bluuebunny/crossref_metadata_2025 huggingface dataset:
The Crystallinity Effect of Manganese Dioxide for Durability of Rechargeable Zn-Air Battery
Authors: Zheng Xiaoying , Moreno Zuria Alonso , Abrego Martinez Juan Carlos , Mohammadi Naser , Mohamedi Mohamed
Published: May 2020

Zn-air battery is of great interest in rechargeable batteries due to its low cost, environment-friendly and theoretically high energy density which is about 1086 Wh kg-1 [1]. The activity and durability of cathode are the bottleneck of the battery performance, which attribute to the sluggish kinetics of the oxygen reduction reaction (ORR) during discharging and oxygen evolution reaction (OER) during charging. Manganese dioxide (MnO2), an abundant and valence-varied transitional metal oxide, has great potential as bifunctional air-cathode catalyst in Zn-air battery. Despite extensive research efforts have been devoted to MnO2 for Zn-air battery, few disclose the relationship between crystallinity and battery durability. Herein, we present the synthesis and characterization of MnO2 samples prepared in a simple beaker (BK) and samples synthesized via the hydrothermal method (HT). The ORR studies revealed respectively for BK-sample and HT-sample an electron number of 3.67-3.95 and 3.68-3.84 in the potential range of 0.4-0.8 V. Afterwards, the samples were evaluated for their performance in a homemade Zn-Air battery. The sample BK delivered a peak power density (42.8 mW cm-2 at an applied current density of 71.0 mA cm-2) on a par with the sample HT (41.6 mW cm-2 at 68.2 mA cm-2). Interestingly, even though both of the sample showed similar discharge and charge voltage during the initial few cycles, the as-prepared sample HT showed more stable cycling performance after long-term discharge-charge cycling, especially for the charging process. After 120th cycle at current density of 2 mA cm-2, the voltage gap of sample HT (1.12 V) is much lower than that of sample BK (1.32 V). The electrochemical impedance spectra (EIS) recorded before and after the cycling measurement exhibited comparable charge transfer resistance for the two as-prepared samples whereas smaller charge transfer resistance of sample HT after the cycle test. The superior cycling durability in sample HT might be ascribed to the better crystallinity of MnO2 and less trend in collapse from the aspect of structure.

References

[1] Y. Li, H. Dai, Chemical Society Reviews, 43 (2014) 5257-5275.
Deterioration of Mechanical Properties Steel Plate Due to Corrosion Phenomena-the Statistical Surveys of Full-Scale Ship and Electrochemical Model-Based Establishment
Authors: Hsu I-Jen , Lu Yi-Sheng , Lee Yueh-Lien
Published: May 2020

The mechanical properties of the corroded steel plates are important in analyzing the remaining capacity of ship structures. However, the data is scarce and most of that came from the simulated test with physical processing. In this study, the mechanical properties of the corroded steel plate from the real ship were investigated. Moreover, the mechanical properties declines model was constructed by conducting the tensile testing on the localized corroded and general corroded steel plate which were created by using the impressed-current method and corrected by the data from the real ships. The preliminary results showed that the young’s modulus, yielding strength, tensile strength and extension rate remains constant on the general corroded steel plates which have a reduced thickness from 5% to 35%. In localized corrosion, however, the extension rate decreases rapidly in prophase, and then the tensile strength decreases and the yielding plateau disappears. Also, the Scanning Electron Microscope (SEM) and X-ray diffraction (XRD) results revealed that the microstructures of the corroded steel plate from the real ship and simulated experiment are all same as the new plate, proving that the alternations of mechanical properties are the result from the corrosion-induced stress concentration.
Corrosion Behavior of Phase Fraction in High Strength Steel Under Corrosion Acceleration Test
Authors: Song Yonkyun
Published: May 2020

High strength steel has been developed to meet the needs of weight reduction in automotive industry. To get high strength (tensile strength over tan 780 mega pascal), phase transformation and complex phases (ferrite, martensite) has been employed in steel alloy design with addition harden ability element such as silicon and manganese. The electrochemical and corrosion behavior of high strength steel is different from the general mild steel. Complex phase steel shows a good general corrosion resistance property but a poor perforation corrosion. The interfaces of phases(Ferrite-Martensite) plays a role of corrosion initiation site. The corrosion product of complex phases steel(high strength steel) accelerates perforation corrosion comparing general mild steel(single phase). The corrosion rate depending on the phase fraction (full ferrite, 20% Farrite, 50% Ferrite 80% Ferrite and full Martensite) was monitored under corrosion acceleration test for 40 days. The corrosion mechanism of complex phase steel will be discussed in this study.
Novel in-Situ Methods for Real-Time Monitoring of Corrosion
Authors: Virtanen Sannakaisa
Published: May 2020

The presentation will introduce recently developed new techniques that allow real-time monitoring of corrosion processes. The approach is based on simultaneous measurement of the cathodic kinetics of the H2 evolution reaction (HER) and the O2 reduction reaction (ORR) in real-time. The universal and non-destructive, in-situ methods based on monitoring the rates of the cathodic reactions enable the determination of sensitive, real-time corrosion rates for both atmospheric corrosion and immersion.

