bluuebunny/crossref_metadata_2025_split huggingface dataset:
Electroforming of Fe:STO samples for resistive switching made visible by electrocoloration observed by high resolution optical microscopy
Authors: Havel Viktor , Marchewka Astrid , Menzel Stephan , Hoffmann-Eifert Susanne , Roth Georg , Waser Rainer 
Published: June 2014

ABSTRACTResistively switching devices have attracted great attention for potential use in future nonvolatile information storage. Among various oxide materials that show resistive switching (RS) behavior, SrTiO3 (STO) is regarded as a model material to study the effect of valence changes accompanying RS in the oxide [1]. In this class of materials, the RS effect is attributed to rely on the migration of oxygen vacancies and an associated valence change in the cation sublattice. To achieve a switchable state, an initial electroforming step is typically required, which is believed to create conductive regions in the insulating material [2]. Under high electrical stress, an oxygen-deficient region, often referred to as the virtual cathode (VC), is formed [3]. The RS occurs across a very short distance between the VC and the anode, allowing for very short switching times. As the electroforming step greatly impacts the device performance and switching variability, its understanding is essential for device optimization. Electroforming is affected by multiple parameters, e.g. voltage, current, temperature, dopant and defect concentrations, ambient gas atmosphere and time. Distinguishing the influence of the particular parameters is a desirable aim and challenging task. Electrocoloration of Fe-doped STO single crystals has proven a valuable means to visualize valence changes of the Fe ions and is thus suitable to study the formation of the VC. Therefore, we performed electrocoloration experiments and used high resolution transmission light optical microscopy to make the redoxprocesses during electroforming visible. The influence of process driving parameters on the evolution of the VC region is studied. The evolution of the VC is interpreted by drift-diffusion simulation of the time evolution of the oxygen vacancy distribution.
Structural Characterization of Lateral-grown 6H-SiC a/m-plane Seed Crystals by Hot Wall CVD Epitaxy
Authors: Goue Ouloide Yannick , Raghothamachar Balaji , Dudley Michael , Trunek Andrew J. , Neudeck Philip G. , Woodworth Andrew A. , Spry David J. 
Published: June 2014

ABSTRACTThe performance of commercially available silicon carbide (SiC) power devices is limited due to inherently high density of screw dislocations (SD), which are necessary for maintaining polytype during boule growth and commercially viable growth rates. The NASA Glenn Research Center (GRC) has recently proposed a new bulk growth process based on axial fiber growth (parallel to the c-axis) followed by lateral expansion (perpendicular to the c-axis) for producing multi-faceted m-plane SiC boules that can potentially produce wafers with as few as one SD per wafer. In order to implement this novel growth technique, the lateral homoepitaxial growth expansion of a SiC fiber without introducing a significant number of additional defects is critical. Lateral expansion is being investigated by hot wall chemical vapor deposition (HWCVD) growth of 6H-SiC a/m-plane seed crystals (0.8mm x 0.5mm x 15mm) designed to replicate axially grown SiC single crystal fibers. The post-growth crystals exhibit hexagonal morphology with approximately 1500 μm (1.5 mm) of total lateral expansion. Preliminary analysis by synchrotron white beam x-ray topography (SWBXT) confirms that the growth was homoepitaxial, matching the polytype of the respective underlying region of the seed crystal. Axial and transverse sections from the as-grown crystal samples were characterized in detail by a combination of SWBXT, transmission electron microscopy (TEM) and Raman spectroscopy to map defect types and distribution. X-ray diffraction analysis indicates the seed crystal contained stacking disorders and this appears to have been reproduced in the lateral growth sections. Analysis of the relative intensity for folded transverse acoustic (FTA) and optical (FTO) modes on the Raman spectra indicate the existence of stacking faults (SFs). Further, the density of stacking faults is higher in the seed than in the grown crystal. Bundles of dislocations are observed propagating from the seed in m-axis lateral directions. Contrast extinction analysis of these dislocation lines reveals they are edge type basal plane dislocations that track the growth direction. Polytype phase transition and stacking faults were observed by high-resolution TEM (HRTEM), in agreement with SWBXT and Raman scattering.
4H-SiC P+N UV Photodiodes: Influence of Temperature and Irradiation
Authors: Bérenguier B. , Ottaviani L. , Biondo S. , Palais O. , Lazar M. , Milesi F. , Torregrosa F. , Kalinina E. , Lebedev A. , Vervisch W. , Lyoussi A. 
Published: June 2014

