bluuebunny/crossref_metadata_2025_split huggingface dataset:
Memory effect in nanostructured Si-rich hafnia films
Authors: Khomenkova L. , Portier X. , Gourbilleau F. , A.Slaoui  
Published: June 2019

ABSTRACTMicrostructral and charge-trap properties of single Hf-silicate dielectric films are presented versus annealing treatment. The as-grown films were found to be homogeneous and amorphous. It is shown that annealing treatment results in the formation of alternated Hf-rich and Si-rich layers. The mechanism responsible for this phenomenon is found to be surface directed spinodal decomposition. The increase of annealing temperature up to 1000-1100°C resulted in the crystallization of Hf-rich phase. The stability of its tetragonal phase caused an enhancement of film permittivity was observed. The evolution of charge trapping properties of the films results in the memory effect which nature was discussed.
Light-Emitting and Structural Properties of Si-rich HfO2 Thin Films Fabricated by RF Magnetron Sputtering
Authors: Khomenkov D. , An Y.-T. , Portier X. , Labbe C. , Gourbilleau F. , Khomenkova L. 
Published: June 2019

ABSTRACTStructural, optical and luminescent properties of Si-rich HfO2 films fabricated by RF magnetron sputtering were investigated versus annealing treatment. Pronounced phase separation process occurred at 950-1100°C and resulted in the formation of hafnia and silica phases, as well as pure silicon clusters. An intense light emission of annealed samples in visible spectral range was obtained under broad band excitation. It was ascribed to exciton recombination inside silicon clusters as well as host defects. To confirm the formation of Si clusters, the structures were co-doped with Er3+ ions and effective light emission at 1.54µm was obtained under non-resonant excitation due to energy transfer from Si clusters towards Er3+ ions. The interaction of Si clusters, host defects and Er3+ ions under is discussed.
Photoluminescence Variation With Temperature in ZnO:Ag Nanorods obtained by Ultrasonic Spray Pyrolysis
Authors: Velázquez Lozada E. , Mera Luna S. , Castañeda L. 
Published: June 2019

ABSTRACTThe photoluminescence, its temperature dependences, as well as structural characteristics obtained by the method of Scanning electronic microscopy (SEM) have been studied in ZnO:Ag nanorods prepared by the ultrasonic spray pyrolysis (USP). PL spectra of ZnO:Ag NRs in the temperature range from 10 K to 300 K are investigated. Three types of PL bands have been revealed: i) the near-band-edge (NBE) emission, ii) defect related emission and iii) IR emission. It is shown that IR emission corresponds to the second-order diffraction of near-band-edge (NBE) emission bands. The study of NBE PL temperature dependences reveals that the acceptor bound exciton (ABE) and its second-order diffraction peak disappeared at the temperature higher than 200 K. The attenuation of the ABE peak intensity is ascribed to the thermal dissociation of ABE with appearing a free exciton (FE). The PL bands, related to the LO phonon replica of FE and its second-order diffraction, dominate in the PL spectra at room temperature that testify on the high quality of ZnO:Ag films prepared by the USP technology.
Efficacy of Tobramycin Conjugated to Superparamagnetic Iron Oxide Nanoparticles in Treating Cystic Fibrosis Infections
Authors: Osiński Marek , Brandt Yekaterina I. , Armijo Leisha M. , Kopciuch Michael , Withers Nathan. J. , Cook Nathaniel C. , Adolphi Natalie L. , Smolyakov Gennady A. , Smyth Hugh D. C. 
Published: June 2019

ABSTRACTCystic fibrosis (CF) is an inherited childhood-onset life-shortening disease. It is characterized by increased respiratory production, leading to airway obstruction, chronic lung infection and inflammatory reactions. The most common bacteria causing persisting infections in people with CF isPseudomonas aeruginosa. Superparamagnetic Fe3O4iron oxide nanoparticles (NPs) conjugated to the antibiotic (tobramycin), guided by a gradient of the magnetic field or subjected to an oscillating magnetic field, show promise in improving the drug delivery across the mucus andP. aeruginosabiofilm to the bacteria. The question remains whether tobramycin needs to be released from the NPs after the penetration of the mucus barrier in order to act upon the pathogenic bacteria. We used a zero-length 1-ethyl-3-[3-dimethylaminopropyl] carbodiimide hydrochloride (EDC) crosslinking agent to couple tobramycin, via its amine groups, to the carboxyl groups on Fe3O4NPs capped with citric acid. The therapeutic efficiency of Fe3O4NPs attached to the drug versus that of the free drug was investigated inP. aeruginosaculture.
Experimental Characterization of frequency-depend electrical parameters of On-Chip Interconnects
Authors: Cortés Hernández Diego M. , Aranda Mónico Linares , Torres Reydezel Torres 
Published: June 2019

