bluuebunny/crossref_metadata_2025_split huggingface dataset:
Laboratory and Modelling Studies of Sodium Benionite Grounmater Interaction
Authors: Sneujman M. , Uotiia H. , Rantanen J. 
Published: June 2019

AbstractAccording to the present Finnish concept sodium bentonite will be used as a buffer material in the repository for high-level waste. Experimental and theoretical studies treating the effect of bentonite upon the chemical conditions in a repository have been initiated with the object of specifying the chemistry of the near field.Sodium bentonite was let react with water under anaerobic conditions at 25°C for 540 days, during which time six fluid samples were extracted for the chemical analysis of 15 chemical species. The generated fluid phase was alkaline (PH = 9…10) and contained a high amount of bicarbonate. Also a low redox-potential was measured. The fluid phase chemistry was investigated using the geochemical code PHREEM. Calcite saturation was observed in all fluid samples.A modelling of sodium bentonite interaction with water based on the main mineral components of bentonite was also performed with PHREEQE. A fairly good agreement between experimental results and model calculations was observed.
Effects of N2O Fluence on the PECVD-grown Si-rich SiOx with Buried Si Nanocrystals
Authors: Lin Chun-Jung , Kuo Hao-Chung , Chen Chia-Yang , Chueh Yu-Lun , Chou Li-Jen , Chang Chih-Wei , Diau Eric Wei-Guang , Lin Gong-Ru 
Published: June 2019

AbstractThe optimized N2O fluence is demonstrated for plasma enhanced chemical vapor deposition (PECVD) of Si-rich substoichiometric silicon oxide (SiOx) films with buried Si nanocrystals. Strong room-temperature photoluminescence (PL) at 550-870 nm has been observed in SiOx films grown by PECVD under a constant SiH4 fluence of 20 sccm with an N2O fluence varying from 105 sccm to 130 sccm. A 22-nm-redshift in the central PL wavelength has been detected after annealing from 15 min to 180 min. The maximum PL irradiance is observed from the SiOx film grown at the optimal N2O fluence of 120 sccm after annealing for 30 minutes. Larger N2O fluence or longer annealing time leads to a PL band that is blue-shifted by 65 nm and 20 nm, respectively. Such a blue shift is attributed to shrinkage in the size of the Si nanocrystals with the participation of oxygen atoms from N2O incorporated within the SiOx matrix. The (220)-oriented Si nanocrystals exhibit radii ranging from 4.4 nm to 5.0 nm as determined by transmission electron microscopy (TEM). The luminescent lifetime lengthens to 52 μs as the nc-Si size increase to > 4 nm. Optimal annealing times for SiOx films prepared at different N2O fluences are also reported. A longer annealing process results in a stronger oxidation effect in SiOx films prepared at higher N2O fluences, yielding a lower PL irradiance at shorter wavelengths. In contrast, larger Si nanocrystals can be precipitated when the N2O fluence becomes lower; however, such a SiOx film usually exhibits weaker PL at longer wavelength due to a lower nc-Si density. These results indicate that a N2O/SiH4 fluence ratio of 6:1 is the optimized PECVD growth condition for the Si-rich SiO2 wherein dense Si nanocrystals are obtained after annealing.
Bifacial Silicon Heterojunction Solar Cell with Deposited Back Surface Field
Authors: Goldbach H. D. , Bink A. , Schropp R. E. I 
Published: June 2019

AbstractSilicon heterojunction cells (SHJ) using crystalline silicon wafers and deposited heterojunction thin film emitters are interesting from an economical, technological, and sc ientific point of view. Modules using such cells (so called HIT cells) are commercially produced by Sanyo Electric Co., using single crystal wafers. Recently reported alternatives still comprise a high-temperature diffused back surface field (BSF). In order to provide a low cost alternative, our goal is to develop SHJ using multicrystalline silicon wafers with both a deposited emitter and a deposited BSF. The present approach truly allows the development of a cheap, low temperature, all-deposited alternative for the HIT cell.We made a bifacial silicon heterojunction solar cell, with an emitter consisting of a 7 nm intrinsic a-Si:H layer and a 15 nm n-type μc-Si:H layer. The back surface field is formed by a 30 nm p++ μc-Si:H layer. In order to achieve a functional deposited BSF the thin p++-layer has to have higher effective dopant concentration than the substrate. We used a 375 μm thick FZ wafer with a resistance of 1 cm with an activation energy of 0.2 eV. The μc-Si:H p++-layer has an activation energy of Ea = 0.082 eV. To detect the operation of the BSF the cell was made bifacial. The cell has an efficiency of 14.87 %, Voc = 571.4 mV and Jsc = 33.3 mA/cm2, Rs = 1.2 Ωcm2 and Rp = 1.8 kΩcm2. The cell, illuminated from the back, shows a Voc of 0.1 V and Jsc of 7 mA/cm2. Reference bifacial cells without BSF show no cell behavior illuminated from the rear side. External quantum efficiency (EQE) measurements with illumination at the rear side of the bifacial heterojunction cell with BSF show a quantum efficiency value of 0.17 in the range 500-800 nm, while the reference cell without BSF shows zero quantum efficiency in this range. These results show evidence for the feasibility of a truly functioning deposited BSF combined with a SHJ with deposited emitter.
High-Performance Amorphous Silicon Emitter for Crystalline Silicon Solar Cells
Authors: Wang T.H. , Iwaniczko E. , Page M.R. , Wang Q. , Levi D.H. , Yan Y. , Xu Y. , Branz H.M. 
Published: June 2019

