bluuebunny/crossref_metadata_2025 huggingface dataset:
(Invited) Thermochemistry of Redox Active Oxides and Its Relevance to Solar Fuel Generation
Authors: Haile Sossina M
Published: February 2020

Laboratories around the world are pursuing a variety of promising strategies for converting solar energy into a reliable energy source for on-demand utilization. We describe here a thermochemical approach for achieving this goal using solar heat as the energy source and redox active non-stoichiometric oxides as the reaction medium. Specifically, upon exposure to high temperatures and/or inert gas, the oxide undergoes reduction (without change in crystalline phase) to release oxygen. On cooling in the presence of H2O (or CO2), the oxide is reoxidized, releasing H2 (or CO). We compare the behavior of a variety of oxides, including those of the fluorite structure-type (ceria and its derivatives) and those of the perovskite structure-type (La1-xSrxMnO3). A shared characteristic of the most promising materials is that bulk oxygen diffusion (chemical diffusion) is fast such that fuel production rates are limited either by surface reaction kinetics or gas-phase mass transfer rates.
SAM Assisted Nickel-Boron Electroless Metallization of PDMS
Authors: Molazemhosseini Alireza , Ieffa Simona , Vena Pasquale , Magagnin Luca
Published: February 2020

Today, rapidly growing range of applications has a critical need for electronic systems, which cannot be made through rigid wafer-based technology. These applications include health-monitoring devices like electrochemical and strain biosensors. The key properties for these devices are bendability and stretchability [1-3]. As intrinsically flexible/stretchable materials have poor electrical performance, the dominant fabrication strategy is to exploit the flexibility of a polymer along with the electrical conductivity of a metal film. In this study, all-wet metallization of polydimethylsiloxane (PDMS) was carried out through Nickel-Boron (NiB) electroless deposition process. Self-assembled monolayers (SAM) of n-(2-aminoethyl) 3-aminopropyl-trimethoxysilane (AEAPTMS) was used to improve the metal thin film adhesion. PDMS surface modification was achieved by sodium hydroxide (1M) immersion for 24h. The modified surface was then silanized by a 0.02% v/v toluene based solution and later activated by a solution of palladium chloride. Water contact angle (WCA) examinations of PDMS surface revealed a significant decrease from 107° for the native surface to less than 50° after surface modification. Surface roughness changes were examined by atomic force microscopy (AFM) before and after each step of surface modification, silanization and metallization. Glow discharge optical emission spectroscopy (GDOES) confirmed the presence of the deposited layers together with the activated interface. Scanning electron microscopy (SEM) observations of PDMS/NiB interface indicated no detachment of NiB film for the silanized samples and significant detachment for non-silanized ones. Results of micro-scratch tests showed a 36% increase in the interface critical normal load of failure for the silanized sample compared to non-silanized one.  Samples with three lines of NiB on PDMS (each line with 5mm width and 20mm length) were prepared to act as a flexible electrochemical sensor (Fig. 1). According to cyclic voltammetry results for a scan range of -1 to 1 mV, the presence of 500 and 1000 ppm ethanol in KOH solution (0.5M) were successfully detected.  

References

A. J. Bandodkar, V. W. S. Hung, W. Jia, G. Valdés-Ramírez, J. R. Windmiller, A. G. Martinez, J. Ramírez, G. Chan, K. Kerman and J. Wang. 2013, Analyst., 138, 123.

J. T. Muth, D. M. Vogt, R. L. Truby, Y. Mengüç, D. B. Kolesky, R. J. Wood and J. A. Lewis. 2014, Adv. Mater., 26, 6307–6312.

W. Jia, A. J. Bandodkar, G. Valdés-Ramírez, J. R. Windmiller, Z. Yang, J. Ramírez, G. Chan and J. Wang. 2013, Anal. Chem., 85 (14), 6553–6560.

Figure 1
Microvia and through-Hole Filling By Electroplating for Electronic Circuit Fabrication
Authors: Dow Wei-Ping
Published: February 2020

Electronic products, such as computers, smart phones, laptops and so on, need chips to perform their functions. These chips have many devices, which need to be integrated and connected with each other. To expand the functions of electronic products, more MOS have not met the requirement yet compared with more chips. Therefore, the concept of three-dimensional (3D) chip stacking packaging is proposed. To meet high density interconnection (HDI), through silicon vias (TSVs), through glass vias (TGVs) used as conducting channels of chip stacking need to be fully filled with metal (e.g., copper or nickel-tungsten alloy), and microvia and through hole designed in IC packaging substrates and printed circuit boards (PCBs) need to be fully filled with copper as well. These filling plating technologies have similar process steps but their feature size is totally different.1-11 Herein, we will review these process steps and propose novel filling plating process steps and technologies, including highly selective microvia filling without copper deposition on the outside plane surface, direct through hole filling without usage of a conducting template, TSV filling using CoWP as a barrier layer and electroless copper as a seed layer, TSV filling using reduced graphene oxide (rGO) as barrier and seed layers, TSV filling without copper but rGO combining with NiW alloy, TGV filling using electroless copper as a seed layer and direct pattern copper electroplating onto a glass wafer by using Al-doped ZnO (AZO) as an adhesive and conducting layer.

References: 

1.       W.-P. Dow and H.-H. Chen, Circuit World 30 (3), 33-36 (2004).

2.      W.-P. Dow, H.-S. Huang, M.-Y. Yen and H.-C. Huang, Journal of The Electrochemical Society 152 (6), C425-C434 (2005).

3.       W.-P. Dow, M.-Y. Yen, W.-B. Lin and S.-W. Ho, Journal of The Electrochemical Society 152 (11), C769-C775 (2005).

