bluuebunny/crossref_metadata_2025_split huggingface dataset:
Electroforming on Additively Manufactured Mandrels
Authors: Zheng Zhaohan , Aghili Sayed MohammadAli , Wüthrich Rolf 
Published: May 2020

Manufacturing industry faces recently a new challenge. Production of parts require, for various reasons, more and more low batch size production, sometimes even batch size one. Not only the batch size is reduced, but a given design has to be produced in lower on lower number too. If previously only prototyping required batch size one prodcution, the new trend of mass personalization requires it as well.
Manufacturing technologies developed over the past decades are able to produce cost effectively very complex products in high series. Low batch series production is often not possible or very costly. Additive manufacturing is a promising answer to this challenge. Additive manufacturing equipment represent however, in case of metal printing, very high investment costs and usually significant post-processing after printing is needed. An alternative way to create complex 3D printed parts in low volumes could be to use electroforming. Electroforming is commonly used to form parts on a model or, as termed in industry, a mandrel. Using additive manufacturing to create this mandrel could be a viable and cost-efficient solution. Since electroforming require less energy and less expensive equipment, it can be potentially used to create precise 3D structures. In order to create a 3D shape using electroforming.
Electroforming has its own challenges. As the thickness of the electroforming increases, voids build up and create a rough, uneven surface that has undesirable physical properties. The mass transfer at the micro-scale also changes the contribution of migration, diffusion and convection phenomena due to the scaling effect [1]. In order to produce complex and micro-scale features with acceptable quality, profile and characteristics, this paper discusses some significant factors and several methods for the improvement.
By applying appropriate potential and rotation on the mandrel during the electroforming process, deposition thickness ranging from few to several 100 microns with very low surface roughness (few microns Ra) could be achieved. The deposit thickness was very consistent too (less than 1% variation of the complete part). The homogeneity of the thickness was further investigated for various geometries to determine the limitations of the methodology.
[1] Angel, K., Tsang, H. H., Bedair, S. S., Smith, G. L., & Lazarus, N. (2018). Selective electroplating of 3D printed parts. Additive Manufacturing, 20, 164–172. doi: 10.1016/j.addma.2018.01.006
New Materials to Battle the Transistor Interconnect Bottleneck
Authors: Nies Cara-Lena , Natarajan Suresh Kondati , Nolan Michael 
Published: May 2020

With ever decreasing transistor size, materials that combine both diffusion barrier and liner material properties are needed to successfully electroplate Cu and thus beat the current interconnect bottleneck. In order to facilitate coating of high aspect ratio vias, the material should be as thin as possible. One possibility to achieve this is presented in this study, where we investigate through density functional theory, the behavior Cu on Ru-doped and Ru passivated ε-TaN (1 1 0). Initially, the adsorption, diffusion and association of one and two Cu atoms on the different surfaces was studied in order to probe the early stages of film growth. This showed that, while surface diffusion of atoms was more favourable on the Ru-passivated surface, the Ru dopant acts as a nucleation site for Cu, with atoms preferentially diffusing towards it.
In order to understand the mechanism of film growth on this surface in more detail and to fine-tune the barrier and liner properties of the material, the effect of different percentages of surface doping were studied. Further, the behavior of Cu13 and Cu29 clusters on different doped surfaces and on the passivated surfaces was investigated. In particular, the study focused on the pathways toward agglomeration as well as the associated activation energies. We find that on a Ru doped surface the atoms agglomerate spontaneously to form a two-layer film, whereas they remain in a monolayer on Ru-passivated TaN (1 1 0).
(Invited) Ambipolar Quantum Dots in Planar Silicon
Authors: Sousa de Almeida Antonio , Zwanenburg Floris Arnoud 
Published: May 2020