ABSTRACTAn exhaustive analysis of the frequency-dependent series resistance associated with the on-chip interconnects is presented. This analysis allows the identification of the regions where the resistance curves present different trending due to variations in the current distribution. Furthermore, it is explained the apparent discrepancy of experimental curves with the well-known square-root-of-frequency models for the resistance considering the skin-effect. Measurement results up to 40 GHz show that models involving terms proportional to the square root of frequency are valid provided that the section of the interconnect where the current is flowing is appropriately represented.
Large-Scale Electronic-Structure Calculations in the Real-Space Scheme: Bilayer Graphene and Silicene
Authors: Uchida Kazuyuki , Guo Zhixin , Iwata Jun-ichi , Oshiyama Atsushi 
Published: June 2019

ABSTRACTWe have developed our original DFT (density-functional theory) calculation code “RSDFT” using real-space schemes. The code is FFT-free, leading to high-performance computing in massively-parallel supercomputers. The code allows us to deal with systems including huge numbers of atoms from first-principles. We have applied our schemes to clarify atomic and electronic structures of two relevant nano-scale systems: twisted bilayer graphene and silicene on Ag substrate.
Effect of Molecular Weight on the Photovoltaic Performance of a Low band gap Copolymer blended with ICBA
Authors: Ibraikulov Olzhas , Bechara Rony , Lévêque Patrick , Leclerc Nicolas , Koishiyev Galymzhan , Heiser Thomas 
Published: June 2019

ABSTRACTAn increase in molecular weight of the polymer generally impedes solubility in common solvents and may influence the polymer optoelectronic properties as well. Indeed, higher molecular weights are expected to increase charge carrier mobilities and therefore give rise to better photovoltaic performances of bulk heterojunction solar cells. In this work, we use copolymers based on 2,1,3-benzothiadiazole, thiophene and thieno[3,2-b]thiophene units of various fractions differing in molecular weights almost by a factor of 4 with a fullerene based acceptor material Indene-C60 Bisadduct (IC[60]BA) to elaborate bulk heterojunction solar cells. We investigate the influence of post-deposition annealing temperatures and polymer:fullerene ratios on the final cell performances. We use IC[60]BA as an acceptor to enhance the open circuit voltage due to its high lying LUMO level [1]. Additionally, charge carrier mobilities were probed using bottom contact organic field-effect transistors. As expected, higher molecular weights (as long as homogeneity was maintained) resulted in an increase of the hole field-effect mobility (up to 7x10-3 cm2V-1s-1). Consequently, the power conversion efficiencies of bulk heterojunction solar cells could be improved by increasing the copolymer molecular weight. A power conversion efficiency of 2.4% with an open circuit voltage of 0.82V was reached in a standard device configuration with aluminum as a cathode after post-deposition thermal annealing.
Optimizing the DSSC Fabrication Process using Lean Six Sigma
Authors: Fauss Brian , Munukutla Lakshmi V. , Main Laura , Polesky Gerald , Kannan Arunachalanadar M. 
Published: June 2019

ABSTRACTDye sensitized solar cells (DSSCs) belong to an innovative third generation photovoltaic technology, which is demonstrating tremendous potential to become a revolutionary technology due to recent breakthroughs in fabrication cost. A seven-step quality improvement method is implemented to enhance process efficiency and effectiveness of the DSSCs. Lean Manufacturing’s 5S method successfully increased efficiency in all of the processes. Six Sigma’s DMAIC methodology is used to identify and eliminate each of the root causes of defects in the critical titanium dioxide deposition process. These optimizations resulted with the following significant improvements in the production process: 1. fabrication time of the DSSCs is reduced by 54 %; 2. fabrication procedures improved to the extent eliminated all critical defects 3. The yield of good cells increased from 17% to 90%.
Simulation of Galvanostatic Discharge of the LixC6/Liquid Electrolyte/Liy(NiaCobMnc)O2 Cell
Authors: Chandrasekaran Rajeswari , Seong Yeonkyeong , Bae Chulheung , Jung Joosik , Kim Kwangsoo , Cheong Kyeongbeom , Miller Theodore 
Published: June 2019