AbstractThin hydrogenated amorphous silicon (a-Si:H) layers deposited by hot-wire chemical vapor deposition (HWCVD) are studied for use as the emitter in silicon heterojunction (SHJ) solar cells on p-type crystalline silicon wafers. Low interface recombination velocity and high open-circuit voltage are achieved by a low substrate temperature (<150°C) intrinsic a-Si:H deposition which ensures immediate amorphous silicon deposition. This is followed by deposition of n-type a-Si:H at a higher temperature (>200°C) which improves dopant activation and other properties. A prolonged atomic H pretreatment to clean the c-Si surface is actually detrimental because it creates additional defects in the c-Si lattice. However, a brief H pretreatment is beneficial and may render the intrinsic interlayer unnecessary. The n-type a-Si:H thickness must be limited to ~5 nm to minimize current loss, because the phosphorous doped a-Si:H layer has significant absorption in the usable solar spectrum. Using the optimized a-Si:H emitter, we obtain efficiency of nearly 17% on planar float-zone (FZ) silicon and 15% on planar Czochralski (CZ) silicon substrates with aluminum back-surface-field (Al-BSF) and contacts.
Electrodeposition of Fluorescent Si Nanomaterial From Acidic Sodium Silicate Solutions
Authors: Abuhassan Laila H. , Nayfeh Munir H. 
Published: June 2019

AbstractWe developed a procedure for the electrodeposition of fluorescent silicon nanomaterial from silicates on conducting substrates. The electrodeposion solution used is a solution of sodium metasilicon salts (Na2SiO3) in HF/H2O2. When a positively biased platinum substrate is immersed in the bath, a current is drawn and a thin fluorescent coating is formed on the substrate. We discuss the results in terms of current-induced nucleation of silicon nanostructures.
Depth-profiling Pore Morphology in Nanoporous Thin Films Using Positronium Lifetime Annihilation Spectroscopy
Authors: Vallery Richard S. , Peng Hua-Gen , Frieze William E. , Gidley David W. , Moore Darren L. , Carter Richard J. 
Published: June 2019

AbstractPositronium annihilation lifetime spectroscopy (PALS) using a positron beam is a proven technique to characterize porosity in amorphous thin film materials. The capability to control the depth of the implanted positrons is unique to beams as compared to traditional bulk PALS techniques. By increasing the positron beam energy, positrons are implanted deeper into the film. Control of the positron implantation depth in beam-PALS allows analysis of sub- micron films, investigation of depth-dependent film inhomogeneities, determination of pore interconnection lengths, and access to buried films under barrier layers. Details on PALS depth profiling and an example of applying the technique to a plasma-enhanced-chemical-vapor- deposited (PECVD) porous film are presented.
First Pass Study of Surface Modified Porous Low-k by Ion Implantation for Zero Thickness Barrier Requirement of Cu/MSQ/Si Stacks in Copper Metallization Scheme
Authors: Nandini Alok , Roy U. , Patel Zubin P. , Bakhru H. 
Published: June 2019

