bluuebunny/crossref_metadata_2025 huggingface dataset:
Coupled Simulation of Electric Flight Dynamics and Physics Based Battery Model for Electric Aircraft Battery Pack Sizing Analysis
Authors: Kolluri Suryanarayana , Shah Krishna , Wang Mengyuan , Mesbahi Mehran , Subramanian Venkat R.
Published: July 2021

Electrification of aircraft and aviation systems is a thriving area of research and technology development in recent years1. According to the Airbus Global Market Forecast, air traffic will double every 15 years, leading to increasing fuel consumption causing severe impact due to greenhouse gases and carbon emission2. Besides the environmental impact, as the international demand for fuel increases, and the fact that petroleum resources are limited, fuel prices are projected to rise. On the other side, the drop in the cost of lithium ion batteries makes electric aircraft feasible to commercialize now. This necessitates studying the battery pack sizing problem to build efficient Energy Management System (EMS) for electric aircraft.

There is a significant amount of research on EMS for electric aircraft. Most of the current literature related to electric aircraft modeling considers the battery voltage to be linear3. This may lead to inaccurate estimation of state of charge (SOC), a key state variable for batteries and battery pack. In this work, we perform coupled simulation studies of the longitudinal flight dynamics and physics-based battery model (single particle model)4
,5. This coupling enables accurate estimation of battery pack state of charge. The simulation studies are performed to understand the interplay between battery pack configuration/design parameters and variables/parameters related to flight dynamics, such as altitude, distance, flight path angle, and velocity. We also compare the SOC prediction of the battery pack using single particle model and dynamic empirical battery model. This work will be extended to develop efficient and robust EMS for electric aircraft.

Acknowledgements

This research was supported by the Texas Materials Institute (TMI) at The University of Texas at Austin.

References

J. A. Rosero, J. A. Ortega, E. Aldabas, and L. Romeral, IEEE Aerosp. Electron. Syst. Mag., 22, 3–9 (2007).

Airbus global market forecase. [Online]., https://www.airbus.com/aircraft/market/global-market-forecast.html.

M. Kaptsov and L. Rodrigues, J. Guid. Control. Dyn., 41, 285–290 (2018).

S. Santhanagopalan, Q. Guo, P. Ramadass, and R. E. White, J. Power Sources, 156, 620–628 (2006).

V. Ramadesigan, P. W. C. Northrop, S. De, S. Santhanagopalan, R. D. Braatz, and V. R. Subramanian, J. Electrochem. Soc., 159, R31–R45 (2012).
The Importance of Li-Ion Nature and Stacking in Layered Cathode Materials for Aqueous Ion Batteries: From Bulk to Surface Models
Authors: Posada Perez Sergio , Rignanese Gian-Marco , Hautier Geoffroy
Published: July 2021

The performance of aqueous ion batteries has been demonstrated since the foundational work from Dahn et al. who combined an anode of VO2 and a cathode of LiMn2O4 in an aqueous electrolyte. The use of aqueous electrolytes opens the possibility of proton co-insertion, one of the common assumptions to explain performance issues in aqueous electrolytes. Experimental and computational works compared the feasibility of several cathode materials to be intercalated by H+ concluding likewise that non-layered cathode materials are less prone to proton intercalation than layered materials.

Therefore, layered compounds should not be good candidates as cathodes of aqueous batteries, although Li+ insertion/extraction using high concentrated LiNO3 aqueous solution as electrolyte, show results consistent with the Li (de)intercalation in organic electrolytes between the ranges from x equals 0.5-1.0 in layered LixCoO2. Thus, could layered materials have a good performance in aqueous environment despite of their tendency to accommodate protons?

In this work, we use ab-initio computations to investigate the behavior of LixCoO2 in aqueous electrolytes analyzing the proton insertion to determine which specific chemical and structural features lead to electrochemically stable materials for aqueous batteries by means of bulk and surface models. The investigations have concerned layered NaxCoO2 in order to investigate the role of stacking and ion material.

Our simulations reveal the excellent performance of LixCoO2 in contrast to NaxCoO2. By means of DFT calculations, the H+/ion exchange have been studied and the grand potential phase diagram and voltage-composition curves have been built considering different phases of LixCoO2 and NaxCoO2. Our simulations predicts the CoO(OH) as the most stable insertion/extraction product at battery operation conditions, due to the formation of O-H-O bonds. However, LixCoO2 is not affected by the presence of protons since they co-existence is not stable in comparison to full lithiated and full protonated systems. Our computations reveal that H+ could have a secondary role as surface detrimental agent, without compromising the battery performance. Nevertheless, the nature of Na and the stacking of NaxCoO2 favors the accommodation of protons, showing different performance than LixCoO2, due to the different stacking and different behavior of Na.

