bluuebunny/crossref_metadata_2025 huggingface dataset:
New, Novel Al2-XHfxO3 Materials for M O S Application
Authors: Mahat Annie Maria , Kamarulzaman Norlida , Badar Nurhanna
Published: February 2020

In this work, new, novel materials of Al2-xHfxO3 have been successfully obtained via a self-propagating synthesis method. Results from X-ray diffraction (XRD) confirm that all samples were pure. Quantitative analysis from Reitveld refinements have shown an accurate results of hafnium (Hf) inclusion in the Al2O3 hexagonal crystal lattice. Morphologies of pure Al2O3 and Al2-xHfxO3 materials were studied by scanning electron microscope (SEM). The Hf content were confirmed via energy dispersive X-ray (EDX) and the values obtained were identical to the synthesized values. UV-visible spectroscopy showed that Al2-xHfxO3 materials exhibited band gap narrowing with respect to pure Al2O3 material. Band values were also dependent on Hf content.
(Invited) Energy Efficient Transistors with 2D Materials
Authors: Rahman Rajib , Ilatikhameneh Hesameddin , Ameen Tarek , Klimeck Gerhard
Published: February 2020

Emerging two-dimensional materials provide new opportunities to design post-Moore’s Law devices due to their atomically thin dimensions, layer dependent band gaps and effective masses, large density of states, and exotic band structures. Novel designs for energy efficient steep subthreshold swing transistors are investigated in 2D materials, highlighting the material and device properties that optimize the metrics needed to compete with CMOS. Based on atomistic non-equilibrium Green’s function simulations, the device characteristics of various 2D material tunnel field effect transistors (TFET) [1] are compared. Since chemical doping of 2D materials is still a challenge, we outline design considerations for generating electrostatic p-n junctions. Since low On-currents are a major challenge in TFETs, we show how On-currents and energy-delay products can be improved significantly in both chemically and electrically doped 2D TFETs. We also present a new design for an electrically doped 2D TFET, which uses a combination of high and low k dielectrics to achieve high On-currents [2]. We also highlight that the material properties of few-layer Phosphorene/Black Phosphorus make it an ideal candidate for low power TFETs.

To replace CMOS transistors, TFETs need to achieve simultaneous supply voltage and channel length scaling. We show how the performance of a TFET degrades as the channel length is scaled. To solve this issue, effective masses and bandgaps need to be engineered according to some predicted conditions. We show that 2D materials such as Phosphorene help channel length scaling in TFETs compared to III-V TFETs. We also propose a novel design for a Phosphorene TFET using an L-shaped gate, which utilizes the large anisotropic effective mass of Phosphorene to improve On-currents and to suppress Off-state leakage [3]. Such a TFET also helps channel length scaling down to 2nm channels [4].

This research is supported by Semiconductor Research Corporation’s LEAST center.

H. Ilatikhameneh et al, IEEE J-EDS Vol. 4, Issue 5, 260-265 (2016).

H. Ilatikhameneh et al, IEEE EDL Vol. 36, No. 10, 1097-1100 (2015).

T. A. Ameen et al, Scientific Reports 6, 28515 (2016).

H. Ilatikhameneh et al, Scientific Reports 6, 31501 (2016).

Figure 1 a) Design of an L-shaped gate in a Phosphorene TFET. b) The current-voltage characteristics of planar gates along armchair and zigzag directions compared to that of the L-shaped gate.

Figure 1
(Invited) Phase Change Materials-based Synaptic Devices for Energy Efficient Implementation of Learning in Hardware
Authors: Shi Yuhan , Kuzum Duygu
Published: February 2020

The biological brain has the capability of learning, pattern recognition, processing imprecisely defined data and executing complex computational tasks. Consisting of 1011 neurons and 1015 synapses as the major computational components, the biological brain is extremely power efficient, massively parallel, structurally plastic, and exceptionally robust against noise and variations. Development of efficient electronic synapses is essential for building large-scale neuromorphic systems. In this talk, we will present synaptic devices based on phase change memory (PCM). We will first explain basics of phase change synaptic devices: device operation, phase change materials, conduction mechanism, power consumption and scaling. We will then discuss the use of PCM for synaptic device implementations spanning from single device operation to various array architecture designs. The concept of spike timing dependent plasticity (STDP), various pulse scheme designs, and pulse programming techniques for plasticity will be explained. Last, we will present implementation of learning using PCM crossbar arrays.
Advanced Catalysts Used in Redox Flow Batteries
Authors: Li Bin , Nie Zimin , Kizewski James , Duan Wentao , Wang Wei , Reed David , Sprenkle Vincent
Published: February 2020

Redox flow batteries (RFBs), as one of the most promising electrical energy storage systems, provide an alternative solution to the problems of balancing power generation and consumption. RFBs are designed to convert and store electrical energy into chemical energy and release it in a controlled fashion when required. In particular, aqueous RFBs are attracting more attentions because of their good safety, low cost and high power density comparing with non-aqueous RFBs. Therefore, aqueous RFB chemistries with appropriate redox potential, high soluble and low-cost active species are critically required.[1]