AbstractLow-κ dielectrics have to meet stringent requirements in material properties in order to be successfully integrated. A particularly difficult challenge for material development is to obtain a combination of low dielectric constant with good thermal and mechanical properties. Incorporation of low dielectric constant materials such as porous silica based materials as a replacement to conventional dielectrics like SiO2 and use of Cu metallization schemes has become a necessity as critical dimensions of devices decrease. This paper is focused on the challenges in developing materials with low dielectric constant but strong thermo mechanical properties.
Thin films of Ultra-Low materials such as porous Methyl Silsesquioxane (MSQ) (κ=2.2) were implanted with argon 1 × 1016 cm-2 dose at energies varying from 20 to 50 keV at room temperature. This work shows that the surface hardness of the porous films can be improved five times as compared to the as-deposited porous films by implanting Ar with 1 × 1016 cm-2 doses at 20 keV, sacrificing only a slight increase (∼9%) in dielectric constant (e.g., from
2.2 to 2.4). The hardness persists after 4500C annealing. In this current work, an ion implantation strategy was pursued to create a SiO2-like surface on MSQ. The effects of implantation parameters on the barrier property and bulk stability of MSQ were then studied. The results reveal one possible route to attain the “zero barrier thickness” requirement for interconnects systems.
Stress Generation in PECVD Silicon Nitride Thin Films for Microelectronics Applications
Authors: Belyansky M. , Klymko N. , Madan A. , Mallikarjunan A. , Li Y. , Chakravarti A. , Deshpande S. , Domenicucci A. , Bedell S. , Adams E. , Coffin J. , Tai L. , Sun S.P. , Widodo J. , Lai C.W 
Published: June 2019

AbstractThin SiN films deposited by plasma enhanced chemical vapor deposition (PECVD) have been analyzed by a variety of analytical techniques including Fourier Transform Infrared Spectroscopy (FTIR), X-ray reflectivity (XRR), and Rutherford Backscattering Spectrometry/Hydrogen Forward Scattering (RBS/HFS) to collect data on bonding, density and chemical composition respectively. Both tensile and compressive SiN films have been deposited and analyzed. Mechanisms of stress formation in SiN thin films are discussed. It has been found that amount of bonded hydrogen as detected by FTIR is higher for compressive films compared to tensile SiN films. Amount of bonded hydrogen in a film is correlated well with tensile stress. Effect of deposition temperature and other process parameters on stress have been studied. Exposure of SiN films to elevated temperature after deposition lead to increase in tension and degradation in compressive stress. New approaches to stress generation in thin films like creation of multilayer film structures have been delineated.
Application of Nanoindentation to Characterize Fracture in ILD Films Used in the BEOL.
Authors: Simonyi Eva E. , Liniger E. , Lane M. , Lin Q. , Dimitrakopoulos C. D. , Tyberg C. 
Published: June 2019

AbstractIt is of importance to understand cracking behavior in low dielectric constant, low modulus materials. Nanoindentation method is presented as a tool to estimate the critical film thickness, thickness above which spontaneous cracking could occur, for ILD films used in the BEOL. The critical film thickness was then used to calculate cohesive energies and fracture toughness of the films. Materials were investigated using nanoindentation combined with AFM imaging. The results were compared to data acquired by four point bend methods.
Reduction of Residual Transient Photocurrents in A Si:H Elevated Photodiode Array Based Cmos Image Sensors
Authors: Theil Jeremy A. 
Published: June 2019

AbstractWhile a-Si:H based elevated photodiode arrays hold the promise of superior performance and lower cost CMOS-based image sensors relative to those based upon crystalline silicon photodiodes, the one area where a-Si:H based sensor performance has not been as good is in image lag. This problem is only exacerbated by Staebler Wronski Effect induced junction degradation. Image lag is caused by residual charge from photocurrents trapped within the junction once the light source is removed and can be measured for several seconds, even under continuous applied reverse bias. It is seen both in constant and variable bias pixel architectures. However, by carefully controlling a-Si:H junction bias conditions, it is possible to significantly reduce these transient photocurrents. This article will describe how the photocurrent decay time exponent can be reduce by almost an order of magnitude. Finally the physical causes behind image lag in a-Si:H based photodiode arrays will be discussed.
Efficient Focusing with an Ultra-Low Effective-Index Lens Based on Photonic Crystals
Authors: Foca Eugen , Föll Helmut , Daschner Frank , Sergentu Vladimir V. , Carstensen Jürgen , Knöchel Reinhard , Tiginyanu Ion M. 
Published: June 2019