In the case of immersion, HER monitoring e.g. with gravimetric buoyancy H2 measurements is well established. Recently it was shown that gravimetric H2 measurements are also suitable to monitor atmospheric H2-type corrosion (for Mg alloys) [1]. A novel approach to measure HER rates during atmospheric exposure is introduced in this work. This is based on determining the pressure increase in a hermetically closed chamber with a pressure sensor. Regarding ORR, both volumetric measurements and pressure sensor based techniques are applicable to monitor the rate of consumption of O2 gas. In addition, a fibre optic O2 sensor can be employed to monitor ORR rates both under immersion and atmospheric corrosion conditions. A combination of these methods enables to monitor ORR and HER simultaneously. Therefore, also corrosion systems where both HER and ORR contribute to the cathodic reaction can be monitored (e.g., Fe and Zn corrosion). Examples for the different scenarios and approaches will be demonstrated. Comparing the total cathodic charge recorded by the new monitoring techniques with mass loss measurements shows an excellent correlation. Moreover, combining the above described approaches with a flow cell setup expands the possible corrosion scenarios to be investigated. The flow cell enables switching between exposure conditions (e.g., electrolyte composition, temperature, flow rate,...) with a real-time response of the corrosion rate.

The techniques presented on one hand are of interest for corrosion monitoring, but on the other side also reveal mechanistic information on corrosion reactions.

[1] M. Strebl, S. Virtanen, J. Electrochem. Soc., 166 (11), C3001-C3009 (2019).
Discussion on Inductive Loop Observed in Complex Plane Plot of Electrochemical Impedance of Mg
Authors: Itagaki Masayuki
Published: May 2020

Electrochemical impedance spectroscopy (EIS) is able to discriminate several time constants involved in electrode reactions. The time constant regarding adsorption-desorption relaxation may be detected in the plot of impedance spectrum when the adsorption at liquid/solid interface contributes to the kinetics of electrode reaction. For example, the complex plane plots of the electrochemical impedance of Pt electrode, where oxygen reduction occurs, show an apparent inductive loop, indicating the presence of the reaction intermediate adsorbed on the electrode1). The inductive loop is often observed in the cases of metal dissolutions in aqueous solutions2-4), and the origin has been explained by the adsorption of adsorbed intermediate in dissolution reaction. In this presentation, the author derives the theoretical equations of the Faraday impedance involving the contribution of adsorption process during metal dissolution. A current i, which flows across liquid/solid interface, is a function of electrode potential E and surficial coverage θ of adsorbed species as follows.

i = f(E, θ) (1)

The Faradaic impedance Z
F can be represented from the differential calculus of the equation (1), where, a
1 and a
1 are partial differential coefficients.

1/Z
F = di/dE = a
1 + a
2(dθ/dE) (2)

The equation (2) indicates that the Faradaic impedance is a function of (dθ/dE) and describes a semicircle due to an adsorption relaxation on the complex plane. In these cases, the semicircle in the low frequency range is related to the time constant of adsorption and desorption of the reaction intermediate. The conditions that the electrochemical impedance shows the inductive loop in the low frequency range are discussed on the basis of the numerical simulations.

References

1) M. Itagaki, H. Hasegawa, K. Watanabe, T. Hachiya, J. Electroanal Chem 557 (2003) 59.

2 M. Keddam, O. R. Mattos, H. Takenouti, J. Electrochem. Soc, 128 (1981) 257.

3) M. Itagaki, M. Tagaki, K. Watanabe, Electrochim.Acta, 41 (1996) 1201.

4) G. Baril, G. Galicia, C. Deslouis, N. Pebere, B. Tribollet, V. Vivier, J. Electrochem. Soc, 154 (2007) C108.
Investigation of AISI 316 Stainless Steel Corrosion in Perchloric Acid
Authors: Ostapenko Gennady I.
Published: May 2020

The synthesis of 4,4-dimethyl-1,3-dioxane for the production of isoprene in perchloric acid is carried out. The synthesis apparatus is made of AISI 316 stainless steel. Here, AISI 316 steel corrosion in pure perchloric acid and in the presence of benzotriazole as a corrosion inhibitor is investigated by the potentiodynamic method.

Figure 1 shows the polarization curves in 1 M perchloric acid at various concentrations of benzotriazole. It is seen that with an increase in the inhibitor concentration, the curves shift to the cathode side and the cathode currents decrease more strongly than the anode currents. Therefore, benzotriazole in perchloric acid is an cathodic action inhibitor.

The Tafel relation for the polarization curve can be represented as the equation (1) of a straight line, which is convenient for determining the corrosion currents icorr
. Polarization curves at various inhibitor concentrations are shown in Figure 2 in the coordinates of this equation. Here icorr
was defined as currents at (Е – Еcorr
) = 0.

Corrosion currents, corrosion rates and inhibition efficiencies for various concentrations of benzotriazole are given in the Table.

