bluuebunny/crossref_metadata_2025_split huggingface dataset:
Synthesis and Electrical Properties of ALD Deposited TiO2-Based Memristor Structures
Authors: Zhang Kai , Lin Pengtao , Pradhan Aswini K , Baumgart Helmut 
Published: February 2020

Memristor devices have been rapidly emerging as a promising candidate in the field of non-volatile memory devices. There are a wide range of applications such as non-volatile random access memory, dynamic random access memory, image processing, flash memory, neural networks, and artificial intelligence. In recent years, many new materials for memristors have been investigated including metal-oxides due to their potential for high-density integration, high endurance, fast switching behavior, low power consumption and simple structure. Among the promising binary transition metal oxide materials, such as nickel oxide, zirconium oxide, zinc oxide, hafnium oxide, and Ta2O5, TiO2 films are extensively used to fabricate nonvolatile memristor devices due to its simple structure and compatibility with CMOS integration processes. Recently, ZnO has been widely used for various applications due to its good electrical conductivity, wide band gape (3.37 eV), high exciton binding energy (~60 meV), low cost, nontoxicity, high mechanical and thermal stability. When doped with Aluminum ZnO grown via atomic layer deposition (ALD) has been reported to show resistivity values ranging from insulating to on the order of 10−3 Ω·cm, which is suitable for memory device electrodes.
Many methods are available for synthesis of thin films such as magnetron sputtering, pulsed laser deposition, thermal oxidation, electrodeposition, chemical vapor deposition, sol gel chemical reaction, and atomic layer deposition. ALD technique is considered promising for potential application in the preparation of memristors based on active TiO2 layers. The ALD is a self-limiting technique that allows one atomic layer growth for each growth cycle. ALD can precisely control the film layer thickness, stoichiometry, composition, uniformity, and sharp interfaces. ALD also shows perfect conformal coverage when it deposits thin film on complex surface structures. Therefore, ALD is considered as a novel and competitive method to deposit MIM memory structures. To create such MIM devices, first a transparent Al:ZnO film was grown on a Si wafer as a transparent bottom electrode followed by an active layer of TiO2 film. Then the top contact layer consisting of Al:ZnO was deposited in-situ on the TiO2 layer to complete the memristor structure. All the thin films in the memristor structure were synthesized sequentially by ALD technology.
Several physical characterization techniques have been utilized to analyze the ALD TiO2 thin films of memory devices. The crystal structure was determined by X-ray diffraction (XRD). The film morphology was studied by field emission scanning electron microscopy (FE-SEM). The surface roughness was measured by atomic force microscopy (AFM). The electric properties were tested by a semiconductor parametric analyzer. The results demonstrate promising memristive properties of synthesized ALD TiO2-Based Memristors sandwhiched between Al:ZnO electrical contacts.
(Invited) 3D Passive Devices and Through-Substrate Connections for Medical and Automotive Applications
Authors: Bunel Catherine , Lefeuvre E , Jacqueline S , Jatlaoui M 
Published: February 2020

Murata has developed a unique technology in silicon for capacitors and interposers with integrated passive devices .The research was focused on advanced concepts with 3D trenches with extremely high aspect ratio and exquisite high K dielectrics to get to the highest capacitor density with excessive reliability. The technology is compliant with strong capability in terms of packaging enabling outstanding performances of miniaturized products and heterogeneous solutions.
This paper outlines two stacking technologies: one in medical where the performance and form factor parameter are becoming more and more important and the other one is in automotive where higher computing performance will be entailed. Both are subject to demanding requirements in terms of reliability.
The 3D integration schemes, one that doesn’t rely on traditional methods of interconnect and the other with Through Silicon Via (TSV), will be depicted in addition to the manufacturing processes.
Using Reduce Graphene Oxide (rGO) As a Conducting Layer for a PCB Metallization
Authors: Chang I-Hsuan , Dow Wei-Ping 
Published: February 2020