ABSTRACT4H-SiC p+n photodiodes based on ultrathin-junctions have been fabricated with distinct processes for the p+-region creation: either with Aluminium conventional ion implantation, or with Boron Plasma Ion Immersion Implantation. Spectral sensitivity measurements were performed at several temperatures from room temperature up to 340°C, with incident wavelengths ranging from 200 to 400 nm. Both responses are characterized by a stability between 200 and 270 nm, and a important increase with temperature between 270 and 380 nm. This fact has to be related to the two different kinds of optical absorption phenomena in SiC with respect to the wavelength, which are direct and indirect (phonon assisted) transitions. When decreasing the temperature, we noticed a hysteresis effect, which could be due to charge trapping by temperature activated defects. After strong proton and electron irradiations, the diodes showed a stability of the response below 270 nm, making them suitable for use in harsh environments. Simulation was performed at room temperature, with a good correlation between simulated and experimental room temperature curves.
3C-SiC on Si: A Versatile Material for Electronic, Biomedical and Clean Energy Applications
Authors: Frewin C.L , Reyes M. , Register J. , Thomas S. W. , Saddow S. E. 
Published: June 2014

AbstractSilicon carbide (SiC) has long been known as a robust semiconductor with superior properties to silicon for electronic applications. Consequently a tremendous amount of international activity has been on-going for over four decades to develop high-power solid state SiC electronics. While this activity has focused on the hexagonal polytypes of SiC, the only form that can be grown directly on Si substrates, 3C-SiC (or cubic SiC), has been researched for non-electronic applications such as MEMS and biosensors. In particular in our group we have pioneered several biomedical devices using 3C-SiC grown on Si substrates, and recently have been investigating the use of this novel material for clean energy applications. This paper first reviews progress made in the area of 3C-SiC electronic devices. Next a review of nearly a decade of biomedical activity is presented, with particular emphasis on the most promising applications: in vivo glucose monitoring, biomedical implants for connecting the human nervous system to advanced prosthetics, and MEMS/NEMS research aimed at allowing for in vivo diagnostic and therapeutic systems for advanced biomedical applications. Recent published work in the area of hydrogen production via electrolysis using 3C-SiC closes the paper as this last application is extremely promising for the burgeoning hydrogen economy and demonstrates a third important application of 3C-SiC on Si – its potential use in clean energy systems.
Impact of growth parameters on the formation of carbon nanostructures through thermal deposition of silicon carbide
Authors: Anderson Munson , Pochet Michael , Maruyama Benji , Nikolaev Pavel , Moore Elizabeth , Boeckl John 
Published: June 2014

ABSTRACTCarbon nanotube (CNT) and graphene films form on silicon carbon (SiC) using a metal-catalyst-free thermal decomposition approach. In this work, the growth conditions used in the decomposition process are varied to investigate their impact on the type and quality of carbon allotrope formed on the SiC substrate. The nanostructure growth is performed using two approaches, both of which involve intense heating (1250-1700oC) under moderate vacuum conditions (10-2 – 10-5 Torr) without the aid of carbon rich feed gases or metal catalysts commonly used in Chemical Vapor Deposition (CVD) growth approaches. The first growth method uses a graphite resistance furnace capable of annealing wafer-sized samples. The second approach uses a high-intensity laser to heat a micro-meter scale spot size. The high-intensity laser heats the illuminated area of the SiC substrate while under vacuum conditions, resulting in a small-scale growth process similar to the conventional resistance furnace technique. Unique to this micro-scale approach is that in situ Raman spectroscopy is performed yielding instantaneous characterization of the resultant carbon nanostructure as it is formed. The laser-induced growth mechanism enables the impact of varied background vacuum pressures and temperatures to be evaluated in situ. This work reports the findings for various parameter sets implemented during growth, and provides insight into the physical mechanism influencing the growth process.
Home VLC using pinpin a-SiC:H multilayer devices
Authors: Louro P. , Silva V. , Rodrigues I. , Vieira M. A. , Vieira M. 
Published: June 2014

ABSTRACTIn this paper an integrated wavelength optical filter and photodetector for Visible Light Communication (VLC) is used. The proposed application uses indoor warm light lamps lighting accomplished by ultra-bright light-emitting diodes (LEDs) pulsed at frequencies higher than the ones perceived by the human eye. The system was analyzed at two different wavelengths in the visible spectrum, one in the blue (430 nm) and the other in the red (626 nm) regions, driven at different currents in order to change their optical intensities. The signals were transmitted into free space and measured using a pin-pin photodetector based on a-SiC:H/a-Si:H. This detector behaves as an optical filter with controlled wavelength sensitivity through the use of adequate optical biasing light. The output photocurrent was measured for different optical intensities of the transmitted optical signal and the extent of each signal was tested. An electrical model was used to support the physical operation of the device.
Novel SiC detector based on optical signal instead of electrical signal
Authors: Lim Geunsik , Manzur Tariq , Kar Aravinda 
Published: June 2014