Figure 1
Wafer-Scale Fabrication of Solid-State on-Chip Microsupercapacitors Based on Silicon-Processing Techniques
Authors: Choi Christopher S , Taberna Pierre-Louis , Lethien Christophe , Simon Patrice , Dunn Bruce S.
Published: May 2020

Conventional silicon-based fabrication techniques, ranging from photolithography to various etching processes, are well-established approaches for achieving high-resolution patterns for microelectronics in the semiconductor industry. Although the use of microfabrication methods in the production of electrochemical energy storage (EES) devices has not really been considered, the adaption of these silicon processing techniques can open up new fabrication routes especially for integrated on-chip energy storage devices. One important consideration for the development of on-chip EES devices is to fabricate a mechanically rigid solid electrolyte with spatial and thickness control, which can be achieved using photopatterning functionality.1

This presentation will review our results on the synthesis and characterization of a photopatternable, ionically conducting solid electrolyte for on-chip micro-supercapacitors (MSC). Our approach was to create ‘quasi-solid’ electrolytes in which the photopatternable epoxy-based polymer matrix (SU-8) confines charge-carrying ions to provide measurable ionic conductivity. The resulting ion modified electrolyte is a promising gel polymer electrolyte with excellent thermal and physical properties and a room temperature ionic conductivity of 10-4 S cm-1. In addition, we demonstrate wafer-scale fabrication of all-photopatterned solid-state MSC devices. Electrochemical testing of tandem MSC devices validated that the potential range and total current output of MSC devices can easily be tailored through modifying the device arrangements in series or parallel configurations. The proposed fabrication strategy, based on magnetron sputtering of electrode materials in conjunction with a photopatternable solid electrolyte, provides a unique opportunity for the development of robust solid-state MSC that can be integrated with microelectronics in a single chip.

Reference

1. Choi, J. Lau, J. Hur, L. Smith, C. Wang, B. Dunn, Advanced Materials. 30 (2017) 1703772.
Dielectric Performance of Polymer Composites By Graphene Inclusion
Authors: Jun So-Yeon , Yu SeGi
Published: May 2020

Four series of polymer composites in which graphene and barium titanate (BaTiO3, BTO) were included for better dielectric performance—graphene oxide (GO) mixing with BTO, reduced graphene oxide (rGO) mixing with BTO, GO encapsulation of BTO, and rGO encapsulation of BTO. To find out the encapsulation of BTO in graphene, TEM, AFM, and Raman spectroscopy were performed on the dielectric samples. All graphene-included films showed 1.5~3 times higher values in the dielectric constants, regardless of the inclusion method, primarily due to the existence of graphene through the interfacial polarization of numerous micro-capacitors within the dielectric medium. On the while, the increase in the dielectric loss was nicely controlled, especially for encapsulation. The best performance came from the rGO encapsulated films, due to more conducting nature of rGO than GO, exhibiting a 300% higher dielectric constant (195 from 65) and a mere increase of 6% in the dielectric loss (0.033 from 0.031). It is the encapsulation by graphene that can minimize the percolation of graphene, i.e., the primary culprit of a poor dielectric loss. Thus, a smart mixing process with rGO, based on encapsulation and subsequent mixing, is desirable for high-performance dielectric composites, which can be easily applied to other two dimensional materials.

Figure 1
Investigation of Indium Oxide Nanowire Transform to Indium Zinc Oxide (IZO) Via Solid State Reactions
Authors: Chang Jing-Han , Lo Hung-Yang , Tseng Yi-Tang , Huang Chih-Yang , Ding Yi-Shin , Wu Wen-Wei
Published: May 2020

Transition metal oxide nanowires have attracted considerable attention due to their physical characteristics, chemical characteristics, and versatile applications. Among them, indium oxide (In203) nanowires demonstrate promising structure and electrical properties. Simultaneously, it used to be the reactants to synthesize indium zinc oxide (IZO) by solid-state reaction. The applicability would be highly related to the microstructure and synthesis process. Hence, study of conversion kinetics of IZO is essential. However, only few studies have mentioned the formation process of IZO and the solid-state diffusion mechanism. In this work, we successfully observed the transformation of novel IZO nanowire from interesting diffusion behavior between single-crystalline In2O3 nanowires and zinc oxide (ZnO). High resolution transmission electron microscope (HRTEM), fast Fourier transform (FFT) diffraction patterns and energy-dispersive spectrometer (EDS) were used for structural and compositional analysis. Based on the HRTEM images and the corresponding FFTs, the triclinic IZO was defined. Meanwhile, The in-situ TEM and EDS analysis provide the formation behavior and elemental distribution to elucidate the diffusion mechanism. This work exhibited the IZO nanowires with a unique structure and interesting formation behavior. Moreover, the study provides the improvement of controllability of conversion microstructure for further device applications.