Electroless (ELS) copper plating process has been commonly used for PCB metallization. However, the ELS copper process is not environment-friendly because it contains precious metal (i.e., Pd catalyst), formaldehyde and chelating agents. Also, ELS copper plating process gives rise to several problems on the metallization of through holes (THs) and microvias.
In this work, ELS copper deposition process was replaced by a reduced graphene oxide (rGO) process to form a conducting layer on the sidewalls of THs and microvias of a PCB for subsequent copper electroplating. rGO has an excellent conductivity and metal barrier capability. Also, the rGO process has more advantages such as environment-friendly, short process steps, no toxic chemicals and organic solvent. A high copper throwing power (> 90 %) in the THs with a high aspect ratio can be obtained using rGO as a conducting layer, even better than ELS copper plating. Moreover, the rGO process could result in good copper filling performance in the microvias without seam or void in the via center. After thermal reliability test, the rGO grafted on the sidewall of the through holes and microvias could pass critical thermal reliability criterion due to its excellent thermal stability. Therefore, brand-new and promising rGO process is hopeful to play a significant role in the future PCB fabrication.
Study on Electromigration of Nano-Silver Paste with Different Hot Pressing Sintering Conditions
Authors: Chen In Gann , Yang Chia Ming , Chio Yan Ruei , Hsu Lien Chung , Hsieh Po Tsung 
Published: February 2020

Silver is suitable for use as a interconnect material due to its good thermal conductivity and electrical conductivity. Additionally, nano-sized silver particles (or pastes) can be rapidly sintered at related low temperatures (<250°C ) due to their high surface to volume ratio. The nano-sized silver particle paste developed in this study can be hot-pressed at 250°C and 10 Mpa to form a low porosity (6.2%) and low-resistivity (2.9*10-8 Ω-m) interconnect, which is comparable to that of commercial available products.
With the demand for higher packing density of integrated circuit, the interconnect line width decreases and the current density increases. In general, if the current density is increased to higher than 105 A/cm2, electro-migration phenomenon would become more serious and could cause unpredictable failure of interconnect. In order to understand the electro-migration mechanism of silver interconnect made by nano-paste followed by hot pressing sintering, the porosity of samples with different hot-pressing parameters was measured. Subsequently, current-stressing tests (at 250°C and 105 A/cm2 ) of interconnects were carried out. Through observations of changes in the surface morphology and cross-sectional microstructures during current-stressing tests, the failure mechanism and electro-migration phenomenon are investigated in detail. It is observed as shown in the figure that the electro-migration occurred in early stage (within about 1 day) that resulted in the decrease of porosity near cathode and increase of porosity near anode respectively.
Figure 1

Figure 1
Electrical Double Layer Gated Field Effect Transistor Biosensors for the Quantitative Detection of Beta-Human Chorionic Gonadotropin
Authors: Smith B , Liao Liang-Wen , Chen Po-Hsuan , Wang Yu-Lin 
Published: February 2020

In this research, we have developed biosensors to detect beta human chorionic gonadotropin (beta-HCG) which is a hormone widely used to test for pregnancy and also serves as a biomarker for risk assessment of certain types of cancers. The biosensor methodology is based on extended gate design of electrical double layer (EDL) gated field effect transistor (FET). In this study, we fabricated a sensor array chip and functionalized the gold electrode surface with antibodies to capture the antigen, beta-HCG. Each sensor in the sensor array chip consists of two gold electrodes, one connected to the gate voltage supply and the other connected to the gate terminal of the FET, which is located on isolated PCB such that the test solution does not directly contact the transistor active region. A hand-held sensor measurement unit is fabricated which can apply the biasing voltages, measurement the resulting drain current signal and display the output results in LCD monitor.
Fluorescence measurement technique is used to confirm and analyze the surface functionalization with antibodies to beta-HCG. The relation between beta-HCG antigen concentration and electrical signal is established by testing the sensor array chips using the hand-held device. The test samples are prepared by diluting purified stock proteins in 1X PBS, as it simulates the physiological conditions of human urine. Using our FET biosensor, we can directly detect beta-HCG in high ionic strength media like 1X PBS, without performing additional sample processing. Most pregnancy tests have a sensitivity of 25–50 IU/l (1.5-3 ng/ml), based on immunochromatography which is the most widely technique for detection of beta-HCG. Using our sensor methodology, we can obtain a sensor response curve with a dynamic range of antigen concentration between 0.03 to 30 ng/ml. As the antigen concentration approximately approaches 10 ng/ml, the current gain value is nearly saturated. The result shows that when beta-HCG antigen concentration increases, current gain value decreases. This sensing methodology can facilitate quantitative detection of beta-HCG in physiological conditions, whereas the current commercially available assays provide only qualitative test results. The sensor demonstrates a very wide dynamic range of detection, with a very low detection limit, which shows the potential of our sensor to detect pregnancies in very early stages. Furthermore, this sensor platform can enable the use of beta-HCG for risk stratification of cancers as well. The sensor can be batch produced and does not use additional labels/reagents or sample pre-processing techniques, which can greatly enhance the cost-effectiveness, comparable to the current commercialized beta-HCG assays.
Epitaxial Growth of Cu2O on Ag Substrate by Electrodeposition
Authors: Dai Dajin , Huang Pei-Yu , Chang Liuwen 
Published: February 2020

