Asymmetric injection and distribution of space charges in propylene carbonate under impulse voltage

NASA Astrophysics Data System (ADS)

Sima, Wenxia; Chen, Qiulin; Sun, Potao; Yang, Ming; Guo, Hongda; Ye, Lian

2018-05-01

Space charge can distort the electric field in high voltage stressed liquid dielectrics and lead to breakdown. Observing the evolution of space charge in real time and determining the influencing factors are of considerable significance. The spatio-temporal evolution of space charge in propylene carbonate, which is very complex under impulse voltage, was measured in this study through the time-continuous Kerr electro-optic field mapping measurement. We found that the injection charge from a brass electrode displayed an asymmetric effect; that is, the negative charge injection near the cathode lags behind the positive charge injection near the anode. Physical mechanisms, including charge generation and drift, are analyzed, and a voltage-dependent saturated drift rectification model was established to explain the interesting phenomena. Mutual validation of models and our measurement data indicated that a barrier layer, which is similar to metal-semiconductor contact, was formed in the contact interface between the electrode and propylene carbonate and played an important role in the space charge injection.

Charge injection and transport in a single organic monolayer island

NASA Astrophysics Data System (ADS)

Vuillaume, Dominique

2005-03-01

We report how electrons and holes, that are locally injected in a single organic monolayer island (where organic monolayers are made from sublimated oligomers (pentacene and other oligoacenes), or made from chemisorption in solution (self-assembled monolayers) of pi-conjugated moieties), stay localized or are able to delocalize over the island as a function of the molecular conformation (order vs. disorder) of this island. Charge carriers were locally injected by the apex of an atomic force microscope tip, and the resulting two-dimensional distribution and concentration of injected charges were measured by electrical force microscopy (EFM) experiments. We show that in crystalline monolayer islands, both electrons and holes can be equally injected, at a similar charge concentration for symmetric injection bias conditions, and that both charge carriers are delocalized over the whole island. On the contrary, charges injected into a more disordered monolayer stay localized at their injection point. These different results are discussed in relation with the electrical performances of molecular devices made from these monolayers (OFET, SAMFET). These results provide insight into the electronic properties, at the nanometer scale, of these molecular devices.

Methodology for extraction of space charge density profiles at nanoscale from Kelvin probe force microscopy measurements.

PubMed

Villeneuve-Faure, C; Boudou, L; Makasheva, K; Teyssedre, G

2017-12-15

To understand the physical phenomena occurring at metal/dielectric interfaces, determination of the charge density profile at nanoscale is crucial. To deal with this issue, charges were injected applying a DC voltage on lateral Al-electrodes embedded in a SiN x thin dielectric layer. The surface potential induced by the injected charges was probed by Kelvin probe force microscopy (KPFM). It was found that the KPFM frequency mode is a better adapted method to probe accurately the charge profile. To extract the charge density profile from the surface potential two numerical approaches based on the solution to Poisson's equation for electrostatics were investigated: the second derivative model method, already reported in the literature, and a new 2D method based on the finite element method (FEM). Results highlight that the FEM is more robust to noise or artifacts in the case of a non-flat initial surface potential. Moreover, according to theoretical study the FEM appears to be a good candidate for determining charge density in dielectric films with thicknesses in the range from 10 nm to 10 μm. By applying this method, the charge density profile was determined at nanoscale, highlighting that the charge cloud remains close to the interface.

Methodology for extraction of space charge density profiles at nanoscale from Kelvin probe force microscopy measurements

NASA Astrophysics Data System (ADS)

Villeneuve-Faure, C.; Boudou, L.; Makasheva, K.; Teyssedre, G.

2017-12-01

To understand the physical phenomena occurring at metal/dielectric interfaces, determination of the charge density profile at nanoscale is crucial. To deal with this issue, charges were injected applying a DC voltage on lateral Al-electrodes embedded in a SiN x thin dielectric layer. The surface potential induced by the injected charges was probed by Kelvin probe force microscopy (KPFM). It was found that the KPFM frequency mode is a better adapted method to probe accurately the charge profile. To extract the charge density profile from the surface potential two numerical approaches based on the solution to Poisson’s equation for electrostatics were investigated: the second derivative model method, already reported in the literature, and a new 2D method based on the finite element method (FEM). Results highlight that the FEM is more robust to noise or artifacts in the case of a non-flat initial surface potential. Moreover, according to theoretical study the FEM appears to be a good candidate for determining charge density in dielectric films with thicknesses in the range from 10 nm to 10 μm. By applying this method, the charge density profile was determined at nanoscale, highlighting that the charge cloud remains close to the interface.

Exciton dynamics of C60-based single-photon emitters explored by Hanbury Brown-Twiss scanning tunnelling microscopy.

PubMed

Merino, P; Große, C; Rosławska, A; Kuhnke, K; Kern, K

2015-09-29

Exciton creation and annihilation by charges are crucial processes for technologies relying on charge-exciton-photon conversion. Improvement of organic light sources or dye-sensitized solar cells requires methods to address exciton dynamics at the molecular scale. Near-field techniques have been instrumental for this purpose; however, characterizing exciton recombination with molecular resolution remained a challenge. Here, we study exciton dynamics by using scanning tunnelling microscopy to inject current with sub-molecular precision and Hanbury Brown-Twiss interferometry to measure photon correlations in the far-field electroluminescence. Controlled injection allows us to generate excitons in solid C60 and let them interact with charges during their lifetime. We demonstrate electrically driven single-photon emission from localized structural defects and determine exciton lifetimes in the picosecond range. Monitoring lifetime shortening and luminescence saturation for increasing carrier injection rates provides access to charge-exciton annihilation dynamics. Our approach introduces a unique way to study single quasi-particle dynamics on the ultimate molecular scale.

DNA Bases Thymine and Adenine in Bio-Organic Light Emitting Diodes

DTIC Science & Technology

2014-11-24

Interestingly, the T-based OLED results resemble the charge trapping effect of nanoparticles in the PEDOT layer of a phosphorescent OLED30 that...Mater. Chem. 21, 1350–1361, doi:10.1039/c0jm02444a (2011). 3. Lee, J. et al. DNA-base guanine as hydrogen getter and charge trapping layer embedded in...nm also decreased performance, as a surplus of holes can be injected creating a charge imbalance and a reduction in current emission efficiency. The

Study of charge transport in composite blend of P3HT and PCBM

NASA Astrophysics Data System (ADS)

Kumar, Manoj; Kumar, Sunil; Upadhyaya, Aditi; Yadav, Anjali; Gupta, Saral K.; Singh, Amarjeet

2018-05-01

Poly (3-hexylthiophene-2,5diyl) (P3HT) as donor and [6,6]-phenyl C61 butyric acid methyl ester (PCBM) as acceptor are mostly used as active medium in polymeric electronic device. In this paper we have prepare the P3HT - PCBM based bulk hetero junction thin films by spin coating technique. The charge transport properties of P3HT:PCBM blends are investigated by the current-voltage measurements using Ag as an electron injecting electrode and ITO as a hole injecting contact. The current density v/s voltage relationships are analyzed in the backdrop of Schottky and Space charge limited current model.

Diesel engine emissions reduction by multiple injections having increasing pressure

DOEpatents

Reitz, Rolf D.; Thiel, Matthew P.

2003-01-01

Multiple fuel charges are injected into a diesel engine combustion chamber during a combustion cycle, and each charge after the first has successively greater injection pressure (a higher injection rate) than the prior charge. This injection scheme results in reduced emissions, particularly particulate emissions, and can be implemented by modifying existing injection system hardware. Further enhancements in emissions reduction and engine performance can be obtained by using known measures in conjunction with the invention, such as Exhaust Gas Recirculation (EGR).

A comprehensive study of charge trapping in organic field-effect devices with promising semiconductors and different contact metals by displacement current measurements

NASA Astrophysics Data System (ADS)

Bisoyi, Sibani; Rödel, Reinhold; Zschieschang, Ute; Kang, Myeong Jin; Takimiya, Kazuo; Klauk, Hagen; Tiwari, Shree Prakash

2016-02-01

A systematic and comprehensive study on the charge-carrier injection and trapping behavior was performed using displacement current measurements in long-channel capacitors based on four promising small-molecule organic semiconductors (pentacene, DNTT, C10-DNTT and DPh-DNTT). In thin-film transistors, these semiconductors showed charge-carrier mobilities ranging from 1.0 to 7.8 cm2 V-1 s-1. The number of charges injected into and extracted from the semiconductor and the density of charges trapped in the device during each measurement were calculated from the displacement current characteristics and it was found that the density of trapped charges is very similar in all devices and of the order 1012 cm-2, despite the fact that the four semiconductors show significantly different charge-carrier mobilities. The choice of the contact metal (Au, Ag, Cu, Pd) was also found to have no significant effect on the trapping behavior.

Unexpected significant increase in bulk conductivity of a dielectric arising from charge injection

NASA Astrophysics Data System (ADS)

Wang, Jian-Jun; Bayer, Thorsten J. M.; Wang, Rui; Carter, Jared J.; Randall, Clive A.; Chen, Long-Qing

2017-06-01

Charge injection is a common phenomenon in heterostructures or devices containing metal-insulator interfaces under a voltage bias ranging from dielectric capacitors to electroluminescent and lasing devices. It is generally believed that charge injection only significantly increases the conductivity near the interfacial region or in capacitors with very thin dielectric layers. In this work, the impact of charge injection on bulk conductivity of a 0.5 mm thick Fe-doped SrTiO3 single crystal is investigated with a combination of experimental impedance measurements and computational modelling. It is found that the interfacial charge injection may increase the predicted bulk conductivity of a dielectric by more than one order of magnitude as a consequence of Schottky barrier height lowering.

Effects of low charge injection densities on corrosion responses of pulsed 316LVM stainless steel electrodes.

PubMed

Riedy, L W; Walter, J S

1996-06-01

The safe charge injection density for pulsing of 316LVM electrodes has been reported to be 40 microC/cm2. However, only 20 microC/cm2 is available for nonfaradic charge transfer and double layer charge injection. Therefore, we evaluated long term pulsing at 20 microC/cm2 with capacitor coupling.

Modulating the fixed charge density in silicon nitride films while monitoring the surface recombination velocity by photoluminescence imaging

NASA Astrophysics Data System (ADS)

Bazilchuk, Molly; Haug, Halvard; Marstein, Erik Stensrud

2015-04-01

Several important semiconductor devices such as solar cells and photodetectors may be fabricated based on surface inversion layer junctions induced by fixed charge in a dielectric layer. Inversion layer junctions can easily be fabricated by depositing layers with a high density of fixed charge on a semiconducting substrate. Increasing the fixed charge improves such devices; for instance, the efficiency of a solar cell can be substantially increased by reducing the surface recombination velocity, which is a function of the fixed charge density. Methods for increasing the charge density are therefore of interest. In this work, the fixed charge density in silicon nitride layers deposited by plasma enhanced chemical vapor deposition is increased to very high values above 1 × 1013 cm-2 after the application of an external voltage to a gate electrode. The effect of the fixed charge density on the surface recombination velocity was experimentally observed using the combination of capacitance-voltage characterization and photoluminescence imaging, showing a significant reduction in the surface recombination velocity for increasing charge density. The surface recombination velocity vs. charge density data was analyzed using a numerical device model, which indicated the presence of a sub-surface damage region formed during deposition of the layers. Finally, we have demonstrated that the aluminum electrodes used for charge injection may be chemically removed in phosphoric acid without loss of the underlying charge. The injected charge was shown to be stable for a prolonged time period, leading us to propose charge injection in silicon nitride films by application of soaking voltage as a viable method for fabricating inversion layer devices.

Stackable differential mobility analyzer for aerosol measurement

DOEpatents

Cheng, Meng-Dawn [Oak Ridge, TN; Chen, Da-Ren [Creve Coeur, MO

2007-05-08

A multi-stage differential mobility analyzer (MDMA) for aerosol measurements includes a first electrode or grid including at least one inlet or injection slit for receiving an aerosol including charged particles for analysis. A second electrode or grid is spaced apart from the first electrode. The second electrode has at least one sampling outlet disposed at a plurality different distances along its length. A volume between the first and the second electrode or grid between the inlet or injection slit and a distal one of the plurality of sampling outlets forms a classifying region, the first and second electrodes for charging to suitable potentials to create an electric field within the classifying region. At least one inlet or injection slit in the second electrode receives a sheath gas flow into an upstream end of the classifying region, wherein each sampling outlet functions as an independent DMA stage and classifies different size ranges of charged particles based on electric mobility simultaneously.

Investigation of charge injection and transport behavior in multilayer structure consisted of ferromagnetic metal and organic polymer under external fields

NASA Astrophysics Data System (ADS)

Zhao, Hua; Meng, Wei-Feng

2017-10-01

In this paper a five layer organic electronic device with alternately placed ferromagnetic metals and organic polymers: ferromagnetic metal/organic layer/ferromagnetic metal/organic layer/ferromagnetic metal, which is injected a spin-polarized electron from outsides, is studied theoretically using one-dimensional tight binding model Hamiltonian. We calculated equilibrium state behavior after an electron with spin is injected into the organic layer of this structure, charge density distribution and spin polarization density distribution of this injected spin-polarized electron, and mainly studied possible transport behavior of the injected spin polarized electron in this multilayer structure under different external electric fields. We analyze the physical process of the injected electron in this multilayer system. It is found by our calculation that the injected spin polarized electron exists as an electron-polaron state with spin polarization in the organic layer and it can pass through the middle ferromagnetic layer from the right-hand organic layer to the left-hand organic layer by the action of increasing external electric fields, which indicates that this structure may be used as a possible spin-polarized charge electronic device and also may provide a theoretical base for the organic electronic devices and it is also found that in the boundaries between the ferromagnetic layer and the organic layer there exist induced interface local dipoles due to the external electric fields.

Modulating the line shape of magnetoconductance by varying the charge injection in polymer light-emitting diodes

NASA Astrophysics Data System (ADS)

Chitraningrum, Nidya; Chu, Ting-Yi; Huang, Ping-Tsung; Wen, Ten-Chin; Guo, Tzung-Fang

2018-02-01

We fabricate the phenyl-substituted poly(p-phenylene vinylene) copolymer (super yellow, SY-PPV)-based polymer light-emitting diodes (PLEDs) with different device architectures to modulate the injection of opposite charge carriers and investigate the corresponding magnetoconductance (MC) responses. At the first glance, we find that all PLEDs exhibit the positive MC responses. By applying the mathematical analysis to fit the curves with two empirical equations of a non-Lorentzian and a Lorentzian function, we are able to extract the hidden negative MC component from the positive MC curve. We attribute the growth of the negative MC component to the reduced interaction of the triplet excitons with charges to generate the free charge carriers as modulated by the applied magnetic field, known as the triplet exciton-charge reaction, by analyzing MC responses for PLEDs of the charge-unbalanced and hole-blocking device configurations. The negative MC component causes the broadening of the line shape in MC curves.

Evaluation of Intrinsic Charge Carrier Transport at Insulator-Semiconductor Interfaces Probed by a Non-Contact Microwave-Based Technique

PubMed Central

Honsho, Yoshihito; Miyakai, Tomoyo; Sakurai, Tsuneaki; Saeki, Akinori; Seki, Shu

2013-01-01

We have successfully designed the geometry of the microwave cavity and the thin metal electrode, achieving resonance of the microwave cavity with the metal-insulator-semiconductor (MIS) device structure. This very simple MIS device operates in the cavity, where charge carriers are injected quantitatively by an applied bias at the insulator-semiconductor interface. The local motion of the charge carriers was clearly probed through the applied external microwave field, also giving the quantitative responses to the injected charge carrier density and charge/discharge characteristics. By means of the present measurement system named field-induced time-resolved microwave conductivity (FI-TRMC), the pentacene thin film in the MIS device allowed the evaluation of the hole and electron mobility at the insulator-semiconductor interface of 6.3 and 0.34 cm2 V−1 s−1, respectively. This is the first report on the direct, intrinsic, non-contact measurement of charge carrier mobility at interfaces that has been fully experimentally verified. PMID:24212382

Analysis of pulsed injection for microgravity receiver tank chilldown

NASA Astrophysics Data System (ADS)

Honkonen, Scott C.; Pietrzyk, Joe R.; Schuster, John R.

The dominant heat transfer mechanism during the hold phase of a tank chilldown cycle in a low-gravity environment is due to fluid motion persistence following the charge. As compared to the single-charge per vent cycle case, pulsed injection maintains fluid motion and the associated high wall heat transfer coefficients during the hold phase. As a result, the pulsed injection procedure appears to be an attractive method for reducing the time and liquid mass required to chill a tank. However, for the representative conditions considered, no significant benefit can be realized by using pulsed injection as compared to the single-charge case. A numerical model of the charge/hold/vent process was used to evaluate the pulsed injection procedure for tank chilldown in microgravity. Pulsed injection results in higher average wall heat transfer coefficients during the hold, as compared to the single-charge case. However, these high levels were not coincident with the maximum wall-to-fluid temperature differences, as in the single-charge case. For representative conditions investigated, the charge/hold/vent process is very efficient. A slightly shorter chilldown time was realized by increasing the number of pulses.

New diesel injection nozzle flow measuring device

NASA Astrophysics Data System (ADS)

Marčič, Milan

2000-04-01

A new measuring device has been developed for diesel injection nozzle testing, allowing measuring of the steady flow through injection nozzle and the injection rate. It can be best applied for measuring the low and high injection rates of the pintle and single hole nozzle. In steady flow measuring the fuel pressure at the inlet of the injection nozzle is 400 bar. The sensor of the measuring device measures the fuel charge, resulting from fuel rubbing in the fuel injection system, as well as from the temperature gradient in the sensor electrode. The electric charge is led to the charge amplifier, where it is converted into electric current and amplified. The amplifier can be used also to measure the mean injection rate value.

Over-injection and self-oscillations in an electron vacuum diode

NASA Astrophysics Data System (ADS)

Leopold, J. G.; Siman-Tov, M.; Goldman, A.; Krasik, Ya. E.

2017-07-01

We demonstrate a practical means by which one can inject more than the space-charge limiting current into a vacuum diode. This over-injection causes self-oscillations of the space-charge resulting in an electron beam current modulation at a fixed frequency, a reaction of the system to the Coulomb repulsive forces due to charge accumulation.

Efficient barrier for charge injection in polyethylene by silver nanoparticles/plasma polymer stack

DOE Office of Scientific and Technical Information (OSTI.GOV)

Milliere, L.; Makasheva, K., E-mail: kremena.makasheva@laplace.univ-tlse.fr; Laurent, C.

2014-09-22

Charge injection from a metal/insulator contact is a process promoting the formation of space charge in polymeric insulation largely used in thick layers in high voltage equipment. The internal charge perturbs the field distribution and can lead to catastrophic failure either through its electrostatic effects or through energetic processes initiated under charge recombination and/or hot electrons effects. Injection is still ill-described in polymeric insulation due to the complexity of the contact between the polymer chains and the electrodes. Barrier heights derived from the metal work function and the polymer electronic affinity do not provide a good description of the measurementsmore » [Taleb et al., IEEE Trans. Dielectr. Electr. Insul. 20, 311–320 (2013)]. Considering the difficulty to describe the contact properties and the need to prevent charge injection in polymers for high voltage applications, we developed an alternative approach by tailoring the interface properties by the silver nanoparticles (AgNPs)/plasma polymer stack, deposited on the polymer film. Due to their small size, the AgNPs, covered by a very thin film of plasma polymer, act as deep traps for the injected charges thereby stabilizing the interface from the point of view of charge injection. After a quick description of the method for elaborating the nanostructured layer near the contact, it is demonstrated how the AgNPs/plasma polymer stack effectively prevents, in a spectacular way, the formation of bulk space charge.« less

An electro-optical and electron injection study of benzothiazole-based squaraine dyes as efficient dye-sensitized solar cell materials: a first principles study.

PubMed

Al-Fahdan, Najat Saeed; Asiri, Abdullah M; Irfan, Ahmad; Basaif, Salem A; El-Shishtawy, Reda M

2014-12-01

Squaraine dyes have attracted significant attention in many areas of daily life from biomedical imaging to semiconducting materials. Moreover, these dyes are used as photoactive materials in the field of solar cells. In the present study, we investigated the structural, electronic, photophysical, and charge transport properties of six benzothiazole-based squaraine dyes (Cis-SQ1-Cis-SQ3 and Trans-SQ1-Trans-SQ3). The effect of electron donating (-OCH3) and electron withdrawing (-COOH) groups was investigated intensively. Ground state geometry and frequency calculations were performed by applying density functional theory (DFT) at B3LYP/6-31G** level of theory. Absorption spectra were computed in chloroform at the time-dependent DFT/B3LYP/6-31G** level of theory. The driving force of electron injection (ΔG (inject)), relative driving force of electron injection (ΔG r (inject)), electronic coupling constants (|VRP|) and light harvesting efficiency (LHE) of all six compounds were calculated and compared with previously studied sensitizers. The ΔG (inject), ΔG r (inject) and |VRP| of all six compounds revealed that these sensitizers would be efficient dye-sensitized solar cell materials. Cis/Trans-SQ3 exhibited superior LHE as compared to other derivatives. The Cis/Trans geometric effect was studied and discussed with regard to electro-optical and charge transport properties.

Improved understanding of the recombination rate at inverted p+ silicon surfaces

NASA Astrophysics Data System (ADS)

To, Alexander; Ma, Fajun; Hoex, Bram

2017-08-01

The effect of positive fixed charge on the recombination rate at SiN x -passivated p+ surfaces is studied in this work. It is shown that a high positive fixed charge on a low defect density, passivated doped surface can result in a near injection level independent lifetime in a certain injection level range. This behaviour is modelled with advanced computer simulations using Sentaurus TCAD, which replicates the measurements conditions during a photoconductance based effective minority carrier lifetime measurement. The resulting simulations show that the shape of the injection level dependent lifetime is a result of the surface recombination rate, which is non-linear due to the surfaces moving into inversion with increasing injection level. As a result, the surface recombination rate switches from being limited by electrons to holes. Equations describing the surface saturation current density, J 0s, during this regime are also derived in this work.

Profiling of Current Transients in Capacitor Type Diamond Sensors.

PubMed

Gaubas, Eugenijus; Ceponis, Tomas; Meskauskaite, Dovile; Kazuchits, Nikolai

2015-06-08

The operational characteristics of capacitor-type detectors based on HPHT and CVD diamond have been investigated using perpendicular and parallel injection of carrier domain regimes. Simulations of the drift-diffusion current transients have been implemented by using dynamic models based on Shockley-Ramo's theorem, under injection of localized surface domains and of bulk charge carriers. The bipolar drift-diffusion regimes have been analyzed for the photo-induced bulk domain (packet) of excess carriers. The surface charge formation and polarization effects dependent on detector biasing voltage have been revealed. The screening effects ascribed to surface charge and to dynamics of extraction of the injected bulk excess carrier domain have been separated and explained. The parameters of drift mobility of the electrons μ(e) = 4000 cm2/Vs and holes μ(h) = 3800 cm2/Vs have been evaluated for CVD diamond using the perpendicular profiling of currents. The coefficient of carrier ambipolar diffusion D(a) = 97 cm2/s and the carrier recombination lifetime τ(R,CVD) ≌ 110 ns in CVD diamond were extracted by combining analysis of the transients of the sensor current and the microwave probed photoconductivity. The carrier trapping with inherent lifetime τR,HPHT ≌ 2 ns prevails in HPHT diamond.

Diffusion-Driven Charge Transport in Light Emitting Devices

PubMed Central

Oksanen, Jani; Suihkonen, Sami

2017-01-01

Almost all modern inorganic light-emitting diode (LED) designs are based on double heterojunctions (DHJs) whose structure and current injection principle have remained essentially unchanged for decades. Although highly efficient devices based on the DHJ design have been developed and commercialized for energy-efficient general lighting, the conventional DHJ design requires burying the active region (AR) inside a pn-junction. This has hindered the development of emitters utilizing nanostructured ARs located close to device surfaces such as nanowires or surface quantum wells. Modern DHJ III-N LEDs also exhibit resistive losses that arise from the DHJ device geometry. The recently introduced diffusion-driven charge transport (DDCT) emitter design offers a novel way to transport charge carriers to unconventionally placed ARs. In a DDCT device, the AR is located apart from the pn-junction and the charge carriers are injected into the AR by bipolar diffusion. This device design allows the integration of surface ARs to semiconductor LEDs and offers a promising method to reduce resistive losses in high power devices. In this work, we present a review of the recent progress in gallium nitride (GaN) based DDCT devices, and an outlook of potential DDCT has for opto- and microelectronics. PMID:29231900

Charge Transfer Dynamics at Dye-Sensitized ZnO and TiO2 Interfaces Studied by Ultrafast XUV Photoelectron Spectroscopy

PubMed Central

Borgwardt, Mario; Wilke, Martin; Kampen, Thorsten; Mähl, Sven; Xiao, Manda; Spiccia, Leone; Lange, Kathrin M.; Kiyan, Igor Yu.; Aziz, Emad F.

2016-01-01

Interfacial charge transfer from photoexcited ruthenium-based N3 dye molecules into ZnO thin films received controversial interpretations. To identify the physical origin for the delayed electron transfer in ZnO compared to TiO2, we probe directly the electronic structure at both dye-semiconductor interfaces by applying ultrafast XUV photoemission spectroscopy. In the range of pump-probe time delays between 0.5 to 1.0 ps, the transient signal of the intermediate states was compared, revealing a distinct difference in their electron binding energies of 0.4 eV. This finding strongly indicates the nature of the charge injection at the ZnO interface associated with the formation of an interfacial electron-cation complex. It further highlights that the energetic alignment between the dye donor and semiconductor acceptor states appears to be of minor importance for the injection kinetics and that the injection efficiency is dominated by the electronic coupling. PMID:27073060

An experimental study of the combustion characteristics in SCCI and CAI based on direct-injection gasoline engine

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lee, C.H.; Lee, K.H.

2007-08-15

Emissions remain a critical issue affecting engine design and operation, while energy conservation is becoming increasingly important. One approach to favorably address these issues is to achieve homogeneous charge combustion and stratified charge combustion at lower peak temperatures with a variable compression ratio, a variable intake temperature and a trapped rate of the EGR using NVO (negative valve overlap). This experiment was attempted to investigate the origins of these lower temperature auto-ignition phenomena with SCCI and CAI using gasoline fuel. In case of SCCI, the combustion and emission characteristics of gasoline-fueled stratified-charge compression ignition (SCCI) engine according to intake temperaturemore » and compression ratio was examined. We investigated the effects of air-fuel ratio, residual EGR rate and injection timing on the CAI combustion area. In addition, the effect of injection timing on combustion factors such as the start of combustion, its duration and its heat release rate was also investigated. (author)« less

High-performance serial block-face SEM of nonconductive biological samples enabled by focal gas injection-based charge compensation.

PubMed

Deerinck, T J; Shone, T M; Bushong, E A; Ramachandra, R; Peltier, S T; Ellisman, M H

2018-05-01

A longstanding limitation of imaging with serial block-face scanning electron microscopy is specimen surface charging. This charging is largely due to the difficulties in making biological specimens and the resins in which they are embedded sufficiently conductive. Local accumulation of charge on the specimen surface can result in poor image quality and distortions. Even minor charging can lead to misalignments between sequential images of the block-face due to image jitter. Typically, variable-pressure SEM is used to reduce specimen charging, but this results in a significant reduction to spatial resolution, signal-to-noise ratio and overall image quality. Here we show the development and application of a simple system that effectively mitigates specimen charging by using focal gas injection of nitrogen over the sample block-face during imaging. A standard gas injection valve is paired with a precisely positioned but retractable application nozzle, which is mechanically coupled to the reciprocating action of the serial block-face ultramicrotome. This system enables the application of nitrogen gas precisely over the block-face during imaging while allowing the specimen chamber to be maintained under high vacuum to maximise achievable SEM image resolution. The action of the ultramicrotome drives the nozzle retraction, automatically moving it away from the specimen area during the cutting cycle of the knife. The device described was added to a Gatan 3View system with minimal modifications, allowing high-resolution block-face imaging of even the most charge prone of epoxy-embedded biological samples. © 2017 The Authors Journal of Microscopy © 2017 Royal Microscopical Society.

The Role of Dopant Ions on Charge Injection and Transport in Electrochemically Doped Quantum Dot Films.

PubMed

Gudjonsdottir, Solrun; van der Stam, Ward; Kirkwood, Nicholas; Evers, Wiel H; Houtepen, Arjan J

2018-05-16

Control over the charge density is very important for implementation of colloidal semiconductor nanocrystals into various optoelectronic applications. A promising approach to dope nanocrystal assemblies is charge injection by electrochemistry, in which the charge compensating electrolyte ions can be regarded as external dopant ions. To gain insight into the doping mechanism and the role of the external dopant ions, we investigate charge injection in ZnO nanocrystal assemblies for a large series of charge compensating electrolyte ions with spectroelectrochemical and electrochemical transistor measurements. We show that charge injection is limited by the diffusion of cations in the nanocrystal films as their diffusion coefficient are found to be ∼7 orders of magnitude lower than those of electrons. We further show that the rate of charge injection depends strongly on the cation size and cation concentration. Strikingly, the onset of electron injection varies up to 0.4 V, depending on the size of the electrolyte cation. For the small ions Li + and Na + the onset is at significantly less negative potentials. For larger ions (K + , quaternary ammonium ions) the onset is always at the same, more negative potential, suggesting that intercalation may take place for Li + and Na + . Finally, we show that the nature of the charge compensating cation does not affect the source-drain electronic conductivity and mobility, indicating that shallow donor levels from intercalating ions fully hybridize with the quantum confined energy levels and that the reorganization energy due to intercalating ions does not strongly affect electron transport in these nanocrystal assemblies.

The Role of Dopant Ions on Charge Injection and Transport in Electrochemically Doped Quantum Dot Films

PubMed Central

2018-01-01

Control over the charge density is very important for implementation of colloidal semiconductor nanocrystals into various optoelectronic applications. A promising approach to dope nanocrystal assemblies is charge injection by electrochemistry, in which the charge compensating electrolyte ions can be regarded as external dopant ions. To gain insight into the doping mechanism and the role of the external dopant ions, we investigate charge injection in ZnO nanocrystal assemblies for a large series of charge compensating electrolyte ions with spectroelectrochemical and electrochemical transistor measurements. We show that charge injection is limited by the diffusion of cations in the nanocrystal films as their diffusion coefficient are found to be ∼7 orders of magnitude lower than those of electrons. We further show that the rate of charge injection depends strongly on the cation size and cation concentration. Strikingly, the onset of electron injection varies up to 0.4 V, depending on the size of the electrolyte cation. For the small ions Li+ and Na+ the onset is at significantly less negative potentials. For larger ions (K+, quaternary ammonium ions) the onset is always at the same, more negative potential, suggesting that intercalation may take place for Li+ and Na+. Finally, we show that the nature of the charge compensating cation does not affect the source-drain electronic conductivity and mobility, indicating that shallow donor levels from intercalating ions fully hybridize with the quantum confined energy levels and that the reorganization energy due to intercalating ions does not strongly affect electron transport in these nanocrystal assemblies. PMID:29718666

Silver nanoparticles as a key feature of a plasma polymer composite layer in mitigation of charge injection into polyethylene under dc stress

NASA Astrophysics Data System (ADS)

Milliere, L.; Maskasheva, K.; Laurent, C.; Despax, B.; Boudou, L.; Teyssedre, G.

2016-01-01

The aim of this work is to limit charge injection from a semi-conducting electrode into low density polyethylene (LDPE) under dc field by tailoring the polymer surface using a silver nanoparticles-containing layer. The layer is composed of a plane of silver nanoparticles embedded in a semi-insulating organosilicon matrix deposited on the polyethylene surface by a plasma process. Size, density and surface coverage of the nanoparticles are controlled through the plasma process. Space charge distribution in 300 μm thick LDPE samples is measured by the pulsed-electroacoustic technique following a short term (step-wise voltage increase up to 50 kV mm-1, 20 min in duration each, followed by a polarity inversion) and a longer term (up to 12 h under 40 kV mm-1) protocols for voltage application. A comparative study of space charge distribution between a reference polyethylene sample and the tailored samples is presented. It is shown that the barrier effect depends on the size distribution and the surface area covered by the nanoparticles: 15 nm (average size) silver nanoparticles with a high surface density but still not percolating form an efficient barrier layer that suppress charge injection. It is worthy to note that charge injection is detected for samples tailored with (i) percolating nanoparticles embedded in organosilicon layer; (ii) with organosilicon layer only, without nanoparticles and (iii) with smaller size silver particles (<10 nm) embedded in organosilicon layer. The amount of injected charges in the tailored samples increases gradually in the samples ranking given above. The mechanism of charge injection mitigation is discussed on the basis of complementary experiments carried out on the nanocomposite layer such as surface potential measurements. The ability of silver clusters to stabilize electrical charges close to the electrode thereby counterbalancing the applied field appears to be a key factor in explaining the charge injection mitigation effect.

Generation of high charge state metal ion beams by electron cyclotron resonance heating of vacuum arc plasma in cusp trap.

PubMed

Nikolaev, A G; Savkin, K P; Oks, E M; Vizir, A V; Yushkov, G Yu; Vodopyanov, A V; Izotov, I V; Mansfeld, D A

2012-02-01

A method for generating high charge state heavy metal ion beams based on high power microwave heating of vacuum arc plasma confined in a magnetic trap under electron cyclotron resonance conditions has been developed. A feature of the work described here is the use of a cusp magnetic field with inherent "minimum-B" structure as the confinement geometry, as opposed to a simple mirror device as we have reported on previously. The cusp configuration has been successfully used for microwave heating of gas discharge plasma and extraction from the plasma of highly charged, high current, gaseous ion beams. Now we use the trap for heavy metal ion beam generation. Two different approaches were used for injecting the vacuum arc metal plasma into the trap--axial injection from a miniature arc source located on-axis near the microwave window, and radial injection from sources mounted radially at the midplane of the trap. Here, we describe preliminary results of heating vacuum arc plasma in a cusp magnetic trap by pulsed (400 μs) high power (up to 100 kW) microwave radiation at 37.5 GHz for the generation of highly charged heavy metal ion beams.

Measurements of charge state breeding efficiency at BNL test EBIS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kondrashev, S.; Alessi, J.; Beebe, E.N.

Charge breeding of singly charged ions is required to efficiently accelerate rare isotope ion beams for nuclear and astrophysics experiments, and to enhance the accuracy of low-energy Penning trap-assisted spectroscopy. An efficient charge breeder for the Californium Rare Isotope Breeder Upgrade (CARIBU) to the ANL Tandem Linear Accelerator System (ATLAS) facility is being developed using the BNL Test Electron Beam Ion Source (Test EBIS) as a prototype. Parameters of the CARIBU EBIS charge breeder are similar to those of the BNL Test EBIS except the electron beam current will be adjustable in the range from 1 to 2 {angstrom}. Themore » electron beam current density in the CARIBU EBIS trap will be significantly higher than in existing operational charge state breeders based on the EBIS concept. The charge state breeding efficiency is expected to be about 25% for the isotope ions extracted from the CARIBU. For the success of our EBIS project, it is essential to demonstrate high breeding efficiency at the BNL Test EBIS tuned to the regime close to the parameters of the CARIBU EBIS at ANL. The breeding efficiency optimization and measurements have been successfully carried out using a Cs{sup +} surface ionization ion source for externally pulsed injection into the BNL Test EBIS. A Cs{sup +} ion beam with a total number of ions of 5 x 10{sup 8} and optimized pulse length of 70 {mu}s has been injected into the Test EBIS and charge-bred for 5.3 ms for two different electron beam currents 1 and 1.5 {angstrom}. In these experiments we have achieved 70% injection/extraction efficiency and breeding efficiency into the most abundant charge state 17%.« less

Laser pulse control of ultrafast heterogeneous electron transfer: a computational study.

PubMed

Wang, Luxia; May, Volkhard

2004-10-22

Laser pulse control of the photoinduced 90 fs charge injection from perylene into the conduction band of TiO2 is studied theoretically. The approach accounts for the electronic-ground state of the dye, the first excited state, the ionized state formed after charge injection, and the continuum of the electronic states in the conduction band, all defined vs a single reaction coordinate. To address different control tasks optimal control theory is combined with a full quantum dynamical description of the electron-vibrational motion accompanying the charge injection process. First it is proved in which way the charge injection time can be changed by tailored laser pulses. In a second step a pump-dump scheme from the perylene ground state to the first excited electronic state and back to the ground state is discussed. Because of the strong coupling of the excited perylene state to the band continuum of TiO2 this control task is more suited to an experimental test than the direct control of the charge injection.

Kerr electro-optic field mapping study of the effect of charge injection on the impulse breakdown strength of transformer oil

NASA Astrophysics Data System (ADS)

Zhang, X.; Zahn, M.

2013-10-01

The smart use of charge injection to improve breakdown strength in transformer oil is demonstrated in this paper. Hypothetically, bipolar homo-charge injection with reduced electric field at both electrodes may allow higher voltage operation without insulation failure, since electrical breakdown usually initiates at the electrode-dielectric interfaces. To find experimental evidence, the applicability and limitation of the hypothesis is first analyzed. Impulse breakdown tests and Kerr electro-optic field mapping measurements are then conducted with different combinations of parallel-plate aluminum and brass electrodes stressed by millisecond duration impulse. It is found that the breakdown voltage of brass anode and aluminum cathode is ˜50% higher than that of aluminum anode and brass cathode. This can be explained by charge injection patterns from Kerr measurements under a lower voltage, where aluminum and brass electrodes inject negative and positive charges, respectively. This work provides a feasible approach to investigating the effect of electrode material on breakdown strength.

Coupling between Transport and Injection Properties of Pentacene Field-Effect Transistors with Different Morphologies

NASA Astrophysics Data System (ADS)

Lee, Keanchuan; Weis, Martin; Taguchi, Dai; Manaka, Takaaki; Iwamoto, Mitsumasa

2013-08-01

We investigated the injection and transport properties of pentacene organic field-effect transistors (OFETs) with inclined and lamellar pentacene grains at various mutual ratios. Although the threshold voltage was conserved and no additional trapping on grain boundaries was suggested from the current-voltage measurements, the contact resistance and mobility increased linearly with the lamellar phase content. We showed that a model based on the coupling between both transport and injection properties via a space charge field caused by injected and trapped carriers accounts for these results.

Method and tool to reverse the charges in anti-reflection films used for solar cell applications

DOEpatents

Sharma, Vivek; Tracy, Clarence

2017-01-31

A method is provided for making a solar cell. The method includes providing a stack including a substrate, a barrier layer disposed on the substrate, and an anti-reflective layer disposed on the barrier layer, where the anti-reflective layer has charge centers. The method also includes generating a corona with a charging tool and contacting the anti-reflective layer with the corona thereby injecting charge into at least some of the charge centers in the anti-reflective layer. Ultra-violet illumination and temperature-based annealing may be used to modify the charge of the anti-reflective layer.

Charge movement in a GaN-based hetero-structure field effect transistor structure with carbon doped buffer under applied substrate bias

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pooth, Alexander, E-mail: a.pooth@bristol.ac.uk; IQE; Uren, Michael J.

2015-12-07

Charge trapping and transport in the carbon doped GaN buffer of a GaN-based hetero-structure field effect transistor (HFET) has been investigated under both positive and negative substrate bias. Clear evidence of redistribution of charges in the carbon doped region by thermally generated holes is seen, with electron injection and capture observed during positive bias. Excellent agreement is found with simulations. It is shown that these effects are intrinsic to the carbon doped GaN and need to be controlled to provide reliable and efficient GaN-based power HFETs.

Tuning pentacene based dye-sensitized solar cells.

PubMed

Kunzmann, Andreas; Gruber, Marco; Casillas, Rubén; Tykwinski, Rik R; Costa, Rubén D; Guldi, Dirk M

2018-05-10

We report on the synthesis, as well as photophysical and electrochemical characterization of a new family of pentacene derivatives, which are applied in n-type dye-sensitized solar cells (DSSCs). As far as the molecular structure of the pentacene is concerned, the synthetic design focuses on cyano acrylic tethered at the 13-position of the pentacene chromophore. The electrolyte composition features increasing amounts of Li+ ions as an additive. In general, the increase of Li+ concentrations extrinsically reduces the quasi Fermi level of the photoanode and as such facilitates the electron injection process. We demonstrate that pentacene derivatives give rise to a unique charge injection process, which is controlled by the positioning of the quasi Fermi level energies as a function of the Li+ concentration. As a result of the enhanced charge injection, device efficiencies as high as 1.5% are achieved, representing a 3-fold increase from previously reported efficiencies in pentacene-based DSSCs. These findings are supported by device analysis in combination with transient absorption and electrochemical impedance spectroscopy assays.

Ultrafast charge separation dynamics in opaque, operational dye-sensitized solar cells revealed by femtosecond diffuse reflectance spectroscopy

PubMed Central

Ghadiri, Elham; Zakeeruddin, Shaik M.; Hagfeldt, Anders; Grätzel, Michael; Moser, Jacques-E.

2016-01-01

Efficient dye-sensitized solar cells are based on highly diffusive mesoscopic layers that render these devices opaque and unsuitable for ultrafast transient absorption spectroscopy measurements in transmission mode. We developed a novel sub-200 femtosecond time-resolved diffuse reflectance spectroscopy scheme combined with potentiostatic control to study various solar cells in fully operational condition. We studied performance optimized devices based on liquid redox electrolytes and opaque TiO2 films, as well as other morphologies, such as TiO2 fibers and nanotubes. Charge injection from the Z907 dye in all TiO2 morphologies was observed to take place in the sub-200 fs time scale. The kinetics of electron-hole back recombination has features in the picosecond to nanosecond time scale. This observation is significantly different from what was reported in the literature where the electron-hole back recombination for transparent films of small particles is generally accepted to occur on a longer time scale of microseconds. The kinetics of the ultrafast electron injection remained unchanged for voltages between +500 mV and –690 mV, where the injection yield eventually drops steeply. The primary charge separation in Y123 organic dye based devices was clearly slower occurring in two picoseconds and no kinetic component on the shorter femtosecond time scale was recorded. PMID:27095505

Planetary investigation utilizing an imaging spectrometer system based upon charge injection technology

NASA Technical Reports Server (NTRS)

Wattson, R. B.; Harvey, P.; Swift, R.

1975-01-01

An intrinsic silicon charge injection device (CID) television sensor array has been used in conjunction with a CaMoO4 colinear tunable acousto optic filter, a 61 inch reflector, a sophisticated computer system, and a digital color TV scan converter/computer to produce near IR images of Saturn and Jupiter with 10A spectral resolution and approximately 3 inch spatial resolution. The CID camera has successfully obtained digitized 100 x 100 array images with 5 minutes of exposure time, and slow-scanned readout to a computer. Details of the equipment setup, innovations, problems, experience, data and final equipment performance limits are given.

Impact of charge carrier injection on single-chain photophysics of conjugated polymers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hofmann, Felix J.; Vogelsang, Jan, E-mail: jan.vogelsang@physik.uni-regensburg.de; Lupton, John M.

Charges in conjugated polymer materials have a strong impact on the photophysics and their interaction with the primary excited state species has to be taken into account in understanding device properties. Here, we employ single-molecule spectroscopy to unravel the influence of charges on several photoluminescence (PL) observables. The charges are injected either stochastically by a photochemical process or deterministically in a hole-injection sandwich device configuration. We find that upon charge injection, besides a blue-shift of the PL emission and a shortening of the PL lifetime due to quenching and blocking of the lowest-energy chromophores, the non-classical photon arrival time distributionmore » of the multichromophoric chain is modified towards a more classical distribution. Surprisingly, the fidelity of photon antibunching deteriorates upon charging, whereas one would actually expect the opposite: the number of chromophores to be reduced. A qualitative model is presented to explain the observed PL changes. The results are of interest to developing a microscopic understanding of the intrinsic charge-exciton quenching interaction in devices.« less

Bimodal exciton-plasmon light sources controlled by local charge carrier injection.

PubMed

Merino, Pablo; Rosławska, Anna; Große, Christoph; Leon, Christopher C; Kuhnke, Klaus; Kern, Klaus

2018-05-01

Electrical charges can generate photon emission in nanoscale quantum systems by two independent mechanisms. First, radiative recombination of pairs of oppositely charged carriers generates sharp excitonic lines. Second, coupling between currents and collective charge oscillations results in broad plasmonic bands. Both luminescence modes can be simultaneously generated upon charge carrier injection into thin C 60 crystallites placed in the plasmonic nanocavity of a scanning tunneling microscope (STM). Using the sharp tip of the STM as a subnanometer-precise local electrode, we show that the two types of electroluminescence are induced by two separate charge transport channels. Holes injected into the valence band promote exciton generation, whereas electrons extracted from the conduction band cause plasmonic luminescence. The different dynamics of the two mechanisms permit controlling their relative contribution in the combined bimodal emission. Exciton recombination prevails for low charge injection rates, whereas plasmon decay outshines for high tunneling currents. The continuous transition between both regimes is described by a rate model characterizing emission dynamics on the nanoscale. Our work provides the basis for developing blended exciton-plasmon light sources with advanced functionalities.

Charge-injection-device 2 x 64 element infrared array performance

NASA Technical Reports Server (NTRS)

Mckelvey, M. E.; Mccreight, C. R.; Goebel, J. H.; Reeves, A. A.

1985-01-01

Three 2 x 64 element Si:Bi accumulation-mode charge-injection-device (CID) arrays were tested at low and moderate background to evaluate their usefulness for space-based astronomical observations. Testing was conducted both in the laboratory and in ground-based telescope IR observations. The devices showed an average readout noise level below 200 equivalent electrons, a peak responsivity of 4 A/W, and a noise equivalent power of 3 x 10 to the -17th W/sq rt Hz. This sensitivity compares well with that of nonintegrating discrete extrinsic silicon photoconductors. The array well capacity was significantly smaller than predicted. The measured sensitivity makes extrinsic silicon CID arrays useful for certain astronomical applications. However, their readout efficiency and frequency response represent serious limitations in low-background applications.

The importance of holes in aluminium tris-8-hydroxyquinoline (Alq{sub 3}) devices with Fe and NiFe contacts

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Hongtao; Desai, P.; Kreouzis, T.

To study the dominant charge carrier polarity in aluminium tris-8-hydroxyquinoline (Alq{sub 3}) based spin valves, single Alq{sub 3} layer devices with NiFe, ITO, Fe, and aluminium electrodes were fabricated and characterised by Time of Flight (ToF) and Dark Injection (DI) techniques, yielding a lower hole mobility compared to electron mobility. We compare the mobility measured by DI for the dominant carrier injected from NiFe and Fe electrodes into Alq{sub 3}, to that of holes measured by ToF. This comparison leads us to conclude that the dominant charge carriers in Alq{sub 3} based spin valves with NiFe or Fe electrodes aremore » holes.« less

Performance of charge-injection-device infrared detector arrays at low and moderate backgrounds

NASA Technical Reports Server (NTRS)

Mckelvey, M. E.; Mccreight, C. R.; Goebel, J. H.; Reeves, A. A.

1985-01-01

Three 2 x 64 element charge injection device infrared detector arrays were tested at low and moderate background to evaluate their usefulness for space based astronomical observations. Testing was conducted both in the laboratory and in ground based telescope observations. The devices showed an average readout noise level below 200 equivalent electrons, a peak responsivity of 4 A/W, and a noise equivalent power of 3x10 sq root of W/Hz. Array well capacity was measured to be significantly smaller than predicted. The measured sensitivity, which compares well with that of nonintegrating discrete extrinsic silicon photoconductors, shows these arrays to be useful for certain astronomical observations. However, the measured readout efficiency and frequency response represent serious limitations in low background applications.

Study Trapped Charge Distribution in P-Channel Silicon-Oxide-Nitride-Oxide-Silicon Memory Device Using Dynamic Programming Scheme

NASA Astrophysics Data System (ADS)

Li, Fu-Hai; Chiu, Yung-Yueh; Lee, Yen-Hui; Chang, Ru-Wei; Yang, Bo-Jun; Sun, Wein-Town; Lee, Eric; Kuo, Chao-Wei; Shirota, Riichiro

2013-04-01

In this study, we precisely investigate the charge distribution in SiN layer by dynamic programming of channel hot hole induced hot electron injection (CHHIHE) in p-channel silicon-oxide-nitride-oxide-silicon (SONOS) memory device. In the dynamic programming scheme, gate voltage is increased as a staircase with fixed step amplitude, which can prohibits the injection of holes in SiN layer. Three-dimensional device simulation is calibrated and is compared with the measured programming characteristics. It is found, for the first time, that the hot electron injection point quickly traverses from drain to source side synchronizing to the expansion of charged area in SiN layer. As a result, the injected charges quickly spread over on the almost whole channel area uniformly during a short programming period, which will afford large tolerance against lateral trapped charge diffusion by baking.

Profiling of Current Transients in Capacitor Type Diamond Sensors

PubMed Central

Gaubas, Eugenijus; Ceponis, Tomas; Meskauskaite, Dovile; Kazuchits, Nikolai

2015-01-01

The operational characteristics of capacitor-type detectors based on HPHT and CVD diamond have been investigated using perpendicular and parallel injection of carrier domain regimes. Simulations of the drift-diffusion current transients have been implemented by using dynamic models based on Shockley-Ramo’s theorem, under injection of localized surface domains and of bulk charge carriers. The bipolar drift-diffusion regimes have been analyzed for the photo-induced bulk domain (packet) of excess carriers. The surface charge formation and polarization effects dependent on detector biasing voltage have been revealed. The screening effects ascribed to surface charge and to dynamics of extraction of the injected bulk excess carrier domain have been separated and explained. The parameters of drift mobility of the electrons μe = 4000 cm2/Vs and holes μh = 3800 cm2/Vs have been evaluated for CVD diamond using the perpendicular profiling of currents. The coefficient of carrier ambipolar diffusion Da = 97 cm2/s and the carrier recombination lifetime τR,CVD ≌ 110 ns in CVD diamond were extracted by combining analysis of the transients of the sensor current and the microwave probed photoconductivity. The carrier trapping with inherent lifetime τR,HPHT ≌ 2 ns prevails in HPHT diamond. PMID:26061200

Criteria for selecting electrodes for electrical stimulation: theoretical and practical considerations.

PubMed

Brummer, S B; Robblee, L S; Hambrecht, F T

1983-01-01

Smaller, more charge-intensive electrodes are needed for "safe" stimulation of the nervous system. In this paper we review critical concepts and the state of the art in electrodes. Control of charge density and charge balance are essential to avoid tissue electrolysis. Chemical criteria for "safe" stimulation are reviewed ("safe" is equated with "chemically reversible"). An example of a safe, but generally impractical, charge-injection process is double-layer charging. The limit here is the onset of irreversible faradaic processes. More charge can be safely injected with so-called "capacitor" electrodes, such as porous intermixtures of Ta/Ta2O5. BaTiO3 has excellent dielectric properties and may provide a new generation of capacitor electrodes. Faradaic charge injection is usually partially irreversible since some of the products escape into the solution. With Pt, up to 400 muc/cm2 real area can be absorbed by faradaic reactions of surface-adsorbed species, but a small part is lost due to metal dissolution. The surface of "activated" Ir is covered with a multilayer hydrated oxide. Charge injection occurs via rapid valence change within this oxide. Little or no metal dissolution is observed, and gassing limits are not exceeded even under stringent conditions.

Mixed Mode Fuel Injector And Injection System

DOEpatents

Stewart, Chris Lee; Tian, Ye; Wang, Lifeng; Shafer, Scott F.

2005-12-27

A fuel injector includes a homogenous charge nozzle outlet set and a conventional nozzle outlet set that are controlled respectively by first and second three way needle control valves. Each fuel injector includes first and second concentric needle valve members. One of the needle valve members moves to an open position for a homogenous charge injection event, while the other needle valve member moves to an open position for a conventional injection event. The fuel injector has the ability to operate in a homogenous charge mode with a homogenous charge spray pattern, a conventional mode with a conventional spray pattern or a mixed mode.

Thermal analysis of injection beam dump of high-intensity rapid-cycling synchrotron in J-PARC

NASA Astrophysics Data System (ADS)

Kamiya, J.; Saha, P. K.; Yamamoto, K.; Kinsho, M.; Nihei, T.

2017-10-01

The beam dump at the beam injection area in the J-PARC 3-GeV rapid cycling synchrotron (RCS) accepts beams that pass through the charge exchange foil without ideal electron stripping during the multi-turn beam injection. The injection beam dump consists of the beam pipe, beam stopper, radiation shield, and cooling mechanism. The ideal beam power into the injection beam dump is 400 W in the case of design RCS extraction beam power of 1 MW with a healthy foil, which has 99.7 % charge stripping efficiency. On the other hand, as a radiation generator, the RCS is permitted to be operated with maximum average beam power of 4 kW into the injection beam dump based on the radiation shielding calculation, in consideration of lower charge stripping efficiency due to the foil deterioration. In this research, to evaluate the health of the RCS injection beam dump system from the perspective of the heat generation, a thermal analysis was performed based on the actual configuration with sufficiently large region, including the surrounding concrete and soil. The calculated temperature and heat flux density distribution showed the validity of the mesh spacing and model range. The calculation result showed that the dumped 4 kW beam causes the temperature to increase up to 330, 400, and 140 °C at the beam pipe, beam stopper, and radiation shield, respectively. Although these high temperatures induce stress in the constituent materials, the calculated stress values were lower than the ultimate tensile strength of each material. Transient temperature analysis of the beam stopper, which simulated the sudden break of the charge stripper foil, demonstrated that one bunched beam pulse with the maximum beam power does not lead to a serious rise in the temperature of the beam stopper. Furthermore, from the measured outgassing rate of stainless steel at high temperature, the rise in beam line pressure due to additive outgassing from the heated beam pipe was estimated to have a negligible effect on beam line pressure. The flow and results of the evaluation in this analysis would provide a good indication for both the verification of the existing beam dumps, and the design of beam dumps in new accelerators with higher intensity beam.