We create ambipolar quantum dots in planar silicon nanoscale transistors. We first investigate the conformity of Al, Ti and Pd nanoscale gates by means of transmission electron microscopy [1]. Next we define low-disorder electron quantum dots with Pd gates [2], and depletion-mode hole quantum dots in undoped silicon [3]. For the latter we use fixed charge in a SiO2/Al2O3 dielectric stack to induce a 2DHG at the Si/SiO2 interface. The depletion-mode design avoids complex multilayer architectures requiring precision alignment and allows directly adopting best practices already developed for depletion dots in other material systems. Finally, I will show ambipolar charge sensing: we have fabricated a single-electron transistor next to a singlehole transistor, and tuned both quantum dots to simultaneously sense charge transitions of the other quantum dot. With active charge sensing, the single-electron transistor can be tuned to detect the few-charge regime in the electron quantum dot. [4].
[1] P. C. Spruijtenburg et al., Nanotechnology, (2018).
[2] M. Brauns et al., Scientific Reports 8, 5690, (2018).
[3] S. V. Amitonov et al., Applied Physics Letters 112, 023102 (2018).
[4] A.J. Sousa de Almeida et al., https://arxiv.org/abs/2001.05045.

Figure 1
Novel HfO2-Based Multilayer Stack for Devices with Enhanced Capacitance
Authors: Moon Taehwan , Jo Sanghyun , Nam Seunggeol , Lee Yun Seong , Kim Sangwook , Lee Kwang-Hee , Heo Jinseong 
Published: May 2020

Recent discovery of ferroelectricity from non-centrosymmetric orthorhombic phase (Pca21) of Hf/Zr oxides [1] has brought enormous research interests and activities because the material compatibility with CMOS process and its scalability to a few nm thickness, which have been critical issues for introducing perovskites ferroelectric (FE) materials in nanoscale devices. Physical concept of “negative capacitance” in FE materials when stacked with dielectrics (DE) has been proposed to enhance the total capacitance larger than that of DE only [2,3] and has been demonstrated in DE-FE stacks such as Al2O3/Hf0.5Zr0.5O2 or Ta2O5/Hf0.5Zr0.5O2 via transient measurement [4,5]. However, stacks with amorphous Al2O3 DE layer having relatively low dielectric constant were vulnerable to irreversible charge injection from electrodes into the DE-FE interface and thus hysteresis-free operation of the capacitor was only limited to short pulse condition below 1μs. Also Ta2O5 DE layer is often found to be defective and the film easily becomes leaky with repeated cycles.
Here we propose novel DE-FE stack based on all crystallized Hf/Zr oxides where polymorphic Hf/Zr oxides have three dominant phases, monoclinic (P21/c), orthorhombic (Pca21), and tetragonal (P42/nmc) and by varying parameters such as Zr composition and thickness in initial amorphous film, the oxides can be crystallized in phase-selective way. We employ the tetragonal phase of Hf/Zr oxide for DE layer which possesses high-k value above 30 and wide bandgap about 5.4 eV ensuring low leakage current and further enabling thickness scaling. All crystallized DE-FE stacks were fabricated on bottom electrodes via atomic layer deposition of Hf/Zr oxides with compositional variation and subsequent metal deposition and post-metallization-annealing. Electrical data from capacitance vs. voltage and polarization vs. voltage measurements manifests an intermediate characteristic between ferroelectric and anti-ferroelectric ones due to multi-phase layers. Pulsed voltage measurements and structural analyses with XRD and selective area electron diffraction will be presented to assess the proposed stack for devices with enhanced capacitance.
References
[1] T. S. Boske, J.Muller, D. Brauhaus, U. Schroder, and U. Bottger, Applied Physics Letters
99, 102903 (2011).
[2] S. Salahuddin, and S. Datta, Nano Letters
8, 2, 405-410 (2008).
[3] H. W. Park, J. Roh, Y. B. Lee, and C. S. Hwang, Advanced Materials
31, 32, 1805266 (2019).
[4] K. D. Kim, Y. J. Kim, M. H. Park, H. W. Park, Y. J. Kwon, Y. B. Lee, H. J. Kim, T. Moon, Y. H. Lee, S. D. Hyun, B. S. Kim, and C. S. Hwang, Advanced Functional Materials
29, 17, 1808228 (2019).
[5] M. Hoffmann, F. P. G. Fengler, M. Herzig, T. Mittmann, B. Max, U. Schroeder, R. Negrea, P. Lucian, S. Slesazeck, and T. Micholajick, Nature
565, 464-467 (2019).