Cuprous oxide (Cu2O) is a p-type semiconductor with a direct bandgap of 2.1 eV and high hole mobility at ambient temperature. Recently, the importance of using an epitaxial film to fabricate optoelectronic devices to improve the performances has been pointed out [Mahenderkar et al., Science, 355, 1203–1206 (2017)]. Investigation of epitaxial growth of Cu2O on, mostly, MgO substrate by molecular beam epitaxy or pulsed laser deposition has been carried out for a decade. However, these techniques require high-quality substrates and expensive facilities. Electrodeposition, on the other hand, provides another option with ease of operation. However, the substrate has to be electrically conductive and possesses a low lattice mismatch to Cu2O.
In this study, the epitaxial growth of Cu2O on Ag substrate by electrodeposition was studied by a combinatorial substrate approach mainly using the electron backscatter diffraction (EBSD) technique. The effect of substrate orientation on epitaxial growth can thus be explored efficiently. The lattice mismatch between Ag and Cu2O is 4.3 %. Prior to the deposition, the annealed, polycrystalline Ag substrate was electropolished and analyzed by EBSD over a marked region of about 500 x 500 μm2. Atomic force microscopy was used to characterize the surface morphology of the substrate grains of different orientations. Afterwards, Cu2O films were deposited galvanostatically on the substrates in an electrolyte containing copper sulfate and lactic acid. The crystal structure and orientation of the marked area was analyzed by EBSD again after electrodeposition. The orientation distribution of the films and the orientation relationship between the overlaid Cu2O and the Ag substrate were thus obtained. X-ray diffraction was also used for phase identification. Results indicated that the substrate grains exhibited similar surface roughness values of approximately 3 nm regardless the orientation. X-ray diffraction reults confirmed that the films deposited at different conditions contained solely the Cu2O phase. No diffraction peaks of Cu and CuO were found. At a low current density of 0.06 mA/cm2, the film has a rough surface composing of faceted islands of 5-20 mm in size. A portion of the islands exhibited the same orientation as the substrate grain. On the other hand, at a high current density of 0.25 mA/cm2, films with smooth surfaces were obtained. The Cu2O films all grew epitaxially on the Ag grains in two orientation relationships: a cube-on-cube one and a <100>/45o one. The origin of the <100>/45o orientation relationship was further studied and will be explained in detail. The deposited films were also analyzed by photoluminescence at room temperature and showed strong near band-edge emissions at 1.97-2.06 eV.
Electroanalytical Characterization of Electrochemical Capacitor Systems
Authors: Mavroudis Helena , Forghani Marveh , Donne Scott W 
Published: February 2020

