bluuebunny/crossref_metadata_2025 huggingface dataset:
Nanostructured Cu-Sn Alloy for Actively and Selectively Converting CO2 to CO
Authors: Ju Wenbo , Zeng Juqin , Rentsch Daniel , Ma Huan , Castellino Micaela , Bejtka Katarzyna , Pirri Candido F. , Vogt Ulrich F. , Battaglia Corsin
Published: February 2020

Many strategies have been proposed for carbon dioxide (CO2) reduction aiming to close the carbon cycle and compensate anthropogenic CO2 emissions. Electrochemical CO2 reduction has several advantages that it can be carried out under ambient conditions with water as the only additional feedstock, and electricity generated from renewable sources can be employed to achieve a fully sustainable route [1].

Copper (Cu) has unique features for electrochemically converting CO2 to a range of chemicals including hydrocarbons [2], but its selectivity for specific products is low. Especially, at a low or intermediate overpotential, the hydrogen evolution reaction (HER) dominates the overall process on polycrystalline Cu in aqueous solutions [3]. However, the selectivity of Cu can be tuned by introducing a secondary metal. Tin-modified nanostructured Cu (CuSn) electrocatalysts have been developed for electrochemically converting CO2 to carbon monoxide (CO). The doped Sn atoms in the topmost layer alloy with Cu, form a CuSn shell, and efficiently suppress the HER. By optimizing the Sn content in the CuSn layer and the nanostructure, the faradaic efficiency for CO reaches > 90 % at -0.7 V vs. RHE, and remains above 85 % in a wide potential range from -0.7 to -1.0 V [4]. However, the excellent selectivity for CO can be only observed at CuSn dendrites. When the CuSn catalyst has a particulate morphology, the selectivity for CO becomes much worse, even though the surface composition has the optimal Cu/Sn ratio. The CuSn particles are active for the HER at a low overpotential. Although the HER can be efficiently suppressed to a faradaic efficiency of less than 15 % at a high overpotential, the major products for CO2 reduction are both CO and formate (COOH-) [5]. This work highlights the importance of nanostructure and surface composition of CuSn catalysts for active and selective CO2 reduction.

Electrodes consisting of a three-dimensional porous architecture are prepared for a large active surface per unit geometric area. The CO production achieves a high partial current density of 4.9 mA·cm-2 at -0.8 V [4].

[1] Centi, G., et al. Energy Environ. Sci. 2013, 6, 1711-1731 [2] Qiao, J., et al., Chem. Soc.
Rev.
2014, 43, 631-675 [3] Li, C., et al., J. Am. Chem. Soc.
2012, 134, 7231-4 [4] Zeng, J., et al., submitted [5] Ju, W., et al., in preparation
Nickel–Cobalt–Phosphide Catalyst Derived from MOF-74 for Oxygen Reduction Reactions
Authors: Gao Xiaolei , Cui Zhenxing , Cao Lei , Yu Jianhua , Zhao Mei , Dong Hongzhou , Sui Jing , Dong Lifeng
Published: February 2020

In recent years, energy converting and storage systems have been playing a crucial role in alleviating the pressure of energy crisis. Oxygen reduction reactions (ORRs) play an important role in energy converting and storage systems, such as fuel cells and metal air batteries. Herein, it is critical important to develop high efficient and stable electrocatalysts for ORRs to replace platinum-based catalytic materials. In this work, nickel-cobalt bimetallic metal-organic framework (NiCo-MOF-74) and its derivatives (oxides, phosphide and sulfide) were synthesized and their electrochemical performances for ORRs were evaluated. It was found that the series of NiCo-MOF-74 products with rod-like structure show excellent electrochemical performance, especially the sulfide. The sulfide exhibits the onset potential of -0.14V vs Ag/AgCl. Therefore, the series of NiCo-MOF-74 derivatives have great potential in ORRs as highly active, stable, low-cost catalysts.
Electrochemicaly Assisted Separation of REE Magnetic Ions in the Microchannel
Authors: Kolczyk Karolina , Kutyla Dawid , Wojnicki Marek , Kowalik Remigiusz , Luty-Blocho Magdalena , Zabinski Piotr
Published: February 2020

Rare earth elements (REE) are interesting due to their magnetic, luminescence properties. They found an application in high technology e.g.: a radar, a sonar, a telescope, hybrid cars, as catalytic converters, television and computers screens, computer hard drives, wind turbines, etc. REE are produced both from primary and secondary sources. In hydrometallurgical processes, the most problematic step of those metals production is their separation. For this reason, it is desirable to improve the current processes via application of High Magnetic Gradient. It utilizes the different magnetic properties of rare earth metal ions to achieve separation by attraction or repulsion in an inhomogeneous magnetic field.

In this study, the using of elcectrochemical method combined with an inhomogeneous magnetic field allows for an enrichment of Ho3+ ions and then their separation from depleted aqueous solutions. The experiments were carried out in a microreactor produced by a 3D printing technology. The ions movement was carried out on a circular path due to the spiral arrangement of the microchannel. The inhomogeneous magnetic field in the channel was created by the placement of the microreactor in a laboratory electromagnet. During the flow conditions, the metal ions were exposed on the force coming from the gradient magnetic field and their separation into two streams was observed. First one consisting of the enrichment solution in magnetic ions and second one containing depleted solution. These solutions were collected and analyzed using UV/Vis spectrophotometry and MP-AES (Microwave Plasma-Atomic Emission Spectrometer).