Our work suggests that to be layered is not enough justification to be discarded as cathode material for aqueous electrolytes. We suggest that the stacking, the alkali-proton repulsion, and specially the operation conditions (voltage window, pH...) are key factors to investigate the suitability or not of a layered material as positive electrode for ion aqueous batteries.
(Invited) Doping Considerations for Finfet, Gate-All-Around, and Nanosheet Based Devices
Authors: Duffy Ray
Published: July 2021

The IEEE International Roadmap for Devices and Systems (IRDS) for More Moore devices summarises the Logic Device state of play very effectively; the FinFET is the key device architecture that could enable logic device scaling until 2025. Increasing fin height while reducing number of fins at unit footprint area is an effective solution to improve performance. It is forecasted that the parasitics will remain as a dominant term in the performance of critical paths. For reduced supply voltage, a transition to gate-all-around (GAA) structures such as lateral nanowires or nanosheets will be necessary to improve electrostatics. Lateral GAA structure would eventually evolve in to the vertical GAA structure to gain back the performance loss due to increasing parasitics at tighter pitches. In this review we will consider doping techniques based on ion implant, solid-source in-diffusion, liquid-source in-diffusion, and gas-source in-diffusion for these device technologies.

The problem of doping source-drain regions in Si MOS devices usually boils down to the problem of (1) getting the dopant into the target structure or wafer, (2) activating the dopant by a thermal treatment, (3) controlling the crystal damage and diffusion. In these advanced device architectures, in essence, the surface is a trapping site for dopants. This isn’t too much of a problem if ions are implanted past the surface by beam-line or by plasma-assisted doping processes, however with the in-diffusion based techniques this is a severe issue.
(Invited) Atomic-Layer-Deposition of in-Situ Crystallized Ge2Sb2Te5 Alloy and Gete/Sb2Te3 Superlattice, and Their Phase-Change Performances
Authors: Hwang Cheol
Published: July 2021

This paper introduces a new atomic layer deposition process for highly conformal, nanocrystalline-as-deposited GeTe-Sb2Te3 pseudo-binary film growth at a deposition temperature of 130 °C. The process utilizes Ge(II)-guanidinate, Te(Si(CH3)3)2, and Sb(OC2H5)3 with the NH3 co-reagent. The alternative GeTe and Sb2Te3 subcycles produced various film compositions, all consistent with the GeTe-Sb2Te3 tie lines, owing to the stoichiometric reactions between the precursors without involvement of undesirable side reactions. The density of the nanocrystalline Ge2Sb2Te5 (GST225) films was 6.2 g/cm3, similar to the density of the bulk crystalline material. The crystallization behaviors indicated that the distribution of the constituent elements of the GST225 films was highly uniform at the atomic level, as opposed to the case of the low-temperature (100 °C)-deposited films. The cubic to hexagonal transition at 350 °C upon post-annealing produced (0001) hexagonal planes highly aligned along the substrate. The demonstration of the phase change memory device achieved high cycling endurance (>107).

The same ALD process was further exploited to grow the GeTe/Sb2Te3 superlattice structure, which might be an even more energy-efficient phase change material. It was found that the Sb2Te3 layer could be grown in highly c-axis oriented manner on SiO2 surface, which then can be used as the template layer for the subsequent growth of also highly c-axis oriented GeTe layer. Direct growth of the GeTe layer on SiO2 did not result in the similar optimal results. However, a certain intermixing occurs during the alternating growth of the Sb2Te3 and GeTe layers, of which details are dependent on the thickness ratio of the two layers. Interestingly, the intermixed layers still showed a certain type of layered structure, which appeared to be related to the van der Waals nature of the Sb2Te3 layer. However, such a layered structure could hardly be achieved on metallic surface such as TiN. This might be related with the highly interacting chemical nature of the TiN surface as well as the relatively rough surface topography. Adopting graphene or ultra-thin SiO2 layer on the TiN recovered the highly c-axis aligned growth behavior.
Study on Hydrogen-Based Reactive Ion Etching of Ovonic Threshold Switch (OTS) Materials for Phase Change Memory Devices
Authors: Kim Doo San , Gill You Jung , Jang Yun Jong , Kim Ye Eun , Yeom Geun Young
Published: July 2021

Phase change random access memory (PCRAM) is one of the most industrially applicable memory devices because of its advantages such as non-volatility, high speed, scalability, and low power consumption. Ovonic threshold switch (OTS) materials are used in selector devices in PCRAM circuits and are generally composed of chalcogenide compounds. In this study, etch characteristics of OTS material composed of Ge-As-Te has been investigated using reactive ion etching (RIE) by hydrogen-based gases such as H2, CH4, NH3, etc. Among the investigated hydrogen-based plasmas, NH3 showed the highest etch rate due to the high vapor pressures of the hydrides of the OTS material, but the formation of nitride compound and the increased roughness were observed on the OTS surface. In the case of CH4 plasma, due to the carbon on the OTS surface, a polymer layer was deposited. Even though H2 showed the better surface smoothness due to the no surface residues or compounds on OTS surface related to carbon or nitrogen, the etch rates were lower than NH3. In this presentation, the effects of various hydrogen-based gases on the etch characteristics of OTS material will be discussed in details.
Effect of Different Polyethylene Glycol (PEG) and Ethyl Cellulose on Impedance Spectroscopy of CuGaO2 Film
Authors: Yeasmin Humaira , Bredar Alexandria R. C. , Farnum Byron H.
Published: July 2021

