bluuebunny/crossref_metadata_2025_split huggingface dataset:
Voltammetric Reduction of Organics at Poly-Para-Aminophenol Modified Graphite Electrodes
Authors: Haque Inam ul , Bano Kiran , Tariq Muqaddas 
Published: February 2020

Polymer coated graphite electrodes were obtained by reductive electro-polymerization of para-aminophenol in 1.0 M nitric acid. Linear sweep voltammetry was employed to investigate electrolytic reduction of nitrobenzene and acetone at these electrodes, Figures 1 and 2. Suitability of the electrodes for analytical determination of these compounds is demonstrated.
References
L. I. Halaoui, H. Sharifian, and A. J. Bard, J. Electrochem. Soc., 148, E386-E393 (2001).
I. U. Haque, K. Bano and S. Iqbal, J. Chem. Soc. Pak., 32, 717-723 (2010).
I. U. Haque and K. Bano, Sci. Int. (Lahore), 24, 415-419 (2012).

1IUH Presently at J-263 Phase-I Defence Housing Authority Lahore 54792 Pakistan

2KB Presently at School of Chemistry Monash University Clayton Victoria 3800 Australia
Study on Horn-Shaped Polypyrrole Electrodes Prepared By Pulse Potential
Authors: Li Li , Wang Jingping 
Published: February 2020

Recently, many research in alternative biopotential sensor technologies for electrocardiograms (ECG) and electroencephalograms (EEG) applications was carried out due to skin irritation or inflammations often caused by the conventional Ag/AgCl electrode. The electrode material is a key to development of new biopotential sensor. Polypyrrole (PPy) is considered as one of most potential electrode material for biopotential sensor and artificial muscles due to its high electronic conductivity, long-term environmental stability, environmental friendliness and the relatively easy synthesis process. The preparation of PPy electrode by electrochemical method offers several advantages including high conductivity, easy controllability of its thickness and morphology However, this method does not provide horn with high distribution density on the surface of PPy film. Thus, further development of this method is needed.
Polypyrrole (PPy) films were prepared by direct current (DC), pulse current (PC) and pulse potential (PP) in aqueous solutions. The scanning electron microscope (SEM) images of PPy films indicated that a lot of horn-shaped PPy was formed during PP-PPy polymerization process. The top-end of horn-shaped PPy exhibits both open and closed structures. The body of horn-shaped PPy has a hollow structure with a thin wall. The micelles composed by PPy monomer and p-toluenesulfonate anions (PTS-) was formed when pyrrole monomer was dispersed in aqueous solution containing PTS- anions by mechanical stirring. In PP polymerization, the micelles with negative charge were repelled and hence leave the surface of PPy films at switch off time. As a result, the PTS- anions on the surface of micelles were effectively supplied, and thus stabilized the micelles. This process results in the continuous growth of horn-shaped PPy. The hollow horn-shaped PPy films showed big specific capacitance, high charging/discharging rate and better stability.
Graphene-Based Hybrid Materials Incorporating Multichromophores
Authors: Economopoulos Solon P. , Tagmatarchis Nikos 
Published: February 2020

Hybrid materials based on graphene have the potential to drive a variety of nanotechnological applications ranging from optoelectronics, to biomedical, as well as, industrial. Herein, we present an array of novel graphene-based materials incorporating one or more chromophore systems, anchored onto graphene through covalent or non-covalent interactions, targeted for energy conversion schemes.
Graphene single- and/or few-layered graphene sheets have been prepared through ultrasonication processes, introducing minimal defects onto the graphitic backbone while affording comparatively large quantities to allow for chemical modification.1 The chromophores selected to form hybrid graphene nanoensembles, through covalent bond formation, range from pyrene, porphyrin and oligo-thiophene adducts.2 The resulting hybrids afforded stable suspensions in a variety of common organic solvents and allowed for detailed characterization in liquid phase. In addition, non-covalently formed graphene-based nanoensembles were also prepared and the various systems comprised of thiophene chromophores, but also pyrene-porphyrin and dual porphyrin systems.2