In this work the influence of the applied current, direction of current field lines, residence time of the magnetic ions in the microchannel and their concentration on the efficiency of separation enrichment and depleted solution were examined.

Acknowledgment

The authors would like to thank Polish National Science Centre for the financial support provided by the grant: No UMO-2014/15/B/ST8/01528.
Biowaste-Derived Carbon Electrodes for Capacitive Deionization
Authors: Lado Julio , Ruotolo Luis Augusto Martins , L. Zornitta Rafael
Published: February 2020

Capacitive Deionization (CDI) is one of the most relevant emerging desalination technologies. CDI is based on the electrosorption of salts using a pair of electrically charged porous electrodes. In this way the CDI process consists on charging (ion removal)/discharging (ion desorption) cycles using the same operational principles of the supercapacitors. Therefore, CDI cells might potentially allow to recover part of the energy consumed in the desalination process while delivering drinking water.

One of the key elements in this technology are, as in the supercapacitor field, the electrodes. In accordance with this, intensive research has been conducted in order to find the best electrode candidates in terms of specific surface area (SSA), porosity, electrical conductivity, surface chemistry and optimized chemical surface charge of the electrode. The combination of these properties are expected to provide higher values of salt adsorption capacity (SAC) and average salt adsorption rate (ASAR). Moreover, it should be also remarked that one of the critical requirements in order to make CDI competitive with current desalination technologies (such as reverse osmosis or electrodialysis) is the cost of the electrode materials. In order to address this challenge, the preparation of carbon electrodes from abundant biowaste precursors was studied as a low cost and green alternative to more innovative carbon composite complex materials.

In this work the authors decided to evaluate different activation treatments of a biowaste precursor in order to obtain suitable activated carbons for capacitive deionization. The different structural properties (BET SSA, pore size distribution, chemical surface groups) of the synthesized AC’s were correlated not only with their electrochemical response (specific capacitance) but also with the CDI performance (SAC, electrosorption kinetics, charge efficiency and the energy consumption).
Removal of Silica from in-Situ Produced Water By Electrocoagulation
Authors: Roberts E.P.L. , Shu Tianpei , Fuladpanjeh-Hojaghan Behzad , Yasri Nael , Trifkovic Milana
Published: February 2020

Compared to water treatment by chemical coagulation, electrocoagulation produces less sludge, leads to only a small change of pH, and can have lower operating costs. Operating costs are a combination of operating labour, electrical power and replacemnt of the consumable metal electrodes. In this study we report the performance of EC for silica removal from in-situ produced water and blowdown, including the energy and metal consumption required per unit volume of treated water, under a range of operating conditions. The use of polarity reversal to control electrode fouling is investigated, as well as some novel operating conditions. With polarity reversal, the particle size distribution of precipitated coagulant changes depending on the frequency of the reversal. At high frequency there is less electrode fouling, but the particle size formed is smaller, so separation of the solids becomes more challenging. We use laser scanning confocal microscopy with pH sensitive fluourescent dyes to observe the precipitation process occuring in the pH boundary layer at the electrode surface. This approach reveals the influence of polarity reversal and mass transport on the coagulation process.
(Invited) Visible Light Driven Photoelectrocatalytic Degradation of Acid Yellow 17 Dye Using Thin Film Sn3O4 Flowers-like Nanostructurred Supporting Onto Ti
Authors: Zanoni Maria VALNICE BOLDRIN , Huda Adri , Suman Pedro H , Orlandi Marcelo Ornaghi , Torquato Lilian D. M.
Published: February 2020

Photoelectrocatalysis is a technique with consolidated principles that has gained prominence and has been successfully applied in organic compound oxidation, microorganism inactivation, CO2 reduction energy[1]. Their application on wastewater treatment is based on the use of a semiconductor that generates charge carriers (e-/h+) when irradiated by light energy equal or greater than its band gap and simultaneously biased by a gradient potential. The recent progress of photoelectrocatalysis is intimately related to the advances in materials science, especially in nanomaterials. Other challenges are the development of stable semiconductor materials able to be activated by solar irradiation.

Among the numerous types of semiconductors used as photocatalysts, tin oxides with diﬀerent forms (SnO, SnO2 and Sn3O4), present wide-spread applications, because of its abundant availability and non-toxicity. The aim of this work was to perform the synthesis of a Sn3O4 ordered structure under mild operational conditions to further apply it in the photoelectrocatalytic degradation of a dye, taken Acid Yellow 17 as a model of textile dye treatment. The hierarchical form of Sn3O4, with the flower-like nanostructure with triclinic Sn3O4/Ti, was successfully prepared using microwave-assisted hydrothermal method at pH 6, in 150 oC. The as-prepared Sn3O4 was deposited in the titanium substrate using spin coating methods. The Sn3O4 /Ti nanostructure demonstrated high photocatalytic activity in the visible wavelength (λ>390 nm), calculated band gap of energy 2.4 eV by diffuse reflectance. The electrode was successfully applied on degradation of 10 ppm solution of AY17 (pH 4) at low bias potential (0.5 V) and visible light irradiation reached complete discoloration after only 30 min of treatment. The TOC removal reached 83% after 4000 s-1 of light irradiation time. Therefore, the flower-like nanostructured Sn3O4 proved to be efficient in the visible light driven photoelectrocatalytic degradation of AY17 dye, which represents an energy-saving option for its future treatment and removal of the environment.