4.       W.-P. Dow, H.-H. Chen, M.-Y. Yen, W.-H. Chen, K.-H. Hsu, P.-Y. Chuang, H. Ishizuka, N. Sakagawa and R. Kimizuka, Journal of The Electrochemical Society 155 (12), D750-D757 (2008).

5.       W.-P. Dow, M.-Y. Yen, S.-Z. Liao, Y.-D. Chiu and H.-C. Huang, Electrochimica Acta 53 (28), 8228-8237 (2008).

6.       W.-P. Dow, Y.-D. Chiu and M.-Y. Yen, Journal of The Electrochemical Society 156 (4), D155-D167 (2009).

7.       W.-P. Dow, C.-C. Li, Y.-C. Su, S.-P. Shen, C.-C. Huang, C. Lee, B. Hsu and S. Hsu, Electrochimica Acta 54 (24), 5894-5901 (2009).

8.       W.-P. Dow, C.-W. Lu, J.-Y. Lin and F.-C. Hsu, Electrochemical and Solid-State Letters 14 (6), D63-D67 (2011).

9.       Y.-T. Lin, M.-L. Wang, C.-F. Hsu, W.-P. Dow, S.-M. Lin and J.-J. Yang, Journal of The Electrochemical Society 160 (12), D3149-D3153 (2013).

10.     S.-P. Shen, W.-H. Chen, W.-P. Dow, T. Kamitamari, E. Cheng, J.-Y. Lin and W.-C. Chang, Microelectronic Engineering 105, 25-30 (2013).

11.     J.-J. Yan, L.-C. Chang, C.-W. Lu and W.-P. Dow, Electrochimica Acta 109 (0), 1-12 (2013).
Smart Polymers for Future Damascene Applications: Combining Bottom-up and Levelling Capabilities
Authors: Nguyen Hai , Stricker Florian , Lechner David , Furrer Julien , Grimaudo Valentine , Moreno-García Pavel , Riedo Andreas , Neuland Maike , Tulej Marek , Wurz Peter , Broekmann Peter
Published: February 2020

Classical additive concepts for the metallization of trenches and vias (Damascene applications) make use of a combination of polymeric suppressors (polyaklylene glycols, PAGs) and their specific antagonists (SPS). Their interplay is intended to regulate the desired bottom-up fill process. Typically, a leveler additive is added to the plating bath as a third additive component which is meant to avoid undesired overplating after the successful superfill.

In this contribution we discuss so-called hybrid polymers which comprise electrochemical characteristics of the PAG suppressors and classical leveler additives. Feature fill experiments demonstrate that bottom-up fill and leveling can indeed be achieved by using one single hybrid polymer component when combined with the SPS. Prototypical model additives showing these hybrid characteristics are polymerizates of epichlorohydrin and imidazole (Imep). Antagonistic Imep/SPS interactions required for the bottom-up fill are observed in particular at low (nominal) current densities whereas synergistic Imep/SPS interactions needed for leveling are dominant higher (nominal) current densities.

Copper films electrodeposited in the presence of an intact Imep leveler ensemble are essentially contamination-free. To probe the contamination level depth profiling experiments with sub-nm depth resolution were carried using a new femto-second laser ablation set-up coupled with a reflectron TOF mass spectrometer. This approach allows a true quantification of the contaminants which actually accumulate at the grain boundaries of the electrodeposited copper films.
Utilizing Inhibitor Molecules in Low Temperature CVD to Control Thin Film Conformality, Nucleation, and Surface Morphology
Authors: Abelson John Robert
Published: February 2020

When performed at substrate temperatures < 300°C, the growth of thin films by chemical vapor deposition can be strongly inhibited by the reversible adsorption of precursor, byproduct, or neutral molecule species on the active surface.  The system-dependent microscopic mechanisms include site blocking, associative desorption of precursor, or competitive adsorption.  Under extreme site blocking conditions, the reaction probability of arriving precursor molecules drops as low as 10-6 per wall collision, a value that affords extremely conformal growth in deep features with aspect ratio > 100:1.  The surface roughness is exceptionally low due to the smoothing effect of precursor re-emission, which mitigates the ‘shadowing’ effect of peaks in the local surface morphology. For precursor molecules that lack the vapor pressure or adsorption enthalpy to reach such values, we add a neutral molecule ‘inhibitor’ to enhance site blocking.  This approach converts a ‘non-conformal’ precursor into one that provides good step coverage in features with aspect ratio ~ 10:1. 

            We derive, based on the diffusion-reaction equation, a conformal zone diagram that predicts regimes of highly conformal CVD as a function of precursor pressure, substrate temperature and feature aspect ratio.

            We show that an inhibitor molecule can be used to control the film nucleation kinetics.  There are two regimes depending on whether the inhibitor molecule binds more strongly to the film material than to the bare substrate surface, or vice versa, such that the equilibrium coverage of inhibitor is large only on the more strongly binding surface.  For strong binding to the film, the density of small nuclei is enhanced, which affords an ultra-smooth film; we give the example of HfB2 growth on SiO2 using NH3 as the inhibitor.  Conversely, when the inhibitor slows the nucleation rate, the deposit consists the sparse distribution of islands in a narrow size distribution that may be useful in photonic or catalytic applications; we give the example of Cu growth using VTMS as the inhibitor.  Variants of the latter also afford highly selective growth, e.g., Cu deposition on a pre-existing metal line with essentially zero Cu nucleation on neighboring oxide. 