AbstractThis work focuses on photonic crystals (PC) that can be ascribed an effective index of refraction > 1 or even > 0. We investigate the possibility to design optical elements (in this case a lens) based on this type of PC. A new approach for determining the effective refractive index of PCs with unusual index of refraction is used, which is simpler than earlier methods based on analyzing equi-frequency surfaces in k-space. An ultra-low refractive index PC is given a form approximating a concave lens and is proven theoretically and experimentally that it efficiently focuses the electromagnetic radiation in the microwave range. Strong focusing effects are found for both polarizations (TE and TM mode). Intensity gains as large as 35 for TM polarizations and 29 for TE polarizations are found. Measurements are in a good accordance with simulations.
MBE Growth of GaAs on Si through Direct Ge Buffers
Authors: Yu Xiaojun , Kuo Yu-Hsuan , Fu Junxian , Harris James S 
Published: June 2019

AbstractThe result of GaAs growth on Si using a thin Ge buffer layer (about 0.5μm thick) is presented in this paper. A two-step method with a high temperature anneal between two steps is used to grow the Ge buffer layer. Single phase GaAs is grown on Ge by controlling the growth temperature, substrate miscut and the prelayers. No APD defect is observed by the XTEM and the threading dislocation density of GaAs grown using this method is about 5˜10×107cm-2. The PL intensity of GaAs is 10× less on Si substrate than on GaAs substrates.
Novel Strategy for Antifouling Paints with Zero Endocrine Disrupting Chemical (EDC) Elution based on Interpenetrating Polymer Networks (IPNs)
Authors: Naito Masanobu , Nakai Takashi , Kawabe Takuma , Mori Kenji , Furuta Daisuke , Imanishi Yukio , Fujiki Michiya 
Published: June 2019

AbstractEnvironmentally friendly organic-inorganic hybrid materials with repellent activity against marine fouling organisms have been developed using interpenetrating polymer networks (IPNs), composed of a three-dimensional silica matrix of tetraethoxysilane (TEOS) and chain-like polymers, such as poly(methylmethacrylate) (PMMA) and poly(vinylacetate) (PVAc). The repellent activity of the IPNs reached a maximum of approximately 90% relative to that of tetrabutyl tin oxide (TBTO). Simple bioassays using blue mussels and algae were used to screen out the adequate proportions of those components.
Fabrication of Coated Polycaprolactone Scaffolds and Their Effects on Murine Embryonic Stem Cells
Authors: Tollon Michael H. , Hamazaki Takashi , Willenberg Bradley J. , Batich Christopher , Terada Naohiro 
Published: June 2019

AbstractIn the past decade, tissue engineering has become a great interest in materials science research. Embryonic stem (ES) cell transplantation has become one of the most researched therapies for restoring tissue and organ function. Many studies have investigated the use of porous biodegradable scaffolds to promote cell adhesion, growth, proliferation, differentiation, and to help steer the course of tissue development. Research has shown that extracellular matrices and the basement membranes affect various cell types and cellular behaviors. However, the effects of these materials on ES cell behavior are currently understudied and poorly understood.In this study, the synthetic biodegradable polymer polycaprolactone (PCL) was chosen to create an interconnected, fibrous foam structure. A phase separated scaffold method was developed and the product made was coated with various extracellular materials. When the phase separated PCL scaffolds were coated with Matrigel and gelatin solutions, murine ES (mES) cells attached, spread, and differentiated within the scaffolds. There was little growth on the uncoated material. Coating effects on mES cells were analyzed using flow cytometry, reverse-transcriptase polymerase chain reaction and scanning electron microscopy. It was found that coating the scaffold with different extracellular matrices affects mES cell morphology and differentiation. Matrigel coating causes expression of neural proteins and gelatin produces a hepatocyte-like cell.
Functionalized Calcium Phosphate-based Nanoparticles for the Treatment of Osteoporosis
Authors: G Balasundaram , M Sato , TJ Webster 
Published: June 2019