ABSTRACTA novel SiC optical detector that produces optical signal in contrast to the electric signal generated by conventional electrical detectors. The optical detector is a remote sensor providing response to incident photons from a distant object. The incident photons modify the refractive index and, consequently, the reflectance of the doped SiC by altering the electron densities in the valence band and the acceptor energy levels. This variation in the refractive index or reflectance represents the optical signal as the sensor response, which can be determined with a probe laser such as a He-Ne laser or a light-emitting diode. The sensor can be applied to numerous remote sensing applications including high-temperature or harsh environments due to the optical read-out of the detector response with a probe laser. The effects of different dopants on the detector response for sensing different chemical species, or equivalently imaging in different MWIR wavelengths, have been studied and the dopant concentration has been found to affect the optical signal. These results indicate that a new class of SiC detectorsclassified as optical detectors can be produced for a variety of wavelengths using different dopants for numerous applications.
Degradation of electrical properties of small molecule organic solar cells under oxygen and moisture
Authors: Ciammaruchi Laura , Carlo Aldo Di , Tang Ching W. 
Published: June 2014

ABSTRACTWe investigated the photovoltaic (PV) parameters of a planar hetero-junction solar cell with di-[4-(N,Nditolyl-amino)-phenyl] cyclohexane (TAPC) as donor (D) and C60 as acceptor (A), upon exposing the acceptor side to oxygen and moisture. We found that for the same time of exposure, even minor oxygen amounts lead to more detrimental results compared to moisture. We argue that the photo-conversion efficiency (PCE) decreases due to creation of recombination centers at the interface, which induce losses in exciton diffusion and charge generation. Under the same conditions, we also registered a direct connection between the cell PV parameters’ decay and a C60 thin-film conductivity loss.
Modeling, Simulation, and Optimal Control of Oil Production under Gas Coning Conditions
Authors: Hasan Agus , Foss Bjarne , Sagatun Svein Ivar , Tjøstheim Bjørn Peter , Svandal Atle , Hatland Cato 
Published: June 2014

Abstract
Gas coning is a tendency of the gas to impel the oil downward in an inverse cone contour toward the well perforations. Once the gas reaches the well, gas production will dominate the well flow and the oil production will hence significantly decrease. From an economical and operational standpoint this condition is undesirable since the gas price is much lower than the oil price, and the gas handling capacity often is a constraint. Therefore, there is an incentive to maximize oil production up until gas breakthrough. In this paper, the gas coning process in a gas oil reservoir completed with a single horizontal well is analytically modeled, simulated, and analyzed applying a nonlinear control approach. The model which describes the interaction between the well and the reservoir may be cast into a boundary control problem of the porous media equation with two boundary conditions; a Neumann boundary condition describing no flow at the outer boundary of the reservoir, and a nonlinear boundary condition describing the well production rate. A well rate controller for the boundary control problem is designed using the Lyapunov method. The controller holds some formal performance guarantees and requires information on the gas oil contact at the well heel only. Further, the controller has a tuning parameter which can be used to maximize a suitable performance measure. The controller is evaluated using a detailed ECLIPSE simulator of a gas coning reservoir. Simulation results show significant improvement of production profit of the proposed method compared to a conventional method which usually uses a constant rate up until gas breakthrough.
Flow Induced Inline Separation (FIIS) De-watering Tests at the Gullfaks Field
Authors: Bjørkhaug M. , Johannesen B. , Eidsmo G. S. 
Published: June 2014

Abstract
Several fields on the Norwegian Continental Shelf have reached the decline phase with an increasing production of water and gas, often in combination with reduction in reservoir pressure. The available space and weight allowance for installation of new equipment on the platforms is often limited, and it is important to minimize both the operational and capital costs. Compact, inline separation equipment can be a key technology for mature fields, and also for subsea fields at large water depths where the weight is critical during the installation phase.
The Statoil operated Gullfaks license has identified Flow Induced Inline Separation (FIIS) as a key technology in order to increase the oil recovery. Due to low foot print, low hydrocarbon inventory and reduced need for flare capacity, the resulting reduced operating cost of the technology, can aid prolonged production from the reservoir. The technology will also provide free space and weight allowances for future tiebacks to Gullfaks. A survey identified a need for both compact gas-liquid as well as compact oil-water separation. Statoil have chosen to develop and test relevant units in close co-operation with vendors of compact separation equipment. All the tested technologies are based on cyclonic separation equipments with low or moderate pressure drops.
Statoil is carrying out an extensive qualification program where compact oil-water separators from FMC Technology and Caltec are developed and tested at real operating conditions. Individual unit tests (25 Am3/h, 3770 bpd liquid) have been performed in high pressure laboratory flow loops and in a test rig on the Gullfaks C production platform located in the North Sea. The aim is to remove at least 60 % of the incoming water phase with a water quality acceptable to the downstream produced water system. The operational window of the tested cyclonic technologies is wide for both vendors. The effect of gas content, water cut, droplet size, operating pressure and water removal on the outlet water quality will be described in the paper.
The conclusion from the work is that the potential of compact oil-water separation is large and possible applications will be discussed in the paper.
Geometric Analysis of Progressive Cavity Pump Single Lobe, for the Production of Extra-Crude Heavy Oil at Huyaparí Oil Field at Orinoco Oil Belt Venezuela
Authors: Arredondo Manuel , Cermeño Leonardo , Quijada Efren 
Published: June 2014