            Finally, we describe two methods to afford superconformal growth, meaning that the film growth rate increases with depth in a feature of aspect ratio between 10:1 and 25:1.  These utilize either a high sticking probability, consumable inhibitor, such as atomic H or N produced by a remote plasma source, or an intrinsic rate competition between two reactants.  Superconformal growth leads to excellent filling of deep features with no void space or seam along the centerline.
Using Azo As a Conductive and Adhesive Liner for through Glass Vias Filling By Cu Electroplating
Authors: Li Un-An , Cheng Chia-Wen , Chan Po-Fan , Dow Wei-Ping
Published: February 2020

This study introduces a method using aluminum-doped zinc oxide (AZO) as a conductive and adhesive liner for through glass vias (TGVs) filling by Cu electroplating. AZO liner is formed on a glass surface by three steps: AZO sol-gel coating, sol-gel evaporation and annealing. AZO sol-gel evaporation was observed by thermogravimetry-differential thermal analysis (TG-DTA). Surface morphology was observed by OM and SEM, and crystallinity and grain size were measured by XRD. AZO sol-gel evaporation rate is key for forming a conformal AZO liner in TGVs. When AZO sol-gel coating was operated under the condition at lower evaporation rate, it would form thick and non-uniform liner and there was a risk of void formation after copper electrodeposition. On the contrary, when the AZO sol-gel coating was operated under the condition of ultrahigh evaporation rate, a thin and uniform AZO liner was formed on the sidewall of the TGVs. This phenomenon refers to the fast coffee ring effect in TGVs. Cu Electroplating was used after AZO liner was formed in the TGVs. This study combined an alkaline conformal copper plating bath with an acid button-up copper plating bath to fill the TGVs. AZO liner cannot only enhance the adhesive force between the deposited copper and the glass, but also play an important role for direct copper plating in TGVs.
Plasma Electrochemistry: How to Control the Size and Size Distribution of Au Nanoparticles
Authors: Lee Seung Whan
Published: February 2020

Metal nanoparticles (NPs) have attracted a great deal of interest for their unique optical and catalytic properties. These novel materials are normally prepared in solution as colloids by chemically reducing metal salts in the presence of a stabilizer (i.e. surfactant). Recently, we have developed a green chemical approach based on plasma electrochemical reduction (PER). A novel microplasma source that plasmas formed at sub-millimeter spatial scale allows a non-thermal, atmospheric-pressure plasma to be stably formed at the surface of aqueous ionic electrolytes and thin polymeric films. This has enabled 1) charge transfer reactions at the plasma-liquid and plasma film interface [1] and 2) electrochemical applications of plasmas for novel materials synthesis [2-6]. However, although controlling the size and size distribution of nanoparticles is a primary requirement for their application potential in diversified area, still remained question is how to control the size and size distribution in plasma electrochemical approach.

Here, we present plasma electrochemical approach to control the size and size distribution of Au nanoparticles.  We initially prepared an aqueous solution including HAuCl4 and carried out PER (single-step process).  In order to grow Au nanoparticles, we synthesized Au seed by PER. Afterwards, Au precursor was slowly added to grow Au seed (multi-step process). As the results, multi-step process successfully synthesized the size of Au nanoparticles at the range from ~60 nm to ~1 um

To characterize the nanoparticle films, we have employed Ultraviolet-Visible absorbance spectroscopy, Nanoparticle size and Stability Analyzer, scanning electron microscopy (SEM) and transmission electron microscopy (TEM).

Acknowledgment

This work was supported by R&D Program of ‘Plasma Convergence & Fundamental Research’ through the National Fusion Research Institute of Korea (NFRI) funded by the Government funds.

References

[1] C. Richmonds, M. Witzke, B. Bartling, S. W. Lee, J. Wainright, C.-C. Liu, R. Mohan Sankaran, J. Am. Chem. Soc. 133, 17582 (2011).

[2] C. Richmonds and R. M. Sankaran , Appl. Phys. Lett. 93, 131501 (2008).

[3] S. W. Lee, D. Liang , X. P. A. Gao , and R. M. Sankaran  Adv. Func. Mater. 21, 2155  (2011).

[4] S. W. Lee, H. Zamani, P. X. L. Feng, and R. M. Sankaran,J. Vac. Sci. Technol. A, 30, 010603, (2011).

[5] S. W. Lee, J. R. Kumpfer, P. A. Lin, G. Li, X. P. A. Gao, S. J. Rowan, R. M. Sankaran, Macromolecules  45, 8201 (2012)

[6] S. W. Lee, M. Janyasupab, C.-C. Liu, R. M. Sankaran, Catal.Today, 211 137 (2013)

Figure: Photo and particle size analysis of Au nanoparticles after single-step and multi-step plasma electrochemical reduction .

Figure 1
Co-Generation of Fuels and Chemical in Mining Processes
Authors: West Alan , Banta Scott
Published: February 2020

We have developed an electrofuels method coupling an electrochemical reactor and a biological reactor containing chemolithoautrophic bacteria that have been engineered to produce chemicals or fuels [1,2].  Together, the two coupled reactors can use electricity generated from renewable sources to produce a chemical such as isobutyric acid or a fuel such as heptadecane from water and dilute CO2 from air.    The process contains no other stoichiometric inputs, is scalable, and currently is undergoing improvements to the engineering of the bugs.  While such a process is feasible, the cost of the electrical energy and the equipment motivates the exploration of alternative approaches

An alternative is discussed here, where we explore the feasibility of using chemical energy released during bioleaching processes to co-produce chemicals.  Here the ore or mineral waste is the sole source of the energy required to convert CO2 and water into the chemical.  The same chemolithoautrophic bacteria is exploited, since it is already used in the processing of between 10 and 25 % of the world’s copper from ore.  This organism grows under acidic conditions (pH of 2) using iron and/or sulfur as it energy source.  Its sole source of carbon is CO2.  In theory, the organism can thus be used for co-generation of chemicals in a large variety of mining processes.