During the past few years, PNNL invented several aqueous RFB systems, including mixed acid vanadium flow battery (VRB)[2]and zinc-polyiodide redox flow battery (ZIB)[3]. It is well known that high charge/discharge rate (charge/discharge current density) is prone to generate high power density, but the energy efficiency (EE) would be significantly declined. The low EE means that more active species are required for identical energy output, which eventually results in increased cost. In order to increase EE especially at higher current density, much attention has been paid on the improvement of electrodes. Commonly, carbon-based materials are used as electrodes in both VRBs and ZIBs because they are readily available, highly stable, corrosion resistant, economical and conductive. However, they were proved to show poor kinetic reversibility. Although noble metal catalysts such as Pt, Au, Ir, and Pd were coated or dispersed onto the carbon surfaces so as to improve the electrochemical activity of active species, the high cost still restricts their commercial application. Here, we will present our development at PNNL on low-cost and highly active catalysts, such as metal (Bi)[4], metal oxide (Nb2O5)[5], carbon oxygen functional groups[6] as well as metal-organic frameworks[7], used in VRBs and ZIBs, greatly enhancing the electrode performances. The corresponding mechanisms will be discussed in detail. 

.

References:

Li, B et al. L. National Science Review (2017): in press

Li, L et al. Advanced Energy Materials 1.3 (2011): 394-400.

Li, B et al., Nature communications, 2015

Li, B et al. Nano letters 13.3 (2013): 1330-1335.

Li, B et al. Nano letters 14.1 (2013): 158-165.

Li, B et al. ChemSusChem 9.12 (2016):1445-1461

Li, B et al., Nano Letters, 16. 7 (2016): 4335-4340
Dissection of the Voltage Losses of an Acidic Quinone Redox Flow Battery
Authors: Aziz Michael J. , Chen Qing , Gerhardt Michael R.
Published: February 2020

We measure the polarization characteristics of a quinone-bromide redox flow battery with interdigitated flow fields, using electrochemical impedance spectroscopy and voltammetry of a full cell and of a half cell against a reference electrode. We find linear polarization behavior at 50% state of charge all the way to the short-circuit current density of 2.5 A/cm2. We uniquely identify the polarization area-specific resistance (ASR) of each electrode, the membrane ASR to ionic current, and the electronic contact ASR. We use voltage probes to deduce the electronic current density through each sheet of carbon paper in the quinone-bearing electrode. By interpreting the results using the Newman 1-D porous electrode model, we deduce the volumetric exchange current density of the porous electrode. We uniquely evaluate the power dissipation and identify a correspondence to the contributions to the electrode ASR from the Faradaic, electronic, and ionic transport processes. We find that, within the electrode, more power is dissipated in the Faradaic process than in the electronic and ionic conduction processes combined, despite the observed linear polarization behavior. We examine the sensitivity of the ASR to the values of the model parameters. The greatest performance improvement is anticipated from increasing the volumetric exchange current density.

Figure 1
Incorporation of Conductive Internal Additives within Electrocuring Adhesives
Authors: Steele Terry WJ
Published: February 2020

Low-voltage activated adhesives have recently been invented, aka ‘voltaglue’, leading to electrochemically mediated adhesive curing (electrocuring)[1]. Consisting of new and established adhesive crosslinking groups, formulations incorporate dendrimers that have a preference of intermolecular crosslinking while allowing flexible incorporation of functional groups. Upon voltage activation, specific functional groups are activated and covalently bond to a variety of surfaces, but this is highly dependent on bulk conductivity.

To tailor the adhesive properties and adhesion strength, internal additives have been explored towards increasing conductivity and ultimately the ‘voltaglue’ crosslinking efficiency. Flexible electrocuring is sought to achieve a range of material properties, from viscous gels to hard set matrices. Ferrocene, a well-known redox active compound with reversible one-electron redox behaviour[2], is often incorporated in polymers/dendrimers due to its reversible nature and conductive aspects [3]. By integrating the ferrocene internal additive into dendrimer formulations combined with the electrically activated crosslinking additives we are able to mediate the electrocuring properties to a limited degree.

In this work we present the synthesis of PAMAM-g-ferrocene-g-diazirine, an electrocuring adhesive that is able to adhere to a range of substrates, with adhesive strengths at the kPa scale. Real time electrorheology measurements chemistry evaluate the range of material properties available and demonstrate the synergistic performance ferrocene internal additives impart on the ‘voltaglue’ adhesives.

 

 

References

 

[1] J. Ping, F. Gao, J.L. Chen, R.D. Webster, T.W.J. Steele, Adhesive curing through low-voltage activation, Nature Communications 6 (2015).

[2] M.E. N.P.R.A. Silva, A.J.L. Pombeiro, J.J.R. Fraústo da Silva, R. Herrmann, N. Deus, R. E.Bozak, Redox potential and substituent effects in ferrocene derivatives: II, Journal of Organometallic Chemistry 480 (1994).

[3] R. Gracia, D. Mecerreyes, Polymers with redox properties: materials for batteries, biosensors and more, Polymer Chemistry 4 (2013).