Figure 1
Effect of Etching Temperature on the Surface Texturing of Si{100} in an Extremely Low Concentration Tmah for Minimized Reflectivity
Authors: Gupta Arti , Pal Prem , Sharma Chandra Shekhar 
Published: May 2020

Among various renewable energy resources, solar energy is one of the most abundant energy available in nature. The solar energy can be utilized by converting photon energy into electrical energy by using solar cells as energy harvesters. Silicon-based solar cells dominate the current photovoltaic market because of its higher efficiency, excellent stability, non-toxicity, lower processing cost and excellent reliability in the outdoor conditions.1 However, the silicon solar cell efficiency can be further increased by reducing the front surface reflection from silicon, which is greater than 35%. In order to reduce the reflection from silicon surface, surface texturing is done where silicon surface is intentionally made rough. Wet anisotropic etching is most widely used in surface texturing of silicon because of its high throughput and lower cost. Potassium hydroxide (KOH) and tetramethylammonium hydroxide (TMAH) are two most extensively used alkaline solution for surface texturing of silicon. 2-4 In these two etchants, TMAH is preferred because it is fully compatible with CMOS process and also provide high etch selectivity between silicon and silicon dioxide. Surface texturing using low concentration TMAH (<5%) results in high surface roughness. This is a remarkable observation that can be applied in solar cell industries to minimize the reflection from silicon front surface.
In this work, we have studied the effect of very low concentration TMAH (1.0-0.1 wt%) without adding any additive and agitation during etching for surface texturing of Si{100} surface. The main objective of this study is to achieve an optimized etched surface topography at lowest possible etching concentration and etching time to minimize the reflectance for application in solar cells. The average solar weighted reflectance (Rsw) of around 10% is obtained in a very mild etching conditions. Compared to the previous results reported in literatures and also the mild etching conditions, reflectance values obtained in this work are quite promising for large area surface texturing of silicon solar cell panels for enhancement in their efficiency. In addition, the use of very low concentration TMAH minimizes the chemical waste. This also helps in adopting the technique for fabricating anti-reflective silicon surfaces at large scale.

References:

1. C. S. Solanki, Solar photovoltaics: fundamentals, technologies and applications, p. 16, PHI Learning Pvt. Ltd., (2015).
2. P. Papet, O. Nichiporuk, A. Kaminski, Y. Rozier, J. Kraiem, J.F. Lelievre, A. Chaumartin, A. Fave, and M. Lemiti, Sol. Energy Mater. Sol. Cells, 90, 2319–2328 (2006).
3. P. Pal and K. Sato, Silicon Wet Bulk Micromachining for MEMS, p. 24, Jenny Standford Publishing, New York, (2017).
4. P. Pal, K. Sato, M. A. Gosalvez, and M. Shikida, J. Micromechanics Microengineering, 17, 2299–2307 (2007).
(Invited) A Brief Overview and Future Outlook on the Progress of III-Nitride Semiconductors Research
Authors: Freitas Jaime A. 
Published: May 2020

The increasing need for devices capable of performing under extreme condition of power and temperature, and opto-electronic devices operating in the UV-Vis spectral range has been the principal driving force for research interest in III-Nitrides semiconductors over the last three decades. Progress in bulk growth and film deposition techniques for homo- and hetero-epitaxial growth of III-Nitride semiconductors has led to successful fabrication and commercialization of an increasing number of devices that are revolutionizing both the optoelectronic and electronic device industries.
Many relevant figures of merit related to electronic device performance scale superlinearly with the band gap; hence, ultra-wide band gap (UWBG) materials (Eg > 3.4 eV) have the potential for far superior performance than conventional WBG materials such as GaN and SiC. UWBG materials will be critical enablers of future electronic components and systems, and a fundamental understanding of their synthesis and properties is critical to exploiting their advantages. In particular, cubic boron nitride (c-BN), among the semiconductor materials in the UWBG group (c-BN, AlN, Ga2O3, and diamond), with a band gap of ~6 eV and thermal conductivity of 13 W/mK (second only to diamond, 20 W/mK) offers the best combination of breakdown voltage and specific on-resistance. Another advantage of c-BN over other UWBG semiconductors is that it can be doped with donors and acceptors, enabling the fabrication of bipolar devices.
The development of high quality GaN substrates and device grade films will be reviewed and a brief overview of the intrinsic properties of the WBG and UWBG semiconductors will be presented.
Demonstration of EDL Modulated FET Biosensors with Impedance Analysis
Authors: Wu Chang-Run , Wang Shin-Li , Chen Po-Hsuan , Chen Jung-Chih , Wang Yu-Lin 
Published: May 2020