Figure 1
(Invited) Electrical Properties of Vapor-Deposited Organic Semiconductor Nanowires By Conductive Atomic Force Microscopy
Authors: Park Kwang-Won , Bilger David , Andrew Trisha L.
Published: May 2020

Understanding how organic semiconductors self-assemble and create nanoscale morphologies is integral for the development of organic electronics. In particular, one-dimensional (1D) molecular nanostructures are of interest because of their unique optoelectronic properties as well as their potential role in fundamental charge transport research. Here, we investigate four small molecules (TpCPD, TpDCF, AcCPD, and AcDCF) possessing anisotropic, non-planar structures and large dipole moments, and establish robust algorithms to control their molecular self-assembly via physical vapor deposition. We find that only molecules containing the fused ring system form 1D nanowires due to the stronger van der Waals associations of the long, planar acenaphthene moieties. We examine the kinetics of self-assembly of AcDCF and create diverse 1D morphologies. Finally, using conductive AFM (c-AFM), we show that 1D wires support higher current densities relative to randomly-oriented clusters lacking long-range order through space-charge limited current (SCLC) measurements.

Figure 1
Measurement of Oxygen Transport through Separators in Flooded Batteries
Authors: Hostetler Eric , Duchateau Kaylee , Waterhouse Robert
Published: May 2020

An in-depth understanding of oxygen transport in flooded lead acid batteries is necessary to better understand and mitigate water loss in the next generation of batteries for start-stop vehicle applications. The presence of the oxygen cycle leads to a lower rate of water loss observed during intermittent drive cycle testing compared to the gassing that would be calculated from the integrated overcharge current into the battery [1]. A model of the oxygen cycle in flooded lead acid batteries has been proposed [2] but until recently the oxygen transport through the separator-electrolyte system hasn’t been measured.

A method for measuring oxygen transport through the separator-electrolyte system has been developed which uses electrodes harvested from commercial batteries. In this method, the separator is sealed between two chambers of a test cell, one containing the positive electrode and the other containing the negative electrode plus a reference. A constant stream of oxygen is delivered to the positive side of the cell using an air pump and diffuser. The negative side is purged, sealed and constantly stirred. The cell is charged and allowed to rest at OCV. Oxygen diffuses from the constant source on the positive side to the negative side where it oxidizes some of the negative active mass. This creates a measurable capacity change at the negative electrode which can be measured during a potentiostatically-controlled recharge cycle.

We will report on measurements of oxygen transport through the separator-electrolyte system for different separator materials in a flooded cell using commercial lead acid electrodes. Results are compared with modeling of the oxygen cycle and related to factors in the separator which influence the oxygen transport rate, such as porosity, pore size distribution and tortuosity,.

[1] Wirth, 16ELBC, 07 September 2018, Vienna Austria

[2] Meissner, Scientific Workshop: High-Temperature Durability Tests for Advanced Lead 12-V Batteries, 30 January 2017, Kloster Eberbach, Germany
(Invited) Understanding the Dynamics of Confined Species in Electrochemical Energy Storage Materials
Authors: Bridges Craig A. , Osti Naresh C. , Martins Murillo L. , Jafta Charl J , Mamontov Eugene , Sun Xiao-Guang , Paranthaman Mariappan Parans , Dai Sheng
Published: May 2020

Layered structures have played an important role in the development of electrochemical energy storage, for the relative ease of ion motion through two-dimensional diffusion channels, and for the stability of the host structure during battery operation. There have been several recent examples in which the performance of ion conducting materials has been improved through the presence of confined species between the layers, potentially through increasing the stability of the layers or enhancing the diffusion of ions. This may be observed for both electrode and electrolyte materials and is exemplified by the recent alternative to ionic liquid (IL) electrolytes, called conductive “solid-like” electrolytes, or the quasi-solid liquid electrolyte (QSLE). In the QSLE based upon boron nitride, ionic liquid electrolyte is confined within the BN layers. The electrolyte is intended to take the higher conductivity advantage of liquid electrolytes and combine this with the superior mechanical stability of BN based solid electrolytes. This hybrid solid electrolyte is derived from few layer nanoporous BN powders; the powders exhibit high surface area (> 800 m2/g) with layers and micropores (< 2 nm) for the infiltration of IL. X-ray diffraction indicates that the broad peak associated with the inter-layer separation shifts to longer d-spacing with absorption and confinement of IL. These infiltrated powders are then pressed to form a mechanically stable electrolyte, with high ionic conductivity. Such electrolytes can show robust stability against dendrite formation during battery cycling, which is a key issue in battery safety. While the properties look promising, there has been little fundamental effort to understand the nature of conduction in these solid-like electrolytes. The dynamics of the IL are expected to play a role in the diffusive motion of Na+/Li+ cations dissolved within the hybrid electrolyte. Prior work on confinement of ionic liquids using quasi-elastic neutron scattering (QENS), such as in the pores of a mesoporous carbon, have shown that the dynamics of the IL may not follow expected trends. For example, the translational motion of the IL may increase with confinement, and then slow down as the temperature is increased. Here we will present the effect of confinement on the dynamics of ionic liquid in 11BN layers using the BASIS spectrometer, and discuss this in relation to other confined electrochemical energy storage systems.
(Invited) Stabilizing Li Anodes using LLZO Membrane Technology
Authors: Sakamoto Jeff
Published: May 2020