We explain the concept, present results for product formation obtained with simulated and real copper ores.  Furthermore, the economic feasibility is discussed in terms of techno-economic analysis.  Long term and short term possibilities for the technology are presented.

[1].  Xiaozheng Li, Roel Mercado, Sarah Berlinger, Scott Banta, and Alan C. West, ” Engineering Acidothiobacillus ferrooxidans Growth Media for Enhanced Electrochemical Processing,” AICHE Journal, accepted (September, 2014).

[2] Xiaozheng Li, Roel Mercado, Timothy Kernan, Alan C. West and Scott Banta, ”Addition of Citrate to Acidothiobacillus ferrooxidans Cultures Enables Precipitate-Free Growth at Elevated pH and Reduces Ferric Inhibition,” Biotechnology and Bioengineering, 111, 1940 (2014).
Investigation of Dy Permeation through Dy Alloy Diaphragm Using Molten Salt Electrolysis
Authors: Konishi Hirokazu , Oishi Tetsuo , Nohira Toshiyuki , Ono Hideki , Takeuchi Eiichi
Published: February 2020

We have been developing a new process for the separation and recovery of rare earth metals using molten salt electrolysis and an alloy diaphragm. The diaphragm functions as a bipolar electrode and enables selective permeation of rare earth ions via the following steps: (1) Rare earth ions are produced by anodic dissolution of wastes containing rare earth metals in the anode room. (2) The rare earth ions are electrochemically reduced at the surface of the alloy diaphragm to form rare earth alloy. (3) The rare earth metals in the alloy diffuse to the other side surface of the alloy diaphragm and are dissolved into the cathode room as rare earth ions by anodic oxidation. (4) The rare earth ions in the cathode room are recovered as rare earth metals or alloys on a transition metal electrode. In this study, the permeation experiment was conducted with a new electrolytic cell. The current density due to alloy formation and anodic oxidation of Dy were measured individually using two potentio/galvanostats, and the results were discussed. DyCl3 was added to LiCl-KCl eutectic melts and Dy was permeated through a DyNi2 diaphragm film by potentiostatic electrolysis. The permeation rate (i.e. current density) was 280 A/m-2and the current efficiency was 98 % (max).
Achieving Surface Finish Requirements on DMLS Parts with Precision Electrochemical Machining
Authors: Risko Donald G
Published: February 2020

3D Additive Manufacturing is a fast growing technology with metallurgical properties of the “printed” parts achieving manufacturing requirements.  Direct Metal Laser Sintering (DMLS) is one of the few additive manufacturing technologies being used in production.  This technology is used to manufacture direct parts for a variety of industries including aerospace, dental, medical and other industries that have small to medium size, highly complex geometries.  Part tolerance and surface finish are two of the main requirements in addition to metallurgy that must be met by the DMLS parts.  Precision Electrochemical Machining (PECM) is a process capable of achieving these requirements on some applications at a significant cost advantage to other methods.  One example will be described in detail in this paper of an aerospace application requiring a surface finish of 4 Ra micro inch on a complex surface.
(Invited) Development of High Mobility Polymer Semiconductors for p-Channel, n-Channel, and Ambipolar Thin Film Transistors
Authors: Li Yuning
Published: February 2020

Polymer semiconductors are enabling materials for a wide range of printed electronics. As channel semiconductors for organic thin film transistors (OTFTs), charge carrier mobility on par with that of amorphous silicon (~0.5 cm2V-1s-1) or higher is required for many applications. The development of polymer semiconductors with high mobility and good ambient stability has been a great challenge. To improve the charge carrier transport, a combination of donor and acceptor units in an alternating fashion in the polymer backbone has been recently found very effective since the intermolecular donor-acceptor attraction can shorten the interchain distance. By utilizing this strategy, we have developed a number of donor-acceptor polymers semiconductors with very high mobility. One particular class of such polymers are based on a diketopyrrolopyrrole (DPP) acceptor building block. By carefully choosing the electron donor blocks, we have successfully developed p-type polymers with high mobility up to 6.9 cm2V-1s-1 and amibipolar polymers with balanced electron and hole mobility of 6.30 cm2V-1s-1 and 2.78 cm2V-1s-1, respectively. By using a ultra-thin layer (~2-5 nm) of polyethylenimine (PEI) to lower the work function of the source and drain contacts, we were able to block the hole injection and successfully transform ambipolar and even p-type transistors unipolar n-type transistors. This general approach to converting the transistor polarity broadens the scope of available polymer semiconductors for constructing n-channel transistors.

References

Li, Y.; Singh, S. P.; Sonar, P. Adv. Mater. 2010, 22, 4862-4866.

Li, Y.; Sonar, P.; Singh, S. P.; Soh, M. S.; van Meurs, M.; Tan, J.  J. Am. Chem. Soc. 2011, 133, 2198-2204.

Li, Y.; Sonar, P.; Murphy, L.; Hong, W. Energy Environ. Sci.
2013, 6,1684-1710.

Sun, B.; Hong, W.; Aziz, H.; Abukhdeir, N. M.; Li, Y. J. Mater. Chem. C
2013, 1, 4423-4426.

Chen, S.; Sun, B.; Hong, W.; Aziz, H.; Meng, Y.; Li, Y.
J. Mat. Chem. C.
2014, 2, 2183-2190.

Sun, B.; Hong, W.; Yan, Z.; Aziz, H.; Li, Y. Adv. Mater. 2014, 26, 2636–2642.