The Electric double layer (EDL) gated FET biosensor has been applied to detecting the different biomarkers such as mi-RNA, protein, cell, and heavy metal ion and get successful results. In the past, we made efforts in research on how to develop portable FET biosensors. In this research, the mechanism of antibody-based FET biosensor is deeply investigated. The enhanced EDL is applied to improve the sensitivity of antibody-based FET biosensor and detect protein in high ionic concentration such as physiological salt concentration directly.
The sensor response is obtained by directly detecting the different concentrations of C-reactive protein (CRP) in physiological salt concentration. The absolute drain current from our device is analyzed and converted to potential drop in solution by giving different gate voltages during measurement. Furthermore, the total impedance on our sensor chip is also obtained by Agilent B1530/B1500A. Combining with FET sensor electrical signals and total impedance analysis, the sensor performance at different gate bias can be characterized.
The result shows sensor response is higher when the higher gate bias is applied to our device. This implies that the high charge density enhances the EDL, causing the higher signal. Furthermore, according to impedance analysis, the total impedance change causing by antibody-antigen interaction is dominated by the imaginary part which proves that our sensor sensing mechanism comes from the capacitive effect. The sensor performance is also analyzed by detecting protein in different salt concentrations. With increasing salt concentration, the total change of potential drop increases. Again, the higher salt concentration enhances the EDL.
In conclusion, the mechanism of EDL-modulated FET biosensor is investigated in this study. The unique EDL-modulated FET biosensor not only overcome the charge screening effects in high ionic concentration but also improve the sensitivity by increasing salt concentration. And we can also operate at different gate bias to optimize the drain current signal. Moreover, the impedance analysis shows the dominance of the imaginary part which can prove the sensor response is from the capacitance effect.

Figure 1
Pore-Scale Performance Analysis of Ordered Microstructures As Gas Diffusion Layers in Fuel Cells
Authors: Niblett Daniel , J. Niasar Vahid , Mularczyk Adrian , Eller Jens , Holmes Stuart 
Published: May 2020

Emerging from the advances in both manufacturing and computational modelling techniques, it is possible to investigate the performance of an ordered microstructure manufactured by high resolution additive manufacturing processes. In a previous study, we have investigated the direct simulation of effective transport properties [1] and within this work, two-phase flow dynamics coupled with the appropriate boundary conditions present in an operating fuel cell (microporous layer defects and gas channel coupling) on an idealised carbon paper and ordered lattice microstructures.
OpenFOAM was used to simulate two-phase flow in the void space of both the porous structures and gas channels coupled with the Volume of Fluid (VoF) method in 2D and 3D simulations. The effective electrical conductivity and permeability was determined for each structure for comparison. To more accurately envisage the replacement of traditional materials with the new conceptual material, more accurate boundary conditions were investigated, including injection from an imposed micro-porous layer defect which was extracted from an SEM image shown in Figure 1. Additionally, coupling the dynamic effects of the gas channel on the fluids within the porous domains allowed for additional insight to the stability of the two-phase flow.
Pore-scale simulations illustrate that only certain ordered structures will promote beneficial two-phase flow in fuel cells in terms of reducing the amount of flooding and oxygen diffusional resistance. Alternatively, it has been shown that the ordered microstructures improve both electrical conductivity and permeability if they can be made from the same carbon material. The ordering of structures to be used as new micro and nano materials is a new area of investigation, which would provide further evidence of performance improvements due to structures.
Furthermore, the dynamic two-phase flow effects on local clusters of water have been investigated and analyses to show how both the gas channels supplying oxygen and microporous layer defects can significantly affect the fluid dynamics including; droplet growth, detachment and transport within the gas channels. This work and its findings was validated by the comparison of the VoF method to mCT data for water injection through a standard GDL and with growth and detachment in the channel. The results showed good agreement between the interface dynamics, location and shape.
[1] D. Niblett, V. Joekar-Niasar, and S. Holmes, “Optimisation of Fuel Cell Gas Diffusion Layers using Ordered Microstructural Design,” Journal of The Electrochemical Society, vol. 167, no. 7, p. 013520, 2018.
Figure 1 - Simulation of water injection into reconstructed ordered and carbon paper microstructures to evaluate the performance of the materials in management of water.