There is tremendous interest in making the next super battery, but state-of-the-art Li-ion technology works well and has inertia in several commercial markets. Supplanting Li-ion will be difficult. Recent material breakthroughs in Li metal solid-state electrolytes could enable a new class of non-combustible solid-state batteries (SSB) delivering twice the energy density (1,200 Wh/L) compared to Li-ion. However, technological and manufacturing challenges remain. The discussion will consist of recent milestones and attempts to bridge knowledge gaps to include:

The physical and mechano-electrochemical phenomena that affect the stability and kinetics of the Li metal-solid electrolyte interface

Thin film processing and Li integration with LLZO

Plating and stripping dynamics of Li metal

Despite the challenges, SSB technology is rapidly progressing. Multi-disciplinary research in the fields of materials science, solid-state electrochemistry, and solid-state mechanics will play an important role in determining if SSB will make the lab-to-market transition.
(Invited) Challenges and Prospects for Next Generation Redox Flow Batteries
Authors: Narayan S. R. , Murali Advaith , Yang Bo , Nirmalchandar Archith , Prakash G. K. Surya
Published: May 2020

The need for affordable, durable and safe large-scale energy storage systems is rapidly growing with the increased deployment of solar and wind-based electricity generation. Aqueous redox flow batteries have the essential characteristics to meet the requirements for such energy storage systems. The past decade has seen considerable research into the scope and challenges of many types of redox materials for this application. The research for the next generation chemistries and systems must focus on lowering redox material cost and increasing durability. It would be beneficial to focus on inexpensive materials such as iron salts and redox couples based on small organic molecules that have shown significant promise. We must also advance our understanding of the factors affecting the capacity fade in aqueous systems, specifically relating to chemical stability, side reactions, and crossover. To this end, the challenge is to harness the advantages of the various organic molecular classes, substituent strategies and cell configurations to enhance the durability of future systems. In addition to low materials costs and durability, power density and efficiency are paramount to achieving low systems costs. The presentation will describe the need for a holistic approach to the challenges in designing next generation systems to meet the needs of rapidly emerging markets.
(Energy Technology Division Graduate Student Award Address sponsored by Bio-Logic) Understanding Charge Transport for Current and Future Electrochemical Energy Storage Technologies
Authors: Housel Lisa M. , Takeuchi Esther S , Marschilok Amy C. , Takeuchi Kenneth J
Published: May 2020

Advances in electrochemical energy storage are key for the integration of intermittent wind and solar energy sources into the grid, widespread adoption of electric vehicles, and development of new safe and reliable consumer devices. For grid, transportation, and electronic energy storage markets, each application has distinct needs. Therefore, developing battery technology for emerging and wide-spread applications demands greater understanding of the complex chemical and electrochemical processes that occur within rechargeable batteries. Electron transfer and ion transport are the foundation of battery function where the capacity, loaded voltage and current define the practical energy and power delivery of the system. During operation, repetitive addition and removal of electrons and ions can lead to structural change within the electrode and interfacial formation that can dramatically impact electrochemical outcomes. Thus, structural, chemical, and electrochemical characterization during operation is critically important for next generation electrochemical energy storage technologies. The research efforts highlighted in this talk use multiple advanced characterization techniques, including operando based methods, to probe charge transport properties, structural changes, and interfacial evolution in multiple rechargeable battery systems. Specifically, X-ray absorption spectroscopy enabled structure and oxidation state elucidation in the absence of long-range order. Isothermal microcalorimetry was used to determine heat evolution due to parasitic or decomposition reactions operando. X-ray diffraction was employed to track temperature-induced and lithiation-induced phase changes of distinct electroactive materials. Using advanced characterization, these research efforts provide insight into electron transfer and ion transport properties and their impact on application relevant outcomes (resistance, cycle life, delivered capacity) of electrochemical energy storage technologies.
Realizing an Asymmetric Supercapacitor Employing Carbon Nanotubes Anchored to Mn3O4 cathode and Fe3O4 Anode
Authors: Kumar Ankit , Sarkar Debasish , Mukherjee Soham , Patil Satish , D. Sarma D. , Shukla Ashok Kumar
Published: May 2020

A facile route to anchor pseudocapacitive materials on multi-walled Carbon Nanotubes (CNTs) to realize high-performance electrode materials for Asymmetric Supercapacitors (ASCs) is reported. The anchoring process is developed subsequent to direct decomposition of metal-hexacyanoferrate complex on the CNT surface. Transmission electron microscopy (TEM) analysis reveals that the nanoparticles (NPs) are discretely attached over CNT surface without forming a uniform layer, thus making nearly entire NP surface available for electrochemical reactions. Accordingly, CNT-Mn3O4 nanocomposite cathode shows significantly improved capacitive performance as compared to pristine CNT electrode, validating the efficacy of designing the composite electrode. With CNT-Fe3O4 nanocomposite as paired anode, the hybrid ASC delivers a specific capacitance of 135.2 F/g at a scan rate of 10 mV/s within a potential window of 0-1.8V in the aqueous electrolyte and retains almost 100% of its initial capacitance after 15000 cycles. The serially connected ASCs can power commercial LEDs and mobile phones reflecting their potential in next-generation storage applications.
(Invited) Size Controlled Silicon Quantum Dots: Basic Properties and Electronic Applications
Authors: Zacharias Margit , Gutsch Sebastian , López-Vidrier Julià , Garrido Blas
Published: May 2020