Acknowledgments

We acknowledge the financial support from INCT-DATREM, process FAPESP 14/50945-4 and CNPq 465571/2014-0.

References

[1] G. G. Bessegato, T. T. Guaraldo, J. F. de Brito,M. F. Brugnera, M. V. B. Zanoni, Electrocatal. 2015 6, 415–441.
3D Modelling of the Transport Phenomena in a Parallel-Plate Electrodeionization Reactor through CFD
Authors: Enciso Rubi , Rodríguez-Torres Israel
Published: February 2020

CFD has been used as a useful tool for the description of the phenomena occurring in electrochemical reactors. The present research studies the electrodeionization process from a 3D perspective, coupling the convection, diffusion and migration phenomena involved in the electrodeionization process using COMSOL Multiphysics and a validation of the simulation process is obtained using Digital Image Analysis and Electrodeionization experiments.

The used reactor is a parallel plate reactor, previously used for an electrodialysis process with good results, the total volume of each of the 4 compartments ( one for diluted-treated solution, one for the concentrated-waste solution and two electrodic rinses to close the electrical circuit) is of about 19.2 mL. The diluted compartment is filled with IRA-67 ion exchange resin ( 0.5-0.75 mm of diameter) previously conditioned and hydrated. The treated solution is a 20 ppm fluoride solution from NaF and was pumped into de diluted and concentrated compartments at a velocity that allowed a one minute Time of Residence.

The simulation was carried out with a 3D model of the reactor using its real measures, only the diluted and concentrated compartments were modelled. The flow of the solution in the concentrated compartment was considered as laminar and in the diluted compartment ( filled with ion exchange resin) a Brinkman-Darcy condition was applied. Nerst-Planck equations were used to describe the transport of the ionic species in the compartments and the flow through a ion exchange membrane.

The results show a good flow distribution,as well as a good ion transport. The simulations, confirmed the experimental results. The analized data is very similar in flow distribution and mass transport in the compartments. The results were analized in a quantitative and qualitative form. The validation of this simulated results will allow the improvement of some problematic zones in the reactor and the methodology developed can be useful to other electrochemical reactors.
Design of a Filter-Press Flow Cell with Parallel Plate Electrodes to Guarantee Homogeneous Current Distributions in Turbulent Flow Conditions. the Importance of Mathematical Modeling Coupled to a Printing 3D
Authors: Pérez-Segura Tzayam , Arenas Fernando , Nava José Luis , Ponce de León Carlos , Walsh Frank C
Published: February 2020

The characterization of the reaction environment in continuous electrochemical reactors is necessary to optimize the operational conditions of electrolysis, such as hydrodynamics, current density, residence time, conversion of the electro-active species, among others. In this context the mathematical modeling followed by experimental trials permit to construct models of operation that guarantee the efficiency and yield of the desired reaction. In this work we are interested in the design of a filter-press flow cell to be used in the evaluation of a nickel deposit on a stainless steel cathode. The goal is to minimize the edge effects at the inlet and exit of the cell. To achieve the above, a plastic mesh that avoids the jet flows in the entrance was designed; such design also diminishes the distribution at the beginning of the electrodes. A theoretical analysis of tertiary current distributions was carried out using previous experimental data of nickel deposition in acidic media. Tertiary current distribution analysis was made coupling the RANS equations with the k-epsilon turbulence model and the Launder-Spalding-like equations using wall functions. Different geometric configurations and operational conditions (flow rate, applied current density, etc.) were evaluated founding that the turbulence promotor and flow distributors posses and important role in the performance of the cell. The cell and its components were printed in 3D from the CFD simulations. Close agreement between experimental and theoretical current density distributions were attained. Primary and secondary current distributions were also calculated. The solution of the above mentioned equations was obtained by using a commercial software via finite element method.
(Invited) Water Transport Along Si/Si Direct Wafer Bonding Interfaces
Authors: Rieutord François , Tardif Samuel , Nikitskiy Ivan , Fournel Frank , Tedjini Marwan , Larrey Vincent , Bridoux Claudine , Morales Christophe , Landru Didier , Kononchuk Oleg
Published: February 2020

Direct bonding interfaces exhibit, before annealing, a narrow density gap due to the contact interactions of facing surface asperities and their incomplete compression. This gap makes a narrow channel (width<1nm) along which water is able to move. This is evidenced clearly from the defect distribution in Si/Si hydrophilic bonding showing clearly a rim of defects whose extent is related to the kinetics of water penetration [1]. A simple model of capillary flow has been used in a first attempt to describe the kinetics of water penetration [2] under such very high confinement but this model fails to reproduce some of the experimental observations as e.g. the increase of wetting front width with penetration length, or the water distribution in case of reversed flow. We shall describe these experimental results, recording kinetics of water flow under varying amplitude and direction of chemical potential gradients (e.g. relative humidity) and different temperatures. These experiments allow a direct test of the dependence of flow kinetics with various parameters such as viscosity and surface energies.