All synthesized hybrids have been extensively characterized with thermogravimetric analysis, microRAMAN, and optical techniques (absorption, steady state and time-resolved photoluminescence spectroscopy) among others to verify, the structural and optoelectronic properties of the nanoensembles. Also due to the increased solubility of the hybrids and the ability to form stable suspensions, electrochemistry was used to elucidate the energy levels of the chromophores, as well as the resulting hybrids, affording insight on the thermodynamically favored mechanisms in the system. Finally, time-resolved photoluminescence experiments verify the promotion of electronic communication of the chromophores with the graphene substrate.
Financial support from GSRT/NSRF 2007-2013 through action “Supporting Postdoctoral Researchers” project GRAPHCELL PE5(2126) is acknowledged.
References

S. P. Economopoulos, N. Tagmatarchis, Chem. Eur. J. 2013, 19, 12930.

S. P. Economopoulos, N. Tagmatarchis, Manuscript in preparation, 2014.
Synthesis and Characterization of Graphene-Polyaniline Composites Preparated in Site for Fuel Cell Applications
Authors: Pereyra Elsa , Menchaca Carmina , Cano Ulises , Albañil Loyda , Guardian René , Uruchurtu Jorge 
Published: February 2020

Keywords: graphene, polyaniline, fuel cells.
Fuel cells have been attracting increasing attention in recent decades due to the high energy demands, fossil fuel depletion and environmental pollution throughout world. However there are still challenges to implement sources and alternative fuels, as in the case of fuel cells: raise increase production cell voltage and reduce material costs and corrosion.
This work focuses on the study of a graphene / polyaniline composite that can be used to improve the efficiency of the electrode in a fuel cell. Graphene alone is a good conductor material with high surface area, however to create a polyaniline intrinsic polymer composite, improvement is expected in their charge-transfer properties.
Two different synthesized graphene as a conductive material, were formed by electrochemical synthesis or modified Hummer method in different particle sizes, and were characterized to study their behavior.The experimental development was carried out by depositing graphene oxide films on a brass plate. The synthesis of polyaniline (PANI) was in situprepared through polymerization of aniline in the presence of graphene or grapheme oxide
The morphology and structure of the material were characterized by scanning electron microscopy (SEM), infrared spectroscopy (IR) and X-ray diffraction (XRD). The electrochemical properties of the resulting materials were systematically studied using cyclic voltammetry (CV), as well as evaluation by electrochemical impedance spectroscopy. Good behavior was observed. The conductivity was also influenced by the particle size of graphene and the improvement is attributed to the fact that graphene not only serves as a highly conductive support material, but also provides large surface for PANI. High conductivity and large specific surface area greatly improve the charge transfer efficiency, providing good corrosion protection to the metal substrate.
SOI and Bulk FinFET Alternatives from the Perspective of Strain Engineering
Authors: Peidous Igor V , Lottes Charles , Jost Christopher 
Published: February 2020

Fabrication of MOSFETs with mechanically strained channels has been an effective means for enhancing transistor drive currents and improving performance of CMOS circuits. FinFET devices appear to suit best for leading-edge ULSI and may be scaled to satisfy the requirements of 10 nm technology generations and beyond. There are two generic options for FinFET implementation – SOI and Bulk. The effectiveness of FinFET strain engineering is one of the decisive factors for selecting a preferred FinFET option.
The purpose of the present work is to provide an insight into the stress states of strain-engineered SOI and Bulk FinFETs. The results of computer simulations quantifying the stress effects on carrier mobility in FinFETs of different geometries and channel orientations are presented. The modeling was performed using a specially developed 2D FEM algorithm that enabled fast turnaround in conducting numerous iterative simulation experiments.
The obtained results show that embedded SiGe stressors (eSiGe) formed in Source/Drain areas of FinFETs are the key element for enhancing drive currents of PFETs to the level comparable with NFETs. However, due to the differences in transistor architectures, the stress induced by eSiGe in SOI FinFET channels and the corresponding change of the carrier mobility is about 2 times lower than that in bulk FinFETs. On the other hand, SOI offers a higher degree of freedom for stress engineering to compensate eSiGe deficiency. SOI FinFET designers may consider alternative crystal orientations for Fins, strained SOI, and low-defect Ge or III-V semiconductors on insulator.
The Dual-Heterojunction Ge on Si Photodetector
Authors: Sahni Subal , Hon N. K. , Masini Gianlorenzo 
Published: February 2020

