2+-coagulated composites in the sodium half-cell configurations. Both Mg2+-coagulated and Na+-coagulated LT-rGO samples exhibit capacities which are more than two times higher than the capacities of pristine lepidocrocite titanate (K0.8[Ti1.73Li0.27]O4), and display good capacity retention after 50 cycles in both lithium and sodium half-cells configurations.
Enhanced Cathode Reactions of the Solid-State Li-Air Battery By Operating Under Humidified Atmosphere
Authors: Kim Mokwon , Ma Sang Bok , Kwon Hyuk Jae , Lee Hyunpyo , Park Jung Ock , Im Dongmin 
Published: December 2020

Lithium-air (Li-air) battery has been considered to be a promising next-generation energy storage system owing to its high theoretical specific energy of 3,458 Wh/kg. Despite the progresses that have been made to improve the cell performance and reaction kinetics of Li-air battery, achieving its sustained reversibility still remains as a highly challenging goal because of the use of liquid electrolyte and carbonaceous materials in the cathode. These components could easily decompose by side reactions against highly oxidative radicals during cycling, leading to a poor cycle life of the cell. To address this instability issue, stable all-solid-state cathode has attracted research attention in accordance with the recent development of oxide-based solid electrolytes. Although a few meaningful approaches to demonstrate oxide-based solid-state cathodes have been reported, such cells were operated under pure oxygen atmosphere (Li-O2 battery), resulting in limited active interfaces for oxygen redox reactions and low specific capacity to the total weight of the cathode structure.
Herein, we report the enhanced cathode reactions for Li-air battery by operating under humidified oxygen atmosphere to overcome the limitation of conventional oxide-based solid-state Li-O2 battery. For the cathode, a novel solid-state composite cathode structure consists of ruthenium-based oxide nanoparticles without any carbonaceous additives was prepared to catalyze the oxygen redox reactions. During cycling, the vaporized water molecules could significantly increase the discharge potential, discharge rates, and round-trip efficiency of the cathode. The morphological and structural analysis of the discharge products formed via water-involved reactions inside the pore structure, not only at the interfaces, were also conducted to figure out the effects of humidification. The resulting solid-state Li-air battery showed a superior cycle life with the high specific capacity to the cathode compared to conventional solid-state Li-O2 batteries. The details of the cathode properties and cell performances will be discussed in the presentation.
Parasitic Reactions Due to Singlet Oxygen and Possible Approaches in Lithium-Oxygen Batteries
Authors: Kwak Won-Jin 
Published: December 2020

Irreversible parasitic reactions cause poor rechargeability and efficiency of Li-O2 batteries, and have predominantly been ascribed to the reaction of reduced oxygen species with cell components.
Recently, it was demonstrated that singlet oxygen (1O2) formed at the cathode during discharge and from the onset of charge accounts for the majority of parasitic reaction rather than reduced oxygen species.
In this presentation, I summarize the current knowledge about parasitic reactions of singlet oxygen in lithium-oxygen batteries and guide pathways to counteract this problem for reversible system.
(Invited) Ultrahigh Areal Capacity Holey Graphene Air Cathodes for Li-O2 and Li-CO2 Batteries
Authors: Lin Yi , Connell John W. 
Published: December 2020

Advanced lithium (Li) batteries using gaseous cathode reactants such as oxygen (O2) and carbon dioxide (CO2) are attractive energy storage platforms because the gases are obtained externally and thus not accounted for in the total battery weight when fully charged. The discharge products at the cathode, typically Li2O2 for Li-O2 batteries and Li2CO3for Li-CO2 batteries, are insoluble in the electrolyte. Therefore, in order for such batteries to function properly, an “air cathode”, which is a conductive scaffold within the battery cell, is required as a physical location for cathode electrochemical reactions to occur. Prior research has identified many carbon nanomaterials such as carbon nanotubes and graphene as viable choices for air cathode scaffold, while various metallic and metal-free catalytic systems integrated onto carbon-based air cathodes have been developed to improve the sluggish discharge and charge reactions. For future practical applications, the air cathode must exhibit a usable capacity per unit electrode area, or areal capacity, a critical parameter that has been largely overlooked so far in this field. In order to achieve high areal capacity, the air cathode must exhibit a sufficient amount of accessible void volume per unit electrode area while maintaining the conductive scaffold integrity during the entire electrochemical process.
Here we present an ultrathick, holey graphene-based air cathode platform fabricated from a facile dry compression process that exhibits remarkable areal capacity values. Holey graphene is a carbon nanomaterial derived from graphene, but with nanometer sized holes through the nanosheet thickness. The holes are generated in a controlled air oxidation process in which the defective carbon on the graphene surface are selectively oxidized and removed. The presence of these holes enhances mass transport through electrode thickness and also enables the unique dry-press fabrication process that is not achievable using other carbon scaffold materials. The dry-pressed holey graphene air cathode platform is compatible with catalyst incorporation to improve battery reaction kinetics. This platform also allows for novel engineering of electrode architectures not achievable using conventional electrode fabrication approaches. The applications of such highly versatile, ultrahigh areal capacity air cathode platforms to both Li-O2 and Li-CO2 battery chemistries will be discussed.
Implementing Low Temperature Strategies to Advance “Really Cool” Molten Sodium Batteries
Authors: Spoerke Erik D. , Gross Martha , Percival Stephen , Peretti Amanda , Lamb Joshua , Small Leo J. 
Published: December 2020

Though batteries for portable electronics and electric vehicles continue to advance at an impressive rate, the needs for safe, low-cost, reliable batteries suitable for large-scale implementation remain unsatisfied. Here, we describe advances toward a promising new class of low temperature molten sodium-halide batteries, capable of safe, reliable operation near 100oC, a dramatic reduction from the ~300oC operating temperatures common to traditional molten sodium batteries. While realizing this low temperature goal promises reduced system costs and improved material lifetimes, it introduces a host of new material performance challenges including molten catholyte phase control and electrochemistry, solid state separator performance, and charge transfer at critical solid-liquid interfaces. The new battery design described here relies on highly conductive NaSICON-based ion-conducting membranes to separate a molten sodium anode and, critically, a molten inorganic sodium iodide (NaI)-based halide salt catholyte. Through engineering of novel molten salt catholyte compositions, we have identified several chemistries capable of producing a high voltage (>3V) while avoiding problems of thermal runaway and electrolyte flammability. Our studies further show that catholyte composition not only impacts low temperature electrochemical performance, but also the accessible capacity and even techno-economic viability of the system. Implementing these catholytes in lab-scale prototypes with charge-transfer interfaces engineered for low-temperature operation, we have demonstrated 5 months of stable electrochemical cycling at 110oC. Continued refinement of these material-enabled strategies promises a new class of grid-scale energy storage technologies based on molten sodium.
Sandia National Laboratories is a multimission laboratory managed and operated by National Technology and Engineering Solutions of Sandia, LLC., a wholly owned subsidiary of Honeywell International, Inc., for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-NA0003525.