[4] C.M. Elson, M.T.H. Liu, C. Mailer, Electron-spin-resonance studies of diazirine anion radicals, Journal of the Chemical Society, Chemical Communications 7 (1986).
Dual Stage Sodium Thermo-Electro-Chemical Converter (Na-TECC)
Authors: Limia Alexander , Yee Shannon K.
Published: February 2020

The need for reliable and distributable energy is evident, but one prominent obstacle is the lack of an efficient direct heat-to-electricity converter. The sodium thermo-electro-chemical converter (Na-TECC) is a highly efficient thermally regenerative electrochemical system (TRES) that can fill this void. This device uses an ion-selective solid-electrolyte called beta”-alumina that is highly conductive to sodium cations. The Na-TECC generates electric power by allowing high pressure sodium cations to expand isothermally through the solid-electrolyte. Theoretically, a device interacting with thermal reservoirs at 1150 K and 550 K should operate above 45% efficiency, but actual devices have not surpassed efficiencies of 20%. The maximum potential voltage in these previous devices was substantially reduced by the kinetic limitations of the charge transfer in the cathode, by pressure losses through the porous electrodes, and by Joule heating losses caused by the solid-electrolyte, electrode, and current collector resistances. To overcome these low efficiencies, a dual stage conversion process is being proposed. Rather than using one isothermal expansion step, the dual cycle will employ a second electrolyte to allow two separate expansion steps: one at the high temperature, and another at an intermediate temperature. This new cycle is thermodynamically favorable as it allows for regeneration from the isobaric cooling of the first expansion step, and reheat to complete the expansion in the second step. This allows the engine to reach a lower condenser temperature than its single stage counterpart for a given heat input, resulting in an increased overall efficiency. The temperature drop across each electrolyte in the dual stage device (e.g., ~ 400 K) is smaller than the temperature drop across a comparable single stage device (e.g., ~ 600 K). This makes the device amenable to better thermal management and allows for less heat loss. Also, the intermediate stage will mitigate the thermal shock across the very thin (< 1 mm) solid electrolyte, reduce crack propagation, limit the percolation of the molten dendrites, and ultimately increase the lifetime of the device. A dual stage concept for the Na-TECC has never been demonstrated in literature, so it is necessary to properly re-define the thermodynamic parameters such as heat loss, maximum power, and optimal current density. Certain drawbacks from a dual stage concept will also be addressed, such as the need for larger electrochemical area and the increased pressure losses. It will be demonstrated that the dual stage device must have lower thermal losses than a single stage device if it is to have a higher efficiency. The improved operation of the Na-TECC can have a transformational effect on small combined heat and power (CHP) systems at the 1-5 kW range.
Synthesis of Co-Ni-Mo As Non-Noble Electrocatalysts for Ethanol Oxidation
Authors: Chaitree Wasu , Kalu Egwu Eric
Published: February 2020

The high activity associated with platinum electrocatalyst for ethanol oxidation is tempered with its easy deactivation by CO species and its expensive nature as a noble metal. This work investigates the synthesis of highly active non-noble metal elctrocatalyst based on Cobalt (Co), Nickel (Ni), and Molybdenum (Mo) for ethanol oxidation. As-deposited Co-Ni-Mo electrocatalyst on carbon support was evaluated for ethanol oxidation. The electrocatalyst was prepared by electroless deposition method on carbon substrate support (CCS) made active for electroless deposition with Pd-ink. The effects of electroless deposition time, and reaction temperature (30-60°C) were studied. The result showed that CoNiMo/CCS was highly active in alkaline ethanol solution (0.5M NaOH+1 M EtOH) for ethanol oxidation. The temperature effect on the performance of the catalysts prepared at different times will be discussed. Although minor amount of Pd (< 50 μg/cm2) was used to make the carbon substrate active for electroless deposition, the results obtained showed that the Pd, was not utilized in ethanol oxidation. Therefore, the catalytic activity observed for the reaction is attributed to Co, Ni, and Mo, in the catalyst and not from Pd. Tafel analysis showed that the exchange current density for the catalyst prepared at 30 minutes deposition time was an order of magnitude higher than that reported for Pt (0.001´10-5A/cm2, [1]), and Pt/C (0.033´10-5A/cm2, [1]). This suggests that the catalyst has a better ability at handling CO deactivating species than Pt. Furthermore, the linearity of the peak potential with the logarithm of scanning rates confirms the irreversibility of ethanol electrooxidation . Overall, this study provides a promising novel and effective non-noble electrocatalyst with an onset potential of 0.05 V (Ag/AgCl).

[1]. Xu C, Shen PK, Ji X, Zeng R, Liu Y. Enhanced activity for ethanol electrooxidation on Pt–MgO/C catalysts. Electrochem Commun. 2005;7:1305–8.

Keywords: Cobalt, Nickel, Molybdenum, Electroless, Ethanol Oxidation, Tafel.
Enhancement of Low Level Dopamin Concentration Detecting Limit By Reducing Quantization Error
Authors: Kang Yumin , Shin Hojin , Oh Yoonbae , Park Cheonho , DeWaele Mark , Bennet Kevin E , Kim Inyoung , Lee Kendall H , Jang Dong Pyo
Published: February 2020

