bluuebunny/crossref_metadata_2025_split huggingface dataset:
Accessing New Monomers from Biopriviledged Molecules By Coupling Metabolic Engineering and Electrosynthesis
Authors: Matthiesen John Edward , Abdolmohammadi Sanaz , Cochran Eric W. , Tessonnier Jean-Philippe 
Published: February 2020

Recent progress in metabolic engineering has generated new microorganisms able to convert carbohydrates and waste lignin into biopriviledged molecules.1 One of these molecules, muconic acid, can be further diversified to adipic acid and terephthalic acid, which are central to the production of Nylon-6,6 and polyethylene terephthalate (PET). Its semi-hydrogenation also leads to new molecules such as trans-3-hexenedioic acid (3HDA), a compound that enables the synthesis of bio-advantaged Nylon-6,6. However, to achieve economically sustainable conversion, it is crucial to streamline the fermentation and downstream catalytic processing steps. This generates new challenges as biogenic impurities inherent to the fermentation broth can deactivate Pt-group metal catalysts.
An alternative approach would be to utilize novel conversion schemes using robust base metals that are stable in the presence of biogenic impurities.2 We show that electrosynthesis represents a promising approach for the direct processing of unpurified broths.2,3 The water, salts, and acidic impurities already present in the medium provide a suitable electrolyte, while protons in the solution provide the hydrogen required for the desired transformation. Muconic acid was converted to 3HDA with a 94% yield and 100% faradaic efficiency using lead (Pb) electrodes.4 Under these conditions, 3HDA can be produced at a competitive price of $2.00 kg-1. The reaction mechanism and the origin of the high selectivity to 3HDA will be discussed.
1. B.H. Shanks and P. Keeling, Bioprivileged Molecules: Creating Value from Biomass, Green Chem. 2017, advance article. https://dx.doi.org/10.1039/C7GC00296C
2. M. Suastegui, J. E. Matthiesen, J. M. Carraher, N. Hernandez, N. Rodriguez Quiroz, A. Okerlund, E. W. Cochran, Z. Shao, J.-P. Tessonnier, Combining Metabolic Engineering and Electrocatalysis: Application to the Production of Polyamides from Sugar, Angew. Chem. Int. Ed.,
2016, 55, 2368-2373. http://dx.doi.org/10.1002/anie.201509653
3. J. E. Matthiesen, J. M. Carraher, M. Vasiliu, D. A. Dixon, J.-P. Tessonnier, Electrochemical Conversion of Muconic Acid to Biobased Diacid Monomers, ACS Sustainable Chem. Eng.,
2016, 4, 3575-3585. http://dx.doi.org/10.1021/acssuschemeng.6b00679
4. J. E. Matthiesen, M. Suástegui, Y. Wu, M. Viswanathan, Y. Qu, M. Cao, N. Rodriguez-Quiroz, A. Okerlund, G. Kraus, D. R. Raman, Z. Shao, J.-P. Tessonnier, Electrochemical Conversion of Biologically Produced Muconic Acid: Key Considerations for Scale-up and Corresponding Technoeconomic Analysis, ACS Sustainable Chem. Eng.,
2016, 12, 7098-7109. http://dx.doi.org/10.1021/acssuschemeng.6b01981
Selective Hydrogenations in Proton Exchange Membrane Reactor
Authors: Carl Sarah , Waldrop Krysta , Pintauro Peter N , Thompson Levi T 
Published: February 2020