AbstractIn an effort to decrease the number of problems associated with osteoporosis, the long-term goal of the present study is to design calcium phosphate-based nanoparticles that specifically attach to areas of low bone density and once attached, allow for the targeted release of bioactive agents that can quickly increase bone formation. Efforts are focused on nanoparticles of calcium phosphate-based materials since they are similar in size and chemistry to the major inorganic components of bone. As a first step in this research, the objective of the present study was to synthesize nanoparticles of crystalline hydroxyapatite (or HA) and amorphous calcium phosphate. Crystalline HA is stable under physiological fluids and, thus, will release embedded bioactive agents slowly. Alternatively, amorphous calcium phosphate is highly biodegradable and will, thus, release embedded bioactive agents quickly. A further objective of the present study was to functionalize such inorganic biodegradable materials with amino groups which would allow for the subsequent attachment of entities to direct such nanoparticles to osteoporotic bone and increased bone formation once attached. One promising approach to direct the nanoparticles to osteoporotic bone is to attach antibodies to pentosidine on the nanoparticles since pentosidine is present in higher amounts in osteoporotic compared to healthy bone. A promising approach to increase bone growth once nanoparticles attach to osteoporotic bone, is to embed nanoparticles with regions of the bone growth factor: bone morphogenic protein-2 (or BMP-2). Results of this study demonstrated the successful synthesis of both crystalline HA and amorphous calcium phosphate nanoparticles. Furthermore, results showed that these nanoparticles can be functionalized with versatile amino groups. In this manner, this study takes the first steps toward utilizing calcium phosphate based nanoparticles to reverse bone loss associated with osteoporosis.
Nanobiohybrids: Bioinspired Sensors
Authors: Chalkias Nikolaos , Giannelis Emmanuel P. 
Published: June 2019

AbstractNanohybrid artificial membranes made by intercalation of amphiphilic molecules into the galleries of a layered host, exhibit characteristics similar to biological membranes and they can be used as sensors. Different responses have been observed even for molecules that have similar features for example, saccharin and its sodium salt suggesting that the nanohybrid might be useful in developing an electronic nose. The dynamic range of the saccharin sensor is 20 - 300μM. In this paper we present our results on sensor fabrication and testing and discuss possible sensing mechanisms. In addition, we describe our work on immobilizing in the nanohybrid membranes Glucose Oxidase, Horseradish Peroxidase and Gramicidin and evaluating their performance.
Interfacial Adhesion of Pure-Silica-Zeolite Low-k Thin Films
Authors: Hu Lili , Wang Junlan , Li Zijian , Li Shuang , Yan Yushan 
Published: June 2019

AbstractNanoporous zeolite thin films are promising candidates as future low dielectric constant (low-k) materials. During the integration process with other semiconductor materials, the residual stresses resulting from the synthesis processes may cause fracture or delamination of the thin films. In order to achieve high quality low-k zeolite thin films, the evaluation of the adhesion performance is important. In this paper, laser spallation technique is utilized to investigate the interfacial adhesion of zeolite thin film-Si substrate interfaces prepared using three different processes. The experimental results demonstrate that the nature of the deposition method has a great effect on the resulted interfacial adhesion of the film-substrate interfaces. This is the first time that the interfacial strength of zeolite thin films-Si substrates is quantitatively evaluated. The results have great significance in the future applications of low-k zeolite thin film materials.
Experimental and Theoretical Investigations of the Magnetic Phases of Epitaxially Grown EuSe at Low Fields and Temperatures
Authors: Rumpf K. , Granitzer P. , Krenn H. 
Published: June 2019

AbstractDue to its metamagnetic behaviour the magnetic phases of EuSe are more complicated than for the other Eu-chalcogenides, e.g. EuTe. At very low temperatures (below 2K) there occurs an additional antiferromagnetic phase. This behaviour cannot be solely explained by exchange interaction of nearest neighbors and next nearest neighbors but requires more information about the NNSSNN, NSNS and NNSNNS spin arrangements. Because the nearest and next nearest neighbour exchange constants are nearly cancelled out, higher order interaction becomes important and the biquadratic exchange has also to be taken into account. Our measurements were carried out on an epitaxial grown 2.5 micrometers EuSe film on BaF2. Three regions predicted in the phase diagram of a EuSe bulk crystal are of special interest. For low temperatures (below 1.8K) and low magnetic fields (below 0.05T) a NSNS antiferromagnetic (type II) phase occurs. For higher temperatures from 1.8K to 4.6K and B = 0.1T to 2.5T a NNSNNS ferrimagnetic order exists whereas for lower magnetic fields a further antiferromagnetic (type I) NNSSNNSS-phase is formed above a temperature of 3.6-3.7K. The experimental data show that bilinear mean field calculations taking into account only nearest (JNN) and next nearest exchange (JNNN) interaction fail on this system. Therefore biquadratic exchange (K) has to be included. We present a 12x12 matrix MFA-formalism to extract the proper exchange parameters, which deviate slightly from the bilinear MFA-approach: JNN = 0.165 K, JNNN = -0.1209 K. The biquadratic exchange constant is taken as K = -0.0458 K. We prove this theoretical implication by testing Arrott plots for a varying slope. We made a fit to the experimental data even beyond MFA by taking the corresponding critical exponents of the Heisenberg model.