bluuebunny/crossref_metadata_2025_split huggingface dataset:
Integration of Photodefinable Polybenzoxazole as Intermetal Dielectric for GaAs HBT Technology
Authors: Yota Jiro , Do Benny 
Published: February 2020

Polybenzoxazole (PBO) is a polymer dielectric that has excellent mechanical, physical, and electrical characteristics and that is used for various semiconductor thin film applications. The PBO has low dielectric constant, and has good thermal stability and thermo-oxidative resistance. Furthermore, the PBO material can be applied by spin-coating and can be cured at temperature of <300oC, which is significantly lower than many other spin-on dielectric materials. These characteristics make PBO suitable for use in many semiconductor technologies and applications that require the processing temperatures not to exceed 300oC, such as GaAs hetero-junction bipolar transistor (HBT) technology. The PBO material is easily processed, and can be made photodefinable by adding photoactive compounds, and therefore be patterned on semiconductor wafers. By using a photodefinable PBO dielectric material, there will not be any need to perform patterning by dry-etch process steps that are typically performed in GaAs technologies.
In this study, photodefinable PBO has been integrated as intermetal dielectric in GaAs HBT technology. Process module optimization and integration studies were performed and the PBO results and process flow were compared to those of dry-etch polyimide, which is typically used as intermetal dielectric in GaAs technology. The photodefinable PBO is shown to allow the intermetal dielectric process flow to be simplified and the number of processes and equipments to be reduced. Results show that PBO has more planarity than polyimide, when coated on GaAs HBT wafers, which typically have significant topography. The PBO photolithography coat, expose, and develop processes were optimized in order to obtain the desired dielectric thickness and the required via dimension and sidewall profile, in addition to removing the PBO from the die street. The PBO thermal curing process was performed at 300oC, while ashing was performed to remove any PBO residue in the vias and streets. Figure 1 shows the FIB/SEM images of GaAs wafer after deposition of Metal 1 and coated with photodefinable, after via expose and develop, after cure, and after ash. Figure 2 shows the GaAs HBT wafer with (a) dry-etch polyimide and (b) photodefinable PBO used as intermetal dielectric. These results show that the photodefinable PBO film is compatible with, is suitable for, and can be integrated as intermetal dielectric in GaAs HBT technology.
New Approaches to Realizing High Power Nitride Based Field Effect Transistors
Authors: Shur Michael , Simin Grigory , Gaska Remis 
Published: February 2020

High breakdown voltage, excellent current carrying capabilities, high electron saturation velocity, high mobility, good thermal properties, chemical inertness, and radiation hardness of nitride semiconductors make them uniquely suited for high power applications. However, new approaches are needed to achieve their full potential. We report on several key innovations that include (1) the use of Perforated Channel (PC) design (to control and minimize the parasitic and on resistances and off and on transistor capacitances for faster switching and sharply reduced losses); (2) surface application of Low Conducting Layers (LCLs) (to control the properties and stability of ungated surfaces and dramatically increase the breakdown voltage); (3) the combination of these two approaches (for achieving the ultimate power performance at the highest switching frequencies with minimum losses); (4) novel device geometries (combining the best features of lateral and vertical devices for normally-off transistors with unprecedented power handling capability); (5) improved control of self-heating and better heat dissipation using the PC channel design. We also review our recent results exploring the PC channel and LCL designs [1-3]. These experimental and simulation results demonstrated a sharp increase in the breakdown voltage, a large enhancement of the cutoff frequency, a better device stability and smaller spreading of the device parameters for higher yield, improved manufacturability, and smaller self-heating due to a lower thermal impedance.
[[1]] G. Simin, M. Islam, M. Gaevski, J. Deng, R. Gaska, and M. Shur, “Low RC-constant Perforated-Channel HFET”, IEEE Electron Device Letters, 35 (2014)
[2] M. Gaevski, Jianyu Deng, A. Dobrinsky, R. Gaska, M. Shur, and G. Simin, Static and transient characteristics of GaN power HFETs with low-conducting coating, physica status solidi, Article first published online: 24 MAR 2014 | DOI: 10.1002/pssc.201300541
[3] G Simin, M Shur, R Gaska, Semiconductor device with low-conducting buried and/or surface layers - US Patent Application 20,130,126,905 (2013)
III-V Nanowire MOSFETs in RF-Applications
Authors: Wernersson Lars-Erik 
Published: February 2020