Metal contact plugs are today commonly used to establish electrical connection to the anode and cathode electrodes of Ge on Si integrated photodetectors. While large progress has been made in optimizing these contacts, scattering loss at the metal regions still remains the most important efficiency-limiting factor. In addition, the process used to form the contacts is challenging because of the relatively high attack rate of Ge in aqueous solutions. In this paper an alternative way of building and contacting a Ge diode is presented: leveraging the presence of the Si substrate, highly doped n- and p-type regions are formed on the sides of the Ge region. These both serve establishing the built in potential in the diode as well as offering a low resistance path for the photocurrent extraction. Devices built using this approach match and sometime exceed the performance of the classic “PIN” homojunction ones.
In this paper experimental results from a number of dual heterojunction Ge on Si devices based on the LuxG process (Luxtera’s integrated sislicon photonic process) will be presented and discussed.
Electroformation of Guvs on Microchip with Coplanar Microelectrodes
Authors: Wang Qiong , Yang Jun , Liao Yan-jian , Hu Ning , Luo Hong-yan 
Published: February 2020

Recently, microfluidic chip with coplanar microelectrodes is generally used in cell electrofusion and electroporation, it is also more and more popular in the electroformation of giant unilamellar vesicles (GUVs). Higher yield and more uniform size distribution of GUVs can be formed between coplanar microelectrodes than those on conventional devices.
In this study, microchips with planar-comb teeth (PCT), symmetrical comb teeth (SCT), and interdigital comb teeth (ICT) coplanar microelectrodes are used to carry out electroformation of GUVs to compare the impact of different configurations. COMSOL Multiphysics software is used to simulate distributions of the electric field and electroosmotic flow (EOF). Horizontal and vertical electroformation chamber are also simulated. Simulation results show that the electric field and EOF distribution of coplanar microelectrodes are quite different from the traditional 3D chips. In addition, ICT gets better EOF distribution than PCT and SCT.
On-chip experiments show that high yield and uniform size distribution of GUVs can be achieved on these new chips as existing devices based on coplanar microelectrodes. Moreover, the size distribution of GUVs is narrowed from several to hundreds of microns (in traditional methods) to several to several ten of microns. As the simulation results proved, lipid vesicles on a microchip with ICT get a more uniform size distribution.
Study on Processing Technique of 3-D PDMS-Ag Composite Microelectrodes Integrated in Microfluidic Systems
Authors: Jiang Fan , Zheng Xiao-lin , Chen Li , Zhang De-yan , Hu Ning , Liao Yan-jian , Luo Hong-yan 
Published: February 2020

Benefited from the development of soft lithography technology, the material polydimethylsiloxane (PDMS) has been widely used serving as a unique material in chip fabrication owing to its properties such as transparency, biocompatibility, and good flexibility. However, PDMS itself is a non-conducting polymer, and the adhesion between metal and PDMS is really weak. Hence, integrating metallic microelectrodes with PDMS-based microchips structures has become an urgent technical issue.
To overcome this problem, we present a method of patterning 3-D microelectrode structures by using a new kind of conductive composite, synthesized by mixing Ag powders with pure PDMS gel. The advantage of this material is the ease of patterning and embedding these microstructures into PDMS-based channels. Compared with other conventional 3-D microelectrode preparations, the technological process was greatly simplified and the cost was effectively reduced.
In this paper, first, the dimensional electric field distributions induced by sidewall electrodes was simulated. Furthermore, we designed a dentate electrode array based on PDMS-Ag conductive composites for cell electrokinetic operations. Integrating 3D-electrode structures into microchips, chip package and fabrication were accomplished by multiple exposures, developments and plasma bonding. The feasibility of electrodes was validated on cell alignment driven by dielectrophoresis force. The results obtained demonstrate that the method seems to be a valuable solution for 3-D microelectrode processing. It is also compatible with existing micro-processing technology with much simpler operations. Thus, we aim at highlighting the promising prospects of this conductive composite material in microfluidic devices.
Interface Investigations and Bulk Behaviors of an All-Solid-State Lithium Microbattery By Means of Electrochemical Impedance Spectroscopy
Authors: Larfaillou Séverin , Guy-Bouyssou Delphine , Le Cras Frédéric , Franger Sylvain 
Published: February 2020