Sun, B.; Hong, W.; Thibau, E.; Aziz, H.; Lu, Z.H.; Li, Y. Organic Electronics
2014, 15, pp. 3787-3794.
(Invited) Thin-Film Transistors Based on Donor-Acceptor Polymers
Authors: Dodabalapur Ananth , Kim Seohee , Ha Taejun , Sonar Prashant
Published: February 2020

In this presentation we will describe device designs, modeling, and experimental results with several new diketopyrrolopyrrole DPP-based polymers and specifically discuss techniques to keep the operating voltage low (< 10 V) in small channel length (< 5 mm) devices.  We have been able to obtain mobility values of ~4 cm2/V-s with some of the materials in such devices at low operating voltages for channel lengths of 4 mm in air.  These devices possess very high temperature field-induced conductivity of any polymer FET and which exceeds that of most organic single crystal FETs reported so far.  Our best devices designs possess a bilayer gate insulator which includes a thin interfacial low- dielectric constant insulator.  We will demonstrate that the mobility improvement arises due to the suppression of the formation of Fröhlich polarons, which tend to reduce mobility when polar media such as high-k dielectrics are used with polymer semiconductors.  We will also discuss charge transport in such polymers transistors both above and below the threshold voltage.
Solution-Processed Light-Emitting Dielectric Films and Their Applications in Multifunctional Devices
Authors: Li Jing , Dong Guifang , Duan Lian , Wang Liduo
Published: February 2020

Ionic materials are used as gate dielectric layers for field-effect transistors (FETs) to reduce working voltage. In this paper, we exhibit a newly synthesized ionic iridium complex with interesting multifunction of both insulativity and light emission.1 Based on this material, a multifunctional device which behaves as a normal transistor at low gate voltage and a controllable light emitting device when the voltage is higher has been successfully fabricated. The device achieves area emission and the brightness can be tuned by three electrodes (gate, source and drain electrodes). Other ionic iridium complexes are also investigated. Results demonstrate that when mixed with some polymer, such as polymethyl methacrylate (PMMA), these complexes can form high performance light-emitting dielectric films as well. Through analysis of energy levels, the working mechanism of the device is proposed. Our study verifies that ionic light-emitting complexes have potential to be used in low-voltage multifunctional electronic devices.

This work was financially supported by the National Natural Science Foundation of China (No. 61177023, 51173096, and 61474069).

Reference:

1 J. Li, G. Dong*, L. Duan, D. Ma, T. Hu, Y. Zhang, L. Wang and Y. Qiu, RSC Adv.
2014, 4, 51294.

Figure 1
(Invited) Disentangling the Effects of Gated-Contacts on Transconductance in Organic FETs
Authors: Bittle Emily , Basham James I. , Jackson Thomas N. , Jurchescu Oana D , Gundlach David J.
Published: February 2020

Recent reports of solution processed organic thin film transistors (TFTs) with exceedingly high field-effect mobility have spurred renewed interest in organic TFTs because of their potential to impact higher performance electronic applications than previously envisioned, while also stimulating considerable debate around the transport physics allowing such high charge carrier mobility in these intriguing material systems.  Most reports parameterizing TFT performance make use of DC electrical characterization methods and mathematical relationships that describe transistor current as a function of applied voltage for ideal devices.  However, the electrical characteristics reported for many of the highest mobility TFTs exhibit substantial non-ideal behavior.  Thus, a detailed investigation of organic transistors with such behavior is needed to discern the transistor channel properties from parasitic device effects that might affect the device operation and give rise to incorrect mobility estimates.  We report here on the use of impedance spectroscopy to disentangle the effects of contacts on device operation and extract the electrical properties of the channel.  Specifically, we look at the small signal AC impedance of rubrene single crystal transistors to investigate "ideal" low field electronic behavior.  The rubrene crystals are grown by vapor transport method and laminated onto prefabricated transistor test structures consisting of a heavily doped silicon substrate (gate electrode), thermally-grown silicon dioxide layer (gate dielectric), and photolithographically-defined metal electrodes (source and drain contacts).  The completed rubrene transistors have channel lengths ranging from 50 µm to 100 µm.  The impedance response is measured as a function of gate bias and frequency (varied from 20 Hz to 2 MHz).  By using a transmission line model to fit the transistor channel coupled with a parallel resistor-capacitor model of the contact impedance, we are able to observe the behavior of the transistor channel and contacts separately as a function of gate bias. We determine the low field mobility of the device independent of contact resistance and show that rapidly changing contact resistance governs the current flow at low gate voltage in DC current-voltage measurements.  This effect gives rise to large transconductance near threshold that reflects the “turn-on” of the gated-contacts rather than solely channel response making mobility extracted by using traditional DC current-voltage relationships describing only the channel inappropriate in this bias region.
(Invited) Electrochemical Reaction Induced Amorphization to Complex Oxide Surface and Its Impact to Catalyst Activity for Oxygen Evolution Reaction
Authors: Jia Hongfei , Zhou Li Qin , Ling Chen
Published: February 2020