III-V MOSFETs are currently being considered for logic applications with the aim to increase the drive current at reduced power consumption. The benefits of the III-V material include a high injection velocity and the possibility to operate close to the ballistic limit, whereas the cylindrical geometry provides electrostatic control. The devices may also find RF-applications that will require studies of further metrics like the on-resistance, the output conductance, and the voltage gain. For device applications it is essential to consider the complete transistor architecture to optimize the layout and to minimize parasitic elements.
In this talk, we will discuss the possibilities and benefits of using III-V Nanowire MOSFETs in RF-applications. In particular we will demonstrate:

Integration III-V nanowires on 4” Si substrates

Interface characterization of the III-V/High-k surface

Design of transistor architectures at scaled gate lengths

RF-performance for 200 nm Lg devices

Strategies to integrate p-type devices

Operation of InAs MOSFET RF down-conversion mixers on Si substrates
Structural and Optical Properties of Phase Change Material in Sb2Te3 Thin Film
Authors: Choi Hyejin , Jung Seonghoon , Kim Taehyeon , Park Jaehun , Jeong KwangHo , Cho Mann-Ho 
Published: February 2020

Chalcogenide based compound, especially Sb2Te3 and related compounds, exhibit pronounced structural and optical contrast with rapid phase transition from amorphous and crystalline phase. This makes them suitable candidates for rewritable optical storage media and phase change random access memory. Simultaneously, Sb2Te3 have reported that one of the best p-type thermoelectric materials characteristics at room temperature, and topological insulators property. As electron and phonon plays a crucial role in determining the performances of any real devices, a better understanding of the amorphous phase and crystal phase, and the transition mechanism between them, is imperative. Recent, Optical pump THz probe spectroscopy (OPTP) is a powerful tool to study the ultrafast carrier dynamics of structural phase transition occurring on ultrafast time scales, as has been applied to a variety of materials, such as semimetal and semiconductor, and Mott insulators examined by using a femtosecond pump-probe technique and found that the appearance of the coherent vibrational modes was significantly modified upon the phase change.
In this study, we investigate ultrafast carrier dynamics in {Sb(3)Te(9)}n thin film that the phase change from amorphous into crystalline states can be explained by THz-TDS and OPTP, which is the relationship between structural phase transition and optical properties transition in THz range. We observed that OPTP spectroscopy was closely dependent on phase of the Sb2Te3 film, indicating that decay time is a crucial carrier dynamics mechanism to the phase transformation process.
Comparative Study on the Solid Electrolyte Interface Formation by the Reduction of Alkyl Carbonates in Lithium Ion Battery
Authors: Haregewoin Atetegeb Meazah , Leggesse Ermias Girma , Hwang Bing-Joe , Jiang Jyh-Chiang , Wang Fu-Ming , Lin Shawn D. 
Published: February 2020

