bluuebunny/crossref_metadata_2025_split huggingface dataset:
(Invited) Hexagonal Boron Nitride Epilayers
Authors: Jiang Hongxing , Lin Jingyu 
Published: February 2020

As a member of the III-nitride wide bandgap semiconductor family, BN has received much less attention in comparison with other nitride semiconductors. The stable phase of BN synthesized at any temperature under ambient pressure is hexagonal. Due to its wide bandgap (> 6 eV) and layered structure, hexagonal BN (h-BN) is an ideal platform for probing fundamental 2D properties of wide bandgap semiconductors. In this talk, a brief overview of the synthesis and electrical and optical properties of wafer-scale h-BN epilayers will be presented [1-7]. It was shown that the unique 2D structure of h-BN induces exceptionally high density of states, large exciton binding energy and high optical absorption and emission intensity. By growing h-BN under high V/III ratios, epilayers exhibiting pure free exciton emission have been obtained [4]. Photocurrent excitation spectroscopy results directly provided a room temperature bandgap value for h-BN in between 6.4 and 6.5 eV and the free exciton binding energy (Ex) of 0.73 eV [5]. Layer-structured B-rich BGaN alloys, heterostructures, and quantum wells have also been successfully grown and their properties will be discussed. Thermal neutron detectors fabricated from 100% B-10 enriched h-BN epilayers of thicknesses exceeding 50 mm have attained the highest detection efficiency to date among solid-state detectors at about 58% [6, 7]. These solid-state neutron detectors have become increasingly desirable for a wide range of applications from fissile materials sensing to well logging, because 3He gas detectors are inherently bulky, require high pressurization and high voltage application, slow response time, and expensive. It is our belief that h-BN will lead to many potential applications from deep UV optoelectronics, radiation detectors, to novel layered-structured photonic and electronic devices.
[1] R. Dahal, J. Li, S. Majety, B.N. Pantha, X. K. Cao, J. Y. Lin, and H.X. Jiang, Appl. Phys. Lett. 98, 211110 (2011).
[2] S. Majety, J. Li, X. K. Cao, R. Dahal, B. N. Pantha, J. Y. Lin, and H. X. Jiang, Appl. Phys. Lett. 100, 061121 (2012).
[3] H. X. Jiang, and J. Y. Lin, Semicon. Sci. Technol. 29, 084003 (2014).
[4] X. Z. Du, J. Li, J. Y. Lin, and H. X. Jiang, Appl. Phys. Lett. 106, 021110 (2015); 108, 052106 (2016).
[5] T. C. Doan, J. Li, J. Y. Lin, and H. X. Jiang, Appl. Phys. Lett. 109, 122101 (2016).
[6] A. Maity, T. C. Doan, J. Li, J. Y. Lin, and H. X. Jiang, Appl. Phys. Lett. 109, 072101 (2016).
[7] A. Maity, S. J. Grenadier, J. Li, J. Y. Lin, and H. X. Jiang, Appl. Phys. Lett. 111, 033507 (2017) and J. Appl. Phys. 123, 044501 (2018).
Magnetic III-N Semiconductors Based on Rare Earth Doping
Authors: Zavada John M 
Published: February 2020

This paper focuses on the magnetic properties of wide bandgap III-N semiconductors doped with rare earth elements. Such materials form a novel class of dilute magnetic semiconductors that have an important potential impact on future information processing devices [1]. In particular, rare earth doped III-N thin films may lead to integration of electronic, optical, and magnetic functionality for sensing and communication applications. The two main thrusts of this paper are the efficient incorporation of rare earth ions in III-N thin films and the demonstration of magnetic effects at room temperature. While early studies were based on ion implantation and solid-state diffusion, major advances have been achieved through molecular beam epitaxy and metal-organic chemical vapor deposition. [2, 3]. Measurements of room temperature magnetic effects from III-N films doped with rare earth elements, including neodymium, europium, gadolinium, erbium, and thullium, will be presented. The dependence of the magnetic properties on the synthesis method and co-doping will be addressed.
[1] Rare Earth and Transiton Metal Doping of Semiconductor Materials: Synthesis, Magnetic Properties and Room Temperature Spintronics, Ed. V. Dierolf, I.T. Ferguson and J.M. Zavada (Elsevier Woodhead Publishing, 2016).
[2] “Er Doping of AlN During Growth by Metalorganic Molecular Beam Epitaxy,” J.D. MacKenzie, C.R. Abernathy, S.J. Pearton, U. Hömmerich, X. Wu, R.G. Wilson, J.M. Zavada, and R.N. Schwartz, Appl. Phys. Lett.692083 (1996).
[3] “Erbium-doped GaN epilayers synthesized by metal-organic chemical vapor deposition,” C. Ugolini, N.Nepal, J. Y. Lin, H. X. Jiang, and J. M. Zavada, Appl. Phys. Lett. 89151903 (2006).
(Invited) Graphene Based Devices for in Vitro and In Vivo Electrophysiology
Authors: Offenhäusser Andreas , Kireev Dmitry 
Published: February 2020