Water splitting and artificial photosynthesis systems are proposed as promising approaches to the conversion and storage of solar energy into chemical fuels.  However, their efficiency is often limited by the sluggish kinetics of oxygen evolution reaction (OER). Although IrO2 and RuO2 can effectively reduce activation barriers for OER, the scarcity of the materials makes it difficult to use them as OER catalysts for large-scale implementation.  Recently there have been a growing interest to investigate complex oxides as alternative OER catalysts and several new catalysts showed activity better or comparable to IrO2 benchmark.  Along with these efforts, experimental evidences also indicated many of complex oxides were not stable under reaction conditions, of which amorphization was often observed at catalyst/electrolyte interface after cyclic voltammetry (CV) or potentiostatic measurements [1-3].  Our recent results showed that such type of surface amorphization processes seemed to affect catalyst performance in quite different ways dependent on catalyst material, electrolyte pH and compositions.  For instances, in alkaline electrolyte (0.1 M NaOH), the activity of cobalt tungstate reduced after multiple CVs, while copper tungstate, on the other hand, became more active.  Under similar conditions, another lithium-containing OER catalyst, Li2CoGeO4, maintained majority of its original activity even after significant loss of lithium and germanium from its surface.  In this study, the surface amorphization process is examined by multiple characterization techniques including HR-TEM, XPS, electrochemical and compositional analyses.  Possible mechanisms leading to these distinctive behaviors will be discussed in detail.

(1)  S. W. Lee, et al., JACS, 2012, 134, 16959-16962

(2)  M. Risch, et al., JPCC, 2013, 117, 8628-8635

(3)  K. J. McDonald, et al., J. Mater. Chem. A, 2014, 2, 18428-18434
Porous Carbon Hollow Nanospheres for Confining Polysulfide in Lithium Sulfur Batteries
Authors: Zhou Weidong , Xiao Xingcheng , Cai Mei , Yang Li
Published: February 2020

Lithium–sulfur batteries (Li–S), as one of the most promising candidates, have attracted increasing attention owing to its high theoretical capacity (1675 mAh g-1), low safety concerns/environmental footprint, high natural abundance and competitive cost. Despite these considerable advantages, practical application of  Li–S batteries is still hindered currently by several challenges, including low electrical conductivity of sulfur/polysulfides, dissolution of lithium polysulfides and the resulting shuttling effect.

To better confine the sulfur/polysulfides in the electrode of Lithium–Sulfur (Li/S) batteries and improve the cycling stability, we developed a porous carbon shell to confine polysulfide. We systematic investigate the effect of pore size on the confining effect of porous C, and found out small pore size down to 2.8 nm gave the best confining effect.  We further developed a core–shell structure with polymer coated porous carbon as shell and S as core. It was first prepared through impregnation of sulfur into hollow carbon spheres under heat treatment, followed by a coating polymerization to give a double layers core–shell structure. From the study of scanning transmission electron microscopy (STEM) images, we demonstrated that the sulfur not only successfully penetrated through the porous carbon shell but also aggregated along the inner wall of the carbon shell, which, for the first time, provided visible and convincing evidence that sulfur preferred diffusing into the hollow carbon rather than aggregating in/on the porous wall of the carbon. Taking advantage of this structure, stable capacity of 900 mAh g-1 at 0.2 C after 150 cycles and 630 mAh g-1 at 0.6 C after 600 cycles could be obtained in Li/S batteries. We also demonstrated the feasibility of full cells using the sulfur electrodes to couple with the silicon film electrodes, which exhibited significantly improved cycling stability and efficiency. The remarkable electrochemical performance could be attributed to the desirable confinement of sulfur through the unique double layers core–shell architectures. [1]

W. Zhou, X. Xiao, M. Cai, Y. Li, Nano Letters, 2014, 14 (9), 5250–5256
Metal Organic Frameworks (MOFs) Cooperated Si Nanorod Arrays Used in Rechargeable Batteries
Authors: Li Jing , Yu Yingjian , Yue Chuang , Sun Shibo , He Xu
Published: February 2020

Given the large surface area and unique channels, metal-organic frameworks (MOFs),1 have  served as a “generalist” in the fields of clean energy,2 such as adsorbents for hydrogen,3 electrolytes for fuel cells,4 electrode materials for supercapacitors5 and so on. However, only a few immature applications of MOFs as electrodes for lithium ion batteries (LIBs) or micro-LIBs have been researched.6-9To the contrary, Si anode, with the highest theoretical capacity, low working potential and feasible integration with other micro- or nano-electronic devices, has been intensively investigated experimentally and theoretically to address the volume expansion issue during discharge/charge processes. But, fully addressing the deterioration of the electrode structures caused by the volume expansion, which would generally results in performance fading and safety issues, is still challenging.

In this work, a novel class of MOFs, was initially proposed to composite/network with Si nanorod (NR) arrays as anodes for LIBs employing the modified nanosphere lithography (NSL) and inductive coupled plasma (ICP) dry etching followed by a method of solution growth. An enhanced capacity was accomplished in this hybrid material nanocomposite electrode compare with that in the only Si NR anodes. In addition, with the employment of a buffer layer of Ti/TiN to modify the electronic conductivity of the interfaces between Si inner core and outer MOFs, a further enhanced capacity was realized accompanied with the high Coulombic Efficiency (CE).First principles calculations were performed to verify the favorable lithium diffusion in the MOF cooperated Si structure.

References:

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[2] Li, S.-L; Xu, Q. Energy. Environ. Sci.
2013, 6, 1656.

[3] Rosi, N. L.; Eckert, J.; Eddaoudi, M.; Vodak, D. T.; Kim, J.; O’Keeffe, M.; Yaghi, O.M. Science
2003, 300, 1127.

[4] Nagao, Y.; Fujishima, M.; Ikeda, R.; Kitagawa, H. Synth. Met.
2003, 123, 133.

[5] DÍaz, R.; Orcajo, M. G.; Botas, J. A.; Calleja, G.; Palma, J.  Mater. Lett.
2012, 68, 126.