Finally we shall establish from basic principles the equation of propagation, which is shown to be a porous medium equation type [3]:

∂ρ/∂t= D/2ρ0 ∂2ρ
2
/∂x2

where ρ is the interface areal density of water and D a constant “diffusion” coefficient depending on the wetting characteristics of the surface , the geometry of the gap and the water viscosity. Solutions of this equation will be given with boundary conditions corresponding to the wafer bonding interface situation. They exhibit features intermediate between sharp water front propagation (as described by Lucas-Washburn type of models) and diffusion equation, in agreement with experiments.

REFERENCES

[1] M. Tedjini et al. Appl. Phys. Lett. 109, 111603 (2016)

[2] F. Rieutord,et al ECS Trans. 2016
volume 75(
9) ,
163-167

[3] J. L. Vazquez, The Porous Medium Equation: Mathematical Theory, Clarendon Press Oxford (2007)
(Invited) Monolithic Integration of Si-CMOS and III-V-on-Si through Direct Wafer Bonding Process
Authors: Lee Kwang Hong , Zhang Li , Wang Bing , Wang Yue , Sasangka Wardhana , Lee Kenneth E. , Fitzgerald Eugene A.
Published: February 2020

Integration of Si-CMOS and III-V compound semiconductors (with device structures of either InGaAs HEMT, AlGaInP LED, GaN HEMT or InGaN LED) on a common Si substrate is demonstrated. The Si-CMOS layer is temporarily bonded on a Si handle wafer. Another III-V/Si substrate is then bonded to the Si-CMOS containing handle wafer. Finally, the handle wafer is released to realize the Si-CMOS on III-V/Si substrate. For GaN HEMT or LED on Si substrate, additional wafer bonding step is required to replace the fragile Si (111) substrate after high temperature GaN growth with a new Si (001) wafer to improve the robustness of the GaN/Si wafers. Through this substrate replacement step, the bonded wafer pair can survive the subsequent processing steps. The monolithic integration of Si-CMOS + III-V devices on a common Si platform enables new generation of systems with more functionality, better energy efficiency, and smaller form factor.
High-Energy Lithium-Ion Hybrid Supercapacitors Composed of Perovskite Type BiFeO3/C Anodes and MOF-Derived Carbon Cathodes
Authors: Dewan Moumita , Majumder Subhasish B
Published: February 2020

A lithium-ion hybrid supercapacitor (Li-HSC) comprising a Li-ion battery type anode and an electrochemical double layer capacitance (EDLC) type cathode has attracted much interest because it accomplishes a large energy density without compromising the power density. But instead of using a conventional Li-ion battery type anode we introduce a perovskite based anodes where ions migrate through the perovskite lattice, allowing for a variety of electrochemical applications. It is still unknown how lithium ions interact with the perovskite structure during the charging discharging process. In this work, carbon coated BiFeO3 (BiFeO3/C) with a unique mesoporous structure is synthesized through autocombustion using glucose as carbon source and metal-organic framework derived carbon (MOF-C) are prepared, adopted as the anode and the cathode for Li-HSCs. The mesoporous BiFeO3/C microspheres exhibit higher Coulombic capacity, excellent rate performance and a long cycling life because of storage reactions based on conversion instead of Li+ insertion or alloying. The BiFeO3/C structure shows a reversible specific capacity of 708 mA h g−
1 at a current density 10 mAg-1after 100 discharging-charging cycles with excellent rate performance. The MOF-C achieved the specific capacity of 250.9 F g−
1 at a current density of 0.1 A g−
1. At a high current density of 2 A g−
1, 90% of the initial capacity could be retained after 1000 discharging–charging cycles, suggesting excellent cycle stability. The Li-HSC comprising a BiFeO3/C anode and a MOF-C cathode boasts a large energy density with a high power density o and 90% of the capacity is retained at a current density of 2 A g−
1 after 1000 charging discharging cycles. The high energy and power densities of the Li-HSCs of BiFeO3/C//MOF-C demonstrate a large potential in energy storage.
Impact of CoII/NiII Ratio in PBA Grown Onto Graphene Oxide over the K-Ion Storage Capability in Acid Aqueous Electrolytes
Authors: Vazquez Juvencio , Acevedo-Peña Prospero , Oliver-Tolentino Miguel Angel , Ramírez Guadalupe , Reguera Edilso
Published: February 2020