Analog-digital simulation of transient-induced logic errors and upset susceptibility of an advanced control system

NASA Technical Reports Server (NTRS)

Carreno, Victor A.; Choi, G.; Iyer, R. K.

1990-01-01

A simulation study is described which predicts the susceptibility of an advanced control system to electrical transients resulting in logic errors, latched errors, error propagation, and digital upset. The system is based on a custom-designed microprocessor and it incorporates fault-tolerant techniques. The system under test and the method to perform the transient injection experiment are described. Results for 2100 transient injections are analyzed and classified according to charge level, type of error, and location of injection.

Imaging the photoinduced charge injection in CdS/TiO2 nanoparticles by the sequential fluorescence mapping method

NASA Astrophysics Data System (ADS)

Frederice, Rafael; Lencione, Diego; Gehlen, Marcelo H.

2017-03-01

The combination of a sensitizer and TiO2 nanoparticles forming a photocatalytic material is a central issue in many fields of applied photochemistry. The charge injection of emissive sensitizers into the conduction band of the semiconductor TiO2 may form a photoactive region that becomes dark, or it has a very low emission signal due to the generation of sensitizer radicals. However, by sequential coupling of a selected photoredox dye, such as resazurin, the dark region may become fluorescent at the interfaces where the charge injection has taken place due to the concomitant formation of fluorescent resorufin by cascade electron transfer. Using this strategy and a total internal reflection fluorescence microscopy (TIRFM) image, the charge injection in TiO2/CdS and SiO2/TiO2/CdS nanoparticles is investigated The method allows the charge injection efficiency of the excited CdS into TiO2 to be evaluated qualitatively, explaining the differences observed for these photocatalytic materials in H2 generation.

Imaging the photoinduced charge injection in CdS/TiO2 nanoparticles by the sequential fluorescence mapping method.

PubMed

Frederice, Rafael; Lencione, Diego; Gehlen, Marcelo H

2017-02-10

The combination of a sensitizer and TiO 2 nanoparticles forming a photocatalytic material is a central issue in many fields of applied photochemistry. The charge injection of emissive sensitizers into the conduction band of the semiconductor TiO 2 may form a photoactive region that becomes dark, or it has a very low emission signal due to the generation of sensitizer radicals. However, by sequential coupling of a selected photoredox dye, such as resazurin, the dark region may become fluorescent at the interfaces where the charge injection has taken place due to the concomitant formation of fluorescent resorufin by cascade electron transfer. Using this strategy and a total internal reflection fluorescence microscopy (TIRFM) image, the charge injection in TiO 2 /CdS and SiO 2 /TiO 2 /CdS nanoparticles is investigated The method allows the charge injection efficiency of the excited CdS into TiO 2 to be evaluated qualitatively, explaining the differences observed for these photocatalytic materials in H 2 generation.

Mixed mode fuel injector with individually moveable needle valve members

DOEpatents

Stewart, Chris; Chockley, Scott A.; Ibrahim, Daniel R.; Lawrence, Keith; Tomaseki, Jay; Azam, Junru H.; Tian, Steven Ye; Shafer, Scott F.

2004-08-03

A fuel injector includes a homogenous charge nozzle outlet set and a conventional nozzle outlet set controlled respectively, by first and second needle valve members. One of the needle valve members moves to an open position while the other needle valve member remains stationary for a homogeneous charge injection event. The former needle valve member stays stationary while the other needle valve member moves to an open position for a conventional injection event. One of the needle valve members is at least partially positioned in the other needle valve member. Thus, the injector can perform homogeneous charge injection events, conventional injection events, or even a mixed mode having both types of injection events in a single engine cycle.

Numerical Investigation of Novel Oxygen Blast Furnace Ironmaking Processes

NASA Astrophysics Data System (ADS)

Li, Zhaoyang; Kuang, Shibo; Yu, Aibing; Gao, Jianjun; Qi, Yuanhong; Yan, Dingliu; Li, Yuntao; Mao, Xiaoming

2018-04-01

Oxygen blast furnace (OBF) ironmaking process has the potential to realize "zero carbon footprint" production, but suffers from the "thermal shortage" problem. This paper presents three novel OBF processes, featured by belly injection of reformed coke oven gas, burden hot-charge operation, and their combination, respectively. These processes were studied by a multifluid process model. The applicability of the model was confirmed by comparing the numerical results against the measured key performance indicators of an experimental OBF operated with or without injection of reformed coke oven gas. Then, these different OBF processes together with a pure OBF were numerically examined in aspects of in-furnace states and global performance, assuming that the burden quality can be maintained during the hot-charge operation. The numerical results show that under the present conditions, belly injection and hot charge, as auxiliary measures, are useful for reducing the fuel rate and increasing the productivity for OBFs but in different manners. Hot charge should be more suitable for OBFs of different sizes because it improves the thermochemical states throughout the dry zone rather than within a narrow region in the case of belly injection. The simultaneous application of belly injection and hot charge leads to the best process performance, at the same time, lowering down hot-charge temperature to achieve the same carbon consumption and hot metal temperature as that achieved when applying the hot charge alone. This feature will be practically beneficial in the application of hot-charge operation. In addition, a systematic study of hot-charge temperature reveals that optimal hot-charge temperatures can be identified according to the utilization efficiency of the sensible heat of hot burden.

40 CFR Table 9 to Subpart Wwww of... - Initial Compliance With Work Practice Standards

Code of Federal Regulations, 2014 CFR

2014-07-01

... compression/injection molding uncover, unwrap or expose only one charge per mold cycle per compression/injection molding machine. For machines with multiple molds, one charge means sufficient material to fill... cycle per compression/injection molding machine, or prior to the loader, hoppers are closed except when...

Ferroelectric Diodes with Charge Injection and Trapping

NASA Astrophysics Data System (ADS)

Fan, Zhen; Fan, Hua; Lu, Zengxing; Li, Peilian; Huang, Zhifeng; Tian, Guo; Yang, Lin; Yao, Junxiang; Chen, Chao; Chen, Deyang; Yan, Zhibo; Lu, Xubing; Gao, Xingsen; Liu, Jun-Ming

2017-01-01

Ferroelectric diodes with polarization-modulated Schottky barriers are promising for applications in resistive switching (RS) memories. However, they have not achieved satisfactory performance reliability as originally hoped. The physical origins underlying this issue have not been well studied, although they deserve much attention. Here, by means of scanning Kelvin probe microscopy we show that the electrical poling of ferroelectric diodes can cause significant charge injection and trapping besides polarization switching. We further show that the reproducibility and stability of switchable diode-type RS behavior are significantly affected by the interfacial traps. A theoretical model is then proposed to quantitatively describe the modifications of Schottky barriers by charge injection and trapping. This model is able to reproduce various types of hysteretic current-voltage characteristics as experimentally observed. It is further revealed that the charge injection and trapping can significantly modify the electroresistance ratio, RS polarity, and high- or low-resistance states initially defined by the polarization direction. Several approaches are suggested to suppress the effect of charge injection and trapping so as to realize high-performance polarization-reversal-induced RS. This study, therefore, reveals the microscopic mechanisms for the RS behavior comodulated by polarization reversal and charge trapping in ferroelectric diodes, and also provides useful suggestions for developing reliable ferroelectric RS memories.

Dissociation of methane on the surface of charged defective carbon nanotubes

NASA Astrophysics Data System (ADS)

Guo, Z. H.; Yan, X. H.; Xiao, Y.

2010-03-01

Based on the framework of density functional theory (CASTEP and DMOL 3 codes), we simulate the dissociation of methane (CH 4) molecule on the surface of charged defective carbon nanotubes (CNTs). The results display that a charged CNT with carbon (C) and molybdenum (Mo) dopants can effectively dissociate CH 4 molecule, and the adsorption strength of H and CH 3 can be controlled by the injected negative charges. Moreover, the barrier between the transition state (TS) and the reactant is 0.1014 eV, and a single imaginary frequency of -0.3 cm is found for the transition state structure.

Plasmon enhanced heterogeneous electron transfer with continuous band energy model

NASA Astrophysics Data System (ADS)

Zhao, Dandan; Niu, Lu; Wang, Luxia

2017-08-01

Photoinduced charge injection from a perylene dye molecule into the conduction band of a TiO2 system decorated by a metal nanoparticles (MNP) is studied theoretically. Utilizing the density matrix theory the charge transfer dynamics is analyzed. The continuous behavior of the TiO2 conduction band is accounted for by a Legendre polynomials expansion. The simulations consider optical excitation of the dye molecule coupled to the MNP and the subsequent electron injection into the TiO2 semiconductor. Due to the energy transfer coupling between the molecule and the MNP optical excitation and subsequent charge injection into semiconductor is strongly enhanced. The respective enhancement factor can reach values larger than 103. Effects of pulse duration, coupling strength and energetic resonances are also analyzed. The whole approach offers an efficient way to increase charge injection in dye-sensitized solar cells.

Pulse-actuated fuel-injection spark plug

DOEpatents

Murray, Ian; Tatro, Clement A.

1978-01-01

A replacement spark plug for reciprocating internal combustion engines that functions as a fuel injector and as a spark plug to provide a "stratified-charge" effect. The conventional carburetor is retained to supply the main fuel-air mixture which may be very lean because of the stratified charge. The replacement plug includes a cylindrical piezoelectric ceramic which contracts to act as a pump whenever an ignition pulse is applied to a central rod through the ceramic. The rod is hollow at its upper end for receiving fuel, it is tapered along its lower length to act as a pump, and it is flattened at its lower end to act as a valve for fuel injection from the pump into the cylinder. The rod also acts as the center electrode of the plug, with the spark jumping from the plug base to the lower end of the rod to thereby provide spark ignition that has inherent proper timing with the fuel injection.

Current-induced switching in a magnetic insulator

NASA Astrophysics Data System (ADS)

Avci, Can Onur; Quindeau, Andy; Pai, Chi-Feng; Mann, Maxwell; Caretta, Lucas; Tang, Astera S.; Onbasli, Mehmet C.; Ross, Caroline A.; Beach, Geoffrey S. D.

2017-03-01

The spin Hall effect in heavy metals converts charge current into pure spin current, which can be injected into an adjacent ferromagnet to exert a torque. This spin-orbit torque (SOT) has been widely used to manipulate the magnetization in metallic ferromagnets. In the case of magnetic insulators (MIs), although charge currents cannot flow, spin currents can propagate, but current-induced control of the magnetization in a MI has so far remained elusive. Here we demonstrate spin-current-induced switching of a perpendicularly magnetized thulium iron garnet film driven by charge current in a Pt overlayer. We estimate a relatively large spin-mixing conductance and damping-like SOT through spin Hall magnetoresistance and harmonic Hall measurements, respectively, indicating considerable spin transparency at the Pt/MI interface. We show that spin currents injected across this interface lead to deterministic magnetization reversal at low current densities, paving the road towards ultralow-dissipation spintronic devices based on MIs.

Analysis of batch-related influences on injection molding processes viewed in the context of electro plating quality demands

NASA Astrophysics Data System (ADS)

Siepmann, Jens P.; Wortberg, Johannes; Heinzler, Felix A.

2016-03-01

The injection molding process is mandatorily influenced by the viscosity of the material. By varying the material batch the viscosity of the polymer changes. For the process and part quality the initial conditions of the material in addition to the processing parameters define the process and product quality. A high percentage of technical polymers processed in injection molding is refined in a follow-up production step, for example electro plating. Processing optimized for electro plating often requires avoiding high shear stresses by using low injection speed and pressure conditions. Therefore differences in the material charges' viscosity occur especially in the quality related low shear rate area. These differences and quality related influences can be investigated by high detail rheological analysis and process simulation based on adapted material describing models. Differences in viscosity between batches can be detected by measurements with high-pressure-capillary-rheometers or oscillatory rheometers for low shear rates. A combination of both measurement techniques is possible by the Cox-Merz-Relation. The detected differences in the rheological behavior of both charges are summarized in two material behavior describing model approaches and added to the simulation. In this paper the results of processing-simulations with standard filling parameters are presented with two ABS charges. Part quality defining quantities such as temperature, pressure and shear stress are investigated and the influence of charge variations is pointed out with respect to electro plating quality demands. Furthermore, the results of simulations with a new quality related process control are presented and compared to the standard processing.

Insulating Material Requirements for Low-Power-Consumption Electrowetting-Based Liquid Lenses.

PubMed

Chevalliot, Stéphanie; Malet, Géraldine; Keppner, Herbert; Berge, Bruno

2016-12-27

Insulating materials from the parylene family were investigated for use in low-power-consumption electrowetting-based liquid lenses. It was shown that for DC-driven operations, parylene C leads to hysteresis, regardless of the presence of a hydrophobic top coat. This hysteresis was attributed to the non-negligible time needed to reach a stable contact angle, due to charge injection and finite conductivity of the material. It was further demonstrated that by using materials with better insulating properties, such as parylene HT and VT4, satisfactory results can be obtained under DC voltages, reaching a low contact angle hysteresis of below 0.2°. We propose a simplified model that takes into account the injection of charges from both sides of the insulating material (the liquid side and the electrode side), showing that electrowetting response can be both increased and decreased.

Review and test of chilldown methods for space-based cryogenic tanks

NASA Astrophysics Data System (ADS)

Chato, David J.; Sanabria, Rafael

The literature for tank chilldown methods applicable to cryogenic tankage in the zero gravity environment of earth orbit is reviewed. One method is selected for demonstration in a ground based test. The method selected for investigation was the charge-hold-vent method which uses repeated injection of liquid slugs, followed by a hold to allow complete vaporization of the liquid and a vent of the tank to space vacuum to cool tankage to the desired temperature. The test was conducted on a 175 cubic foot, 2219 aluminum walled tank weighing 329 pounds, which was previously outfitted with spray systems to test nonvented fill technologies. To minimize hardware changes, a simple control-by-pressure scheme was implemented to control injected liquid quantities. The tank cooled from 440 R sufficiently in six charge-hold-vent cycles to allow a complete nonvented fill of the test tank. Liquid hydrogen consumed in the process is estimated at 32 pounds.

Review and test of chilldown methods for space-based cryogenic tanks

NASA Technical Reports Server (NTRS)

Chato, David J.; Sanabria, Rafael

1991-01-01

The literature for tank chilldown methods applicable to cryogenic tankage in the zero gravity environment of earth orbit is reviewed. One method is selected for demonstration in a ground based test. The method selected for investigation was the charge-hold-vent method which uses repeated injection of liquid slugs, followed by a hold to allow complete vaporization of the liquid and a vent of the tank to space vacuum to cool tankage to the desired temperature. The test was conducted on a 175 cubic foot, 2219 aluminum walled tank weighing 329 pounds, which was previously outfitted with spray systems to test nonvented fill technologies. To minimize hardware changes, a simple control-by-pressure scheme was implemented to control injected liquid quantities. The tank cooled from 440 R sufficiently in six charge-hold-vent cycles to allow a complete nonvented fill of the test tank. Liquid hydrogen consumed in the process is estimated at 32 pounds.

Pulse shape discrimination based on fast signals from silicon photomultipliers

NASA Astrophysics Data System (ADS)

Yu, Junhao; Wei, Zhiyong; Fang, Meihua; Zhang, Zixia; Cheng, Can; Wang, Yi; Su, Huiwen; Ran, Youquan; Zhu, Qingwei; Zhang, He; Duan, Kai; Chen, Ming; Liu, Meng

2018-06-01

Recent developments in organic plastic scintillators capable of pulse shape discrimination (PSD) enable a breakthrough in discrimination between neutrons and gammas. Plastic scintillator detectors coupled with silicon photomultipliers (SiPMs) offer many advantages, such as lower power consumption, smaller volume, and especially insensitivity to magnetic fields, compared with conventional photomultiplier tubes (PMTs). A SensL SiPM has two outputs: a standard output and a fast output. It is known that the charge injected into the fast output electrode is typically approximately 2% of the total charge generated during the avalanche, whereas the charge injected into the standard output electrode is nearly 98% of the total. Fast signals from SiPMs exhibit better performance in terms of timing and time-correlated measurements compared with standard signals. The pulse duration of a standard signal is on the order of hundreds of nanoseconds, whereas the pulse duration of the main monopole waveform of a fast signal is a few tens of nanoseconds. Fast signals are traditionally thought to be suitable for photon counting at very high speeds but unsuitable for PSD due to the partial charge collection. Meanwhile, the standard outputs of SiPMs coupled with discriminating scintillators have yielded nice PSD performances, but there have been no reports on PSD using fast signals. Our analysis shows that fast signals can also provide discrimination if the rate of charge injection into the fast output electrode is fixed for each event, even though only a portion of the charge is collected. In this work, we achieved successful PSD using fast signals; meanwhile, using a coincidence timing window of less 3 nanoseconds between the readouts from both ends of the detector reduced the influence of the high SiPM dark current. We experimentally achieved good timing performance and PSD capability simultaneously.

Two dimensional simulation of patternable conducting polymer electrode based organic thin film transistor

NASA Astrophysics Data System (ADS)

Nair, Shiny; Kathiresan, M.; Mukundan, T.

2018-02-01

Device characteristics of organic thin film transistor (OTFT) fabricated with conducting polyaniline:polystyrene sulphonic acid (PANi-PSS) electrodes, patterned by the Parylene lift-off method are systematically analyzed by way of two dimensional numerical simulation. The device simulation was performed taking into account field-dependent mobility, low mobility layer at the electrode-semiconductor interface, trap distribution in pentacene film and trapped charge at the organic/insulator interface. The electrical characteristics of bottom contact thin film transistor with PANi-PSS electrodes and pentacene active material is superior to those with palladium electrodes due to a lower charge injection barrier. Contact resistance was extracted in both cases by the transfer line method (TLM). The extracted charge concentration and potential profile from the two dimensional numerical simulation was used to explain the observed electrical characteristics. The simulated device characteristics not only matched the experimental electrical characteristics, but also gave an insight on the charge injection, transport and trap properties of the OTFTs as a function of different electrode materials from the perspectives of transistor operation.

Simulation of the charge migration in DNA under irradiation with heavy ions.

PubMed

Belov, Oleg V; Boyda, Denis L; Plante, Ianik; Shirmovsky, Sergey Eh

2015-01-01

A computer model to simulate the processes of charge injection and migration through DNA after irradiation by a heavy charged particle was developed. The most probable sites of charge injection were obtained by merging spatial models of short DNA sequence and a single 1 GeV/u iron particle track simulated by the code RITRACKS (Relativistic Ion Tracks). Charge migration was simulated by using a quantum-classical nonlinear model of the DNA-charge system. It was found that charge migration depends on the environmental conditions. The oxidative damage in DNA occurring during hole migration was simulated concurrently, which allowed the determination of probable locations of radiation-induced DNA lesions.

Signal processing applications of massively parallel charge domain computing devices

NASA Technical Reports Server (NTRS)

Fijany, Amir (Inventor); Barhen, Jacob (Inventor); Toomarian, Nikzad (Inventor)

1999-01-01

The present invention is embodied in a charge coupled device (CCD)/charge injection device (CID) architecture capable of performing a Fourier transform by simultaneous matrix vector multiplication (MVM) operations in respective plural CCD/CID arrays in parallel in O(1) steps. For example, in one embodiment, a first CCD/CID array stores charge packets representing a first matrix operator based upon permutations of a Hartley transform and computes the Fourier transform of an incoming vector. A second CCD/CID array stores charge packets representing a second matrix operator based upon different permutations of a Hartley transform and computes the Fourier transform of an incoming vector. The incoming vector is applied to the inputs of the two CCD/CID arrays simultaneously, and the real and imaginary parts of the Fourier transform are produced simultaneously in the time required to perform a single MVM operation in a CCD/CID array.

A novel blood-pooling MR contrast agent: Carboxymethyl-diethylaminoethyl dextran magnetite.

PubMed

Sonoda, Akinaga; Nitta, Norihisa; Tsuchiya, Keiko; Nitta-Seko, Ayumi; Ohta, Shinichi; Otani, Hideji; Murata, Kiyoshi

2016-12-01

Gadofosveset trisodium is available as a prolonged pooling vascular contrast agent for magnetic resonance imaging. As gadolinium (Gd)-based agents may increase the risk for nephrogenic systemic fibrosis in patients with severe renal insufficiency, the present study synthesized carboxymethyl-diethylaminoethyl dextran magnetite (CMEADM) particles as a blood-pooling, non-Gd‑based contrast agent. CMEADM particles carry a negative or positive charge due to the binding of amino and carboxyl groups to the hydroxyl group of dextran. The present study evaluated whether the degree of charge alters the blood‑pooling time. The evaluation was performed by injecting four groups of three Japanese white rabbits each with CMEADM‑, CMEADM2‑, CMEADM+ (surface charges: ‑10.4, ‑41.0 and +9.6 mV, respectively) or with ultrasmall superparamagnetic iron oxide (USPIO; ‑11.5 mV). The relative signal intensity (SIrel) of each was calculated using the following formula: SIrel = (SI post‑contrast ‑ SI pre‑contrast / SI pre‑contrast) x 100. Following injection with the CMEADMs, but not with USPIO, the in vivo pooling time was prolonged to >300 min. No significant differences were attributable to the electric charge among the CMEADM‑, CMEADM2‑ or and CMEADM+ particles when analyzed with analysis of variance and Tukey's HSD test. Taken together, all three differently‑charged CMEADM2 particles exhibited prolonged vascular enhancing effects, compared with the USPIO. The degree of charge of the contrast agents used in the present study did not result in alteration of the prolonged blood pooling time.

Assessment study of infrared detector arrays for low-background astronomical research

NASA Technical Reports Server (NTRS)

Ando, K. J.

1978-01-01

The current state-of-the-art of infrared detector arrays employing charge coupled devices (CCD) or charge injection devices (CID) readout are assessed. The applicability, limitations and potentials of such arrays under the low-background astronomical observing conditions of interest for SIRFT (Shuttle Infrared Telescope Facility) are determined. The following are reviewed: (1) monolithic extrinsic arrays; (2) monolithic intrinsic arrays; (3) charge injection devices; and (4) hybrid arrays.

Instability analysis of charges trapped in the oxide of metal-ultra thin oxide-semiconductor structures

NASA Astrophysics Data System (ADS)

Aziz, A.; Kassmi, K.; Maimouni, R.; Olivié, F.; Sarrabayrouse, G.; Martinez, A.

2005-09-01

In this paper, we present the theoretical and experimental results of the influence of a charge trapped in ultra-thin oxide of metal/ultra-thin oxide/semiconductor structures (MOS) on the I(Vg) current-voltage characteristics when the conduction is of the Fowler-Nordheim (FN) tunneling type. The charge, which is negative, is trapped near the cathode (metal/oxide interface) after constant current injection by the metal (Vg<0). Of particular interest is the influence on the Δ Vg(Vg) shift over the whole I(Vg) characteristic at high field (greater than the injection field (>12.5 MV/cm)). It is shown that the charge centroid varies linearly with respect to the voltage Vg. The behavior at low field (<12.5 MV/cm) is analyzed in référence A. Aziz, K. Kassmi, Ka. Kassmi, F. Olivié, Semicond. Sci. Technol. 19, 877 (2004) and considers that the trapped charge centroid is fixed. The results obtained make it possible to analyze the influence of the injected charge and the applied field on the centroid position of the trapped charge, and to highlight the charge instability in the ultra-thin oxide of MOS structures.

On Practical Charge Injection at the Metal/Organic Semiconductor Interface

PubMed Central

Kumatani, Akichika; Li, Yun; Darmawan, Peter; Minari, Takeo; Tsukagoshi, Kazuhito

2013-01-01

We have revealed practical charge injection at metal and organic semiconductor interface in organic field effect transistor configurations. We have developed a facile interface structure that consisted of double-layer electrodes in order to investigate the efficiency through contact metal dependence. The metal interlayer with few nanometers thickness between electrode and organic semiconductor drastically reduces the contact resistance at the interface. The improvement has clearly obtained when the interlayer is a metal with lower standard electrode potential of contact metals than large work function of the contact metals. The electrode potential also implies that the most dominant effect on the mechanism at the contact interface is induced by charge transfer. This mechanism represents a step forward towards understanding the fundamental physics of intrinsic charge injection in all organic devices. PMID:23293741

Stackable differential mobility analyzer for aerosol measurement

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cheng, Meng-Dawn; Chen, Da-Ren

2007-05-08

A multi-stage differential mobility analyzer (MDMA) for aerosol measurements includes a first electrode or grid including at least one inlet or injection slit for receiving an aerosol including charged particles for analysis. A second electrode or grid is spaced apart from the first electrode. The second electrode has at least one sampling outlet disposed at a plurality different distances along its length. A volume between the first and the second electrode or grid between the inlet or injection slit and a distal one of the plurality of sampling outlets forms a classifying region, the first and second electrodes for chargingmore » to suitable potentials to create an electric field within the classifying region. At least one inlet or injection slit in the second electrode receives a sheath gas flow into an upstream end of the classifying region, wherein each sampling outlet functions as an independent DMA stage and classifies different size ranges of charged particles based on electric mobility simultaneously.« less

A mechanism of charge transport in electroluminescent structures consisting of porous silicon and single-crystal silicon

DOE Office of Scientific and Technical Information (OSTI.GOV)

Evtukh, A. A., E-mail: dept_5@isp.kiev.ua; Kaganovich, E. B.; Manoilov, E. G.

2006-02-15

Electroluminescent structures that emit in the visible region of the spectrum and are based on porous silicon (por-Si) formed on the p-Si substrate electrolytically using an internal current source are fabricated. The photoluminescent and electroluminescent properties, as well as the current-and capacitance-voltage characteristics of the structures are studied. Electroluminescence is observed only if the forward bias voltage is applied to the structure; the electroluminescence mechanism is based on the injection and is related to the radiative recombination of electrons and holes in quantum-dimensional Si nanocrystals. The injection of holes is controlled by the condition of their accumulation in the space-chargemore » region of p-Si and by a comparatively low concentration of electronic states at the por-Si/p-Si interface. The charge transport in por-Si is caused by the direct tunneling of charge carriers between the quantum-mechanical levels, which is ensured by an appreciable number of quantum-dimensional Si nanocrystals. The leakage currents are low as a result of a small variance in the sizes of Si nanocrystals and the absence of comparatively large nanocrystals.« less

Stationary to nonstationary transition in crossed-field devices

DOE Office of Scientific and Technical Information (OSTI.GOV)

Marini, Samuel; Rizzato, Felipe B.; Pakter, Renato

2016-03-15

The previous results based on numerical simulations showed that a cold electron beam injected in a crossed field gap does not reach a time independent stationary state in the space charge limited regime [P. J. Christenson and Y. Y. Lau, Phys. Plasmas 1, 3725 (1994)]. In this work, the effect of finite injection temperature in the transition from stationary to nonstationary states is investigated. A fully kinetic model for the electron flow is derived and used to determine the possible stationary states of the system. It is found that although there is always a stationary solution for any set ofmore » parameters, depending on the injection temperature the electron flow becomes very sensitive to fluctuations and the stationary state is never reached. By investigating the nonlinear dynamics of a characteristic electron, a theory based on a single free parameter is constructed to predict when the transition between stationary and nonstationary states occurs. In agreement with the previous numerical results, the theory indicates that for vanishing temperatures the system never reaches the time independent stationary state in the space charge limited regime. Nevertheless, as the injection temperature is raised it is found a broad range of system parameters for which the stationary state is indeed attained. By properly adjusting the free parameter in the theory, one can be able to describe, to a very good accuracy, when the transition occurs.« less

Mixed mode control method and engine using same

DOEpatents

Kesse, Mary L [Peoria, IL; Duffy, Kevin P [Metamora, IL

2007-04-10

A method of mixed mode operation of an internal combustion engine includes the steps of controlling a homogeneous charge combustion event timing in a given engine cycle, and controlling a conventional charge injection event to be at least a predetermined time after the homogeneous charge combustion event. An internal combustion engine is provided, including an electronic controller having a computer readable medium with a combustion timing control algorithm recorded thereon, the control algorithm including means for controlling a homogeneous charge combustion event timing and means for controlling a conventional injection event timing to be at least a predetermined time from the homogeneous charge combustion event.

Dual nozzle single pump fuel injection system

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gonzalez, C.

1992-02-25

This patent describes an improvement in a fuel injection system in a stratified charge hybrid internal combustion engine including a main combustion chamber, a precombustion chamber connected with the main chamber, fuel injectors in the main combustion chamber and precombustion chamber which open at higher and lower pressure levels respectively to sequentially inject fuel into the prechamber and the main chamber, timed spark ignition means in the prechamber for ignition of the fuel-air mixture therein, and an engine driven and timed fuel injection pump having a variable output capacity that varies with power level position, the injection pump is suppliedmore » by a low pressure charging pump. The improvement comprises: a shuttle valve including a bore therein; a shuttle spool means positioned within the bore defining a prechamber supply chamber on one side thereof and a spool activation chamber on the opposite side thereof the spool means having a first and second position; biasing means urging the spool towards it first position with the spool actuation chamber at its minimum volume; first conduit means connecting charging pressure to the prechamber supply camber in the first position oil the spool means; second conduit means connecting the injection pump to spool actuation chamber; third conduit means connecting the spool actuating chamber with the main injector; forth conduit means connecting the prechamber supply chamber with the prechamber injector; the initial charge from the injection pump actuates the spool means from its fir to its second position.« less

Neutralization of beam-emitting spacecraft by plasma injection

NASA Technical Reports Server (NTRS)

Sasaki, S.; Kawashima, N.; Kuriki, K.; Yanagisawa, M.; Obayashi, T.; Roberts, W. T.; Reasoner, D. L.; Taylor, W. W. L.

1987-01-01

An impulsive plasma injection has been used to study charge neutralization of the Space Shuttle Orbiter while it was emitting an electron beam into space. This investigation was performed by Space Experiments with Particle Accelerators on Spacelab-1. A plasma consisting of 10 to the 19th argon ion-electron pairs was injected into space for 1 ms while an electron beam was also being emitted into space. The electron beam energy and current were as high as 5 keV and 300 mA. While the orbiter potential was positive before the plasma injection and began to decrease during the plasma injection, it was near zero for 6 to 20 ms after the plasma injection. The recovery time to the initial level of charging varied from 10 to 100 ms. In a laboratory test in a large space chamber using the same flight hardware, the neutralization time was 8-17 ms and the recovery time was 11-20 ms. The long duration of the neutralization effect in space can be explained by a model of diffusion of the cold plasma which is produced near the Orbiter by charge exchange between the neutral argon atoms and the energetic argon ions during plasma injection.

Promoting Charge Separation and Injection by Optimizing the Interfaces of GaN:ZnO Photoanode for Efficient Solar Water Oxidation.

PubMed

Wang, Zhiliang; Zong, Xu; Gao, Yuying; Han, Jingfeng; Xu, Zhiqiang; Li, Zheng; Ding, Chunmei; Wang, Shengyang; Li, Can

2017-09-13

Photoelectrochemical water splitting provides an attractive way to store solar energy in molecular hydrogen as a kind of sustainable fuel. To achieve high solar conversion efficiency, the most stringent criteria are effective charge separation and injection in electrodes. Herein, efficient photoelectrochemical water oxidation is realized by optimizing charge separation and surface charge transfer of GaN:ZnO photoanode. The charge separation can be greatly improved through modified moisture-assisted nitridation and HCl acid treatment, by which the interfaces in GaN:ZnO solid solution particles are optimized and recombination centers existing at the interfaces are depressed in GaN:ZnO photoanode. Moreover, a multimetal phosphide of NiCoFeP was employed as water oxidation cocatalyst to improve the charge injection at the photoanode/electrolyte interface. Consequently, it significantly decreases the overpotential and brings the photocurrent to a benchmark of 3.9 mA cm -2 at 1.23 V vs RHE and a solar conversion efficiency over 1% was obtained.

Hole injection and dielectric breakdown in 6H-SiC and 4H-SiC metal-oxide-semiconductor structures during substrate electron injection via Fowler-Nordheim tunneling

NASA Astrophysics Data System (ADS)

Samanta, Piyas; Mandal, Krishna C.

2015-12-01

Hole injection into silicon dioxide (SiO2) films (8-40 nm thick) is investigated for the first time during substrate electron injection via Fowler-Nordheim (FN) tunneling in n-type 4H- and 6H-SiC (silicon carbide) based metal-oxide-semiconductor (MOS) structures at a wide range of temperatures (T) between 298 and 598 K and oxide electric fields Eox from 6 to 10 MV/cm. Holes are generated in heavily doped n-type polycrystalline silicon (n+ -polySi) gate serving as the anode as well as in the bulk silicon dioxide (SiO2) film via hot-electron initiated band-to-band ionization (BTBI). In absence of oxide trapped charges, it is shown that at a given temperature, the hole injection rates from either of the above two mechanisms are higher in n-4H-SiC MOS devices than those in n-6H-SiC MOS structures when compared at a given Eox and SiO2 thickness (tox). On the other hand, relative to n-4H-SiC devices, n-6H-SiC structures exhibit higher hole injection rates for a given tox during substrate electron injection at a given FN current density je,FN throughout the temperature range studied here. These two observations clearly reveal that the substrate material (n-6H-SiC and n-4H-SiC) dependencies on time-to-breakdown (tBD) or injected charge (electron) to breakdown (QBD) of the SiO2 film depend on the mode of FN injections (constant field/voltage and current) from the substrate which is further verified from the rigorous device simulation as well.

Effect of Organic Blocking Layer on the Energy Storage Characteristics of High-Permittivity Sol-Gel Thin Film Based on Neat 2-Cyanoethyltrimethoxysilane

NASA Astrophysics Data System (ADS)

Kim, Yunsang; Kathaperumal, Mohanalingam; Pan, Ming-Jen; Perry, Joseph

2014-03-01

Organic-inorganic hybrid sol-gel materials with polar groups that can undergo reorientational polarization provide a potential route to dielectric materials for energy storage. We have investigated the influence of nanoscale polymeric layer on dielectric and energy storage properties of 2-cyanoethyltrimethoxysilane (CNETMS) films. Two polymeric materials, fluoropolymer (CYTOP) and poly(p-phenylene oxide, PPO), are examined as potential materials to control charge injection from electrical contacts into CNETMS films by means of a potential barrier, whose width and height are defined by thickness and permittivity. Blocking layers ranging from 20 nm to 200 nm were deposited on CNETMS films by spin casting and subjected to thermal treatment. Polarization-electric field measurements show 30% increase in extractable energy density with PPO/CNETMS bilayers, relative to CNETMS alone, due to improved breakdown strength. Conduction current of the bilayers indicate that onset of charge conduction at high field is much delayed, which can be translated into effective suppression of charge injection and probability of breakdown events. The results will be discussed in regards to film morphology, field partitioning, width and height of potential barrier, charge trapping and loss of bilayers.

Computational study of interfacial charge transfer complexes of 2-anthroic acid adsorbed on a titania nanocluster for direct injection solar cells

NASA Astrophysics Data System (ADS)

Manzhos, Sergei; Kotsis, Konstantinos

2016-09-01

Adsorption and light absorption properties of interfacial charge transfer complexes of 2-anthroic acid and titania, promising for direct-injection solar cells, are studied ab initio. The formation of interfacial charge transfer bands is observed. The intensity of visible absorption is relatively low, highlighting a key challenge facing direct injection cells. We show that the popular strategy of using a lower level of theory for geometry optimization followed by single point calculations of adsorption or optical properties introduces significant errors which have been underappreciated: by up to 3 eV in adsorption energies, by up to 5 times in light absorption intensity.

A SONOS device with a separated charge trapping layer for improvement of charge injection

NASA Astrophysics Data System (ADS)

Ahn, Jae-Hyuk; Moon, Dong-Il; Ko, Seung-Won; Kim, Chang-Hoon; Kim, Jee-Yeon; Kim, Moon-Seok; Seol, Myeong-Lok; Moon, Joon-Bae; Choi, Ji-Min; Oh, Jae-Sub; Choi, Sung-Jin; Choi, Yang-Kyu

2017-03-01

A charge trapping layer that is separated from the primary gate dielectric is implemented on a FinFET SONOS structure. By virtue of the reduced effective oxide thickness of the primary gate dielectric, a strong gate-to-channel coupling is obtained and thus short-channel effects in the proposed device are effectively suppressed. Moreover, a high program/erase speed and a large shift in the threshold voltage are achieved due to the improved charge injection by the reduced effective oxide thickness. The proposed structure has potential for use in high speed flash memory.

Determination of somatropin charged variants by capillary zone electrophoresis - optimisation, verification and implementation of the European pharmacopoeia method.

PubMed

Storms, S M; Feltus, A; Barker, A R; Joly, M-A; Girard, M

2009-03-01

Measurement of somatropin charged variants by isoelectric focusing was replaced with capillary zone electrophoresis in the January 2006 European Pharmacopoeia Supplement 5.3, based on results from an interlaboratory collaborative study. Due to incompatibilities and method-robustness issues encountered prior to verification, a number of method parameters required optimisation. As the use of a diode array detector at 195 nm or 200 nm led to a loss of resolution, a variable wavelength detector using a 200 nm filter was employed. Improved injection repeatability was obtained by increasing the injection time and pressure, and changing the sample diluent from water to running buffer. Finally, definition of capillary pre-treatment and rinse procedures resulted in more consistent separations over time. Method verification data are presented demonstrating linearity, specificity, repeatability, intermediate precision, limit of quantitation, sample stability, solution stability, and robustness. Based on these experiments, several modifications to the current method have been recommended and incorporated into the European Pharmacopoeia to help improve method performance across laboratories globally.

Bio-inspired Nanoparticulate Medical Glues for Minimally Invasive Tissue Repair

PubMed Central

Lee, Yuhan; Xu, Chenjie; Sebastin, Monisha; Lee, Albert; Holwell, Nathan; Xu, Calvin; Miranda-Nieves, David; Mu, Luye; Lin, Charles

2015-01-01

Delivery of tissue glues through small-bore needles or trocars is critical for sealing holes, affixing medical devices, or attaching tissues together during minimally invasive surgeries. Inspired by the granule-packaged glue delivery system of sandcastle worms, we have developed a nanoparticulate formulation of a viscous hydrophobic light-activated adhesive based on poly(glycerol sebacate)-acrylate. Negatively charged alginate was used to stabilize the nanoparticulate surface to significantly reduce its viscosity and to maximize injectability through small-bore needles. The nanoparticulate glues can be concentrated to ~30w/v% dispersions in water that remain localized following injection. With the trigger of a positively charged polymer (e.g., protamine), the nanoparticulate glues can quickly assemble into a viscous glue that exhibits rheological, mechanical and adhesive properties resembling the native poly(glycerol sebacate)-acrylate based glues. This platform should be useful to enable the delivery of viscous glues to augment or replace sutures and staples during minimally invasive procedures. PMID:26227833

Photoactive layer based on T-shaped benzimidazole dyes used for solar cell: from photoelectric properties to molecular design

NASA Astrophysics Data System (ADS)

Xu, Beibei; Li, Yuanzuo; Song, Peng; Ma, Fengcai; Sun, Mengtao

2017-03-01

Three benzimidazole-based organic dyes, possessing the same triphenylamine donors and cyanoacrylic acid acceptors with the bithiophene π-bridges combined in different nuclear positions of benzimidazole, were investigated in the utility of dye-sensitizer solar cells. The structure, molecular orbital and energy, absorption spectra and some important parameters (such as light harvesting efficiency (LHE), electron injection driving force, the electron injection time, chemical reactivity parameters, vertical dipole moment as well as interaction models of dye-I2) were obtained according to Newns-Anderson model and DFT calculation. The process and strength of charge transfer and separation were visualized with charge different density and index of spatial extent (S, D and Δq). Current work paid attention to the new T-shaped dyes to reveal the relation between the structure and photoelectric performance. Furthermore, nine dyes (substitution of alkyl chains and π-bridges) have been designed and characterized to screen promising sensitizer candidates with excellent photo-electronic properties.

Bioinspired Nanoparticulate Medical Glues for Minimally Invasive Tissue Repair.

PubMed

Lee, Yuhan; Xu, Chenjie; Sebastin, Monisha; Lee, Albert; Holwell, Nathan; Xu, Calvin; Miranda Nieves, David; Mu, Luye; Langer, Robert S; Lin, Charles; Karp, Jeffrey M

2015-11-18

Delivery of tissue glues through small-bore needles or trocars is critical for sealing holes, affixing medical devices, or attaching tissues together during minimally invasive surgeries. Inspired by the granule-packaged glue delivery system of sandcastle worms, a nanoparticulate formulation of a viscous hydrophobic light-activated adhesive based on poly(glycerol sebacate)-acrylate is developed. Negatively charged alginate is used to stabilize the nanoparticulate surface to significantly reduce its viscosity and to maximize injectability through small-bore needles. The nanoparticulate glues can be concentrated to ≈30 w/v% dispersions in water that remain localized following injection. With the trigger of a positively charged polymer (e.g., protamine), the nanoparticulate glues can quickly assemble into a viscous glue that exhibits rheological, mechanical, and adhesive properties resembling the native poly(glycerol sebacate)-acrylate based glues. This platform should be useful to enable the delivery of viscous glues to augment or replace sutures and staples during minimally invasive procedures. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Charge injection and discharging of Si nanocrystals and arrays by atomic force microscopy

NASA Technical Reports Server (NTRS)

Boer, E.; Ostraat, M.; Brongersma, M. L.; Flagan, R. C.; Atwater, H. A.

2000-01-01

Charge injection and storage in dense arrays of silicon nanocrystals in SiO(sub 2) is a critical aspect of the performance of potential nanocrystal flash memory structures. The ultimate goal for this class of devices is few-or single- electron storage in a small number of nanocrystal elements.

Electrochemical Evaluations of Fractal Microelectrodes for Energy Efficient Neurostimulation.

PubMed

Park, Hyunsu; Takmakov, Pavel; Lee, Hyowon

2018-03-12

Advancements in microfabrication has enabled manufacturing of microscopic neurostimulation electrodes with smaller footprint than ever possible. The smaller electrodes can potentially reduce tissue damage and allow better spatial resolution for neural stimulation. Although electrodes of any shape can easily be fabricated, substantial effort have been focused on identification and characterization of new materials and surface morphology for efficient charge injection, while maintaining simple circular or rectangular Euclidean electrode geometries. In this work we provide a systematic electrochemical evaluation of charge injection capacities of serpentine and fractal-shaped platinum microelectrodes and compare their performance with traditional circular microelectrodes. Our findings indicate that the increase in electrode perimeter leads to an increase in maximum charge injection capacity. Furthermore, we found that the electrode geometry can have even more significant impact on electrode performance than having a larger perimeter for a given surface area. The fractal-shaped microelectrodes, despite having smaller perimeter than other designs, demonstrated superior charge injection capacity. Our results suggest that electrode design can significantly affect both Faradaic and non-Faradaic electrochemical processes, which may be optimized to enable a more energy efficient design for neurostimulation.

Opto-electronic characterization of third-generation solar cells.

PubMed

Neukom, Martin; Züfle, Simon; Jenatsch, Sandra; Ruhstaller, Beat

2018-01-01

We present an overview of opto-electronic characterization techniques for solar cells including light-induced charge extraction by linearly increasing voltage, impedance spectroscopy, transient photovoltage, charge extraction and more. Guidelines for the interpretation of experimental results are derived based on charge drift-diffusion simulations of solar cells with common performance limitations. It is investigated how nonidealities like charge injection barriers, traps and low mobilities among others manifest themselves in each of the studied cell characterization techniques. Moreover, comprehensive parameter extraction for an organic bulk-heterojunction solar cell comprising PCDTBT:PC 70 BM is demonstrated. The simulations reproduce measured results of 9 different experimental techniques. Parameter correlation is minimized due to the combination of various techniques. Thereby a route to comprehensive and accurate parameter extraction is identified.

Simulation of radial expansion of an electron beam injected into a background plasma

NASA Technical Reports Server (NTRS)

Koga, J.; Lin, C. S.

1989-01-01

A 2-D electrostatic particle code was used to study the beam radial expansion of a nonrelativistic electron beam injected from an isolated equipotential conductor into a background plasma. The simulations indicate that the beam radius is generally proportional to the beam electron gyroradius when the conductor is charged to a large potential. The simulations also suggest that the charge buildup at the beam stagnation point causes the beam radial expansion. From a survey of the simulation results, it is found that the ratio of the beam radius to the beam electron gyroradius increases with the square root of beam density and decreases inversely with beam injection velocity. This dependence is explained in terms of the ratio of the beam electron Debye length to the ambient electron Debye length. These results are most applicable to the SEPAC electron beam injection experiments from Spacelab 1, where high charging potential was observed.

Engine combustion control via fuel reactivity stratification

DOEpatents

Reitz, Rolf Deneys; Hanson, Reed M.; Splitter, Derek A.; Kokjohn, Sage L.

2015-07-14

A compression ignition engine uses two or more fuel charges having two or more reactivities to control the timing and duration of combustion. In a preferred implementation, a lower-reactivity fuel charge is injected or otherwise introduced into the combustion chamber, preferably sufficiently early that it becomes at least substantially homogeneously dispersed within the chamber before a subsequent injection is made. One or more subsequent injections of higher-reactivity fuel charges are then made, and these preferably distribute the higher-reactivity matter within the lower-reactivity chamber space such that combustion begins in the higher-reactivity regions, and with the lower-reactivity regions following thereafter. By appropriately choosing the reactivities of the charges, their relative amounts, and their timing, combustion can be tailored to achieve optimal power output (and thus fuel efficiency), at controlled temperatures (and thus controlled NOx), and with controlled equivalence ratios (and thus controlled soot).

Engine combustion control via fuel reactivity stratification

DOEpatents

Reitz, Rolf Deneys; Hanson, Reed M.; Splitter, Derek A.; Kokjohn, Sage L.

2016-06-28

A compression ignition engine uses two or more fuel charges having two or more reactivities to control the timing and duration of combustion. In a preferred implementation, a lower-reactivity fuel charge is injected or otherwise introduced into the combustion chamber, preferably sufficiently early that it becomes at least substantially homogeneously dispersed within the chamber before a subsequent injection is made. One or more subsequent injections of higher-reactivity fuel charges are then made, and these preferably distribute the higher-reactivity matter within the lower-reactivity chamber space such that combustion begins in the higher-reactivity regions, and with the lower-reactivity regions following thereafter. By appropriately choosing the reactivities of the charges, their relative amounts, and their timing, combustion can be tailored to achieve optimal power output (and thus fuel efficiency), at controlled temperatures (and thus controlled NOx), and with controlled equivalence ratios (and thus controlled soot).

Engine combustion control via fuel reactivity stratification

DOEpatents

Reitz, Rolf Deneys; Hanson, Reed M; Splitter, Derek A; Kokjohn, Sage L

2013-12-31

A compression ignition engine uses two or more fuel charges having two or more reactivities to control the timing and duration of combustion. In a preferred implementation, a lower-reactivity fuel charge is injected or otherwise introduced into the combustion chamber, preferably sufficiently early that it becomes at least substantially homogeneously dispersed within the chamber before a subsequent injection is made. One or more subsequent injections of higher-reactivity fuel charges are then made, and these preferably distribute the higher-reactivity matter within the lower-reactivity chamber space such that combustion begins in the higher-reactivity regions, and with the lower-reactivity regions following thereafter. By appropriately choose the reactivities of the charges, their relative amounts, and their timing, combustion can be tailored to achieve optimal power output (and thus fuel efficiency), at controlled temperatures (and thus controlled NOx), and with controlled equivalence ratios (and thus controlled soot).

Extraction method of interfacial injected charges for SiC power MOSFETs

NASA Astrophysics Data System (ADS)

Wei, Jiaxing; Liu, Siyang; Li, Sheng; Song, Haiyang; Chen, Xin; Li, Ting; Fang, Jiong; Sun, Weifeng

2018-01-01

An improved novel extraction method which can characterize the injected charges along the gate oxide interface for silicon carbide (SiC) power metal-oxide-semiconductor field-effect transistors (MOSFETs) is proposed. According to the different interface situations of the channel region and the junction FET (JFET) region, the gate capacitance versus gate voltage (Cg-Vg) curve of the device can be divided into three relatively independent parts, through which the locations and the types of the charges injected in to the oxide above the interface can be distinguished. Moreover, the densities of these charges can also be calculated by the amplitudes of the shifts in the Cg-Vg curve. The correctness of this method is proved by TCAD simulations. Moreover, experiments on devices stressed by unclamped-inductive-switching (UIS) stress and negative bias temperature stress (NBTS) are performed to verify the validity of this method.

Towards electrical spin injection into LaAlO3-SrTiO3.

PubMed

Bibes, M; Reyren, N; Lesne, E; George, J-M; Deranlot, C; Collin, S; Barthélémy, A; Jaffrès, H

2012-10-28

Future spintronics devices will be built from elemental blocks allowing the electrical injection, propagation, manipulation and detection of spin-based information. Owing to their remarkable multi-functional and strongly correlated character, oxide materials already provide such building blocks for charge-based devices such as ferroelectric field-effect transistors (FETs), as well as for spin-based two-terminal devices such as magnetic tunnel junctions, with giant responses in both cases. Until now, the lack of suitable channel materials and the uncertainty of spin-injection conditions in these compounds had however prevented the exploration of similar giant responses in oxide-based lateral spin transport structures. In this paper, we discuss the potential of oxide-based spin FETs and report magnetotransport data that suggest electrical spin injection into the LaAlO(3)-SrTiO(3) interface system. In a local, three-terminal measurement scheme, we analyse the voltage variation associated with the precession of the injected spin accumulation driven by perpendicular or longitudinal magnetic fields (Hanle and 'inverted' Hanle effects). The spin accumulation signal appears to be much larger than expected, probably owing to amplification effects by resonant tunnelling through localized states in the LaAlO(3). We give perspectives on how to achieve direct spin injection with increased detection efficiency, as well on the implementation of efficient top gating schemes for spin manipulation.

Construction of a Direct Water-Injected Two-Stroke Engine for Phased Direct Fuel Injection-High Pressure Charging Investigations

NASA Technical Reports Server (NTRS)

Somsel, James P.

1998-01-01

The development of a water injected Orbital Combustion Process (OCP) engine was conducted to assess the viability of using the powerplant for high altitude NASA aircraft and General Aviation (GA) applications. An OCP direct fuel injected, 1.2 liter, three cylinder, two-stroke engine has been enhanced to independently inject water directly into the combustion chamber. The engine currently demonstrates low brake specific fuel consumption capability and an excellent power to weight ratio. With direct water injection, significant improvements can be made to engine power, to knock limits/ignition advance timing, and to engine NO(x) emissions. The principal aim of the testing was to validate a cyclic model developed by the Systems Analysis Branch at NASA Ames Research Center. The work is a continuation of Ames' investigations into a Phased Direct Fuel Injection Engine with High Pressure Charging (PDFI-ITPC).

Dust particle injector for hypervelocity accelerators provides high charge-to-mass ratio

NASA Technical Reports Server (NTRS)

Berg, O. E.

1966-01-01

Injector imparts a high charge-to-mass ratio to microparticles and injects them into an electrostatic accelerator so that the particles are accelerated to meteoric speeds. It employs relatively large masses in the anode and cathode structures with a relatively wide separation, thus permitting a large increase in the allowable injection voltages.

Solid state carbon nanotube device for controllable trion electroluminescence emission

NASA Astrophysics Data System (ADS)

Liang, Shuang; Ma, Ze; Wei, Nan; Liu, Huaping; Wang, Sheng; Peng, Lian-Mao

2016-03-01

Semiconducting carbon nanotubes (CNTs) have a direct chirality-dependent bandgap and reduced dimensionality-related quantum confinement effects, which are closely related to the performance of optoelectronic devices. Here, taking advantage of the large energy separations between neutral singlet excitons and charged excitons, i.e. trions in CNTs, we have achieved for the first time all trion electroluminescence (EL) emission from chirality-sorted (8,3) and (8,4) CNT-based solid state devices. We showed that strong trion emission can be obtained as a result of localized impact excitation and electrically injected holes, with an estimated efficiency of ~5 × 10-4 photons per injected hole. The importance of contact-controlled carrier injection (including symmetric and asymmetric contact configurations) and EL spectral stability for gradually increasing bias were also investigated. The realization of electrically induced pure trion emission opens up a new opportunity for CNT film-based optoelectronic devices, providing a new degree of freedom in controlling the devices to extend potential applications in spin or magnetic optoelectronics fields.Semiconducting carbon nanotubes (CNTs) have a direct chirality-dependent bandgap and reduced dimensionality-related quantum confinement effects, which are closely related to the performance of optoelectronic devices. Here, taking advantage of the large energy separations between neutral singlet excitons and charged excitons, i.e. trions in CNTs, we have achieved for the first time all trion electroluminescence (EL) emission from chirality-sorted (8,3) and (8,4) CNT-based solid state devices. We showed that strong trion emission can be obtained as a result of localized impact excitation and electrically injected holes, with an estimated efficiency of ~5 × 10-4 photons per injected hole. The importance of contact-controlled carrier injection (including symmetric and asymmetric contact configurations) and EL spectral stability for gradually increasing bias were also investigated. The realization of electrically induced pure trion emission opens up a new opportunity for CNT film-based optoelectronic devices, providing a new degree of freedom in controlling the devices to extend potential applications in spin or magnetic optoelectronics fields. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr07468a

Microcontact printing of self-assembled monolayers to pattern the light-emission of polymeric light-emitting diodes

NASA Astrophysics Data System (ADS)

Brondijk, J. J.; Li, X.; Akkerman, H. B.; Blom, P. W. M.; de Boer, B.