[6] Barthelet, K.; Marrot, J.; Riou, D.; Férey, G. Angew. Chem., Int. Ed.
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[7]  Zheng, X.; Li, Y.; Xu, Y.; Hong, Z.; Wei, M. CrystEngComm
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[8] Wessells, C. D.; Huggins, R. A.; Cui, Y. Nat. Commun.
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[9] Han, Y.; Qi, P.; Li, S.; Feng, X.; Zhou, J.; Li, H.; Su, S.; Li, X.; Wang, B. Chem. Commun. 2014, 50, 8057.
Toward a Better Understanding of the Surface Effect through the Design of Conductive Binders in Lithium Sulfur Battery
Authors: Ai Guo , Wang Zhihui , Dai Yiling , Zhao Hui , Chen Yulin , Liu Gao
Published: February 2020

Li-S battery has attracted much attention, because of the extreme high theoretical capacity and low cost compare to Li-ion battery. But the poor cycling life of lithium sulfur battery kept them from large scale usage. The poor electric conductivity of the charge and discharge product is another limitation for Li-S battery. A lot of research work has focused on the improvement of electrode design, including the combination of porous carbon film, carbon paper, carbon nanotube, graphene or other conductive nanostructure. The design of binder is another effect way to improved the battery performance, because the binder covers up most of the inner surface of the electrode, which has a important effect in surface modification. In Li-S battery, a notable feature of phase transformation will take place, which are from solid phase S8/Li2S8 into soluble Li2S4, then precipitate into solid state Li2S during discharge and the combination of solid phase and liquid phase reaction during charge. The surface effect of binder will have a much bigger influence on Li-S battery performance because this phase transformation.

So in this work, we investigated several binders with different kind of functional group, including both conductive and nonconductive binders, to study the effect of binder on surface modification. A huge difference is observed in electrochemical performance and electrode morphology with different binders. These indicates the different effect of binder on surface modification and therefore in reaction mechanism during charge and discharge. So, we suggest that the designing of binder with preferred physical and electrochemical property in indeed crucial in further improving the performance of Li-S battery.
Carbon Hotels with Nanosulfur Guests: Promising High Capacity Cathode Architecture with Hybrid Electrolyte for Lithium-Sulfur Battery
Authors: Pol Vilas G. , Dysart Arthur , Hong Chulgi , Etacheri Vinodkumar , Tang Jialiang
Published: February 2020

Lithium-sulfur battery is highly appealing primarily due to its high theoretical specific energy of 2567 Whkg-1 and specific capacity of 1672 mAhg-1, both values an order of magnitude higher than those of commercialized Li-ion systems.1-
2 Despite the wealth of literature demonstrating remarkable carbon-sulfur cathode architectures for Li-S systems, their industrial adoption is limited by performance issues such as low columbic efficiency, poor cycle life, and impractical syntheses. It is imperative that continuing studies on Li-S systems recognize the importance of the underlying fundamental chemistry for progress to be seen. The focus of this work is to develop, characterize, and optimize both Li-S materials and synthesis processes in the pursuit of a practical Li-S rechargeable battery.

Through this work, we understand the shuttle mechanisms and its effect on stable cycling performance and high columbic efficiency in Li-S systems. Initially, we have fabricated carbon hotels using starch based precursor with solid state synthesis approach. These premade hollow carbon particles are filled in situ with sulfur nanoparticles, sonochemically.  The electrolyte used is DOL:D2:LiTFSI. The newly developed C-S  composite cathode demonstrates high columbic efficiency (minimum 97%) and ~900 mAh/g reversible capacity during long cycling.

References

Bruce, P. G.; Freunberger, S. A.; Hardwick, L. J.; Tarascon, J.-M. Nature Materials
2012, 11.

W. Weng, V. G. Pol, K. Amine, Adv. Mater., 2013, 25, 1608–1615
Li Storage Feasibility of Defected Single- and Bi-Layer Graphene
Authors: Yildirim Handan , Kinaci Alper , Zhao Zhi-Jian , Chan Maria K. Y. , Greeley Jeff
Published: February 2020

The limited capacity of the intercalation-type graphitic materials has lead to much effort to explore new electrode materials. A natural choice among the carbonaceous materials, graphene, has attracted increased attention for obtaining higher Li storage capacity. The outstanding mechanical strength, electronic conductivity, and ready availability of extra storage sites for Li, has suggested that this material could be an ideal platform for storing more Li. However, for wide range of Li coverages, the calculations predict that defect-free single layer graphene is not thermodynamically favorable for lithiation compared to bulk metallic Li. Thus, exploring ways with which graphene surfaces can be activated such that Li storage capacity can be improved has become a significant focus of research in the field. One such strategy is to activate graphene surface with structural defects. Generally speaking, structural defects can be found nearly in all carbonaceous materials. The presence of such defects can be detrimental for the performance of graphene-based devices. In contrast, however, deviations from the perfection of atomic lattice can also be useful for some applications, as they make it possible to tailor the properties leading to new functionalities.