Metal hexacyanoferrates (MHCFs), known as the Prussian blue analogues, with the general chemical formula AhMk[Fe(CN)6]r nH2O (where A = alkali metal cation, M = transition metal cation), are promising materials for electrocatalysts, charge-storage and sensor applications due to their unique structural characteristics such as three-dimensional (3D) network with a distinct tunnel and pore structures. It is well known that MHCF can exhibit solid state redox reactions associated with electrochemical insertion/extraction of various ions (Li+, Na+, K+, NH4
+, Mg2
+, etc.). For this reason, Prussian blue Analogues are currently being widely employed as active materials for alkali ion batteries and supercapacitive energy storage. In this work, the nickel(II)/cobalt(II) hexacyanoferrate(III) (Ni/Co-PBA)/graphene oxide composites were synthesized by co-precipitation method. XRD, FT-IR and Raman carried out their structural characterization, and morphological characterization was performed using SEM and TEM. The cyclic voltammetry results show two faradic processes associated to FeIII/ FeII and CoII/ CoIII redox couple which is accompanied by K+ ion insertion in and out of the cyanobridged metallic framework to maintain local charge neutrality. Adittionally, Electrochemical impedance spectroscopy was employed to study the impact of CoII/NiII ratio on the apparent diffusion coefficient for K+ in the material. The composites synthesized exhibited higher specific capacitance in acid medium within the potential range from 0 to 0.85 V vs Ag/AgCl (3M NaCl).
Modification of Carbon/Electrolyte Interface for Electrochemical Capacitor Improvement
Authors: Frackowiak Elzbieta , Slesinski Adam , Fic Krzysztof
Published: February 2020

Electrochemical capacitor (EC) parameters are affected by the amount of charge reversibly accumulated at electrode/electrolyte interface, electrode material, type of electrolyte and its electrochemical stability as well as cell construction. It has been proved that asymmetric configuration, i.e., various electrode materials for positive and negative electrodes or hybrid configuration where different charge storage mechanism is utilised on both electrodes can bring a significant capacitor enhancement. Both approaches, it means typical electrostatic attraction of ions on various electrode materials and pseudocapacitive phenomena originating from electrode materials and/or electrolyte have been considered.

Carbon electrode surface has been modified by the ammonia adsorption. Dry and wet preliminary oxidation as well as thermal treatment of carbon materials have been realized for more efficient ammonia trapping into pores. A detailed analysis of nitrogen functionalities and carbon texture was performed. Donor-acceptor nature of modified carbon allows a capacitor voltage to be extended. The equilibria state and protective layers formed at the carbon/electrolyte interface give the possibility to reach operating capacitor voltage of 1.8 V. This unique but simple strategy enables a self-controlled pH gradient within the capacitor system. It is assumed that bulk of electrolyte has a neutral character (lithium sulfate) whereas both electrode interfaces (+) and (-) indicate acidic and basic character, respectively. Expected gradient of pH between positive and negative electrode is at least 6. Excellent reversibility during long-term galvanostatic cycling (10 000 cycles) and floating has been confirmed. Furthermore, this configuration eliminates the need for physical separation of ions (such as an ion-exchange membrane) to decelerate their mixing and improves the power density of the device.

Another approach for capacitor operation improvement is selection of suitable ions at electrode/electrolyte interface considering their ‘hard’ and ‘soft’ character.
Insights into Electrochemical Capacitors Ageing at Different Voltage/Current Conditions
Authors: Fic Krzysztof , Piwek Justyna , Platek Anetta , Frackowiak Elzbieta
Published: February 2020

Electrochemical capacitors (ECs) are high-power energy storage devices able to operate for thousands of cycles. Nevertheless, their calendar and cycle life is limited, especially when high voltage is applied. On the other hand, that parameter (voltage, U) significantly increases their energy values according to the equation E=0.5CU2. Therefore, there is a particular need for the understanding of ageing and performance fade reasons in order to prolong supercapacitor operation.

Herein, the effect of ageing-related phenomena in water-based ECs is widely studied. LiNO3 at various concentrations (1M and 5M) was utilized. According to the ageing criteria (IEC 62391-1) AC/AC systems were cycled at elevated voltages (1.5-1.7V) using floating test until 20% of initial capacitance fade. It has been observed that voltage increase by 0.1V interval results in a shortening of the operation time for about 50%, reflected by resistance increase and distorted voltammetry response. However, the utilization of highly concentrated LiNO3 solution (5M) extends the electrochemical performance from 206h recorded for 1M LiNO3 to 312h. In order to insightfully describe ageing phenomena, physicochemical carbon properties were monitored by post-mortem approach. It has been observed that remarkable SBET decrease is observed on positive electrode only. The higher voltage applied the lower SBET surface area of positive electrode, whatever the electrolyte concentration. TPD studies provided more the information about the surface of the AC electrode. Essentially, the oxidation of positive electrode was higher than the negative one Moreover, it is predicted that negative electrode suffers from some morphological transformations rather than surface functionality changes, likely caused by hydrogen evolution.