2009-04-01

By patterning a self-assembled monolayer (SAM) of thiolated molecules with opposing dipole moments on a gold anode of a polymer light-emitting diode (PLED), the charge injection and, therefore, the light-emission of the device can be controlled with a micrometer-scale resolution. Gold surfaces were modified with SAMs based on alkanethiols and perfluorinated alkanethiols, applied by microcontact printing, and their work functions have been measured. The molecules form a chemisorbed monolayer of only ˜1.5 nm on the gold surface, thereby locally changing the work function of the metal. Kelvin probe measurements show that the local work function can be tuned from 4.3 to 5.5 eV, which implies that this anode can be used as a hole blocking electrode or as a hole injecting electrode, respectively, in PLEDs based on poly( p-phenylene vinylene) (PPV) derivatives. By microcontact printing of SAMs with opposing dipole moments, the work function was locally modified and the charge injection in the PLED could be controlled down to the micrometer length scale. Consequently, the local light-emission exhibits a high contrast. Microcontact printing of SAMs is a simple and inexpensive method to pattern, with micrometer resolution, the light-emission for low-end applications like static displays.

PMMA interlayer-modulated memory effects by space charge polarization in resistive switching based on CuSCN-nanopyramids/ZnO-nanorods p-n heterojunction

PubMed Central

Cheng, Baochang; Zhao, Jie; Xiao, Li; Cai, Qiangsheng; Guo, Rui; Xiao, Yanhe; Lei, Shuijin

2015-01-01

Resistive switching (RS) devices are commonly believed as a promising candidate for next generation nonvolatile resistance random access memory. Here, polymethylmethacrylate (PMMA) interlayer was introduced at the heterointerface of p-CuSCN hollow nanopyramid arrays and n-ZnO nanorod arrays, resulting in a typical bipolar RS behavior. We propose the mechanism of nanostructure trap-induced space charge polarization modulated by PMMA interlayer. At low reverse bias, PMMA insulator can block charges through the heterointerface, and and trapped states are respectively created on both sides of PMMA, resulting in a high resistance state (HRS) due to wider depletion region. At high reverse bias, however, electrons and holes can cross PMMA interlayer by Fowler-Nordeim tunneling due to a massive tilt of energy band, and then inject into the traps of ZnO and CuSCN, respectively. and trapped states are created, resulting in the formation of degenerate semiconductors on both sides of PMMA. Therefore, quantum tunneling and space charge polarization lead to a low resistance state (LRS). At relatively high forward bias, subsequently, the trapped states of and are recreated due to the opposite injection of charges, resulting in a recovery of HRS. The introduction of insulating interlayer at heterointerface, point a way to develop next-generation nonvolatile memories. PMID:26648249

Electron transfer processes occurring on platinum neural stimulating electrodes: pulsing experiments for cathodic-first/charge-balanced/biphasic pulses for 0.566 ≤ k ≤ 2.3 in oxygenated and deoxygenated sulfuric acid.

PubMed

Kumsa, Doe W; Montague, Fred W; Hudak, Eric M; Mortimer, J Thomas

2016-10-01

The application of a train of cathodic-first/charge-balanced/biphasic pulses applied to a platinum electrode resulted in a positive creep of the anodic phase potential that increases with increasing charge injection but reaches a steady-state value before 1000 pulses have been delivered. The increase follows from the fact that charge going into irreversible reactions occurring during the anodic phase must equal the charge going into irreversible reactions during the cathodic phase for charge-balanced pulses. In an oxygenated electrolyte the drift of the measured positive potential moved into the platinum oxidation region of the i(V e) profile when the charge injection level exceeds k = 1.75. Platinum dissolution may occur in this region and k = 1.75 defines a boundary between damaging and non-damaging levels on the Shannon Plot. In a very low oxygen environment, the positive potential remained below the platinum oxidation region for the highest charge injection values studied, k = 2.3. The results support the hypothesis that platinum dissolution is the defining factor for the Shannon limit, k = 1.75. Numerous instrumentation issues were encountered in the course of making measurements. The solutions to these issues are provided.

Simulation of bipolar charge transport in nanocomposite polymer films

NASA Astrophysics Data System (ADS)

Lean, Meng H.; Chu, Wei-Ping L.

2015-03-01

This paper describes 3D particle-in-cell simulation of bipolar charge injection and transport through nanocomposite film comprised of ferroelectric ceramic nanofillers in an amorphous polymer matrix. The classical electrical double layer (EDL) model for a monopolar core is extended (eEDL) to represent the nanofiller by replacing it with a dipolar core. Charge injection at the electrodes assumes metal-polymer Schottky emission at low to moderate fields and Fowler-Nordheim tunneling at high fields. Injected particles migrate via field-dependent Poole-Frenkel mobility and recombine with Monte Carlo selection. The simulation algorithm uses a boundary integral equation method for solution of the Poisson equation coupled with a second-order predictor-corrector scheme for robust time integration of the equations of motion. The stability criterion of the explicit algorithm conforms to the Courant-Friedrichs-Levy limit assuring robust and rapid convergence. The model is capable of simulating a wide dynamic range spanning leakage current to pre-breakdown. Simulation results for BaTiO3 nanofiller in amorphous polymer matrix indicate that charge transport behavior depend on nanoparticle polarization with anti-parallel orientation showing the highest leakage conduction and therefore lowest level of charge trapping in the interaction zone. Charge recombination is also highest, at the cost of reduced leakage conduction charge. The eEDL model predicts the meandering pathways of charge particle trajectories.

The impact of the Fermi-Dirac distribution on charge injection at metal/organic interfaces.

PubMed

Wang, Z B; Helander, M G; Greiner, M T; Lu, Z H

2010-05-07

The Fermi level has historically been assumed to be the only energy-level from which carriers are injected at metal/semiconductor interfaces. In traditional semiconductor device physics, this approximation is reasonable as the thermal distribution of delocalized states in the semiconductor tends to dominate device characteristics. However, in the case of organic semiconductors the weak intermolecular interactions results in highly localized electronic states, such that the thermal distribution of carriers in the metal may also influence device characteristics. In this work we demonstrate that the Fermi-Dirac distribution of carriers in the metal has a much more significant impact on charge injection at metal/organic interfaces than has previously been assumed. An injection model which includes the effect of the Fermi-Dirac electron distribution was proposed. This model has been tested against experimental data and was found to provide a better physical description of charge injection. This finding indicates that the thermal distribution of electronic states in the metal should, in general, be considered in the study of metal/organic interfaces.

Reduced electron back-injection in Al2O3/AlOx/Al2O3/graphene charge-trap memory devices

NASA Astrophysics Data System (ADS)

Lee, Sejoon; Song, Emil B.; Min Kim, Sung; Lee, Youngmin; Seo, David H.; Seo, Sunae; Wang, Kang L.

2012-12-01

A graphene charge-trap memory is devised using a single-layer graphene channel with an Al2O3/AlOx/Al2O3 oxide stack, where the ion-bombarded AlOx layer is intentionally added to create an abundance of charge-trap sites. The low dielectric constant of AlOx compared to Al2O3 reduces the potential drop in the control oxide Al2O3 and suppresses the electron back-injection from the gate to the charge-storage layer, allowing the memory window of the device to be further extended. This shows that the usage of a lower dielectric constant in the charge-storage layer compared to that of the control oxide layer improves the memory performance for graphene charge-trap memories.

Biased-probe-induced water ion injection into amorphous polymers investigated by electric force microscopy

NASA Astrophysics Data System (ADS)

Knorr, Nikolaus; Rosselli, Silvia; Miteva, Tzenka; Nelles, Gabriele

2009-06-01

Although charging of insulators by atomic force microscopy (AFM) has found widespread interest, often with data storage or nanoxerography in mind, less attention has been paid to the charging mechanism and the nature of the charge. Here we present a systematic study on charging of amorphous polymer films by voltage pulses applied to conducting AFM probes. We find a quadratic space charge limited current law of Kelvin probe force microscopy and electrostatic force microscopy peak volumes in pulse height, offset by a threshold voltage, and a power law in pulse width of positive exponents smaller than one. We interpret the results by a charging mechanism of injection and surface near accumulation of aqueous ions stemming from field induced water adsorption, with threshold voltages linked to the water affinities of the polymers.

Charge Transport in Spiro-OMeTAD Investigated through Space-Charge-Limited Current Measurements

NASA Astrophysics Data System (ADS)

Röhr, Jason A.; Shi, Xingyuan; Haque, Saif A.; Kirchartz, Thomas; Nelson, Jenny

2018-04-01

Extracting charge-carrier mobilities for organic semiconductors from space-charge-limited conduction measurements is complicated in practice by nonideal factors such as trapping in defects and injection barriers. Here, we show that by allowing the bandlike charge-carrier mobility, trap characteristics, injection barrier heights, and the shunt resistance to vary in a multiple-trapping drift-diffusion model, a numerical fit can be obtained to the entire current density-voltage curve from experimental space-charge-limited current measurements on both symmetric and asymmetric 2 ,2',7 ,7' -tetrakis(N ,N -di-4-methoxyphenylamine)-9 ,9' -spirobifluorene (spiro-OMeTAD) single-carrier devices. This approach yields a bandlike mobility that is more than an order of magnitude higher than the effective mobility obtained using analytical approximations, such as the Mott-Gurney law and the moving-electrode equation. It is also shown that where these analytical approximations require a temperature-dependent effective mobility to achieve fits, the numerical model can yield a temperature-, electric-field-, and charge-carrier-density-independent mobility. Finally, we present an analytical model describing trap-limited current flow through a semiconductor in a symmetric single-carrier device. We compare the obtained charge-carrier mobility and trap characteristics from this analytical model to the results from the numerical model, showing excellent agreement. This work shows the importance of accounting for traps and injection barriers explicitly when analyzing current density-voltage curves from space-charge-limited current measurements.

Opto-electronic characterization of third-generation solar cells

PubMed Central

Jenatsch, Sandra

2018-01-01

Abstract We present an overview of opto-electronic characterization techniques for solar cells including light-induced charge extraction by linearly increasing voltage, impedance spectroscopy, transient photovoltage, charge extraction and more. Guidelines for the interpretation of experimental results are derived based on charge drift-diffusion simulations of solar cells with common performance limitations. It is investigated how nonidealities like charge injection barriers, traps and low mobilities among others manifest themselves in each of the studied cell characterization techniques. Moreover, comprehensive parameter extraction for an organic bulk-heterojunction solar cell comprising PCDTBT:PC70BM is demonstrated. The simulations reproduce measured results of 9 different experimental techniques. Parameter correlation is minimized due to the combination of various techniques. Thereby a route to comprehensive and accurate parameter extraction is identified. PMID:29707069

Charge breeding simulations for radioactive ion beam production

DOE Office of Scientific and Technical Information (OSTI.GOV)

Variale, V.; Raino, A. C.; Clauser, T.

2012-02-15

The charge breeding technique is used for radioactive ion beam (RIB) production in order of optimizing the re-acceleration of the radioactive element ions produced by a primary beam in a thick target. Charge breeding is achieved by means of a device capable of increasing the ion charge state from 1+ to a desired value n+. In order to get high intensity RIB, experiments with charge breeding of very high efficiency could be required. To reach this goal, the charge breeding simulation could help to optimize the high charge state production efficiency by finding more proper parameters for the radioactive 1+more » ions. In this paper a device based on an electron beam ion source (EBIS) is considered. In order to study that problem, a code already developed for studying the ion selective containment in an EBIS with RF quadrupoles, BRICTEST, has been modified to simulate the ion charge state breeding rate for different 1+ ion injection conditions. Particularly, the charge breeding simulations for an EBIS with a hollow electron beam have been studied.« less

Improved performance of laser wakefield acceleration by tailored self-truncated ionization injection

NASA Astrophysics Data System (ADS)

Irman, A.; Couperus, J. P.; Debus, A.; Köhler, A.; Krämer, J. M.; Pausch, R.; Zarini, O.; Schramm, U.

2018-04-01

We report on tailoring ionization-induced injection in laser wakefield acceleration so that the electron injection process is self-truncating following the evolution of the plasma bubble. Robust generation of high-quality electron beams with shot-to-shot fluctuations of the beam parameters better than 10% is presented in detail. As a novelty, the scheme was found to enable well-controlled yet simple tuning of the injected charge while preserving acceleration conditions and beam quality. Quasi-monoenergetic electron beams at several 100 MeV energy and 15% relative energy spread were routinely demonstrated with a total charge of the monoenergetic feature reaching 0.5 nC. Finally these unique beam parameters, suggesting unprecedented peak currents of several 10 kA, are systematically related to published data on alternative injection schemes.

SEPAC data analysis in support of the environmental interaction program

NASA Technical Reports Server (NTRS)

Lin, Chin S.

1990-01-01

Injections of nonrelativistic electron beams from an isolated equipotential conductor into a uniform background of plasma and neutral gas were simulated using a two dimensional electrostatic particle code. The ionization effects of spacecraft charging are examined by including interactions of electrons with neutral gas. The simulations show that the conductor charging potential decreases with increasing neutral background density due to the production of secondary electrons near the conductor surface. In the spacecraft wake, the background electrons accelerated towards the charged space craft produced an enhancement of secondary electrons and ions. Simulations run for longer times indicate that the spacecraft potential is further reduced and short wavelength beam-plasma oscillations appear. The results are applied to explain the space craft charging potential measured during the SEPAC experiments from Spacelab 1. A second paper is presented in which a two dimensional electrostatic particle code was used to study the beam radial expansion of a nonrelativistic electron beam injected from an isolated equipotential conductor into a background plasma. The simulations indicate that the beam radius is generally proportional to the beam electron gyroradius when the conductor is charged to a large potential. The simulations also suggest that the charge buildup at the beam stagnation point causes the beam radial expansion. From a survey of the simulation results, it is found that the ratio of the beam radius to the beam electron gyroradius increases with the square root of beam density and decreases inversely with beam injection velocity. This dependence is explained in terms of the ratio of the beam electron Debye length to the ambient electron Debye length. These results are most applicable to the SEPAC electron beam injection experiments from Spacelab 1, where high charging potential was observed.

Fabrication and applications of electrets

NASA Technical Reports Server (NTRS)

Pillai, P. K. C.; Shriver, E. L.

1977-01-01

Permanently charged dielectrics can be made less expensively, faster, and more effectively using improved techniques and materials. Methods include charge injection, Tesla-coil charging, and molten spray. Possible uses include pollution control, low-power sensors, and illumination control.

Charge injection and accumulation in organic light-emitting diode with PEDOT:PSS anode

NASA Astrophysics Data System (ADS)

Weis, Martin; Otsuka, Takako; Taguchi, Dai; Manaka, Takaaki; Iwamoto, Mitsumasa

2015-04-01

Organic light-emitting diode (OLED) displays using flexible substrates have many attractive features. Since transparent conductive oxides do not fit the requirements of flexible devices, conductive polymer poly(3,4-ethylenedioxythiophene):poly(4-styrenesulfonate) (PEDOT:PSS) has been proposed as an alternative. The charge injection and accumulation in OLED devices with PEDOT:PSS anodes are investigated and compared with indium tin oxide anode devices. Higher current density and electroluminescence light intensity are achieved for the OLED device with a PEDOT:PSS anode. The electric field induced second-harmonic generation technique is used for direct observation of temporal evolution of electric fields. It is clearly demonstrated that the improvement in the device performance of the OLED device with a PEDOT:PSS anode is associated with the smooth charge injection and accumulation.

Advanced stratified charge rotary aircraft engine design study

NASA Technical Reports Server (NTRS)

Badgley, P.; Berkowitz, M.; Jones, C.; Myers, D.; Norwood, E.; Pratt, W. B.; Ellis, D. R.; Huggins, G.; Mueller, A.; Hembrey, J. H.

1982-01-01

A technology base of new developments which offered potential benefits to a general aviation engine was compiled and ranked. Using design approaches selected from the ranked list, conceptual design studies were performed of an advanced and a highly advanced engine sized to provide 186/250 shaft Kw/HP under cruise conditions at 7620/25,000 m/ft altitude. These are turbocharged, direct-injected stratified charge engines intended for commercial introduction in the early 1990's. The engine descriptive data includes tables, curves, and drawings depicting configuration, performance, weights and sizes, heat rejection, ignition and fuel injection system descriptions, maintenance requirements, and scaling data for varying power. An engine-airframe integration study of the resulting engines in advanced airframes was performed on a comparative basis with current production type engines. The results show airplane performance, costs, noise & installation factors. The rotary-engined airplanes display substantial improvements over the baseline, including 30 to 35% lower fuel usage.

In-situ analysis of microwave conductivity and impedance spectroscopy for evaluation of charge carrier dynamics at interfaces

NASA Astrophysics Data System (ADS)

Choi, Wookjin; Inoue, Junichi; Tsutsui, Yusuke; Sakurai, Tsuneaki; Seki, Shu

2017-11-01

A unique concerted analysis comprising non-contact microwave conductivity measurements and impedance spectroscopy was developed to simultaneously assess the charge carrier mobility and injection barriers. The frequency dependence of the microwave conductivity as well as the electrical current was analyzed by applying sinusoidal voltage to determine the equivalent circuit parameters. Based on the temperature dependence of the circuit parameters, the energy of the injection barrier was estimated to be 0.4 eV with the Richardson-Schottky model, and the band-like transport was confirmed with the negative temperature coefficient with the β value of 1.4 in the intra-layer conduction of C8-BTBT. In contrast, the increase in the resistance of the C8-BTBT layer with decreasing temperature implied the occurrence of hopping-like transport in the inter-layer conduction of C8-BTBT.

Peripheral Hole Acceptor Moieties on an Organic Dye Improve Dye‐Sensitized Solar Cell Performance

PubMed Central

Hao, Yan; Gabrielsson, Erik; Lohse, Peter William; Yang, Wenxing; Johansson, Erik M. J.; Hagfeldt, Anders

2015-01-01

Investigation of charge transfer dynamics in dye‐sensitized solar cells is of fundamental interest and the control of these dynamics is a key factor for developing more efficient solar cell devices. One possibility for attenuating losses through recombination between injected electrons and oxidized dye molecules is to move the positive charge further away from the metal oxide surface. For this purpose, a metal‐free dye named E6 is developed, in which the chromophore core is tethered to two external triphenylamine (TPA) units. After photoinduced electron injection into TiO2, the remaining hole is rapidly transferred to a peripheral TPA unit. Electron–hole recombination is slowed down by 30% compared to a reference dye without peripheral TPA units. Furthermore, it is found that the added TPA moieties improve the electron blocking effect of the dye, retarding recombination of electrons from TiO2 to the cobalt‐based electrolyte. PMID:27722076

Novel hole transport materials for organic light emitting devices

NASA Astrophysics Data System (ADS)

Shi, Jianmin; Forsythe, Eric; Morton, David

2008-08-01

Organic electronic devices generally have a layered structure with organic materials sandwiched between an anode and a cathode, such organic electronic devices of organic light-emitting diode (OLED), organic photovoltaic (OPV), organic thin-film transistor (OTFT). There are many advantages of these organic electronic devices as compared to silicon-based devices. However, one of key challenge for an organic electronic device is to minimize the charge injection barrier from electrodes to organic materials and improve the charge transport mobility. In order to overcome these circumstances, there are many approaches including, designing organic materials with minimum energy barriers and improving charge transport mobility. Ideally organic materials or complex with Ohmic contact will be the most desired.

Ducted fuel injection: A new approach for lowering soot emissions from direct-injection engines

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mueller, Charles J.; Nilsen, Christopher W.; Ruth, Daniel J.

Designers of direct-injection compression-ignition engines use a variety of strategies to improve the fuel/charge-gas mixture within the combustion chamber for increased efficiency and reduced pollutant emissions. Strategies include the use of high fuel-injection pressures, multiple injections, small injector orifices, flow swirl, long-ignition-delay conditions, and oxygenated fuels. This is the first journal publication paper on a new mixing-enhancement strategy for emissions reduction: ducted fuel injection. The concept involves injecting fuel along the axis of a small cylindrical duct within the combustion chamber, to enhance the mixture in the autoignition zone relative to a conventional free-spray configuration (i.e., a fuel spray thatmore » is not surrounded by a duct). Finally, the results described herein, from initial proof-of-concept experiments conducted in a constant-volume combustion vessel, show dramatically lower soot incandescence from ducted fuel injection than from free sprays over a range of charge-gas conditions that are representative of those in modern direct-injection compression-ignition engines.« less

Ducted fuel injection: A new approach for lowering soot emissions from direct-injection engines

DOE PAGES

Mueller, Charles J.; Nilsen, Christopher W.; Ruth, Daniel J.; ...

2017-07-18

Designers of direct-injection compression-ignition engines use a variety of strategies to improve the fuel/charge-gas mixture within the combustion chamber for increased efficiency and reduced pollutant emissions. Strategies include the use of high fuel-injection pressures, multiple injections, small injector orifices, flow swirl, long-ignition-delay conditions, and oxygenated fuels. This is the first journal publication paper on a new mixing-enhancement strategy for emissions reduction: ducted fuel injection. The concept involves injecting fuel along the axis of a small cylindrical duct within the combustion chamber, to enhance the mixture in the autoignition zone relative to a conventional free-spray configuration (i.e., a fuel spray thatmore » is not surrounded by a duct). Finally, the results described herein, from initial proof-of-concept experiments conducted in a constant-volume combustion vessel, show dramatically lower soot incandescence from ducted fuel injection than from free sprays over a range of charge-gas conditions that are representative of those in modern direct-injection compression-ignition engines.« less

A Charge-Based Low-Power High-SNR Capacitive Sensing Interface Circuit

PubMed Central

Peng, Sheng-Yu; Qureshi, Muhammad S.; Hasler, Paul E.; Basu, Arindam; Degertekin, F. L.

2008-01-01

This paper describes a low-power approach to capacitive sensing that achieves a high signal-to-noise ratio. The circuit is composed of a capacitive feedback charge amplifier and a charge adaptation circuit. Without the adaptation circuit, the charge amplifier only consumes 1 μW to achieve the audio band SNR of 69.34dB. An adaptation scheme using Fowler-Nordheim tunneling and channel hot electron injection mechanisms to stabilize the DC output voltage is demonstrated. This scheme provides a very low frequency pole at 0.2Hz. The measured noise spectrums show that this slow-time scale adaptation does not degrade the circuit performance. The DC path can also be provided by a large feedback resistance without causing extra power consumption. A charge amplifier with a MOS-bipolar pseudo-resistor feedback scheme is interfaced with a capacitive micromachined ultrasonic transducer to demonstrate the feasibility of this approach for ultrasound applications. PMID:18787650

Quantitative Analysis of Charge Injection and Discharging of Si Nanocrystals and Arrays by Electrostatic Force Microscopy

NASA Technical Reports Server (NTRS)

Bell, L. D.; Boer, E.; Ostraat, M.; Brongersma, M. L.; Flagan, R. C.; Atwater, H. A.

2000-01-01

NASA requirements for computing and memory for microspacecraft emphasize high density, low power, small size, and radiation hardness. The distributed nature of storage elements in nanocrystal floating-gate memories leads to intrinsic fault tolerance and radiation hardness. Conventional floating-gate non-volatile memories are more susceptible to radiation damage. Nanocrystal-based memories also offer the possibility of faster, lower power operation. In the pursuit of filling these requirements, the following tasks have been accomplished: (1) Si nanocrystal charging has been accomplished with conducting-tip AFM; (2) Both individual nanocrystals on an oxide surface and nanocrystals formed by implantation have been charged; (3) Discharging is consistent with tunneling through a field-lowered oxide barrier; (4) Modeling of the response of the AFM to trapped charge has allowed estimation of the quantity of trapped charge; and (5) Initial attempts to fabricate competitive nanocrystal non-volatile memories have been extremely successful.

On the improvement for charging large-scale flexible electrostatic actuators

NASA Astrophysics Data System (ADS)

Liao, Hsu-Ching; Chen, Han-Long; Su, Yu-Hao; Chen, Yu-Chi; Ko, Wen-Ching; Liou, Chang-Ho; Wu, Wen-Jong; Lee, Chih-Kung

2011-04-01

Recently, the development of flexible electret based electrostatic actuator has been widely discussed. The devices was shown to have high sound quality, energy saving, flexible structure and can be cut to any shape. However, achieving uniform charge on the electret diaphragm is one of the most critical processes needed to have the speaker ready for large-scale production. In this paper, corona discharge equipment contains multi-corona probes and grid bias was set up to inject spatial charges within the electret diaphragm. The optimal multi-corona probes system was adjusted to achieve uniform charge distribution of electret diaphragm. The processing conditions include the distance between the corona probes, the voltages of corona probe and grid bias, etc. We assembled the flexible electret loudspeakers first and then measured their sound pressure and beam pattern. The uniform charge distribution within the electret diaphragm based flexible electret loudspeaker provided us with the opportunity to shape the loudspeaker arbitrarily and to tailor the sound distribution per specifications request. Some of the potential futuristic applications for this device such as sound poster, smart clothes, and sound wallpaper, etc. were discussed as well.

In vitro extracellular recording and stimulation performance of nanoporous gold-modified multi-electrode arrays.

PubMed

Kim, Yong Hee; Kim, Gook Hwa; Kim, Ah Young; Han, Young Hwan; Chung, Myung-Ae; Jung, Sang-Don

2015-12-01

Nanoporous gold (Au) structures can reduce the impedance and enhance the charge injection capability of multi-electrode arrays (MEAs) used for interfacing neuronal networks. Even though there are various nanoporous Au preparation techniques, fabrication of MEA based on low-cost electro-codeposition of Ag:Au has not been performed. In this work, we have modified a Au MEA via the electro-codeposition of Ag:Au alloy, followed by the chemical etching of Ag, and report on the in vitro extracellular recording and stimulation performance of the nanoporous Au-modified MEA. Ag:Au alloy was electro-codeposited on a bilayer lift-off resist sputter-deposition passivated Au MEA followed by chemical etching of Ag to form a porous Au structure. The porous Au structure was analyzed by scanning electron microscopy and tunneling electron microscopy and found to have an interconnected nanoporous Au structure. The impedance value of the nanoporous Au-modified MEA is 15.4 ± 0.55 kΩ at 1 kHz, accompanied by the base noise V rms of 2.4 ± 0.3 μV. The charge injection limit of the nanoporous Au-modified electrode estimated from voltage transient measurement is approximately 1 mC cm(-2), which is comparable to roughened platinum and carbon nanotube electrodes. The charge injection capability of the nanoporous Au-modified MEA was confirmed by observing stimulus-induced spikes at above 0.2 V. The nanoporous Au-modified MEA showed mechanical durability upon ultrasonic treatment for up to an hour. Electro-codeposition of Ag:Au alloy combined with chemical etching Ag is a low-cost process for fabricating nanoporous Au-modified MEA suitable for establishing the stimulus-response relationship of cultured neuronal networks.

In vitro extracellular recording and stimulation performance of nanoporous gold-modified multi-electrode arrays

NASA Astrophysics Data System (ADS)

Kim, Yong Hee; Kim, Gook Hwa; Kim, Ah Young; Han, Young Hwan; Chung, Myung-Ae; Jung, Sang-Don

2015-12-01

Objective. Nanoporous gold (Au) structures can reduce the impedance and enhance the charge injection capability of multi-electrode arrays (MEAs) used for interfacing neuronal networks. Even though there are various nanoporous Au preparation techniques, fabrication of MEA based on low-cost electro-codeposition of Ag:Au has not been performed. In this work, we have modified a Au MEA via the electro-codeposition of Ag:Au alloy, followed by the chemical etching of Ag, and report on the in vitro extracellular recording and stimulation performance of the nanoporous Au-modified MEA. Approach. Ag:Au alloy was electro-codeposited on a bilayer lift-off resist sputter-deposition passivated Au MEA followed by chemical etching of Ag to form a porous Au structure. Main results. The porous Au structure was analyzed by scanning electron microscopy and tunneling electron microscopy and found to have an interconnected nanoporous Au structure. The impedance value of the nanoporous Au-modified MEA is 15.4 ± 0.55 kΩ at 1 kHz, accompanied by the base noise V rms of 2.4 ± 0.3 μV. The charge injection limit of the nanoporous Au-modified electrode estimated from voltage transient measurement is approximately 1 mC cm-2, which is comparable to roughened platinum and carbon nanotube electrodes. The charge injection capability of the nanoporous Au-modified MEA was confirmed by observing stimulus-induced spikes at above 0.2 V. The nanoporous Au-modified MEA showed mechanical durability upon ultrasonic treatment for up to an hour. Significance. Electro-codeposition of Ag:Au alloy combined with chemical etching Ag is a low-cost process for fabricating nanoporous Au-modified MEA suitable for establishing the stimulus-response relationship of cultured neuronal networks.

Ionic charge state measurements during He(+)-rich solar particle events

NASA Technical Reports Server (NTRS)

Hovestadt, D.; Klecker, B.; Scholer, M.; Gloeckler, G.

1984-01-01

Ionic charge state measurements of carbon, oxygen, and iron in He(+)-rich energetic particle events are presented. The data have been obtained with the Max-Planck-Institut/University of Maryland sensor system on the ISEE 3 spacecraft. The ionic charge states cannot be explained in terms of a model in which the coronal temperature determines a charge equilibrium which is subsequently frozen-in nor in terms of charge exchange during transition through coronal matter after acceleration. It is concluded that the acceleration and probably also the injection process is biased against particles with high mass-to-charge ratios. The plasma injected into the acceleration process must consist of material of cold (not greater than 8.5 x 10 to the 4th K) as well as hot (2.5 x 10 to the 6th K) origin. The cold material must be more abundant than the hot material.

On the nature of high field charge transport in reinforced silicone dielectrics: Experiment and simulation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Huang, Yanhui, E-mail: huangy12@rpi.edu; Schadler, Linda S.

The high field charge injection and transport properties in reinforced silicone dielectrics were investigated by measuring the time-dependent space charge distribution and the current under dc conditions up to the breakdown field and were compared with the properties of other dielectric polymers. It is argued that the energy and spatial distribution of localized electronic states are crucial in determining these properties for polymer dielectrics. Tunneling to localized states likely dominates the charge injection process. A transient transport regime arises due to the relaxation of charge carriers into deep traps at the energy band tails and is successfully verified by amore » Monte Carlo simulation using the multiple-hopping model. The charge carrier mobility is found to be highly heterogeneous due to the non-uniform trapping. The slow moving electron packet exhibits a negative field dependent drift velocity possibly due to the spatial disorder of traps.« less

Gate field plate IGBT with trench accumulation layer for extreme injection enhancement

NASA Astrophysics Data System (ADS)

Xu, Xiaorui; Chen, Wanjun; Liu, Chao; Chen, Nan; Tao, Hong; Shi, Yijun; Ma, Yinchang; Zhou, Qi; Zhang, Bo

2017-04-01

A gate field plate IGBT (GFP-IGBT) with extreme injection enhancement is proposed and verified using TCAD simulations. The GFP-IGBT features a gate field plate (GFP) inserted into n-drift region directly and a tiny P-base region separated from the GFP. In the ON-state, the accumulation layer is formed near to not only the bottom but also the side of the trench, which enhances electron injection efficiency. And the tiny P-base region reduces the holes extracted by reverse-biased P-base/N-drift junction. Both the GFP and tiny P-base contribute to achieving extreme injection enhancement, leading to a low forward voltage drop. In the OFF-state, due to the low stored charges in N-buffer layer, GFP-IGBT shows a short current fall time, leading to a decrease of turn-off loss. The simulation results show that, compared with the conventional IGBT, the GFP-IGBT offers a forward voltage drop reduction of 25% or current fall time reduction of 89% (i.e. turn-off loss reduction of 53%), resulting in low power loss. The excellent device performance, coupled with a commercial IGBT-compatible fabrication process, makes the proposed GFP-IGBT a promising candidate for power switching applications.

Photon-counting intensified random-access charge injection device

NASA Astrophysics Data System (ADS)

Norton, Timothy J.; Morrissey, Patrick F.; Haas, Patrick; Payne, Leslie J.; Carbone, Joseph; Kimble, Randy A.

1999-11-01

At NASA GSFC we are developing a high resolution solar-blind photon counting detector system for UV space based astronomy. The detector comprises a high gain MCP intensifier fiber- optically coupled to a charge injection device (CID). The detector system utilizes an FPGA based centroiding system to locate the center of photon events from the intensifier to high accuracy. The photon event addresses are passed via a PCI interface with a GPS derived time stamp inserted per frame to an integrating memory. Here we present imaging performance data which show resolution of MCP tube pore structure at an MCP pore diameter of 8 micrometer. This data validates the ICID concept for intensified photon counting readout. We also discuss correction techniques used in the removal of fixed pattern noise effects inherent in the centroiding algorithms used and present data which shows the local dynamic range of the device. Progress towards development of a true random access CID (RACID 810) is also discussed and astronomical data taken with the ICID detector system demonstrating the photon event time-tagging mode of the system is also presented.

Comparison of conductor and dielectric inks in printed organic complementary transistors

NASA Astrophysics Data System (ADS)

Ng, Tse Nga; Mei, Ping; Whiting, Gregory L.; Schwartz, David E.; Abraham, Biby; Wu, Yiliang; Veres, Janos

2014-10-01

Two types of printable conductor and a bilayer gate dielectric are evaluated for use in all-additive, inkjetprinted complementary OTFTs. The Ag nanoparticle ink based on nonpolar alkyl amine surfactant or stabilizer enables good charge injection into p-channel devices, but this ink also leaves residual stabilizer that modifies the transistor backchannel and shifts the turn-on voltage to negative values. The Ag ink based on polar solvent requires dopant modification to improve charge injection to p-channel devices, but this ink allows the OTFT turn-on voltage to be close to 0 V. The reverse trend is observed for n-channel OTFTs. For gate insulator, a bilayer dielectric is demonstrated that combines the advantages of two types of insulator materials, in which a fluoropolymer reduces dipolar disorder at the semiconductor-dielectric interface, while a high-k PVDF terpolymer dielectric facilitates high gate capacitance. The dielectric is incorporated into an inverter and a three-stage ring oscillator, and the resulting circuits were demonstrated to operate at a supply voltage as low as 2 V, with bias stress levels comparable to circuits with other types of dielectrics.

Advanced processing methods to introduce and preserve dipole orientation in organic electro-optic materials for next generation photonic devices

NASA Astrophysics Data System (ADS)

Huang, Su

Organic electro-optic (E-O) materials have attracted considerable research attention in the past 20 years due to their rising potentials in a lot of novel photonic applications, such as high-speed telecommunication, terahertz generation and ultra-fast optical interconnections. Chapter 2 of this dissertation focuses on a barrier layer approach to improve the poling efficiency of electro-optic polymers. First of all, high conduction current from excessive charge injection is identified as a fundamental challenge of effective poling. After analyzing the conduction mechanism, we introduce a sol-gel derived thin titanium dioxide (TiO2) layer that can significantly block excessive charge injection and reduce the leakage current during high field poling. Ultralarge E-O coefficients, up to 160-350 pm/V at 1310 nm have been achieved by poling with such a barrier, which are 26%-40% higher than the results poled without such a TiO2 layer. This enhancement is explained by the suppressed charge injection and space charge accumulation by the insertion of the high injection barrier from the TiO2 barrier layer. In Chapter 3, the impact of the inserted barrier layer on the temporal alignment stability of E-O polymers is discussed. Considerable stability enhancement is confirmed using both standard 500-hour temporal alignment stability test at 85 °C and thermally stimulated discharge method. We suggest that the enhancement comes from improved stability of the screening charge. During poling the additional barrier layer helps to lower the injection and thus the space charge accumulation. And this reduced space charge accumulation further helps to replace the space charge part in the total formulation of screening charge with more stable interface trapped charge. We thus expand this knowledge to a group of other materials that can also block excessive charge injection and suppressed space charge accumulation, including dielectric polymers polyvinyl alcohol (PVA), poly(4-vinylphenol) (PVP) and TOPAS as well as ferroelectric polymer poly(vinylidene fluoride-co-trifluoroethylene) (P(VDF-TrFE), 65/35 copolymer), which differ largely from the others in dielectric constant, conductivity and surface properties. The only common feature of them is that they all lowered the charge injection and leakage current for 1-2 orders during poling. On every buffer layer we tried, similar trend of stability enhancement is found. These results suggest that the observed temporal stability enhancement is indeed an effect from the abovementioned mechanism. Chapter 4 focuses on the development of an innovative new poling method, which utilizes pyroelectric effect instead of external power sources to overcome the limitations of conventional contact poling and corona poling. With careful theory assisted design, we developed a reliable protocol to efficiently introduce dipole orientation in organic E-O materials by heating and cooling them with detachable pyroelectric crystals. This new method can potentially improve the process adaptability of organic E-O materials in a variety of photonic devices. Large Pockels coefficients (up to 81 pm/V at 1.3 micron) have been successfully achieved in thin films poled using this method. The effective fields in these experiments are estimated to be around 0.5 to 0.9 MV/cm, which agree well with the electrostatics analysis using an idealized model. The same method is directly applied to surface modified hybrid polymer silicon slot waveguide ring-resonator modulators devices. A 25 pm/V tunability of resonance peak wavelength shift has been realized, which was higher than any reported results in similar devices. Chapter 5 discusses about the possible application of the pyroelectric poling in a multi-stack waveguide device architecture. A long-existing challenge to pole E-O polymer based photonic devices is how to effectively drop the poling voltage to the core layer, which is usually sandwiched between two dielectric claddings. In the past, this was done by using relatively conductive claddings, which on the other hand can bring larger optical loss and dielectric loss to the waveguide. Thus careful engineering compromise must be made between better poling efficiency and lower loss. Pyroelectric poling as discussed in Chapter 4 opens up new possibilities. In this chapter, it is demonstrated that E-O polymer films can be poled even with 3 orders thicker dielectric layer in circuit using pyroelectric poling. The theoretical analysis matches well with the experimental results. (Abstract shortened by UMI.).

Injectable hydrogels with high fixed charge density and swelling pressure for nucleus pulposus repair: biomimetic glycosaminoglycan analogues.

PubMed

Sivan, S S; Roberts, S; Urban, J P G; Menage, J; Bramhill, J; Campbell, D; Franklin, V J; Lydon, F; Merkher, Y; Maroudas, A; Tighe, B J

2014-03-01

The load-bearing biomechanical role of the intervertebral disc is governed by the composition and organization of its major macromolecular components, collagen and aggrecan. The major function of aggrecan is to maintain tissue hydration, and hence disc height, under the high loads imposed by muscle activity and body weight. Key to this role is the high negative fixed charge of its glycosaminoglycan side chains, which impart a high osmotic pressure to the tissue, thus regulating and maintaining tissue hydration and hence disc height under load. In degenerate discs, aggrecan degrades and is lost from the disc, particularly centrally from the nucleus pulposus. This loss of fixed charge results in reduced hydration and loss of disc height; such changes are closely associated with low back pain. The present authors developed biomimetic glycosaminoglycan analogues based on sulphonate-containing polymers. These biomimetics are deliverable via injection into the disc where they polymerize in situ, forming a non-degradable, nuclear "implant" aimed at restoring disc height to degenerate discs, thereby relieving back pain. In vitro, these glycosaminoglycan analogues possess appropriate fixed charge density, hydration and osmotic responsiveness, thereby displaying the capacity to restore disc height and function. Preliminary biomechanical tests using a degenerate explant model showed that the implant adapts to the space into which it is injected and restores stiffness. These hydrogels mimic the role taken by glycosaminoglycans in vivo and, unlike other hydrogels, provide an intrinsic swelling pressure, which can maintain disc hydration and height under the high and variable compressive loads encountered in vivo. Copyright © 2013 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Analytical and numerical studies of photo-injected charge transport in molecularly-doped polymers

NASA Astrophysics Data System (ADS)

Roy Chowdhury, Amrita

The mobility of photo-injected charge carriers in molecularly-doped polymers (MDPs) exhibits a commonly observed, and nearly universal Poole-Frenkel field dependence, mu exp√(beta0E), that has been shown to arise from the correlated Gaussian energy distribution of transport sites encountered by charges undergoing hopping transport through the material. Analytical and numerical studies of photo-injected charge transport in these materials are presented here with an attempt to understand how specific features of the various models developed to describe these systems depend on the microscopic parameters that define them. Specifically, previously published time-of-flight mobility data for the molecularly doped polymer 30% DEH:PC (polycarbonate doped with 30 wt.% aromatic hydrazone DEH) is compared with direct analytical and numerical predictions of five disorder-based models, the Gaussian disorder model (GDM) of Bassler, and four correlated disorder models introduced by Novikov, et al., and by Parris, et al. In these numerical studies, disorder parameters describing each model were varied from reasonable starting conditions, in order to give the best overall fit. The uncorrelated GDM describes the Poole-Frenkel field dependence of the mobility only at very high fields, but fails for fields lower than about 64 V/mum. The correlated disorder models with small amounts of geometrical disorder do a good over-all job of reproducing a robust Poole-Frenkel field dependence, with correlated disorder theories that employ polaron transition rates showing qualitatively better agreement with experiment than those that employ Miller-Abrahams rates. In a separate study, the heuristic treatment of spatial or geometric disorder incorporated in existing theories is critiqued, and a randomly-diluted lattice gas model is developed to describe the spatial disorder of the transport sites in a more realistic way.

A model and simulation of fast space charge pulses in polymers

NASA Astrophysics Data System (ADS)

Lv, Zepeng; Rowland, Simon M.; Wu, Kai

2017-11-01

The transport of space charge packets across polyethylene and epoxy resin in high electric fields has been characterized as fast or slow depending on packet mobility. Several explanations for the formation and transport of slow space charge packets have been proposed, but the origins of fast space charge pulses, with mobilities above 10-11 m2 V-1 s-1, are unclear. In one suggested model, it is assumed that the formation of fast charge pulses is due to discontinuous electromechanical compression and charge injection at the electrode-insulation interface, and their transport is related to corresponding relaxation processes. In that model, charges travel as a pulse because of group polarization. This paper provides an alternative model based on the reduction of charge carrier activation energy due to charge density triggered polymer chain movement and subsequent chain relaxation times. The generation and transport of fast charge pulses are readily simulated by a bipolar charge transport model with three additional parameters: reduced activation energy, charge density threshold, and chain relaxation time. Such a model is shown to reproduce key features of fast space charge pulses including speed, duration, repetition rate and pulse size. This model provides the basis for a deep understanding of the physical origins of fast space charge pulses in polymers.

Reducing Soot in Diesel Exhaust

NASA Technical Reports Server (NTRS)

Bellan, J.

1984-01-01

Electrically charged fuel improves oxidation. Fuel injection system reduces amount of soot formed in diesel engines. Spray injector electrically charges fuel droplets as they enter cylinder. Charged droplets repel each other, creating, dilute fuel mist easily penetrated by oxygen in cylinder.

Charge injection and accumulation in organic light-emitting diode with PEDOT:PSS anode

DOE Office of Scientific and Technical Information (OSTI.GOV)

Weis, Martin, E-mail: martin.weis@stuba.sk; Otsuka, Takako; Taguchi, Dai

2015-04-21

Organic light-emitting diode (OLED) displays using flexible substrates have many attractive features. Since transparent conductive oxides do not fit the requirements of flexible devices, conductive polymer poly(3,4-ethylenedioxythiophene):poly(4-styrenesulfonate) (PEDOT:PSS) has been proposed as an alternative. The charge injection and accumulation in OLED devices with PEDOT:PSS anodes are investigated and compared with indium tin oxide anode devices. Higher current density and electroluminescence light intensity are achieved for the OLED device with a PEDOT:PSS anode. The electric field induced second-harmonic generation technique is used for direct observation of temporal evolution of electric fields. It is clearly demonstrated that the improvement in the devicemore » performance of the OLED device with a PEDOT:PSS anode is associated with the smooth charge injection and accumulation.« less

Universal diffusion-limited injection and the hook effect in organic thin-film transistors

NASA Astrophysics Data System (ADS)

Liu, Chuan; Huseynova, Gunel; Xu, Yong; Long, Dang Xuan; Park, Won-Tae; Liu, Xuying; Minari, Takeo; Noh, Yong-Young

2016-07-01

The general form of interfacial contact resistance was derived for organic thin-film transistors (OTFTs) covering various injection mechanisms. Devices with a broad range of materials for contacts, semiconductors, and dielectrics were investigated and the charge injections in staggered OTFTs was found to universally follow the proposed form in the diffusion-limited case, which is signified by the mobility-dependent injection at the metal-semiconductor interfaces. Hence, real ohmic contact can hardly ever be achieved in OTFTs with low carrier concentrations and mobility, and the injection mechanisms include thermionic emission, diffusion, and surface recombination. The non-ohmic injection in OTFTs is manifested by the generally observed hook shape of the output conductance as a function of the drain field. The combined theoretical and experimental results show that interfacial contact resistance generally decreases with carrier mobility, and the injection current is probably determined by the surface recombination rate, which can be promoted by bulk-doping, contact modifications with charge injection layers and dopant layers, and dielectric engineering with high-k dielectric materials.

Universal diffusion-limited injection and the hook effect in organic thin-film transistors.

PubMed

Liu, Chuan; Huseynova, Gunel; Xu, Yong; Long, Dang Xuan; Park, Won-Tae; Liu, Xuying; Minari, Takeo; Noh, Yong-Young

2016-07-21

The general form of interfacial contact resistance was derived for organic thin-film transistors (OTFTs) covering various injection mechanisms. Devices with a broad range of materials for contacts, semiconductors, and dielectrics were investigated and the charge injections in staggered OTFTs was found to universally follow the proposed form in the diffusion-limited case, which is signified by the mobility-dependent injection at the metal-semiconductor interfaces. Hence, real ohmic contact can hardly ever be achieved in OTFTs with low carrier concentrations and mobility, and the injection mechanisms include thermionic emission, diffusion, and surface recombination. The non-ohmic injection in OTFTs is manifested by the generally observed hook shape of the output conductance as a function of the drain field. The combined theoretical and experimental results show that interfacial contact resistance generally decreases with carrier mobility, and the injection current is probably determined by the surface recombination rate, which can be promoted by bulk-doping, contact modifications with charge injection layers and dopant layers, and dielectric engineering with high-k dielectric materials.

Universal diffusion-limited injection and the hook effect in organic thin-film transistors

PubMed Central

Liu, Chuan; Huseynova, Gunel; Xu, Yong; Long, Dang Xuan; Park, Won-Tae; Liu, Xuying; Minari, Takeo; Noh, Yong-Young

2016-01-01

The general form of interfacial contact resistance was derived for organic thin-film transistors (OTFTs) covering various injection mechanisms. Devices with a broad range of materials for contacts, semiconductors, and dielectrics were investigated and the charge injections in staggered OTFTs was found to universally follow the proposed form in the diffusion-limited case, which is signified by the mobility-dependent injection at the metal-semiconductor interfaces. Hence, real ohmic contact can hardly ever be achieved in OTFTs with low carrier concentrations and mobility, and the injection mechanisms include thermionic emission, diffusion, and surface recombination. The non-ohmic injection in OTFTs is manifested by the generally observed hook shape of the output conductance as a function of the drain field. The combined theoretical and experimental results show that interfacial contact resistance generally decreases with carrier mobility, and the injection current is probably determined by the surface recombination rate, which can be promoted by bulk-doping, contact modifications with charge injection layers and dopant layers, and dielectric engineering with high-k dielectric materials. PMID:27440253

Tunneling modulation of a quantum-well transistor laser

NASA Astrophysics Data System (ADS)

Feng, M.; Qiu, J.; Wang, C. Y.; Holonyak, N.

2016-11-01

Different than the Bardeen and Brattain transistor (1947) with the current gain depending on the ratio of the base carrier spontaneous recombination lifetime to the emitter-collector transit time, the Feng and Holonyak transistor laser current gain depends upon the base electron-hole (e-h) stimulated recombination, the base dielectric relaxation transport, and the collector stimulated tunneling. For the n-p-n transistor laser tunneling operation, the electron-hole pairs are generated at the collector junction under the influence of intra-cavity photon-assisted tunneling, with electrons drifting to the collector and holes drifting to the base. The excess charge in the base lowers the emitter junction energy barrier, allowing emitter electron injection into the base and satisfying charge neutrality via base dielectric relaxation transport (˜femtoseconds). The excess electrons near the collector junction undergo stimulated recombination at the base quantum-well or transport to the collector, thus supporting tunneling current amplification and optical modulation of the transistor laser.

PIC code modeling of spacecraft charging potential during electron beam injection into a background of neutral gas and plasma, part 1

NASA Technical Reports Server (NTRS)

Koga, J. K.; Lin, C. S.; Winglee, R. M.

1989-01-01

Injections of nonrelativistic electron beams from an isolated equipotential conductor into a uniform background of plasma and neutral gas were simulated using a 2-D electrostatic particle code. The ionization effects on spacecraft charging are examined by including interactions of electrons with neutral gas. The simulations show that the conductor charging potential decreases with increasing neutral background density due to the production of secondary electrons near the conductor surface. In the spacecraft wake, the background electrons accelerated towards the charged spacecraft produce an enhancement of secondary electrons and ions. Simulations run for longer times indicate that the spacecraft potential is further reduced and short wavelength beam-plasma oscillations appear. The results are applied to explain the spacecraft charging potential measured during the SEPAC experiments from Spacelab 1.

Synergetic Influences of Mixed-Host Emitting Layer Structures and Hole Injection Layers on Efficiency and Lifetime of Simplified Phosphorescent Organic Light-Emitting Diodes.

PubMed

Han, Tae-Hee; Kim, Young-Hoon; Kim, Myung Hwan; Song, Wonjun; Lee, Tae-Woo

2016-03-09

We used various nondestructive analyses to investigate various host material systems in the emitting layer (EML) of simple-structured, green phosphorescent organic light-emitting diodes (OLEDs) to clarify how the host systems affect its luminous efficiency (LE) and operational stability. An OLED that has a unipolar single-host EML with conventional poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) ( PSS) showed high operating voltage, low LE (∼26.6 cd/A, 13.7 lm/W), and short lifetime (∼4.4 h @ 1000 cd/m(2)). However, the combined use of a gradient mixed-host EML and a molecularly controlled HIL that has increased surface work function (WF) remarkably decreased operating voltage and improved LE (∼68.7 cd/A, 77.0 lm/W) and lifetime (∼70.7 h @ 1000 cd/m(2)). Accumulated charges at the injecting interfaces and formation of a narrow recombination zone close to the interfaces are the major factors that accelerate degradation of charge injection/transport and electroluminescent properties of OLEDs, so achievement of simple-structured OLEDs with high efficiency and long lifetime requires facilitating charge injection and balanced transport into the EML and distributing charge carriers and excitons in EML.

The cost-effectiveness of CT-guided sacroiliac joint injections: a measure of QALY gained.

PubMed

Bydon, Mohamad; Macki, Mohamed; De la Garza-Ramos, Rafael; Youssef, Mina; Gokaslan, Ziya L; Meleka, Sherif; Bydon, Ali

2014-10-01

The purpose of this study is to estimate the total cost and the quality of life years (QALY) gained for computer tomography (CT)-guided sacroiliac joint (SIJ) injections. The cost per QALY gained for the procedure is the primary end-point of this study. In our 1-year prospective institutional study, we gathered 30 patients undergoing CT-guided SIJ injections for degenerative changes at the SIJ space. Patient-reported outcomes included both the US population-based EQ-5D (EuroQol) index score and the EQ-visual analog scale (VAS). The EQ-5D is based on mobility, self-care, usual activities, pain/discomfort, and anxiety depression. Utility expenditures were based on hospital charges at our institution. All 30 patients had one pre-injection physician visit followed by 43 initial injections (13 bilateral). Each patient underwent one CT scan, and three patients required additional plain films. In the 1 year following the injections, 26 physician visits were documented. Five patients required repeat CT-guided injections. Total 1-year cost for all 30 patients was $34 874·00. Mean decrease in EQ-VAS was 0·60 (P  =  0·187). The mean 1-year gain of 0·58 EQ-5D QALY reached statistical significance (P < 0·001). The cost per QALY gained by CT-guided sacroiliac injections was $2004·29. In one of the first cost analyses of CT-guided sacroiliac injections, we found that the procedure improves pain and activities of daily living. The cost per QALY gained by CT-guided sacroiliac injections falls well below the threshold cost of 1 QALY, suggesting that the procedure is strongly cost-effective.