In the field of electrophysiology, graphene has just recently gained impact in cellular interfacing. Compared to silicon-based transistors, they are more sensitive, hence more favorable. Moreover, intrinsic flexibility and biocompatibility of graphene has a promising future for this research, pointing out in the direction of fully flexible, soft and implantable neuroprosthetic applications. There, graphene can be used either actively as a transistor's active area or passively as an electrode material. In the first case, the device requires at least two electrodes (source and drain), complicated electrochemical gating, and read-out schematics while in the second case there is just one feedline required to feed and record from a graphene electrode. Moreover, such graphene-based electrodes are comparably easy to fabricate, characterize and use.
In this presentation, we will describe a method to fabricate arrays of graphene-based probes, requiring minimal number of fabrication steps, while maintaining overall device functionality. These devices are either fabricated on rigid or flexible substrates. Devices, such as graphene field effect transistors (GFETs) and graphene multielectrode arrays (GMEAs) have been designed, fabricated and tested for their performance. The flexible GFETs exhibit an order of magnitude larger sensitivity compared to silicon transistors with similar geometry. Multiple probe per wafer design allows us to fabricate different kinds of devices on one 4-inch wafer, consequently increasing a possible range of applications from e.g. retinal to cortical neuroprosthetics.
An Ionic Polymer Actuator Capable of Simultaneously Improving Bandwidth and Blocking Force for Efficient Haptic Feedback
Authors: Choi Hanbin , Kim So Young , Kim Yongchan , Cho Changhyeon , Lee Hojin , Kim Do Hwan 
Published: February 2020

Recently, an ionic electroactive polymer (i-EAP) actuators are spotlighted in various fields because they provide a lot of advantages such as lightweight, flexibility, simple process, and low driving power. However, they suffer from low blocking force, displacement, and wide bandwidth that can be implemented under electric field for apply to various applications. In order to apply these i-EAP actuators to various applications, it is important to provide the optimum characteristics of the i-EAP actuator adaptive to the target application. Particularly, it is required to achieve high blocking force and displacement as well as wide actuation bandwidth for haptic feedback among the various applications.
In this talk, we propose an ionic polymer actuator (IPA) with wide bandwidth of over 100Hz and high blocking force based on PEDOT:PSS electrode with additives and ionic polymer with fibrillary nanostructures for effective haptic feedback. In particular, we developed an actuator that improves the interfacial properties between electrodes and an ionic polymer as well as electrical conductivity of electrodes by simple and effective way through spray-coating of PEDOT: PSS solution with additives. As a result, the IPA was successfully operated with a large displacement up to 2.5mm at an operating frequency of 20mHz under an applied voltage of 2V. Further, the IPA shows large blocking force of 0.4mN at operating frequency of 1Hz. These our actuator is capable of driving up to a high frequency of 200Hz and shows an improved blocking force up to 0.4mN. We potentially believe our IPA will provide a rational guide to future haptic feedback.
(Invited) what Limits the Intrinsic Carrier Mobility of Two Dimensional Metal Dichalcogenides?
Authors: Liu Yuanyue 
Published: February 2020