One of the major concerns in lithium ion battery is the composition of the electrolytes as it governs some of the vital physicochemical properties of the electrolytes such as viscosity, ionic conductivity, thermal stability and wettability. Most important properties of lithium ion batteries are related to the properties of the solid electrolyte interface (SEI) layer formed on the electrode surface. The SEI in turn is mainly dependent on the electrolyte composition [1]. Therefore, understanding the nature, mechanism and property of the SEI formation in different electrolyte composition is crucial in selecting electrolytes. In this work, we report a direct comparison of the reduction of propylene carbonate (PC), ethylene carbonate (EC) and diethyl carbonate (DEC) as a single, binary and ternary solvent systems. Battery performance test, cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and scanning electron microscope (SEM) is employed to study the nature of the surface films formed.
The reduction products are determined by using ex-situ attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), in the glove box, after employing linear sweep voltammetry (LSV) to certain potential regions. EC/PC/DEC based electrolyte shows better capacity retention and less impedance than the EC/PC system. In all systems, the FTIR results indicate the formation of (CH3CH2OCO2Li)2 and Li2CO3 due to the reduction of PC. EC is reduced to (CH2OCO2Li)2 and Li2CO3 in both the binary and ternary solvent system. The FTIR result at the potential where DEC reduction occurs shows the formation of (CH2=CH-OCO2CH2CH3)Li which is less stable and forms a less-passivating layer in the first cycle. However, this product can further react with another species in the subsequent cycles and form a stable SEI.
[1] A.J. Gmitter, J. Gural, G.G. Amatucci, J. Power Sources, 217 (2012) 21-28.
[2] K. Xu, J. Electrochem. Soc., 156 (2009) A751-A755.
[3] G.V. Zhuang, H. Yang, B. Blizanac, P.N. Ross, Electrochem. Solid-State Lett, 8 (2005) A441-A445.
Heat Flow Measurement and Analysis during Lithium-Ion Battery Formation Process
Authors: Xu Jeff Qiang , Sarlashkar Jayant V , Iyengar Vikram , Argo Mickey 
Published: February 2020

An important step often overlooked or rarely investigated in lithium-ion battery manufacturing is the formation process. The formation process is the first full charging cycle of a lithium ion battery, which activates the cells before the lithium-ion cells can be used. The study focuses on using novel thermal measurement tool to monitor heat flow during the first charging/discharging cycle and its subsequent cycles of newly manufactured 18650 cylindrical cells. Thermal models and formulations were developed to identify the complexity of heat influence when three cells were tested simultaneously. A heat flow profile versus formation voltage window was discovered to provide important information to the study. Figure 1 shows a clear voltage window from 2.0 V to 3.7 V was identified to use as a reference range for designing alternative formation current rates. The formation process can then be altered to allow the preferential formation current rates to obtain the highest formation efficiency and improved cell performance. The impact of the lithium-ion battery formation process on battery performance such as capacity and cycle life were also examined in this study.
Figure 1: Heater Power Change as a Function of Cell Voltage during C/10 Formation Current Rate
Hybrid Solid Electrolyte Composed of Lithium Aluminum Germanium Phosphate and Poly(ethylene oxide) for All Solid-State Lithium Batteries
Authors: Jung Yun-Chae , Lee Sang-Min , Choi Jeong-Hee , Kim Dong-Won 
Published: February 2020

Lithium-ion batteries have rapidly become the dominant power sources for portable electronic devices and electric vehicles, due to their high energy density and long cycle life [1,2].However, safety issues still prevent full utilization of these batteries owing to the use of flammable liquid electrolytes, and safety problems have become a significant concern especially in large capacity applications such as electric vehicles and energy storage systems. In this respect, fabrication of all solid-state lithium batteries by using solid electrolytes may give a fundamental solution for the safety issue of lithium batteries [3,4]. Glass ceramic electrolytes present potential advantages, such as absence of electrolyte leakage, large electrochemical stability window, absence of problems relating to vaporization of organic solvents and high thermal stability. However, sheet manufacturing, especially using thin-film technologies for making large-scale batteries, is considered to be difficult because of hard and brittle ceramic materials. In this work, solvent-free hybrid solid electrolytes composed of lithium aluminum germanium phosphate and poly(ethylene oxide) (PEO) were prepared in the form of flexible film, and their electrochemical characteristics were investigated. Their morphological properties were examined using SEM, EDS and XRD. The ionic conductivities and electrochemical stability of hybrid solid electrolytes were much higher than those of PEO-based polymer electrolyte. The optimized hybrid solid electrolyte was applied to the solid-state Li/LiFePO4 cell, and its electrochemical performance was evaluated.