Figure 1
Segmenting Water Observed with X-Ray Computed Tomography in Gas Diffusion Layers of Polymer Electrolyte Fuel Cells Using Convolutional Neural Networks
Authors: Shum Andrew , Parkinson Dilworth Y. , Zenyuk Iryna V. 
Published: May 2020

Gas diffusion layers (GDLs) are responsible for oxygen delivery to the catalyst layer and water management in polymer electrolyte fuel cells (PEFCs). With x-ray computed tomography (CT) – a non-destructive technique, one can observe water transport through the GDL, and also assess local wettability. With ability of X-ray CT to capture dynamics of water transport the quantity of data and the time required to process the data increases. There is a need to further automate data processing and analysis through machine learning; in particular, convolutional neural networks (CNNs). CNNs can be applied to a multitude of image processing tasks such as finding centers of rotation for CT data [1], removal of reconstruction artifacts [1], and denoising of data sets [2]. However, CNNs are probably most known for their ability to perform segmentation/labeling.
Although CNNs have proven to be widely applicable to image processing and analysis, it has also become apparent that individual pairings of architecture and application must be validated [1]. As such, we focus on the use of CNNs to segment synchrotron X-ray CT data sets for water within various GDLs. The water is tracked for an in-situ evaporation/condensation experiment. Knowledge of the water's location and shape as a function of time is necessary to understand local GDL’s wettability and its effect on PEFC performance. The challenge these samples present to more traditional segmentation methods is the low contrast between water and carbon fibers. Depending on the composition of a GDL, binder, polytetrafluoroethylene (PTFE), and the microporous layer (MPL) may also be present in the same narrow window of gray-scale values. Separating these phases is essential in evaluating the material's water transport properties. We will present results from both our efforts with CNNs and the specific PEFC experiment that produced the data sets.

References:

1. Yang, X.; DeCarlo, F.; Phatak, C.; Gursoy, D. A Convolutional Neural Network Approach to Calibrating the Rotation Axis for X-ray Computed Tomography. J. Synchrotron Radiat. 2017, 24, 469-475, DOI: 10.1107/s1600577516020117.
2. Pelt, D.M.; Sethian, J.A. A Mixed-Scale Dense Convolutional Neural Network for Image Analysis. Proc. Natl. Acad. Sci. U. S. A., Early Ed. 2018, 115 (2), 254-259, DOI: 10.1073/pnas.1715832114.
Preparation of Unique Flower-like Pt-Ni Alloy Catalysts As the Cathode of a PEMFC By Electrodeposition Technique
Authors: Huang Jen-Hui , Yeh Tsung-Kuang , Wang Mei-Ya 
Published: May 2020

The hydrogen economy can play an important role in the low-carbon economy, and fuel cells technology is an essential part of the hydrogen economy. The proton exchange membrane fuel cell (PEMFC) is one kind of electrochemical reaction device with the advantages of low temperature operation, high conversion efficiency and noiseless, which is expected to widely utilizes in public transportations.
The oxygen reduction reaction (ORR) at the cathode is the rate-determining step in a PEMFC. To enhance the ORR efficiency at the cathode, the unique flower-like platinum-nickel binary alloy catalysts were deposited on the carbon cloth by potentiostatic electrodeposition, effectively improve the oxygen absorption and desorption paths on the surface. The Pt-Ni binary alloy catalysts with the shorter lattice spacings and the effect of high-index facets would increase the electrochemical surface areas (ECSAs) of the catalyst and power density. The samples with the pure platinum and commercial Pt catalyst were also prepared as comparison.
Morphology, particle size, chemical bonding, and elemental composition were characterized by SEM, TEM, XRD, XPS and ICP-MS. In addition, the electrochemical characteristics of the Pt-Ni catalysts were investigated via cyclic voltammetry (CV) and linear sweep voltammetry (LSV) analysis in 0.1 M perchloric acid solution. In single cell test, the peak power density of PEMFC with Pt-Ni cathode was 700 mW/cm2
.