Delafossite materials (CuIMIIIO2) are p-type metal oxides which can be used as hole transport layers in a wide range of heterojunction solar cells. These materials are interesting because of their crystal structure that can facilitate hole diffusion through the valance band. Maximizing the interfacial capacitance within porous nanocrystalline films of CuGaO2 is a primary goal for enhancing their performance in solar cells. The electrochemistry of CuGaO2 can reveal much information about the capacitance of the material and therefore the electronic density of valance band states. Here we have investigated the structural and electrochemical properties of CuGaO2 nanocrystalline thin films in acetonitrile solution with LiClO4 electrolyte. Nanocrystalline films are produced by dispersion of CuGaO2 nanocrystals in a polymer solution designed to control the porosity of the resulting film. We have used different molecular weights of polyethylene glycol and two different chain lengths of ethyl cellulose polymers to understand their impact on film morphology. As the film capacitance is related to surface area, a more porous film is expected to increase the film capacitance. In addition, we have also varied the CuGaO2 : polymer ratio to find the optimum condition for enhanced film capacitance. The films were characterized by powder XRD where peak ratios for (003)/(006) and (012)/(006) planes were calculated to understand the orientation of nanocrystals within the film. Electrochemical Impedance Spectroscopy (EIS) was used to probe the electrochemical behavior and capacitance of the films. We are particularly observing the Creal values at low frequency for comparative study of various films. These studies find that Creal is maximized for the ethyl cellulose polymers and a 2:1 ratio of CuGaO2 : polymer mixture.
(Invited) Scratch Controled Electrochemical Production of Macropores in Silicon
Authors: Quiroga-Gonzalez Enrique
Published: July 2021

Electrochemical etching of macropores in Si can be done either randomly (wild pores) or lithographically defined. When the points to be etched are not defined, the etching process starts at defects, or statistically distributed on the surface, just limited by the space-charge-region created in the semiconductor as effect of the electric field applied [1]. Ordered pores are usually accomplished by lithography plus a preliminary etching step for the formation of inverted pyramids [2]. At the pits of the pyramids the electric field is more intense during the electrochemical etching process, causing that the probability to etch pores is higher at those points. Defining the positions where pores are etched is necessary for different applications, where order is important. However, this makes the process to produce pores, which is not necessarily clean, more expensive with the need clean-room appliances (masking layer deposition and lithography).

In order to simplify the production of ordered micropores, in this work it is proposed to take advantage of the increased probability of surface defects to act as nucleation points of growing pores. An electronic grade single side polished p-type Si wafer, with resistivity of 20 Ωcm was used as starting material. The electrolyte was a 10 % (v/v) HF solution in DMF. The wafer was scratched with fine sand paper previous to the etching process. Electrochemical etching was performed aplying a current density of 20 mA/cm^2 for 10 min. Macropores grew mainly along the scratches (see Figure). The spacing between pores depends on the distances between scratches. The regions without scratches have a lower probability to be etched. However, if the defects introduced by the sand paper are cured by a short chemical etching process in KOH, the probability to electrochemically etch those sections is further increased, in comparison with the sections with scratches and no KOH treatment. With the observations, it is straight to think that it is possible to do deffect engingineering to tune the electrochemical etching of micropores in Si.

[1] E. Quiroga-González, H. Föll, book chapter "Chapter 2: Fundamentals of Silicon Porosification via Electrochemical Etching", in "Porous Silicon: Formation and Properties, Volume 1", editor G. Korotcenkov, CRC Press. (2015). ISBN: 9781482264548.

[2] E. Quiroga-González, E. Ossei-Wusu, J. Carstensen, H. Föll, J. Electrochem. Soc. 158(11) E119 (2011).

Figure 1
(Invited) Polymer-Based Electronics: Infrared Detectors and Supercapacitors
Authors: Ng Tse Nga
Published: July 2021

The shortwave infrared spectral region is particularly powerful for health monitoring and medical diagnostics, because biological tissues show low absorbance and minimal infrared auto-fluorescence, enabling greater penetration depth and improved resolution in comparison to visible light. Here I will discuss my lab’s development of organic infrared photodetectors using a new generation of semiconducting polymers extending to 1600 nm. Several demonstrations will show the various potential applications including blood pulse measurements, spectroscopic identification, and image reconstruction. Furthermore, we have implemented upconversion imagers that combine photo-sensing and display in a compact structure, to extend the capability of human and machine vision to 1400 nm.

In addition, the same infrared polymers are narrow bandgap and present opportunities to create energy dense supercapacitors. Here we present promising n-type polymers that retained 90% of initial capacitance after 2000 charge-discharge cycles. Through current-voltage and spectroscopic measurements, we infer the mechanisms that lead to capacitance fade and suggests structural and electrochemical strategies to realize high-endurance energy storage devices for flexible printed systems.
(Invited) Theoretical Frequency Limit of Organic Rectifier Diodes
Authors: Jung Sungyeop , Horowitz Gilles , Bonnassieux Yvan
Published: July 2021

In this communication, a new theoretical model for the ac transit frequency of organic rectifier diodes is proposed. The model is built upon a full description of the drift-diffusion current in the rectifier diode for the entire forward bias regime. Such a method precisely correlates the transit frequency to a number of materials, geometrical, and operational parameters in particular the charge-Injection barriers. By systematic variation of parameters, it is found that a rectifier operating beyond 1 GHz is observable only with a highly injecting anode. Other parameters to reach that regime of operation are discussed.