ABSTRACTAn isothermal, physics-based model was developed in COMSOL multiphysics software to simulate the galvanostatic discharge performance of LixC6/Liquid Electrolyte/ Liy(NiaCobMnc)O2 dual lithium-ion insertion cell at 298 K. Modeling results are compared with experimental data to provide further insight into design and optimization of these cells for advanced electric vehicles.
Development of nanotechnology experimental modules using ferrofluids for high school classrooms
Authors: Chopra Nitin , Shi Wenwu , Peramsetty Nikita R. , Evans Victoria L. 
Published: June 2019

ABSTRACTNanotechnology and nanoscience have a strong potential to impact society and the commercial sector. It is critical to introduce this area to high school classrooms as a teaching tool. Here, we report the development of ferrofluid-based experimental modules in a team effort including a high school student and a high school teacher. The basic experimental modules were developed as follows: A) Electric motor-based patterning of magnetic nanoparticles and carbon nanotubes on a silicon wafer. Electromagnetically activated or ‘spiked’-ferrofluid was utilized here. B) Basic concepts of wettability, hydrophobicity, and oleophilicity were demonstrated by combining hydrophobic CNTs, water, and ferrofluids. C) Finally, the utility of ferrofluid-based environmental remediation was demonstrated for oil removal from oil-water mixture and organic dye separation from water-dye mixture. It is envisioned that the integration of the developed experimental modules into high school curriculum will motivate high school students to pursue degrees in science, engineering, and nanotechnology. Thus, this will assist in the development of future workforce in the area of nanotechnology and materials science.
Introducing Raman Spectroscopy of Crystalline Solids in the Undergraduate Curriculum
Authors: Roughani Bahram , Warner David , Ramabadran Uma 
Published: June 2019

ABSTRACTWe describe an experiment designed as an upper level physics laboratory that introduces students to Raman Scattering of electronic materials and research methodology. This experiment is an effective approach in demonstrating the relationship between the Raman intensity of the scattered light from crystals and symmetry dependent Raman selection rules. In our measurements we alter the angle between the crystal axis and the polarization of the incident laser beam by Si (100) sample rotation. The three dimensional plot of the intensity profile versus the theoretical model is used to distinguish differences between various crystal planes of the same electronic sample. This experiment will combine optical analysis with materials aspects of electronic materials.
Education and Dissemination: Lab-to-Market-to-Classroom
Authors: Campo E. M. 
Published: June 2019

ABSTRACTIn this paper, we present a work plan for the dissemination of refreshable, photoactuatable tactile displays to the visually impaired, serving both Lab-to-Market and Lab-to-Classroom initiatives. The work plan is designed in accordance with the logic model, which identifies an overlap amongst classroom, market, and laboratory. This overlap seems to nucleate when a technology in developmental phase is deployed in a classroom with high affinity to such technology. In this scheme, students are stakeholders whom help decide both content and applications to be included in the developing curriculum, and provide technology feedback, effectively leading to increased consumer acceptance. The identified Lab-to-Market-to-Classroom continuum could be the missing link where to nurture sustainable scientific, technological, and curricular development.
Manipulation of interface electronic structure by thin metal oxide films
Authors: Wang Chenggong , Irfan  , Gao Yongli 
Published: June 2019

AbstractWe have investigated the counter intuitive phenomenon of inserting a metal oxide layer to improve hole injection or extraction in organic semiconductor devices using ultraviolet photoemission, x-ray photoemission, and inverse photoemission spectroscopy (UPS, XPS and IPES). We observed that metal oxides, such as MoO3, substantially increase the work function when deposited on indium-tin-oxide (ITO). The increase lifts up the highest occupied molecular orbital (HOMO) of the hole transport layer, therefore reduces the energy barrier between the HOMO and the Fermi level of the anode. The uplift creates an interface band bending region that results in a drift electric field that encourages the collection of holes at the anode. The optimum thickness for the oxide layer is estimated to be 2 nm. We have also investigated the effects of ambient or O2 exposure of MoO3. We observed that while most of the electronic energy levels of the oxide remained largely intact, the work function reduction was significant. This opens a way for optimal energy level alignment by modifying the work function through exposure. Furthermore, we observed that the work function reduction by exposure could be reversed by proper annealing of the sample in vacuum. The investigations therefore point to manipulate the interface electronic structure and charge injection/extraction by thin metal oxide films.
High-Conductivity Solution-Processed Carbon Nanotube Networks as Transparent Electrodes in Organic Solar Cells
Authors: Ostfeld Aminy E. , Fogden Siân , Catheline Amélie , Kim Kee-Chan , Ligsay Kathleen , McFarlane Graham A. , Arias Ana Claudia 
Published: June 2019