Constant miniaturization of electronic devices leads nowadays to the conception of smaller batteries. In this domain, using an all solid state thin film technology has many advantages over conventional lithium cells. These microbatteries are thin, bendable, with a long service lifetime and can also be produced with customizable shapes for better integration in electronic devices. Moreover, without liquid electrolyte, they are safe and comply well with environmental standards. Unfortunately their design and relative small dimensions imply some difficulties to accurately characterize them (from a physico-chemical point of view) without damages.
This paper will present the use of Electrochemical Impedance Spectroscopy to understand the behavior of thin film batteries built by stacking several active layers thanks to physical vapor deposition technics (with LiCoO2 as positive electrode, lithium phosphorus oxynitride vitreous glass as electrolyte (LiPON) and lithium metal as negative electrode). The first step of this study was to distinguish the impedance response between each individual active layer and interface by testing different systems. Metal-insulator-metal stack let us access to the ionic transport properties in LiPON [1]. Half-cells composed with electrolyte and LiCoO2 or lithium, give us information about the electrolyte/active material interfacial behavior. At last, the insertion electrode bulk electronic conductivity can be obtained with a Pt/LiCoO2/Pt symmetrical cell. Thanks to all these results it is thus possible to determine an electrical equivalent model for the complete battery. The model is composed of serial contact and collector resistivity (A), bulk electrolyte (B), capacitance and resistance interfaces (C, D), semi-infinite diffusion in LiCoO2 (E) and charges accumulation phenomena (F).
The Second step was to explain the reasons for spectrum evolutions in function of state of charge, aging or other external conditions. EIS was systematically performed after battery manufacturing and after aging, from 1 MHz to 50 mHz and between 3V and 4.2V. The most obvious observation is the evolution of the “D” contribution with cell potential. Iriyama et al. already attributed it to the charge transfer process at the LiCoO2/LiPON interface [2]. But after aging a new potential dependent R//C contribution appears and could correspond to bulk phenomena in the insertion electrode created by crystalline evolution during aging.
To conclude, thanks to electrochemical impedance spectroscopy, we will propose an electrical equivalent model of the operating microbattery to predict its evolution, failure and aging.

[1] X.Yu, J. Bates, G. Jellison anf F. X. Hart, J. Electrochem Soc., 144, 524 (1997)

[2] Y. Iriyama, T. Kako, C. Yada, T. Abe and Z. Ogumi, Solid State Ionics, 176, 2371 (2005).
Innovative Solutions to Materials Challenges for High-Voltage SiC Power Devices
Authors: Gaskill D. Kurt , Myers-Ward R.L. , Klein P.B. , Mahadik N.a. , Stahlbush R.E. , Eddy C.R. 
Published: February 2020