This work was supported by the Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education (NRF-2018R1D1AB07048877), and by Materials, Components & Equipment Research Program funded by the Gyeonggi Province.
Zinc - Iodine Rechargeable Flow Battery with Optimized Zn Solution for High Energy Density Devices
Authors: Accogli Alessandra , Bertoli Luca , Panzeri Gabriele , Salerno Matteo , Magagnin Luca
Published: July 2021

Nowadays, electrochemical energy storage systems have gaining interest because they constitute an essential element in the development of sustainable energy technologies [1,2]. Among them, rechargeable flow batteries (RFBs) are one of the most promising technology for the integration in grid-connected electricity, especially if combined with unpredictable and intermittent renewable energy sources, due to their high efficiency, power/energy independent sizing and room temperature operation [3]. At the moment, among all RFBs systems, the most investigated and advanced technology is the vanadium based RFB, characterized by an energy efficiency equal to 80% and energy density ranging 15-45 Wh/l [4]. However, currently the main bulk of research is focused on finding an economically convenient and technically competitive flow battery chemistry, able to ensure long lifetime and high energy efficiency [5,6]. In this study, a zinc-iodine RFB with low cost and high energy density will be presented. In particular, inorganic electrolytes based on high soluble salts have been developed to increase the charge density of the device. Moreover, a deep study on the effects of organic additive for the proper zinc developed electrolyte, aiming to reduce the dendrites growth and to increase the current efficiency, have been analyzed. In order to investigate the effect of these chemical compounds, the developed solutions have been characterized by means of cyclic voltammetries while the obtained zinc metallic coatings have been morphological characterized using scanning electron microscopy. The combination of high energy efficiency of the Zn-I RFB, in the order of 70% at 20 mA cm-2, with its very high energy density ranging from 25 to 60 Wh/l, depending on the formulation of the electrolytes, its ability to withstand a large number of charge/discharge cycles and the low cost, makes this battery system suitable for large energy storage applications.

References

P. Alotto, M. Guarnieri, and F. Moro. Renewable and Sustainable Energy Reviews 29 (2014): 325-335.

A. Z. Weber, M.M. Mench,, J.P. Meyers, P.N. Ross, J.T. Gostick and Q. Liu. Journal of Applied Electrochemistry (2011), 41(10), 1137.

G. Kear, A.A Shah, and F.C. Walsh. International journal of energy research, (2012), 36(11), 1105-1120.

C. Ding, H. Zhang, X. Li, T. Liu, and F. Xing. The Journal of Physical Chemistry Letters, (2013), 4(8), 1281-1294.

C- Xie, Y. Duan, W. Xu, H. Zhang, and X Li. Angewandte Chemie International Edition, (2017) 56(47), 14953-14957.

S. Selverston, R. F. Savinell, and J. S. Wainright. Journal of The Electrochemical Society 164.6 (2017): A1069-A1075.
Stability of Novel Anolyte and Catholyte Materials for Organic Nonaqueous Redox Flow Batteries
Authors: Giurini Michael , Dan Adina , Brinks Marcus , Hoekstra Elizabeth , Symstad Kassia , Porath Anthony , Guarr Thomas F.
Published: July 2021

In recent years, many improvements have been made in renewable energy technologies, allowing them to outcompete fossil fuels in terms of the cost-efficiency of energy production. However, the biggest challenge in the implementation of renewable energies is matching energy production to energy consumption. In an effort to bridge this gap, there has been significant academic and commercial focus on energy storage technologies, with redox flow batteries being of particular interest.

Organic nonaqueous redox flow batteries provide several improvements over traditional flow batteries. These improvements include higher accessible cell voltage, enhanced energy density, wider operating temperature range, and reduced operational costs compared to current flow battery technology. Current redox flow battery chemistries often utilize toxic metals such as vanadium for anolyte and catholyte materials. These metals are expensive, difficult to safely dispose of, and require a highly acidic electrolyte. Organic anolyte and catholyte materials provide a potential solution to these problems but also introduce other challenges, most notably stability of the battery materials in their oxidized and reduced states.

In this study a number of organic redox-active molecules been evaluated for their use as anolyte and catholyte materials capable of highly reversible one electron and two electron oxidations and reductions. Cyclic voltammetry and spectroelectrochemistry were utilized to determine oxidation or reduction potentials as well as the electrochemical stability of those materials in their oxidized or reduced states.
Preparation of Furfural Resin-Based Active Carbon with Acid Treated Pore Surface Electric Double Layer Capacitor
Authors: Hokari Kanade , Shimizu Shota , Okamoto Naoki , Saito Takeyasu , Ide Isamu , Nishikawa Masanobu , Onishi Yoshikazu
Published: July 2021

Demand for high capacity and high power energy saving devices is recently increasing for environmental conservation and energy saving. Electric double layer capacitor (EDLC) is a capacitor utilizing an electric double layer generated at the interface between an activated carbon electrode and an electrolyte. While high power and high durability are attractive, low energy density remained as a crucial issue. We reported that EDLC capacity increased as the amount of acidic surface functional groups increases. In this study, we employed mixed-acid treatment and KMnO4 treatment to introduce acidic surface functional groups on active carbon and investigated the relationship between physicochemical properties and electrical properties.