References

1. J.M.Tarascon, M.Armand, Nature, 414, 359 (2001).
2. P.G.Bruce, B.Scrosati, J.M.Tarascon, Angew. Chem. Int. Ed, 47, 2930 (2008).
3. N.Kamaya, K.Homma, Y.Yamakawa, M.Hirayama, R.Kanno, M.Yonemura, T.Kamiyama, Y.Kato, S.Hama, K.Kawamoto, A.Mitsui, Nat. Mater, 10, 682 (2011).
4. Y.Li, J.B.Goodenough, Electrochem. Commun., 13, 1289 (2011).
Production of Silicon Particles for High-Capacity Anode Material Yielding Outstanding Production Capacity
Authors: Andersen Hanne Flåten , Mæhlen Jan Petter , Klette Hallgeir , Ulvestad Asbjørn , Filtvedt Werner , Kirkengen Martin , Mongstad Trygve Tveiterås , Vie Preben J. S. , Holt Arve 
Published: February 2020

Silicon is proven to have a great potential as an anode material in lithium-ion batteries due to its high theoretical electrochemical capacity. The standard, commercial graphite anode has a theoretical capacity of less than 400 mAh/g, whereas the silicon anode can potentially deliver a tenfold capacity as a result of multiple Li-ion incorporation in the structure. However, silicon anodes deteriorate quickly during cyclic charging and discharging, rendering them useless in only a few cycles. This has been attributed to stresses induced by the large volume change of the material during cycling. The methods explored in order to overcome these problems such as using lithography, advanced nanotechnology, incorporation of silicon in carbon nanotubes or similar methods are too slow and too expensive for commercial use.
This work presents results from using a silane-based decomposition reactor in order to produce silicon particles with a suitable nanostructure for use in lithium-ion battery anodes. The silane gas is decomposed in a controlled environment at a temperature of 500-600 °C. The current pilot reactor has demonstrated production of up to 350 g/hour in an easily up-scalable lab version. Particles of diameter ranging from 50 nm and up to 500 nm have been produced with relatively narrow size distribution. This method may produce both amorphous and crystalline particles and the surface of the particles can be terminated by hydrogen or other elements if desired.
The silicon particles were mixed with an organic binder in an aqueous slurry and coated on a Cu-foil, The electrochemical performance was tested with CR-2032 coin cells. In the course of the presented work studies of cyclic voltammetry, cycling stability (Figure 1), voltage profiles and electrochemical impedance were performed. Besides electrochemical methods, SEM (Figure 2), XRD, ICP-MS and particle size distribution measurements were implemented. The silicon particles achieved a high capacity, relatively good stability, as well as a high yield and production capacity. Further developments on the silicon particles, such as doping of Si and in-line surface coating, are feasible.
Invited Presentation: Striving Toward an Ultrahigh Energy Density Li-Air Battery
Authors: Abraham K.M. 
Published: February 2020

In the pursuit to develop a practical rechargeable Li/air battery, we have studied the mechanisms of O2 reduction and evolution reactions (ORR and OER), and the nature of the products formed, in a series of organic electrolytes and ionic liquids. The distinct ORR products formed in these disparate electrolyte solutions can be explained using a general theory based on the Hard Soft Acid Base (HSAB) concept. We have found that the electron donor property of the solvent modulates Li+ acidity in organic electrolytes , through the formation of complexes (or solvates) of the formula Li(solvent)n
+ where, n = 2-4, and these solvates in turn influence the mechanisms and products of both catalyzed and uncatalyzed ORR in Li-air batteries. A cobalt phthalocyanine-derived catalyst has enabled the full reduction of O2 to Li2O in selected solvents, and provided improved rechargeability for Li-air cells.
Acknowledgment: The US Army US Army RDECOM CERDEC C2D, Aberdeen Proving Grounds, MD, provided financial support for this work

Dr. K. M. Abraham is Professor at Northeastern University Center for Renewable Energy Technology, Boston, Massachusetts, USA. KM has made many pioneering contributions to advance primary and secondary lithium and Li-ion batteries including the invention of the lithium-air battery.
Invited Presentation: Lithium Metal Anode: Challenges and Opportunities
Authors: Zaghib Karim 
Published: February 2020