With the increased demand for environmentally sustainable fuels and chemicals, interest in the conversion of biomass conversion into value-added chemicals and high density fuels has increased. Traditional biomass upgrading processes are carried out thermocatalytically at high temperatures and pressures, and often yield low selectivities. In contrast, electrocatalytic process can be performed at low temperatures and pressures and can utilize renewable electricity. In addition for hydrogenation reactions, high hydrogen concentrations can be achieved.
The key to controlling the selectivity of electrocatalytic hydrogenations is identifying appropriate cathode materials. Our group has been exploring the use of early trasition metal carbide based materials for a variety of electrocatalytic and catalytic reactions. Significant improvements in product yields and selectivities have been demonstrated for the electrocatalytic hydrogenation of triglycerides using W2C and Pd/W2C materials. These improved rates have been linked to hydrogen spillover and synergistic effects between Pd and the W2C support.
The aim of research described in this paper was to investigate the use of a proton exchange membrane reactor for the electrocatalytic hydrogenation of model biomass species including furfural and crotonaldehyde, and compare the results with those from conventional thermocatalytic processes. Expanding upon previous work, the cathode catalyst consisted of a metal active for hydrogenation (Pd, Co, and Ni) supported on traditional thermocatalyst supports (SiO2 and Al2O3), a traditional electrocatalyst supports (carbon), and Mo2C, a conductive thermocatalyst that has been extensively studied for various hydrogenation reactions. Structural and compositional properties of the materials were linked to their hydrogenation rates and selectivities.
Towards Sustainable Fuels from Biomass Using Fast Pyrolysis and Electrocatalysis in Regional Depots
Authors: Saffron Christopher M. , Das Sabyasachi , Fasahati Peyman , Garedew Mahlet , Lam Chun Ho , Jackson James E. 
Published: February 2020

Novel routes to renewable hydrocarbon fuels are needed to provide transportation energy for operating the U.S. automobile fleet and to reduce atmospheric carbon concentrations. Biomass-to-liquid technologies are necessary components of future bioenergy systems that are used instead of fossil systems to minimize climate change. Fast pyrolysis is a thermochemical technology that converts biomass into liquid fuel intermediates while producing biochar, a co-product that sequesters carbon when land applied. Though biochar is potentially of great benefit to the environment, the liquid intermediate made by pyrolysis, known as bio-oil, requires significant upgrading to meet the standards that are currently imposed on gasoline and diesel fuel. Following biomass deconstruction by fast pyrolysis at regional depots, electrocatalytic hydrogenation and deoxygenation (ECH) is proposed to partially upgrade bio-oil to create a stable intermediate with properties superior to raw bio-oil. Decentralized and distributed systems of this kind will allow for optimizing the balance of “economies of scale” and “economies of transportation,” while valorising agricultural commodities for rural prosperity. Subsequent hydroprocessing at centralized refineries, possibly using hydrogen from wind- or solar-driven electrolysis, creates the finished fuel. By reactively stabilizing bio-oil and increasing its energy content, ECH could be a foundational technology for this novel bioenergy system that is capable of significant decarbonization of the terrestrial atmosphere.
Synthesis of ALD Iridium Thin Films on Silicon and Monel K-500 Steel Substrates
Authors: Oelslager Peter John , Baumgart Helmut 
Published: February 2020

Iridium (Ir) thin films have been extensively investigated for a variety of applications. Ir is a potential optical material for Fresnel zone X-ray microchannel plates, and inductive grid filters. It is also a noble metal making it well suited to corrosion resistance in harsh environments
Atomic Layer Deposition (ALD) is considered a special case of chemical vapor deposition (CVD) in that two different chemical precursor materials are alternately introduced into a vacuum chamber where a chemical reaction occurs on the surface of the substrate. This method of thin film growth is self-limiting and conformal and consequently results in precise layer thickness control, stoichiometry, composition, and uniformity across a large surface area. Advantages that are unique to ALD include the ability to grow conformal thin films across complex geometries, and the relatively low temperatures required to achieve film growth.
In this work, iridium metal films were synthesized on silicon (Si) and Monel K-500 alloy substrates by ALD using Iridium (III) acetylacetonate known as Ir(acac)3 or [CH3COCH=C(O-)CH3]3 Ir as precursor 1, and industrial grade O2 as oxidizing reactant. The solid Ir precursor was heated to 150 °C, and the substrate temperature was varied to establish an optimum growth window. The lowest temperature in which Ir growth was found is 200 °C, and the thin film growth rate increased as a function of temperature up to 250 °C. Higher temperatures have not yet been attempted due to equipment constraints. The Monel K-500 steel alloy flat discs were cut from commercially available Monel K-500 bars of ~1 inch diameter.
In this study we report on the successful synthesis of Ir films on Si and Monel K-500 substrates. Detailed characterization has been performed using X-ray diffraction (XRD) techniques, atomic force microscopy (AFM), and field emission scanning electron microscopy (FE-SEM) of samples which have been notched with focused ion beam (FIB) techniques for cross-sectional film thickness measurements as revealed in Figure 1. The polycrystalline ALD Iridium film exhibited good chemisorption and adhesion to native oxide covered Si substrates, with hydroxyl surface termination. However even with the absence of a SiO2 surface film, the ALD synthesis of Iridium metal films worked equally well on the Monel K-500 steel alloy flat disc substrates and yielded excellent surface coverage.
Development of Advanced Cobalt CMP Slurry Platform By Electrochemical Screening and Polishing Studies
Authors: Theivanayagam Murali Ganth , Wang Hongyu , VanHanehem Matthew , Auger Robert 
Published: February 2020