It seems that p
ost-mortem approach which involves diversity of physio-chemical techniques can be definitely treated as an insightful approach for ageing research in the real capacitor system.
(Invited) Continued Device Miniaturization Enabled By New Materials Innovations and Advanced Patterning Schemes
Authors: Saly Mark
Published: February 2020

The microelectronics industry continues to experience high demand for new materials innovation driven by the need for solutions in the advanced patterning space. As device features and critical dimensions continue to shrink, the complexity of chip fabrication increases at an exponential rate. With this increase in complexity, many issues and challenges arise. For instance, with more steps and smaller dimensions, Edge Placement Error (EPE) becomes a key limiting factor towards enabling future nodes. EPE is the error between the intended and actual placements of desired features in a device. Smaller device features afford tighter tolerance specifications and smaller error budgets. Advanced devices require multiple patterning steps, which increase the potential for errors and misalignments. EPE can have detrimental effects on device performance due to contact shorts and open circuits, often leading to poor device yields. One way to limit the effects of EPEs is to use self-alignment patterning schemes. Selective deposition and selective etch processes are both key enablers for the development of self-aligned processes in semiconductor fabrication. Figure 1(a) shows a standard contact patterning flow without self-alignment. Selective deposition can relax the lithography and overlay requirements, as shown in Figure 1(b), and greatly decrease EPE by enabling self-alignment patterning schemes. Furthermore, as devices continue to shrink, conventional etch processes suffer from poor etch control and line edge roughness and thus can also contribute to EPE for future nodes. Atomic layer Etch (ALE) is an emerging etch technique that uses two or more precursors in a sequential fashion where the surface modification during precursor exposure is self-limiting leading to highly controllable etches that are very smooth and conformal. In addition, the filling of high aspect ratio features is also a key enabler to complicated multi-patterning flows (such as reverse tone patterning). Although there has been remarkable progress on these fronts, further developments are needed to ensure the scalability of microelectronics devices. This presentation will focus on insights and recent research results in the quest for enabling new patterning schemes through the development of new selective ALD processes, thermal ALE processes, and methods for the gap fill of high aspect ratio features.

Figure 1
Multiple-Parameter-Detected Silicon-Based Photonic Crystal Biosensor Based on Defect-Mode Coupling
Authors: Feng Shuai , Chen Xiao , Li Chuanbo , Wang Yiquan
Published: February 2020

A high-sensitivity, high-resolution, multi-working channel and real-time detection typed one-dimensional photonic crystal biosensor is proposed. Through changing the slit’s width between two adjacent silicon layers,multiple defects with different resonant wavelengths can be designed. The biosensor is based on the air-mode cavity which means light energy is greatly limited to the defect channels. Owing to the strong localizing capability of the defects and the forceful light-material interaction, a subtle alteration of the liquid’s refractive index can make the resonant wavelength and transmittance changes significantly. Due to the mutual coupling effect of multiple defect modes, when the liquid’s refractive index around a defect changes, the resonant wavelengths of all the device’s defect modes and the corresponding transmittances will be affected. Different liquid samples can flow freely within respective slits, so they can be measured in real time and at the same time. Through analyzing the alterations of the wavelengths and transmittances, the concentration information of a variety of liquid samples can be measured through a wide transmission spectrum measurement.
(Invited) First Principles Study of Electron Mobility of Mg2Si and Beyond
Authors: Meng Fanchen , Ma Jinlong , He Jian , Li Wu
Published: February 2020

Mg2Si is an important parent compound of green thermoelectric materials for medium temperature range applications of power generation. Notwithstanding decades of extensive study on the experimental side, in-depth theoretical understanding of the phonon spectrum and the thermal transport in Mg2Si from a first-principles perspective was only attained recently. Furthermore, there lacks a feasible first-principles methodology of calculating the electrical transport properties of Mg2Si. We here present the results of ab initio calculations on the electrical transport properties of Mg2Si. The microscopic electrical transport parameters such as mobility and mean free path are calculated within the framework of Boltzmann Transport Equation (BTE) in conjunction with ab initio calculations of electron-phonon coupling constants. Both the BTE and the relaxation time are solved iteratively, so empirical or semi-empirical potentials or constant relaxation approximations are no longer needed. The calculated results are in good agreement with experimental reports. The applicability of the present methodology to other thermoelectric materials will be also discussed towards fully calculated figures of merit.
Very High Aspect Ratio (AR>10) through Glass Hole (TGH) Filling in Stagnant Condition By Using DC Plating for Advanced Interposer Applications
Authors: Chang Yiu-Hsiang , Chen Jie-Chi , Tseng Julie , Lin James , Chang Ya-Huei , Huang Meng-Chi , Lin Hung-Yi , Zhang Lu
Published: February 2020

High aspect ratio (AR) through glass interposer filling has been widely investigated and developed in the recent years. Most efforts put on blind via filling by using the agitation (i.e., air agitation, cathode rotation, paddle agitation, etc.) or periodic pulse reverse (PPR) plating technique to help improvement of filling performance and enhancement of mass transfer of each component in plating electrolyte. However, high aspect ratio through hole filling has been less addressed because the void or seam defects are easily formed in the through hole. In this study, the AR>10 (AR~12) through glass hole filling with defect-free has been successfully demonstrated under stagnant condition, as shown in Figure 1 by using DC mode of fixed current density plating. Based on the operation condition, the equipment design is simple and the lifetime of additives could be long. Furthermore, the thickness difference between Cu overburden (3.51 μm) and dimple (2.88 μm) is around 0.7 μm, implying that the Cu surface is nearly flat, as shown in Figure 2. This achievement is because the additive of leveler could effectively inhibit the Cu deposition on the Cu seed layer surface, but it does not inhibit Cu deposition in the through hole center. Therefore, the butterfly pattern could be formed in the early stage of Cu filling. Besides, the relatively flat Cu surface is beneficial to post Cu removal process, such as expensive CMP process.