This study aims to investigate the behaviour of the electrode materials during charging and discharging processes using an indicator electrode. Generally, the capacitive behaviour of the electrochemical capacitors is associated with the electrical double layer at the surface of the electrode, and in some materials pseudo-capacitance, which results from redox processes. More importantly, it is possible that some oxidized or reduced species which are soluble in electrolyte diffuse or migrate from one electrode to another electrode. Hence, an indicator electrode can detect these ions movement during the charging and discharging processes.
In this study, each electrochemical cell has been made of two symmetrical activated carbon (AC) electrodes with the same mass of active material on each electrode. The AC electrochemical cells have been tested in the non-aqueous electrolyte (1 M TEABF4) and aqueous electrolyte (0.5 M K2SO4) using cycling voltammetry (CV) at 25 mV/s sweep rate between 0 and 2.3 V and 0 to 2 V respectively. It was followed by the step potential electrochemical spectroscopy (SPECS) experiment with a 10 mV potential step and 30 s of equilibration time. The SPECS method is based on applying a series of equal magnitude potential steps on a working electrode, with sufficient rest time to allow for equilibrium to be established for each step throughout an applied potential window. This slow scan rate allows the separation of the charge storage mechanisms, such as electrical double layer and diffusion-limited processes [1]. At the same time, the open circuit potential (OCP) of both electrodes have been measured with respect to the Ag/AgNO3 reference electrode during the CV and SPECS experiments. This technique allows one to see how an individual electrode behaves in the overall cell performance.
Moreover, the electroanalytical characterisation of the AC electrochemical cell has been investigated using the indicator electrode. In this method, the platinum mesh was located in the middle of the two separated papers between two electrodes and the Pt mesh potential was clamped at -± 0.5 V with respect to the Ag/AgNO3 reference electrode during the CV and SPECS experiments. This new technique enables one to detect the migration of oxidised or reduced species from each of the electrodes during charging/discharging processes. In an ideal capacitor, this indicator electrode should have zero current; however, it has been observed that the indicator current changes at both positive and negative potentials during charge storage mechanism. This indicates the emitting and migration of redox species between the two electrodes. Also, it can be seen that there are different effects of aqueous and non-aqueous electrolyte on the behaviour of the redox migration.

Reference: [1]. Marveh Forghani and Scott W. Donne, Journal of the Electrochemical Society 2018 165: A664-A673.
Supercapacitors from Waste: Converting Pulp and Paper Mill Waste to Nitrogen Doped Supercapacitors
Authors: Latham Kenneth G 
Published: February 2020

The conversion of waste into energy storage materials has become an important topic in the field of sustainability. The challenge being that new materials from waste should perform better than those that are currently available, be cost effective, environmental friendly and scalable. The was streams from pulp and paper mills make an ideal candidate for upgrading, as they contain a wide range of biomaterials that have the potential to be converted into carbon materials for supercapacitors. The challenge with these waste streams is that they are wet and contain a range of inorganic materials.
To overcome this, hydrothermal carbonization was utilized to convert the waste streams into carbonaceous materials. Hydrothermal carbonization is a wet, low temperature, thermochemical carbonization technique that excels in converting wet biomass into carbon products that can be easily activated an converted into carbon electrodes for supercapacitors. Additionally, the carbon materials can be doped with nitrogen, phosphorus, boron and sulfur by simply adding the dopant to the raw material prior to carbonization. Doped carbon materials have displayed improved performance and stability over their non-doped counterparts, as the dopants provide additional charge storage sites, increasing capacitance.
In this work we have examined the potential to upgrade black liquor, an inexpensive by product of the pulping process, via hydrothermal carbonization for supercapacitors. These materials have been doped with a range of readily available nitrogen sources (NH4Cl, melamine, urea) to increase the stability and capacitance of the electrode. Additionally, a range of activation agents (KOH, K2CO3, KHCO3 and melamine) were investigated to improve the capacitance and stability. The electrodes were tested in aqueous electrolytes, 4M KOH and 0.5M Na2SO4, with stable voltage windows of 1.1V and 1.8V, respectively.
To examine the capacitance and cycle stability, cyclic voltametry and galvanostatic charge-discharge measurements were employed, finding that most materials had a capacitance <190 Fg-1 at 25 mV s-1. The electrochemical variations between the materials were further examined by Step Potential Electrochemical Spectroscopy, which allowed the decoupling of double layer and pseudocapacitance contributions. These were combined with in-depth X-ray Photoelecton Spectroscopy of the surface to draw correlations between pseudocapacitane from the carbon-oxygen/carbon-nitrogen functional groups and capacitance contributions from the double layer.
Design of Machine-Washable and Wearable Supercapacitors Using Composite Laminates
Authors: Anjum Nasim , Shen Caiwei 
Published: February 2020