Fast scan cyclic voltammetry (FSCV) is a technique that measures the concentrations of neurotransmitters in vivo or in vitro. Conventional FSCV uses a triangle waveform, which starts from -0.4V, sweeps to +1.3V and returns to -0.4V. It makes not only a large background signal, but also a small signal from oxidation and reduction of a neurotransmitter. These large background signals can be removed by a background subtraction technique which extracts only the oxidation and reduction signals. After that, analyze the subtracted signal to estimate the concentration of the neurotransmitter. It has a limit in detecting low-level concentration of neurotransmitter because a large quantization error comes from the wide range of analog-to-digital convertor (ADC). To measure low-level concentrations of a neurotransmitter, the range of the ADC was decreased to lower the quantization error. Even though using a narrow range of ADC has a low quantization error, it cannot measure the whole voltammagram. For this reason, the waveform is changed for the background signal to become flat, where the oxidation signal arises, and move these flat sections to ADC-range using hardware subtraction. Eventually, we can measure the oxidation signal in a narrow range with low quantization error.
Tonic Dopamine Concentration Measurement Using Tailored Fscv
Authors: Cho Hyun-U , Oh Yoonbae , Shin Hojin , Park Cheonho , Kang Yumin , DeWaele Mark , Bennet Kevin E , Lee Kendall H , Jang Dong Pyo
Published: February 2020

Fast-scan cyclic voltammetry along with its background subtraction method has been widely used for detecting neurotransmitters in the brain. The most common application of FSCV is measuring phasic changes of dopamine (DA) in the brain evoked by an external stimulus. The background subtraction method has greatly improved FSCV’s application to the neuroscience field. However, tonic dopamine concentration, which is as vital as phasic change, cannot be measured even though the background is subtracted. In this study, we developed a tailoring FSCV technique which can manipulate the background current by modifying a waveform’s voltage points. By using the technique, the last background current generated by multiple waveform application is tailored to the front background current. As a result, background current is cancelled out by subtracting the tailored (last) voltammagram from the front voltammagram. Therefore, only the DA oxidation/reduction pattern still remained between front and last voltammogram, so that, tailoring FSCV can detect tonic DA concentration without background subtraction method.

The tailoring technique is evaluated by comparing it with commercialized enzyme-linked immunosorbent assay (ELISA) kits. By measuring endogenously released DA from DAergic cells, the tailoring method showed a significant correlation with ELISA results.
Amorphous Transition Metal Polysulfides As Electrode Materials for Li-Ion Batteries
Authors: Doan-Nguyen Vicky V. T. , Subrahmanyam Kota S. , Butala Megan M. , Gerbec Jeffrey A. , Islam Saiful M. , Kanipe Katherine N. , Wilson Catrina E. , Balasubramanian Mahalingam , Wiaderek Kamila M , Borkiewicz Olaf J , Chapman Karena W , Chupas Peter J , Moskovits Martin , Dunn Bruce S. , Kanatzidis Mercouri G. , Seshadri Ram
Published: February 2020

Sulfur cathodes in conversion reaction batteries operate by a different mechanism than that of intercalation materials, and they possess larger theoretical capacities. However, sulfur-based electrode materials suffer from parasitic polysulfide shuttling, which contribute to decreased capacity retention and cyclability. We demonstrate that porous transition metal polysulfide chalcogels achieve high gravimetric capacity as electrode materials for lithium-ion batteries. Transition metal polysulfide chalcogels are amorphous, and comprise polysulfide chains connected by inorganic linkers. The linkers appear to act as a “glue" in the electrode to prevent polysulfide shuttling. In particular, we examined 3d and 4d transition metal polysulfide chalcogels (M’M”Sx in which M is a transition metal) and their role in maintaining structural stability in the electrode. In the MoS3.4 case study, the Mo polysulfide chalcogels function as electrodes in carbonate– as well as ether–based electrolytes and achieve an initial gravimetric capacity of 600 mAh/g. We employ X-ray absorption spectroscopy and operando pair distribution function techniques to elucidate the structural evolution of the electrode. Raman and X-ray photoelectron spectroscopy track the chemical moieties that arise during the anion-redox-driven processes. We find the redox state of Mo remains unchanged across the electrochemical cycling even to 1 V and correspondingly, the redox is anion–driven. Porous chalcogels offer a new class of electrode materials for achieving high-capacity Li-ion batteries.
Data Science Tools for Incorporating Physics-Based Models into Analysis of Impedance Spectra
Authors: Murbach Matthew D. , Schwartz Daniel T.
Published: February 2020

Electrochemical impedance spectroscopy (EIS) is a widely used method for noninvasively characterizing many electrochemical systems – probing the physicochemical response at different timescales to provide insight into a wide range of kinetic, transport, and thermodynamic parameters. By fitting equivalent circuit analogs to experimental impedance spectra, lumped parameters (ohmic and charge transfer resistances, double layer capacitances, Warburg impedances, etc.) which contain information about the physicochemical properties of the system are extracted. While this usage of equivalent circuit models makes fitting the data straightforward, the lumped parameter nature of this process can lead to limitations on the information content and discriminatory power of these measurements.1,2 Moreover, while the extracted parameters are often used as inputs to complex physics-based models, the reverse flow of information – directly incorporating modeling insights into the analysis of experimental impedance spectra – remains challenging for many researchers using EIS.

Here, we present an open-source, web-based tool for easily integrating physics-based modeling into the analysis of experimental impedance data. Using a large dataset of simulated spectra across a well sampled physical range of model parameters, the best fit of an experimental dataset can be used to find parameter estimates for the model. This data driven approach enables a more robust method for finding parameter estimates than optimizing the model directly and visualizations of the resulting best estimates give researchers the tools to more deeply analyze their data. Interactive visualizations of the simulated spectra also make it possible to ask more insightful questions about the model itself. As an example, we present a dataset of impedance simulations from a pseudo 2-dimensional (P2D) lithium ion battery model3,4 and describe insights gained by incorporating this dataset into analysis of experimental battery impedance spectra. Finally, we discuss the tool as an extensible platform for adding additional modeling datasets and features from across the community and the role of open-source tools within electrochemistry.