Furfural resin-based particles (1 µm in diameter) were carburized in a nitrogen atmosphere for 3 h at a temperature ramping rate of 1°C/min to 400°C. The carbonized particles were mixed with KOH at a KOH : carbonized particles ratio of 4:1; the mixture was then activated at 800°C under flowing nitrogen gas at a temperature ramping rate of 10°C/min. After heat treatment had been performed, the active carbon was impregnated with mixed acid and KMnO4. Specific surface area/pore size distribution was evaluated by N2 adsorption method. Surface functional groups were evaluated by Boehm method. Active carbon, carbon black and polytetrafluoroethylene were mixed at a mass ratio of 8: 1: 1 (=0.08 g:0.01 g:0.01 g), then pellets (14 mm in diameter and 2 mm in thickness) were prepared and dried at 115ºC for 24 hours to obtain activated carbon electrodes. Constant current charge/discharge test (potential width: 0-1.0 V, current density: 20-500 mA/g) and was performed at room temperature by two-electrode cell using KOH aqueous solution (6 M) as an electrolytic solution.

Table 1 shows the pore structure and specific capacity per weight at 20 mA/g of active carbon treated mixed-acid treatment and KMnO4 treatment. Due to acid treatment, the surface structure was destroyed and the specific surface area decreased in the following order: Control (1291 m2/g) > Mixed-acid (883 m2/g) > KMnO4 (793 m2/g) KMnO4 & Mixed-acid (358 m2/g). Although acid treatment result in a smaller specific surface area (883, 793, 358 m2/g) than that of control (1291 m2/g), they had higher specific capacity per weight (160, 219, 149 F/g) than that of no acid treatment (111 F/g). The improvement in wettability or pseudo-capacity due to redox reaction was a possible reason why the high the specific capacity per weight and high rate characteristics were obtained by the acid treatment.

Figure 1
(Invited) A Brief Overview and Future Outlook on the Progress of III-Nitride Semiconductors Research
Authors: Freitas Jaime A.
Published: July 2021

The increasing need for devices capable of performing under extreme condition of power and temperature, and opto-electronic devices operating in the UV-Vis spectral range has been the principal driving force for research interest in III-Nitrides semiconductors over the last three decades. Progress in bulk growth and film deposition techniques for homo- and hetero-epitaxial growth of III-Nitride semiconductors has led to successful fabrication and commercialization of an increasing number of devices that are revolutionizing both the optoelectronic and electronic device industries.

Many relevant figures of merit related to electronic device performance scale superlinearly with the band gap; hence, ultra-wide band gap (UWBG) materials (Eg > 3.4 eV) have the potential for far superior performance than conventional WBG materials such as GaN and SiC. UWBG materials will be critical enablers of future electronic components and systems, and a fundamental understanding of their synthesis and properties is critical to exploiting their advantages. In particular, cubic boron nitride (c-BN), among the semiconductor materials in the UWBG group (c-BN, AlN, Ga2O3, and diamond), with a band gap of ~6 eV and thermal conductivity of 13 W/mK (second only to diamond, 20 W/mK) offers the best combination of breakdown voltage and specific on-resistance. Another advantage of c-BN over other UWBG semiconductors is that it can be doped with donors and acceptors, enabling the fabrication of bipolar devices.

The development of high quality GaN substrates and device grade films will be reviewed and a brief overview of the intrinsic properties of the WBG and UWBG semiconductors will be presented.
Effect of HfO2 Passivation Layer on Light Extraction Efficiency of AlInN Nanowire Ultraviolet Light-Emitting Diodes
Authors: Patel Moulik , Jain Barsha , Velpula Ravi Teja , Nguyen Hieu Pham Trung
Published: July 2021

Diverse applications of ultraviolet (UV) light in the field of purification, sterilization, detection, surface disinfection, sensing, and many others have been studied mostly on AlGaN light-emitting-diodes (LEDs). However, the external quantum efficiency (EQE) of AlGaN deep UV LEDs is limited due to strong induced polarization fields, high dislocation density, severe electron leakage, difficulty in p-type doping, low internal quantum efficiency (IQE), IQE droop, and low light extraction efficiency (LEE). Alternatively, AlInN semiconductor has been recently gained tremendous attention for high power UV LEDs [1-3]. Our group has successfully demonstrated the first AlInN core-shell nanowire UV LEDs with a relatively high IQE of ~52%[1]. However, the light extraction study of such nanowire LEDs is unexplored. In this context, we have studied the LEE of a single AlInN nanowire UV LED at 220 nm - 400 nm wavelength regime. Moreover, we report that the LEE of a single AlInN nanowire UV LED could be increased by ~60% using HfO2 passivation compared to conventional nanowire LED at 282 nm.

The schematic structure of AlInN nanowire UV LED is shown in Figure 1(a). The nanowire is composed of 200 nm n-GaN, 100 nm n-AlxIn1-xN quantum barrier (QB)/40 nm i-AlyIn1-yN quantum well (QW)/100 nm p-AlxIn1-xN QB, and 20 nm p-GaN layer. We have estimated the LEE of nanowire LEDs using the finite difference time domain (FDTD) simulation method. Silicon (Si) is used as a substrate, and the n-GaN layer is tapered with a diameter from 70 nm (bottom) to 100 nm (top). The diameter is set to be 100 nm for the rest of the regions. We have placed a single TM-polarized dipole source at the QW center to calculate LEE for a nanowire LED in the simulations. The estimated LEE of 282 nm wavelength single nanowire AlInN UV LED with various HfO2 passivation layers thickness is provided in Figure 1(b). The LEE of such LED without any passivation is ~25.2%, whereas the maximum recorded LEE is ~40.6% with the utilization of 35nm thickness HfO2 passivation layer. This study provides a promising approach for enhancing the light extraction efficiency of nanowire UV LEDs.