Flexible and wearable supercapacitors, as a rechargeable energy storage device, are promising power sources for next-generation wearable electronics and electronic textiles in many consumer, medical, and military applications, as they offer safety, mechanical flexibility, stability, and durability that are lacking in current batteries. However, flexible supercapacitor prototypes reported so far have not demonstrated sufficient mechanical properties that could withstand critical situations, such as folding, twisting, and machine washing, which are commonly happening for real-world applications.
Here we present the design of flexible supercapacitors that are foldable, twistable, and machine-washable due to exceptional mechanical properties of the materials. The devices are constructed using thin composite laminates as electrodes and ion-conducting separators. Each layer of the laminates is composed of randomly distributed activated carbon fibers or glass fibers in polymer electrolyte matrix. Calculations and simulations show that such laminates with proper fiber length and volume fraction of fibers can provide both high strength and high flexibility that enable them to survive critical mechanical deformations, while traditional particle-based electrodes cannot.
The electrochemical and mechanical tests demonstrate that the activation of the carbon fiber surface does not affect much of the mechanical properties of the laminates, but greatly improves the surface area of electrodes, which leads to two orders increase in their electrical double-layer capacitance. The prototypes made of electrode/separator/electrode laminates show adjustable areal capacitances of over 10 mF/cm2. The electrochemical performance has remained unchanged after repeated folding and twisting tests. Moreover, we sewed the devices onto fabrics and washed them together with daily garments in a washing machine, after which we observed no mechanical damage or capacitance degradation.
In conclusion, we believe that the excellent electrochemical performance, flexibility and mechanical durability make the composite laminates-based flexible supercapacitors promising to be integrated with daily garments to power various wearable electronics. The design rules and results are also applicable to developing other flexible functional devices that require extraordinary mechanical properties without sacrificing another function.
Investigation of the Fe / W / O System for Aqueous Electrochemical Capacitor Electrode Materials
Authors: Crosnier Olivier , Goubard Nicolas , Espinosa Angeles Julio Cesar , Douard Camille , Favier Frederic , Brousse Thierry 
Published: February 2020

Electrochemical capacitors fill the gap between high energy and high power storage devices. Within this matter EDLCs (Electric Double Layer Capacitors, which store charge electrostatically, are the most studied using carbon based materials. They present excellent performance concerning specific capacitance and cyclability, capable to undergo up to one million of cycles [1]. These materials present a low density, due to the activated carbon, making them unsuitable for applications where a high volumetric capacitance is required. For this special scope alluring high-density polycationic oxides exhibit a reliable advantage over the normal carbon based materials [2].
In this work, several materials of the Fe / W / O system have been investigated. Amongst them, two iron tungstate oxides (FeWO4 and Fe2WO6) are of peculiar interest. They were successfully synthesized by several techniques, such as ceramic, hydrothermal and polyol-mediated routes [3]. The materials obtained underwent different heat treatments in order to acquire a crystalline structure. Afterwards, the different samples were characterized by X-ray diffraction, Scanning Electron Microscopy, Energy dispersive X-ray spectroscopy, Mössbauer Spectroscopy and surface area measurements, BET. The materials were assembled in a composite electrode to be studied in a three electrode set up in aqueous LiNO3 5M by cyclic voltammetry.
The results showed a compromise between the specific surface area, the particle size, morphology, and crystallization, as well as the mean Fe oxidation state that have a direct impact in the electrochemical performance.

References

[1] P. Simon and Y. Gogotsi, Nature Mater., 2008, 7, 845–854.
[2] O. Crosnier et. al., Curr. Opin. Electrochem., 2018, 9, 87–94.
[3] N. Goubard-Bretesché et. al., Electrochem. Comm., 2015, 57, 61–64.