Research on lithium metal combined with polymer electrolyte in lithium rechargeable batteries was started in 1979. Since that time, battery research has expanded worldwide. Several new polymers, solid electrolytes and ionic liquids with improved conductivity were identified. These advances resulted from a better understanding of the major parameters controlling ion migration, such as favorable polymer structure, phase diagram between solvating polymer and lithium salt, and the development of new lithium counter-anions. In spite of the progress so far, the quest for a highly conductive dry polymer at room temperature is still not available. However, effort is continuing, and all-lithium polymer battery (LPB) developers presently face the challenge of whether to heat the polymer electrolyte to enable high-power performance, as required for electric vehicle and energy storage. LPB developers have explored both the high-temperature and low-temperature options.
This presentation discusses the challenges and opportunities in developing thin lithium metal with stable SEI as negative electrode for three battery technologies using:
1. Batteries made from dry polymer and ionic liquid-polymer electrolytes for
rechargeable lithium batteries
2. All solid-state Li-sulfur batteries
3. Li-air batteries.
In addition, we will discuss the safety of lithium, dendrite mechanism, interface phenomena, side reactions, protection of lithium metal, and lithium alloys.
Electrochemical Characterization of Li1.07V0.83Fe0.1O2 ANODE Material for Li-ION Batteries
Authors: Gędziorowski Bartłomiej , Molenda Janina 
Published: February 2020

INTRODUCTION

Recently a novel compounds based on layered LiV1-yMyO2 (M = Li, Fe, Cr) were found to be promising anode materials for Li-ion technology [1-3], as they exhibit long low-voltage plateau vs. metallic lithium, and higher volumetric capacity than commonly used graphite-based anode materials.
This work presents synthesis and evaluation of electrochemical properties of Li1.07V0.83Fe0.1O2, in particular open circuit voltage (OCV) and XRD analysis at different discharge (lithium content) stages.

EXPERIMENTAL

Li1.07V0.83Fe0.1O2 was synthesized using a high-temperature solid-state reaction method with Li2CO3, V2O3 and Fe2O3 taken as substrates. Stoichiometric amounts of reactants were milled in a high efficiency mill. Obtained powder was pressed into pellets and sintered in two steps: 1) at 800 °C for 10 h in Ar and 2) at 1050 °C for 12 h in 5 vol.% of H2 in Ar, followed by quenching.
Structural studies were performed in 10-110° range with CuKα radiation using Panalytical Empyrean diffractometer, followed by Rietveld refinement of identified structures.
Electrical conductivity was measured using 4-probe AC technique in -60°C to 70°C temperature range.
Electrochemical studies were done in Li/Li+/ Li1.07V0.83Fe0.1O2 cells constructed using CR2032-type containers. 1M solution of LiPF6in EC/DEC (in 1:1 ratio) was used as the electrolyte. For the positive electrode powder of active material was used (mass ≈ 50mg). OCV values were assumed as voltages of batteries after discharging to designated compositions followed by at least 24 h of relaxation.

RESULTS AND DISCUSSION

XRD analysis shown that the material is single phase and exhibits layered R-3m α-NaFeO2 type structure.
Electrical conductivity values are almost two order of magnitude higher than for materials with no iron substitution.
Discharge characteristics upon load shown step-like character, distinctly different than in Li1.07V0.93O2with shorter and right-shifted low voltage plateau.

ACKNOWLEDGMENT

This work was supported by NCN grant no. NCN 2011/02/A/ST5/00447.

REFERENCES

[1] A. R. Armstrong, C. Lyness, P. M. Panchmatia, M. S. Islam, P. G. Bruce, Nature Mater. 10
(2011) 223-229
[2] W.-T. Kim, Y. U. Jeong, H. C. Choi, Y. J. Lee, Y. J. Kim, J. H. Song, J. Power Sources 221
(2013) 366-371.
[3] X. Ma, G. Hautier, A. Jain, R. Doe, G. Ceder, J. Electrochem. Soc., 160 (2013) A279-A284.