References:

1. Fletcher, S. Tables of Degenerate Electrical Networks for Use in the Equivalent-Circuit Analysis of Electrochemical Systems. J. Electrochem. Soc.
141, 1823–1826 (1994).

2. Harrington, D. A. & van den Driessche, P. Mechanism and equivalent circuits in electrochemical impedance spectroscopy. Electrochimica Acta
56, 8005–8013 (2011).

3. Doyle, M., Meyers, J. P. & Newman, J. Computer simulations of the impedance response of lithium rechargeable batteries. J. Electrochem. Soc.
147, 99–110 (2000).

4. Meyers, J. P., Doyle, M., Darling, R. M. & Newman, J. The impedance response of a porous electrode composed of intercalation particles. J. Electrochem. Soc.
147, 2930–2940 (2000).
3D Microscopic Simulation of Mediator Supercapacitors
Authors: Wang Yuchen , Zhang Chen , Qiao Xiaoyao , Zhou Xiangyang
Published: February 2020

Supercapacitors (SCs) can reach a high specific energy (25-50 Wh/kg) by doping mediators in electrolyte contained in porous electrode structure. Mediators in electrolyte can be considered as redox materials to provide pseudocapacitance and to increase the conductivity of electrolyte. However, the charge/discharge behaviors of the mediators with respect to current and voltage are difficult to be resolved because of the complicated structure and charge/discharge kinetics of the electrode materials. In this work, a 3D microscopic model is established to investigate the roles of different components, especially mediators in charge/discharge processes. The microscopic model (Figure 1) is solved using COMSOL Multiphysics. Activated carbon, carbon fibers, mediators and polymer electrolyte are explicitly represented in this model. The simulation describes the process after applying a voltage on the mediator SC. During charging, electric current flows into the mediators at positive electrode and flows out from the mediators at negative electrode. The charge rate at electrical double layers is much faster than the charge rate for the mediator domains due to different charge storage mechanisms. The mediators can only store the charges at the certain potential range. With the increase of the mediator capacitance, the time to reach a stable state increases. The mediators can also affect the stable potential of the electrolyte. As such, the model can be used to design the composition of the mediator SCs and predict the effect of mediators on the performance of the mediator SCs. In addition, the information regarding the stable electrolyte potential vs. mediator capacitance can be used to choose the electrolyte with specific potential windows to avoid electrolyte degradation at electrode/electrolyte interface.

Figure 1
Ab Initio Simulation and Analysis of the Charge Couples in Rechargeable Batteries and Supercapacitors
Authors: Zhou Xiangyang , Wang Yuchen
Published: February 2020

According to a long existing theory by Conway, the strikingly difference between supercapacitors (including pseudocapacitors) and rechargeable batteries can be unified under an electrochemical adsorption on 2-D or quasi-2-D electrode structures. The battery-like and capacitor-like behaviours differentiate themselves by the interaction between the charge couples (a group of molecules, ions, radicles, etc.). In this work, ab initio atomistic methods were used to calculate the interaction energy of the charge couples in 4 systems. The first is RuO2 a typical redox system showing capacitor-like behaviour. The second is Prussian blue in an organic electrolyte. This is a redox system showing a battery-like behaviour. The third system is the anode of Li-ion battery or layered graphite with intercalation of lithium ion. The fourth is TiS2 with intercalation of lithium ion showing a capacitor-like behaviour. With these four systems one can see transitions between capacitor-like and battery-like behaviours with both redox and intercalation charging mechanisms. A hybrid classic/ab initio molecular dynamics procedure was adopted to evaluate the microstructure of the charge couples in the electrode/electrolyte systems. Then, a perturbation was applied to the systems and the total chemical energy was evaluated using ab initio methods. The interaction forces were evaluated by conducting differentiation of the chemical energy on spatial coordinates. The study demonstrates that interaction between the charge couples plays an important role in charge/discharge processes in electrochemical energy storage systems. Based on the results, a perspective for developing new electrochemical energy storage systems is provided.
Simulation of the Impact of the Loss of Contact Area in All-Solid-State Battery
Authors: Tian Hong-Kang , Qi Yue
Published: February 2020

Maintaining the physical contact between the solid-state electrolyte and the electrodes is important to improve the performance of the Li-ion battery. The initial interface contact depends on the fabrication process of the battery. Typically, the deposited thin-film battery would have better interface contact than the bulk-type (mixed powder) battery. Increasing the compression pressure during the fabrication process could lead to a better initial contact. On the other hand, the contact area would continuously lose due to the volume change of the electrodes during the cycling of the battery. 

To illustrate this problem, a 1-D continuum model was developed to simulate the discharging process of an all-solid-state Li-ion battery, which is composed of Li as the anode, LiCOO2 as the cathode, and Li3PO4 as the electrolyte. The parameters were taken from a thin-film battery model that has fitted to experimental data. We incorporated the effect of the imperfect contact into this model by assuming the current and Li concentration will be localized at the contacted area. We correlated the percentage of lost contact area with the discharging capacity and energy. We observed that the capacity and energy decrease with the loss of contact area and discharge rate. For example, when discharging at 1 C-rate, the capacity decreased 20% as the contact area losses 19.8%. At a higher discharging rate of 32 C, the capacity dropped quickly to be less than 20% when the contact area losses 1.52%. 