Figure 1
(Invited) Appearance of High Mobility Carriers in Strained Epitaxial Germanium
Authors: Myronov Maksym
Published: February 2020

Carrier mobility is one of the most important parameters of any semiconductor material, determining its suitability for applications in a large variety of electronic devices including field effect transistors (FETs). Bulk or 3D, Germanium (Ge), with its very high intrinsic hole and electron mobilities of 1900 and 3900 cm2V-1s-1 at room temperature, respectively, is the most promising candidate material to replace Si channels in future complementary metal oxide semiconductor (CMOS) devices. When one or more of the dimensions of a solid are reduced sufficiently to nanometer range, its physicochemical characteristics notably depart from those of the bulk solid. With reduction in size, novel electrical, mechanical, chemical, magnetic, and optical properties can be introduced. The resulting structure is then called a low-dimensional structure or system.

Biaxial compressive strain in nm scale thick Ge epilayer narrows its band gap and causes the appearance of a quantum well (QW) in the valence band. Holes confined in the strained Ge QW form a two-dimensional hole gas (2DHG) and have an increased mobility due both to their lower effective mass and reduced scattering factors in this material system. During the recent years a major breakthrough have been achieved in enhancement of carrier mobility in strained epitaxial Ge grown on a standard Si(001) substrate. Extremely high room- and low-temperature 2DHG mobilities of up to 4,500 cm2V-1s-1 and 1,500,000 cm2V-1s-1, respectively, have been demonstrated. These hole mobilities are the highest not only among the group-IV Si, SiGe, Ge, SiC and Diamond semiconductors, but also among p-type III–V, II–VI and emerging 2D materials.

The 2DHG mobilities in strained Ge are already sufficiently high to fabricate sub-100 nm electronic devices and demonstrate ballistic transport therein at or around room temperature. This material will be an excellent platform for scientists to discover new quantum phenomena and applications.
(Invited) Catalytic Chemical Vapor Deposition Technology for Low Temperature Processing of Thin Film Transistors
Authors: Hong Wan-Shick
Published: February 2020

For bendable and wearable device applications, it is necessary to ensure a sufficiently low processing temperature, usually one that is lower than the glass transition temperature of ordinary plastic sheets. However, it is very challenging to obtain inorganic thin films that contain an acceptable level of electronic defects at such a low temperature. Various attempts have been made to improve the electrical characteristics of the low temperature films, but most of the efforts slowed down the deposition rate considerably.

Catalytic chemical vapor deposition technique (Cat-CVD) has been known for its versatility and advantages such as a fast film growth rate and a high efficiency of gas utilization. These assets, combined with the absence of the atomic-scale damage caused by the bombardment of the charged particles, make this method attractive to applications in low temperature processing of the thin film transistors. Although this technique is still struggling to overcome several obstacles on its way to industrial implementation, it is a powerful research tool that can shed a light not just to finding interesting phenomena when various combinations of process parameters are tried, but also to understanding the behavior of radicals and atoms on the low temperature surfaces.

In this presentation, models of film growth in the catalytic chemical deposition process are discussed, and recent studies, including a surface pre-treatment, on applications to thin film transistors are surveyed.
(Invited) New p-Type Oxide Semiconductor with High Hole Mobility over 7 cm2/Vs Formed By Solution Process
Authors: Cho Sung Haeng , Nam Sooji , Hwang Chi-Sun , Lee Su-Jae
Published: February 2020

We report new p-type metal oxide semiconductor thin-film transistor with high field-effect hole mobility fabricated in solution process in this work. Metal oxide semiconductors have long attracted large attention as large-area electronic devices by virtue of high electrical and optical performances such as transparency, large electron mobility, good uniformity and low-temperature processability since the pioneering work of Prof. Hosono group in 2004, and their mass production has now been successfully realized in the active matrix backplane of flat-panel or flexible display. Few p-type metal oxide semiconductors with high performance, however, have been reported compared with n-type metal oxide semiconductors such as InGaZnO, InZnSnO, etc. This is mostly ascribed as the localization of valence band maximum which mainly consists of oxygen p orbitals. To enhance the dispersion of valence band, it has been theoretically proposed that the filled diffuse metal d or s orbital to hybridize with oxygen 2p orbital can be utilized and indeed it was experimentally demonstrated that Sn 5s orbital and Cu 3d orbital played such a role in SnO and CuO, respectively. But, SnO phase is very vulnerable to disproportion reaction to metallic Sn and SnO2 which behaves as an n-type semiconductor so that the process window to realize it in electron devices was very narrow and the electrical performance in the devices such as thin-film transistor was very limited, e.g low on/off ratio. Inspired by the theoretical work of high throughput materials screening performed by the first principles calculation, we fabricated the alkali metal doped SnO thin-film with solution process and low-temperature annealing less than 400 oC. We found that the oxidation state of Sn in thin-films changed from +4 state (SnO2 phase) to +2 state (SnO phase) depending on the content of alkali metal ions from x-ray photoelectron spectroscopy (XPS). Furthermore, Hall-effect measurement indicated the type conversion of the majority carrier from n-type to p-type as the content of alkali metal ion increases, in consistence with XPS results. The high hall mobility of 51 cm2/Vs was obtained at the optimal alkali-metal ion doped SnO thin film and we successfully fabricated thin-film transistors with alkali-metal ion doped SnO with a field-effect hole mobility over 7 cm2/Vs. We hope that this work will contribute to open a new era for transparent large area electronics based on oxide semiconductors with high functionalities such as complementary logic circuit.
(Invited) Development of Ultra-Wide Bandgap Amorphous Oxide Semiconductors for Future Electronics
Authors: Kim Junghwan , Hosono Hideo
Published: February 2020