Reconfigurable Diodes Based on Vertical WSe2 Transistors with van der Waals Bonded Contacts.

PubMed

Avsar, Ahmet; Marinov, Kolyo; Marin, Enrique Gonzalez; Iannaccone, Giuseppe; Watanabe, Kenji; Taniguchi, Takashi; Fiori, Gianluca; Kis, Andras

2018-05-01

New device concepts can increase the functionality of scaled electronic devices, with reconfigurable diodes allowing the design of more compact logic gates being one of the examples. In recent years, there has been significant interest in creating reconfigurable diodes based on ultrathin transition metal dichalcogenide crystals due to their unique combination of gate-tunable charge carriers, high mobility, and sizeable band gap. Thanks to their large surface areas, these devices are constructed under planar geometry and the device characteristics are controlled by electrostatic gating through rather complex two independent local gates or ionic-liquid gating. In this work, similar reconfigurable diode action is demonstrated in a WSe 2 transistor by only utilizing van der Waals bonded graphene and Co/h-BN contacts. Toward this, first the charge injection efficiencies into WSe 2 by graphene and Co/h-BN contacts are characterized. While Co/h-BN contact results in nearly Schottky-barrier-free charge injection, graphene/WSe 2 interface has an average barrier height of ≈80 meV. By taking the advantage of the electrostatic transparency of graphene and the different work-function values of graphene and Co/h-BN, vertical devices are constructed where different gate-tunable diode actions are demonstrated. This architecture reveals the opportunities for exploring new device concepts. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

New functionalities of potassium tantalate niobate deflectors enabled by the coexistence of pre-injected space charge and composition gradient

NASA Astrophysics Data System (ADS)

Zhu, Wenbin; Chao, Ju-Hung; Chen, Chang-Jiang; Campbell, Adrian L.; Henry, Michael G.; Yin, Stuart Shizhuo; Hoffman, Robert C.

2017-10-01

In most beam steering applications such as 3D printing and in vivo imaging, one of the essential challenges has been high-resolution high-speed multi-dimensional optical beam scanning. Although the pre-injected space charge controlled potassium tantalate niobate (KTN) deflectors can achieve speeds in the nanosecond regime, they deflect in only one dimension. In order to develop a high-resolution high-speed multi-dimensional KTN deflector, we studied the deflection behavior of KTN deflectors in the case of coexisting pre-injected space charge and composition gradient. We find that such coexistence can enable new functionalities of KTN crystal based electro-optic deflectors. When the direction of the composition gradient is parallel to the direction of the external electric field, the zero-deflection position can be shifted, which can reduce the internal electric field induced beam distortion, and thus enhance the resolution. When the direction of the composition gradient is perpendicular to the direction of the external electric field, two-dimensional beam scanning can be achieved by harnessing only one single piece of KTN crystal, which can result in a compact, high-speed two-dimensional deflector. Both theoretical analyses and experiments are conducted, which are consistent with each other. These new functionalities can expedite the usage of KTN deflection in many applications such as high-speed 3D printing, high-speed, high-resolution imaging, and free space broadband optical communication.

Lateral and Vertical Organic Transistors

NASA Astrophysics Data System (ADS)

Al-Shadeedi, Akram

An extensive study has been performed to provide a better understanding of the operation principles of doped organic field-effect transistors (OFETs), organic p-i-n diodes, Schottky diodes, and organic permeable base transistors (OPBTs). This has been accomplished by a combination of electrical and structural characterization of these devices. The discussion of doped OFETs focuses on the shift of the threshold voltage due to increased doping concentrations and the generation and transport of minority charge carriers. Doping of pentacene OFETs is achieved by co-evaporation of pentacene with the n-dopant W2(hpp)4. It is found that pentacene thin film are efficiently doped and that a conductivity in the range of 2.6 x 10-6 S cm-1 for 1 wt% to 2.5 x 10-4 S cm-1 for 16 wt% is reached. It is shown that n-doped OFET consisting of an n-doped channel and n-doped contacts are ambipolar. This behavior is surprising, as n-doping the contacts should suppress direct injection of minority charge carriers (holes). It was proposed that minority charge carrier injection and hence the ambipolar characteristic of n-doped OFETs can be explained by Zener tunneling inside the intrinsic pentacene layer underneath the drain electrode. It is shown that the electric field in this layer is indeed in the range of the breakdown field of pentacene based p-i-n Zener homodiodes. Doping the channel has a profound influence on the onset voltage of minority (hole) conduction. The onset voltage can be shifted by lightly n-doping the channel. The shift of onset voltage can be explained by two mechanisms: first, due to a larger voltage that has to be applied to the gate in order to fully deplete the n-doped layer. Second, it can be attributed to an increase in hole trapping by inactive dopants. Moreover, it has been shown that the threshold voltage of majority (electron) conduction is shifted by an increase in the doping concentration, and that the ambipolar OFETs can be turned into unipolar OFETs at high doping concentrations. In subsequent chapters, the working mechanisms of OPBTs are discussed. OPBTs consist of two Schottky diodes (top and bottom diode), and the charge transport in these C60-based Schottky diodes is studied first. Two transport regimes can be distinguished in forward direction - injection limited currents (ILCs) and space charge limited currents (SCLCs). It is found that the current increases exponentially with applied voltage in the ILC regime and depends quadratically on the applied voltage in the SCLC regime. Furthermore, it is observed that the forward and backward currents of the Schottky diode are increased by decreasing the C60 layer thickness, increasing the active area, and increasing the temperature. Furthermore, in order to reach a high performance, various treatments have been applied. Air exposure, a variation of the thickness of the top electrode, as well as annealing of the diodes are used to optimize the diodes. OPBTs are processed by using the semiconductor C60 due its high charge carrier mobility and good film-forming properties. Again, the working mechanism of OPBTs is studied by electrical characterization (base-sweep measurements and output characteristics). To achieve a high performance of OPBTs, various treatments and techniques have been applied. The annealing of the OPBTs after fabrication changes the morphology of the base electrode. Thus, openings (pinholes) are formed in the base electrode, which enables a high current transfer from the upper to lower semiconductor layer. The formation of openings is proved by analyzing SEM and TEM image of the base electrode. Adding a doped layer at the emitter is another process to optimize the OPBTs. The doped layer ensures a high charge carrier injection at the emitter, leading to a high transmission and current gain. Furthermore, it has been observed that the ON/OFF ratio and transconductance of OPBTs increases by decreasing their active area. A very high transconductance gm of 37 S/cm2 is reached, which has the potential to boost the switching speed of organic transistors to 5 MHz. Furthermore, it is shown that the base electrode thickness is an essential parameter for OPBTs. The current gain beta decreases by increasing thickness of base electrode, whereas the ON/OFF ratio increases for thicker base electrodes.

Motions of charged particles in the magnetosphere under the influence of a time-varying large scale convection electric field

NASA Technical Reports Server (NTRS)

Smith, P. H.; Hoffman, R. A.; Bewtra, N. K.

1979-01-01

The motions of charged particles under the influence of the geomagnetic and electric fields are quite complex in the region of the inner magnetosphere. The Volland-Stern type large-scale convection electric field with gamma = 2 has been used successfully to predict both the plasmapause location and particle enhancements determined from Explorer 45 (S3-A) measurements. Recently introduced into the trajectory calculations of Ejiri et al. (1978) is a time dependence in this electric field based on the variation in Kp for actual magnetic storm conditions. The particle trajectories are computed as they change in this time-varying electric field. Several storm fronts of particles of different magnetic moments are allowed to be injected into the inner magnetosphere from L = 10 in the equatorial plane. The motions of these fronts are presented in a movie format. The local time of injection, the particle magnetic moments and the subsequent temporal history of the magnetospheric electric field play important roles in determining whether the injected particles are trapped within the ring current region or whether they are convected to regions outside the inner magnetosphere.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dempsey, Adam B.; Curran, Scott; Wagner, Robert M.

Gasoline compression ignition concepts with the majority of the fuel being introduced early in the cycle are known as partially premixed combustion (PPC). Previous research on single- and multi-cylinder engines has shown that PPC has the potential for high thermal efficiency with low NOx and soot emissions. A variety of fuel injection strategies has been proposed in the literature. These injection strategies aim to create a partially stratified charge to simultaneously reduce NOx and soot emissions while maintaining some level of control over the combustion process through the fuel delivery system. The impact of the direct injection strategy to createmore » a premixed charge of fuel and air has not previously been explored, and its impact on engine efficiency and emissions is not well understood. This paper explores the effect of sweeping the direct injected pilot timing from -91° to -324° ATDC, which is just after the exhaust valve closes for the engine used in this study. During the sweep, the pilot injection consistently contained 65% of the total fuel (based on command duration ratio), and the main injection timing was adjusted slightly to maintain combustion phasing near top dead center. A modern four cylinder, 1.9 L diesel engine with a variable geometry turbocharger, high pressure common rail injection system, wide included angle injectors, and variable swirl actuation was used in this study. The pistons were modified to an open bowl configuration suitable for highly premixed combustion modes. The stock diesel injection system was unmodified, and the gasoline fuel was doped with a lubricity additive to protect the high pressure fuel pump and the injectors. The study was conducted at a fixed speed/load condition of 2000 rpm and 4.0 bar brake mean effective pressure (BMEP). The pilot injection timing sweep was conducted at different intake manifold pressures, swirl levels, and fuel injection GTP-15-1067, Dempsey 2 pressures. The gasoline used in this study has relatively high fuel reactivity with a research octane number of 68. The results of this experimental campaign indicate that the highest brake thermal efficiency and lowest emissions are achieved simultaneously with the earliest pilot injection timings (i.e., during the intake stroke).« less

Self-consistent modeling of laminar electrohydrodynamic plumes from ultra-sharp needles in cyclohexane

NASA Astrophysics Data System (ADS)

Becerra, Marley; Frid, Henrik; Vázquez, Pedro A.

2017-12-01

This paper presents a self-consistent model of electrohydrodynamic (EHD) laminar plumes produced by electron injection from ultra-sharp needle tips in cyclohexane. Since the density of electrons injected into the liquid is well described by the Fowler-Nordheim field emission theory, the injection law is not assumed. Furthermore, the generation of electrons in cyclohexane and their conversion into negative ions is included in the analysis. Detailed steady-state characteristics of EHD plumes under weak injection and space-charge limited injection are studied. It is found that the plume characteristics far from both electrodes and under weak injection can be accurately described with an asymptotic simplified solution proposed by Vazquez et al. ["Dynamics of electrohydrodynamic laminar plumes: Scaling analysis and integral model," Phys. Fluids 12, 2809 (2000)] when the correct longitudinal electric field distribution and liquid velocity radial profile are used as input. However, this asymptotic solution deviates from the self-consistently calculated plume parameters under space-charge limited injection since it neglects the radial variations of the electric field produced by a high-density charged core. In addition, no significant differences in the model estimates of the plume are found when the simulations are obtained either with the finite element method or with a diffusion-free particle method. It is shown that the model also enables the calculation of the current-voltage characteristic of EHD laminar plumes produced by electron field emission, with good agreement with measured values reported in the literature.

Reaction-space analysis of homogeneous charge compression ignition combustion with varying levels of fuel stratification under positive and negative valve overlap conditions

DOE PAGES

Kodavasal, Janardhan; Lavoie, George A.; Assanis, Dennis N.; ...

2015-10-26

Full-cycle computational fluid dynamics simulations with gasoline chemical kinetics were performed to determine the impact of breathing and fuel injection strategies on thermal and compositional stratification, combustion and emissions during homogeneous charge compression ignition combustion. The simulations examined positive valve overlap and negative valve overlap strategies, along with fueling by port fuel injection and direct injection. The resulting charge mass distributions were analyzed prior to ignition using ignition delay as a reactivity metric. The reactivity stratification arising from differences in the distributions of fuel–oxygen equivalence ratio (Φ FO), oxygen molar fraction (χ O2) and temperature (T) was determined for threemore » parametric studies. In the first study, the reactivity stratification and burn duration for positive valve overlap valve events with port fuel injection and early direct injection were nearly identical and were dominated by wall-driven thermal stratification. nitrogen oxide (NO) and carbon monoxide (CO) emissions were negligible for both injection strategies. In the second study, which examined negative valve overlap valve events with direct injection and port fuel injection, reactivity stratification increased for direct injection as the Φ FO and T distributions associated with direct fuel injection into the hot residual gas were positively correlated; however, the latent heat absorbed from the hot residual gas by the evaporating direct injection fuel jet reduced the overall thermal and reactivity stratification. These stratification effects were offsetting, resulting in similar reactivity stratification and burn durations for the two injection strategies. The higher local burned gas temperatures with direct injection resulted in an order of magnitude increase in NO, while incomplete combustion of locally over-lean regions led to a sevenfold increase in CO emissions compared to port fuel injection. The final study evaluated positive valve overlap and negative valve overlap valve events with direct injection. Furthermore, relative to positive valve overlap, the negative valve overlap condition had a wider reactivity stratification, a longer burn duration and higher NO and CO emissions associated with reduced fuel–air mixing.« less

Plasma membrane translocation of a protein needle based on a triple-stranded β-helix motif.

PubMed

Sanghamitra, Nusrat J M; Inaba, Hiroshi; Arisaka, Fumio; Ohtan Wang, Dan; Kanamaru, Shuji; Kitagawa, Susumu; Ueno, Takafumi

2014-10-01

Plasma membrane translocation is challenging due to the barrier of the cell membrane. Contrary to the synthetic cell-penetrating materials, tailed bacteriophages use cell-puncturing protein needles to puncture the cell membranes as an initial step of the DNA injection process. Cell-puncturing protein needles are thought to remain functional in the native phages. In this paper, we found that a bacteriophage T4 derived protein needle of 16 nm length spontaneously translocates through the living cell membrane. The β-helical protein needle (β-PN) internalizes into human red blood cells that lack endocytic machinery. By comparing the cellular uptake of β-PNs with modified surface charge, it is shown that the uptake efficiency is maximum when it has a negative charge corresponding to a zeta potential value of -16 mV. In HeLa cells, uptake of β-PN incorporates endocytosis independent mechanisms with partial macropinocytosis dependence. The endocytosis dependence of the uptake increases when the surface charges of β-PNs are modified to positive or negative. Thus, these results suggest that natural DNA injecting machinery can serve as an inspiration to design new class of cell-penetrating materials with a tailored mechanism.

Controlled Electron Injection into Plasma Accelerators and SpaceCharge Estimates

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fubiani, Gwenael G.J.

2005-09-01

Plasma based accelerators are capable of producing electron sources which are ultra-compact (a few microns) and high energies (up to hundreds of MeVs) in much shorter distances than conventional accelerators. This is due to the large longitudinal electric field that can be excited without the limitation of breakdown as in RF structures.The characteristic scale length of the accelerating field is the plasma wavelength and for typical densities ranging from 10 18 - 10 19 cm -3, the accelerating fields and scale length can hence be on the order of 10-100GV/m and 10-40 μm, respectively. The production of quasimonoenergetic beams wasmore » recently obtained in a regime relying on self-trapping of background plasma electrons, using a single laser pulse for wakefield generation. In this dissertation, we study the controlled injection via the beating of two lasers (the pump laser pulse creating the plasma wave and a second beam being propagated in opposite direction) which induce a localized injection of background plasma electrons. The aim of this dissertation is to describe in detail the physics of optical injection using two lasers, the characteristics of the electron beams produced (the micrometer scale plasma wavelength can result in femtosecond and even attosecond bunches) as well as a concise estimate of the effects of space charge on the dynamics of an ultra-dense electron bunch with a large energy spread.« less

Towards a Switched-Capacitor Based Stimulator for Efficient Deep-Brain Stimulation

PubMed Central

Vidal, Jose; Ghovanloo, Maysam

2013-01-01

We have developed a novel 4-channel prototype stimulation circuit for implantable neurological stimulators (INS). This Switched-Capacitor based Stimulator (SCS) aims to utilize charge storage and charge injection techniques to take advantage of both the efficiency of conventional voltage-controlled stimulators (VCS) and the safety and controllability of current-controlled stimulators (CCS). The discrete SCS prototype offers fine control over stimulation parameters such as voltage, current, pulse width, frequency, and active electrode channel via a LabVIEW graphical user interface (GUI) when connected to a PC through USB. Furthermore, the prototype utilizes a floating current sensor to provide charge-balanced biphasic stimulation and ensure safety. The stimulator was analyzed using an electrode-electrolyte interface (EEI) model as well as with a pair of pacing electrodes in saline. The primary motivation of this research is to test the feasibility and functionality of a safe, effective, and power-efficient switched-capacitor based stimulator for use in Deep Brain Stimulation. PMID:21095987

Hybrid Hydroxyapatite Nanoparticle Colloidal Gels are Injectable Fillers for Bone Tissue Engineering

PubMed Central

Gu, Zhen; Jamal, Syed; Detamore, Michael S.

2013-01-01

Injectable bone fillers have emerged as an alternative to the invasive surgery often required to treat bone defects. Current bone fillers may benefit from improvements in dynamic properties such as shear thinning during injection and recovery of material stiffness after placement. Negatively charged inorganic hydroxyapatite (HAp) nanoparticles (NPs) were assembled with positively charged organic poly(d,l-lactic-co-glycolic acid) (PLGA) NPs to create a cohesive colloidal gel. This material is held together by electrostatic forces that may be disrupted by shear to facilitate extrusion, molding, or injection. Scanning electron micrographs of the dried colloidal gels showed a well-organized, three-dimensional porous structure. Rheology tests revealed that certain colloidal gels could recover after being sheared. Human umbilical cord mesenchymal stem cells were also highly viable when seeded on the colloidal gels. HAp/PLGA NP colloidal gels offer an attractive scheme for injectable filling and regeneration of bone tissue. PMID:23815275

Substrate driven photochemistry of CdSe quantum dot films: charge injection and irreversible transformations on oxide surfaces.

PubMed

Tvrdy, Kevin; Kamat, Prashant V

2009-04-23

The photochemical behavior of CdSe quantum dots anchored to different surfaces was probed through their deposition on glass, SiO2, and TiO2 films. Following visible light irradiation under ambient conditions, CdSe quantum dots deposited on semiconducting TiO2 surface degraded, where no such degradation was observed when deposited on inert SiO2 surface or glass. Fluorescence decay and transient absorption experiments confirmed that charge injection from excited CdSe into TiO2 occurs with an apparent rate constant of 5.62 x 10(8) s(-1) and is the primary event responsible for photodegradation. In the presence of air, injected electrons are scavenged by surface adsorbed oxygen leaving behind reactive holes which induce anodic corrosion of CdSe quantum dots. In a vacuum environment, minimal CdSe degradation was observed as electron scavenging by oxygen is replaced with charge recombination between injected electrons and holes in CdSe nanocrystals. Spectroscopic measurements presented in this study highlight the role of both substrate and medium in dictating the photochemistry of CdSe quantum dots.

Theoretical determination of the ionization potential and the electron affinity of organic semiconductors

NASA Astrophysics Data System (ADS)

Yanagisawa, Susumu

2017-11-01

Ionization potential and electron affinity of organic semicondutors are important quantities, which are relevant to charge injection barriers. The electrostatic and dynamical contributions to the polarization energies for the injected charges in pentacene polymorphs were investigated. While the dynamical polarization induced narrowing of the energy gap, the electrostatic effect shifted up or down the frontier energy levels, which is sensitive to the molecular orientation at the surface.

Radiation from a space charge dominated linear electron beam

DOE Office of Scientific and Technical Information (OSTI.GOV)

Biswas, Debabrata

2008-01-15

It is commonly known that radiation loss in linear beam transport is largely unimportant. For a space charge dominated linear beam, however, radiation power loss can be an appreciable fraction of the injected beam power [Biswas, Kumar, and Puri, Phys. Plasmas 14, 094702 (2007)]. Exploring this further, the electromagnetic nature of radiation due to the passage of a space charge dominated electron beam in a 'closed' drift tube is explicitly demonstrated by identifying the cavity modes where none existed prior to beam injection. It is further shown that even in an 'open' drift tube from which radiation may leak, themore » modes that escape contribute to the time variation of the electric and magnetic fields in the transient phase. As the window opening increases, the oscillatory transient phase disappears altogether. However, the 'bouncing ball' modes survive and can be observed between the injection and collection plates.« less

Titanyl phthalocyanine ambipolar thin film transistors making use of carbon nanotube electrodes

NASA Astrophysics Data System (ADS)

Coppedè, Nicola; Valitova, Irina; Mahvash, Farzaneh; Tarabella, Giuseppe; Ranzieri, Paolo; Iannotta, Salvatore; Santato, Clara; Martel, Richard; Cicoira, Fabio

2014-12-01

The capability of efficiently injecting charge carriers into organic films and finely tuning their morphology and structure is crucial to improve the performance of organic thin film transistors (OTFTs). In this work, we investigate OTFTs employing carbon nanotubes (CNTs) as the source-drain electrodes and, as the organic semiconductor, thin films of titanyl phthalocyanine (TiOPc) grown by supersonic molecular beam deposition (SuMBD). While CNT electrodes have shown an unprecedented ability to improve charge injection in OTFTs, SuMBD is an effective technique to tune film morphology and structure. Varying the substrate temperature during deposition, we were able to grow both amorphous (low substrate temperature) and polycrystalline (high substrate temperature) films of TiOPc. Regardless of the film morphology and structure, CNT electrodes led to superior charge injection and transport performance with respect to benchmark Au electrodes. Vacuum annealing of polycrystalline TiOPc films with CNT electrodes yielded ambipolar OTFTs.

Caractérisation de l'augmentation des transferts thermiques dans une couche de liquide diélectrique soumise à une injection unipolaire de charges électriques

NASA Astrophysics Data System (ADS)

Traoré, Philippe; Koulova-Nenova, D.; Romat, H.; Perez, A.

2009-03-01

The electro-thermo-convective flow in a horizontal dielectric liquid layer placed between two electrodes and subjected to an injection of electric charges from one of the electrodes and at the same time to a thermal gradient is studied numerically. We consider the case of a strong charge injection in order to only take into account the Coulomb force disregarding the dielectric forces, from above and below the layer. The effect of the action of both electric and thermal fields on the dielectric liquid layer is analyzed and the behavior of the flow when these fields compete or cooperate is studied. It is demonstrated that the electrically induced convection enhances the heat transfer. To cite this article: Ph. Traoré et al., C. R. Mecanique 337 (2009).

Controllable conversion of quasi-freestanding polymer chains to graphene nanoribbons

NASA Astrophysics Data System (ADS)

Ma, Chuanxu; Xiao, Zhongcan; Zhang, Honghai; Liang, Liangbo; Huang, Jingsong; Lu, Wenchang; Sumpter, Bobby G.; Hong, Kunlun; Bernholc, J.; Li, An-Ping

2017-03-01

In the bottom-up synthesis of graphene nanoribbons (GNRs) from self-assembled linear polymer intermediates, surface-assisted cyclodehydrogenations usually take place on catalytic metal surfaces. Here we demonstrate the formation of GNRs from quasi-freestanding polymers assisted by hole injections from a scanning tunnelling microscope (STM) tip. While catalytic cyclodehydrogenations typically occur in a domino-like conversion process during the thermal annealing, the hole-injection-assisted reactions happen at selective molecular sites controlled by the STM tip. The charge injections lower the cyclodehydrogenation barrier in the catalyst-free formation of graphitic lattices, and the orbital symmetry conservation rules favour hole rather than electron injections for the GNR formation. The created polymer-GNR intraribbon heterostructures have a type-I energy level alignment and strongly localized interfacial states. This finding points to a new route towards controllable synthesis of freestanding graphitic layers, facilitating the design of on-surface reactions for GNR-based structures.

Relativistic Acceleration of Electrons Injected by a Plasma Mirror into a Radially Polarized Laser Beam.

PubMed

Zaïm, N; Thévenet, M; Lifschitz, A; Faure, J

2017-09-01

We propose a method to generate femtosecond, relativistic, and high-charge electron bunches using few-cycle and tightly focused radially polarized laser pulses. In this scheme, the incident laser pulse reflects off an overdense plasma that injects electrons into the reflected pulse. Particle-in-cell simulations show that the plasma injects electrons ideally, resulting in a dramatic increase of charge and energy of the accelerated electron bunch in comparison to previous methods. This method can be used to generate femtosecond pC bunches with energies in the 1-10 MeV range using realistic laser parameters corresponding to current kHz laser systems.

Photoresponse of polyaniline-functionalized graphene quantum dots

NASA Astrophysics Data System (ADS)

Lai, Sin Ki; Luk, Chi Man; Tang, Libin; Teng, Kar Seng; Lau, Shu Ping

2015-03-01

Polyaniline-functionalized graphene quantum dots (PANI-GQD) and pristine graphene quantum dots (GQDs) were utilized for optoelectronic devices. The PANI-GQD based photodetector exhibited higher responsivity which is about an order of magnitude at 405 nm and 7 folds at 532 nm as compared to GQD-based photodetectors. The improved photoresponse is attributed to the enhanced interconnection of GQD by island-like polymer matrices, which facilitate carrier transport within the polymer matrices. The optically tunable current-voltage (I-V) hysteresis of PANI-GQD was also demonstrated. The hysteresis magnifies progressively with light intensity at a scan range of +/-1 V. Both GQD and PANI-GQD devices change from positive to negative photocurrent when the bias reaches 4 V. Photogenerated carriers are excited to the trapping states in GQDs with increased bias. The trapped charges interact with charges injected from the electrodes which results in a net decrease of free charge carriers and a negative photocurrent. The photocurrent switching phenomenon in GQD and PANI-GQD devices may open up novel applications in optoelectronics.Polyaniline-functionalized graphene quantum dots (PANI-GQD) and pristine graphene quantum dots (GQDs) were utilized for optoelectronic devices. The PANI-GQD based photodetector exhibited higher responsivity which is about an order of magnitude at 405 nm and 7 folds at 532 nm as compared to GQD-based photodetectors. The improved photoresponse is attributed to the enhanced interconnection of GQD by island-like polymer matrices, which facilitate carrier transport within the polymer matrices. The optically tunable current-voltage (I-V) hysteresis of PANI-GQD was also demonstrated. The hysteresis magnifies progressively with light intensity at a scan range of +/-1 V. Both GQD and PANI-GQD devices change from positive to negative photocurrent when the bias reaches 4 V. Photogenerated carriers are excited to the trapping states in GQDs with increased bias. The trapped charges interact with charges injected from the electrodes which results in a net decrease of free charge carriers and a negative photocurrent. The photocurrent switching phenomenon in GQD and PANI-GQD devices may open up novel applications in optoelectronics. Electronic supplementary information (ESI) available: Raman spectrum of PANI-GQD, TGA, Red-shift of PL peak with the amounts of aniline, excitation dependent PL of PANI-GQD, area of hysteretic loop for different voltage scan ranges, photocurrent at 1 V under prolonged illumination. See DOI: 10.1039/c4nr07565j

SIMULATIONS OF BOOSTER INJECTION EFFICIENCY FOR THE APS-UPGRADE

DOE Office of Scientific and Technical Information (OSTI.GOV)

Calvey, J.; Borland, M.; Harkay, K.

2017-06-25

The APS-Upgrade will require the injector chain to provide high single bunch charge for swap-out injection. One possible limiting factor to achieving this is an observed reduction of injection efficiency into the booster synchrotron at high charge. We have simulated booster injection using the particle tracking code elegant, including a model for the booster impedance and beam loading in the RF cavities. The simulations point to two possible causes for reduced efficiency: energy oscillations leading to losses at high dispersion locations, and a vertical beam size blowup caused by ions in the Particle Accumulator Ring. We also show that themore » efficiency is much higher in an alternate booster lattice with smaller vertical beta function and zero dispersion in the straight sections.« less

Fluorescence spectral shift of QD films with electron injection: Dependence on counterion proximity

NASA Astrophysics Data System (ADS)

Lu, Meilin; Li, Bo; Zhang, Yaxin; Liu, Weilong; Yang, Yanqiang; Wang, Yuxiao; Yang, Qingxin

2017-05-01

Due to the promising application of quantum dot (QD) films in solar cells, LEDs and environmental detectors, the fluorescence of charged QD films has achieved much attention during recent years. In this work, we observe the spectral shift of photoluminescence (PL) in charged CdSe/ZnS QD films controlled by electrochemical potential. The spectral center under negative bias changes from red-shift to blue-shift while introducing smaller inorganic counterions (potassium ions) into the electrolyte. This repeatable effect is attributed to the enhanced electron injection with smaller cations and the electronic perturbations of QD luminescence by these excess charges.

Internal combustion engine using premixed combustion of stratified charges

DOEpatents

Marriott, Craig D [Rochester Hills, MI; Reitz, Rolf D [Madison, WI

2003-12-30

During a combustion cycle, a first stoichiometrically lean fuel charge is injected well prior to top dead center, preferably during the intake stroke. This first fuel charge is substantially mixed with the combustion chamber air during subsequent motion of the piston towards top dead center. A subsequent fuel charge is then injected prior to top dead center to create a stratified, locally richer mixture (but still leaner than stoichiometric) within the combustion chamber. The locally rich region within the combustion chamber has sufficient fuel density to autoignite, and its self-ignition serves to activate ignition for the lean mixture existing within the remainder of the combustion chamber. Because the mixture within the combustion chamber is overall premixed and relatively lean, NO.sub.x and soot production are significantly diminished.

Impact of Illumination on Charge Injection and Accumulation in Organic Transistor in Presence of Plasmonic Nanoparticles

NASA Astrophysics Data System (ADS)

Lee, Keanchuan; Weis, Martin; Chen, Xiangyu; Taguchi, Dai; Manaka, Takaaki; Iwamoto, Mitsumasa

2013-04-01

Effects of illumination on the carrier injection and transport due to photogenerated carriers were investigated in pentacene organic field-effect transistor (OFET). A plasmonic nanoparticles self-assembled monolayer (SAM) was incorporated in pentacene FET to act to enhance the photo-carrier generation. The influence of nanoparticles (NPs) on the photogeneration as well as on the charge trapping has been investigated using the current-voltage (I-V) and impedance spectroscopy (IS) measurements. The I-V results proved higher amount of photogenerated charge in presence of NPs even though this device has the contact resistance about two orders higher and effective mobility an order lower than the reference device without plasmonic NPs. The IS analysis of relaxation times verified strong influence of NPs on the charge trapping.

Electrical degradation of triarylamine-based light-emitting polymer diodes monitored by micro-Raman spectroscopy

NASA Astrophysics Data System (ADS)

Kim, Ji-Seon; Ho, Peter K. H.; Murphy, Craig E.; Seeley, Alex J. A. B.; Grizzi, Ilaria; Burroughes, Jeremy H.; Friend, Richard H.

2004-03-01

Although much progress has been made in improving polymer light-emitting diode performance, there has been little work to address device intrinsic degradation mechanisms due to the challenge of tracking minute chemical reactions in the 100-nm-thick buried active layers during operation. Here we have elucidated a hole-mediated electrical degradation of triarylamine-based blue polymer diodes using in situ Raman microspectroscopy. A slow irreversible hole-doping of polymer adjacent to the hole-injecting conducting-polymer leads to formation of oxidised triarylamine species counterbalanced by anions from the conducting-polymer. These charged species act as luminescence quenchers and hinder further hole injection across the interface leading to significant decreases in current density at low voltages.

Point-to-plane and plane-to-plane electrostatic charge injection atomization for insulating liquids

NASA Astrophysics Data System (ADS)

Malkawi, Ghazi

An electrostatic charge injection atomizer was fabricated and used to introduce and study the electrostatic charge injection atomization methods for highly viscous vegetable oils and high conductivity low viscosity aviation fuel, JP8. The total, spray and leakage currents and spray breakup characteristics for these liquids were investigated and compared with Diesel fuel data. Jet breakup and spray atomization mechanism showed differences for vegetable oils and lower viscosity hydrocarbon fuels. For vegetable oils, a bending/spinning instability phenomenon was observed similar to the phenomenon found in liquid jets of high viscosity polymer solutions. The spray tip lengths and cone angles were presented qualitatively and quantitatively and correlated with the appropriate empirical formulas. The different stages of the breakup mechanisms for such oils, as a function of specific charges and flow rates, were discussed. In order to make this method of atomization more suitable for practical use in high flow rate applications, a blunt face electrode (plane-to-plane) was used as the charge emitter in place of a single pointed electrode (point-to-plane). This allowed the use of a multi-orifice emitter that maintained a specific charge with the flow rate increase which could not be achieved with the needle electrode. The effect of the nozzle geometry, liquid physical properties and applied bulk flow on the spray charge, total charge, maximum critical spray specific charge and electrical efficiency compared with the needle point-to-plane atomizer results was presented. Our investigation revealed that the electrical efficiency of the atomizer is dominated by the charge forced convection rate rather than charge transport by ion motilities and liquid motion by the electric field. As a result of the electric coulomb forces between the electrified jets, the multi-orifice atomizer provided a unique means of dispersing the fuel in a hollow cone with wide angles making the new method suitable for variety of combustion applications.

Electromagnetic analysis of the plasma chamber of an ECR-based charge breeder

DOE Office of Scientific and Technical Information (OSTI.GOV)

Galatà, A., E-mail: alessio.galata@lnl.infn.it; Patti, G.; Celona, L.

2016-02-15

The optimization of the efficiency of an ECR-based charge breeder is a twofold task: efforts must be paid to maximize the capture of the injected 1+ ions by the confined plasma and to produce high charge states to allow post-acceleration at high energies. Both tasks must be faced by studying in detail the electrons heating dynamics, influenced by the microwave-to-plasma coupling mechanism. Numerical simulations are a powerful tools for obtaining quantitative information about the wave-to-plasma interaction process: this paper presents a numerical study of the microwaves propagation and absorption inside the plasma chamber of the PHOENIX charge breeder, which themore » selective production of exotic species project, under construction at Legnaro National Laboratories, will adopt as charge breeder. Calculations were carried out with a commercial 3D FEM solver: first, all the resonant frequencies were determined by considering a simplified plasma chamber; then, the realistic geometry was taken into account, including a cold plasma model of increasing complexity. The results gave important information about the power absorption and losses and will allow the improvement of the plasma model to be used in a refined step of calculation reproducing the breeding process itself.« less

Enhanced Internal Quantum Efficiency in Dye-Sensitized Solar Cells: Effect of Long-Lived Charge-Separated State of Sensitizers.

PubMed

Sun, Haiya; Liu, Dongzhi; Wang, Tianyang; Lu, Ting; Li, Wei; Ren, Siyao; Hu, Wenping; Wang, Lichang; Zhou, Xueqin

2017-03-22

Effective charge separation is one of the key determinants for the photovoltaic performance of the dye-sensitized solar cells (DSSCs). Herein, two charge-separated (CS) sensitizers, MTPA-Pyc and YD-Pyc, have been synthesized and applied in DSSCs to investigate the effect of the CS states of the sensitizers on the device's efficiency. The CS states with lifetimes of 64 and 177 ns for MTPA-Pyc and YD-Pyc, respectively, are formed via the photoinduced electron transfer (PET) from the 4-styryltriphenylamine (MTPA) or 4-styrylindoline (YD) donor to the pyrimidine cyanoacrylic acid (Pyc) acceptor. DSSCs based on MTPA-Pyc and YD-Pyc exhibit high internal quantum efficiency (IQE) values of over 80% from 400 to 600 nm. In comparison, the IQEs of the charge transfer (CT) sensitizer cells are 10-30% lower in the same wavelength range. The enhanced IQE values in the devices based on the CS sensitizers are ascribed to the higher electron injection efficiencies and slower charge recombination. The results demonstrate that taking advantage of the CS states in the sensitizers can be a promising strategy to improve the IQEs and further enhance the overall efficiencies of the DSSCs.

Electromagnetic analysis of the plasma chamber of an ECR-based charge breeder

NASA Astrophysics Data System (ADS)

Galatà, A.; Patti, G.; Celona, L.; Mascali, D.; Neri, L.; Torrisi, G.

2016-02-01

The optimization of the efficiency of an ECR-based charge breeder is a twofold task: efforts must be paid to maximize the capture of the injected 1+ ions by the confined plasma and to produce high charge states to allow post-acceleration at high energies. Both tasks must be faced by studying in detail the electrons heating dynamics, influenced by the microwave-to-plasma coupling mechanism. Numerical simulations are a powerful tools for obtaining quantitative information about the wave-to-plasma interaction process: this paper presents a numerical study of the microwaves propagation and absorption inside the plasma chamber of the PHOENIX charge breeder, which the selective production of exotic species project, under construction at Legnaro National Laboratories, will adopt as charge breeder. Calculations were carried out with a commercial 3D FEM solver: first, all the resonant frequencies were determined by considering a simplified plasma chamber; then, the realistic geometry was taken into account, including a cold plasma model of increasing complexity. The results gave important information about the power absorption and losses and will allow the improvement of the plasma model to be used in a refined step of calculation reproducing the breeding process itself.

Charge carrier thermalization in organic diodes

PubMed Central

van der Kaap, N. J.; Koster, L. J. A.

2016-01-01

Charge carrier mobilities of organic semiconductors are often characterized using steady-state measurements of space charge limited diodes. These measurements assume that charge carriers are in a steady-state equilibrium. In reality, however, energetically hot carriers are introduces by photo-excitation and injection into highly energetic sites from the electrodes. These carriers perturb the equilibrium density of occupied states, and therefore change the overall charge transport properties. In this paper, we look into the effect of energetically hot carriers on the charge transport in organic semiconductors using steady state kinetic Monte Carlo simulations. For injected hot carriers in a typical organic semiconductor, rapid energetic relaxation occurs in the order of tens of nanoseconds, which is much faster than the typical transit time of a charge carrier throught the device. Furthermore, we investigate the impact of photo-generated carriers on the steady-state mobility. For a typical organic voltaic material, an increase in mobility of a factor of 1.1 is found. Therefore, we conclude that the impact of energetically hot carriers on normal device operation is limited. PMID:26791095

Trap-assisted hole injection and quantum efficiency enhancement in poly(9,9' dioctylfluorene-alt-benzothiadiazole) polymer light-emitting diodes

NASA Astrophysics Data System (ADS)

Seeley, Alexander J. A. B.; Friend, Richard H.; Kim, Ji-Seon; Burroughes, Jeremy H.

2004-12-01

We report a reversible many-fold quantum efficiency enhancement during electrical driving of polymer light-emitting diodes (LEDs) containing poly(9,9' dioctylfluorene-alt-benzothiadiazole) (F8BT), developing over several minutes or hours at low applied bias and recovering on similar time scales after driving. This phenomenon is observed only in devices containing F8BT as an emissive layer in pure or blended form, regardless of anode and cathode choices and even in the absence of a poly(styrene-sulphonate)-doped poly(3,4-ethylene-dioxythiophene) (PEDOT:PSS) layer. We report detailed investigations using a standardized device structure containing PEDOT:PSS and a calcium cathode. Direct measurements of trapped charge recovered from the device after driving significantly exceed the unipolar limit, and thermally activated relaxation suggests a maximum trap depth around 0.6eV. Neither photoluminescence nor electroluminescence spectra reveal any change in the bulk optoelectronic properties of the emissive polymer nor any new emissive species. During the quantum efficiency (QE) enhancement process, the bulk conduction of the device increases. Reverse bias treatment of the device significantly reinforces the QE enhancement. Based on these observations, we propose a simple model in which interfacial dipoles are generated by trapped holes near the anode combining with injected electrons, to produce a narrow tunneling barrier for easy hole injection. The new injection pathway leads to a higher hole current density and thus a better charge injection balance. This produces the relatively high quantum efficiency observed in all F8BT LEDs.

Particle identification using digital pulse shape discrimination in a nTD silicon detector with a 1 GHz sampling digitizer

NASA Astrophysics Data System (ADS)

Mahata, K.; Shrivastava, A.; Gore, J. A.; Pandit, S. K.; Parkar, V. V.; Ramachandran, K.; Kumar, A.; Gupta, S.; Patale, P.

2018-06-01

In beam test experiments have been carried out for particle identification using digital pulse shape analysis in a 500 μm thick Neutron Transmutation Doped (nTD) silicon detector with an indigenously developed FPGA based 12 bit resolution, 1 GHz sampling digitizer. The nTD Si detector was used in a low-field injection setup to detect light heavy-ions produced in reactions of ∼ 5 MeV/A 7Li and 12C beams on different targets. Pulse height, rise time and current maximum have been obtained from the digitized charge output of a high bandwidth charge and current sensitive pre-amplifier. Good isotopic separation have been achieved using only the digitized charge output in case of light heavy-ions. The setup can be used for charged particle spectroscopy in nuclear reactions involving light heavy-ions around the Coulomb barrier energies.

The direct injection of intense ion beams from a high field electron cyclotron resonance ion source into a radio frequency quadrupole

NASA Astrophysics Data System (ADS)

Rodrigues, G.; Becker, R.; Hamm, R. W.; Baskaran, R.; Kanjilal, D.; Roy, A.

2014-02-01

The ion current achievable from high intensity ECR sources for highly charged ions is limited by the high space charge. This makes classical extraction systems for the transport and subsequent matching to a radio frequency quadrupole (RFQ) accelerator less efficient. The direct plasma injection (DPI) method developed originally for the laser ion source avoids these problems and uses the combined focusing of the gap between the ion source and the RFQ vanes (or rods) and the focusing of the rf fields from the RFQ penetrating into this gap. For high performance ECR sources that use superconducting solenoids, the stray magnetic field of the source in addition to the DPI scheme provides focusing against the space charge blow-up of the beam. A combined extraction/matching system has been designed for a high performance ECR ion source injecting into an RFQ, allowing a total beam current of 10 mA from the ion source for the production of highly charged 238U40+ (1.33 mA) to be injected at an ion source voltage of 60 kV. In this design, the features of IGUN have been used to take into account the rf-focusing of an RFQ channel (without modulation), the electrostatic field between ion source extraction and the RFQ vanes, the magnetic stray field of the ECR superconducting solenoid, and the defocusing space charge of an ion beam. The stray magnetic field is shown to be critical in the case of a matched beam.

The direct injection of intense ion beams from a high field electron cyclotron resonance ion source into a radio frequency quadrupole.

PubMed

Rodrigues, G; Becker, R; Hamm, R W; Baskaran, R; Kanjilal, D; Roy, A

2014-02-01

The ion current achievable from high intensity ECR sources for highly charged ions is limited by the high space charge. This makes classical extraction systems for the transport and subsequent matching to a radio frequency quadrupole (RFQ) accelerator less efficient. The direct plasma injection (DPI) method developed originally for the laser ion source avoids these problems and uses the combined focusing of the gap between the ion source and the RFQ vanes (or rods) and the focusing of the rf fields from the RFQ penetrating into this gap. For high performance ECR sources that use superconducting solenoids, the stray magnetic field of the source in addition to the DPI scheme provides focusing against the space charge blow-up of the beam. A combined extraction/matching system has been designed for a high performance ECR ion source injecting into an RFQ, allowing a total beam current of 10 mA from the ion source for the production of highly charged (238)U(40+) (1.33 mA) to be injected at an ion source voltage of 60 kV. In this design, the features of IGUN have been used to take into account the rf-focusing of an RFQ channel (without modulation), the electrostatic field between ion source extraction and the RFQ vanes, the magnetic stray field of the ECR superconducting solenoid, and the defocusing space charge of an ion beam. The stray magnetic field is shown to be critical in the case of a matched beam.

The effect of the hole injection layer on the performance of single layer organic light-emitting diodes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wenjin, Zeng; Ran, Bi; Hongmei, Zhang, E-mail: iamhmzhang@njupt.edu.cn, E-mail: iamwhuang@njupt.edu.cn

2014-12-14

Efficient single-layer organic light-emitting diodes (OLEDs) were reported based on a green fluorescent dye 10-(2-benzothiazolyl)-2,3,6,7-tetrahydro-1,1,7,7–tetramethyl-1H,5H,11H-(1) benzopyropyrano (6,7-8-I,j)quinolizin-11-one (C545T). Herein, poly(3,4-ethylenedioxy thiophene) poly(styrene sulfonate) were, respectively, applied as the injection layer for comparison. The hole transport properties of the emission layer with different hole injection materials are well investigated via current-voltage measurement. It was clearly found that the hole injection layers (HILs) play an important role in the adjustment of the electron/hole injection to attain transport balance of charge carriers in the single emission layer of OLEDs with electron-transporting host. The layer of tris-(8-hydroxyquinoline) aluminum played a dual role of hostmore » and electron-transporting materials within the emission layer. Therefore, appropriate selection of hole injection layer is a key factor to achieve high efficiency OLEDs with single emission layer.« less

Influence of polymeric electron injection layers on the electrical properties of solution-processed multilayered polymer light-emitting diodes

NASA Astrophysics Data System (ADS)

Itoh, Eiji; Kurami, Kazuhiko

2016-02-01

In this study, we fabricated multilayered polymer-based light-emitting diodes (pLEDs) with various solution-processed electron-injection layers (EILs), and investigated the influence of the EILs on the electrical properties of pLEDs in indium tin oxide (ITO)/poly(3,4-ethylenedioxythiophene) doped with poly(styrene sulfonic acid) (PEDOT:PSS)/poly[(9,9-dioctylfluorene-alt-(1,4-phenylene((4-sec-butylphenyl)amino)-1,4-phenylene))] (TFB) (HTL)/poly(9,9-dioctylfluorene-alt-1,4-benzothiadiazole) (F8BT) (EML)/EIL/Al structures. We have used the quaternized ammonium π-conjugated polyelectrolyte derivative (poly[(9,9-di(3,3‧-N,N‧-trimethylammonium)propylfluorenyl-2,7-diyl)-co-(1,4-phenylene)]diiodide salt) (PF-PDTA), a mixture of PF-PDTA and CS2CO3, and the aliphatic-amine-based polymer poly(ethylene imine) (PEI) as solution-processed EILs, and compared them with LiF as a solvent-free EIL. The EILs enhanced the electron injection and improve the pLED performance. High external quantum efficiencies of nearly 4% were obtained in the pLEDs with the combination of a multilayered structure fabricated by a transfer printing technique and EILs of a PF-PDTA:CS2CO3 mixture and PEI. On the other hand, the device with PF-PDTA exhibited lower efficiency, higher driving voltage, and larger leakage current at lower voltage. The migration of ionic charges was suggested from the abnormal dielectric behaviors, and serious damage on the electrode material occurred when both an acid hole-injection layer (PEDOT:PSS) and PF-PDTA were used. On the other hand, the pLEDs with ultrathin PEI showed high performance and stable device operation in terms of the influence of ionic charges.

GAP/CL-20-Based Compound Explosive: A New Booster Formulation Used in a Small-Sized Initiation Network

NASA Astrophysics Data System (ADS)

Yanju, Wei; Jingyu, Wang; Chongwei, An; Hequn, Li; Xiaomu, Wen; Binshuo, Yu

2017-01-01

With ε-2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane (CL-20) and glycidyl azide polymer (GAP) as the solid filler and binder, respectively, GAP/CL-20-based compound explosives were designed and prepared. Using micro injection charge technology, the compound explosives were packed into small grooves to explore their application in a small-sized initiation network. The detonation reliability, detonation velocity, mechanical sensitivity, shock sensitivity, and brisance of the explosive were measured and analyzed. The results show that when the solid content of CL-20 is 82 wt%, the explosive charged in the groove has a smooth surface from a macroscopic view. From a microscopic view, a coarse surface is bonded with many CL-20 particles by GAP binder. The GAP/CL-20-based explosive charge successfully generates detonation waves in a groove larger than 0.6 mm × 0.6 mm. When the charge density in the groove is 1.68 g.cm-3 (90% theoretical maximum density), the detonation velocity reaches 7,290 m.s-1. Moreover, this kind of explosive is characterized by low impact and shock sensitivity.

Investigation of the optical and electrical characteristics of solution-processed poly (3 hexylthiophene) (P3HT): multiwall carbon nanotube (MWCNT) composite-based devices

NASA Astrophysics Data System (ADS)

Rathore, Priyanka; Mohan Singh Negi, Chandra; Singh Verma, Ajay; Singh, Amarjeet; Chauhan, Gayatri; Regis Inigo, Anto; Gupta, Saral K.

2017-08-01

Devices comprised of solution-processed poly (3-hexylthiophene) (P3HT)/multiwall carbon nanotubes (MWCNTs), with various concentrations of MWCNTs, were fabricated and characterized. The morphology of the P3HT: MWCNT nanocomposite was characterized by using field emission scanning electron microscopy (FESEM). The optical characteristics of the nanocomposite were studied by UV/VIS/NIR spectroscopy and Raman spectroscopy. The electrical properties of the fabricated devices were characterized by measuring the current density-voltage (J-V) characteristics. While the J-V characteristics of a pristine P3HT device reveal thermal injection limited charge transport, the P3HT: MWCNT nanocomposite-based devices exhibit three distinct voltage-dependent conduction regimes. The fitting curve with measured data reveals Ohmic conduction for a low voltage range, a trap-charge limited conduction (TCLC) process at an intermediate voltage range followed by a trap free space-charge limited conduction (SCLC) process at much higher voltages. A fundamental understanding of this work can assist in creating new charge transport pathways which will provide new avenues for the development of highly efficient polymer-based optoelectronic devices.

Charge balancing in GaN-based 2-D electron gas devices employing an additional 2-D hole gas and its influence on dynamic behaviour of GaN-based heterostructure field effect transistors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hahn, Herwig, E-mail: hahn@gan.rwth-aachen.de; Reuters, Benjamin; Geipel, Sascha

2015-03-14

GaN-based heterostructure FETs (HFETs) featuring a 2-D electron gas (2DEG) can offer very attractive device performance for power-switching applications. This performance can be assessed by evaluation of the dynamic on-resistance R{sub on,dyn} vs. the breakdown voltage V{sub bd}. In literature, it has been shown that with a high V{sub bd}, R{sub on,dyn} is deteriorated. The impairment of R{sub on,dyn} is mainly driven by electron injection into surface, barrier, and buffer traps. Electron injection itself depends on the electric field which typically peaks at the gate edge towards the drain. A concept suitable to circumvent this issue is the charge-balancing conceptmore » which employs a 2-D hole gas (2DHG) on top of the 2DEG allowing for the electric field peak to be suppressed. Furthermore, the 2DEG concentration in the active channel cannot decrease by a change of the surface potential. Hence, beside an improvement in breakdown voltage, also an improvement in dynamic behaviour can be expected. Whereas the first aspect has already been demonstrated, the second one has not been under investigation so far. Hence, in this report, the effect of charge-balancing is discussed and its impact on the dynamic characteristics of HFETs is evaluated. It will be shown that with appropriate device design, the dynamic behaviour of HFETs can be improved by inserting an additional 2DHG.« less

Direct determination of energy level alignment and charge transport at metal-Alq3 interfaces via ballistic-electron-emission spectroscopy.

PubMed

Jiang, J S; Pearson, J E; Bader, S D

2011-04-15

Using ballistic-electron-emission spectroscopy (BEES), we directly determined the energy barrier for electron injection at clean interfaces of Alq(3) with Al and Fe to be 2.1 and 2.2 eV, respectively. We quantitatively modeled the sub-barrier BEES spectra with an accumulated space charge layer, and found that the transport of nonballistic electrons is consistent with random hopping over the injection barrier.

Direct determination of energy level alignment and charge transport at metal/Alq{sub 3} interfaces via ballistic-electron-emission spectroscopy.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jiang, J. S.; Pearson, J. E.; Bader, S. D.

2011-04-15

Using ballistic-electron-emission spectroscopy (BEES), we directly determined the energy barrier for electron injection at clean interfaces of Alq{sub 3} with Al and Fe to be 2.1 and 2.2 eV, respectively. We quantitatively modeled the sub-barrier BEES spectra with an accumulated space charge layer, and found that the transport of nonballistic electrons is consistent with random hopping over the injection barrier.

N-type molecular electrical doping in organic semiconductors: formation and dissociation efficiencies of charge transfer complex

NASA Astrophysics Data System (ADS)

Kim, Jae-Min; Yoo, Seung-Jun; Moon, Chang-Ki; Sim, Bomi; Lee, Jae-Hyun; Lim, Heeseon; Kim, Jeong Won; Kim, Jang-Joo

2016-09-01

Electrical doping is an important method in organic electronics to enhance device efficiency by controlling Fermi level, increasing conductivity, and reducing injection barrier from electrode. To understand the charge generation process of dopant in doped organic semiconductors, it is important to analyze the charge transfer complex (CTC) formation and dissociation into free charge carrier. In this paper, we correlate charge generation efficiency with the CTC formation and dissociation efficiency of n-dopant in organic semiconductors (OSs). The CTC formation efficiency of Rb2CO3 linearly decreases from 82.8% to 47.0% as the doping concentration increases from 2.5 mol% to 20 mol%. The CTC formation efficiency and its linear decrease with doping concentration are analytically correlated with the concentration-dependent size and number of dopant agglomerates by introducing the degree of reduced CTC formation. Lastly, the behavior of dissociation efficiency is discussed based on the picture of the statistical semiconductor theory and the frontier orbital hybridization model.

Injector Design for a Model Electron Ring at the University of Maryland

NASA Astrophysics Data System (ADS)

Godlove, T.; Bernal, S.; Deng, J. J.; Li, Y.; Reiser, M.; Wang, J. G.; Zou, Y.