Since Li3PO4 and LiCOO2 are both ceramic materials and their initial contact area is non-perfect after the fabricating process. We applied the Johnson-Kendall-Roberts (JKR) model, which is appropriate for elastic deformation and adhesive contact, to estimate the applied pressure that can recover the loss of contact to the initial condition. We found that it is more effective to apply the pressure when the battery just starts to decay when the battery capacity loss is less than 10%. Therefore, in practical application, this model and method can be used to estimate the extent of the loss of contact area during the operation of the all-solid-state Li-ion battery, and further suggesting how much pressures should be applied to recover the capacity.
Codeposition of Nickel-Phosphorus Alloys Reinforced with Boron Carbide Microparticles: Direct and Pulse Plating
Authors: Bernasconi Roberto , Magagnin Luca
Published: February 2020

Hard chromium coatings are widely used nowadays due to their remarkable properties such as good corrosion and wear resistance, low friction coefficient and high hardness. The main problem associated however with hard chromium plating is that during the deposition of the coating hexavalent chromium ions may be released. These are extremely dangerous for human health, as they are carcinogenic. For this reason its use has been limited by European Union Restriction of Hazardous Substances Directive. For these reasons researchers are looking for a suitable alternative with characteristics comparable to those of Cr. Nickel-phosphorus alloys were codeposited with boron carbide particles. Two compositions of nickel-phosphorus, one presenting a low phosphorus content in the order of 4 % wt. and another one presenting a high phosphorus content of about 12% wt., were deposited from modified nickel Watt’s electrolytes using both direct and pulse plating. A strong influence of the deposition method was observed on the phosphorus content in the matrix and on the quantity of codeposited particles. Pulse plating was found to significantly increase both of them. Nucleation of the pure nickel-phosphorus alloy and the codeposit were studied using chronoamperometry and AFM in potentiostatic mode. An instantaneous nucleation mechanism was evidenced on iron and gold. Microhardness was measured and connected to the phosphorous and particle contents.
Pulse Reverse Electrolytic Stripping of Chrome Plate
Authors: Garich Holly , Snyder Stephen , Hall Timothy D , Taylor E. J. , Inman Maria
Published: February 2020

A strong desire exists from an environmental, health and safety perspective to eliminate hexavalent chromium during electroplating of protective hard chrome coatings used to enhance component wear resistance. However, toxic hexavalent chromium waste streams are also generated during repair and refurbishment of chrome components as the parts are electrolytically stripped of the existing chrome before being recoated and reinstalled into various systems. Furthermore, the chromate formed during stripping accumulates in the electrolyte, interfering with the process efficiency and damaging the base metal.

Faraday is working to develop an electrolytic stripping process intended as a drop-in replacement for the conventional stripping process. The process seeks to eliminate the formation of hexavalent chromium while maintaining the material properties of the underlying substrate.

Faraday will present work that demonstrates removal of chrome from high strength steel substrates using a weak acid electrolyte that doesn’t produce hexavalent chromium or adversely affect the substrate properties. Furthermore, the effect of pulse and pulse/reverse electric fields on the efficacy of the stripping process will be presented.
(Invited) Structural Evolution of Hafnium Methacrylate Nanoclusters Following Electron-Beam Irradiation from in Situ ir Spectroscopy
Authors: Mattson Eric , Rupich Sara , Cabrera Yasiel , Chabal Yves J
Published: February 2020

High absorption metal and main group oxide nanoclusters have recently become the subject of intense investigation due to their potential as alternatives to conventional organic chemically amplified photoresists for negative tone patterning in the extreme ultraviolet (EUV) range. It is believed that the low energy secondary electrons generated from photoionization of the nanoclusters are responsible for the chemistry that occurs following irradiation. Despite their potential, little is known about many aspects of their function as resist materials; in particular, the role of high absorption elements in the absorption/photoionization process, the role of electrons of different energies, the formation of radicals and chemically reactive species and the overall structural changes that occur at each stage of processing. Thus, the precise atomic mechanism underlying solubility switching upon irradiation remains unknown. We have investigated one such class of materials: nanoclusters based on a hafnium oxide core decorated with methacrylic acid ligands (HfMAA) , using a combination of in situ infrared (IR) spectroscopy and x-ray photoemission spectroscopy (XPS). Thin films (10-30 nm) of the HfMAA nanoclusters deposited onto SiO2 from solution are characterized by XPS and IR spectroscopy in conjunction with density functional calculations. The mechanisms of solubility switching following EUV exposure are investigated using irradiation with low energy electrons to emulate the photoexcited carriers generated in the EUV absorption process. Using in situ IR spectroscopy, we are able to monitor the structural evolution of the nanoclusters at each stage of processing, beginning from the initial deposition to post application bake (PAB), electron irradiation, post exposure bake (PEB) and development. Monochromatic electron beams with energies ranging from 5 eV up to the typical EUV wavelength of 92 eV enable a correlation between the role of secondary electron energy with chemistry and functional character. In conjunction with XPS analysis, these measurements detail the structural evolution of the films under typical processing conditions, providing insight into the solubility switching mechanism of this emerging class of inorganic photoresists.
(Invited) Applying Energy Storage to Tune the Magnetism of Large-Pore Ordered Mesoporous Metal Oxide Thin Films
Authors: Brezesinski Torsten
Published: February 2020