Silicon carbide (SiC) is a material of interest for high-temperature, high-voltage and high-power switching device applications. Key materials challenges inhibiting such devices include elimination of basal plane dislocations (BPDs) and enhancement of minority carrier lifetimes in the drift or blocking regions of the device. Recent progress in addressing both of these issues is presented.
BPDs are a major concern for the SiC bipolar devices required for high-voltage applications as they source Shockley-type stacking faults in the presence of an electron-hole plasma and reduce minority carrier lifetimes. Many methods have been investigated to reduce the BPD density including pre-growth treatments, substrate orientation, growth parameters and growth interrupts. It has been shown that the conversion of BPDs to threading edge dislocations (TEDs) continues throughout the epitaxial growth process in 4° off-axis SiC material and that a minimum thickness of ~16 µm is required to convert all BPDs to TEDs. Here we show that optimizing a hydrogen etch of the substrate prior to epitaxial growth significantly enhances conversion efficiency in a thin highly doped n+ buffer layer (BL). IN this work, epitaxial layers were grown on 4° off-axis substrates in an Aixtron/Epigress VP508 horizontal hot-wall reactor using the standard chemistry of silane (2% in H2) and propane.
In addition, using various growth approaches, low-doped epitaxial layers of only 20 µm in thickness on a 5 µm highly doped buffer layer have demonstrated minority carrier lifetimes up to 4 µs, as measured by time resolved photoluminescence, without any pre- or post- processing treatment. Interface recombination likely dominates these measurements. We extend this approach by presenting new data investigating the non-uniformity of lifetime found on as-grown material under various conditions.
This work is supported by the Office of Naval Research
Study of Ti-Rich and Al-Rich Contact Metallization for AlGaN/GaN HEMT Power Devices
Authors: Bertrand Dimitri , Fayolle Murielle , Blanquet Elisabeth , Torres Alphonse , Volpi Fabien 
Published: February 2020

AlGaN/GaN heterostructures have great potential for high-power applications due to their material properties: wide band-gap, high electron mobility in a 2D electron gas and high breakdown field. Low resistance ohmic contacts are required to benefit from the full advantages of the high-electron-mobility-transistor (HEMT) structure. A choice of metallization in agreement with the CMOS-industry standards (i.e. without Au) is required to facilitate the industrialization of such devices. Hence, a Ti/Al stack is a viable solution. Realization of low resistive ohmic contacts is very sensitive to Ti/Al composition and annealing temperatures [1-2]. Understanding metallurgical mechanisms is crucial to optimize the contact.
This work is focused on the study of the Ti/Al metallization and the reactions occurring during a two-steps annealing (300s at 600°C then 60s at 900°C in N2 ambient) in both Ti-rich and Al-rich cases. Two Ti/Al stacks, Al-rich (75/225 nm) and Ti-rich (95/200 nm) have been studied first on Si3N4/Si substrates in order to observe only the Ti+Al reactions and eventual nitridation. Then, the best promising stack (the Ti-rich one) has been transferred on AlGaN substrate. Characterizations consist in AFM, sheet resistance (R), XRD (Fig.1) and cross-section SEM (Fig.2.a) & STEM-EDX measurements (Fig.3). Thermodynamics study has been performed to follow the material behavior.
Regarding the Al-rich stack, XRD peaks (Fig.1.a) prove the formation of TiAl3 at 600°C. This is confirmed by the R value (570 mW) corresponding to a resistivity close to the TiAl3 one (respectively ~20 and 17 µW.cm). At 900°C, R reaches a very resistive value (>8 W) and voids can be identified on SEM images above the remaining TiAl3 (Fig.2.a). XRD reveals the presence of AlN (Fig.1.b) probably formed by the nitridation of Al in excess during the annealing by the N2. This is consistent with the ternary diagram of the Ti-Al-N system (Fig.2.b).
Regarding the Ti-rich stack, XRD graph (Fig.1.c) demonstrates the formation of TiAl3 and a Ti-rich phase at 600°C. At 900°C, XRD reveals the presence of a titanium nitride phase in the contact. This probably results from the reaction of Ti-Al stack with the Si3N4substrate.
The Al-rich metallization creates a thick and resistive layer on top of the stack which is not suitable for achieving low resistive contacts. At the opposite, the Ti-rich metallization allows formation of a titanium nitride layer involving the substrate, a key-reaction for achieving ohmic contacts. Hence, we transferred on AlGaN substrate the Ti/Al 95/200nm stack. Same methodology using also cross-section STEM+EDX (Fig.3) has been applied to complete the scenario of reactions between the Ti/Al stack and AlGaN substrate.

References

[1] B. Jacobs et al., J. Cryst. Growth 241, 15 (2002)
[2] H-S. Lee et al., IEEE Electron Device Lett. 32, 623 (2011)

[3] Q. Chen, B. Sundman, J. Phase Equil. 19, 146 (1998)