1997-05-01

A model electron recirculator is being developed at the University of Maryland. It employs a 10-keV, space-charge-dominated beam injected into a 1.8-m radius ring equipped with a strong-focusing lattice based on printed-circuit quadrupoles and dipoles. The motivation and general features are described in separate papers. Here we describe the design for injecting a single-turn bunch into the ring. The system includes a low-emittance e-gun, matching section, pulsed dipole and Panofsky quadrupole. The dipole at the injection point must deflect the beam -10^circ during entry and +10^circ after entry, with about 25 ns transition time. The Panofsky quadrupole must be off during entry and on for subsequent laps, with a similar rise time.

Dynamics of direct X-ray detection processes in high-Z Bi2O3 nanoparticles-loaded PFO polymer-based diodes

NASA Astrophysics Data System (ADS)

Ciavatti, A.; Cramer, T.; Carroli, M.; Basiricò, L.; Fuhrer, R.; De Leeuw, D. M.; Fraboni, B.

2017-10-01

Semiconducting polymer based X-ray detectors doped with high-Z nanoparticles hold the promise to combine mechanical flexibility and large-area processing with a high X-ray stopping power and sensitivity. Currently, a lack of understanding of how nanoparticle doping impacts the detector dynamics impedes the optimization of such detectors. Here, we study direct X-ray radiation detectors based on the semiconducting polymer poly(9,9-dioctyfluorene) blended with Bismuth(III)oxide (Bi2O3) nanoparticles (NPs). Pure polymer diodes show a high mobility of 1.3 × 10-5 cm2/V s, a low leakage current of 200 nA/cm2 at -80 V, and a high rectifying factor up to 3 × 105 that allow us to compare the X-ray response of a polymer detector in charge-injection conditions (forward bias) and in charge-collection conditions (reverse bias), together with the impact of NP-loading in the two operation regimes. When operated in reverse bias, the detectors reach the state of the art sensitivity of 24 μC/Gy cm2, providing a fast photoresponse. In forward operation, a slower detection dynamics but improved sensitivity (up to 450 ± 150 nC/Gy) due to conductive gain is observed. High-Z NP doping increases the X-ray absorption, but higher NP loadings lead to a strong reduction of charge-carrier injection and transport due to a strong impact on the semiconductor morphology. Finally, the time response of optimized detectors showed a cut-off frequency up to 200 Hz. Taking advantage of such a fast dynamic response, we demonstrate an X-ray based velocity tracking system.

Simulation of Space Charge Dynamic in Polyethylene Under DC Continuous Electrical Stress

NASA Astrophysics Data System (ADS)

Boukhari, Hamed; Rogti, Fatiha

2016-10-01

The space charge dynamic plays a very important role in the aging and breakdown of polymeric insulation materials under high voltage. This is due to the intensification of the local electric field and the attendant chemical-mechanical effects in the vicinity around the trapped charge. In this paper, we have investigated the space charge dynamic in low-density polyethylene under high direct-current voltage, which is evaluated by experimental conditions. The evaluation is on the basis of simulation using a bipolar charge transport model consisting of charge injection, transports, trapping, detrapping, and recombination phenomena. The theoretical formulation of the physical problem is based on the Poisson, the continuity, and the transport equations. Numerical results provide temporal and local distributions of the electric field, the space charge density for the different kinds of charges (net charge density, mobile and trapped of electron density, mobile hole density), conduction and displacement current densities, and the external current. The result shows the appearance of the negative packet-like space charge with a large amount of the bulk under the dc electric field of 100 kV/mm, and the induced distortion of the electric field is largely near to the anode, about 39% higher than the initial electric field applied.

Efficient charge injection in p-type polymer field-effect transistors with low-cost molybdenum electrodes through V2O5 interlayer.

PubMed

Baeg, Kang-Jun; Bae, Gwang-Tae; Noh, Yong-Young

2013-06-26

Here we report high-performance polymer OFETs with a low-cost Mo source/drain electrode by efficient charge injection through the formation of a thermally deposited V2O5 thin film interlayer. A thermally deposited V2O5 interlayer is formed between a regioregular poly(3-hexylthiophene) (rr-P3HT) or a p-type polymer semiconductor containing dodecyl-substituted thienylenevinylene (TV) and dodecylthiophene (PC12TV12T) and the Mo source/drain electrode. The P3HT or PC12TV12T OFETs with the bare Mo electrode exhibited lower charge carrier mobility than those with Au owing to a large barrier height for hole injection (0.5-1.0 eV). By forming the V2O5 layer, the P3HT or PC12TV12T OFETs with V2O5 on the Mo electrode exhibited charge carrier mobility comparable to that of a pristine Au electrode. Best P3HT or PC12TV12T OFETs with 5 nm thick V2O5 on Mo electrode show the charge carrier mobility of 0.12 and 0.38 cm(2)/(V s), respectively. Ultraviolet photoelectron spectroscopy results exhibited the work-function of the Mo electrode progressively changed from 4.3 to 4.9 eV with an increase in V2O5 thickness from 0 to 5 nm, respectively. Interestingly, the V2O5-deposited Mo exhibits comparable Rc to Au, which mainly results from the decreased barrier height for hole carrier injection from the low-cost metal electrode to the frontier molecular orbital of the p-type polymer semiconductor after the incorporation of the transition metal oxide hole injection layer, such as V2O5. This enables the development of large-area, low-cost electronics with the Mo electrodes and V2O5 interlayer.

Evaluation of economic efficiencies in clinical retina practice: activity-based cost analysis and modeling to determine impacts of changes in patient management

PubMed Central

Murray, Timothy G; Tornambe, Paul; Dugel, Pravin; Tong, Kuo Bianchini

2011-01-01

Background The purpose of this study is to report the use of activity-based cost analysis to identify areas of practice efficiencies and inefficiencies within a large academic retinal center and a small single-specialty group. This analysis establishes a framework for evaluating rapidly shifting clinical practices (anti-vascular endothelial growth factor therapy, microincisional vitrectomy surgery) and incorporating changing reimbursements for care delivery (intravitreal injections, optical coherence tomography [OCT]) to determine the impact on practice profitability. Pro forma modeling targeted the impact of declining reimbursement for OCT imaging and intravitreal injection using a strategy that incorporates activity-based cost analysis into a direct evaluation schema for clinical operations management. Methods Activity-based costing analyses were performed at two different types of retinal practices in the US, ie, a small single-specialty group practice and an academic hospital-based practice (Bascom Palmer Eye Institute). Retrospective claims data were utilized to identify all procedures performed and billed, submitted charges, allowed charges, and net collections from each of these two practices for the calendar years 2005–2006 and 2007–2008. A pro forma analysis utilizing current reimbursement profiles was performed to determine the impact of altered reimbursement on practice profitability. All analyses were performed by a third party consulting firm. Results The small single-specialty group practice outperformed the academic hospital-based practice on almost all markers of efficiency. In the academic hospital-based practice, only four service lines were profitable, ie, nonlaser surgery, laser surgery, non-OCT diagnostics, and injections. Profit margin varied from 62% for nonlaser surgery to 1% for intravitreal injections. Largest negative profit contributions were associated with office visits and OCT imaging. Conclusion Activity-based cost analysis is a powerful tool to evaluate retinal practice efficiencies. These two distinct practices were able to provide significant increases in clinical care (office visits, ophthalmic imaging, and patient procedures) through maintaining efficiencies of care. Pro forma analysis of 2011 data noted that OCT payments to facilities and physicians continue to decrease dramatically and that this payment decrease further reduced the profitability for the two largest aspects of these retinal practices, ie, intravitreal injections and OCT retinal imaging. Ultimately, all retinal practices are at risk for significant shifts in financial health related to rapidly evolving changes in patterns of care and reimbursement associated with providing outstanding clinical care. PMID:21792278

Potential mapping with charged-particle beams

NASA Technical Reports Server (NTRS)

Robinson, J. W.; Tillery, D. G.

1979-01-01

Experimental methods of mapping the equipotential surfaces near some structure of interest rely on the detection of charged particles which have traversed the regions of interest and are detected remotely. One method is the measurement of ion energies for ions created at a point of interest and expelled from the region by the fields. The ion energy at the detector in eV corresponds to the potential where the ion was created. An ionizing beam forms the ions from background neutrals. The other method is to inject charged particles into the region of interest and to locate their exit points. A set of several trajectories becomes a data base for a systematic mapping technique. An iterative solution of a boundary value problem establishes concepts and limitations pertaining to the mapping problem.

Current at Metal-Organic Interfaces

NASA Astrophysics Data System (ADS)

Kern, Klaus

2012-02-01

Charge transport through atomic and molecular constrictions greatly affects the operation and performance of organic electronic devices. Much of our understanding of the charge injection and extraction processes in these systems relays on our knowledge of the electronic structure at the metal-organic interface. Despite significant experimental and theoretical advances in studying charge transport in nanoscale junctions, a microscopic understanding at the single atom/molecule level is missing. In the present talk I will present our recent results to probe directly the nanocontact between single molecules and a metal electrode using scanning probe microscopy and spectroscopy. The experiments provide unprecedented microscopic details of single molecule and atom junctions and open new avenues to study quantum critical and many body phenomena at the atomic scale. Implications for energy conversion devices and carbon based nanoelectronics will also be discussed.

PNEUMATIC MICROVALVE FOR ELECTROKINETIC SAMPLE PRECONCENTRATION AND CAPILLARY ELECTROPHORESIS INJECTION

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cong, Yongzheng; Rausch, Sarah J.; Geng, Tao

2014-10-27

Here we show that a closed pneumatic microvalve on a PDMS chip can serve as a semipermeable membrane under an applied potential, enabling current to pass through while blocking the passage of charged analytes. Enrichment of both anionic and cationic species has been demonstrated, and concentration factors of ~70 have been achieved in just 8 s. Once analytes are concentrated, the valve is briefly opened and the sample is hydrodynamically injected onto an integrated microchip or capillary electrophoresis (CE) column. In contrast to existing preconcentration approaches, the membrane-based method described here enables both rapid analyte concentration as well as highmore » resolution separations.« less

Extracting dielectric fixed charge density on highly doped crystalline-silicon surfaces using photoconductance measurements

NASA Astrophysics Data System (ADS)

To, A.; Hoex, B.

2017-11-01

A novel method for the extraction of fixed interface charge, Qf, and the surface recombination parameters, Sn0 and Sp0, from the injection-level dependent effective minority carrier lifetime measurements is presented. Unlike conventional capacitance-voltage measurements, this technique can be applied to highly doped surfaces provided the surface carrier concentration transitions into strong depletion or inversion with increased carrier injection. By simulating the injection level dependent Auger-corrected inverse lifetime curve of symmetrically passivated and diffused samples after sequential annealing and corona charging, it was revealed that Qf, Sn0, and Sp0 have unique signatures. Therefore, these important electronic parameters, in some instances, can independently be resolved. Furthermore, it was shown that this non-linear lifetime behaviour is exhibited on both p-type and n-type diffused inverted surfaces, by demonstrating the approach with phosphorous diffused n+pn+ structures and boron diffused p+np+ structures passivated with aluminium oxide (AlOx) and silicon nitride, respectively (SiNx). The results show that the approximation of a mid-gap Shockley-Read-Hall defect level with equal capture cross sections is able to, in the samples studied in this work, reproduce the observed injection level dependent lifetime behaviour.

Summary Report of H- Injection Session II

DOE Office of Scientific and Technical Information (OSTI.GOV)

Weiren Chou

1999-06-28

The H - injection was invented many years ago and has since been successfully applied in many machines over the last decades. The challenge to the high intensity machines is how to reduce the injection loss, which is usually the major part of total beam losses in a machine. Painting, both longitudinal and transverse, is an effective way to reduce the space charge e ects and to minimize losses. RF capture of a chopped beam also gives better e ciency than adiabatic capture. To employ a 2nd harmonic rf system to atten the rf bucket shape is another commonly usedmore » scheme. To compensate the capacitive space charge impedance by an inductive insert could be a new venture, but which is not discussed at the workshop due to time limitation. The foil physics is well understood. Simulations seem to be able to include all the important e ects in it, including the space charge. The general feeling is that we are in a good position concerning H - injection studies. Although there remains a number of design issues, the knowledge, experiences and tools in our hand should be able to address each of them properly.« less

Non-local electrical spin injection and detection in germanium at room temperature

NASA Astrophysics Data System (ADS)

Rortais, F.; Vergnaud, C.; Marty, A.; Vila, L.; Attané, J.-P.; Widiez, J.; Zucchetti, C.; Bottegoni, F.; Jaffrès, H.; George, J.-M.; Jamet, M.

2017-10-01

Non-local carrier injection/detection schemes lie at the very foundation of information manipulation in integrated systems. This paradigm consists in controlling with an external signal the channel where charge carriers flow between a "source" and a well separated "drain." The next generation electronics may operate on the spin of carriers in addition to their charge and germanium appears as the best hosting material to develop such a platform for its compatibility with mainstream silicon technology and the predicted long electron spin lifetime at room temperature. In this letter, we demonstrate injection of pure spin currents (i.e., with no associated transport of electric charges) in germanium, combined with non-local spin detection at 10 K and room temperature. For this purpose, we used a lateral spin valve with epitaxially grown magnetic tunnel junctions as spin injector and spin detector. The non-local magnetoresistance signal is clearly visible and reaches ≈15 mΩ at room temperature. The electron spin lifetime and diffusion length are 500 ps and 1 μm, respectively, the spin injection efficiency being as high as 27%. This result paves the way for the realization of full germanium spintronic devices at room temperature.

High-temperature fusion of a multielectron leviton

NASA Astrophysics Data System (ADS)

Moskalets, Michael

2018-04-01

The state of electrons injected onto the surface of the Fermi sea depends on temperature. The state is pure at zero temperature and is mixed at finite temperature. In the case of a single-electron injection, such a transformation can be detected as a decrease in shot noise with increasing temperature. In the case of a multielectron injection, the situation is subtler. The mixedness helps the development of quantum-mechanical exchange correlations between injected electrons, even if such correlations are absent at zero temperature. These correlations enhance the shot noise, which in part counteracts the reduction of noise with temperature. Moreover, at sufficiently high temperatures, the correlation contribution to noise predominates over the contribution of individual particles. As a result, in the system of N electrons, the apparent charge (which is revealed via the shot noise) is changed from e at zero temperature to N e at high temperatures. It looks like the exchange correlations glue electrons into one particle of total charge and energy. This point of view is supported by both charge noise and heat noise. Interestingly, in the macroscopic limit, N →∞ , the correlation contribution completely suppresses the effect of temperature on noise.

Giant Gating Tunability of Optical Refractive Index in Transition Metal Dichalcogenide Monolayers.

PubMed

Yu, Yiling; Yu, Yifei; Huang, Lujun; Peng, Haowei; Xiong, Liwei; Cao, Linyou

2017-06-14

We report that the refractive index of transition metal dichacolgenide (TMDC) monolayers, such as MoS 2 , WS 2 , and WSe 2 , can be substantially tuned by >60% in the imaginary part and >20% in the real part around exciton resonances using complementary metal-oxide-semiconductor (CMOS) compatible electrical gating. This giant tunablility is rooted in the dominance of excitonic effects in the refractive index of the monolayers and the strong susceptibility of the excitons to the influence of injected charge carriers. The tunability mainly results from the effects of injected charge carriers to broaden the spectral width of excitonic interband transitions and to facilitate the interconversion of neutral and charged excitons. The other effects of the injected charge carriers, such as renormalizing bandgap and changing exciton binding energy, only play negligible roles. We also demonstrate that the atomically thin monolayers, when combined with photonic structures, can enable the efficiencies of optical absorption (reflection) tuned from 40% (60%) to 80% (20%) due to the giant tunability of the refractive index. This work may pave the way toward the development of field-effect photonics in which the optical functionality can be controlled with CMOS circuits.

An Analysis of Conjugate Ground-based and Space-based Measurements of Energetic Electrons during Substorms

NASA Astrophysics Data System (ADS)

Sivadas, N.; Semeter, J. L.

2015-12-01

Substorms within the Earth's magnetosphere release energy in the form of energetic charged particles and several kinds of waves within the plasma. Depending on their strength, satellite-based navigation and communication systems are adversely affected by the energetic charged particles. Like many other natural phenomena, substorms can have a severe economic impact on a technology-driven society such as ours. Though energization of charged particles is known to occur in the magnetosphere during substorms, the source of this population and its relation to traditional acceleration region dynamics, are not completely understood. Combining measurements of energetic charged particles within the plasmasheet and that of charged particles precipitated in to the ionosphere will provide a better understanding of the role of processes that accelerate these charged particles. In the current work, we present energetic electron flux measured indirectly using data from ground-based Incoherent Scatter Radar and that measured directly at the plasmasheet by the THEMIS spacecraft. Instances of low-altitude-precipitation observed from ground suggest electrons of energy greater than 300 keV, possibly arising from particle injection events during substorms at the magnetically conjugate locations in the plasmasheet. The differences and similarities in the measurements at the plasmasheet and the ionosphere indicate the role different processes play in influencing the journey of these energetic particles form the magnetosphere to the ionosphere. Our observations suggest that there is a lot more to be understood of the link between magnetotail dynamics and energetic electron precipitation during substorms. Understanding this may open up novel and potentially invaluable ways of diagnosing the magnetosphere from the ground.

The thermally stimulated discharge of ion-irradiated oxide films

NASA Astrophysics Data System (ADS)

Wang, Qiuru; Zeng, Huizhong; Zhang, Wanli

2018-01-01

The ion irradiation technique is utilized to modify the surface structure of amorphous insulating oxide films. While introducing defects, a number of surface charges are injected into the films and captured in the traps during ion irradiation. The variation of surface morphology and the enhancement of emission spectrum corresponding to vacancy defects are respectively verified by atomic force microscopy and photoluminescence measurements. The surface charges trapped in the shallow traps are easy to release caused by thermal excitation, and discharge is observed during heating. Based on the thermally stimulated discharge measurements, the trap parameters of oxide films, such as activation energy and relaxation time, are calculated from experimental data.

Characterization of polylactic co-glycolic acid nanospheres modified with PVA and DDAB

NASA Astrophysics Data System (ADS)

Mulia, Kamarza; Satyapertiwi, Dwiantari; Devina, Ranee; Krisanti, Elsa

2017-02-01

The common treatment for diabetic retinopathy is corticosteroids intravitreal injection that sometimes lead to complications. Dexamethasone-loaded polylactic co-glycolic acid (PLGA) nanospheres, modified with dioctadecyldimethylammonium bromide (DDAB) as the cationic surfactant, is expected to prolong drug retention time. Zeta potential of the PLGA nanospheres prepared using non-ionic surfactant PVA and DDAB confirmed the cationic surfactant increase the surface charge of the PLGA nanospheres. The optimal formulation based on the particle size and high positive surface charge was the PLGA-DDAB nanospheres. SEM analysis showed spherical morphology of the nanospheres having diameter 626.9 ± 98.01 nm positive zeta potential of +22.5 mV.

Production of large resonant plasma volumes in microwave electron cyclotron resonance ion sources

DOEpatents

Alton, Gerald D.

1998-01-01

Microwave injection methods for enhancing the performance of existing electron cyclotron resonance (ECR) ion sources. The methods are based on the use of high-power diverse frequency microwaves, including variable-frequency, multiple-discrete-frequency, and broadband microwaves. The methods effect large resonant "volume" ECR regions in the ion sources. The creation of these large ECR plasma volumes permits coupling of more microwave power into the plasma, resulting in the heating of a much larger electron population to higher energies, the effect of which is to produce higher charge state distributions and much higher intensities within a particular charge state than possible in present ECR ion sources.

Greatly Increasing Trapped Ion Populations for Mobility Separations Using Traveling Waves in Structures for Lossless Ion Manipulations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Deng, Liulin; Ibrahim, Yehia M.; Garimella, Sandilya V. B.

The initial use of traveling waves (TW) for ion mobility (IM) separations using a structures for lossless ion manipulations (SLIM) employed an ion funnel trap (IFT) to accumulate ions from a continuous electrospray ionization source, and limited to injected ion populations of ~106 charges due to the onset of space charge effects in the trapping region. Additional limitations arise due to the loss of resolution for the injection of ions over longer periods (e.g. in extended pulses). In this work a new SLIM ‘flat funnel’ (FF) module has been developed and demonstrated to enable the accumulation of much larger ionmore » populations and their injection for IM separations. Ion current measurements indicate a capacity of ~3.2×108 charges for the extended trapping volume, over an order of magnitude greater than the IFT. The orthogonal ion injection into a funnel shaped separation region can greatly reduce space charge effects during the initial IM separation stage, and the gradually reduced width of the path allows the ion packet to be increasingly compressed in the lateral dimension as the separation progresses, allowing e.g. efficient transmission through conductance limits or compatibility with subsequent ion manipulations. This work examined the TW, RF, and DC confining field SLIM parameters involved in ion accumulation, injection, transmission and separation in the FF IM module using both direct ion current and MS measurements. Wide m/z range ion transmission is demonstrated, along with significant increases in signal to noise (S/N) ratios due to the larger ion populations injected. Additionally, we observed a reduction in the chemical background, which was attributed to more efficient desolvation of solvent related clusters over the extended ion accumulation periods. The TW SLIM FF IM module is anticipated to be especially effective as a front end for long path SLIM IM separation modules.« less

Space charge characteristics of fluorinated polyethylene: Different effects of fluorine and oxygen

NASA Astrophysics Data System (ADS)

Zhao, Ni; Nie, Yongjie; Li, Shengtao

2018-04-01

Direct fluorination are proved having obvious effect on space charge characteristics of polyethylene. It is believed that fluorine has a positive effect on suppressing space charge injection while oxygen impurity has a negative effect. However, the mechanism for the opposite effect of fluorine and oxygen is still not clear. In this paper, the different effects of fluorine and oxygen on space charge characteristics of fluorinated low density polyethylene (LDPE) are investigated on the basis of dielectric property, chemical constitutes and trap performance of surface fluorinated layers. The results show that direct fluorination has obvious effect on chemical constitutes and dielectric properties of surface fluorinated layer. Introduced fluorine is the main factor for suppressing charge injection from the electrodes, because it seriously changes the chemical constitutes and further the trap properties of the surface fluorinated layer. While introduction of oxygen results in heterocharges and makes space charge distribution complex, due to the ionization of generated small groups like C=O containing groups. Moreover, direct fluorination will result in cleavage of some LDPE molecules whatever there is oxygen impurity or not.

Effect of Premixed Fuel Preparation for Partially Premixed Combustion with a Low Octane Gasoline on a Light-Duty Multi-Cylinder Compression Ignition Engine

DOE PAGES

Dempsey, Adam B.; Curran, Scott; Wagner, Robert M.; ...

2015-05-12

Gasoline compression ignition concepts with the majority of the fuel being introduced early in the cycle are known as partially premixed combustion (PPC). Previous research on single- and multi-cylinder engines has shown that PPC has the potential for high thermal efficiency with low NOx and soot emissions. A variety of fuel injection strategies has been proposed in the literature. These injection strategies aim to create a partially stratified charge to simultaneously reduce NOx and soot emissions while maintaining some level of control over the combustion process through the fuel delivery system. The impact of the direct injection strategy to createmore » a premixed charge of fuel and air has not previously been explored, and its impact on engine efficiency and emissions is not well understood. This paper explores the effect of sweeping the direct injected pilot timing from -91° to -324° ATDC, which is just after the exhaust valve closes for the engine used in this study. During the sweep, the pilot injection consistently contained 65% of the total fuel (based on command duration ratio), and the main injection timing was adjusted slightly to maintain combustion phasing near top dead center. A modern four cylinder, 1.9 L diesel engine with a variable geometry turbocharger, high pressure common rail injection system, wide included angle injectors, and variable swirl actuation was used in this study. The pistons were modified to an open bowl configuration suitable for highly premixed combustion modes. The stock diesel injection system was unmodified, and the gasoline fuel was doped with a lubricity additive to protect the high pressure fuel pump and the injectors. The study was conducted at a fixed speed/load condition of 2000 rpm and 4.0 bar brake mean effective pressure (BMEP). The pilot injection timing sweep was conducted at different intake manifold pressures, swirl levels, and fuel injection GTP-15-1067, Dempsey 2 pressures. The gasoline used in this study has relatively high fuel reactivity with a research octane number of 68. The results of this experimental campaign indicate that the highest brake thermal efficiency and lowest emissions are achieved simultaneously with the earliest pilot injection timings (i.e., during the intake stroke).« less

Charge transfer and injection barrier at the metal-organic interfaces

NASA Astrophysics Data System (ADS)

Yan, Li

2002-09-01

The metal-organic interface plays a critical role in determining the functionality and performance of many innovative organic based devices. It has attracted extensive research interests in recent years. This thesis presents investigations of the electronic structures of organic materials, such as tris-(8-hydroxyquinoline) aluminum (Alq3) and copper phthalocyanine (CuPc), during their interface formation with metals. The characterization is accomplished by X-ray and ultraviolet photoelectron spectroscopes (XPS and UPS) and inverse photoelectron spectroscopy (IPES). As discussed herein, both occupied and unoccupied electronic states at the interfaces are carefully examined in different aspects. In Chapter 4, the charge transfer and chemical reaction at various metal/Alq3 interfaces are investigated using XPS and UPS to study the electron injection into the Alga film. Electron transfer from the low work function metal and Al/LiF(CsF) bilayer to the Alga has been observed. The role of the dielectric and possible chemistry at the interface are discussed in comparison of the low work function metals. Further in Chapter 5, the origin of the metal-interface dipole and the estimation of charge injection barrier is explored using several organic materials. A thermodynamic equilibrium model is extended to explain the relation between the charge transfer process ad the interface dipole. Further, in Chapter 6 the combination of XPS, UPS and IPES detailed the evolution of both occupied and unoccupied energy states during the alkali metal doping. The energy gap modification in organic due to metal doping is observed directly for the spectra. Chapter 7 provides stability study of the organic thin films under x-ray and UV light. The results verify the usability of UPS and XPS for the organic materials used in the thesis. Chapter 7 also shows the secondary ion mass spectroscopy results of metal diffusion in organic thin films.

Effect of Molecular Coupling on Ultrafast Electron-Transfer and Charge-Recombination Dynamics in a Wide-Gap ZnS Nanoaggregate Sensitized by Triphenyl Methane Dyes.

PubMed

Debnath, Tushar; Maity, Partha; Dana, Jayanta; Ghosh, Hirendra N

2016-03-03

Wide-band-gap ZnS nanocrystals (NCs) were synthesized, and after sensitizing the NCs with series of triphenyl methane (TPM) dyes, ultrafast charge-transfer dynamics was demonstrated. HRTEM images of ZnS NCs show the formation of aggregate crystals with a flower-like structure. Exciton absorption and lumimescence, due to quantum confinement of the ZnS NCs, appear at approximately 310 and 340 nm, respectively. Interestingly, all the TPM dyes (pyrogallol red, bromopyrogallol red, and aurin tricarboxylic acid) form charge-transfer complexes with the ZnS NCs, with the appearance of a red-shifted band. Electron injection from the photoexcited TPM dyes into the conduction band of the ZnS NCs is shown to be a thermodynamically viable process, as confirmed by steady-state and time-resolved emission studies. To unravel charge-transfer (both electron injection and charge recombination) dynamics and the effect of molecular coupling, femtosecond transient absorption studies were carried out in TPM-sensitized ZnS NCs. The electron-injection dynamics is pulse-width-limited in all the ZnS/TPM dye systems, however, the back electron transfer differs, depending on the molecular coupling of the sensitizers (TPM dyes). The detailed mechanisms for the above-mentioned processes are discussed. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Invalidity of the Fermi liquid theory and magnetic phase transition in quasi-1D dopant-induced armchair-edged graphene nanoribbons

NASA Astrophysics Data System (ADS)

Hoi, Bui Dinh; Davoudiniya, Masoumeh; Yarmohammadi, Mohsen

2018-04-01

Based on theoretically tight-binding calculations considering nearest neighbors and Green's function technique, we show that the magnetic phase transition in both semiconducting and metallic armchair graphene nanoribbons with width ranging from 9.83 Å to 69.3 Å would be observed in the presence of injecting electrons by doping. This transition is explained by the temperature-dependent static charge susceptibility through calculation of the correlation function of charge density operators. This work showed that charge concentration of dopants in such system plays a crucial role in determining the magnetic phase. A variety of multicritical points such as transition temperatures and maximum susceptibility are compared in undoped and doped cases. Our findings show that there exist two different transition temperatures and maximum susceptibility depending on the ribbon width in doped structures. Another remarkable point refers to the invalidity (validity) of the Fermi liquid theory in nanoribbons-based systems at weak (strong) concentration of dopants. The obtained interesting results of magnetic phase transition in such system create a new potential for magnetic graphene nanoribbon-based devices.

Injection Locking of a Semiconductor Double Quantum Dot Micromaser

PubMed Central

Liu, Y.-Y.; Stehlik, J.; Gullans, M. J.; Taylor, J. M.; Petta, J. R.

2016-01-01

Emission linewidth is an important figure of merit for masers and lasers. We recently demonstrated a semiconductor double quantum dot (DQD) micromaser where photons are generated through single electron tunneling events. Charge noise directly couples to the DQD energy levels, resulting in a maser linewidth that is more than 100 times larger than the Schawlow-Townes prediction. Here we demonstrate a linewidth narrowing of more than a factor 10 by locking the DQD emission to a coherent tone that is injected to the input port of the cavity. We measure the injection locking range as a function of cavity input power and show that it is in agreement with the Adler equation. The position and amplitude of distortion sidebands that appear outside of the injection locking range are quantitatively examined. Our results show that this unconventional maser, which is impacted by strong charge noise and electron-phonon coupling, is well described by standard laser models. PMID:28127226

Injection Locking of a Semiconductor Double Quantum Dot Micromaser.

PubMed

Liu, Y-Y; Stehlik, J; Gullans, M J; Taylor, J M; Petta, J R

2015-11-01

Emission linewidth is an important figure of merit for masers and lasers. We recently demonstrated a semiconductor double quantum dot (DQD) micromaser where photons are generated through single electron tunneling events. Charge noise directly couples to the DQD energy levels, resulting in a maser linewidth that is more than 100 times larger than the Schawlow-Townes prediction. Here we demonstrate a linewidth narrowing of more than a factor 10 by locking the DQD emission to a coherent tone that is injected to the input port of the cavity. We measure the injection locking range as a function of cavity input power and show that it is in agreement with the Adler equation. The position and amplitude of distortion sidebands that appear outside of the injection locking range are quantitatively examined. Our results show that this unconventional maser, which is impacted by strong charge noise and electron-phonon coupling, is well described by standard laser models.

Novel nano-OLED based probes for very high resolution optical microscopy

NASA Astrophysics Data System (ADS)

Zhao, Yiying

Near-field scanning optical microscopy (NSOM) has been applied in the study of nanomaterials, microelectronics, photonics, plasmonics, cells, and molecules. However, conventional NSOM relies on optically pumped probes, suffering low optical transmission, heating of the tip, and poor reproducibility of probe fabrication, increasing the cost, impeding usability, reducing practical imaging resolution, and limiting NSOM's utility. In this thesis, I demonstrate a novel probe based on a nanoscale, electrically pumped organic light-emitting device (OLED) formed on the tip of a low-cost, commercially available atomic force microscopy (AFM) probe. I describe the structure, fabrication, and principles of this novel probe's operation, and discuss its potential to overcome the limitations of conventional NSOM probes. The broader significance of this work in the field of organic optoelectronics is also discussed. Briefly, OLEDs consist of organic thin films sandwiched between two electrodes. Under bias, electrons and holes are injected into the organic layers, leading to radiative recombination. Depositing a small molecular OLED in vacuum onto a pyramid-tipped AFM probe results in a laminar structure that is highly curved at the tip. Simple electrical modeling predicts concentration of electric field and localized electron injection into the organic layers at the tip, improving the local charge balance in an otherwise electron-starved OLED. Utilizing an "inverted" OLED structure (i.e. cathode on the "bottom"), light emission is localized to sub-200 nm sized, green light emitting regions on probe vertices; light output power in the range of 0.1-0.5 nanowatts was observed, comparable to that of typical fiber based NSOM probes but with greater power efficiency. Massive arrays of similar sub-micron OLEDs were also fabricated by depositing onto textured silicon substrates, demonstrating the superior scalability of the probe fabrication process (e.g. relative to pulled glass fibers). The investigation of the effect of non-planar substrate geometry on charge injection, transport and recombination provides broader insights into OLEDs made on rough substrates, general understanding of OLED operation (e.g. filamentary charge conduction) and degradation, and potentially helps to improve technologically important "inverted" OLED structures.

A Yellow-Emitting Homoleptic Iridium(III) Complex Constructed from a Multifunctional Spiro Ligand for Highly Efficient Phosphorescent Organic Light-Emitting Diodes.

PubMed

Ren, Bao-Yi; Guo, Run-Da; Zhong, Dao-Kun; Ou, Chang-Jin; Xiong, Gang; Zhao, Xiang-Hua; Sun, Ya-Guang; Jurow, Matthew; Kang, Jun; Zhao, Yi; Li, Sheng-Biao; You, Li-Xin; Wang, Lin-Wang; Liu, Yi; Huang, Wei

2017-07-17

To suppress concentration quenching and to improve charge-carrier injection/transport in the emission layer (EML) of phosphorescent organic light-emitting diodes (PhOLEDs), a facial homoleptic iridium(III) complex emitter with amorphous characteristics was designed and prepared in one step from a multifunctional spiro ligand containing spiro[fluorene-9,9'-xanthene] (SFX) unit. Single-crystal X-ray analysis of the resulting fac-Ir(SFXpy) 3 complex revealed an enlarged Ir···Ir distance and negligible intermolecular π-π interactions between the spiro ligands. The emitter exhibits yellow emission and almost equal energy levels compared to the commercial phosphor iridium(III) bis(4-phenylthieno[3,2-c]pyridinato-N,C 2 ')acetylacetonate (PO-01). Dry-processed devices using a common host, 4,4'-bis(N-carbazolyl)-1,1'-biphenyl, and the fac-Ir(SFXpy) 3 emitter at a doping concentration of 15 wt % exhibited a peak performance of 46.2 cd A -1 , 36.3 lm W -1 , and 12.1% for the current efficiency (CE), power efficiency (PE), and external quantum efficiency (EQE), respectively. Compared to control devices using PO-01 as the dopant, the fac-Ir(SFXpy) 3 -based devices remained superior in the doping range between 8 and 15 wt %. The current densities went up with increasing doping concentration at the same driving voltage, while the roll-offs remain relatively low even at high doping levels. The superior performance of the new emitter-based devices was ascribed to key roles of the spiro ligand for suppressing aggregation and assisting charge-carrier injection/transport. Benefiting from the amorphous stability of the emitter, the wet-processed device also exhibited respectful CE, PE, and EQE of 32.2 cd A -1 , 22.1 lm W -1 , and 11.3%, respectively, while the EQE roll-off was as low as 1.7% at the luminance of 1000 cd m -2 . The three-dimensional geometry and binary-conjugation features render SFX the ideal multifunctional module for suppressing concentration quenching, facilitating charge-carrier injection/transport, and improving the amorphous stability of iridium(III)-based phosphorescent emitters.

Effect of electrode materials on the space charge distribution of an Al2O3 nano-modified transformer oil under impulse voltage conditions

NASA Astrophysics Data System (ADS)

Yang, Qing; Liu, Mengna; Sima, Wenxia; Jin, Yang

2017-11-01

The combined effect mechanism of electrode materials and Al2O3 nanoparticles on the insulating characteristics of transformer oil was investigated. Impulse breakdown tests of pure transformer oil and Al2O3 nano-modified transformer oil of varying concentrations with different electrode materials (brass, aluminum and stainless steel) showed that the breakdown voltage of Al2O3 nano-modified transformer oil is higher than that of pure transformer oil and there is a there is an optimum concentration for Al2O3 nanoparticles when the breakdown voltage reaches the maximum. In addition, the breakdown voltage was highest with the brass electrode, followed by that with stainless steel and then aluminum, irrespective of the concentration of nanoparticles in the transformer oil. This is explained by the charge injection patterns from different electrode materials according to the results of space charge measurements in pure and nano-modified transformer oil using the Kerr electro-optic system. The test results indicate that there are electrode-dependent differences in the charge injection patterns and quantities and then the electric field distortion, which leads to the difference breakdown strength in result. As for the nano-modified transformer oil, due to the Al2O3 nanoparticle’s ability of shielding space charges of different polarities and the charge injection patterns of different electrodes, these two factors have different effects on the electric field distribution and breakdown process of transformer oil between different electrode materials. This paper provides a feasible approach to exploring the mechanism of the effect of the electrode material and nanoparticles on the breakdown strength of liquid dielectrics and analyzing the breakdown process using the space charge distribution.

Molecularly "engineered" anode adsorbates for probing OLED interfacial structure-charge injection/luminance relationships: large, structure-dependent effects.

PubMed

Huang, Qinglan; Evmenenko, Guennadi; Dutta, Pulak; Marks, Tobin J

2003-12-03

Molecule-scale structure effects at organic light-emitting diodes (OLED) anode-organic transport layer interfaces are probed via a self-assembly approach. A series of ITO anode-linked silyltriarylamine molecules differing in aryl group and linker density are synthesized for this purpose and used to probe the relationship between nanoscale interfacial chemical structure, charge injection and electroluminescence properties. Dramatic variations in hole injection magnitude and OLED performance can be correlated with the molecular structures and electrochemically derived heterogeneous electron-transfer rates of such triarylamine fragments, placed precisely at the anode-hole transport layer interface. Very bright and efficient ( approximately 70 000 cd/m2 and approximately 2.5% forward external quantum efficiency) OLEDs have thereby been fabricated.

Transient Response in a Dendritic Neuron Model for Current Injected at One Branch

PubMed Central

Rinzel, John; Rall, Wilfrid

1974-01-01

Mathematical expressions are obtained for the response function corresponding to an instantaneous pulse of current injected to a single dendritic branch in a branched dendritic neuron model. The theoretical model assumes passive membrane properties and the equivalent cylinder constraint on branch diameters. The response function when used in a convolution formula enables one to compute the voltage transient at any specified point in the dendritic tree for an arbitrary current injection at a given input location. A particular numerical example, for a brief current injection at a branch terminal, illustrates the attenuation and delay characteristics of the depolarization peak as it spreads throughout the neuron model. In contrast to the severe attenuation of voltage transients from branch input sites to the soma, the fraction of total input charge actually delivered to the soma and other trees is calculated to be about one-half. This fraction is independent of the input time course. Other numerical examples, which compare a branch terminal input site with a soma input site, demonstrate that, for a given transient current injection, the peak depolarization is not proportional to the input resistance at the injection site and, for a given synaptic conductance transient, the effective synaptic driving potential can be significantly reduced, resulting in less synaptic current flow and charge, for a branch input site. Also, for the synaptic case, the two inputs are compared on the basis of the excitatory post-synaptic potential (EPSP) seen at the soma and the total charge delivered to the soma. PMID:4424185

Molecular Engineering for Enhanced Charge Transfer in Thin-Film Photoanode.

PubMed

Kim, Jeong Soo; Kim, Byung-Man; Kim, Un-Young; Shin, HyeonOh; Nam, Jung Seung; Roh, Deok-Ho; Park, Jun-Hyeok; Kwon, Tae-Hyuk

2017-10-11

We developed three types of dithieno[3,2-b;2',3'-d]thiophene (DTT)-based organic sensitizers for high-performance thin photoactive TiO 2 films and investigated the simple but powerful molecular engineering of different types of bonding between the triarylamine electron donor and the conjugated DTT π-bridge by the introduction of single, double, and triple bonds. As a result, with only 1.3 μm transparent and 2.5-μm TiO 2 scattering layers, the triple-bond sensitizer (T-DAHTDTT) shows the highest power conversion efficiency (η = 8.4%; V OC = 0.73 V, J SC = 15.4 mA·cm -2 , and FF = 0.75) in an iodine electrolyte system under one solar illumination (AM 1.5, 1000 W·m -2 ), followed by the single-bond sensitizer (S-DAHTDTT) (η = 7.6%) and the double-bond sensitizer (D-DAHTDTT) (η = 6.4%). We suggest that the superior performance of T-DAHTDTT comes from enhanced intramolecular charge transfer (ICT) induced by the triple bond. Consequently, T-DAHTDTT exhibits the most active photoelectron injection and charge transport on a TiO 2 film during operation, which leads to the highest photocurrent density among the systems studied. We analyzed these correlations mainly in terms of charge injection efficiency, level of photocharge storage, and charge-transport kinetics. This study suggests that the molecular engineering of a triple bond between the electron donor and the π-bridge of a sensitizer increases the performance of dye-sensitized solar cell (DSC) with a thin photoactive film by enhancing not only J SC through improved ICT but also V OC through the evenly distributed sensitizer surface coverage.

Dielectric-Particle Injector For Processing Of Materials

NASA Technical Reports Server (NTRS)

Leung, Philip L.; Gabriel, Stephen B.

1992-01-01

Device generates electrically charged particles of solid, or droplets of liquid, fabricated from dielectric material and projects them electrostatically, possibly injecting them into electrostatic-levitation chamber for containerless processing. Dielectric-particle or -droplet injector charges dielectric particles or droplets on zinc plate with photo-electrons generated by ultraviolet illumination, then ejects charged particles or droplets electrostatically from plate.

Carbazole/triarylamine based polymers as a hole injection/transport layer in organic light emitting devices.

PubMed

Wang, Hui; Ryu, Jeong-Tak; Kwon, Younghwan

2012-05-01

This study examined the influence of the charge injection barriers on the performance of organic light emitting diodes (OLEDs) using polymers with a stepwise tuned ionization potential (I(p) approximately -5.01 - -5.29 eV) between the indium tin oxide (ITO) (phi approximately -4.8 eV) anode and tris(8-hydroxyquinolinato) aluminium (Alq3) (I(p) approximately -5.7 eV) layer. The energy levels of the polymers were tuned by structural modification. Double layer devices were fabricated with a configuration of ITO/polymer/Alq3/LiF/Al, where the polymers, Alq3, and LiF/Al were used as the hole injection/transport layer, emissive electron transport layer, and electron injection/cathode, respectively. Using the current density-voltage (J-V), luminescence-voltage (L-V) and efficiencies in these double layer devices, the device performance was evaluated in terms of the energy level alignments at the interfaces, such as the hole injection barriers (phi(h)(iTO/polymer) and phi(h)(polymer/Alq3)) from ITO through the polymers into the Alq3 layer, and the electron injection barrier (phi(e)(polymer/Alq3) or electron/exciton blocking barrier) at the polymer/Alq3 interface.

Conjugated ionomers for photovoltaic applications: electric field driven charge separation in organic photovoltaics. Final Technical report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lonergan, Mark

Final technical report for Conjugated ionomers for photovoltaic applications, electric field driven charge separation in organic photovoltaics. The central goal of the work we completed was been to understand the photochemical and photovoltaic properties of ionically functionalized conjugated polymers (conjugated ionomers or polyelectrolytes) and energy conversion systems based on them. We primarily studied two classes of conjugated polymer interfaces that we developed based either upon undoped conjugated polymers with an asymmetry in ionic composition (the ionic junction) or doped conjugated polymers with an asymmetry in doping type (the p-n junction). The materials used for these studies have primarily been themore » polyacetylene ionomers. We completed a detailed study of p-n junctions with systematically varying dopant density, photochemical creation of doped junctions, and experimental and theoretical work on charge transport and injection in polyacetylene ionomers. We have also completed related work on the use of conjugated ionomers as interlayers that improve the efficiency or organic photovoltaic systems and studied several important aspects of the chemistry of ionically functionalized semiconductors, including mechanisms of so-called "anion-doping", the formation of charge transfer complexes with oxygen, and the synthesis of new polyfluorene polyelectrolytes. We also worked worked with the Haley group at the University of Oregon on new indenofluorene-based organic acceptors.« less

Sol-gel-derived double-layered nanocrystal memory

NASA Astrophysics Data System (ADS)

Ko, Fu-Hsiang; You, Hsin-Chiang; Lei, Tan-Fu

2006-12-01

The authors have used the sol-gel spin-coating method to fabricate a coexisting hafnium silicate and zirconium silicate double-layered nanocrystal (NC) memories. From transmission electron microscopic and x-ray photoelectron spectroscopic analyses, the authors determined that the hafnium silicate and zirconium silicate NCs formed after annealing at 900°C for 1min. When using channel hot electron injection for charging and band-to-band tunneling-induced hot hole injection for discharging, the NC memories exhibited superior Vth shifting because of the higher probability for trapping the charge carrier.

Peritoneal retention of liposomes: Effects of lipid composition, PEG coating and liposome charge.

PubMed

Dadashzadeh, S; Mirahmadi, N; Babaei, M H; Vali, A M

2010-12-01

In the treatment of peritoneal carcinomatosis, systemic chemotherapy is not quite effective due to the poor penetration of cytotoxic agents into the peritoneal cavity, whereas intraperitoneal administration of chemotherapeutic agents is generally accompanied by quick absorption of the free drug from the peritoneum. Local delivery of drugs with controlled-release delivery systems like liposomes could provide sustained, elevated drug levels and reduce local and systemic toxicity. In order to achieve an ameliorated liposomal formulation that results in higher peritoneal levels of the drug and retention, vesicles composed of different phospholipid compositions (distearoyl [DSPC]; dipalmitoyl [DPPC]; or dimiristoylphosphatidylcholine [DMPC]) and various charges (neutral; negative, containing distearoylphosphatidylglycerol [DSPG]; or positive, containing dioleyloxy trimethylammonium propane [DOTAP]) were prepared at two sizes of 100 and 1000nm. The effect of surface hydrophilicity was also investigated by incorporating PEG into the DSPC-containing neutral and charged liposomes. Liposomes were labeled with (99m)Tc and injected into mouse peritoneum. Mice were then sacrificed at eight different time points, and the percentage of injected radiolabel in the peritoneal cavity and the tissue distribution in terms of the percent of the injected dose/gram of tissue (%ID/g) were obtained. The ratio of the peritoneal AUC to the free label ranged from a minimum of 4.95 for DMPC/CHOL (cholesterol) 100nm vesicles to a maximum of 24.99 for DSPC/CHOL/DOTAP 1000nm (DOTAP 1000) vesicles. These last positively charged vesicles had the greatest peritoneal level; moreover, their level remained constant at approximately 25% of the injected dose from 2 to 48h. Among the conventional (i.e., without PEG) 100nm liposomes, the positively charged vesicles again showed the greatest retention. Incorporation of PEG at this size into the lipid structures augmented the peritoneal level, particularly for negatively charged liposomes. The positively charged PEGylated vesicles (DOTAP/PEG 100) had the second-greatest peritoneal level after DOTAP 1000; however, their peritoneal-to-blood AUC ratio was low (3.05). Overall, among the different liposomal formulations, the positively charged conventional liposomes (100 and 1000nm) provided greater peritoneal levels and retention. DOTAP/PEG100 may also be a more efficient formulation because this formulation can provide a high level of anticancer drug into the peritoneal cavity and also can passively target the primary tumor. Copyright © 2010 Elsevier B.V. All rights reserved.

EHD Approach to Tornadic Thunderstorms and Methods of Their Destruction

NASA Astrophysics Data System (ADS)

Kikuchi, H.

2005-05-01

In many cases, tornadoes are accompanied or involved by lightning discharges and are thought to be com- posed of uncharged and charged components different from each other in terms of velocity, vorticity, heli- city, and appearance (shape and luminosity). Their visible dark portion may correspond to uncharged tor- nadoes, while luminous or bright part may involve charged tornadoes with return strokes. Usually, un- charged tornadoes have been considered to be ascending hot streams of thermohydrodynamic origin. This is the conventional theory of tornadoes, based on hydrodynamics (HD) or thermohydrodynamics (THD) but does not consider electrical effects that are really significant in tornadic thunderstorms..It has been shown, however, that a new electrohydrodynamics (EHD) established and developed over the last more than a decade is applicable to tornadic thunderstorms with lightning. This paper summarizes such an EHD approach and proposes the methods of tornado destruction based on EHD. Space charge and electric field configurations in tornadic thunderstorms are considered to be quadrupole-like, taking into account the cloud-charge images onto the ground. Accordingly, dynamics of particles and EHD flows in an electric quadrupole forming an electric cusp and mirror can straightly apply to those circumstances. When the gas pressure is below the breakdown threshold, there occur helical motion of particles, not only charged but also even uncharged, and/or vortex generation. While for gases whose pressure is beyond the breakdown threshold, the following basic processes succeed one after another. When the grain is uncharged, a dis- charge channel is formed towards each pole as a result of X-type reconnection. For a negatively or posi- tively charged grain, I-type reconnection occurs between the grain and positive or negative poles, respect- ively. For uncharged two grains, O-type reconnection between both grains could be involved in addition to X-type between each pole, while for oppositely charged two grains, F-type reconnection could be in- volved between grains in addition to I-type between each grain and a pole with opposite polarity. Thus one can say that the uncharged component of tornadic thunderstorms is composed of conventional ascending hot streams of thermohydrodynamic origin and particle flows of new EHD origin produced by a quadru- pole-like cloud-base, funnel-top charge distributions, while the charged component is a bunch of return strokes including charged flows due to dust-related electric reconnection and EHD vortices in large-scale generated by EHD helical turbulence where there may occur self-organization to coalescence of fluid vor- tex and electric displacement field lines at least in an initial stage of return stroke (rise time of some ms), since earth's magnetic field could be ignored. This also indicates that fluid vortex breakdown points also tend to merge electric cusps, X-type and O-type. Then the principle of dust-related electric reconnection could be replaced by dust cluster injection into electric cusps (X-type and O-type) in several ways just mentioned above. Thus a variety of such dust cluster injection could cause additional cloud-to-dust cluster discharges, expending electrostatic energy accumulated in thunderclouds considerably and destructing tornadoes consequently.

Characterization of silicon detectors through TCT at Delhi University

NASA Astrophysics Data System (ADS)

Jain, G.; Lalwani, K.; Dalal, R.; Bhardwaj, A.; Ranjan, K.

2016-07-01

Transient Current Technique (TCT) is one of the important methods to characterize silicon detectors and is based on the time evolution of the charge carriers generated when a laser light is shone on it. For red laser, charge is injected only to a small distance from the surface of the detector. For such a system, one of the charge carriers is collected faster than the readout time of the electronics and therefore, the effective signal at the electrodes is decided by the charge carriers that traverse throughout the active volume of the detector, giving insight to the electric field profile, drift velocity, effective doping density, etc. of the detector. Delhi University is actively involved in the silicon detector R&D and has recently installed a TCT setup consisting of a red laser system, a Faraday cage, a SMU (Source Measuring Unit), a bias tee, and an amplifier. Measurements on a few silicon pad detectors have been performed using the developed system, and the results have been found in good agreement with the CERN setup.

Fabrication of solid-state secondary battery using semiconductors and evaluation of its charge/discharge characteristics

NASA Astrophysics Data System (ADS)

Sasaki, Atsuya; Sasaki, Akito; Hirabayashi, Hideaki; Saito, Shuichi; Aoki, Katsuaki; Kataoka, Yoshinori; Suzuki, Koji; Yabuhara, Hidehiko; Ito, Takahiro; Takagi, Shigeyuki

2018-04-01

Li-ion batteries have attracted interest for use as storage batteries. However, the risk of fire has not yet been resolved. Although solid Li-ion batteries are possible alternatives, their performance characteristics are unsatisfactory. Recently, research on utilizing the accumulation of carriers at the trap levels of semiconductors has been performed. However, the detailed charge/discharge characteristics and principles have not been reported. In this report, we attempted to form new n-type oxide semiconductor/insulator/p-type oxide semiconductor structures. The battery characteristics of these structures were evaluated by charge/discharge measurements. The obtained results clearly indicated the characteristics of rechargeable batteries. Furthermore, the fabricated structure accumulated an approximately 5000 times larger number of carriers than a parallel plate capacitor. Additionally, by constructing circuit models based on the experimental results, the charge/discharge mechanisms were considered. This is the first detailed experimental report on a rechargeable battery that operates without the double injection of ions and electrons.