The fabrication of SiOx/SiO2 superlattices combined with thermal annealing enables the size and density control of Si quantum dots. The layered-arranged Si quantum dots represent a model system to systematically study the photonic and electronic properties of indirect gap quantum dots prepared in a CMOS compatible way. Hence, the model system is used to understand the interplay of absorption and recombination, the carrier kinetics and the electronic transport properties for matrix embedded Si quantum dots. The interplay of radiative and non-radiative recombination will be discussed for high quantum yield. Doping of Si quantum dots and the respective quantification is at the limit of the respective high resolution techniques but clearly show the effect of self-purification. Recent results using the Si quantum dots in memristor devices will be presented.
(Invited) New Strategies to Produce Light Emitters with Si-based Nanostructures
Authors: Favre Luc , Bouabdellaoui Mohammed , Assaf Elie , Guelil Imene , David Thomas , Ronda Antoine , Abbarchi Marco , Abel Mathieu , Rowell Nelson L. , Lockwood David J. , Berbezier Isabelle
Published: May 2020

Silicon-Germanium strain engineering has been used for more than two decades in silicon based devices and has contributed to the scaling down of a transistor’s size and to significant improvements in device performance. However, while conventional silicon-germanium based electronics has experienced rapid and steady growth, thanks to this continuous miniaturization of transistors, this trend cannot continue indefinitely. Industry has already moved to alternate methods such as FinFET devices, in which a thin silicon channel is placed vertically, and the FD-SOI (FD-SGOI) design consisting of a thin film Si(SiGe) channel placed horizontally. For nodes scaled down below 28 nm, low power operation will be inherently hindered by both the imperfect interface, non-uniformity of ultra-thin films and quantum confinement effects, which increase the effective bandgap. In these devices, despite the intense research activity on the strained SiGe ultra-thin body, which accounts for a large portion of such microelectronic devices (below the 45 nm node), we still fail to properly understand the mechanisms that limit hole and electron mobilities in SGOI layers. In addition, one of the main challenges for Si based devices remains the fabrication of efficient group-IV photon sources / photon detectors compatible with the microelectronic industry, which would usefully replace the integration of III-V heterostructures on Si. The major bottleneck is that group-IV semiconductor elements have indirect bandgaps, but with possibilities of being transformed to direct bandgaps using strain engineering strategies.

In this presentation, we will review the formation mechanism of Ge-rich layers on SOI by condensation at different temperatures. TEM cross-section and GPA analysis of the heterostructures will be presented. We will also report the physical and optical properties of these heterostructures. Special attention is devoted to the influence of the SiGe thickness reduction (up to few MLs), where quantum confinement is prominent in the optical properties of the layers. Raman and PL results will be presented to better explain such confinement behavior. We show that novel SGOI substrates could represent a key strategy for the fabrication of future photonic devices.
(Invited) Tuning the Optoelectronic Properties in Composite Systems for Sunlight Conversion
Authors: Vomiero Alberto
Published: May 2020

The processes of light absorption, exciton generation, charge separation and collection are critical to a series of applications, in which Sun light is either directly converted into electric power, like in solar cells, or transformed into chemical energy, like in photoelectrochemical hydrogen generation. All these processes are regulated by the optoelectronic properties of complex systems, in which the electronic band structure can be finely tuned by proper adjustment of chemical composition, size and morphology of the single components. Key element for the control of the optoelectronic properties is the modulation of the final electronic band structure. We will illustrate different strategies to obtain the desired optical and electrical properties in different complexes.

One of the most interesting systems is composed of semiconducting nanocrystals exhibiting quantum confined effects (the so-called quantum dots, QDs), which act as light absorbing materials, and generate excitons as a consequence of photon absorption. [1] The QDs are typically coupled to a wide bandgap semiconductor (SnO2, ZnO, TiO2), which acts as electron transport material. In this case, the optoelectronic properties are determined by the dynamics of hole/electron dissociation and recombination, and the structure of the interface between the QD and the oxide semiconductor regulates such dynamics. Another option is to apply core-shell QDs, in which the relative band alignment between the core and the shell can be tuned by tailoring the interface between them. [2]

We will illustrate a series of examples, [3] in which exciton dynamics in composite systems influences the functionality of the final device, including solar cells, photoelectrochemical hydrogen production and luminescent solar concentrators.

Keywords: Composite systems; quantum dots; exciton dynamics; solar cells; photoelectrochemical hydrogen generation; luminescent solar concentrators

References:

[1] Y. Zhou et al. Adv. En. Mater. 1501913 (2016): 6.

[2] G. Sirigu et al. Phys. Rev. B 155303 (2017): 96.