Reference

R. T. Velpula, B. Jain, M. R. Philip, et al., Sci. Rep., 10(1) 2547-2556 (2020).

R. T. Velpula, B. Jain, H.Q.T. Bui, et al., Opt. Mater. Express, 10(2), 472-483 (2020).

B. Jain, R. T. Velpula, M. Tumuna, et al., Opt. Express, 28(15), 22908-22918 (2020).

Figure 1
(Invited) Optically-Active Zero-Dimensional Graphene Quantum Dots with MoS2 for Photodetection
Authors: Kaul Anupama B
Published: July 2021

With its superior electronic properties, large surface area, high mechanical strength-to-weight ratio, exceptional charge carrier mobility reaching the ballistic limit in certain cases, graphene is a material of immense technological importance. However, compared to other two-dimensional (2D) van der Waals solids, such as transition metal dichalcogenides (TMDCs) and black phosphorus, an atomic membrane of graphene absorbs less than about 2% of the incoming light due to its low light absorption cross-section, and lack of a bandgap. However, when sheets of graphene are physically confined into nanoscale dimensions, either as graphene nanoribbons or zero-dimensional (0D) structures, such as graphene quantum dots (GQDs), a band gap in such structures is induced due to quantum confinement. Additionally, semiconducting 2D materials such as MoS2, exhibit a distinct and well defined band gap ranging from 1.3 eV to 1.8 eV, from bulk to monolayers. In this work, the hybrid structure of 0D graphene quantum dots (GQDs) and semiconducting 2D MoS2 has been investigated that exhibit outstanding properties for optoelectronic devices surpassing the limitations of MoS2 photodetectors where the GQDs extend the optical absorption into the near-UV regime. A tunable laser revealed the photocurrent to be maximal at lower wavelengths in the near ultra-violet (UV) over the 400 – 1100 nm spectral range, where the responsivity of the hybrid GQDs/MoS2 was ~ 775 AW-1. Time-resolved measurements of the photocurrent for the hybrid devices also resulted in enhancement of the switching dynamics with switching time constants far improved compared to bare MoS2. From our promising results, we conclude that the GQDs exhibit a sizable bandgap upon optical excitation, where photocarriers are injected into the MoS2 films, endowing the hybrids with long carrier life-times to enable efficient light absorption beyond the visible and into the near-UV regime. The GQD-MoS2 structure is thus an enabling platform for high-performance photodetectors, optoelectronic circuits and quantum devices.
(Invited) Recent Advances in the Modeling of ZnSySe1-y / GaAs (001) Heterostructures with Application to Dislocation Sidewall Gettering
Authors: Ayers John , Kujofsa Tedi , Raphael Johanna
Published: July 2021

In this talk we will describe state-of-the-art approaches to the modeling of strain relaxation and dislocations in ZnSySe1-y/GaAs (001) heterostructures, with applications to dislocation sidewall gettering (DSG) in devices. Current modeling approaches are based on the extension of the original Dodson and Tsao plastic flow model [B. W. Dodson and J. Y. Tsao, Appl. Phys. Lett., 51, 1325 (1987); Appl. Phys. Lett., 52, 852 (1988)] to include compositional grading and multilayers, dislocation interactions, and differential thermal expansion. Important recent breakthroughs have greatly enhanced the utility of these modeling approaches in three respects: i) pinning interactions have been included in graded and multilayered structures, providing a better description of the rate of strain relaxation as well as the limiting strain; ii) a refined model describing the interaction length for dislocation-dislocation interactions was formulated to include jogging in compositionally-graded and step-graded layers; and iii) inclusion of back-and-forth weaving of dislocations provides a more accurate description of heterostructures containing strain reversals, such as strained-layer superlattices or overshoot graded layers. We will describe these three key advances and use reasonable estimates of the kinetic parameters for ZnSySe1-y to explain and illustrate practical features of dislocation sidewall gettering in II-VI heterostructures.
(Invited) Electrical Performance Improvement in 300mm Ge-Based Devices
Authors: Tapily Kandabara , Nakamura Genji , Consiglio Steven , Clark Robert D , Newman Danny , Triyoso Dina H. , Niimi Hiroaki , Wajda Cory S , Leusink Gert J
Published: July 2021

As device feature size continues to scale, new device architecture and dielectric materials with engineered properties are becoming essential in overcoming the issues in scaled CMOS devices such as short channel effects. Some of the recent innovations device makers are exploring for better electrostatic control and improved performance are the introduction of new device architecture such as gate all around devices (nanowires/nanosheets), and channel engineering such as high mobility channel materials (Ge and III-V). Ge is particularly attractive for use as a channel material for P-type MOSFETs due to its high hole mobility and Si VLSI high volume manufacturing (HVM) compatibility. However, there are couple significant remaining challenges to integrating Ge into 300mm Si VLSI HVM which are a stable gate-stack formation and integration of Ge on Si (1-5). In this talk, advances in Ge gate stack engineering will be discussed. Using Si compatible technologies we have demonstrated scaled EOT by engineering both the interface and high-k formation.