In advanced nodes at 10 nm and below, cobalt (Co) metal is under investigation to replace copper (Cu) in metal lines and vias in back end of line (BEOL) for the first few metal layers due to its better electromigration performance, lower resistivity, conformal coverage in high aspect ratio features, and overall improved device performance. These new integration schemes require Co chemical mechanical planarization (CMP) steps to achieve planarity and desired target thickness. However, Co metal is prone to corrosion in aqueous solutions and its lower redox potential makes it an easy galvanic corrosion target under CMP conditions. Commercial Cu bulk slurries are not compatible for Co polishing as they show significant corrosion defects such as pitting, rough surface, and missing lines after CMP. Advanced Co bulk CMP slurries, therefore, need to contain effective chelator, corrosion inhibitor, and additives at suitable slurry pH to eliminate corrosion defects, while still delivering high Co removal rates (2000 to 5000 Å/min).
In this presentation, we will discuss the systematic approach taken to develop a Co bulk CMP slurry formulation platform that can provide high removal rates and low/no corrosion, through development of fundamental understanding of Co surface chemistry, chelation, and corrosion properties. Results and key learnings from the extensive screening techniques such as Tafel polarization, galvanic corrosion, static-etch corrosion, quartz crystal microbalance, and X-ray photo electron spectroscopy analyses used to identify the ideal slurry pH, effective chelators, and corrosion inhibitors will be shared. In addition, Co blanket and pattern wafer polishing performances will be presented for the leading slurry formulations.
(Invited) Transition Metal Dichalcogenide Semiconductor Growth and Large Area Devices for Optoelectronics and Sensing
Authors: Garg Sourav , Mollah Abu Shahab , Waters Joseph L , Kim Seongsin M , Kung Patrick 
Published: February 2020

Atomically-thin transition metal dichalcogenides (TMDCs), such as MoS2 and WS2, are topological materials with physical characteristics of great interest for the realization of nano-electronic and photonic devices, with promising applications for chemical and biological sensing. These semiconductors possess a bandgap that changes from indirect to direct as a result of the disappearance of inversion symmetry when the material is reduced into a sub-nanometer monolayer form (2D). Although TMDC monolayers were originally and are continuing to be widely realized through mechanical exfoliation, there are accelerating material synthesis efforts to achieve more controllably sized and shaped TMDC in order to facilitate the realization of devices with greater consistency.
In this work, we present the growth and characterization of continuous monolayer TMDC followed by the realization and measurement of both photoconductive and Schottky detectors, as well as chemical sensor devices. The materials were grown by chemical vapor deposition on sapphire substrates. The monolayers were subsequently characterized using Raman spectroscopy, photoluminescence, fluorescence imaging, optical absorption, atomic force microscopy, and electron microscopy. Large area metal-2D semiconductor-metal interdigitated devices were realized by conventional photolithography, with 20 μm wide and 4000 μm long metal fingers separated by a distance ranging from 5 to 50 μm.
The electrical and photoresponse characteristics of MoS2 based photoconductors were measured at room temperature in nitrogen ambient. The spectral response was measured in the 400-800 nm range and exhibited a rapid drop for wavelengths longer than 675 nm, corresponding to the bandgap of MoS2. The spectral response revealed clear A and B band-edge exciton related peaks, as well as a peak arising from the van Hove singularities. At a bias of 1 V, monolayer MoS2 devices exhibited a responsivity of 11 A/W corresponding to a specific detectivity of 8x1011 Jones. The high responsivity was associated with a large photoconductive gain arising from trap states/surface states in the large area MoS2 material and device. The resulting persistent photoconductivity and photoconductive time decay were subsequently studied. The use of MoS2 devices for chemical sensing was investigated. The changes in electrical resistance in the dark was monitored as a function of the concentration of the gas sensed in an inert nitrogen ambient. When tested for CO2, concentrations down to 200 ppm were able to be detected.
(Invited) 2D Materials Synthesis: It’s All about the Substrate
Authors: Robinson Joshua A 
Published: February 2020