[3] X. Tong et al Nano Energy 441-449 (2017): 31.
(Invited) Small Yet Bright Lanthanide-Based Nanoparticles Via Rapid Microwave-Assisted Synthesis
Authors: Hemmer Eva
Published: May 2020

Based on their outstanding optical properties, lanthanide-based compounds have been suggested for a wide range of applications including the fields of biomedicine, optoelectronics, and solar energy conversion. For instance, the capability of lanthanide-based materials to emit visible and near-infrared (NIR) light under NIR excitation is highly sought after when aiming for biomedical applications. This is as NIR light penetrates deeper into biological tissue and is less phototoxic than UV light commonly used for optical bioprobes. Our favorite nanomaterials are lanthanide-based fluorides (MLnF4, M = alkali metal, Ln = lanthanides and Yttrium), and our research addresses challenges in their synthesis as well as the establishment of structure-property relationships. The growing attention toward such optically active materials has prompted the development of novel synthesis methods for a more reliable and efficient access to these systems. In this regard, microwave-assisted approaches provide unique advantages over traditional solvothermal methods reliant on convectional heating: namely, significantly shorter reaction durations, more rigid reaction conditions, and thus a higher degree of reproducibility. Upon control of multiple physico-chemical reaction parameters – including the choice of precursors, the reaction temperature/time profile, and the metal ion to Ln3+ ion ratio – MLnF4 materials of tailored crystalline phase and size at the sub-10 nm realm can be obtained. Such control is crucial for the understanding of fundamental structure-property relationships and when aiming for the design of design of next-generation bioprobes and energy converters. For instance, the upconverting properties of the obtained nanomaterials render them suitable energy donors when combined with lanthanide-based complexes acting as energy acceptors. Key features of the resulting hybrid system are the simultaneous UV-blue and NIR light harvesting capabilities. These traits render the presented hybrid system a formidable candidate for the development of photoactivated devices capable of operating under multiple excitation wavelengths and to transduce the absorbed light into narrow, well-defined spectral regions.
(Invited) Crystal Field Analysis of Eu3+ and Tb3+ Luminescence in Amorphous Silicon Alloys
Authors: Tessler Leandro R.
Published: May 2020

Trivalent rare earth ions efficiently emit luminescence in amorphous silicon based alloy hosts. The luminescence details depend mostly on the immediate chemical neighborhood of the ions. In crystals the luminescence peaks at low temperatures can be adjusted by lorentzian lineshapes with energies determined by the symmetry of the well defined lattice sites. In disordered materials however not only the local symmetry can change but also the local stoichiometry is not well defined. As a result the luminescence peaks become gaussian in shape. Nevertheless, by carefully adjusting the luminescence spectra information can be obtained about the local properties. We studied the luminescence of Eu3+ and Tb3+ in amorphous silicon alloys at low temperatures. The results indicate that Eu3+ is mostly on distorted cubic symmetry sites, while for Tb3+ it is not possible to determine the symmetry reliably. In any case, the results are compatible with the rare earth ions coordinated to residual oxygen in the alloys.
(Invited) Surfactant-Directed Quantum Dot Self-Assembly on Unconventional GaAs Surfaces
Authors: Lewis Ryan B.
Published: May 2020

The pursuit of integrated sources for quantum optics has motivated quantum dot research for decades. However, difficulties in controlling the geometry, symmetry and size-uniformity of self-assembled quantum dots has been a major roadblock in device development. While the Stranski–Krastanov (SK) growth of InAs three-dimensional (3D) islands has been extensively investigated on GaAs(001), the SK growth mode is not observed on GaAs (110) and {111}, the other low index surfaces of GaAs. This is unfortunate as these surfaces have symmetries (Cs and C3v, respectively) which differ from that of the (001) surface, and owing to their low energy they are often present in self-assembled nanostructures such as nanowires. Furthermore, the high symmetry of {111} surfaces is expected to yield quantum dots that are ideal for entangled photon emission.

Here we show that using a Bi surfactant to modify surface properties can profoundly influence epitaxial growth on GaAs (110) and (111)A surfaces. On GaAs(110), the Bi surfactant alters the fundamental growth mode of InAs from 2D layer growth to a 3D SK mode. Furthermore, a morphological phase transition can be induced “on-demand” in static strained 2D InAs(110) layers by exposing them to Bi, resulting in a rapid rearrangement of the InAs layer into 3D islands. Small (110) QDs are coherently strained to the substrate. These islands are optically active and exhibit emission that is linearly polarized, showing perspective for polarized single-photon emitters. On GaAs(111)A, GaAs buffer layer growth under a Bi flux results in ultra-smooth surfaces, which are free from the typically-observed morphological defects. Similar to the (110) case, exposing 2D InAs/GaAs(111)A layers to Bi induces the InAs 3D island self-assembly. These findings illustrate how surface-energy-modifying surfactants open the door to QDs synthesis on new substrates and with new materials.
(Invited) Oxide-Based Luminiscent and Active Nanophotonic Structures
Authors: Serna Rosalia , Toudert Johann , Gonzalo Jose , Mariscal Antonio , Soria Esther , Gomez-Rodriguez Pilar
Published: May 2020

In this talk we will discuss the potential of oxides for novel plasmonic and photonic devices. For this purpose, we have designed and produced highly functional thin film oxide metamaterials by either embedding non-oxide nanoparticles which act as optical resonators, or by growing pure nanostructured oxides with a fine control of their composition. In the former case we build robust plasmonic and sensing platforms that profit from the coupling between plasmonic and photonic modes[1-3]. And in the latter case we control the band-gap and thus the optical response tuning of the nanostructured oxide, thus creating a platform for integrated photonics [4]. In this context we will show the light emission properties of Europium oxides that can range from wide white band to narrow red emission, and how the coupling with metallic nanostructures enhances and modifies their spectral response.