Two-dimensional (2D) metal dichalcogenides (MX2) are the most common type of 2D semiconductors and have shown great potential for a wide range of chemical and physical applications. However, they are limited by a low electron/hole mobility, which has been recognized as one of the major challenges impeding their further developments, and urges efforts to understand the mobility-limiting factors and discovery of higher-mobility alternatives. Here using density functional perturbation theory and Wannier interpolation of the electron–phonon matrix to study a wide range of MX2, we find that the intrinsic carrier mobility, in contrast to common belief, neither correlates with the effective mass nor can be assessed by the widely used deformation potential theory; instead it is limited by the longitudinal optical (LO) phonon scattering for most MX2, while for MoS2 and WS2, the mobility is limited by the longitudinal acoustic (LA) phonon scattering. Furthermore, we find that the LO scattering strength is strongly correlated with the magnitude of the Born effective charge, suggesting that the carrier transport is greatly affected by the electric polarization change induced by the atomic vibration. This finding enables us to use the Born effective charge to rapidly screen the 2D MX2 database for high-mobility semiconductor candidates. Our work reveals the underlying factors governing the intrinsic carrier mobility of 2D MX2, and offers a practical descriptor for discovering high-mobility candidates.
Ref: L. Cheng, Y. Liu, JACS, 2018, DOI: 10.1021/jacs.8b07871
(Invited) visco-Poroelastic & Iontronic Pump: New Strategy for Ultrasensitive Artificial Skin Sensors
Authors: Kim Do Hwan 
Published: February 2020

Creating artificial sensor skins that shows the tactile- and chemical-sensing capability of human skin has been a big challenge in wearable sensor research. In particular, biomimetics has emerged as a burgeoning area in the field of deformable tactile sensor skins that has led innovations in material designing and device structure manipulation with the aim of imitating multimodal sensing features of human skin intelligently.
Herein, inspired by the sophisticated physiological sensing mechanism of living cells, we describe a uniquely designed visco-poroelastic, iontronic pump consisting of artificial ions confined into polymeric network matrix or well-designed hybrid interface. Novel bottom-up strategy employed here resulted into supramolecular polymer networks through non-covalent interactions between poroelastic artificial ions and viscoelastic polymer chains, which endows effective iontronic pumping under mechanical stimuli and electronic field, simultaneously. This design for visco-poroelastic, iontronic, and ion confined artificial mechanoreceptors allows for ultrasensitive mechanosensing over a wide spectrum of pressure (Pa~150kPa) beyond capabilities of human skin. Moreover, our devices could visualize the local variation in the applied pressure or electronic field without using spatially distributed device arrays.
(Invited) Flexible Nanogenerators for Energy Harvesting and Self-Powered Biomedical Devices
Authors: Xie Yannan 
Published: February 2020

Recently, flexible electronics have experienced a rapid development and are dramatically desirable for commercial, medical, and military applications. Conventional flexible biomedical sensors usually require external power-supply devices whose small power density and limited lifetime dramatically hinder the speedy advancement of this field. To solve the above issues, self-powered sensing technology has been introduced and attracted significant interests as a crucial alternative. The self-powered active sensor will generate electricity as a response to the external stimuli and the electric signal can reversely reflect the impact of the outside trigger. Therefore, it is able to effectively and independently work without any external power sources and hence its accelerated progress is of great significance to the prevalence of wearable and flexible sensors.
Originated from Maxwell’s displacement current, nanogenerator (NG) based on triboelectric effects have been developing rapidly for efficiently harvesting environmental mechanical energy and self-powered active sensor. Triboelectric nanogenerator (TENG) relied on a conjunction of triboelectrification and electrostatic induction has shown numerous advantages, including large output, high efficiency, low cost, simple fabrication, light weight, and being environmental friendly. Besides mechanical energy, thermal energy is another important energy source especially for wearable electronics. The temperature difference (ΔT) between human body and surrounding environment always exists and can be used as driving force for electric energy generation through Seebeck effect. But the ΔT need to be furtherly enhanced. In our living environment, in addition to the direct heat source, light source (such as the infrared light) can also provide thermal energy through the photothermal effect. Based on the photothermal effect and Seebeck effect, photo-thermoelectric generator has been rapidly developed for converting photo energy into electricity without a spatial temperature gradient in the environment.
In our works, flexible NGs based on triboelectric effect and photo-thermoelectric effect have been demonstrated and designed for wearable electronics. The electric signals obtained from the NGs not only can be acted as direct energy sources for flexible devices but also used for self-powered biomedical applications, such as human motion monitoring, temperature sensing, anti-bacterial treatment, and so on.
(Invited) Flexible Human-Machine Interfaces and Damage Robust Stretchable Optoelectronics
Authors: Tee Benjamin CK 
Published: February 2020

Electronic devices and machines are undergoing exciting form factor evolutions by adopting formats closer to human skins[1–5]. At the same time, almost all forms of human-machine interfaces require electrically activated light sources to facilitate the interactions. These emerging trends present challenges as well as opportunities for innovations in light emitting devices that are robust to mechanical strains and even severe electro-mechanical damage. Self-healing materials have been shown to be useful in electronic devices and impart repeatable healing of electro-mechanical performance[6,7]. At the same time, stretchable light sources have been demonstrated for applications in soft robotics and touch interfaces[8]. In my talk, I will discuss recent progress in pressure sensor designs, as well as our efforts to develop a stretchable and damage robust opto-electronic materials.