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Optical and Structural Properties of Ga and in Co-Doped ZnO Nanocrystals Films
Authors: El Filali Brahim , Torchynska Tetyana , Garcia Jorge Luis Ramirez , Lozada Erick Velazquez , Shcherbyna Lyudmyla
Published: July 2021

The impact of double donor doping on the crystal structure, emission and electrical resistivity has been studied in the ZnO:Ga:In films. The films were deposited by ultrasonic spray pyrolysis on a previously cleaned silicon substrate. To the study of double donor doping, two groups of samples were prepared. In the first group the In content was 1at% and the Ga contents were varied in the range 0.5-3.0at.%. In the second group the In content was 2at% and the Ga content were changed in the range 0.5-2.5at%. To stimulate the film crystallization, all samples were annealed at 400oC for 2 hours in nitrogen flow 5l/min. The high quality nanocrystal (NC) films with the wurtzite-type crystal structure, bright near band edge (NBE) emission and the small intensity of defect related PL bands have been aobtained. The variation non monotonically of the ZnO crystal lattice parameters, as well as the PL intensities of NBE emission bands has been detected. The reasons for the parameter variation non monotonically and the optimal concentrations for the Ga/In double donor doping of ZnO NC films have been analyzed and discussed.

Corresponding author E mail: braelf@hotmail.com
(Invited) Wearable Electrochemical Sensor for Detection of Multianalyte Biomarkers in Wound Healing Efficacy
Authors: Simoska Olja , Stevenson Keith J
Published: July 2021

The targeted diagnosis and effective treatments of chronic wounds remain a significant healthcare challenge, requiring the design of analytical sensors for real-time monitoring of wound healing activity. Herein, we describe an adaptable method for the fabrication of carbon ultramicroelectrode arrays (CUAs) on flexible substrates with the goal to utilize this sensor as a wearable device to monitor chronic wounds. As a proof-of-concept study, we demonstrate the electrochemical detection of three electroactive analytes as biomarkers for wound healing state in a wound fluid simulant on flexible CUAs. Notably, to follow pathogenic responses, we characterize the analytical figures of merit for identification and monitoring of bacterial warfare toxin pyocyanin (PYO) secreted by the opportunistic human pathogen Pseudomonas aeruginosa. We also demonstrate the detection of uric acid (UA) and nitric oxide (NO•), which are signaling biomolecules indicative of wound healing, and immune responses, respectively. The electrochemically determined limit of detection (LOD) and linear dynamic range (LDR) for PYO, UA, and NO• fall within the clinically relevant concentrations for each biomarker. In addition, we demonstrate the successful use of flexible CUAs for quantitative, electrochemical detection of PYO from P. aeruginosa strains and cellular NO• from immune cells in the wound matrix. An electrochemical examination of the interaction between PYO and NO• is also presented, providing insight into pathogen-host responses. Finally, the effects of the antimicrobial agent, silver (Ag+), on P. aeruginosa PYO production rates are investigated on flexible CUAs. Our quantitative electrochemical results show that the addition of Ag+ to P. aeruginosa cultures in wound simulant decreases PYO secretion rates.
(Invited) Perspective on Operational Bio/Chemical Sensors for Human Performance Monitoring and Optimization
Authors: Kim Steve , Brothers Michael
Published: July 2021

Monitoring the human performance plays a significant role in many sectors including the military, first responders, athletics, and aerospace. Minimally invasive and non-invasive biomarker sensors are paramount keys to achieving real time human performance monitoring. The sensors’ role is to report physical, psychological, and physiological statuses of the individuals, in which the performance readings can be ultimately used to assess their readiness and ability to carry out assigned tasks. In this talk, the biomarkers indicative of human performance are going to be discussed including their limits in operational sensing with respect to the applicable chemical and biochemical sensor technologies. Following this, a perspective on the state of the art sensor technologies aimed to human performance monitoring and optimization applications is to be provided. In addition, an in-depth discussion on chemical, biochemical, and physical transducers based on electronic and electrochemical detection methods is going to be delivered.
(Invited) Hydrogel Bio-Electronics and Bio-Optics
Authors: Zhao Xuanhe
Published: July 2021

Whereas human tissues and organs are mostly soft, wet and bioactive; machines are commonly hard, dry and biologically inert. Merging humans, machines and their intelligence is of imminent importance in addressing grand societal challenges in health, sustainability, security, education and joy of living. However, interfacing humans and machines is extremely challenging due to their fundamentally contradictory properties. At MIT Zhao Lab, we exploit soft materials technology to form long-term, high-efficacy, multi-modal interfaces and convergence between humans and machines. In particular, hydrogels with similar mechanical and physiological properties as various biological tissues have been explored as an ideal material candidate for such human-machine interfaces and convergence. This talk will focus on Hydrogel Bio-electronics and Bio-optics. I will first discuss the general principles to design hydrogels to possess extraordinary mechanical, electrical and optical properties. I will then introduce a 3D printing method for the fabrication of various hydrogel bio-electronic and bio-optic devices, including wearable, ingestible and implanted devices. Thereafter, I will discuss in vivo tests on the long-term biocompatibility, functionalities, and efficacy of the hydrogel bio-electronics and bio-optics in rat and pig models. I will conclude the talk with a perspective on future human-machine convergence enabled by soft materials technology.
(Invited) Bio-Inspired Electronic Eye and Wirelessly-Integrated Wearable/Implantable Device
Authors: KIM Dae-Hyeong
Published: July 2021