Polymer-templated mesostructured non-silicate oxide thin films have received much attention in the past on account of their potential for future device applications. However, despite the overall progress made in the synthesis of such materials, “complex” metal oxides are more often than not ill-defined from a structural point of view. The primary reasons are the lack of control over the hydrolysis and condensation reactions of the inorganic precursors used, and the fact that the crystallization of the nanoscale walls is difficult to control. In this talk I will describe the evaporation-induced self-assembly synthesis of cubic mesoporous La1–xCaxMnO3 (LCMO), La1–ySryMnO3 (LSMO) and LiFe5O8 (LFO) thin films using a polyisobutylene-block-poly(ethylene oxide) diblock copolymer as the structure-directing agent. Electron microscopy, GISAXS, XRD, XPS, RBS and SQUID magnetometry all show that these materials are of high quality and thermally stable to over 600 °C. More importantly, they can store charge by topotactic lithium insertion reaction (LFO) and via double-layer capacitance (LCMO/LSMO), which allows for the intriguing possibility of reversibly tuning the magnetization [1, 2]. Collectively, I will show that both approaches provide a method to exert fine control over magnetism in situ, and further might help to better understand (Faradaic) surface charge storage processes.

[1] C. Reitz, P. M. Leufke, R. Schneider, H. Hahn, T. Brezesinski, Chem. Mater. 26 (2014) 5745.

[2] C. Reitz, C. Suchomski, D. Wang, H. Hahn, T. Brezesinski, J. Mater. Chem. C 4 (2016) 8889.
Highly-Ordered Growth of Solution-Processable ZnO for Thin Film Transistors
Authors: Buckley Darragh , McNulty David , Zubialevich V.Z. , Parbrook Peter J. , O'Dwyer Colm
Published: February 2020

Zinc oxide is an important optoelectronic material, of particular interest due to its wide band gap (Eg
~ 3.3 eV at 300 K), large exciton binding energy (~66 meV) and especially for the variety of methods by which it can be processed. Moreover, ZnO is readily able to alloy with other metals in the oxide form and has a lattice that can facilitate interstitial doping. This gives ZnO a key role in the area of optoelectronics, metal oxide thin films and thin film transistor (TFT) technologies.

We demonstrate that crystalline, epitaxial-like and highly ordered ZnO thin films can be achieved from a precursor liquid at relatively low temperature via spin-coating. The synthesised films are smooth, stoichiometric ZnO with controllable thickness. An iterative layer-by-layer coating schematic is employed to demonstrate the effects of film thickness on structure, morphology as well as the surface and internal defects. Characterisation of the crystallinity, morphology, O-vacancy formation, stoichiometry, surface roughness and thickness variation was determined through X-ray diffraction, scanning and transmission electron and atomic force microscopy, X-ray photoelectron and photoluminescence spectroscopy, and the data of multi-layered ZnO correlated to defect formation and electrical conductivity.

It is imperative that high crystal quality epitaxial-like thin films can be formed from solution processing to compete with physical deposition methods. We demonstrate that iterative spin-coating of deposited ZnO films results in a transition in crystal texture with increasing thickness (number of layers) from the [] m-plane to the [] c-plane. The films attain a c-axis preferential orientation, with no other crystalline peaks present. Results show that the film’s surface morphology was very smooth, with average rms roughness <0.15 nm. Examination of these films also shows the consistency of the surface composition and defect level while highlighting the
(Invited) Ethanol Photoreaction over Anatase TiO2(101) and Rutile TiO2(110) Single Crystals. A Combined STM and Online Mass Spectrometry
Authors: Idriss Hicham , Thornton Geoff , Harison George , Katsiev Habib , Algamdi Hamdan
Published: February 2020

The reactions of ethanol have been investigated over anatase TiO2(101) and rutile TiO2 (110) single crystals by STM and on-line mass spectrometry to determine the adsorbate species in the dark and post UV illumination, in the presence and absence of O2 or Au nanoclusters, in order to extract initial reaction parameters under photo-excitation. On anatase (101) TiO2 single crystal the reaction rate for the photo-oxidation of ethanol to acetaldehyde is found to be strongly dependent on O2 partial pressures and surface coverage with an order of the reaction for O2 close to 0.15. Carbon-carbon bond dissociation leading to CH3 radicals in the gas phase was found to be a minor pathway, which is contrary to the case of TiO2 rutile (110) single crystal, as previously reported by our group and others. Our STM images distinguished two types of surface adsorbates upon ethanol exposure that can be attributed to its molecular and dissociative modes. Upon UV exposure at (and above) 3×10-8 mbar O2, a third species is identified as a reaction end-product, which can be tentatively attributed to acetate/formate species, in line with XPS C1s measurements. The room temperature photo-oxidation of ethanol has also been investigated over a rutile TiO2(110) single crystal by STM and on-line mass spectrometry, in the presence of O2 to determine adsorbate species remaining post UV exposure and emitted gas phase products. In addition to acetaldehyde, methyl radical was detected in the mass spectrometry resulting from the photo-fragmentation of an acetaldehyde-O complex. Formic acid species bound to Ti5c in a bi-dentate mode were identified by STM on the surface after the reaction. The effect of O2 partial pressure on the reaction selectivity demonstrated a dominance of the photo-fragmentation process with increasing pressure unlike the case of anatase TiO2(101) single crystal. In addition the effect of Au particles on the reaction of the TiO2(110 rutile has been investigated for hydrogen production under photo-irradiation in UHV conditions. It was found that particle size in the range 4 to 8 nm do not change the reaction rate yet particle density does. Detailed reaction mechanism for both reduction and oxidation reactions are addressed based on structural and kinetic information from the UHV systems and compared to those of their corresponding powder forms in liquid-solid photocatalytic reactions conditions.
(Invited) Phase Transition and Related Energy Applications of (Hf,Zr)O2 Films
Authors: Park Min Hyuk , Hwang C. S.
Published: February 2020