Following this approach, we performed an extensive series of density functional theory (DFT) calculations for Li adsorption and intercalation in single and bi-layer graphene, which are activated by topological defects for improving Li adsorption. The results confirm that Li adsorption on defect-free single layer graphene is not thermodynamically favorable compared to bulk metallic Li. However, graphene surfaces activated by structural defects are generally found to bind Li more strongly, with the interaction strength sensitive to both the nature of the defects and their densities. The interaction of Li with a one-dimensional extended defect is additionally found to be strong, improving Li storage capacity. The theoretical Li storage capacities of the defected single-layer graphene structures are evaluated with a rigorous thermodynamic analysis, which establishes, in some cases, that these capacities approach, although not exceed, those of graphite. Li storage in bi-layer graphene with and without defects are evaluated in a similar way, and indicate more favorable interaction, and promise for higher Li storage than that of single layer graphene. We will present performance comparisons between defected single- and bi-layer graphene structures, and bulk-graphite for Li storage capacities. A detailed analysis of the effect of the van der Walls (vdW) interactions will also be presented.
Novel Approaches for Engineering Li2S Cathodes of Lithium Sulfur Batteries
Authors: Chen Lin , Shaw Leon
Published: February 2020

Lithium–sulfur (Li–S) batteries are attractive as the next generation of energy storage devices for the applications in portable electronics and electric vehicles due to their high energy density. In the recent years, various novel electrodes and electrolytes have been tried to enhance the battery performance. However, these designs have not completely addressed the issue of low capacity retention. Herein, we proposed a novel template approach to engineer C@Li2S@C with double-core shell structure. Via this method, the outside carbon shell offers a pathway to electrons and enables a high electronic conductivity. The Li2S layer with sphere structures is expected to be well encapsulated by the carbon shell. In the early stage testing, the cells yield an initial capacity of around 910 mA h/g. More importantly, there are only small decays after the 2nd cycle and little degradations from the 16th cycle to the 53rd cycle with a high retained capacity of ~570 mA h/g, which means the capacity retention is excellent with an ultrahigh Comloubic efficiency of 96%.
The Unexpected Discovery of New Mg Complexes As Electrolytes for Rechargeable Magnesium Batteries
Authors: Liao Chen , Pan Baofei , Burrell Anthony K. , Zhang Zhengcheng
Published: February 2020

The electrolytes play a pivotal role in the multivalent batteries. Here we will report the unexpected discovery of new complexes as electrolytes for magnesium batteries. Eliminating the usage of Lewis acids, the electrolytes are safer than conventional magnesium organohaloaluminate. The electrolytes have a high coulombic efficiency for Mg plating/dissolution and the anodic stability is increased to 3.3 V vs Mg. The preparation and characterization of the new electrolytes will be presented, including the syntheses, multinuclear NMR spectroscopy, the hypothesis of the product formation, the electrochemical characterization such as ionic conductivities and transport numbers. The capabilities of the electrolyte with Chevrel Phase Mo6S8 and other cathodes will also be discussed.

Figure 1
Computational Examination of Orientation-Dependent Morphological Evolution during the Electrodeposition and Electrodissolution of Magnesium
Authors: DeWitt Stephen , Thornton Katsuyo
Published: February 2020

Magnesium batteries provide a promising alternative to Li-ion batteries due to their potential for lower cost, higher energy density, and safer, dendrite-free operation. Magnesium is the eighth most abundant element in the earth’s crust, and replacing the relatively rarer lithium could enable reduced battery costs. Furthermore, metallic Mg anodes have a significantly higher theoretical specific volumetric capacity (3833 mAh/cm3) than either Li-graphite anodes (760 mAh/cm3) or metallic Li anodes (2046 mAh/cm3). Finally, metallic Li anodes often form dendrites during cycling that can short the battery, leading to thermal runaway. In contrast, metallic Mg anodes form compact faceted films during cycling with minimal risk of dendrite formation.

Understanding the evolution of the metallic Mg anode is a critical factor in the development of a practical, high-performance Mg-metal battery. In this presentation, we describe a new model for simulating the evolution of the faceted Mg deposits, both during deposition and during dissolution. We apply the standard dilute solution equations to describe the evolution of the concentration and the distribution of the potential in the electrolyte. The evolution of the magnesium deposit is described using a phase-field approach with conserved dynamics and a source term along the deposit surface to account for deposition and dissolution. The deposition/dissolution rate is calculated using Butler-Volmer kinetics. Reaction rate constants that depend on the local orientation of the surface of the deposit allow for the simulation of facet development and evolution. We present two possible models relating the orientation dependence of the forward rate constant to that of the backward rate constant.

We apply this model to a range of experimentally relevant scenarios to improve the understanding of the mechanisms governing the film morphology during cycling. We investigate the effect on the deposit morphology of changing the applied current density during growth, finding that the deposits become narrower and taller as the applied current increases. We present predictions of the characteristic deposit morphology during dissolution for the two orientation-dependent reaction rate models. These predictions provide a diagnostic criterion for future experiments to determine which of the two models is correct. Finally, we present a series of two-deposit simulations to illustrate the types of interactions between deposits and how those interactions influence the film morphology.

Acknowledgement:

This work was supported as part of the Joint Center for Energy Storage Research, an Energy Innovation Hub funded by the U.S. Department of Energy, Office of Science, Basic Energy Sciences. This research used resources of the National Energy Research Scientific Computing Center, a DOE Office of Science User Facility supported by the Office of Science of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231.
Electrolyte Development for Magnesium Ion Battery
Authors: Sa Niya , Proffit Danielle L. , Vaughey John T. , Lipson Albert L. , Liao Chen , Ingram Brian , Ren Yang , Burrell Anthony K.
Published: February 2020

Abundance of the magnesium element in the earth's crust as well as the safety features of Mg metal have attracted considerable attention for rechargeable Mg battery development. Before the successful invention of a prototype Mg ion battery, optimization of the Mg electrolyte performance is necessary. Exploration of the compatibility of an Mg electrolyte with high voltage cathode materials against Mg metal anode remains to be a big challenge. In this work, we will present some current studies of the electrolyte development for Mg ion battery. Specifically, electrochemical evaluation of the performance of the magnesium bis(trifluoromethane sulfonyl)imide-based non-aqueous electrolyte on the cathode and anode materials will be discussed.