[1]. J. Toudert, R. Serna, I. Camps, J. Wojcik, P. Mascher, E. Rebollar, T. Ezquerra, J. Phys. Chem. C 121, 3511 ( 2017).

[2] G. Baraldi, M.García Pardo, J. Gonzalo, R. Serna and J. Toudert, Adv. Mater. Interfaces 5, 1870058 (2018).

[3] J. Toudert, R. Serna, M. Pardo, N. Ramos, R. Peláez, and B. Maté, Opt. Express 26, 34043 (2018).

[4] A. Mariscal, A. Quesada, A. Tarazaga Martín-Luengo, Miguel A. García, A. Bonanni, J.F. Fernández and R. Serna, Appl. Surf. Science 456,980 (2018).
(Invited) Quantum Dot Displays
Authors: Sun Xiao Wei
Published: May 2020

We present highly efficient colloidal core-shell quantum dots, quantum rods and perovskite nanocrystals for emerging energy-saving quality display and lighting applications. We applied these luminescent materials to make various devices including luminescent microspheres for on-chip InGaN LED packaging (photoluminescent applications), and assembling aligned quantum rod to make polarized emission films. These nanocrystal materials were also used to make high efficiency quantum dot light-emitting diodes.
(Invited) Monolayer h-BN: Epitaxy, Properties, and Emerging Device Applications
Authors: Laleyan David , Wang Ping , Mi Zetian
Published: May 2020

Hexagonal boron nitride (h-BN) has shown tremendous promise when used alongside other two-dimensional (2D) materials such as graphene, and as a wide-bandgap semiconductor for deep-ultraviolet optoelectronics and quantum photonics. Owing to its large bandgap energy comparable or higher than Al(Ga)N, h-BN can be used to form heterostructures to address some of the critical challenges of Al(Ga)N-based systems. To date, however, many fundamental material properties of h-BN remain unknown. For example, its bandgap energy remains under debate, with reports spanning from 5.9 to 6.5 eV. There is also strong controversy as to whether h-BN has a direct or indirect bandgap. In this context, We have studied the epitaxy of h-BN by using ultrahigh temperature (up to 1850 °C) plasma-assisted molecular beam epitaxy (MBE) on sapphire, Ni and HOPG substrates. We show that, when grown at sufficiently high temperature, h-BN can exhibit predominantly excitonic emission at ~220 nm. The measured luminescence intensity is orders of magnitude higher than AlN under identical conditions. By forming a p-i-n structure using this high-quality h-BN as the active region, the current-voltage (I-V) and electroluminescence characteristics of a first demonstration of a h-BN deep UV LED will be reported.
Influence of Different Carbon Precursors on Optical and Electrical Properties of Silicon Carbonitride Thin Films
Authors: Abdelal Aysegul , Khatami Zahra , Mascher Peter
Published: May 2020

Silicon carbonitride (SiCN) thin films are widely used for protective hard coatings due to their superior mechanical and chemical properties such as high wear resistance, chemical and thermal stability at high temperatures, and hardness. Another scope of study of SiCN thin films is as the low dielectric constant (LKC) materials, which are desired for replacing silicon oxide (SiO2) in integrated circuits (IC). SiCN owes the interest shown to being an intermediate compound between silicon nitride (Si3N4) which is a highly transparent, wide band gap (5 eV) dielectric, and silicon carbide (SiC) with excellent mechanical performance.

In this study we present the optical and electrical properties of SiCN:H thin films fabricated by electron cyclotron resonance plasma enhanced chemical vapor deposition (ECR PECVD) by using a mixture of acetylene (C2H2) or methane (CH4), silane (SiH4), argon (Ar), and nitrogen (N2) gas precursors. Samples fabricated with two different carbon sources were analyzed and compared regarding their chemical composition as well as their electrical and optical properties. The atomic composition of Si, C, N, O, and H were determined by Rutherford backscattering spectrometry (RBS) and elastic recoil detection (ERD) analysis and the chemical bonds formed in SiCN:H were analyzed through Fourier transform infrared spectroscopy (FTIR). Optical bandgap, index of refraction and extinction coefficient were analyzed by variable angle spectroscopic ellipsometry (VASE) and will be presented for different deposition conditions. The dielectric constants and dielectric breakdown voltages of the thin films were determined through current-voltage (I-V) and capacitance-voltage (C-V) measurements. Lastly, the hardness properties are explained due to varying C and H concentrations.