A new ferroelectric phase (space group: Pca21) in (Hf,Zr)O2 thin film and doped/undoped HfO2 has been intensively studied since 2011.[1,2] The films could show large remanent polarizations (They are generally ~20 μC/cm2 and can be even larger than 40 μC/cm2 for La-doped HfO2) with extremely small film thickness (It is generally ~10 nm and can be even as thin as ~2.5 nm).[3,4] Moreover, they could endure more than 109 times of switching with the electric field of 2.5 MV/cm.[2] The Curie temperature of (Hf,Zr)O2 could be controlled by changing Zr:Hf ratio, and the (Hf,Zr)O2 films showed first-order like phase transition.[5] Interestingly, the two-step polarization switching could be observed in rather wide temperature range near room temperature for Hf0.4Zr0.6O2 film,[5] which could be observed in a very narrow temperature range for BaTiO3in a previous study.[6]

 The phase transition involved with the new ferroelectric phase is believed to be highly promising for various applications such as electrostatic supercapacitor, energy harvester, and electrocaloric cooler.[7-9] The Hf0.3Zr0.7O2 thin film could store electrostatic energy up to 46 J/cm3.[7] The temperature dependent change of polarization of Hf0.2Zr0.8O2 thin film could harvest electrical energy of 11.6 J/cm3 cycle from heat using Olsen cycle.[8] This also can be used for solid state cooling based on electrocaloric effect (The adiabatic temperature change was 13.4 K) when the inverse Olsen cycle is used.[8] It was suggested that a monolithic device with aforementioned various functions can be achieved on Si substrate.[8] In 2016, the giant negative electrocaloric effect (The adiabatic temperature change was -10.8 K.) in Hf0.5Zr0.5O2 film was also reported based on the abnormal pyroelectric properties.[9] It is expected that the combination of giant positive and negative electrocaloric effect in (Hf,Zr)O2films can make the solid state cooling device more efficient.[10]

 In this presentation, the fundamentals for phase transition in (Hf,Zr)O2films will be discussed based on the first-­order phase transition model involving the orthorhombic and tetragonal phases. The application of the phase transition behaviors for the various energy applications including energy storage/harvesting and solid state cooling will be presented in detail.

[1] T. Boescke et al. Appl. Phys. Lett. 99, 102903 (2011).

[2] M. H. Park et al. Adv. Mater. 27, 1811 (2015).

[3] J. Meuller et al. IEEE International Electron Devices Meeting (IEDM) (2013).

[4] A. Chernikova et al. ACS Appl. Mater. Interfaces 8, 7232 (2016).

[5] M. H. Park and H. J. Kim et al. Nanoscale 8, 13898 (2016).

[6] W. J. Merz, Phys. Rev. 91, 513–517 (1953).

[7] M. H. Park et al. Adv. Electron. Mater. 4, 1400610 (2014).

[8] M. H. Park et al. Nano Energy 12, 131 (2015).

[9] M. H. Park et al. Adv. Mater. 28, 7956 (2016).

[10] Li et al. Europhys. Lett. 102, 47004 (2013).
CMP: Consideration of Stop-on Selectivity in Advanced Node Semiconductor Manufacturing Technology
Authors: Tsai Stan , Amanapu Hari , Xie Ruilong , Zhang John , Chung Kisup , Labelle Cathy , Huang Haigou , Han Ja-Hyung , Koli Dinesh R , Surisetty Charan
Published: February 2020

In advanced node semiconductor manufacturing, Chemical Mechanical Polish (CMP) is a critical integration step to many modules, from fin formation, replacement metal gate (RMG), to interconnects. In each application, CMP’s stop-on capability is increasingly seen as an essential element in gauging device integrity, and thus is critical to the successful implementation of a technology. Traditionally, CMP selectivity is merely a characteristic of slurry chemistry and its abrasive materials, and is measured by blanket rates of the corresponding films. However, in advanced node semiconductor manufacturing, as feature sizes are at Nano scale and polishing precision needs to be controlled at angstrom level, this slurry selectivity does not necessarily translate to a good stop-on capability. At this precision level, stop-on performance is sensitive to the selection of CMP pad as well as how the CMP process is developed. It is also highly sensitive to the integration process, including the deposition process and various integration steps leading to CMP. This presentation reviews the critical roles CMP plays in fin formation, replacement metal gate (RMG) and local interconnects. Taking middle of line (MOL) CMP steps as examples, detailed discussion will be presented on how selectivity is modulated and how the needs of stop-on capability is balanced with the need to make sure complete clearing.