On the mechanisms of cation injection in conducting bridge memories: The case of HfO{sub 2} in contact with noble metal anodes (Au, Cu, Ag)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Saadi, M.; CNRS, LTM, F-38000 Grenoble; El Manar University, LMOP, 2092 Tunis

Resistance switching is studied in HfO{sub 2} as a function of the anode metal (Au, Cu, and Ag) in view of its application to resistive memories (resistive random access memories, RRAM). Current-voltage (I-V) and current-time (I-t) characteristics are presented. For Au anodes, resistance transition is controlled by oxygen vacancies (oxygen-based resistive random access memory, OxRRAM). For Ag anodes, resistance switching is governed by cation injection (Conducting Bridge random access memory, CBRAM). Cu anodes lead to an intermediate case. I-t experiments are shown to be a valuable tool to distinguish between OxRRAM and CBRAM behaviors. A model is proposed to explainmore » the high-to-low resistance transition in CBRAMs. The model is based on the theory of low-temperature oxidation of metals (Cabrera-Mott theory). Upon electron injection, oxygen vacancies and oxygen ions are generated in the oxide. Oxygen ions are drifted to the anode, and an interfacial oxide is formed at the HfO{sub 2}/anode interface. If oxygen ion mobility is low in the interfacial oxide, a negative space charge builds-up at the HfO{sub 2}/oxide interface. This negative space charge is the source of a strong electric field across the interfacial oxide thickness, which pulls out cations from the anode (CBRAM case). Inversely, if oxygen ions migration through the interfacial oxide is important (or if the anode does not oxidize such as Au), bulk oxygen vacancies govern resistance transition (OxRRAM case).« less

Defect Generation for a Hydrated Layer and Thermal Stability Based on Ba0.7Sr0.3TiO3/SiO2 as H+ Sensitive Layer in Ion-Sensitive Field-Effect Transistor Devices

NASA Astrophysics Data System (ADS)

Chen, Chun-Yuan; Chou, Jung-Chuan; Chou, Hsueh-Tao

2009-04-01

In this paper, we present a novel sensitive ion-sensitive field-effect transistor (ISFET) membrane based on Ba0.7Sr0.3TiO3 (BST)/SiO2 fabricated by sputtering deposition. The proposed device exhibits a linear shift in acidic solutions in the pH range from 1 to 10. The device sensitivity was about 50-55 mV/pH for different deposition times. We also examined the trapping behavior of the surface hydrated layer using the metal-insulator-semiconductor (MIS) structure. Results show that the hydration layer gives rise to stress polarity dependence of electron injection when immersed in pH buffer solutions. Injection from the gate electrode produces larger positive charges and interface state densities in contrast to the substrate injection, which causes simultaneous positive and negative charge trapping. A physical model that quantitatively describes the asymmetry associated with the hydrated diffusion layer is presented, and the temperature effects of BST/SiO2 ISFET devices in the range from 25 to 65 °C were examined. We observed that pH sensitivity increases with increasing temperature. The temperature coefficient of sensitivity (TCS) can be divided into two different ranges: 0.08 mV/pH °C between 25 and 45 °C, and 0.57 mV/pH °C between 45 and 65 °C. A better thermal stability is produced in the 25 and 45 °C range in comparison with other sensitive layers.

Charge exchange cooling in the tandem mirror plasma confinement apparatus

DOEpatents

Logan, B. Grant

1978-01-01

Method and apparatus for cooling a plasma of warm charged species confined in the center mirror cell of the tandem mirror apparatus by injecting cold neutral species of the plasma into at least one mirroring region of the center mirror cell, the cooling due to the loss of warm charged species through charge exchange with the cold neutral species with resulting diffusion of the warm neutral species out of the plasma.

Generation of tunable, high repetition rate optical frequency combs using on-chip silicon modulators

NASA Astrophysics Data System (ADS)

Nagarjun, K. P.; Jeyaselvan, Vadivukarassi; Selvaraja, Shankar Kumar; Supradeepa, V. R.

2018-04-01

We experimentally demonstrate tunable, highly-stable frequency combs with high repetition-rates using a single, charge injection based silicon PN modulator. In this work, we demonstrate combs in the C-band with over 8 lines in a 20-dB bandwidth. We demonstrate continuous tuning of the center frequency in the C-band and tuning of the repetition-rate from 7.5GHz to 12.5GHz. We also demonstrate through simulations the potential for bandwidth scaling using an optimized silicon PIN modulator. We find that, the time varying free carrier absorption due to carrier injection, an undesirable effect in data modulators, assists here in enhancing flatness in the generated combs.

A high-altitude barium radial injection experiment

NASA Technical Reports Server (NTRS)

Wescott, E. M.; Stenbaek-Nielsen, H. C.; Hallinan, T. J.; Deehr, C. S.; Romick, G. J.; Olson, J. V.; Roederer, J. G.; Sydora, R.

1980-01-01

A rocket launched from Poker Flat, Alaska, carried a new type of high-explosive barium shaped charge to 571 km, where detonation injected a thin disk of barium vapor with high velocity nearly perpendicular to the magnetic field. The TV images of the injection are spectacular, revealing three major regimes of expanding plasma which showed early instabilities in the neutral gas. The most unusual effect of the injection is a peculiar rayed barium-ion structure lying in the injection plane and centered on a 5 km 'black hole' surrounding the injection point. Preliminary electrostatic computer simulations show a similar rayed development.

Simulation study of signal formation in position sensitive planar p-on-n silicon detectors after short range charge injection

NASA Astrophysics Data System (ADS)

Peltola, T.; Eremin, V.; Verbitskaya, E.; Härkönen, J.

2017-09-01

Segmented silicon detectors (micropixel and microstrip) are the main type of detectors used in the inner trackers of Large Hadron Collider (LHC) experiments at CERN. Due to the high luminosity and eventual high fluence of energetic particles, detectors with fast response to fit the short shaping time of 20-25 ns and sufficient radiation hardness are required. Charge collection measurements carried out at the Ioffe Institute have shown a reversal of the pulse polarity in the detector response to short-range charge injection. Since the measured negative signal is about 30-60% of the peak positive signal, the effect strongly reduces the CCE even in non-irradiated detectors. For further investigation of the phenomenon the measurements have been reproduced by TCAD simulations. As for the measurements, the simulation study was applied for the p-on-n strip detectors similar in geometry to those developed for the ATLAS experiment and for the Ioffe Institute designed p-on-n strip detectors with each strip having a window in the metallization covering the p+ implant, allowing the generation of electron-hole pairs under the strip implant. Red laser scans across the strips and the interstrip gap with varying laser diameters and Si-SiO2 interface charge densities (Qf) were carried out. The results verify the experimentally observed negative response along the scan in the interstrip gap. When the laser spot is positioned on the strip p+ implant the negative response vanishes and the collected charge at the active strip increases respectively. The simulation results offer a further insight and understanding of the influence of the oxide charge density in the signal formation. The main result of the study is that a threshold value of Qf, that enables negligible losses of collected charges, is defined. The observed effects and details of the detector response for different charge injection positions are discussed in the context of Ramo's theorem.

The injection of microorganisms into an atmospheric pressure rf-driven microplasma

NASA Astrophysics Data System (ADS)

Maguire, P. D.; Mahony, C. M. O.; Diver, D.; Mariotti, D.; Bennet, E.; Potts, H.; McDowell, D. A.

2013-09-01

The introduction of living organisms, such as bacteria, into atmospheric pressure microplasmas offers a unique means to study certain physical mechanisms in individual microorganisms and also help understand the impact of macroscopic entities and liquid droplets on plasma characteristics. We present the characterization of an RF-APD operating at 13.56 MHz and containing microorganisms in liquid droplets emitted from a nebulizer, with the spray entrained in a gas flow by a gas shroud and passed into the plasma source. We report successful microorganism injection and transmission through the plasma with stable plasma operation of at least one hour. Diagnostics include RF electrical characterization, optical emission spectrometry and electrostatic deflection to investigate microorganism charging. A close-coupled Impedans Octiv VI probe indicates source efficiencies of 10 to 15%. The introduction of the droplets/microorganisms results in increased plasma conductivity and reduced capacitance, due to their impact on electron density and temperature. An electrical model will be presented based on diagnostic data and deflection studies with input from simulations of charged aerosol diffusion and evaporation. Engineering and Physical Sciences Research Council EP/K006088, EP/K006142.

Cationic microbubbles and antibiotic-free miniplasmid for sustained ultrasound-mediated transgene expression in liver.

PubMed

Manta, Simona; Renault, Gilles; Delalande, Anthony; Couture, Olivier; Lagoutte, Isabelle; Seguin, Johanne; Lager, Franck; Houzé, Pascal; Midoux, Patrick; Bessodes, Michel; Scherman, Daniel; Bureau, Michel-Francis; Marie, Corinne; Pichon, Chantal; Mignet, Nathalie

2017-09-28

Despite the increasing number of clinical trials in gene therapy, no ideal methods still allow non-viral gene transfer in deep tissues such as the liver. We were interested in ultrasound (US)-mediated gene delivery to provide long term liver expression. For this purpose, new positively charged microbubbles were designed and complexed with pFAR4, a highly efficient small length miniplasmid DNA devoid of antibiotic resistance sequence. Sonoporation parameters, such as insonation time, acoustic pressure and duration of plasmid injection were controlled under ultrasound imaging guidance. The optimization of these various parameters was performed by bioluminescence optical imaging of luciferase reporter gene expression in the liver. Mice were injected with 50μg pFAR4-LUC either alone, or complexed with positively charged microbubbles, or co-injected with neutral MicroMarker™ microbubbles, followed by low ultrasound energy application to the liver. Injection of the pFAR4 encoding luciferase alone led to a transient transgene expression that lasted only for two days. The significant luciferase signal obtained with neutral microbubbles decreased over 2days and reached a plateau with a level around 1 log above the signal obtained with pFAR4 alone. With the newly designed positively charged microbubbles, we obtained a much stronger bioluminescence signal which increased over 2days. The 12-fold difference (p<0.05) between MicroMarker™ and our positively charged microbubbles was maintained over a period of 6months. Noteworthy, the positively charged microbubbles led to an improvement of 180-fold (p<0.001) as regard to free pDNA using unfocused ultrasound performed at clinically tolerated ultrasound amplitude. Transient liver damage was observed when using the cationic microbubble-pFAR4 complexes and the optimized sonoporation parameters. Immunohistochemistry analyses were performed to determine the nature of cells transfected. The pFAR4 miniplasmid complexed with cationic microbubbles allowed to transfect mostly hepatocytes compared to its co-injection with MicroMarker™ which transfected more preferentially endothelial cells. Copyright © 2017 Elsevier B.V. All rights reserved.

An electron transporting unit linked multifunctional Ir(III) complex: a promising strategy to improve the performance of solution-processed phosphorescent organic light-emitting diodes.

PubMed

Giridhar, Thota; Saravanan, Chinnusamy; Cho, Woosum; Park, Young Geun; Lee, Jin Yong; Jin, Sung-Ho

2014-04-18

An oxadiazole based electron transporting (ET) unit was glued to the heteroleptic Ir(III) complex (TPQIr-ET) and used as a dopant for phosphorescent organic light-emitting diodes (PhOLEDs). It shows superior device performance than the dopant without the ET unit (TPQIr) due to the balanced charge carrier injection by the ET unit.

Production of large resonant plasma volumes in microwave electron cyclotron resonance ion sources

DOEpatents

Alton, G.D.

1998-11-24

Microwave injection methods are disclosed for enhancing the performance of existing electron cyclotron resonance (ECR) ion sources. The methods are based on the use of high-power diverse frequency microwaves, including variable-frequency, multiple-discrete-frequency, and broadband microwaves. The methods effect large resonant ``volume`` ECR regions in the ion sources. The creation of these large ECR plasma volumes permits coupling of more microwave power into the plasma, resulting in the heating of a much larger electron population to higher energies, the effect of which is to produce higher charge state distributions and much higher intensities within a particular charge state than possible in present ECR ion sources. 5 figs.

Nonvolatile floating gate organic memory device based on pentacene/CdSe quantum dot heterojuction

NASA Astrophysics Data System (ADS)

Shin, Ik-Soo; Kim, Jung-Min; Jeun, Jun-Ho; Yoo, Seok-Hyun; Ge, Ziyi; Hong, Jong-In; Ho Bang, Jin; Kim, Yong-Sang

2012-04-01

An organic floating-gate memory device using CdSe quantum dots (QDs) as a charge-trapping element was fabricated. CdSe QDs were localized beneath a pentacene without any tunneling insulator, and the QD layer played a role as hole-trapping sites. The band bending formed at the junction between pentacene and QD layers inhibited back-injection of holes trapped in CdSe into pentacene, which appeared as a hysteretic capacitance-voltage response during the operation of the device. Nearly, 60% of trapped charge was sustained even after 104 s in programmed state, and this long retention time can be potentially useful in practical applications of non-volatile memory.

Sharp plasma pinnacle structure based on shockwave for an improved laser wakefield accelerator

NASA Astrophysics Data System (ADS)

Fang, Ming; Zhang, Zhijun; Wang, Wentao; Liu, Jiansheng; Li, Ruxin

2018-07-01

We created a sharp plasma pinnacle structure for localized electron injection and controlled acceleration in a laser wakefield accelerator. The formation of this shockwave-based pinnacle structure was investigated using aerodynamic theory. Details and scaling laws for the shockwave angle, shock position, shock width, and density ratio were experimentally and theoretically presented. Such work is crucial to yielding an expected plasma density distribution in a laser–plasma experiment but has had little discussion in the literature. Compared with the commonly used shock downramp structure, the particle-in-cell simulations demonstrated that the e beam injected in the created pinnacle structure could be accelerated to higher energy with much smaller root-mean-square relative energy spread. Moreover, this study indicated that the beam charge and transverse emittance can be tuned by the shock angle.

Dissimilar viscosity induced sample pre-concentration in elecrokinetic nanofluidic channels

NASA Astrophysics Data System (ADS)

Wink, Dean; Shelton, Elijah; Pennathur, Sumita; Storey, Brian

2013-11-01

Nanofluidic analysis systems boast many advantages: portability, small sample handling, short processing times, and potential for integration with mobile electronics. However, such systems face the challenge of detecting increasingly small volumes of sample at low concentrations. In this work, we demonstrate a unique pre-concentration technique in electrokinetic nanofluidic systems based on a viscosity mismatch between two fluids. In nanofluidic electrokinetic systems, finite electric double layers (EDL) lead to non-uniform electric potentials and transverse concentration distributions. Therefore, when the EDL is comparable in size to the channel height, negatively charged ions are repelled from negatively charged walls and preferentially populate the channel centerline. Furthermore, an axial piecewise viscosity distribution induces internal pressure gradients within the channel. These force the ions to move at a different average velocities based on the pressure gradient being favorable or adverse, leading to focusing. To experimentally probe this phenomenon, we electrokinetically inject solutions of borate buffer with and without glycerol (to change the viscosity) and use a fluorescent tracer dye to visualize the flow. We perform the injections in cross-geometry channels of 20 micron, 1 micron, and 250 nanometer depths. We measure fluorescence at 5, 10 and 15 mm distances from junction. Enhancement is characterized by comparing intensities to control measurements for systems with uniform viscosity.

Exploring the validity and limitations of the Mott-Gurney law for charge-carrier mobility determination of semiconducting thin-films.

PubMed

Röhr, Jason A; Moia, Davide; Haque, Saif A; Kirchartz, Thomas; Nelson, Jenny

2018-03-14

Using drift-diffusion simulations, we investigate the voltage dependence of the dark current in single carrier devices typically used to determine charge-carrier mobilities. For both low and high voltages, the current increases linearly with the applied voltage. Whereas the linear current at low voltages is mainly due to space charge in the middle of the device, the linear current at high voltage is caused by charge-carrier saturation due to a high degree of injection. As a consequence, the current density at these voltages does not follow the classical square law derived by Mott and Gurney, and we show that for trap-free devices, only for intermediate voltages, a space-charge-limited drift current can be observed with a slope that approaches a value of two. We show that, depending on the thickness of the semiconductor layer and the size of the injection barriers, the two linear current-voltage regimes can dominate the whole voltage range, and the intermediate Mott-Gurney regime can shrink or disappear. In this case, which will especially occur for thicknesses and injection barriers typical of single-carrier devices used to probe organic semiconductors, a meaningful analysis using the Mott-Gurney law will become unachievable, because a square-law fit can no longer be achieved, resulting in the mobility being substantially underestimated. General criteria for when to expect deviations from the Mott-Gurney law when used for analysis of intrinsic semiconductors are discussed.

Exploring the validity and limitations of the Mott-Gurney law for charge-carrier mobility determination of semiconducting thin-films

NASA Astrophysics Data System (ADS)

Röhr, Jason A.; Moia, Davide; Haque, Saif A.; Kirchartz, Thomas; Nelson, Jenny

2018-03-01

Using drift-diffusion simulations, we investigate the voltage dependence of the dark current in single carrier devices typically used to determine charge-carrier mobilities. For both low and high voltages, the current increases linearly with the applied voltage. Whereas the linear current at low voltages is mainly due to space charge in the middle of the device, the linear current at high voltage is caused by charge-carrier saturation due to a high degree of injection. As a consequence, the current density at these voltages does not follow the classical square law derived by Mott and Gurney, and we show that for trap-free devices, only for intermediate voltages, a space-charge-limited drift current can be observed with a slope that approaches a value of two. We show that, depending on the thickness of the semiconductor layer and the size of the injection barriers, the two linear current-voltage regimes can dominate the whole voltage range, and the intermediate Mott-Gurney regime can shrink or disappear. In this case, which will especially occur for thicknesses and injection barriers typical of single-carrier devices used to probe organic semiconductors, a meaningful analysis using the Mott-Gurney law will become unachievable, because a square-law fit can no longer be achieved, resulting in the mobility being substantially underestimated. General criteria for when to expect deviations from the Mott-Gurney law when used for analysis of intrinsic semiconductors are discussed.

Störmer method for a problem of point injection of charged particles into a magnetic dipole field

NASA Astrophysics Data System (ADS)

Kolesnikov, E. K.

2017-03-01

The problem of point injection of charged particles into a magnetic dipole field was considered. Analytical expressions were obtained by the Störmer method for regions of allowed pulses of charged particles at random points of a dipole field at a set position of the point source of particles. It was found that, for a fixed location of the studied point, there was a specific structure of the coordinate space in the form of a set of seven regions, where the injector location in each region corresponded to a definite form of an allowed pulse region at the studied point. It was shown that the allowed region boundaries in four of the mentioned regions were surfaces of conic section revolution.

Modulation of the electronic property of phosphorene by wrinkle and vertical electric field

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Yan; Wei, Zhongming, E-mail: zmwei@semi.ac.cn; Li, Jingbo, E-mail: jbli@semi.ac.cn

2015-09-14

The electronic properties of wrinkled phosphorene and its response to charge injection and external vertical electric field have been studied using first-principles calculations. It is found that small-size wrinkle systems have lower energy than wrinkle-free monolayer, suggesting that free-standing phosphorene spontaneously forms small protrusion on its nanosheet. The ratio of wrinkle height to curvature radius increases with enlarging height, indicating a promotion of field enhancement factor. Furthermore, the injected charges mostly distribute at peak and valley. Direct-to-indirect band-gap transition has been found for zigzag wrinkle with height of 14.81 Å. The band gaps of wrinkled nanosheets decrease almost linearly with increasingmore » field, which is caused by charge separation of valence band maximum and conduction band minimum.« less

Design and evaluation of wide-range and low-power analog front-end enabling body-implanted devices to monitor charge injection properties

NASA Astrophysics Data System (ADS)

Ito, Keita; Uno, Shoma; Goto, Tatsuya; Takezawa, Yoshiki; Harashima, Takuya; Morikawa, Takumi; Nishino, Satoru; Kino, Hisashi; Kiyoyama, Koji; Tanaka, Tetsu

2017-04-01

For safe electrical stimulation with body-implanted devices, the degradation of stimulus electrodes must be considered because it causes the unexpected electrolysis of water and the destruction of tissues. To monitor the charge injection property (CIP) of stimulus electrodes while these devices are implanted, we have proposed a charge injection monitoring system (CIMS). CIMS can safely read out voltages produced by a biphasic current pulse to a stimulus electrode and CIP is calculated from waveforms of the acquired voltages. In this paper, we describe a wide-range and low-power analog front-end (AFE) for CIMS that has variable gain-frequency characteristics and low-power analog-to-digital (A/D) conversion to adjust to the degradation of stimulus electrodes. The designed AFE was fabricated with 0.18 µm CMOS technology and achieved a valuable gain of 20-60 dB, an upper cutoff frequency of 0.2-10 kHz, and low-power interleaving A/D conversion. In addition, we successfully measured the CIP of stimulus electrodes for body-implanted devices using CIMS.

Modification of anisotropic plasma diffusion via auxiliary electrons emitted by a carbon nanotubes-based electron gun in an electron cyclotron resonance ion source.

PubMed

Malferrari, L; Odorici, F; Veronese, G P; Rizzoli, R; Mascali, D; Celona, L; Gammino, S; Castro, G; Miracoli, R; Serafino, T

2012-02-01

The diffusion mechanism in magnetized plasmas is a largely debated issue. A short circuit model was proposed by Simon, assuming fluxes of lost particles along the axial (electrons) and radial (ions) directions which can be compensated, to preserve the quasi-neutrality, by currents flowing throughout the conducting plasma chamber walls. We hereby propose a new method to modify Simon's currents via electrons injected by a carbon nanotubes-based electron gun. We found this improves the source performances, increasing the output current for several charge states. The method is especially sensitive to the pumping frequency. Output currents for given charge states, at different auxiliary electron currents, will be reported in the paper and the influence of the frequency tuning on the compensation mechanism will be discussed.

Organic integrated circuits for information storage based on ambipolar polymers and charge injection engineering

NASA Astrophysics Data System (ADS)

Dell'Erba, Giorgio; Luzio, Alessandro; Natali, Dario; Kim, Juhwan; Khim, Dongyoon; Kim, Dong-Yu; Noh, Yong-Young; Caironi, Mario

2014-04-01

Ambipolar semiconducting polymers, characterized by both high electron (μe) and hole (μh) mobility, offer the advantage of realizing complex complementary electronic circuits with a single semiconducting layer, deposited by simple coating techniques. However, to achieve complementarity, one of the two conduction paths in transistors has to be suppressed, resulting in unipolar devices. Here, we adopt charge injection engineering through a specific interlayer in order to tune injection into frontier energy orbitals of a high mobility donor-acceptor co-polymer. Starting from field-effect transistors with Au contacts, showing a p-type unbalanced behaviour with μh = 0.29 cm2/V s and μe = 0.001 cm2/V s, through the insertion of a caesium salt interlayer with optimized thickness, we obtain an n-type unbalanced transistor with μe = 0.12 cm2/V s and μh = 8 × 10-4 cm2/V s. We applied this result to the development of the basic pass-transistor logic building blocks such as inverters, with high gain and good noise margin, and transmission-gates. In addition, we developed and characterized information storage circuits like D-Latches and D-Flip-Flops consisting of 16 transistors, demonstrating both their static and dynamic performances and thus the suitability of this technology for more complex circuits such as display addressing logic.

Gated charged-particle trap

DOEpatents

Benner, W.H.

1999-03-09

The design and operation of a new type of charged-particle trap provides simultaneous measurements of mass, charge, and velocity of large electrospray ions. The trap consists of a detector tube mounted between two sets of center-bored trapping plates. Voltages applied to the trapping plates define symmetrically-opposing potential valleys which guide axially-injected ions to cycle back and forth through the charge-detection tube. A low noise charge-sensitive amplifier, connected to the tube, reproduces the image charge of individual ions as they pass through the detector tube. Ion mass is calculated from measurement of ion charge and velocity following each passage through the detector. 5 figs.

Quantum dot solar cells. Tuning photoresponse through size and shape control of CdSe-TiO2 architecture.

PubMed

Kongkanand, Anusorn; Tvrdy, Kevin; Takechi, Kensuke; Kuno, Masaru; Kamat, Prashant V

2008-03-26

Different-sized CdSe quantum dots have been assembled on TiO2 films composed of particle and nanotube morphologies using a bifunctional linker molecule. Upon band-gap excitation, CdSe quantum dots inject electrons into TiO2 nanoparticles and nanotubes, thus enabling the generation of photocurrent in a photoelectrochemical solar cell. The results presented in this study highlight two major findings: (i) ability to tune the photoelectrochemical response and photoconversion efficiency via size control of CdSe quantum dots and (ii) improvement in the photoconversion efficiency by facilitating the charge transport through TiO2 nanotube architecture. The maximum IPCE (photon-to-charge carrier generation efficiency) obtained with 3 nm diameter CdSe nanoparticles was 35% for particulate TiO2 and 45% for tubular TiO2 morphology. The maximum IPCE observed at the excitonic band increases with decreasing particle size, whereas the shift in the conduction band to more negative potentials increases the driving force and favors fast electron injection. The maximum power-conversion efficiency

Interfacial charge separation and photovoltaic efficiency in Fe(ii)-carbene sensitized solar cells.

PubMed

Pastore, Mariachiara; Duchanois, Thibaut; Liu, Li; Monari, Antonio; Assfeld, Xavier; Haacke, Stefan; Gros, Philippe C

2016-10-12

The first combined theoretical and photovoltaic characterization of both homoleptic and heteroleptic Fe(ii)-carbene sensitized photoanodes in working dye sensitized solar cells (DSSCs) has been performed. Three new heteroleptic Fe(ii)-NHC dye sensitizers have been synthesized, characterized and tested. Despite an improved interfacial charge separation in comparison to the homoleptic compounds, the heteroleptic complexes did not show boosted photovoltaic performances. The ab initio quantitative analysis of the interfacial electron and hole transfers and the measured photovoltaic data clearly evidenced fast recombination reactions for heteroleptics, even associated with un unfavorable directional electron flow, and hence slower injection rates, in the case of homoleptics. Notably, quantum mechanics calculations revealed that deprotonation of the not anchored carboxylic function in the homoleptic complex can effectively accelerate the electron injection rate and completely suppress the electron recombination to the oxidized dye. This result suggests that introduction of strong electron-donating substituents on the not-anchored carbene ligand in heteroleptic complexes, in such a way of mimicking the electronic effects of the carboxylate functionality, should yield markedly improved interfacial charge generation properties. The present results, providing for the first time a detailed understanding of the interfacial electron transfers and photovoltaic characterization in Fe(ii)-carbene sensitized solar cells, open the way to a rational molecular engineering of efficient iron-based dyes for photoelectrochemical applications.

First charge breeding results at CARIBU EBIS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kondrashev, S., E-mail: kondrashev@anl.gov; Barcikowski, A., E-mail: kondrashev@anl.gov; Dickerson, C., E-mail: kondrashev@anl.gov

The Electron Beam Ion Source (EBIS) developed to breed CARIBU radioactive beams at ATLAS is currently in the off-line commissioning stage. The beam commissioning is being performed using a low emittance surface ionization source producing singly-charged cesium ions. The primary goal of the off-line commissioning is the demonstration of high-efficiency charge breeding in the pulsed injection mode. An overview of the final design of the CARIBU EBIS charge breeder, the off-line commissioning installation and the first results on charge breeding of stable cesium ions are presented and discussed.

Low intrinsic carrier density LSMO/Alq3/AlOx/Co organic spintronic devices

NASA Astrophysics Data System (ADS)

Riminucci, Alberto; Graziosi, Patrizio; Calbucci, Marco; Cecchini, Raimondo; Prezioso, Mirko; Borgatti, Francesco; Bergenti, Ilaria; Dediu, Valentin Alek

2018-04-01

The understanding of spin injection and transport in organic spintronic devices is still incomplete, with some experiments showing magnetoresistance and others not detecting it. We have investigated the transport properties of a large number of tris-(8-hydroxyquinoline)aluminum-based organic spintronic devices with an electrical resistance greater than 5 MΩ that did not show magnetoresistance. Their transport properties could be described satisfactorily by known models for organic semiconductors. At high voltages (>2 V), the results followed the model of space charge limited current with a Poole-Frenkel mobility. At low voltages (˜0.1 V), that are those at which the spin valve behavior is usually observed, the charge transport was modelled by nearest neighbor hopping in intra-gap impurity levels, with a charge carrier density of n0 = (1.44 ± 0.21) × 1015 cm-3 at room temperature. Such a low carrier density can explain why no magnetoresistance was observed.

A Nonmetal Plasmonic Z-Scheme Photocatalyst with UV- to NIR-Driven Photocatalytic Protons Reduction.

PubMed

Zhang, Zhenyi; Huang, Jindou; Fang, Yurui; Zhang, Mingyi; Liu, Kuichao; Dong, Bin

2017-05-01

Ultrabroad-spectrum absorption and highly efficient generation of available charge carriers are two essential requirements for promising semiconductor-based photocatalysts, towards achieving the ultimate goal of solar-to-fuel conversion. Here, a fascinating nonmetal plasmonic Z-scheme photocatalyst with the W 18 O 49 /g-C 3 N 4 heterostructure is reported, which can effectively harvest photon energies spanning from the UV to the nearinfrared region and simultaneously possesses improved charge-carrier dynamics to boost the generation of long-lived active electrons for the photocatalytic reduction of protons into H 2 . By combining with theoretical simulations, a unique synergistic photocatalysis effect between the semiconductive Z-scheme charge-carrier separation and metal-like localized-surface-plasmon-resonance-induced "hot electrons" injection process is demonstrated within this binary heterostructure. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Space experiments with particle accelerators

NASA Technical Reports Server (NTRS)

Obayashi, T.; Kawashima, N.; Kuriki, K.; Nagatomo, M.; Ninomiya, K.; Sasaki, S.; Roberts, W. T.; Chappell, C. R.; Reasoner, D. L.; Garriott, O. K.;

Non-local opto-electrical spin injection and detection in germanium at room temperature

NASA Astrophysics Data System (ADS)

Jamet, Matthieu; Rortais, Fabien; Zucchetti, Carlo; Ghirardini, Lavinia; Ferrari, Alberto; Vergnaud, Celine; Widiez, Julie; Marty, Alain; Attane, Jean-Philippe; Jaffres, Henri; George, Jean-Marie; Celebrano, Michele; Isella, Giovanni; Ciccacci, Franco; Finazzi, Marco; Bottegoni, Federico

Non-local charge carriers injection/detection schemes lie at the foundation of information manipulation in integrated systems. The next generation electronics may operate on the spin instead of the charge and germanium appears as the best hosting material to develop such spintronics for its compatibility with mainstream silicon technology and long spin lifetime at room temperature. Moreover, the energy proximity between the direct and indirect bandgaps allows for optical spin orientation. In this presentation, we demonstrate injection of pure spin currents in Ge, combined with non-local spin detection blocks at room temperature. Spin injection is performed either electrically through a magnetic tunnel junction (MTJ) or optically, by using lithographed nanostructures to diffuse the light and create an in-plane polarized electron spin population. Pure spin current detection is achieved using either a MTJ or the inverse spin-Hall effect across a Pt stripe. Supported by the ANR project SiGeSPIN #ANR-13-BS10-0002 and the CARIPLO project SEARCH-IV (Grant 2013-0623).

First experience with carbon stripping foils for the 160 MeV H- injection into the CERN PSB

NASA Astrophysics Data System (ADS)

Weterings, Wim; Bracco, Chiara; Jorat, Louise; Noulibos, Remy; van Trappen, Pieter

2018-05-01

160 MeV H- beam will be delivered from the new CERN linear accelerator (Linac4) to the Proton Synchrotron Booster (PSB), using a H- charge-exchange injection system. A 200 µg/cm2 carbon stripping foil will convert H- into protons by stripping off the electrons. The H- charge-exchange injection principle will be used for the first time in the CERN accelerator complex and involves many challenges. In order to gain experience with the foil changing mechanism and the very fragile foils, in 2016, prior to the installation in the PSB, a stripping foil test stand has been installed in the Linac4 transfer line. In addition, parts of the future PSB injection equipment are also temporarily installed in the Linac4 transfer line for tests with a 160 MeV H- commissioning proton beam. This paper describes the foil changing mechanism and control system, summarizes the practical experience of gluing and handling these foils and reports on the first results with beam.

"Vivo para consumirla y la consumo para vivir" ["I live to inject and inject to live"]: high-risk injection behaviors in Tijuana, Mexico.

PubMed

Strathdee, Steffanie A; Fraga, Wendy Davila; Case, Patricia; Firestone, Michelle; Brouwer, Kimberly C; Perez, Saida Gracia; Magis, Carlos; Fraga, Miguel Angel

2005-09-01

Injection drug use is a growing problem on the US-Mexico border, where Tijuana is situated. We studied the context of injection drug use among injection drug users (IDUs) in Tijuana to help guide future research and interventions. Guided in-depth interviews were conducted with 10 male and 10 female current IDUs in Tijuana. Topics included types of drug used, injection settings, access to sterile needles, and environmental influences. Interviews were taped, transcribed verbatim, and translated. Content analysis was conducted to identify themes. Of the 20 IDUs, median age and age at first injection were 30 and 18. Most reported injecting at least daily: heroin ("carga", "chiva", "negra"), methamphetamine ("crico", "cri-cri"), or both drugs combined. In sharp contrast to Western US cities, almost all regularly attended shooting galleries ("yongos" or "picaderos") because of the difficulties obtaining syringes and police oppression. Almost all shared needles/paraphernalia ["cuete" (syringe), "cacharros" (cookers), cotton from sweaters/socks (filters)]. Some reported obtaining syringes from the United States. Key themes included (1) pharmacies refusing to sell or charging higher prices to IDUs, (2) ample availability of used/rented syringes from "picaderos" (e.g., charging approximately 5 pesos or "10 drops" of drug), and (3) poor HIV/AIDS knowledge, such as beliefs that exposing syringes to air "kills germs." This qualitative study suggests that IDUs in Tijuana are at high risk of HIV and other blood-borne infections. Interventions are urgently needed to expand access to sterile injection equipment and offset the potential for a widespread HIV epidemic.

Performance and combustion characteristics of direct-injection stratified-charge rotary engines

NASA Technical Reports Server (NTRS)

Nguyen, Hung Lee

1987-01-01

Computer simulations of the direct-injection stratified-charge (DISC) Wankel engine have been used to calculate heat release rates and performance and efficiency characteristics of the 1007R engine. Engine pressure data have been used in a heat release analysis to study the effects of heat transfer, leakage, and crevice flows. Predicted engine performance data are compared with experimental test data over a range of engine speeds and loads. An examination of methods to improve the performance of the Wankel engine with faster combustion, reduced leakage, higher compression ratio, and turbocharging is presented.

Local Charge Injection and Extraction on Surface-Modified Al2O3 Nanoparticles in LDPE.

PubMed

Borgani, Riccardo; Pallon, Love K H; Hedenqvist, Mikael S; Gedde, Ulf W; Haviland, David B

2016-09-14

We use a recently developed scanning probe technique to image with high spatial resolution the injection and extraction of charge around individual surface-modified aluminum oxide nanoparticles embedded in a low-density polyethylene (LDPE) matrix. We find that the experimental results are consistent with a simple band structure model where localized electronic states are available in the band gap (trap states) in the vicinity of the nanoparticles. This work offers experimental support to a previously proposed mechanism for enhanced insulating properties of nanocomposite LDPE and provides a powerful experimental tool to further investigate such properties.

Estimation of instantaneous heat transfer coefficients for a direct-injection stratified-charge rotary engine

NASA Technical Reports Server (NTRS)

Lee, C. M.; Addy, H. E.; Bond, T. H.; Chun, K. S.; Lu, C. Y.

1987-01-01

The main objective of this report was to derive equations to estimate heat transfer coefficients in both the combustion chamber and coolant pasage of a rotary engine. This was accomplished by making detailed temperature and pressure measurements in a direct-injection stratified-charge rotary engine under a range of conditions. For each sppecific measurement point, the local physical properties of the fluids were calculated. Then an empirical correlation of the coefficients was derived by using a multiple regression program. This correlation expresses the Nusselt number as a function of the Prandtl number and Reynolds number.

The ionic charge of Copper-64 complexes conjugated to an engineered antibody effects biodistribution

DOE PAGES

Dearling, Jason L. J.; Smith, Suzanne V.; Paterson, Brett M.; ...

2015-04-15

The development of biomolecules as imaging probes requires radiolabeling methods that do not significantly influence their biodistribution. Sarcophagine (Sar) chelators form extremely stable complexes with copper, and are therefore a promising option for labeling proteins with ⁶⁴Cu. However, initial studies using the first-generation sarcophagine bifunctional chelator SarAr to label the engineered antibody fragment ch14.18-ΔC H2 (MW 120 kDa) with ⁶⁴Cu showed high tracer retention in the kidneys,(>38% injected dose per gram (ID/g) 48 h post-injection), presumably because the high local positive charge on the Cu II-SarAr moiety resulted in increased binding of the labeled protein to the negatively charged basalmore » cells of the glomerulus. To test this hypothesis, ch14.18-ΔC H2 was conjugated with a series of Sar derivatives of decreasing positive charge and three commonly used macrocyclic polyaza polycarboxylate (PAC) BFCs. The immunoconjugates were labeled with ⁶⁴Cu and injected into mice, and PET/CT images were obtained at 24 and 48 h post injection (p.i.). At 48 h p.i., ex vivo biodistribution was carried out. In addition, to demonstrate the potential of metastasis detection using ⁶⁴Cu-labeled ch14.18-ΔC H2, a preclinical imaging study of intrahepatic neuroblastoma tumors was performed carried out. Reducing the positive charge on the Sar chelators decreased kidney uptake of Cu-labeled ch14.18-ΔC H2 by more than 6-fold, from >45 ID/g to <6% ID/g, while the uptake in most other tissues, including liver, was relatively unchanged. However, despite this dramatic decrease, the renal uptake of the PAC BFCs was generally lower than that of the Sar derivatives, as was the liver uptake. Uptake of ⁶⁴Cu-labeled ch14.18-ΔC H2 in neuroblastoma hepatic metastases was detected using PET.« less

Integration of High-Charge-Injection-Capacity Electrodes onto Polymer Softening Neural Interfaces.

PubMed

Arreaga-Salas, David E; Avendaño-Bolívar, Adrian; Simon, Dustin; Reit, Radu; Garcia-Sandoval, Aldo; Rennaker, Robert L; Voit, Walter

2015-12-09

Softening neural interfaces are implanted stiff to enable precise insertion, and they soften in physiological conditions to minimize modulus mismatch with tissue. In this work, a high-charge-injection-capacity iridium electrode fabrication process is detailed. For the first time, this process enables integration of iridium electrodes onto softening substrates using photolithography to define all features in the device. Importantly, no electroplated layers are utilized, leading to a highly scalable method for consistent device fabrication. The iridium electrode is metallically bonded to the gold conductor layer, which is covalently bonded to the softening substrate via sulfur-based click chemistry. The resulting shape-memory polymer neural interfaces can deliver more than 2 billion symmetric biphasic pulses (100 μs/phase), with a charge of 200 μC/cm(2) and geometric surface area (GSA) of 300 μm(2). A transfer-by-polymerization method is used in combination with standard semiconductor processing techniques to fabricate functional neural probes onto a thiol-ene-based, thin film substrate. Electrical stability is tested under simulated physiological conditions in an accelerated electrical aging paradigm with periodic measurement of electrochemical impedance spectra (EIS) and charge storage capacity (CSC) at various intervals. Electrochemical characterization and both optical and scanning electron microscopy suggest significant breakdown of the 600 nm-thick parylene-C insulation, although no delamination of the conductors or of the final electrode interface was observed. Minor cracking at the edges of the thin film iridium electrodes was occasionally observed. The resulting devices will provide electrical recording and stimulation of the nervous system to better understand neural wiring and timing, to target treatments for debilitating diseases, and to give neuroscientists spatially selective and specific tools to interact with the body. This approach has uses for cochlear implants, nerve cuff electrodes, penetrating cortical probes, spinal stimulators, blanket electrodes for the gut, stomach, and visceral organs and a host of other custom nerve-interfacing devices.

Numerical investigation of the effect of net charge injection on the electric field deviation in a TE CO2 laser

NASA Astrophysics Data System (ADS)

Jahanianl, Nahid; Aram, Majid; Morshedian, Nader; Mehramiz, Ahmad

2018-03-01

In this report, the distribution of and deviation in the electric field were investigated in the active medium of a TE CO2 laser. The variation in the electric field is due to injection of net electron and proton charges as a plasma generator. The charged-particles beam density is assumed to be Gaussian. The electric potential and electric field distribution were simulated by solving Poisson’s equation using the SOR numerical method. The minimum deviation of the electric field obtained was about 2.2% and 6% for the electrons and protons beams, respectively, for a charged-particles beam-density of 106 cm-3. This result was obtained for a system geometry ensuring a mean-free-path of the particles beam of 15 mm. It was also found that the field deviation increases for a the mean-free-path smaller than that or larger than 25 mm. Moreover, the electric field deviation decreases when the electrons beam density exceeds 106 cm-3.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Abanin, D. A.; Department of Physics, Princeton University, Princeton, New Jersey 08544; Kavli Institute for Theoretical Physics, University of California, Santa Barbara, California 93106

Quantum Hall states that result from interaction induced lifting of the eightfold degeneracy of the zeroth Landau level in bilayer graphene are considered. We show that at even filling factors electric charge is injected into the system in the form of charge 2e Skyrmions. This is a rare example of binding of charges in a system with purely repulsive interactions. We calculate the Skyrmion energy and size as a function of the effective Zeeman interaction and discuss the signatures of the charge 2e Skyrmions in the scanning probe experiments.

Gain measurements of the Ca-Xe charge exchange system. [for UV lasers

NASA Technical Reports Server (NTRS)

Michels, C. J.; Chubb, D. L.

1978-01-01

Charge-exchange-pumped Ca(+) was studied for possible positive laser gain at 370.6 and 315.9 nm using an Xe MPD arc as the Xe(+) source. The present paper describes the MPD arc, the calcium injection system, the diagnostics for gain, and spontaneous emission measurements and results. No positive gain measurements were observed. A small Xe-Ca charge exchange cross section compared to He-metal laser systems charge exchange cross sections is the most probable reason why the result was negative.

Injection and detection of a spin-polarized current in a light-emitting diode

NASA Astrophysics Data System (ADS)

Fiederling, R.; Keim, M.; Reuscher, G.; Ossau, W.; Schmidt, G.; Waag, A.; Molenkamp, L. W.

1999-12-01

The field of magnetoelectronics has been growing in practical importance in recent years. For example, devices that harness electronic spin-such as giant-magnetoresistive sensors and magnetoresistive memory cells-are now appearing on the market. In contrast, magnetoelectronic devices based on spin-polarized transport in semiconductors are at a much earlier stage of development, largely because of the lack of an efficient means of injecting spin-polarized charge. Much work has focused on the use of ferromagnetic metallic contacts, but it has proved exceedingly difficult to demonstrate polarized spin injection. More recently, two groups have reported successful spin injection from an NiFe contact, but the observed effects of the spin-polarized transport were quite small (resistance changes of less than 1%). Here we describe a different approach, in which the magnetic semiconductor BexMnyZn1-x-ySe is used as a spin aligner. We achieve injection efficiencies of 90% spin-polarized current into a non-magnetic semiconductor device. The device used in this case is a GaAs/AlGaAs light-emitting diode, and spin polarization is confirmed by the circular polarization state of the emitted light.

Tuning ultrafast electron injection dynamics at organic-graphene/metal interfaces.

PubMed

Ravikumar, Abhilash; Kladnik, Gregor; Müller, Moritz; Cossaro, Albano; Bavdek, Gregor; Patera, Laerte L; Sánchez-Portal, Daniel; Venkataraman, Latha; Morgante, Alberto; Brivio, Gian Paolo; Cvetko, Dean; Fratesi, Guido

2018-05-03

We compare the ultrafast charge transfer dynamics of molecules on epitaxial graphene and bilayer graphene grown on Ni(111) interfaces through first principles calculations and X-ray resonant photoemission spectroscopy. We use 4,4'-bipyridine as a prototypical molecule for these explorations as the energy level alignment of core-excited molecular orbitals allows ultrafast injection of electrons from a substrate to a molecule on a femtosecond timescale. We show that the ultrafast injection of electrons from the substrate to the molecule is ∼4 times slower on weakly coupled bilayer graphene than on epitaxial graphene. Through our experiments and calculations, we can attribute this to a difference in the density of states close to the Fermi level between graphene and bilayer graphene. We therefore show how graphene coupling with the substrate influences charge transfer dynamics between organic molecules and graphene interfaces.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, H. D.; Fiorito, R. B.; Corbett, J.

The 3GeV SPEAR3 synchrotron light source operates in top-up injection mode with up to 500 mA circulating in the storage ring (equivalently 392 nC). Each injection pulse contains 40–80 pC producing a contrast ratio between total stored charge and injected charge of about 6500:1. In order to study transient injected beam dynamics during user operations, it is desirable to optically image the injected pulse in the presence of the bright stored beam. In the present work this is done by imaging the visible component of the synchrotron radiation onto a digital micro-mirror-array device (DMD), which is then used as anmore » optical mask to block out light from the bright central core of the stored beam. The physical masking, together with an asynchronously-gated, ICCD imaging camera, makes it possible to observe the weak injected beam component on a turn-by-turn basis. The DMD optical masking system works similar to a classical solar coronagraph but has some distinct practical advantages: i.e. rapid adaption to changes in the shape of the stored beam, a high extinction ratio for unwanted light and minimum scattering from the primary beam into the secondary optics. In this paper we describe the DMD masking method, features of the high dynamic range point spread function for the SPEAR3 optical beam line and measurements of the injected beam in the presence of the stored beam.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Hao; Fiorito, Ralph; Corbett, Jeff

The 3GeV SPEAR3 synchrotron light source operates in top-up injection mode with up to 500mA circulating in the storage ring (equivalently 392nC). Each injection pulse contains only 40-80 pC producing a contrast ratio between total stored charge and injected charge of about 6500:1. In order to study transient injected beam dynamics during User operations, it is desirable to optically image the injected pulse in the presence of the bright stored beam. In the present work this is done by re-imaging visible synchrotron radiation onto a digital micro-mirror-array device (DMD), which is then used as an optical mask to block outmore » light from the bright central core of the stored beam. The physical masking, together with an asynchronously-gated, ICCD imaging camera makes it is possible to observe the weak injected beam component on a turn-by-turn basis. The DMD optical masking system works similar to a classical solar coronagraph but has some distinct practical advantages: i.e. rapid adaption to changes in the shape of the stored beam, high extinction ratio for unwanted light and minimum scattering from the primary beam into the secondary optics. In this paper we describe the DMD masking method, features of the high dynamic range point spread function for the SPEAR3 optical beam line and measurements of the injected beam in the presence of the stored beam.« less

An improved model to estimate trapping parameters in polymeric materials and its application on normal and aged low-density polyethylenes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, Ning, E-mail: nl4g12@soton.ac.uk; He, Miao; Alghamdi, Hisham

2015-08-14

Trapping parameters can be considered as one of the important attributes to describe polymeric materials. In the present paper, a more accurate charge dynamics model has been developed, which takes account of charge dynamics in both volts-on and off stage into simulation. By fitting with measured charge data with the highest R-square value, trapping parameters together with injection barrier of both normal and aged low-density polyethylene samples were estimated using the improved model. The results show that, after long-term ageing process, the injection barriers of both electrons and holes is lowered, overall trap depth is shallower, and trap density becomesmore » much greater. Additionally, the changes in parameters for electrons are more sensitive than those of holes after ageing.« less

The CarbFix Pilot Project in Iceland - CO2 capture and mineral storage in basaltic rocks

NASA Astrophysics Data System (ADS)

Sigurdardottir, H.; Sigfusson, B.; Aradottir, E. S.; Gunnlaugsson, E.; Gislason, S. R.; Alfredsson, H. A.; Broecker, W. S.; Matter, J. M.; Stute, M.; Oelkers, E.

2010-12-01

The overall objective of the CarbFix project is to develop and optimize a practical and cost-effective technology for capturing CO2 and storing it via in situ mineral carbonation in basaltic rocks, as well as to train young scientist to carry the corresponding knowledge into the future. The project consists of a field injection of CO2 charged water at the Hellisheidi geothermal power plant in SW Iceland, laboratory experiments, numerical reactive transport modeling, tracer tests, natural analogue and cost analysis. The CO2 injection site is situated about 3 km south of the Hellisheidi geothermal power plant. Reykjavik Energy operates the power plant, which currently produces 60,000 tons/year CO2 of magmatic origin. The produced geothermal gas mainly consists of CO2 and H2S. The two gases will be separated in a pilot gas treatment plant, and CO2 will be transported in a pipeline to the injection site. There, CO2 will be fully dissolved in 20 - 25°C water during injection at 25 - 30 bar pressure, resulting in a single fluid phase entering the storage formation, which consists of relatively fresh basaltic lavas. The CO2 charged water is reactive and will dissolve divalent cations from the rock, which will combine with the dissolved carbon to form solid thermodynamically stable carbonate minerals. The injection test is designed to inject 2200 tons of CO2 per year. In the past three years the CarbFix project has been addressing background fluid chemistries at the injection site and characterizing the target reservoir for the planned CO2 injection. Numerous groundwater samples have been collected and analysed. A monitoring and accounting plan has been developed, which integrates surface, subsurface and atmospheric monitoring. A weather station is operating at the injection site for continuous monitoring of atmospheric CO2 and to track all key parameters for the injection. Environmental authorities have granted licenses for the CO2 injection and the use of tracers, based on the monitoring plan. Pipelines, injection and monitoring wells have been installed and equipment test runs are in the final phase. A bailer has been constructed to be used to retrieve samples at reservoir conditions. Hydrological parameters of a three dimensional field model have been calibrated and reactive transport simulations are ongoing. The key risks that the project is currently facing are technical and financial. Until now the project has been facing incidences that have already impacted the time schedule in the CarbFix project. Furthermore the project is facing world-wide exchange rate uncertainty plus the inherited uncertainty that innovative research projects contain. However, the CarbFix group remains optimistic that injection will start in near future.

40 CFR 63.365 - Test methods and procedures.

Code of Federal Regulations, 2011 CFR

2011-07-01

... for Volatile Alcohols in Water By Direct Aqueous-Injection Gas Chromatography, (incorporated by... be determined by either: (A) Weighing the ethylene oxide gas cylinder(s) used to charge the... mass of gas charged by the weight percent ethylene oxide present in the gas. (B) Installing calibrated...

Modulated charge injection in p-type dye-sensitized solar cells using fluorene-based light absorbers.

PubMed

Liu, Zonghao; Xiong, Dehua; Xu, Xiaobao; Arooj, Qudsia; Wang, Huan; Yin, Liyuan; Li, Wenhui; Wu, Huaizhi; Zhao, Zhixin; Chen, Wei; Wang, Mingkui; Wang, Feng; Cheng, Yi-Bing; He, Hongshan

2014-03-12

In this study, new pull-push arylamine-fluorene based organic dyes zzx-op1, zzx-op2, and zzx-op3 have been designed and synthesized for p-type dye-sensitized solar cells (p-DSCs). In zzx-op1, a di(p-carboxyphenyl)amine (DCPA) was used as an electron donor, a perylenemonoimide (PMID) as an electron acceptor, and a fluorene (FLU) unit with two aliphatic hexyl chains as a π-conjugated linker. In zzx-op2 and zzx-op3, a 3,4-ethylenedioxythiophene (EDOT) and a thiophene were inserted consecutively between PMID and FLU to tune the energy levels of the frontier molecular orbitals of the dyes. The structural modification broadened the spectral coverage from an onset of 700 nm for zzx-op1 to 750 nm for zzx-op3. The electron-rich EDOT and thiophene lifted up the HOMO (highest occupied molecular orbital) levels of zzx-op2 and zzx-op3, making their potential more negative than zzx-op1. When three dyes were employed in p-type DSCs with I(-)/I3(-) as a redox couple and NiO nanoparticles as hole materials, zzx-op1 exhibited impressive energy conversion efficiency of 0.184% with the open-circuit voltage (VOC) of 112 mV and the short-circuit current density (JSC) of 4.36 mA cm(-2) under AM 1.5G condition. Density functional theory calculations, transient photovoltage decay measurements, and electrochemical impedance spectroscopic studies revealed that zzx-op1 sensitized solar cell exhibited much higher charge injection efficiency (90.3%) than zzx-op2 (53.9%) and zzx-op3 (39.0%), indicating a trade-off between spectral broadening and electron injection driving force in p-type DSCs.

Monitoring Ultrafast Chemical Dynamics by Time-Domain X-ray Photo- and Auger-Electron Spectroscopy.

PubMed

Gessner, Oliver; Gühr, Markus

2016-01-19

The directed flow of charge and energy is at the heart of all chemical processes. Extraordinary efforts are underway to monitor and understand the concerted motion of electrons and nuclei with ever increasing spatial and temporal sensitivity. The element specificity, chemical sensitivity, and temporal resolution of ultrafast X-ray spectroscopy techniques hold great promise to provide new insight into the fundamental interactions underlying chemical dynamics in systems ranging from isolated molecules to application-like devices. Here, we focus on the potential of ultrafast X-ray spectroscopy techniques based on the detection of photo- and Auger electrons to provide new fundamental insight into photochemical processes of systems with various degrees of complexity. Isolated nucleobases provide an excellent testing ground for our most fundamental understanding of intramolecular coupling between electrons and nuclei beyond the traditionally applied Born-Oppenheimer approximation. Ultrafast electronic relaxation dynamics enabled by the breakdown of this approximation is the major component of the nucleobase photoprotection mechanisms. Transient X-ray induced Auger electron spectroscopy on photoexcited thymine molecules provides atomic-site specific details of the extremely efficient coupling that converts potentially bond changing ultraviolet photon energy into benign heat. In particular, the time-dependent spectral shift of a specific Auger band is sensitive to the length of a single bond within the molecule. The X-ray induced Auger transients show evidence for an electronic transition out of the initially excited state within only ∼200 fs in contrast to theoretically predicted picosecond population trapping behind a reaction barrier. Photoinduced charge transfer dynamics between transition metal complexes and semiconductor nanostructures are of central importance for many emerging energy and climate relevant technologies. Numerous demonstrations of photovoltaic and photocatalytic activity have been performed based on the combination of strong light absorption in dye molecules with charge separation and transport in adjacent semiconductor nanostructures. However, a fundamental understanding of the enabling and limiting dynamics on critical atomic length- and time scales is often still lacking. Femtosecond time-resolved X-ray photoelectron spectroscopy is employed to gain a better understanding of a short-lived intermediate that may be linked to the unexpectedly limited performance of ZnO based dye-sensitized solar cells by delaying the generation of free charge carriers. The transient spectra strongly suggest that photoexcited dye molecules attached to ZnO nanocrystals inject their charges into the substrate within less than 1 ps but the electrons are then temporarily trapped at the surface of the semiconductor in direct vicinity of the injecting molecules. The experiments are extended to monitor the electronic response of the semiconductor substrate to the collective injection from a monolayer of dye molecules and the subsequent electron-ion recombination dynamics. The results indicate some qualitative similarities but quantitative differences between the recombination dynamics at molecule-semiconductor interfaces and previously studied bulk-surface electron-hole recombination dynamics in photoexcited semiconductors.