Abstract
Since its appearance in May 1930, the progressive cavity pump is being increasingly used in oil production, mainly at heavy oil fields with numerous of application advantages. In the design and selection of progressive cavity pumps (PCP) and extra heavy crude oil, it is usually assessed the type of elastomer used, the displacement capability and the lifting of the pump, leaving out important variables to consider.
A very important point to highlight between two pump models that have similar in uprisings capabilities and geometry, which influence on parameters that affect the volumetric efficiency, the type of fluid to be pumped, capacity and solids handling, speed of operation and service life, among others.
Depending on the application some pumps will be more appropriate than others, it would depend on the geometric design, which affects the performance of the pump operating conditions. For example, without taking care of the elastomer type or the lifting value, two pumps 80 m3/D/100RPM of different geometry, have different efficiencies working with the same fluid. It is Possible that one of them required a higher speed of operation that the other, this one would be more susceptible to solids, and the pump would fail sooner. It could show some remarkable differences on their service-life that means that one of them could have a run-time longer than other.
This document presents the geometric analysis performed at progressive cavity pumps used successfully at the Huyaparí field at the Orinoco Oil Belt Venezuela. Based on field experience, actual data geometries from different suppliers, it is presented a characterization of the geometric variables that must have an efficient BCP at Huyaparí field and it could be extrapolated to some oil fields that have similar characterization of fluid and operation. This study is focused on the geometric analysis, thus excluding elastomers or assessment survey and focus required in the successful operations of a specific field.
Cost Reduction in High Production Wells with ESP in Tello Field
Authors: Archila Jesus , Rueda Julio Mario , Garces Carlos , Carreño Oscar 
Published: June 2014

Abstract
This article describes the implementation of a better performance of the ESP equipment to improve and maintain production in Tello field, focus on one of the most important root cause of failure in the Tello field that was "well geometry" referring to collapsing and no uniforms 7" and 9-5/8" casings new technology, reducing costs with a better down hole installation velocity, eliminating the stuck risk, and less failure services.
With efficient solutions of the problem using ESP slim application with high load shaft thru a significant difference of diameter on a big range of flow rate was reduce the probability of a MLE damage and scratch the equipment with the casing, as well the MWI (measure while installing) it’s been implemented on each service to eliminate the verification of electrical continuity in ESP installations.
Assessing Risks and Regulating Safety Standards in the Oil and Gas Industry: The Peruvian Experience
Authors: Cordano A. L.Vásquez , Jácome J. Salvador , Carpio R.García. García , Guzmán V. Fernández 
Published: June 2014

Abstract*
Environmental regulation has usually focused on continuous sources of pollution like CO2 emissions through carbon taxes. However, the recent oil spill in the Gulf of Mexico has shown that accidents associated to safety failures can also generate bursts of pollution with serious environmental consequences. Regulating safety conditions to prevent accidents in the oil and gas industry is challenging because public regulators cannot perfectly observe whether firms comply with safety laws. Likewise, it involves a complex political process in which different agents such as the government and oil companies interact and compete. This paper studies this problem in the case of Peru, providing a framework to analyze the enforcement of regulations designed to control safety standards in the oil and gas industry.
Regulating oil accidents demands a holistic approach, for the paper discusses different contributions from economics and game theory to understand the safety regulatory framework of Peru representing the interactions among the government, oil companies, and public regulators. It characterizes the optimal enforcement strategy to prevent safety law violations causing accidents. Policy instruments such as self-reporting, monitoring and economic incentives are also analyzed considering the Peruvian experience.
It is possible to represent using a simple decision framework the complex institutional system governing environmental regulations in Peru. Economic motives in an uncertain business environment drive law infringing behavior that leads to safety violations, so the government finds optimal to apply a law enforcement strategy that attacks these incentives. Oil companies may find beneficial to comply with safety standards to minimize private losses associated to large accidents involving oil spills, gas pipelines leakages, etc.
Understanding how to properly regulate the occurrence of oil and gas accidents is fundamental for the legitimacy of the oil industry and governments’ stability in a context where citizens demand improvements in safety standards and environmental quality. The analysis provided here can help oil firms and regulators in Peru and other jurisdictions assess the risks involved in oil and gas operations and the optimal ways to diminish them by considering appropriate regulations that balance the interests of companies and the governments’ objective of protecting the environment and human health.