ABSTRACTSolutions of individual, unbroken single-walled carbon nanotubes in organic solvent were fabricated in a reductive dissolution process. Transparent conductive films deposited from these organic inks gave a significantly higher conductivity to absorptivity ratio than those cast from an aqueous dispersion of carbon nanotubes. For example, films from the organic ink have achieved a sheet resistance of 250 Ω/□ with transmittance of 92% at 550 nm wavelength, compared to 76% transmittance for a 250 Ω/□ film from the aqueous dispersion. The promise of these films as transparent electrodes has been demonstrated by their incorporation into organic solar cells with power conversion efficiency of 2.3%, comparable to that of solar cells produced using indium tin oxide transparent electrodes.
Parameter Study on UV-induced Degradation of Dye-sensitized Solar Cells
Authors: Jensen Katrine Flarup , Veurman Welmoed , Brandt Henning , Im Chan , Wilde Jürgen , Hinsch Andreas 
Published: June 2019

ABSTRACTThe present work investigates the UV stability of the dye-sensitized solar cell (DSC) by parametrical investigation of the material influence on UV stability. UV illumination has been observed to cause degradation by slow photocatalysis in the DSC. Photooxidized impurities represent an unwanted side reaction with the redox pair of the electrolyte as the released electron will deplete the triiodide concentration. A study on the DSC cell was carried out with intermediate electrical characterization by cyclic voltammetry (CV) and electrical impedance spectroscopy (EIS) to map the influence of UV illumination as a function of the H2O concentration in the electrolyte, the plate distance and the triiodide concentration. The results show that the H2O content has a detrimental influence on the DSC stability during UV illumination. A higher concentration of triiodide can buffer the reaction with impurities, so that a longer-term stability is achieved. A recovery of triiodide in UV aged cells with either no remaining triiodide or with such a low concentration that the cell current has been diffusionlimited, was seen during CV to -0.75 V under illumination. The reappearance of triiodide was accompanied with a production of hydrogen bubbles, which was related to the H2O content in the electrolyte and the exposure to UV. Our approach can be used to test the purity and the UV stability of various electrolytes.
Effect of Copper Sulfide nanocrystals in a Poly(3-hexylthiophene)/Titania solar cell
Authors: Quintana-Ramírez Priscilla V. , Arenas M. C. 
Published: June 2019

ABSTRACTPoly(3-hexylthiophene)/Titania (P3HT/TiO2) heterojunction has been widely studied in the field of hybrid solar cells. Usually, organic dyes shift the neat TiO2 absorption edge toward the visible range improving the conversion efficiency or/and the TiO2 surface is modified with ligands in order to increase the electron transport. On the other hand, copper sulfide, non-toxic semiconductor, has been included in bulk organic P3HT based solar cell, increasing the photocurrent density of devices. Therefore, we propose the use of copper sulfide in the hybrid TiO2/P3HT heterojunction to determine its effect in the performance of TiO2/P3HT solar cell. Copper sulfide nanocrystals (CuxS) were synthesized at 230 °C, 240 °C and 260 °C and, they were mixed with P3HT in order to form P3HT:CuxS bulk heterojunctions. Scattered grains and irregular morphology in the final topography of the reference device (P3HT/TiO2 heterojunction) were observed by AFM, while a granular morphology and a few pores like craters were observed in the devices containing P3HT:CuxS bulk heterojunctions. Chalcocite phase (Cu2S) was obtained at 230 and 240°C and, digenite (Cu1.8S) phase at 260°C, both copper sulfide phases are very promising for solar cells. Despite this, poor rectifications in the devices were found in the current-voltage curves of the devices containing copper sulfide nanocrystals in contrast to the P3HT/TiO2 cell (device without nanocrystals), it could be due to the current leakage or recombination process in the copper sulfide/TiO2 interface. It suggests future work in order to improve the devices.
Probing Confinement Effects on Multilayered Ferroelectric Polymer Films Using Second Harmonic Generation
Authors: Jones J. , Zhu L. , Tolk N. , Mu R. 
Published: June 2019