Oxide materials for spintronic device applications

NASA Astrophysics Data System (ADS)

Prestgard, Megan Campbell

Spintronic devices are currently being researched as next-generation alternatives to traditional electronics. Electronics, which utilize the charge-carrying capabilities of electrons to store information, are fundamentally limited not only by size constraints, but also by limits on current flow and degradation, due to electro-migration. Spintronics devices are able to overcome these limitations, as their information storage is in the spin of electrons, rather than their charge. By using spin rather than charge, these current-limiting shortcomings can be easily overcome. However, for spintronic devices to be fully implemented into the current technology industry, their capabilities must be improved. Spintronic device operation relies on the movement and manipulation of spin-polarized electrons, in which there are three main processes that must be optimized in order to maximize device efficiencies. These spin-related processes are: the injection of spin-polarized electrons, the transport and manipulation of these carriers, and the detection of spin-polarized currents. In order to enhance the rate of spin-polarized injection, research has been focused on the use of alternative methods to enhance injection beyond that of a simple ferromagnetic metal/semiconductor injector interface. These alternatives include the use of oxide-based tunnel barriers and the modification of semiconductors and insulators for their use as ferromagnetic injector materials. The transport of spin-polarized carriers is heavily reliant on the optimization of materials' properties in order to enhance the carrier mobility and to quench spin-orbit coupling (SOC). However, a certain degree of SOC is necessary in order to allow for the electric-field, gate-controlled manipulation of spin currents. Spin detection can be performed via both optical and electrical techniques. Using electrical methods relies on the conversion between spin and charge currents via SOC and is often the preferred method for device-based applications. This dissertation presents experimental results on the use of oxides for fulfilling the three spintronic device requirements. In the case of spin injection, the study of dilute magnetic dielectrics (DMDs) shows the importance of doping on the magnetic properties of the resulting tunnel barriers. The study of spin transport in ZnO has shown that, even at room temperature, the spin diffusion length is relatively long, on the order of 100 nm. These studies have also probed the spin relaxation mechanics in ZnO and have shown that Dyakonov-Perel spin relaxation, operating according to Fermi-Dirac statistics, is the dominant spin relaxation mechanism in zinc oxide. Finally, spin detection in ZnO has shown that, similar to other semiconductors, by modifying the resistivity of the ZnO thin films, the spin Hall angle (SHA) can be enhanced to nearly that of metals. This is possible by enhancing extrinsic SOC due to skew-scattering from impurities as well as phonons. In addition, thermal spin injection has also been detected using ZnO, which results support the independently measured inverse spin-Hall effect studies. The work represented herein illustrates that oxide materials have the potential to enhance spintronic device potential in all processes pertinent to spintronic applications.

AUTOMOTIVE DIESEL MAINTENANCE 1. UNIT XXIV, I--MAINTAINING THE FUEL SYSTEM PART III--CATERPILLAR DIESEL ENGINE, II--UNDERSTANDING THE VOLTAGE REGULATOR/ALTERNATOR.

ERIC Educational Resources Information Center

Minnesota State Dept. of Education, St. Paul. Div. of Vocational and Technical Education.

THIS MODULE OF A 30-MODULE COURSE IS DESIGNED TO DEVELOP AN UNDERSTANDING OF THE OPERATION AND MAINTENANCE OF THE DIESEL ENGINE FUEL AND BATTERY CHARGING SYSTEM. TOPICS ARE (1) INJECTION TIMING CONTROLS, (2) GOVERNOR, (3) FUEL SYSTEM MAINTENANCE TIPS, (4) THE CHARGING SYSTEM, (5) REGULATING THE GENERATOR/ALTERNATOR, AND (6) CHARGING SYSTEM SERVICE…

Detection of charge storage on molecular thin films of tris(8-hydroxyquinoline) aluminum (Alq3) by Kelvin force microscopy: a candidate system for high storage capacity memory cells.

PubMed

Paydavosi, Sarah; Aidala, Katherine E; Brown, Patrick R; Hashemi, Pouya; Supran, Geoffrey J; Osedach, Timothy P; Hoyt, Judy L; Bulović, Vladimir

2012-03-14

Retention and diffusion of charge in tris(8-hydroxyquinoline) aluminum (Alq(3)) molecular thin films are investigated by injecting electrons and holes via a biased conductive atomic force microscopy tip into the Alq(3) films. After the charge injection, Kelvin force microscopy measurements reveal minimal changes with time in the spatial extent of the trapped charge domains within Alq(3) films, even for high hole and electron densities of >10(12) cm(-2). We show that this finding is consistent with the very low mobility of charge carriers in Alq(3) thin films (<10(-7) cm(2)/(Vs)) and that it can benefit from the use of Alq(3) films as nanosegmented floating gates in flash memory cells. Memory capacitors using Alq(3) molecules as the floating gate are fabricated and measured, showing durability over more than 10(4) program/erase cycles and the hysteresis window of up to 7.8 V, corresponding to stored charge densities as high as 5.4 × 10(13) cm(-2). These results demonstrate the potential for use of molecular films in high storage capacity nonvolatile memory cells. © 2012 American Chemical Society

Charge carrier transport and injection across organic heterojunctions

NASA Astrophysics Data System (ADS)

Tsang, Sai Wing

The discovery of highly efficient organic light-emitting diodes (OLEDs) in the 1980s has stimulated extensive research on organic semiconductors and devices. Underlying this breakthrough is the realization of the organic heterojunction (OH). Besides OLEDs, the implementation of the OH also significantly improves the power conversion efficiency in organic photovoltaic cells (OPVs). The continued technological advancements in organic electronic devices depend on the accumulation of knowledge of the intrinsic properties of organic materials and related interfaces. Among them, charge-carrier transport and carrier injection are two key factors that govern the performance of a device. This thesis mainly focuses on the charge carrier injection and transport at organic heterojunctions. The carrier transport properties of different organic materials used in this study are characterized by time-of-flight (TOF) and admittance spectroscopy (AS). An injection model is formulated by considering the carrier distribution at both sides of the interface. Using a steady-state simulation approach, the effect of accumulated charges on energy level alignment at OH is revealed. Instead of a constant injection barrier, it is found that the barrier varies with applied voltage. Moreover, an escape probability function in the injection model is modified by taking into account the total hopping rate and available hopping sites at the interface. The model predicts that the injection current at low temperature can be dramatically modified by an extremely small density of deep trap states. More importantly, the temperature dependence of the injection current is found to decrease with increasing barrier height. This suggests that extracting the barrier height from the J vs 1/T plot, as commonly employed in the literature, is problematic. These theoretical predictions are confirmed by a series of experiments on heterojunction devices with various barrier heights. In addition, the presence of deep trap states is also consistent with carrier mobility measurements at low temperature. From the point of view of application, an interface chemical doping method is proposed to engineer the carrier injection at an organic heterojunction. It is found that the injection current can be effectively increased or suppressed by introducing a thin (2 nm) doped organic layer at the interface. This technique is further extended to study the impact of an injection barrier at the OH, in OLEDs, on device performance. It is shown that a 0.3 eV injection barrier at the OH, that is normally negligible at metal/organic interface, can reduce the device efficiency by 25%. This is explained by the carrier distribution in the density-of-states at the OH. Furthermore, the carrier transport properties in a bulk heterojunction system are investigated. The bulk heterojunction consists of an interpenetrating network of a polymeric electron donor and a molecular electron acceptor. This material system has been studied in the last few years as an attractive power conversion efficiency (5% under AM 1.5) of OPV cells has been demonstrated. It is found that the electron mobility is greatly dependent on the thermal treatment of the film. Interfacial dipole effect at the heterojunction between the donor and the acceptor is proposed to be the determining factor that alters the carrier mobility in different nanoscale structures.

Correlational Effects of the Molecular-Tilt Configuration and the Intermolecular van der Waals Interaction on the Charge Transport in the Molecular Junction.

PubMed

Shin, Jaeho; Gu, Kyungyeol; Yang, Seunghoon; Lee, Chul-Ho; Lee, Takhee; Jang, Yun Hee; Wang, Gunuk

2018-06-25

Molecular conformation, intermolecular interaction, and electrode-molecule contacts greatly affect charge transport in molecular junctions and interfacial properties of organic devices by controlling the molecular orbital alignment. Here, we statistically investigated the charge transport in molecular junctions containing self-assembled oligophenylene molecules sandwiched between an Au probe tip and graphene according to various tip-loading forces ( F L ) that can control the molecular-tilt configuration and the van der Waals (vdW) interactions. In particular, the molecular junctions exhibited two distinct transport regimes according to the F L dependence (i.e., F L -dependent and F L -independent tunneling regimes). In addition, the charge-injection tunneling barriers at the junction interfaces are differently changed when the F L ≤ 20 nN. These features are associated to the correlation effects between the asymmetry-coupling factor (η), the molecular-tilt angle (θ), and the repulsive intermolecular vdW force ( F vdW ) on the molecular-tunneling barriers. A more-comprehensive understanding of these charge transport properties was thoroughly developed based on the density functional theory calculations in consideration of the molecular-tilt configuration and the repulsive vdW force between molecules.

The electro-mechanical effect from charge dynamics on polymeric insulation lifetime

DOE Office of Scientific and Technical Information (OSTI.GOV)

Alghamdi, H., E-mail: haalghamdi@nu.edu.sa; Faculty of Engineering, Najran University, Najran, P.O.Box 1988; Chen, G.

For polymeric material used as electrical insulation, the presence of space charges could be the consequence of material degradations that are thermally activated but increased by the application of an electric field. The dynamics of space charge, therefore, can be potentially used to characterize the material. In this direction, a new aging model in which parameters have clear physical meanings has been developed and applied to the material to extrapolate the lifetime. The kinetic equation has been established based on charge trapping and detrapping of the injected charge from the electrodes. The local electromechanical energy stored in the region surroundingmore » the trap is able to reduce the trap-depth with a value related to the electric field. At a level where the internal electric field exceeds the detrapping field in the material, an electron can be efficiently detrapped and the released energy from detrapping process can cause a weak bond or chain scission i.e. material degradation. The model has been applied to the electro-thermally aged low density polyethylene film samples, showing well fitted result, as well as interesting relationships between parameter estimates and insulation morphology.« less

The study of surface acoustic wave charge transfer device

NASA Technical Reports Server (NTRS)

Papanicolaou, N.; Lin, H. C.

1978-01-01

A surface acoustic wave-charge transfer device, consisting of an n-type silicon substrate, a thermally grown silicon dioxide layer, and a sputtered film of piezoelectric zinc oxide is proposed as a means of circumventing problems associated with charge-coupled device (CCD) applications in memory, signal processing, and imaging. The proposed device creates traveling longitudinal electric fields in the silicon and replaces the multiphase clocks in CCD's. The traveling electric fields create potential wells which carry along charges stored there. These charges may be injected into the wells by light or by using a p-n junction as in conventional CCD's.

An experimental study of basaltic glass-H2O-CO2 interaction at 22 and 50 °C: Implications for subsurface storage of CO2

NASA Astrophysics Data System (ADS)

Galeczka, Iwona; Wolff-Boenisch, Domenik; Oelkers, Eric H.; Gislason, Sigurdur R.

2014-02-01

A novel high pressure column flow reactor was used to investigate the evolution of solute chemistry along a 2.3 m flow path during pure water- and CO2-charged water-basaltic glass interaction experiments at 22 and 50 °C and 10-5.7 to 22 bars partial pressure of CO2. Experimental results and geochemical modelling showed the pH of injected pure water evolved rapidly from 6.7 to 9-9.5 and most of the iron released to the fluid phase was subsequently consumed by secondary minerals, similar to natural meteoric water-basalt systems. In contrast to natural systems, however, the aqueous aluminium concentration remained relatively high along the entire flow path. The aqueous fluid was undersaturated with respect to basaltic glass and carbonate minerals, but supersaturated with respect to zeolites, clays, and Fe hydroxides. As CO2-charged water replaced the alkaline fluid within the column, the fluid briefly became supersaturated with respect to siderite. Basaltic glass dissolution in the column reactor, however, was insufficient to overcome the pH buffer capacity of CO2-charged water. The pH of this CO2-charged water rose from an initial 3.4 to only 4.5 in the column reactor. This acidic reactive fluid was undersaturated with respect to carbonate minerals but supersaturated with respect to clays and Fe hydroxides at 22 °C, and with respect to clays and Al hydroxides at 50 °C. Basaltic glass dissolution in the CO2-charged water was closer to stoichiometry than in pure water. The mobility and aqueous concentration of several metals increased significantly with the addition of CO2 to the inlet fluid, and some metals, including Mn, Cr, Al, and As exceeded the allowable drinking water limits. Iron became mobile and the aqueous Fe2+/Fe3+ ratio increased along the flow path. Although carbonate minerals did not precipitate in the column reactor in response to CO2-charged water-basaltic glass interaction, once this fluid exited the reactor, carbonates precipitated as the fluid degassed at the outlet. Substantial differences were found between the results of geochemical modelling calculations and the observed chemical evolution of the fluids during the experiments. These differences underscore the need to improve the models before they can be used to predict with confidence the fate and consequences of carbon dioxide injected into the subsurface. The pH increase from 3.4 to 4.5 of the CO2-rich inlet fluid does not immobilize toxic elements at ambient temperature but immobilizes Al and Cr at 50 °C. This indicates that further neutralization of CO2-charged water is required for decreased toxic element mobility. The CO2-charged water injection enhances the mobility of redox sensitive Fe2+ significantly making it available for the storage of injected carbon as iron carbonate minerals. The precipitation of aluminosilicates likely occurred at a pH of 4.2-4.5 in CO2-charged waters. These secondary phases can (1) fill the available pore space and therefore clog the host rock in the vicinity of the injection well, and (2) incorporate some divalent cations limiting their availability for carbon storage. The inability of simple reactive transport models to describe accurately the fluid evolution in this well constrained one dimensional flow system suggests that significant improvements need to be made to such models before we can predict with confidence the fate and consequences of injecting carbon dioxide into the subsurface. Column reactors such as that used in this study could be used to facilitate ex situ carbon mineral storage. Carbonate precipitation at the outlet of the reactor suggests that the harvesting of divalent metals from rocks using CO2-charged waters could potentially be upscaled to an industrial carbonation process.

Risky driving and sexual behaviors as developmental outcomes of co-occurring substance use and antisocial behavior.

PubMed

Luk, Jeremy W; Worley, Matthew J; Winiger, Evan; Trim, Ryan S; Hopfer, Christian J; Hewitt, John K; Brown, Sandra A; Wall, Tamara L

2016-12-01

To examine the associations between substance use and antisocial behavior trajectories and seven risky behaviors over time. Data were collected from a high-risk sample of adolescents followed into young adulthood. Five trajectory classes, identified based on dual development of substance use and antisocial behavior symptoms, were used to predict three risky driving and four risky sexual behaviors. In this high-risk sample (n=530), participants reported notably high overall rates of reckless driving (55.5%) and unprotected sex under the influence (44.8%) in the past year. Risky behaviors that are typically of low base rates in population-based studies were also elevated, with 8.8% reporting past-year driving under the influence (DUI) charge, 17.6% reporting lifetime sexually transmitted infection (STI), and 10.4% reporting lifetime injection drug use. The Dual Chronic class had the highest levels of all seven risky behaviors, and were 3-4 times more likely to report risky driving, lifetime STI, and injection drug use than the Relatively Resolved class. Rates of past-year reckless driving and DUI were elevated among classes with persistent antisocial behavior, whereas rates of DUI, DUI charge, and unprotected sex under the influence were elevated among classes with persistent substance use. Young adults with persistent co-occurring substance use and antisocial behavior engage in multiple very costly risky behaviors. Differential associations between risky behaviors and trajectory classes highlight the need for targeted interventions. Published by Elsevier Ireland Ltd.

“Vivo para consumirla y la consumo para vivir” [“I live to inject and inject to live”]: High-Risk Injection Behaviors in Tijuana, Mexico

PubMed Central

Strathdee, Steffanie A.; Fraga, Wendy Davila; Case, Patricia; Firestone, Michelle; Brouwer, Kimberly C.; Perez, Saida Gracia; Magis, Carlos; Fraga, Miguel Angel

2007-01-01

Injection drug use is a growing problem on the US–Mexico border, where Tijuana is situated. We studied the context of injection drug use among injection drug users (IDUs) in Tijuana to help guide future research and interventions. Guided in-depth interviews were conducted with 10 male and 10 female current IDUs in Tijuana. Topics included types of drug used, injection settings, access to sterile needles, and environmental influences. Interviews were taped, transcribed verbatim, and translated. Content analysis was conducted to identify themes. Of the 20 IDUs, median age and age at first injection were 30 and 18. Most reported injecting at least daily: heroin (“carga,” “chiva,” “negra”), methamphetamine (“crico,” “cri-cri”), or both drugs combined. In sharp contrast to Western US cities, almost all regularly attended shooting galleries (“yongos” or “picaderos”) because of the difficulties obtaining syringes and police oppression. Almost all shared needles/paraphernalia [“cuete” (syringe), “cacharros” (cookers), cotton from sweaters/socks (filters)]. Some reported obtaining syringes from the United States. Key themes included (1) pharmacies refusing to sell or charging higher prices to IDUs, (2) ample availability of used/rented syringes from “picaderos” (e.g., charging approximately 5 pesos or “10 drops” of drug), and (3) poor HIV/AIDS knowledge, such as beliefs that exposing syringes to air “kills germs.” This qualitative study suggests that IDUs in Tijuana are at high risk of HIV and other blood-borne infections. Interventions are urgently needed to expand access to sterile injection equipment and offset the potential for a widespread HIV epidemic. PMID:16107441

Nanoparticle diffusion in, and microrheology of, the bovine vitreous ex vivo

PubMed Central

Xu, Qingguo; Boylan, Nicholas J.; Suk, Jung Soo; Wang, Ying-Ying; Nance, Elizabeth; Yang, Jeh-Chang; McDonnell, Peter; Cone, Richard; Duh, Elia J.; Hanes, Justin

2013-01-01

Intravitreal injection of biodegradable nanoparticles (NP) holds promise for gene therapy and drug delivery to the back of the eye. In some cases, including gene therapy, NP need to diffuse rapidly from the site of injection in order to reach targeted cell types in the back of the eye, whereas in other cases it may be preferred for the particles to remain at the injection site and slowly release drugs that may then diffuse to the site of action. We studied the movements of polystyrene (PS) nanoparticles of various sizes and surface chemistries in fresh bovine vitreous. PS NP as large as 510 nm rapidly penetrated the vitreous gel when coated with polyethylene glycol (PEG), whereas the movements of NP 1190 nm in diameter or larger were highly restricted regardless of surface chemistry owing to steric obstruction. PS NP coated with primary amine groups (–NH2) possessed positively charged surfaces at the pH of bovine vitreous (pH = 7.2), and were immobilized within the vitreous gel. In comparison, PS NP coated with –COOH (possessing negatively charged surfaces) in the size range of 100–200 nm and at particle concentrations below 0.0025% (w/v) readily diffused through the vitreous meshwork; at higher concentrations (~0.1% w/v), these nanoparticles aggregated within vitreous. Based on the mobility of different sized PS-PEG NP, we estimated the average mesh size of fresh bovine vitreous to be ~550 ± 50 nm. The bovine vitreous behaved as an impermeable elastic barrier to objects sized 1190 nm and larger, but as a highly permeable viscoelastic liquid to non-adhesive objects smaller than 510 nm in diameter. Guided by these studies, we next sought to examine the transport of drug- and DNA-loaded nanoparticles in bovine vitreous. Biodegradable NP with diameter of 227 nm, composed of a poly(lactic-co-glycolic acid) (PLGA)-based core coated with poly(vinyl alcohol) rapidly penetrated vitreous. Rod-shaped, highly-compacted CK30PEG10k/DNA with PEG coating (neutral surface charge; diameter ~60 nm) diffused rapidly within vitreous. These findings will help guide the development of nanoparticle-based therapeutics for the treatment of vision-threatening ocular diseases. PMID:23369761

Ignition delays, heats of combustion, and reaction rates of aluminum alkyl derivatives used as ignition and combustion enhancers for supersonic combustors

NASA Technical Reports Server (NTRS)

Ryan, T. W., III; Harlowe, W. W.; Schwab, S.

1992-01-01

The work was based on adapting an apparatus and procedure developed at Southwest Research Institute for rating the ignition quality of fuels for diesel engines. Aluminum alkyls and various Lewis-base adducts of these materials, both neat and mixed 50/50 with pure JP-10 hydrocarbon, were injected into the combustion bomb using a high-pressure injection system. The bomb was pre-charged with air that was set at various initial temperatures and pressures for constant oxygen density. The ignition delay times were determined for the test materials at these different initial conditions. The data are presented in absolute terms as well as comparisons with the parent alkyls. The relative heats of reaction of the various test materials were estimated based on a computation of the heat release, using the pressure data recorded during combustion in the bomb. In addition, the global reaction rates for each material were compared at a selected tmperature and pressure.

Feasibility of an advanced thrust termination assembly for a solid propellant rocket motor

NASA Technical Reports Server (NTRS)

1975-01-01

A total of 68 quench tests were conducted in a vented bomb assembly (VBA). Designed to simulate full-scale motor operating conditions, this laboratory apparatus uses a 2-inch-diameter, end-burning propellant charge and an insulated disc of consolidated hydrated aluminum sulfate along with the explosive charge necessary to disperse the salt and inject it onto the burning surface. The VBA was constructed to permit variation of motor design parameters of interest; i.e., weight of salt per unit burning surface area, weight of explosive per unit weight of salt, distance from salt surface to burning surface, incidence angle of salt injection, chamber pressure, and burn time. Completely satisfactory salt quenching, without re-ignition, occurred in only two VBA tests. These were accomplished with a quench charge ratio (QCR) of 0.023 lb salt per square inch of burning surface at dispersing charge ratios (DCR) of 13 and 28 lb of salt per lb of explosive. Candidate materials for insulating salt charges from the rocket combustion environment were evaluated in firings of 5-inch-diameter, uncured end-burner motors. A pressed, alumina ceramic fiber material was selected for further evaluation and use in the final demonstration motor.

Towards Attosecond High-Energy Electron Bunches: Controlling Self-Injection in Laser-Wakefield Accelerators Through Plasma-Density Modulation

NASA Astrophysics Data System (ADS)

Tooley, M. P.; Ersfeld, B.; Yoffe, S. R.; Noble, A.; Brunetti, E.; Sheng, Z. M.; Islam, M. R.; Jaroszynski, D. A.

2017-07-01

Self-injection in a laser-plasma wakefield accelerator is usually achieved by increasing the laser intensity until the threshold for injection is exceeded. Alternatively, the velocity of the bubble accelerating structure can be controlled using plasma density ramps, reducing the electron velocity required for injection. We present a model describing self-injection in the short-bunch regime for arbitrary changes in the plasma density. We derive the threshold condition for injection due to a plasma density gradient, which is confirmed using particle-in-cell simulations that demonstrate injection of subfemtosecond bunches. It is shown that the bunch charge, bunch length, and separation of bunches in a bunch train can be controlled by tailoring the plasma density profile.

Status of the laser ion source at IMP

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sha, S.; Graduate University of Chinese Academy of Sciences, Beijing 100049; School of Nuclear science and technology, Lanzhou University, Lanzhou 73000

2012-02-15

A laser (Nd:YAG laser, 3 J, 1064 nm, 8-10 ns) ion source has been built and under development at IMP to provide pulsed high-charge-state heavy ion beams to a radio frequency quadrupole (RFQ) for upgrading the IMP accelerators with a new low-energy beam injector. The laser ion source currently operates in a direct plasma injection scheme to inject the high charge state ions produced from a solid target into the RFQ. The maximum power density on the target was about 8.4 x 10{sup 12} W/cm{sup 2}. The preliminary experimental results will be presented and discussed in this paper.

Superlattice photoelectrodes for photoelectrochemical cells

DOEpatents

Nozik, Arthur J.

1987-01-01

A superlattice or multiple-quantum-well semiconductor is used as a photoelectrode in a photoelectrochemical process for converting solar energy into useful fuels or chemicals. The quantum minibands of the superlattice or multiple-quantum-well semiconductor effectively capture hot-charge carriers at or near their discrete quantum energies and deliver them to drive a chemical reaction in an electrolyte. The hot-charge carries can be injected into the electrolyte at or near the various discrete multiple energy levels quantum minibands, or they can be equilibrated among themselves to a hot-carrier pool and then injected into the electrolyte at one average energy that is higher than the lowest quantum band gap in the semiconductor.

Rematching AGS Booster synchrotron injection lattice for smaller transverse beam emittances

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, C.; Beebe-Wang, J.; Brown, K.

2017-01-25

The polarized proton beam is injected into the booster via the charge-exchange (H- to H+) scheme. The emittance growth due to scattering at the stripping foil is proportional to the beta functions at the foil. It was demonstrated that the current scheme of reducing the beta functions at the stripping foil preserves the emittance better; however the betatron tunes are above but very close to half integer. Due to concern of space charge and half integer in general, options of lattice designs aimed towards reducing the beta functions at the stripping foil with tunes at more favorable places are explored.

A comparative study of the reduction of silver and gold salts in water by a cathodic microplasma electrode

NASA Astrophysics Data System (ADS)

De Vos, Caroline; Baneton, Joffrey; Witzke, Megan; Dille, Jean; Godet, Stéphane; Gordon, Michael J.; Mohan Sankaran, R.; Reniers, François

2017-03-01

A comparative study of the reduction of aqueous silver (Ag) and gold (Au) salts to colloidal Ag and Au nanoparticles, respectively, by a gaseous, cathodic, atmospheric-pressure microplasma electrode is presented. The resulting nanoparticles (NPs) were characterized by ultraviolet-visible (UV-vis) absorption spectroscopy and transmission electron microscopy (TEM), and the aqueous solution composition before and after experiments was determined by ionic conductivity, electrochemical potential, and/or UV-vis absorption measurements. TEM showed that Ag and Au NPs were spherical and non-agglomerated when synthesized in the presence of a stabilizer, polyvinyl alcohol. The charge injected by the plasma was correlated to the maximum intensity in the absorbance spectra which in turn depends on the nanoparticle concentration. Separately, the charge injected was correlated to the metal cation concentration. Ag and Au reduction rates were found to be directly proportional to the charge injected, independent of plasma current and process time. Differences in the mechanism for Ag and Au reduction were also observed, and solution species generated by the plasma and their role in the reduction process (e.g. H2O2, electrons) is discussed.

Low-Temperature Combustion of High Octane Fuels in a Gasoline Compression Ignition Engine

DOE PAGES

Cung, Khanh Duc; Ciatti, Stephen Anthony; Tanov, Slavey; ...

2017-12-21

Gasoline Compression Ignition (GCI) has been shown as one of the advanced combustion concepts that could potentially provide a pathway to achieve cleaner and more efficient combustion engines. Fuel and air in GCI are not fully premixed as compared to homogeneous charge compression ignition (HCCI) which is a completely kinetic-controlled combustion system. Therefore, the combustion phasing can be controlled by the time of injection, usually post injection in a multiple-injection scheme, to mitigate combustion noise. Gasoline fuels ignite more difficult than Diesel. The autoignition quality of gasoline can be indicated by research octane number (RON). Fuels with high octane tendmore » to have more resistance to auto-ignition, hence more time for fuel-air mixing. In this study, three fuels, namely, Aromatic, Alkylate, and E30, with similar RON value of 98 but different hydrocarbon compositions were tested in a multi-cylinder engine under GCI combustion mode. Considerations of EGR, start of injection (SOI), and boost were investigated to study the sensitivity of dilution, local stratification, and reactivity of the charge, respectively, for each fuel. Combustion phasing was kept constant during the experiments to the changes in ignition and combustion process before and after 50% of the fuel mass is burned. Emission characteristics at different levels of EGR and lambda were revealed for all fuels with E30 having the lowest filter smoke number (FSN) and was also most sensitive to the change in dilution. Reasonably low combustion noise (< 90 dB) and stable combustion (COVIMEP < 3%) were maintained during the experiments. The second part of this paper contains visualization of the combustion process obtained from endoscope imaging for each fuel at selected conditions. Soot radiation signal from GCI combustion were strong during late injection, and also more intense at low EGR conditions. Furthermore, soot/temperature profiles indicated only the high-temperature combustion period, while cylinder pressure-based heat release rate (HRR) showed a two-stage combustion phenomenon.« less

Low-Temperature Combustion of High Octane Fuels in a Gasoline Compression Ignition Engine

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cung, Khanh Duc; Ciatti, Stephen Anthony; Tanov, Slavey

Gasoline Compression Ignition (GCI) has been shown as one of the advanced combustion concepts that could potentially provide a pathway to achieve cleaner and more efficient combustion engines. Fuel and air in GCI are not fully premixed as compared to homogeneous charge compression ignition (HCCI) which is a completely kinetic-controlled combustion system. Therefore, the combustion phasing can be controlled by the time of injection, usually post injection in a multiple-injection scheme, to mitigate combustion noise. Gasoline fuels ignite more difficult than Diesel. The autoignition quality of gasoline can be indicated by research octane number (RON). Fuels with high octane tendmore » to have more resistance to auto-ignition, hence more time for fuel-air mixing. In this study, three fuels, namely, Aromatic, Alkylate, and E30, with similar RON value of 98 but different hydrocarbon compositions were tested in a multi-cylinder engine under GCI combustion mode. Considerations of EGR, start of injection (SOI), and boost were investigated to study the sensitivity of dilution, local stratification, and reactivity of the charge, respectively, for each fuel. Combustion phasing was kept constant during the experiments to the changes in ignition and combustion process before and after 50% of the fuel mass is burned. Emission characteristics at different levels of EGR and lambda were revealed for all fuels with E30 having the lowest filter smoke number (FSN) and was also most sensitive to the change in dilution. Reasonably low combustion noise (< 90 dB) and stable combustion (COVIMEP < 3%) were maintained during the experiments. The second part of this paper contains visualization of the combustion process obtained from endoscope imaging for each fuel at selected conditions. Soot radiation signal from GCI combustion were strong during late injection, and also more intense at low EGR conditions. Furthermore, soot/temperature profiles indicated only the high-temperature combustion period, while cylinder pressure-based heat release rate (HRR) showed a two-stage combustion phenomenon.« less

Multiplexed capillary electrophoresis system

DOEpatents

Yeung, Edward S.; Li, Qingbo; Lu, Xiandan

1998-04-21

The invention provides a side-entry optical excitation geometry for use in a multiplexed capillary electrophoresis system. A charge-injection device is optically coupled to capillaries in the array such that the interior of a capillary is imaged onto only one pixel. In Sanger-type 4-label DNA sequencing reactions, nucleotide identification ("base calling") is improved by using two long-pass filters to split fluorescence emission into two emission channels. A binary poly(ethyleneoxide) matrix is used in the electrophoretic separations.

Multiplexed capillary electrophoresis system

DOEpatents

Yeung, Edward S.; Chang, Huan-Tsang; Fung, Eliza N.; Li, Qingbo; Lu, Xiandan

1996-12-10

The invention provides a side-entry optical excitation geometry for use in a multiplexed capillary electrophoresis system. A charge-injection device is optically coupled to capillaries in the array such that the interior of a capillary is imaged onto only one pixel. In Sanger-type 4-label DNA sequencing reactions, nucleotide identification ("base calling") is improved by using two long-pass filters to split fluorescence emission into two emission channels. A binary poly(ethyleneoxide) matrix is used in the electrophoretic separations.

Multiplexed capillary electrophoresis system

DOEpatents

Yeung, E.S.; Li, Q.; Lu, X.

1998-04-21

The invention provides a side-entry optical excitation geometry for use in a multiplexed capillary electrophoresis system. A charge-injection device is optically coupled to capillaries in the array such that the interior of a capillary is imaged onto only one pixel. In Sanger-type 4-label DNA sequencing reactions, nucleotide identification (``base calling``) is improved by using two long-pass filters to split fluorescence emission into two emission channels. A binary poly(ethyleneoxide) matrix is used in the electrophoretic separations. 19 figs.

Multiplexed capillary electrophoresis system

DOEpatents

Yeung, E.S.; Chang, H.T.; Fung, E.N.; Li, Q.; Lu, X.

1996-12-10

The invention provides a side-entry optical excitation geometry for use in a multiplexed capillary electrophoresis system. A charge-injection device is optically coupled to capillaries in the array such that the interior of a capillary is imaged onto only one pixel. In Sanger-type 4-label DNA sequencing reactions, nucleotide identification (``base calling``) is improved by using two long-pass filters to split fluorescence emission into two emission channels. A binary poly(ethyleneoxide) matrix is used in the electrophoretic separations. 19 figs.

Coal-water slurry fuel internal combustion engine and method for operating same

DOEpatents

McMillian, Michael H.

1992-01-01

An internal combustion engine fueled with a coal-water slurry is described. About 90 percent of the coal-water slurry charge utilized in the power cycle of the engine is directly injected into the main combustion chamber where it is ignited by a hot stream of combustion gases discharged from a pilot combustion chamber of a size less than about 10 percent of the total clearance volume of main combustion chamber with the piston at top dead center. The stream of hot combustion gases is provided by injecting less than about 10 percent of the total coal-water slurry charge into the pilot combustion chamber and using a portion of the air from the main combustion chamber that has been heated by the walls defining the pilot combustion chamber as the ignition source for the coal-water slurry injected into the pilot combustion chamber.

Developing Density of Laser-Cooled Neutral Atoms and Molecules in a Linear Magnetic Trap

NASA Astrophysics Data System (ADS)

Velasquez, Joe, III; Walstrom, Peter; di Rosa, Michael

2013-05-01

In this poster we show that neutral particle injection and accumulation using laser-induced spin flips may be used to form dense ensembles of ultracold magnetic particles, i.e., laser-cooled paramagnetic atoms and molecules. Particles are injected in a field-seeking state, are switched by optical pumping to a field-repelled state, and are stored in the minimum-B trap. The analogous process in high-energy charged-particle accumulator rings is charge-exchange injection using stripper foils. The trap is a linear array of sextupoles capped by solenoids. Particle-tracking calculations and design of our linear accumulator along with related experiments involving 7Li will be presented. We test these concepts first with atoms in preparation for later work with selected molecules. Finally, we present our preliminary results with CaH, our candidate molecule for laser cooling. This project is funded by the LDRD program of Los Alamos National Laboratory.

High-Potential Porphyrins Supported on SnO 2 and TiO 2 Surfaces for Photoelectrochemical Applications

DOE PAGES

Jiang, Jianbing; Swierk, John R.; Materna, Kelly L.; ...

2016-12-03

Here, we report CF 3-substituted porphyrins and evaluate their use as photosensitizers in water-splitting dye-sensitized photoelectrochemical cells (WS-DSPECs) by characterizing interfacial electron transfer on metal oxide surfaces. Furthermore, by using (CF 3) 2C 6H 3 instead of C 6F 5 substituents at the meso positions, we obtain the desired high potentials while avoiding the sensitivity of C 6F 5 substituents to nucleophilic substitution, a process that limits the types of synthetic reactions that can be used. Both the number of CF 3 groups and the central metal tune the ground and excited-state potentials. A pair of porphyrins bearing carboxylic acidsmore » as anchoring groups were deposited on SnO 2 and TiO 2 surfaces and the interfacial charge-injection and charge-recombination kinetics were characterized by using a combination of computational modeling, terahertz measurements, and transient absorption spectroscopy. We also found that both free-base and metallated porphyrins inject into SnO 2, and that recombination is slower for the latter case. Our findings demonstrate that (CF 3) 2C 6H 3-substituted porphyrins are promising photosensitizers for use in WS-DSPECs.« less

Ion guiding in macro-size insulating capillaries: straight, tapered, and curved shapes

NASA Astrophysics Data System (ADS)

Kojima, Takao M.

2018-02-01

When keV energy ions are injected into a tilted insulating capillary, a certain fraction of the injected ions are transported through the tilt angle of the capillary. This ion guiding phenomenon is considered to be caused by a self-organizing charge distribution, where the inner wall of the capillary becomes charged by initial incoming ions. The charge distribution, which is formed, can guide following ions toward the exit of the capillary. Since the initial discovery of this effect, studies of ion guiding by insulating capillaries have been extended to various materials, and different sizes and shapes of capillaries. In recent years, some investigations of the guiding effect of macro-size curved capillaries have also been reported. In this review, relevant studies in a history of ion guiding in curved capillaries are discussed and future directions in this field are considered.

Parametric emittance measurements of electron beams produced by a laser plasma accelerator

NASA Astrophysics Data System (ADS)

Barber, S. K.; van Tilborg, J.; Schroeder, C. B.; Lehe, R.; Tsai, H.-E.; Swanson, K. K.; Steinke, S.; Nakamura, K.; Geddes, C. G. R.; Benedetti, C.; Esarey, E.; Leemans, W. P.

2018-05-01

Laser plasma accelerators (LPA) offer an exciting possibility to deliver high energy, high brightness electrons beams in drastically smaller distance scales than is typical for conventional accelerators. As such, LPAs draw considerable attention as potential drivers for next generation light sources and for a compact linear collider. In order to asses the viability of an LPA source for a particular application, the brightness of the source should be properly characterized. In this paper, we present charge dependent transverse emittance measurements of LPA sources using both ionization injection and shock induced density down ramp injection, with the latter delivering smaller transverse emittances by a factor of two when controlling for charge density. The single shot emittance method is described in detail with a discussion on limitations related to second order transport effects. The direct role of space charge is explored through a series of simulations and found to be consistent with experimental observations.

The influence of pre-conditioning on space charge formation in LDPE

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fleming, R.J.; Henriksen, M.; Holboell, J.T.

1996-12-31

In this paper the authors present space charge accumulation data for planar low density polyethylene samples subjected to 20kV/mm dc fields at room temperature. The data were obtained using the laser-induced-pressure-pulse (LIPP) technique. Some of the samples were conditioned by holding them at 40 C in short-circuit at rotary pump pressure for 48hr prior to measurement. Such conditioning had no consistent effect on the space charge. The extent of charge injection/extraction at the semicon electrodes appeared to vary considerably between samples.

Characterization of an atomic hydrogen source for charge exchange experiments

DOE PAGES

Leutenegger, M. A.; Beiersdorfer, P.; Betancourt-Martinez, G. L.; ...

2016-07-02

Here, we characterized the dissociation fraction of a thermal dissociation atomic hydrogen source by injecting the mixed atomic and molecular output of the source into an electron beam ion trap containing highly charged ions and recording the x-ray spectrum generated by charge exchange using a high-resolution x-ray calorimeter spectrometer. We exploit the fact that the charge exchange state-selective capture cross sections are very different for atomic and molecular hydrogen incident on the same ions, enabling a clear spectroscopic diagnostic of the neutral species.

An investigation of flow-limited field-injection electrostatic spraying (FFESS) and its applications to thin film deposition

NASA Astrophysics Data System (ADS)

Singh, Ravindra Pratap

Electrostatic spraying is the process of controlled disruption of a liquid surface due to excess surface charge density. The technique has found applications in a wide range of fields from agricultural sprays to fuel injectors to colloidal thrusters for space vehicle propulsion. Over the past 20 years, the technique has been intensely studied in material processing for synthesis of ceramic and metal powders, nanoparticles and thin films. The importance of the technique lies in its simple setup, high deposition efficiency, and ambient atmosphere operation. In conventional electrostatic spraying (CESS), one uses a conducting nozzle to charge the liquid, mostly by induction charging. CESS is therefore restricted to the single jet mode of spraying which occurs at low spray currents. It lacks stability and reproducibility in the high current, multiple jet regime, which can generate much finer sprays. In flow-limited field-injection electrostatic spraying (FFESS), one uses a field-injection electrode to stably and controllably inject higher currents into the liquid, a la Fowler-Nordheim, using an otherwise insulating nozzle. This way, it is possible to stably electrospray in the multiple jet mode. In addition to producing much finer sprays, the multi-jet mode atomizes liquids at higher rates, and spreads the spray over a wider region and more uniformly than single jet sprays, thus paving way for large-area uniform thin film deposition. A simple yet comprehensive theory is formulated to describe the multi jet formation. The theory, which is based on the energy minimization principle, takes into account, for the first time, the interactions between charged jets which leads to saturation in the number of jets at high spray currents. The possibility of using an array of nozzles to obtain uniform large-area high-throughput thin film deposition is also investigated. A large number of FFESS nozzles with alternating positive and negative polarities arranged in a periodic 2-dimensional array are found to produce uniform thin films over large areas. Deposition of TiO2 and silver thin films using multi jet FFESS is studied, demonstrating great control on film morphology and properties. TiO2 thin films deposited on high-intensity discharge arc lamps are found to improve the quality of its light output. Silver thin films of high purity and conductivity, and with good adhesion, could be deposited at relatively high deposition rates and high deposition efficiency as compared to CVD techniques.

Metastable defect response in CZTSSe from admittance spectroscopy

DOE PAGES

Koeper, Mark J.; Hages, Charles J.; Li, Jian V.; ...

2017-10-02

Admittance spectroscopy is a useful tool used to study defects in semiconductor materials. However, metastable defect responses in non-ideal semiconductors can greatly impact the measurement and therefore the interpretation of results. Here, admittance spectroscopy was performed on Cu2ZnSn(S,Se) 4 where metastable defect response is illustrated due to the trapping of injected carriers into a deep defect state. To investigate the metastable response, admittance measurements were performed under electrically and optically relaxed conditions in comparison to a device following a low level carrier-injection pretreatment. The relaxed measurement demonstrates a single capacitance signature while two capacitance signatures are observed for the devicemore » measured following carrier-injection. The deeper level signature, typically reported for kesterites, is activated by charge trapping following carrier injection. Both signatures are attributed to bulk level defects. The significant metastable response observed on kesterites due to charge trapping obscures accurate interpretation of defect levels from admittance spectroscopy and indicates that great care must be taken when performing and interpreting this measurement on non-ideal devices.« less

Core/shell colloidal quantum dot exciplex states for the development of highly efficient quantum-dot-sensitized solar cells.

PubMed

Wang, Jin; Mora-Seró, Iván; Pan, Zhenxiao; Zhao, Ke; Zhang, Hua; Feng, Yaoyu; Yang, Guang; Zhong, Xinhua; Bisquert, Juan

2013-10-23

Searching suitable panchromatic QD sensitizers for expanding the light-harvesting range, accelerating charge separation, and retarding charge recombination is an effective way to improve power conversion efficiency (PCE) of quantum-dot-sensitized solar cells (QDSCs). One possible way to obtain a wide absorption range is to use the exciplex state of a type-II core/shell-structured QDs. In addition, this system could also provide a fast charge separation and low charge-recombination rate. Herein, we report on using a CdTe/CdSe type-II core/shell QD sensitizer with an absorption range extending into the infrared region because of its exciplex state, which is covalently linked to TiO2 mesoporous electrodes by dropping a bifunctional linker molecule mercaptopropionic acid (MPA)-capped QD aqueous solution onto the film electrode. High loading and a uniform distribution of QD sensitizer throughout the film electrode thickness have been confirmed by energy dispersive X-ray (EDX) elemental mapping. The accelerated electron injection and retarded charge-recombination pathway in the built CdTe/CdSe QD cells in comparison with reference CdSe QD-based cells have been confirmed by impedance spectroscopy, fluorescence decay, and intensity-modulated photocurrent/photovoltage spectroscopy (IMPS/IMVS) analysis. With the combination of the high QD loading and intrinsically superior optoelectronic properties of type-II core/shell QD (wide absorption range, fast charge separation, and slow charge recombination), the resulting CdTe/CdSe QD-based regenerative sandwich solar cells exhibit a record PCE of 6.76% (J(sc) = 19.59 mA cm(-2), V(oc) = 0.606 V, and FF = 0.569) with a mask around the active film under a full 1 sun illumination (simulated AM 1.5), which is the highest reported to date for liquid-junction QDSCs.

Trapped charge densities in Al{sub 2}O{sub 3}-based silicon surface passivation layers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jordan, Paul M., E-mail: Paul.Jordan@namlab.com; Simon, Daniel K.; Dirnstorfer, Ingo

2016-06-07

In Al{sub 2}O{sub 3}-based passivation layers, the formation of fixed charges and trap sites can be strongly influenced by small modifications in the stack layout. Fixed and trapped charge densities are characterized with capacitance voltage profiling and trap spectroscopy by charge injection and sensing, respectively. Al{sub 2}O{sub 3} layers are grown by atomic layer deposition with very thin (∼1 nm) SiO{sub 2} or HfO{sub 2} interlayers or interface layers. In SiO{sub 2}/Al{sub 2}O{sub 3} and HfO{sub 2}/Al{sub 2}O{sub 3} stacks, both fixed charges and trap sites are reduced by at least a factor of 5 compared with the value measured inmore » pure Al{sub 2}O{sub 3}. In Al{sub 2}O{sub 3}/SiO{sub 2}/Al{sub 2}O{sub 3} or Al{sub 2}O{sub 3}/HfO{sub 2}/Al{sub 2}O{sub 3} stacks, very high total charge densities of up to 9 × 10{sup 12} cm{sup −2} are achieved. These charge densities are described as functions of electrical stress voltage, time, and the Al{sub 2}O{sub 3} layer thickness between silicon and the HfO{sub 2} or the SiO{sub 2} interlayer. Despite the strong variation of trap sites, all stacks reach very good effective carrier lifetimes of up to 8 and 20 ms on p- and n-type silicon substrates, respectively. Controlling the trap sites in Al{sub 2}O{sub 3} layers opens the possibility to engineer the field-effect passivation in the solar cells.« less

Charge Modulation in Graphitic Carbon Nitride as a Switchable Approach to High-Capacity Hydrogen Storage.

PubMed

Tan, Xin; Kou, Liangzhi; Tahini, Hassan A; Smith, Sean C

2015-11-01

Electrical charging of graphitic carbon nitride nanosheets (g-C4 N3 and g-C3 N4 ) is proposed as a strategy for high-capacity and electrocatalytically switchable hydrogen storage. Using first-principle calculations, we found that the adsorption energy of H2 molecules on graphitic carbon nitride nanosheets is dramatically enhanced by injecting extra electrons into the adsorbent. At full hydrogen coverage, the negatively charged graphitic carbon nitride achieves storage capacities up to 6-7 wt %. In contrast to other hydrogen storage approaches, the storage/release occurs spontaneously once extra electrons are introduced or removed, and these processes can be simply controlled by switching on/off the charging voltage. Therefore, this approach promises both facile reversibility and tunable kinetics without the need of specific catalysts. Importantly, g-C4 N3 has good electrical conductivity and high electron mobility, which can be a very good candidate for electron injection/release. These predictions may prove to be instrumental in searching for a new class of high-capacity hydrogen storage materials. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Photoinduced charge transfer from vacuum-deposited molecules to single-layer transition metal dichalcogenides

NASA Astrophysics Data System (ADS)

Osada, Kazuki; Tanaka, Masatoshi; Ohno, Shinya; Suzuki, Takanori

2016-06-01

Variations of photoluminescence (PL) and Raman spectra of single-layer MoS2, MoSe2, WS2, and WSe2 due to the vacuum deposition of C60 or copper phthalocyanine (CuPc) molecules have been investigated. PL spectra are decomposed into two competitive components, an exciton and a charged exciton (trion), depending on carrier density. The variation of PL spectra is interpreted in terms of charge transfer across the interfaces between transition metal dichalcogenides (TMDs) and dopant molecules. We find that deposited C60 molecules inject photoexcited electrons into MoS2, MoSe2, and WS2 or holes into WSe2. CuPc molecules also inject electrons into MoS2, MoSe2, and WS2, while holes are depleted from WSe2 to CuPc. We then propose a band alignment between TMDs and dopant molecules. Peak shifts of Raman spectra and doped carrier density estimated using a three-level model also support the band alignment. We thus demonstrate photoinduced charge transfer from dopant molecules to single-layer TMDs.

Using quantum dot photoluminescence for load detection

NASA Astrophysics Data System (ADS)

Moebius, M.; Martin, J.; Hartwig, M.; Baumann, R. R.; Otto, T.; Gessner, T.

2016-08-01

We propose a novel concept for an integrable and flexible sensor capable to visualize mechanical impacts on lightweight structures by quenching the photoluminescence (PL) of CdSe quantum dots. Considering the requirements such as visibility, storage time and high optical contrast of PL quenching with low power consumption, we have investigated a symmetrical and an asymmetrical layer stack consisting of semiconductor organic N,N,N',N'-Tetrakis(3-methylphenyl)-3,3'-dimethylbenzidine (HMTPD) and CdSe quantum dots with elongated CdS shell. Time-resolved series of PL spectra from layer stacks with applied voltages of different polarity and simultaneous observation of power consumption have shown that a variety of mechanisms such as photo-induced charge separation and charge injection, cause PL quenching. However, mechanisms such as screening of external field as well as Auger-assisted charge ejection is working contrary to that. Investigations regarding the influence of illumination revealed that the positive biased asymmetrical layer stack is the preferred sensor configuration, due to a charge carrier injection at voltages of 10 V without the need of coincident illumination.

Evidence and implications of direct charge excitation as the dominant mechanism in plasmon-mediated photocatalysis

DOE PAGES

Boerigter, Calvin; Campana, Robert; Morabito, Matthew; ...

2016-01-28

Plasmonic metal nanoparticles enhance chemical reactions on their surface when illuminated with light of particular frequencies. It has been shown that these processes are driven by excitation of localized surface plasmon resonance (LSPR). The interaction of LSPR with adsorbate orbitals can lead to the injection of energized charge carriers into the adsorbate, which can result in chemical transformations. The mechanism of the charge injection process (and role of LSPR) is not well understood. Here we shed light on the specifics of this mechanism by coupling optical characterization methods, mainly wavelength-dependent Stokes and anti-Stokes SERS, with kinetic analysis of photocatalytic reactionsmore » in an Ag nanocube–methylene blue plasmonic system. We propose that localized LSPR-induced electric fields result in a direct charge transfer within the molecule–adsorbate system. Lastly, these observations provide a foundation for the development of plasmonic catalysts that can selectively activate targeted chemical bonds, since the mechanism allows for tuning plasmonic nanomaterials in such a way that illumination can selectively enhance desired chemical pathways.« less

Silane-propane ignitor/burner

DOEpatents

Hill, R.W.; Skinner, D.F. Jr.; Thorsness, C.B.

1983-05-26

A silane propane burner for an underground coal gasification process which is used to ignite the coal and to controllably retract the injection point by cutting the injection pipe. A narrow tube with a burner tip is positioned in the injection pipe through which an oxidant (oxygen or air) is flowed. A charge of silane followed by a supply of fuel, such as propane, is flowed through the tube. The silane spontaneously ignites on contact with oxygen and burns the propane fuel.

Silane-propane ignitor/burner

DOEpatents

Hill, Richard W.; Skinner, Dewey F.; Thorsness, Charles B.

1985-01-01

A silane propane burner for an underground coal gasification process which is used to ignite the coal and to controllably retract the injection point by cutting the injection pipe. A narrow tube with a burner tip is positioned in the injection pipe through which an oxidant (oxygen or air) is flowed. A charge of silane followed by a supply of fuel, such as propane, is flowed through the tube. The silane spontaneously ignites on contact with oxygen and burns the propane fuel.

A simulation study of radial expansion of an electron beam injected into an ionospheric plasma

NASA Technical Reports Server (NTRS)

Koga, J.; Lin, C. S.

1994-01-01

Injections of nonrelativistic electron beams from a finite equipotential conductor into an ionospheric plasma have been simulated using a two-dimensional electrostatic particle code. The purpose of the study is to survey the simulation parameters for understanding the dependence of beam radius on physical variables. The conductor is charged to a high potential when the background plasma density is less than the beam density. Beam electrons attracted by the charged conductor are decelerated to zero velocity near the stagnation point, which is at a few Debye lengths from the conductor. The simulations suggest that the beam electrons at the stagnation point receive a large transverse kick and the beam expands radially thereafter. The buildup of beam electrons at the stagnation point produces a large electrostatic force responsible for the transverse kick. However, for the weak charging cases where the background plasma density is larger than the beam density, the radial expansion mechanism is different; the beam plasma instability is found to be responsible for the radial expansion. The simulations show that the electron beam radius for high spacecraft charging cases is of the order of the beam gyroradius, defined as the beam velocity divided by the gyrofrequency. In the weak charging cases, the beam radius is only a fraction of the beam gyroradius. The parameter survey indicates that the beam radius increases with beam density and decreases with magnetic field and beam velocity. The beam radius normalized by the beam gyroradius is found to scale according to the ratio of the beam electron Debye length to the ambient electron Debye length. The parameter dependence deduced would be useful for interpreting the beam radius and beam density of electron beam injection experiments conducted from rockets and the space shuttle.