To date, the majority of published works on electronic and optoelectronic properties of 2D materials has been from mechanically exfoliated flakes on silicon oxide. However, if we are to make 2D materials a viable material technology, we must be able to grow them over very large scale, with exceptional control over structure, chemistry, and doping. We have demonstrated that direct synthesis of a variety of 2D layers and heterostructures, and have found that the substrate upon which the materials are grown can ultimately dictate the properties and performance of the synthetic layers. In this talk, I will discuss recent breakthroughs in our understanding and engineering of the 2D/3D interface to achieve high quality 2D layers on sapphire and other crystalline substrates. This includes the impact of substrate chemistry, structure, and defects on achieving high moblity and high quantum-yield 2D layers.
Synthesis and Optoelectronic Performance of III-V Nanowires
Authors: Zhang Xuehong , Pan Anlian 
Published: February 2020

III-V semiconductor nanowires (NWs), such as InAs, GaAs, InP, are promising materials for applications in infrared optoelectronic devices because of their typically high carrier mobilities and narrow band gap. In view of expanding the application fields, a major opportunity for III-V NWs and their applications lies in the tunability of bandgaps. Here, the complete composition range InAsxP1-x alloy NWs with potential bandgap tunability from the near-IR region to the mid-IR region were synthesized by a new route combining the vapor-liquid-solid (VLS) growth mechanism with an additional ion-exchange (IE) process. Based on these as-grown InAsxP1-x NWs, broadly band tunable nanometer-scale infrared photodetectors (PDs) have been achieved. In addition, high quality GaSb/GaInSb p–n heterojunction semiconductor nanowires were synthesized successfully via a simple chemical vapor deposition (CVD) method. Based on these nanowires, high-performance photodetectors were constructed with an external quantum efficiency of 104, a responsivity of 103 A/W, and a short response time of 2 ms in the infrared optical communication region (1.55 μm). These III-V NWs shows promising potential applications in integrated photonics and optoelectronics devices or systems.
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Enhanced Piezoelectric Property in Strained Anisotropic Layered Tungsten Ditelluride Nanoflowers
Authors: Masimukku Srinivaas , Wu Jyh Ming 
Published: February 2020

Layered transition metal dichalcogenides (TMDS) possess enormous attention in the field of catalysis, optoelectronic devices, sensors, and piezotronics owing to its wide range of chemical, electrical and mechanical properties. Numerous efforts have been made to develop nanostructured TMDS in solution-based methods. Here, we successfully synthesised layered tungsten ditelluride ( WTe2 ) nanoflowers (NFs) in solution phase approach. We further characterised WTe2 NFs and evaluated the piezoelectric properties using atomic force microscopy. The layered WTe2 NFs exhibited significant piezoresponse which may result due to its non-centrosymmetric structure. The unique piezoelectric property of the layered WTe2 is opening up the new field applications such as low-power consumption devices, ultrasensitive sensors, and piezoelectric nanogenerators.

Reference

Wenzhuo Wu, Lei Wang, Nature, 514, 470-474.
Recent Progress in SiC and GaN Power Devices
Authors: Sheng Kuang , Yang Shu , Guo Qing , Xu Hongyi 
Published: February 2020