Despite recent progresses, significant challenges still exist in developing a miniaturized and lightweight type of artificial vision that features wide field-of-view (FoV), high contrast, and low noise. Meanwhile, the wireless integration of wearable devices with implantable devices can present a new opportunity in the development of unconventional biomedical electronic devices. In this talk, recent progresses in the bio-inspired electronic eye and the wirelessly-integrated bioelectronics will be presented. In the first part, a fish-eye-inspired camera integrating a monocentric lens and a hemispherical silicon-nanorod photodetector array will be presented. In the second part, a bioelectronics device that consists of a soft implantable drug delivery device integrated wirelessly with a wearable electrophysiology sensing device will be presented. These novel types of device are expected to provide new opportunities for the next generation bio-inspired electronics and bio-integrated electronics.
(Invited) Adding a New Sensing Dimension to Soft Electronics: From the Skin to below the Skin
Authors: Xu Sheng
Published: July 2021

Soft electronic devices that can noninvasively and continuously acquire vital signs from the human body represent an important trend for healthcare. Combined strategies of materials design and advanced microfabrication allow the integration of a variety of components and devices on a soft platform, resulting in functional systems with minimal constraints on the human body. In this presentation, I will demonstrate a wearable multichannel patch that can sense a collection of signals from the human skin in a wireless mode. Additionally, integrating high-performance ultrasonic transducers on the stretchable substrate adds a new third dimension to the detection range of conventional soft electronics. Ultrasound waves can penetrate the skin and noninvasively capture dynamic events in deep tissues, such as blood pressure and blood flow waveforms in central arteries and veins. This soft platform holds profound implications for a wide range of applications in consumer electronics, sports medicine, defense, and clinical practices.

Figure 1
Pr-Based Nanofiber Cathode for Intermediate Temperature SOFCs
Authors: Gumeci Cenk , Parrondo Javier , Abdul Jabbar Mohammed Hussain , Thompson Dave , Dale Nilesh
Published: July 2021

In this work, praseodymium based double perovskite (PrBa0.5Sr0.5Co1.5Fe0.5O5+𝛿) - PBSCF nanofibers cathodes were fabricated by electrospinning technique for intermediate-temperature solid oxide fuel cells (IT-SOFCs).The optimized three-dimensional nanofiber network cathode provides high porosity coupled with the higher interfacial contact area, leading to a faster oxygen reduction reaction (ORR) kinetics.

EIS analysis of the nanofiber structured cathode resulted in a polarization resistance of ~0.025 Ω cm2 at 750 °C. Resulted low resistance is smaller than the commercial LSCF cathode showing polarization resistance of ~0.041 Ω cm2 at 750 °C. The peak power densities of the PBSCF fibers are ~2539, 1580 and 993 mW/ cm2 at 750, 700, and 650 °C, respectively when compared to LSCF cathode performance of ~ 1974, 1304 and 769 mW/ cm2 at same temperature. Such promising performance of fiber cathode IT-SOFCs in this study was achieved via careful selection of the catalyst structure and composition, electrode structure for efficient ORR, and perhaps through process optimizations. The results obtained in this study illustrates that one-dimensional nanostructures obtained by adopting nanofibers can be an appropriate cathode material choice for intermediate-temperature SOFCs suitable for automotive applications.
(Invited) Metal-Supported Solid Oxide Fuel Cells and Electrolyzers for Low-Cost, Robust, Rapid-Start Systems
Authors: Tucker Mike C , Shen Fengyu , Hu Boxun , Welander Martha M , Skafte Theis Løye , Lau Grace Y.
Published: July 2021

This talk will provide an overview of performance, durability, and applications of metal-supported solid oxide fuel cell and electrolysis cell technology developed at Lawrence Berkeley National Laboratory (LBNL). The unique LBNL symmetric cell architecture design, with thin zirconia ceramic backbones and electrolyte sandwiched between porous metal supports, offers a number of advantages over conventional all-ceramic cells, including low-cost structural materials (e.g. stainless steel), mechanical ruggedness, excellent tolerance to redox cycling, and extremely fast start-up capability.

MS-SOFC performance with a variety of fuels will be presented, including hydrogen, ethanol, natural gas, and simulated reformates. The impact of the presence of carbon and internal reforming catalysts on the durability of the cells will be examined. In particular, oxidation of the stainless steel supports in the presence of carbon is analyzed. Scale-up from button cells to 50cm2 will be presented.

The case for use of MS-SOECs for dynamic electrolysis operation will be made. Detailed analysis of degradation modes over 1000h of operation with 50/50 steam/H2 informed efforts to improve durability through the use of coatings and catalyst processing techniques.

In addition to our long-standing development of zirconia-based metal-supported cells, recent efforts on metal-supported proton-conducting cells are ongoing. Co-sintering of 400-series stainless steel and BZCY-type proton conductors presents a number of challenges, including: Ba evaporation in reducing atmosphere, over-densification of steel at the high temperatures (>1400°C) required for BZCY processing, mismatch of metal and ceramic sintering behavior, and migration of Cr and Si from the steel support into the BZCY layers. Feasibility of new approaches to overcome these challenges will be discussed.