References

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2014, 5, 1.
[2] Z. Huang, Y. Hao, Y. Li, H. Hu, C. Wang, A. Nomoto, T. Pan, Y. Gu, Y. Chen, T. Zhang, W. Li, Y. Lei, N. Kim, C. Wang, L. Zhang, J. W. Ward, A. Maralani, X. Li, M. F. Durstock, A. Pisano, Y. Lin, S. Xu, Nat. Electron.
2018, 1, 473.
[3] L. Y. Chen, B. C. K. Tee, A. L. Chortos, G. Schwartz, V. Tse, D. J. Lipomi, H. S. P. Wong, M. V McConnell, Z. Bao, Nat. Commun.
2014, 5, 1.
[4] D.J. Lipomi, B.C.K. Tee, M. Vosgueritchian, Z. Bao, Adv. Mater.
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[5] B. C. K. Tee, A. Chortos, A. Berndt, A. K. Nguyen, A. Tom, A. McGuire, Z. C. Lin, K. Tien, W. G. Bae, H. Wang, P. Mei, H. H. Chou, B. Cui, K. Deisseroth, T. N. Ng, Z. Bao, Science (80-. ).
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[6] Y. J. Tan, J. Wu, H. Li, B. C. K. Tee, ACS Appl. Mater. Interfaces
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[7] B. C.-K. Tee, C. Wang, R. Allen, Z. Bao, Nat. Nanotechnol.
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[8] S. Li, B. N. Peele, C. M. Larson, H. Zhao, R. F. Shepherd, Adv. Mater.
2016, 28, 9770.
High Efficiency Multi-Level Flexible Triboelectric Nanogenerator for Wearable Electronics
Authors: Ravichandran Aravind , Ramuz Marc , Blayac Sylvain 
Published: February 2020

With the rapid development of wearable electronics and sensor networks, batteries cannot meet the sustainable energy requirement due to their limited lifetime, size and degradation. With miniaturization leading to high-power and robustness, triboelectric nanogenerators(TENGs) have been conceived as a promising technology by harvesting mechanical energy to power small electronics and wearables. The main issues associated with TENGs are their very low output power leading to lower output charge density and high impedance matching.
In this work, a state of the art multilayer flexible structure is devised which not only increases the charge density but also provides a high average power output. Thin-film organic flexible materials are deposited to acquire charges from the triboelectrification process, allowing the acceptance of more charges from an electrode and thereby increasing the power output. Material work function provide better understanding towards charge transfer process.
A proof of concept device is conceptualized for use in a highly efficient self-powered sensor network system, converting ambient mechanical energy to electricity with a 1.2kV peak amplitude and a very high device performance. This device structure makes the TENGs attractive to charging applications for wearables and large-scale harvesting without massive volume. By this technique, we have overcome numerous friction-based operation challenges including lack of uniform contact, material loss through wear, high sensitivity to humidity, and output power storage.
By considering these merits of simple fabrication, outstanding performance, robust characteristic and low-cost technology, we believe that multi level flexible TENGs can open great opportunities not only for powering small electronics but can contribute to large-scale energy harvesting through engineering design being complementary to existing energy sources.
The Catalytic Roles of Surface Transition Metals on the Hydrogen Evolution/Oxidation Reactions of Pt-Surfaces in Base
Authors: Liu Ershuai , Jiao Li , Mukerjee Sanjeev , Jia Qingying 
Published: February 2020