ABSTRACTElectrical energy storage plays a key role in mobile electronic devices, stationary power systems, and hybrid electrical vehicles. High energy density capacitors based on dielectric polymers are a focus of increasing research effort motivated by the possibility to realize compact and flexible energy storage devices, taking advantage of light weight and facile processability of organic materials. In addition, dielectric polymers enjoy inherent advantages of self-healing mechanism and high breakdown strength, leading to capacitors with great reliability and high energy density. It is the focus of this group to develop a multilayered ferroelectric PVDF system for improved energy storage efficiency. These systems are fabricated using enabling technology in co-extrusion which allows more cost effective and large area device production as opposed to more conventional layer-by-layer techniques. Many efforts have been made by the team to fabricate these micro- and nano-layered systems resulting in much improved device performance. A three-time improvement of capacitive electrical energy density has been demonstrated. The focus of this research is to understand the physics of why these multilayered systems perform better than a single layer by developing a characterization technique using both confocal second harmonic generation (SHG) and electric field induced second harmonic (EFISH) laser spectroscopy. Our results have shown that SHG is a very sensitive, non-destructive and versatile technique that can be used to study the ferroelectric and structural properties of layered systems. When combined with EFISH this technique allows the interrogation of structural and dielectric properties within the individual layers and at the interfaces between the layers. Further, the proposed techniques can be readily employed in-situ which can provide information in real time during sample processing with static and time-resolved spectroscopic measurements.
Competition between Exciplex Formation and Photocarrier Generation in Molecular-Scale Donor-Acceptor Heterojunctions
Authors: Tsutsumi Jun’ya , Yamada Toshikazu , Matsui Hiroyuki , Hasegawa Tatsuo 
Published: June 2019

ABSTRACTDonor-acceptor mixed-stack charge-transfer (CT) compounds can be regarded as a model system for charge carrier separation in molecular-scale donor-acceptor heterojunctions. Here we investigated fundamental photocarrier generation characteristics in single crystals of a donoracceptor mixed-stack system, phenothiazine-tetracyanoquinodimethane (PTZ-TCNQ). The laser beam-induced current (LBIC) measurement on the crystals allowed the discrimination between the exciton and the photocarrier diffusion on the basis of the observed spatial decay profiles. We found that the photocarriers are directly generated by higher-lying CT band excitation and exhibit extremely long diffusion length reaching more than 10 μm. We discuss the origin of the efficient photocarrier generation in terms of the geminate electron-hole pair formation.
Analytical Model for Heat Transfer in a Finite Region of Organic Phase Change Materials
Authors: Zhu Yejun , Huang Baoling , Wu Jingshen 
Published: June 2019

ABSTRACTThe concept of low carbon, energy saving and sustainable design has been widely accepted all over the world. As a matter of fact, large amount energy is consumed to control the indoor environment to maintain a comfortable ambience for living and working. To increase the energy utilization efficiency, phase change material (PCM), which can store and release heat through phase change, has been recognized as an excellent candidate for green building. Analytical model is of great importance to describe and predict heat transfer with phase change. The classic Stefan problem solution is quite suitable for crystalline materials, which requires the input of certain phase change temperature. However, many PCMs widely used, like paraffin, are semi-crystalline materials, which have a much larger phase changing temperature range compared with small molecule crystalline materials. It is important to appropriately model the phase change of semi-crystalline polymers for the application of PCM. Furthermore, in large spatial scale prediction, widely used semi-infinite plane model is usually quite suitable to explain initial heat transfer. Unfortunately, semi-infinite plane is not the same as real situation. In this paper, by using the temperature at the end of the phase change as the equivalent melting temperature, a heat transfer model for semi-crystalline organic PCM is constructed. Meanwhile, this model concerns the phase change in a limited region. This model can serve as a fast tool to predict the one-dimensional heat transfer with phase change in an explicit form. The model is validated by the results of simulations and experiments reported in the literature.