Over a decade, amorphous oxide semiconductors (AOSs) have been significantly developed. And, they are already employed in flat panel displays (FPDs), including LCDs and OLED displays. However, a longstanding issue such as bias-stress, illumination stress, e.g. NBS, NBIS, PBS, is not yet fully resolved. While, transparent or flexible electronics, recently, attract much attention for next generation. To realize practical transparent or flexible electronics, stability of conventional AOSs should be improved much than now. For instabilities of AOSs, many phenomenalistic cases have been reported, but their origins and mechanisms have not been theoretically elucidated. But, it is clear that all instabilities result from external factors such as illumination, hydrogen diffusion, humidity and electrical bias. Thus, it can be said that the material with less sensitivities to a variety of external factors exhibits higher stability.

We recently demonstrated a highly photo-stable TFT consisting of an ultra-wide bandgap AOS (UWB-AOS) based on a-GaOx [1-3]. The UWB-AOS has a low sensitivity against visible light due to its very wide optical bandgap of ~4.0 eV. However, a wider bandgap AOSs tend to have low mobility or difficulty in doping electrons. As shown in Fig. 1, the AOSs comprising the cations of relatively large principle quantum number have a relatively high mobility of >20 cm2/Vs. However, they have a narrow band gap (Eg) of ~2.5 eV. Therefore, a widening the Eg by decreasing only the valence band maximum (VBM) level would be the best approach to obtain high-performance UWB-AOSs.

Details, including the relation between electronic structures and stabilities, will be presented at the conference.

References

[1] J. Kim el al., SID Symposium Digest of Technical Papers 47 (2016) 951.

[2] J. Kim et al., NPG Asia Materials 9.3 (2017) e359.

[3] J. Kim et al., Active-Matrix Flatpanel Displays and Devices (AM-FPD), 2017 24th International Workshop on. IEEE, 2017.

Figure 1
(Invited) Progress in Flexible 2D Nanoelectronics
Authors: Park Saungeun , Zhu Weinan , Akinwande Deji
Published: February 2020

Over a decade, two-dimensional (2D) van der Waals crystal materials have been intensively studied in the electronic device community for their attractive physics and various electronic applications such as the Internet-of-Things (IoTs) and wearable electronics. Particularly, their robust mechanical properties with the intrinsic strain limit of ~20% and wide range of saturation velocity of ~108 cm/s facilitate the future flexible nanoelectronics. Graphene, the first pioneering 2D material, is believed to be promising for high frequency flexible applications due to its high mobility and flexibility. However, its semi-metallic band structure limits graphene in digital applications that require the evident current On/Off ratio. On the other hand, the Molybdenum disulfide (MoS2), which has sizable bandgap of 1.3 ~1.9 eV, has been demonstrated for high current On/Off ratio over 108, which indicates its promising digital/logic systems wth low power operation. However, its high frequency digital applications are limited by its low mobility and n-type unipolar transport. The black phosphorus has been intensively studied due to its sizable bandgap ranging from 0.3 to 2 eV and high carrier mobility reaching to 1000 cm2/Vs, which can facilitate the development of high frequency digital applications. In this work, we demonstrate the high frequency operation of flexible 2D materials-based transistors. Graphene transistors on flexible willow glass substrate shows outstanding 95 GHz intrinsic cut-off frequency, and its calculated saturation velocity is ~8.4 ×106 cm/s, which is the highest for any flexible transistor on any material system. RF measurement of MoS2 transistors with the 500 nm channel length on flexible polyimide substrate shows 5.6 GHz intrinsic cut-off frequency and 3.3 GHz power gain. Multilayered BP field-effect transistor with 500 nm channel length shows 17.5 GHz and 14.5 GHz for intrinsic cut-off frequency and power gain, respectively. All of these studies for 2D materials-based transistors on flexible substrates clearly represents the state-of-the-art progress of the GHz operation of flexible transistors as well as wide GHz range of frequency operations, which pave the path toward wireless communication flexible applications and IoTs. In addition, paper substrates have been investigated for future electronics due to its cost-effective, eco-friendly and flexible features. With polyimide coating layer on commercially available paper substrates, we could make wet-processable paper substrate with low surface roughness for short channel length fabrication. We represent CVD graphene and MoS2 transistors on paper substrate, which shows the first GHz FETs operation on paper substrates.