Despite the importance of the hydrogen evolution and oxidation reactions (HER/HOR) to modern electrocatalysis, their sluggish kinetics in alkaline remains unclear. Recent efforts have shown that surface deposition of transition metals on platinum electrode can dramatically affect the HER and/or HOR performance. However, the catalytic roles of the second metal are unclear. For some of the metals (such as Mn and Fe) it even remains inconclusive whether they are beneficial or detrimental to the HER/HOR performance.1,2Herein, we systematically investigated the catalytic roles of several transition metals including Mn, Fe, Co, Ni, Cu, and Ru by electrochemically depositing them onto Pt surfaces. We conclusively show that all the studied metal except for Cu benefits the HER of Pt surfaces, whereas only Ni (marginally) and Ru benefits the HOR. On the basis of these electrochemical results and in situx-ray absorption spectroscopy data. we propose that the second metal on the surface impact the HER/HOR kinetics via affecting the transportation of the hydroxide throughout the double layer region. This finding may help to rationalize bimetallic mechanism for HER/HOR in alkaline.
(1) Rebollar, L.; Intikhab, S.; Snyder, J. D.; Tang, M. H. Determining the Viability of Hydroxide-Mediated Bifunctional HER/HOR Mechanisms through Single-Crystal Voltammetry and Microkinetic Modeling. J. Electrochem. Soc.
2018, 165, J3209-J3221.
(2) Subbaraman, R.; Tripkovic, D.; Chang, K.-C.; Strmcnik, D.; Paulikas, A. P.; Hirunsit, P.; Chan, M.; Greeley, J.; Stamenkovic, V.; Markovic, N. M. Trends in activity for the water electrolyser reactions on 3d M (Ni, Co, Fe, Mn) hydr (oxy) oxide catalysts. Nat. Mater.
2012, 11, 550-557.

Figure 1
Isotope-Labeling Studies in Water Oxidation Electrocatalysis
Authors: Scott Soren B. , Sørensen Jakob E. , Kibsgaard Jakob , Chorkendorff Ib 
Published: February 2020

Improving understanding of the electrocatalytic mechanisms for the oxygen evolution reaction (OER) will help in designing electrode materials with lower catalytic overpotential and greater stability, increasing the efficiency and economic viability of electrolysis. Isotope-labeling can be a powerful tool for elucidating catalytic mechanisms, including in electrocatalysis. Herein, we apply 18-O labeling, utilizing a fully quantitative electrochemistry - mass spectrometry method with unprecedented sensitivity[1] and post-characterization by low-energy ion scattering spectrometry, to investigate the electrocatalytic mechanism of oxygen evolution.
Nickel-iron based electrodes are used in industrial alkaline water electrolysis, but questions remain about the intrinsic activity and electrocatalytic mechanism. By performing a series of isotope-labeling experiments on a model system of mass-selected Ni-Fe nanoparticles, we show that oxygen evolution does not proceed via lattice oxygen exchange and that only the surface of the nanoparticles are active[2]. This allows us to estimate the turn-over frequency of the active sites, 6 O2 molecules per site per second, which is higher than previous estimates. We also quantify lattice oxygen exchange in IrO2 and RuO2 thin films during oxygen evolution in acidic electrolyte as a function of electrochemical roughening, and perform oxygen stripping experiments to probe OER intermediates. This talk will describe these findings and further explore the potential of isotope labeling studies in electrocatalysis.
[1] D. B. Trimarco, S. B. Scott et al, Enabling real-time detection of electrochemical desorption phenomena with sub-monolayer sensitivity. Electrochimica Acta. 2018, 268, 520-530
[2] C. Roy, B. Sebok, S. B. Scott et al, Impact of nanoparticle size and lattice oxygen on water oxidation on NiFeOxHy. Nature Catalysis. 2018, 1(11), 820–829

Figure 1
Functionalized Phosphorene Quantum Dots As Efficient Electrocatalyst for Oxygen Evolution Reaction
Authors: Prasannachandran Ranjith , Vineesh Thazhe Veettil , Anil Athira , Krishna B Murali , Shaijumon Manikoth M 
Published: February 2020

Two-dimensional layered materials[1] have been of great interest due to their unique physico-chemical properties and wide range of applications. Wide interest in exfoliated 2D layered materials such as graphene[2] and transition metal dichalcogenides (TMDs) motivated scientists to explore similar layered materials and, phosphorene, a layered counterpart of black phosphorous[3], has attracted lot of attention in recent times. The high air sensitivity and chemical reactivity of mono/few-layered phosphorene remain a big challenge in its synthesis and further applications. Here, a novel strategy for controlled synthesis and in situ surface functionalization of phosphorene quantum dots (PQDs) using a single step electrochemical exfoliation process from bulk black phosphorous crystals is demonstrated. Further, our results prove promising potential of phosphorenes as technologically viable OER electrodes for water splitting devices.

Keywords: Phosphorene; Electrochemical synthesis; Oxygen Evolution Reaction

References

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[3] L. Kou, C. Chen, S. C. Smith, The Journal of Physical Chemistry Letters
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