Owing to low conduction/switching loss, high switching frequency and high operating temperature, wide bandgap SiC and GaN power devices are attractive for next-generation power electronic systems with increased efficiency and power density. Because of the superior performance, SiC and GaN power devices could be in position to compete with the mainstream Si power devices in a variety of applications, including household appliances, photovoltaic inverters, electric vehicles, data centers, etc. Despite numerous research efforts devoted to material growth, device fabrication and circuit demonstration in the past decades, wide bandgap power semiconductor devices are still confronted with challenges that need to be addressed through new structure design and advanced process development. In this talk, we will review recent progress in SiC and GaN power devices, including the following. (1) High-density of interface traps usually exist at the gate-oxide/SiC interface in SiC MOSFETs, presenting a critical challenge to the channel mobility and device stability. Interface engineering techniques for SiC MOSFETs (e.g. NO/N2O annealing, P incorporation, metal interfacial-layer, high-k dielectric deposition, etc.) and their impact on interface trap distribution as well as channel mobility will be discussed. (2) Long-term reliability of SiC MOSFETs with special focus on time-dependent dielectric breakdown (TDDB) will be presented. (3) We will introduce our latest progress in design and fabrication of super junction SiC devices, which can break the fundamental limit of the conventional unipolar devices. (4) In GaN-based lateral power devices, the 2DEG channel is an inherent normally-on channel, due to the spontaneous and piezoelectric polarization effects. To achieve fail-safe operation and simpler gate drive circuit, normally-off device technology including p-(Al)GaN cap, barrier recess and plasma treatment in the gate region will be introduced and compared. (5) Gate stack engineering techniques toward high-reliability GaN MIS-HEMTs/FETs will also be presented.
Effect of Wafer and Damaged Layer Thickness on Residual Stress and Bow of Free-Standing Gallium Nitride Wafers during Wafering Process
Authors: Park Jin-Seong , Shim Jae-Hyoung , Chun Kyung-Bin , Lee Jae-Eon , Shim Tae-Hun , Park Jea-Gun 
Published: February 2020

In recent years, free-standing gallium nitride (FS-GaN) wafers were researched due to high demand for power device, high brightness LED (HB-LED) and laser diode (LD). The GaN wafers grown by hydride vapor phase epitaxy (HVPE) have been used for the substrate of power device, HB-LED and LD because they demonstrated lower dislocation density (DD) than that of GaN wafers grown by metal-organic chemical vapor deposition (MOCVD). However, they still have residual stress and wafer bow, which lower the device productivity in mass production. To overcome these issues, the control of crystallographic quality and wafer bow are the key technologies. The crystallographic quality of the GaN wafer is mostly determined at the growth process. The bow of the wafer is determined by the difference in thermal expansion coefficient (TEC) between sapphire substrate and GaN, and it can be controlled at the wafering process. In this study, therefore, we investigated how the bow of the FS-GaN wafer is changed during wafering process. In particular, the effect of the abrasive size on the damaged layer thickness during lapping process was investigated and residual stress was calculated theoretically.
Two inch GaN wafers were fabricated on (0001) sapphire substrates by HVPE and separated by the laser lift-off (LLO) process. The bow of as-grown GaN wafer after LLO process was ranged from -300 to -100 um, which was determined by the residual thermal stress. The GaN wafer bow is changed during the wafering process, especially the lapping process. From the Stoney’s formula, it is notable that the thickness of substrate (tS) and sub-surface damaged layer (tSSD) can change the wafer bow.
Fig. 1 shows the wafer bow (black triangle), residual stress (blue square) of experimented GaN wafer and wafer bow calculated by the Stoney’s formula (red triangle). It was confirmed that the wafer bow was reduced as the thickness of GaN wafer reduced. In particular, the bow was inverted from concave to convex at the thickness of around 180 um. As the lapping process progressed, tS is reduced and tSSD is generated, which led to the change of bow to convex.
Fig. 2 shows the sub-surface damaged layer of the GaN wafer after lapping with 2-um diamond abrasives. It exhibits that the crystalline GaN layer was damaged by the diamond abrasives and changed to polycrystalline phase at the top surface. In addition, it indicates that the microcracks propagated into the wafer under the polycrystalline layer. Total thickness of polycrystalline layer and microcracks, tSSD, was around 1.09 um. Thus, the tSSD should be removed for achieving the damage-free GaN wafer.
In our presentation, we report how we achieved zero-bow FS-GaN wafer shown in Fig. 3, and how to control residual stress and optimize wafering process.
* This work was financially supported by the Brain Korea 21 Plus Program in 2017.

Figure 1