Measurements and PHITS Monte Carlo Estimations of Residual Activities Induced by the 181 MeV Proton Beam in the Injection Area at J-PARC RCS Ring

NASA Astrophysics Data System (ADS)

Yamakawa, Emi; Yoshimoto, Masahiro; Kinsho, Michikazu

At the injection area of the RCS ring in the J-PARC, residual gamma dose at the rectangular ceramic ducts, especially immediately downstream of the charge-exchanged foil, has increased with the output beam power. In order to investigate the cause of high residual activities, residual gamma dose and radioactive sources produced at the exterior surface of the ducts have been measured by a GM survey meter and a handy type of Germanium (Ge) semiconductor detector in the case of 181 MeV injected proton beam energy. With these measurements, it is revealed that the radioactive sources produced by nuclear reactions cause the high activities at the injection area. For a better understanding of phenomena in the injection area, various simulations have been done with the PHITS Monte Carlo code. The distribution of radioactive sources and residual gamma dose rate obtained by the calculations are consistent with the measurement results. With this consistency, secondary neutrons and protons derived from nuclear reactions at the charge-exchanged foil are the dominant cause to high residual gamma dose at the ceramic ducts in the injection area. These measurements and calculations are unique approaches to reveal the cause of high residual dose around the foil. This study is essential for the future of high-intensity proton accelerators using a stripping foil.

Electrical and dielectric properties of foam injection-molded polypropylene/multiwalled carbon nanotube composites

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ameli, A.; Nofar, M.; Saniei, M.

A combination of high dielectric permittivity (ε′) and low dielectric loss (tan δ) is required for charge storage applications. In percolative systems such as conductive polymer composites, however, obtaining high ε′ and low tan δ is very challenging due to the sharp insulation-conduction transition near the threshold region. Due to the particular arrangement of conductive fillers induced by both foaming and injection molding processes, they may address this issue. Therefore, this work evaluates the application of foam injection molding process in fabricating polymer nanocomposites for energy storage. Polypropylene-multiwalled carbon nanotubes (PP-MWCNT) composites were prepared by melt mixing and foamed inmore » an injection molding process. Electrical conductivity (σ), ε′ and tan δ were then characterized. Also, scanning and transmission electron microscopy (SEM and TEM) was used to investigate the carbon nanotube’s arrangement as well as cellular morphology. The results showed that foam injection-molded composites exhibited highly superior dielectric properties to those of solid counterparts. For instance, foamed samples had ε′=68.3 and tan δ =0.05 (at 1.25 vol.% MWCNT), as opposed to ε′=17.8 and tan δ=0.04 in solid samples (at 2.56 vol.% MWCNT). The results of this work reveal that high performance dielectric nanocomposites can be developed using foam injection molding technologies for charge storage applications.« less

Nonlinear and Nonequilibrium Spin Injection in Magnetic Tunneling Junctions

NASA Astrophysics Data System (ADS)

Guo, Hong

2007-03-01

Quantitative analysis of charge and spin quantum transport in spintronic devices requires an atomistic first principles approach that can handle nonlinear and nonequilibrium transport conditions. We have developed an approach for this purpose based on real space density functional theory (DFT) carried out within the Keldysh nonequilibrium Green's function formalism (NEGF). We report theoretical analysis of nonlinear and nonequilibrium spin injection and quantum transport in Fe/MgO/Fe trilayer structures as a function of external bias voltage. Devices with well relaxed atomic structures and with FeO oxidization layers are investigated as a function of external bias voltage. We also report calculations of nonequilibrium spin injection into molecular layers and graphene. Comparisons to experimental data will be presented. Work in collaborations with: Derek Waldron, Vladimir Timochevski (McGill University); Ke Xia (Institute of Physics, Chinese Academy of Science, Beijing, China); Eric Zhu, Jian Wang (University of Hong Kong); Paul Haney, and Allan MacDonald (University of Texas at Austin).

Enhanced Tunnel Spin Injection into Graphene using Chemical Vapor Deposited Hexagonal Boron Nitride

PubMed Central

Kamalakar, M. Venkata; Dankert, André; Bergsten, Johan; Ive, Tommy; Dash, Saroj P.

2014-01-01

The van der Waals heterostructures of two-dimensional (2D) atomic crystals constitute a new paradigm in nanoscience. Hybrid devices of graphene with insulating 2D hexagonal boron nitride (h-BN) have emerged as promising nanoelectronic architectures through demonstrations of ultrahigh electron mobilities and charge-based tunnel transistors. Here, we expand the functional horizon of such 2D materials demonstrating the quantum tunneling of spin polarized electrons through atomic planes of CVD grown h-BN. We report excellent tunneling behavior of h-BN layers together with tunnel spin injection and transport in graphene using ferromagnet/h-BN contacts. Employing h-BN tunnel contacts, we observe enhancements in both spin signal amplitude and lifetime by an order of magnitude. We demonstrate spin transport and precession over micrometer-scale distances with spin lifetime up to 0.46 nanosecond. Our results and complementary magnetoresistance calculations illustrate that CVD h-BN tunnel barrier provides a reliable, reproducible and alternative approach to address the conductivity mismatch problem for spin injection into graphene. PMID:25156685

The role of electronic coupling between substrate and 2D MoS2 nanosheets in electrocatalytic production of hydrogen.

PubMed

Voiry, Damien; Fullon, Raymond; Yang, Jieun; de Carvalho Castro E Silva, Cecilia; Kappera, Rajesh; Bozkurt, Ibrahim; Kaplan, Daniel; Lagos, Maureen J; Batson, Philip E; Gupta, Gautam; Mohite, Aditya D; Dong, Liang; Er, Dequan; Shenoy, Vivek B; Asefa, Tewodros; Chhowalla, Manish

2016-09-01

The excellent catalytic activity of metallic MoS2 edges for the hydrogen evolution reaction (HER) has led to substantial efforts towards increasing the edge concentration. The 2H basal plane is less active for the HER because it is less conducting and therefore possesses less efficient charge transfer kinetics. Here we show that the activity of the 2H basal planes of monolayer MoS2 nanosheets can be made comparable to state-of-the-art catalytic properties of metallic edges and the 1T phase by improving the electrical coupling between the substrate and the catalyst so that electron injection from the electrode and transport to the catalyst active site is facilitated. Phase-engineered low-resistance contacts on monolayer 2H-phase MoS2 basal plane lead to higher efficiency of charge injection in the nanosheets so that its intrinsic activity towards the HER can be measured. We demonstrate that onset potentials and Tafel slopes of ∼-0.1 V and ∼50 mV per decade can be achieved from 2H-phase catalysts where only the basal plane is exposed. We show that efficient charge injection and the presence of naturally occurring sulfur vacancies are responsible for the observed increase in catalytic activity of the 2H basal plane. Our results provide new insights into the role of contact resistance and charge transport on the performance of two-dimensional MoS2 nanosheet catalysts for the HER.

Size and Temperature Dependence of Electron Transfer between CdSe Quantum Dots and a TiO 2 Nanobelt

DOE PAGES

Tafen, De Nyago; Prezhdo, Oleg V.

2015-02-24

Understanding charge transfer reactions between quantum dots (QD) and metal oxides is fundamental for improving photocatalytic, photovoltaic and electronic devices. The complexity of these processes makes it difficult to find an optimum QD size with rapid charge injection and low recombination. We combine time-domain density functional theory with nonadiabatic molecular dynamics to investigate the size and temperature dependence of the experimentally studied electron transfer and charge recombination at CdSe QD-TiO 2 nanobelt (NB) interfaces. The electron injection rate shows strong dependence on the QD size, increasing for small QDs. The rate exhibits Arrhenius temperature dependence, with the activation energy ofmore » the order of millielectronvolts. The charge recombination process occurs due to coupling of the electronic subsystem to vibrational modes of the TiO 2 NB. Inelastic electron-phonon scattering happens on a picosecond time scale, with strong dependence on the QD size. Our simulations demonstrate that the electron-hole recombination rate decreases significantly as the QD size increases, in excellent agreement with experiments. The temperature dependence of the charge recombination rates can be successfully modeled within the framework of the Marcus theory through optimization of the electronic coupling and the reorganization energy. Our simulations indicate that by varying the QD size, one can modulate the photoinduced charge separation and charge recombination, fundamental aspects of the design principles for high efficiency devices.« less

Investigation of methyl decanoate combustion in an optical direct-injection diesel engine

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cheng, A. S.; Dumitrescu, Cosmin E.; Mueller, Charles J.

In this study, an optically accessible heavy-duty diesel engine was used to investigate the impact of methyl decanoate (MD) on combustion and emissions. A specific goal of the study was to determine if MD could enable soot-free leaner-lifted flame combustion (LLFC) – a mode of mixing-controlled combustion associated with fuel-air equivalence ratios below approximately two. An ultra-low sulfur diesel certification fuel (CF) was used as the baseline fuel, and experiments were conducted at two fuel-injection pressures with three levels of charge-gas dilution. In addition to conventional pressure-based and engine-out emissions measurements, exhaust laser-induced incandescence, in-cylinder natural luminosity (NL), and in-cylindermore » chemiluminescence (CL) diagnostics were used to provide detailed insight into combustion processes.« less

Investigation of methyl decanoate combustion in an optical direct-injection diesel engine

DOE PAGES

Cheng, A. S.; Dumitrescu, Cosmin E.; Mueller, Charles J.

2014-11-24

In this study, an optically accessible heavy-duty diesel engine was used to investigate the impact of methyl decanoate (MD) on combustion and emissions. A specific goal of the study was to determine if MD could enable soot-free leaner-lifted flame combustion (LLFC) – a mode of mixing-controlled combustion associated with fuel-air equivalence ratios below approximately two. An ultra-low sulfur diesel certification fuel (CF) was used as the baseline fuel, and experiments were conducted at two fuel-injection pressures with three levels of charge-gas dilution. In addition to conventional pressure-based and engine-out emissions measurements, exhaust laser-induced incandescence, in-cylinder natural luminosity (NL), and in-cylindermore » chemiluminescence (CL) diagnostics were used to provide detailed insight into combustion processes.« less

Universal Disorder in Organic Semiconductors Due to Fluctuations in Space Charge

NASA Astrophysics Data System (ADS)

Wu, Tzu-Cheng

This thesis concerns the study of charge transport in organic semiconductors. These materials are widely used as thin-film photoconductors in copiers and laser printers, and for their electroluminescent properties in organic light-emitting diodes. Much contemporary research is directed towards improving the efficiency of organic photovoltaic devices, which is limited to a large extent by the spatial and energetic disorder that hinders the charge mobility. One contribution to energetic disorder arises from the strong Coulomb interactions between injected charges with one another, but to date this has been largely ignored. We present a mean-field model for the effect of mutual interactions between injected charges hopping from site to site in an organic semiconductor. Our starting point is a modified Fröhlich Hamiltonian in which the charge is linearly coupled to the amplitudes of a wide band of dispersionless plasma modes having a Lorentzian distribution of frequencies. We show that in most applications of interest the hopping rates are fast enough while the plasma frequencies are low enough that random thermal fluctuations in the plasma density give rise to an energetically disordered landscape that is effectively stationary for many thousands of hops. Moreover, the distribution of site energies is Gaussian, and the energy-energy correlation function decays inversely with distance; as such, it can be argued that this disorder contributes to the Poole-Frenkel field dependence seen in a wide variety of experiments. Remarkably, the energetic disorder is universal; although it is caused by the fluctuations in the charge density, it is independent of the charge concentration.

Enhanced Electron Injection and Exciton Confinement for Pure Blue Quantum-Dot Light-Emitting Diodes by Introducing Partially Oxidized Aluminum Cathode.

PubMed

Wang, Zhibin; Cheng, Tai; Wang, Fuzhi; Bai, Yiming; Bian, Xingming; Zhang, Bing; Hayat, Tasawar; Alsaedi, Ahmed; Tan, Zhan'ao

2018-05-31

Stable and efficient red (R), green (G), and blue (B) light sources based on solution-processed quantum dots (QDs) play important roles in next-generation displays and solid-state lighting technologies. The brightness and efficiency of blue QDs-based light-emitting diodes (LEDs) remain inferior to their red and green counterparts, due to the inherently unfavorable energy levels of different colors of light. To solve these problems, a device structure should be designed to balance the injection holes and electrons into the emissive QD layer. Herein, through a simple autoxidation strategy, pure blue QD-LEDs which are highly bright and efficient are demonstrated, with a structure of ITO/PEDOT:PSS/Poly-TPD/QDs/Al:Al2O3. The autoxidized Al:Al2O3 cathode can effectively balance the injected charges and enhance radiative recombination without introducing an additional electron transport layer (ETL). As a result, high color-saturated blue QD-LEDs are achieved with a maximum luminance over 13,000 cd m -2 , and a maximum current efficiency of 1.15 cd A -1 . The easily controlled autoxidation procedure paves the way for achieving high-performance blue QD-LEDs.

Spray Formation from a Charged Liquid Jet of a Dielectric Fluid

NASA Astrophysics Data System (ADS)

Doak, William; de Bellis, Victor; Chiarot, Paul; Microfluidics; Multiphase Flow Laboratory Team

2017-11-01

Atomization of a dielectric micro-jet is achieved via an electrohydrodynamic charge injection process. The atomizer is comprised of a grounded nozzle housing (ground electrode) and an internal probe (high voltage electrode) that is concentric with the emitting orifice. The internal probe is held at electric potentials ranging from 1-10 kV. A pressurized reservoir drives a dielectric fluid at a desired flow rate through the 100-micrometer diameter orifice. The fluid fills the cavity between the electrodes as it passes through the atomizer, impeding the transport of electrons. This process injects charge into the flowing fluid. Upon exiting the orifice, the emitted jet is highly charged and it deforms via a bending instability that is qualitatively similar to the behavior observed in the electrospinning of fibers. We observed bulging regions, or nodes, of highly charged fluid forming along the bent, rotating jet. These nodes separate into highly charged droplets that emit satellite droplets. The remaining ligaments break up due to capillarity in a process that produces additional satellites. All of the droplets possess a normal (inertial) and radial (electrically-driven) momentum component. The radial component is responsible for the formation of a conical spray envelope. Our research focuses on the jet, its break up, and the droplet dynamics of this system. This research supported by the American Chemical Society.

Cyanopyridine Based Bipolar Host Materials for Green Electrophosphorescence with Extremely Low Turn-On Voltages and High Power Efficiencies.

PubMed

Li, Wei; Li, Jiuyan; Liu, Di; Li, Deli; Wang, Fang

2016-08-24

Low driving voltage and high power efficiency are basic requirements when practical applications of organic light emitting diodes (OLEDs) in displays and lighting are considered. Two novel host materials m-PyCNmCP and 3-PyCNmCP incorporating cyanopyridine moiety as electron-transporting unit are developed for use in fac-tris(2-phenylpyridine)iridium(III) (Ir(ppy)3) based green phosphorescent OLEDs (PhOLEDs). Extremely low turn-on voltages of 2.01 and 2.27 V are realized, which are even lower than the theoretical limit of the emitted photon energy (hv)/electron charge (e) (2.37 V) of Ir(ppy)3. High power efficiency of 101.4 lm/W (corresponding to a maximum external quantum efficiency of 18.4%) and 119.3 lm/W (24.7%) are achieved for m-PyCNmCP and 3-PyCNmCP based green PhOLEDs. The excellent EL performance benefits from the ideal parameters of host materials by combining cyano and pyridine to enhance the n-type feature. The energetic favorable alignment of HOMO/LUMO levels of hosts with adjacent layers and the dopant for easy charge injections and direct charge trapping by dopant, their bipolar feature to balance charge transportations, sufficiently high triplet energy and small singlet/triplet energy difference (0.38 and 0.43 eV) combine to be responsible for the extremely low driving voltages and high power efficiencies of the green PhOLEDs.

Using Quasi-3D OSIRIS simulations of LWFA to study generating high brightness electron beams using ionization and density downramp injection

NASA Astrophysics Data System (ADS)

Dalichaouch, Thamine; Davidson, Asher; Xu, Xinlu; Yu, Peicheng; Tsung, Frank; Mori, Warren; Li, Fei; Zhang, Chaojie; Lu, Wei; Vieira, Jorge; Fonseca, Ricardo

2016-10-01

In the past few decades, there has been much progress in theory, simulation, and experiment towards using Laser wakefield acceleration (LWFA) as the basis for designing and building compact x-ray free-electron-lasers (XFEL) as well as a next generation linear collider. Recently, ionization injection and density downramp injection have been proposed and demonstrated as a controllable injection scheme for creating higher quality and ultra-bright relativistic electron beams using LWFA. However, full-3D simulations of plasma-based accelerators are computationally intensive, sometimes taking 100 millions of core-hours on today's computers. A more efficient quasi-3D algorithm was developed and implemented into OSIRIS using a particle-in-cell description with a charge conserving current deposition scheme in r - z and a gridless Fourier expansion in ϕ. Due to the azimuthal symmetry in LWFA, quasi-3D simulations are computationally more efficient than 3D cartesian simulations since only the first few harmonics in are needed ϕ to capture the 3D physics of LWFA. Using the quasi-3D approach, we present preliminary results of ionization and down ramp triggered injection and compare the results against 3D LWFA simulations. This work was supported by DOE and NSF.

Metal oxide induced charge transfer doping and band alignment of graphene electrodes for efficient organic light emitting diodes.

PubMed

Meyer, Jens; Kidambi, Piran R; Bayer, Bernhard C; Weijtens, Christ; Kuhn, Anton; Centeno, Alba; Pesquera, Amaia; Zurutuza, Amaia; Robertson, John; Hofmann, Stephan

2014-06-20

The interface structure of graphene with thermally evaporated metal oxide layers, in particular molybdenum trioxide (MoO3), is studied combining photoemission spectroscopy, sheet resistance measurements and organic light emitting diode (OLED) characterization. Thin (<5 nm) MoO3 layers give rise to an 1.9 eV large interface dipole and a downwards bending of the MoO3 conduction band towards the Fermi level of graphene, leading to a near ideal alignment of the transport levels. The surface charge transfer manifests itself also as strong and stable p-type doping of the graphene layers, with the Fermi level downshifted by 0.25 eV and sheet resistance values consistently below 50 Ω/sq for few-layer graphene films. The combination of stable doping and highly efficient charge extraction/injection allows the demonstration of simplified graphene-based OLED device stacks with efficiencies exceeding those of standard ITO reference devices.

Studies of charge transport in DNA films using the time-of-flight (TOF) technique

NASA Astrophysics Data System (ADS)

Yaney, Perry P.; Gorman, Timothy; Ouchen, Fahima; Grote, James G.

2011-09-01

Measurements were carried out on salmon DNA-based films, including as-received DNA (molecular weight, MW>2000 kDa) without and with hexacetyltrimethl-ammonium chloride (CTMA) surfactant, and sonicated DNA of MW~200 kDa with CTMA. The test specimens were spin-coated or drop-cast films on ITO-coated quartz slides with a gold charge-collecting electrode. To protect the films from atmospheric influences, the TOF devices were coated with a 200-400 nm polyurethane passivation layer. A quadrupled 20 ns, pulsed Nd:YAG laser with output at 266 nm was used for charge injection. The room temperature photoconductive transients were dispersive to varying degrees with hole mobilities in DNA materials films ranging between 2E-5 to 6E-3 cm2/Vs for fields ranging from 8 to 58 kV/cm. Only hole response was observed in DNA. The dispersive data were analyzed using a simple, quasi-empirical equation for the photocurrent transient data.

Charge Transfer from Carbon Nanotubes to Silicon in Flexible Carbon Nanotube/Silicon Solar Cells

DOE PAGES

Li, Xiaokai; Mariano, Marina; McMillon-Brown, Lyndsey; ...

2017-11-10

Mechanical fragility and insufficient light absorption are two major challenges for thin flexible crystalline Si-based solar cells. Flexible hybrid single-walled carbon nanotube (SWNT)/Si solar cells are demonstrated by applying scalable room-temperature processes for the fabrication of solar-cell components (e.g., preparation of SWNT thin films and SWNT/Si p–n junctions). The flexible SWNT/Si solar cells present an intrinsic efficiency ≈7.5% without any additional light-trapping structures. By using these solar cells as model systems, the charge transport mechanisms at the SWNT/Si interface are investigated using femtosecond transient absorption. Although primary photon absorption occurs in Si, transient absorption measurements show that SWNTs also generatemore » and inject excited charge carriers to Si. Such effects can be tuned by controlling the thickness of the SWNTs. Thus, findings from this study could open a new pathway for designing and improving the efficiency of photocarrier generation and absorption for high-performance ultrathin hybrid SWNT/Si solar cells.« less

Highly reliable top-gated thin-film transistor memory with semiconducting, tunneling, charge-trapping, and blocking layers all of flexible polymers.

PubMed

Wang, Wei; Hwang, Sun Kak; Kim, Kang Lib; Lee, Ju Han; Cho, Suk Man; Park, Cheolmin

2015-05-27

The core components of a floating-gate organic thin-film transistor nonvolatile memory (OTFT-NVM) include the semiconducting channel layer, tunneling layer, floating-gate layer, and blocking layer, besides three terminal electrodes. In this study, we demonstrated OTFT-NVMs with all four constituent layers made of polymers based on consecutive spin-coating. Ambipolar charges injected and trapped in a polymer electret charge-controlling layer upon gate program and erase field successfully allowed for reliable bistable channel current levels at zero gate voltage. We have observed that the memory performance, in particular the reliability of a device, significantly depends upon the thickness of both blocking and tunneling layers, and with an optimized layer thickness and materials selection, our device exhibits a memory window of 15.4 V, on/off current ratio of 2 × 10(4), read and write endurance cycles over 100, and time-dependent data retention of 10(8) s, even when fabricated on a mechanically flexible plastic substrate.

A numerical study on the charge transport in TPD/Alq3-based organic light emitting diodes.

PubMed

Kim, K S; Hwang, Y W; Lee, H G; Won, T Y

2014-08-01

We report our simulation study on the charge transport characteristic of the multi-layer structure for organic light emitting diodes (OLEDs). We performed a numerical simulation on a multilayer structure comprising a hole transport layer (HTL), an emission layer (EML), and an electron transport layer (ETL) between both electrodes. The material of the HTL is TPD (N,N'-Bis (3-methylphenyl)-N,N'-bis(phenyl) benzidine), and the ETL includes Alq3 (Tris (8-hyroxyquinolinato) aluminium). Here, we investigated the parameters such as recombination rates which influence the efficiency of the charge transport between layers in bilayer OLEDs. We also analyzed a transient response during the turn on/off period and the carrier transport in accordance with the variation of the injection barrier and applied voltage. In addition, our numerical simulation revealed that the insertion of the EML affects the photonic characteristics in bilayer structure and also the efficiency due to the difference in the internal barrier height.

Experimental setup for camera-based measurements of electrically and optically stimulated luminescence of silicon solar cells and wafers.

PubMed

Hinken, David; Schinke, Carsten; Herlufsen, Sandra; Schmidt, Arne; Bothe, Karsten; Brendel, Rolf

2011-03-01

We report in detail on the luminescence imaging setup developed within the last years in our laboratory. In this setup, the luminescence emission of silicon solar cells or silicon wafers is analyzed quantitatively. Charge carriers are excited electrically (electroluminescence) using a power supply for carrier injection or optically (photoluminescence) using a laser as illumination source. The luminescence emission arising from the radiative recombination of the stimulated charge carriers is measured spatially resolved using a camera. We give details of the various components including cameras, optical filters for electro- and photo-luminescence, the semiconductor laser and the four-quadrant power supply. We compare a silicon charged-coupled device (CCD) camera with a back-illuminated silicon CCD camera comprising an electron multiplier gain and a complementary metal oxide semiconductor indium gallium arsenide camera. For the detection of the luminescence emission of silicon we analyze the dominant noise sources along with the signal-to-noise ratio of all three cameras at different operation conditions.

Charge Transfer from Carbon Nanotubes to Silicon in Flexible Carbon Nanotube/Silicon Solar Cells

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Xiaokai; Mariano, Marina; McMillon-Brown, Lyndsey

Mechanical fragility and insufficient light absorption are two major challenges for thin flexible crystalline Si-based solar cells. Flexible hybrid single-walled carbon nanotube (SWNT)/Si solar cells are demonstrated by applying scalable room-temperature processes for the fabrication of solar-cell components (e.g., preparation of SWNT thin films and SWNT/Si p–n junctions). The flexible SWNT/Si solar cells present an intrinsic efficiency ≈7.5% without any additional light-trapping structures. By using these solar cells as model systems, the charge transport mechanisms at the SWNT/Si interface are investigated using femtosecond transient absorption. Although primary photon absorption occurs in Si, transient absorption measurements show that SWNTs also generatemore » and inject excited charge carriers to Si. Such effects can be tuned by controlling the thickness of the SWNTs. Thus, findings from this study could open a new pathway for designing and improving the efficiency of photocarrier generation and absorption for high-performance ultrathin hybrid SWNT/Si solar cells.« less

Hall-Effect Based Semi-Fast AC On-Board Charging Equipment for Electric Vehicles

PubMed Central

Milanés-Montero, María Isabel; Gallardo-Lozano, Javier; Romero-Cadaval, Enrique; González-Romera, Eva

2011-01-01

The expected increase in the penetration of electric vehicles (EV) and plug-in hybrid electric vehicles (PHEV) will produce unbalanced conditions, reactive power consumption and current harmonics drawn by the battery charging equipment, causing a great impact on the power quality of the future smart grid. A single-phase semi-fast electric vehicle battery charger is proposed in this paper. This ac on-board charging equipment can operate in grid-to-vehicle (G2V) mode, and also in vehicle-to-grid (V2G) mode, transferring the battery energy to the grid when the vehicle is parked. The charger is controlled with a Perfect Harmonic Cancellation (PHC) strategy, contributing to improve the grid power quality, since the current demanded or injected has no harmonic content and a high power factor. Hall-effect current and voltage transducers have been used in the sensor stage to carry out this control strategy. Experimental results with a laboratory prototype are presented. PMID:22163697

Hall-effect based semi-fast AC on-board charging equipment for electric vehicles.

PubMed

Milanés-Montero, María Isabel; Gallardo-Lozano, Javier; Romero-Cadaval, Enrique; González-Romera, Eva

2011-01-01

The expected increase in the penetration of electric vehicles (EV) and plug-in hybrid electric vehicles (PHEV) will produce unbalanced conditions, reactive power consumption and current harmonics drawn by the battery charging equipment, causing a great impact on the power quality of the future smart grid. A single-phase semi-fast electric vehicle battery charger is proposed in this paper. This ac on-board charging equipment can operate in grid-to-vehicle (G2V) mode, and also in vehicle-to-grid (V2G) mode, transferring the battery energy to the grid when the vehicle is parked. The charger is controlled with a Perfect Harmonic Cancellation (PHC) strategy, contributing to improve the grid power quality, since the current demanded or injected has no harmonic content and a high power factor. Hall-effect current and voltage transducers have been used in the sensor stage to carry out this control strategy. Experimental results with a laboratory prototype are presented.

Effect of oxide insertion layer on resistance switching properties of copper phthalocyanine

NASA Astrophysics Data System (ADS)

Joshi, Nikhil G.; Pandya, Nirav C.; Joshi, U. S.

2013-02-01

Organic memory device showing resistance switching properties is a next-generation of the electrical memory unit. We have investigated the bistable resistance switching in current-voltage (I-V) characteristics of organic diode based on copper phthalocyanine (CuPc) film sandwiched between aluminum (Al) electrodes. Pronounced hysteresis in the I-V curves revealed a resistance switching with on-off ratio of the order of 85%. In order to control the charge injection in the CuPc, nanoscale indium oxide buffer layer was inserted to form Al/CuPc/In2O3/Al device. Analysis of I-V measurements revealed space charge limited switching conduction at the Al/CuPc interface. The traps in the organic layer and charge blocking by oxide insertion layer have been used to explain the absence of resistance switching in the oxide buffer layered memory device cell. Present study offer potential applications for CuPc organic semiconductor in low power non volatile resistive switching memory and logic circuits.

Diagnostic experiments at a 3 MeV test stand at Rutherford Appleton Laboratory (United Kingdom).

PubMed

Gabor, C; Faircloth, D C; Lee, D A; Lawrie, S R; Letchford, A P; Pozimski, J K

2010-02-01

A front end is currently under construction consisting of a H(-) Penning ion source (65 keV, 60 mA), low energy beam transport (LEBT), and radio frequency quadrupole (3 MeV output energy) with a medium energy beam transport suitable for high power proton applications. Diagnostics can be divided either in destructive techniques such as beam profile monitor, pepperpot, slit-slit emittance scanner (preferably used during commissioning) or nondestructive, permanently installed devices such as photodetachment-based techniques. Another way to determine beam distributions is a scintillator with charge-coupled device camera. First experiments have been performed to control the beam injection into the LEBT. The influence of beam parameters such as particle energy and space-charge compensation on the two-dimensional distribution and profiles will be presented.

Motions of charged particles in the Magnetosphere under the influence of a time-varying large scale convection electric field

NASA Technical Reports Server (NTRS)

Smith, P. H.; Bewtra, N. K.; Hoffman, R. A.

1979-01-01

The motions of charged particles under the influence of the geomagnetic and electric fields were quite complex in the region of the inner magnetosphere. The Volland-Stern type large scale convection electric field was used successfully to predict both the plasmapause location and particle enhancements determined from Explorer 45 measurements. A time dependence in this electric field was introduced based on the variation in Kp for actual magnetic storm conditions. The particle trajectories were computed as they change in this time-varying electric field. Several storm fronts of particles of different magnetic moments were allowed to be injected into the inner magnetosphere from L = 10 in the equatorial plane. The motions of these fronts are presented in a movie format.

A simulation study of interactions of space-shuttle generated electron beams with ambient plasma and neutral gas

NASA Technical Reports Server (NTRS)

Winglee, Robert M.

1991-01-01

The objective was to conduct large scale simulations of electron beams injected into space. The study of the active injection of electron beams from spacecraft is important, as it provides valuable insight into the plasma beam interactions and the development of current systems in the ionosphere. However, the beam injection itself is not simple, being constrained by the ability of the spacecraft to draw current from the ambient plasma. The generation of these return currents is dependent on several factors, including the density of the ambient plasma relative to the beam density, the presence of neutrals around the spacecraft, the configuration of the spacecraft, and the motion of the spacecraft through the plasma. Two dimensional (three velocity) particle simulations with collisional processes included are used to show how these different and often coupled processes can be used to enhance beam propagation from the spacecraft. To understand the radial expansion mechanism of an electron beam injected from a highly charged spacecraft, two dimensional particle-in-cell simulations were conducted for a high density electron beam injected parallel to magnetic fields from an isolated equipotential conductor into a cold background plasma. The simulations indicate that charge build-up at the beam stagnation point causes the beam to expand radially to the beam electron gyroradius.

CONJUGATED POLYMERS AND POLYELECTROLYTES IN SOLAR PHOTOCONVERSION, Final Technical Report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schanze, Kirk S

2014-08-05

This DOE-supported program investigated the fundamental properties of conjugated polyelectrolytes, with emphasis placed on studies of excited state energy transport, self-assembly into conjugated polyelectroyte (CPE) based films and colloids, and exciton transport and charge injection in CPE films constructed atop wide bandgap semiconductors. In the most recent grant period we have also extended efforts to examine the properties of low-bandgap donor-acceptor conjugated polyelectrolytes that feature strong visible light absorption and the ability to adsorb to metal-oxide interfaces.

The application of smart sensor techniques to a solid-state array multispectral sensor

NASA Technical Reports Server (NTRS)

Mcfadin, L. W.

1978-01-01

The solid-state array spectroradiometer (SAS) developed at JSC for remote sensing applications is a multispectral sensor which has no moving parts, is virtually maintenance-free, and has the ability to provide data which requires a minimum of processing. The instrument is based on the 42 x 342 element charge injection device (CID) detector. This system allows the combination of spectral scanning and across-track spatial scanning along with its associated digitization electronics into a single detector.

Capillaries for use in a multiplexed capillary electrophoresis system

DOEpatents

Yeung, Edward S.; Chang, Huan-Tsang; Fung, Eliza N.

1997-12-09

The invention provides a side-entry optical excitation geometry for use in a multiplexed capillary electrophoresis system. A charge-injection device is optically coupled to capillaries in the array such that the interior of a capillary is imaged onto only one pixel. In Sanger-type 4-label DNA sequencing reactions, nucleotide identification ("base calling") is improved by using two long-pass filters to split fluorescence emission into two emission channels. A binary poly(ethyleneoxide) matrix is used in the electrophoretic separations.

Capillaries for use in a multiplexed capillary electrophoresis system

DOEpatents

Yeung, E.S.; Chang, H.T.; Fung, E.N.

1997-12-09

The invention provides a side-entry optical excitation geometry for use in a multiplexed capillary electrophoresis system. A charge-injection device is optically coupled to capillaries in the array such that the interior of a capillary is imaged onto only one pixel. In Sanger-type 4-label DNA sequencing reactions, nucleotide identification (``base calling``) is improved by using two long-pass filters to split fluorescence emission into two emission channels. A binary poly(ethyleneoxide) matrix is used in the electrophoretic separations. 19 figs.

Dynamics of electronic transitions and frequency dependence of negative capacitance in semiconductor diodes under high forward bias

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bansal, Kanika; Datta, Shouvik; Henini, Mohamed

2014-09-22

We observed qualitatively dissimilar frequency dependence of negative capacitance under high charge injection in two sets of functionally different junction diodes: III-V based light emitting and Si-based non-light emitting diodes. Using an advanced approach based on bias activated differential capacitance, we developed a generalized understanding of negative capacitance phenomenon which can be extended to any diode based device structure. We explained the observations as the mutual competition of fast and slow electronic transition rates which are different in different devices. This study can be useful in understanding the interfacial effects in semiconductor heterostructures and may lead to superior device functionality.

Photocurrent enhancement mechanisms in bilayer nanofilm-based ultraviolet photodetectors made from ZnO and ZnS spherical nanoshells

PubMed Central

2014-01-01

Hollow-sphere bilayer nanofilm-based ultraviolet light photodetectors made from ZnO and ZnS spherical nanoshells show enhanced photocurrent, which are comparable to or even better than those of other semiconductor nanostructures with different shapes. In this work, the photocurrent enhancement mechanisms of these bilayer nanofilm-based ultraviolet light photodetectors are explained, which could be attributed to the strong light absorption based on the whispering gallery mode resonances, the separation of the photogenerated carriers through the internal electric field within the bilayer nanofilms, the hopping-like electrical transport, and the effective charge injection from Cr/Au contacts to the nanofilms. PMID:25136287

Interaction between dimethyldioctadecylammonium bromide-modified PLGA microspheres and hyaluronic acid

NASA Astrophysics Data System (ADS)

Mulia, Kamarza; Devi, Krisanti, Elsa

2017-02-01

In application of intravitreal injection, an extended drug delivery system is desired so that the frequency of injection to treat diabetic retinopathy may be reduced. Poly(lactic-co-glycolic acid) polymer (PLGA) was used to encapsulate a model drug in the form of microspheres. The zeta potential of dimethyldioctadecylammonium bromide (DDAB)-modified PLGA microspheres in water was proportional to the DDAB concentration used in the preparation step, up to +57.8 mV. The scanning electron microscope pictures and the zeta potential data (SEM) confirmed that the surface of the PLGA has been modified by the cationic surfactant and that electrostatic interaction between the positively charged microspheres and the negatively charged vitreous were present.

Performance of a supercharged direct-injection stratified-charge rotary combustion engine

NASA Technical Reports Server (NTRS)

Bartrand, Timothy A.; Willis, Edward A.

1990-01-01

A zero-dimensional thermodynamic performance computer model for direct-injection stratified-charge rotary combustion engines was modified and run for a single rotor supercharged engine. Operating conditions for the computer runs were a single boost pressure and a matrix of speeds, loads and engine materials. A representative engine map is presented showing the predicted range of efficient operation. After discussion of the engine map, a number of engine features are analyzed individually. These features are: heat transfer and the influence insulating materials have on engine performance and exhaust energy; intake manifold pressure oscillations and interactions with the combustion chamber; and performance losses and seal friction. Finally, code running times and convergence data are presented.

The study on injection parameters of selected alternative fuels used in diesel engines

NASA Astrophysics Data System (ADS)

Balawender, K.; Kuszewski, H.; Lejda, K.; Lew, K.

2016-09-01

The paper presents selected results concerning fuel charging and spraying process for selected alternative fuels, including regular diesel fuel, rape oil, FAME, blends of these fuels in various proportions, and blends of rape oil with diesel fuel. Examination of the process included the fuel charge measurements. To this end, a set-up for examination of Common Rail-type injection systems was used constructed on the basis of Bosch EPS-815 test bench, from which the high-pressure pump drive system was adopted. For tests concerning the spraying process, a visualisation chamber with constant volume was utilised. The fuel spray development was registered with the use of VisioScope (AVL).

Performance and efficiency evaluation and heat release study of a direct-injection stratified-charge rotary engine

NASA Technical Reports Server (NTRS)

Nguyen, H. L.; Addy, H. E.; Bond, T. H.; Lee, C. M.; Chun, K. S.

1987-01-01

A computer simulation which models engine performance of the Direct Injection Stratified Charge (DISC) rotary engines was used to study the effect of variations in engine design and operating parameters on engine performance and efficiency of an Outboard Marine Corporation (OMC) experimental rotary combustion engine. Engine pressure data were used in a heat release analysis to study the effects of heat transfer, leakage, and crevice flows. Predicted engine data were compared with experimental test data over a range of engine speeds and loads. An examination of methods to improve the performance of the rotary engine using advanced heat engine concepts such as faster combustion, reduced leakage, and turbocharging is also presented.

Investigation of field induced trapping on floating gates

NASA Technical Reports Server (NTRS)

Gosney, W. M.

1975-01-01

The development of a technology for building electrically alterable read only memories (EAROMs) or reprogrammable read only memories (RPROMs) using a single level metal gate p channel MOS process with all conventional processing steps is outlined. Nonvolatile storage of data is achieved by the use of charged floating gate electrodes. The floating gates are charged by avalanche injection of hot electrodes through gate oxide, and discharged by avalanche injection of hot holes through gate oxide. Three extra diffusion and patterning steps are all that is required to convert a standard p channel MOS process into a nonvolatile memory process. For identification, this nonvolatile memory technology was given the descriptive acronym DIFMOS which stands for Dual Injector, Floating gate MOS.

Fuel injection of coal slurry using vortex nozzles and valves

DOEpatents

Holmes, Allen B.

1989-01-01

Injection of atomized coal slurry fuel into an engine combustion chamber is achieved at relatively low pressures by means of a vortex swirl nozzle. The outlet opening of the vortex nozzle is considerably larger than conventional nozzle outlets, thereby eliminating major sources of failure due to clogging by contaminants in the fuel. Control fluid, such as air, may be used to impart vorticity to the slurry and/or purge the nozzle of contaminants during the times between measured slurry charges. The measured slurry charges may be produced by a diaphragm pump or by vortex valves controlled by a separate control fluid. Fluidic circuitry, employing vortex valves to alternatively block and pass cool slurry fuel flow, is disclosed.

Charge generation layers for solution processed tandem organic light emitting diodes with regular device architecture.

PubMed

Höfle, Stefan; Bernhard, Christoph; Bruns, Michael; Kübel, Christian; Scherer, Torsten; Lemmer, Uli; Colsmann, Alexander

2015-04-22

Tandem organic light emitting diodes (OLEDs) utilizing fluorescent polymers in both sub-OLEDs and a regular device architecture were fabricated from solution, and their structure and performance characterized. The charge carrier generation layer comprised a zinc oxide layer, modified by a polyethylenimine interface dipole, for electron injection and either MoO3, WO3, or VOx for hole injection into the adjacent sub-OLEDs. ToF-SIMS investigations and STEM-EDX mapping verified the distinct functional layers throughout the layer stack. At a given device current density, the current efficiencies of both sub-OLEDs add up to a maximum of 25 cd/A, indicating a properly working tandem OLED.

Tuberculosis knowledge among injecting drug users visiting syringe exchange programme in Tallinn, Estonia.

PubMed

Rüütel, Kristi; Parker, R David; Sobolev, Igor; Loit, Helle-Mai

2012-12-01

The purpose of the current study was to describe tuberculosis (TB) knowledge, beliefs, and experience with TB services among injecting drug users. Participants for this anonymous, cross-sectional study were recruited from a community based syringe exchange programme in Tallinn, Estonia. A structured questionnaire was completed and included information on socio-demographics, health history, drug use, and knowledge about TB and HIV. The study included 407 people (79% male, mean age 27.9 years, mean injection drug use 9.4 years). 32.9% of participants reported HIV infection and 1.7% lifetime history of TB. 26.4% participants (n=106) reported symptoms suggestive of TB. 93% of participants recognized correctly that TB is air-borne infection and 91% that HIV is a risk factor for TB. Only 40% of the participants knew that TB diagnostics and treatment in Estonia are free of charge for everybody and 58% reported they knew where to get health care services in case they suspected that they had TB. TB transmission and treatment adherence knowledge was better among those in contact with either health care or harm reduction services, e.g the community based syringe exchange programme. Similar to HIV services, TB prevention and education should be integrated into harm reduction and drug treatment programmes to facilitate early diagnosis and treatment of TB among injecting drug users.

Injectant mole-fraction imaging in compressible mixing flows using planar laser-induced iodine fluorescence

NASA Technical Reports Server (NTRS)

Hartfield, Roy J., Jr.; Abbitt, John D., III; Mcdaniel, James C.

1989-01-01

A technique is described for imaging the injectant mole-fraction distribution in nonreacting compressible mixing flow fields. Planar fluorescence from iodine, seeded into air, is induced by a broadband argon-ion laser and collected using an intensified charge-injection-device array camera. The technique eliminates the thermodynamic dependence of the iodine fluorescence in the compressible flow field by taking the ratio of two images collected with identical thermodynamic flow conditions but different iodine seeding conditions.

On the critical charge required for positive leader inception in long air gaps

NASA Astrophysics Data System (ADS)

Liu, Lipeng; Becerra, Marley

2018-01-01

The amount of the electric charge injected by the streamer corona bursts during the stage of leader inception determines the energy deposited to thermalize the corona stem into a leader segment. This paper is aimed at investigating the critical charge required for positive leader inception in air by using a thermo-hydrodynamic model with a detailed kinetic scheme. In order to simplify the analysis and to speed up the simulation, a reduced kinetic scheme for air is proposed. Numerical comparisons show that the reduced scheme can obtain almost the same results as the previous comprehensive kinetic scheme but with only half of the number of species and reactions. The thermo-hydrodynamic model with the reduced kinetics is then used to solve the radial dynamics of a single stem heated by current pulses typical of streamer corona bursts. The critical charge necessary for the direct transition of a first streamer corona into a leader under electrodes with large curvature radius is estimated between 0.08 and 0.5 µC per stem. Furthermore, the simulation shows that the gas heating of corona stem formed from electrodes with small curvature radius is mainly determined by the total accumulated charge injected by previous streamer corona bursts and the length of the dark periods in between the current pulses. The shape and the number of the corona current pulses in the discharge also play a role and their effects are discussed. It is suggested that the transition into a leader is triggered when a secondary streamer burst is initiated after the gas temperature is increased by the heating of previous streamers to about 1200 K. In addition, it is found that the heating produced by the charge injected by previous streamer corona bursts can be neglected if the dark period to the next burst is larger than few hundreds of µs for a corona stem with moderate initial stem radius. This indicates that the critical charge criterion obtained from laboratory experiments does not hold to evaluate the inception of positive leaders under conditions when long dark periods are present.

Microneedle-mediated transcutaneous immunization with plasmid DNA coated on cationic PLGA nanoparticles

PubMed Central

Kumar, Amit; Wonganan, Piyanuch; Sandoval, Michael A.; Li, Xinran; Zhu, Saijie; Cui, Zhengrong

2012-01-01

Previously, it was shown that microneedle-mediated transcutaneous immunization with plasmid DNA can potentially induce a stronger immune response than intramuscular injection of the same plasmid DNA. In the present study, we showed that the immune responses induced by transcutaneous immunization by applying plasmid DNA onto a skin area pretreated with solid microneedles were significantly enhanced by coating the plasmid DNA on the surface of cationic nanoparticles. In addition, the net surface charge of the DNA-coated nanoparticles significantly affected their in vitro skin permeation and their ability to induce immune responses in vivo. Transcutaneous immunization with plasmid DNA-coated net positively charged anoparticles elicited a stronger immune response than with plasmid DNA-coated net negatively charged nanoparticles or by intramuscular immunization with plasmid DNA alone. Transcutaneous immunization with plasmid DNA-coated net positively charged nanoparticles induced comparable immune responses as intramuscular injection of them, but transcutaneous immunization was able to induce specific mucosal immunity and a more balanced T helper type 1 and type 2 response. The ability of the net positively charged DNA-coated nanoparticles to induce a strong immune response through microneedle-mediated transcutaneous immunization may be attributed to their ability to increase the expression of the antigen gene encoded by the plasmid and to more effectively stimulate the maturation of antigen-presenting cells. PMID:22921518

Space charge dynamics Of CF4 fluorinated LDPE samples from different fluorination conditions and their DC conductivities

NASA Astrophysics Data System (ADS)

Liu, Ning; Li, Ziyun; Chen, George; Chen, Qiang; Li, Shengtao

2017-07-01

Taking advantage of plasma technology using mixing gas CF4/H2, a fluorination process was performed on LDPE samples in the present paper. Different exposure times and discharge voltage levels were applied to produce four different types of samples. It has been found that after fluorination, space charge injection is obviously suppressed. And with longer fluorination times and higher discharge voltage, injected homocharges are reduced. By employing x-ray photoelectron spectroscopy, new chemical groups of C-F bindings are confirmed to be introduced by fluorination process of the plasma treatment. The charge suppression effect can be explained as: surface traps introduced by fluorination will reduce the interface field at both electrodes. Moreover, for fluorinated samples, heterocharge emerges obviously under 30 kV \\text{m}{{\\text{m}}-1} , which are considered as charges ionized from degradation products of etching and/or lower weight molecular specifies. Through the conductivity measurements also performed at 30 kV \\text{m}{{\\text{m}}-1} , it is found that, for the fluorinated samples with the better charge blocking effect, the conductivity is lowered. However, the conductivity of the fluorinated sample with the lightest degree of fluorination is found to be higher than that of normal samples.

Preliminary test results of electrical charged particle generator for application to fog dispersal

NASA Technical Reports Server (NTRS)

Frost, W.

1982-01-01

A charged particle generator for use in fog dispersal applications was built and preliminary tests were carried out. The parameter used as a measure of performance was the current measured with a needle probe positioned in the charged jet connected to ground through an ammeter. The needle was movable and allowed the current profile throughout the jet to be determined. The measured current is referred to as the current output. The major independent parameters were liquid water injection rate, plenum pressure, and corona voltage. Optimum current output was achieved at the approximate pressure of 30 psig, corona voltage of 5600 volts, and liquid water injection rate of 6 cc/min. The results of the test with the prototype charged particle generator clearly demonstrate that a current on the order of 20 microamperes can be routinely achieved with the system. This measurement of current does not necessarily represent the total issuing from the nozzle current which is expected to be larger. From these results, confidence was established that a charged particle generator which will operate continuously and consistently can be designed, constructed, and operated. Further work is required, however, to better understand the physical mechanisms involved and to optimize the system for fog dispersal application.

Fast Neural Solution Of A Nonlinear Wave Equation

NASA Technical Reports Server (NTRS)

Barhen, Jacob; Toomarian, Nikzad

1996-01-01

Neural algorithm for simulation of class of nonlinear wave phenomena devised. Numerically solves special one-dimensional case of Korteweg-deVries equation. Intended to be executed rapidly by neural network implemented as charge-coupled-device/charge-injection device, very-large-scale integrated-circuit analog data processor of type described in "CCD/CID Processors Would Offer Greater Precision" (NPO-18972).

Demonstration of charge breeding in a compact room temperature electron beam ion trap

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vorobjev, G.; Sokolov, A.; Herfurth, F.

2012-05-15

For the first time, a small room-temperature electron beam ion trap (EBIT), operated with permanent magnets, was successfully used for charge breeding experiments. The relatively low magnetic field of this EBIT does not contribute to the capture of the ions; single-charged ions are only caught by the space charge potential of the electron beam. An over-barrier injection method was used to fill the EBIT's electrostatic trap with externally produced, single-charged potassium ions. Charge states as high as K{sup 19+} were reached after about a 3 s breeding time. The capture and breeding efficiencies up to 0.016(4)% for K{sup 17+} havemore » been measured.« less

Charge-Retraction Time-of-Flight Measurement for Organic Charge Transport Materials

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wallace, J.U.; Young, R.H.; Tang, C.W.

This describes an all-electrical technique, charge-retraction time-of-flight (CR-TOF), to measure charge carrier mobility through an organic layer. Carriers are injected and accumulated at a blocking interface, then retracted. The retraction current transient is nearly indistinguishable from a traditional time-of-flight photocurrent. The CR-TOF technique is validated by measurement of the hole mobility of two well-known compounds, 4,4',4"-tris[N-(3-methylphenyl)-N-phenylamino]triphenylamine and 4,4'-bis[N-1-napthyl)-N-phenylamino]biphenyl, utilizing 1,3,5-tris(N-phenylbenzimidazol-2-yl)-benzene as a hole-blocking layer.

Dielectric particle injector for material processing

NASA Technical Reports Server (NTRS)

Leung, Philip L. (Inventor)

1992-01-01

A device for use as an electrostatic particle or droplet injector is disclosed which is capable of injecting dielectric particles or droplets. The device operates by first charging the dielectric particles or droplets using ultraviolet light induced photoelectrons from a low work function material plate supporting the dielectric particles or droplets, and then ejecting the charged particles or droplets from the plate by utilizing an electrostatic force. The ejected particles or droplets are mostly negatively charged in the preferred embodiment; however, in an alternate embodiment, an ion source is used instead of ultraviolet light to eject positively charged dielectric particles or droplets.

Fuel mixture stratification as a method for improving homogeneous charge compression ignition engine operation

DOEpatents

Dec, John E [Livermore, CA; Sjoberg, Carl-Magnus G [Livermore, CA

2006-10-31

A method for slowing the heat-release rate in homogeneous charge compression ignition ("HCCI") engines that allows operation without excessive knock at higher engine loads than are possible with conventional HCCI. This method comprises injecting a fuel charge in a manner that creates a stratified fuel charge in the engine cylinder to provide a range of fuel concentrations in the in-cylinder gases (typically with enough oxygen for complete combustion) using a fuel with two-stage ignition fuel having appropriate cool-flame chemistry so that regions of different fuel concentrations autoignite sequentially.

Numerical Studies of High-Intensity Injection Painting for Project X

DOE Office of Scientific and Technical Information (OSTI.GOV)

Drozhdin, A.I.; Vorobiev, L.G.; Johnson, D.E.

Injection phase space painting enables the mitigation of space charge and stability issues, and will be indispensable for the Project-X at Fermilab [1], delivering high-intensity proton beams to HEP experiments. Numerical simulations of multi-turn phase space painting have been performed for the FNAL Recycler Ring, including a self-consistent space charge model. The goal of our studies was to study the injection painting with inclusion of 3D space charge, using the ORBIT tracking code. In a current scenario the painting lasts for 110 turns, twice faster, than we considered in this paper. The optimal wave-forms for painting kickers, which ensure themore » flatter phase distributions, should be found. So far we used a simplified model for painting kicker strength (implemented as the 'ideal bump' in ORBIT). We will include a more realistic field map for the chicane magnets. Additional stripping simulations will be combined. We developed a block for longitudinal painting, which works with arbitrary notches in incoming micro-bunch buckets. The appropriate choice of the amplitude of the second harmonic of RF field will help to flatten the RF-bucket contours, as was demonstrated in 1D simulations. Non-linear lattice issue will be also addressed.« less

A Power-Efficient Wireless Capacitor Charging System Through an Inductive Link

PubMed Central

Lee, Hyung-Min; Ghovanloo, Maysam

2014-01-01

A power-efficient wireless capacitor charging system for inductively powered applications has been presented. A bank of capacitors can be directly charged from an ac source by generating a current through a series charge injection capacitor and a capacitor charger circuit. The fixed charging current reduces energy loss in switches, while maximizing the charging efficiency. An adaptive capacitor tuner compensates for the resonant capacitance variations during charging to keep the amplitude of the ac input voltage at its peak. We have fabricated the capacitor charging system prototype in a 0.35-μm 4-metal 2-poly standard CMOS process in 2.1 mm2 of chip area. It can charge four pairs of capacitors sequentially. While receiving 2.7-V peak ac input through a 2-MHz inductive link, the capacitor charging system can charge each pair of 1 μF capacitors up to ±2 V in 420 μs, achieving a high measured charging efficiency of 82%. PMID:24678284

A Power-Efficient Wireless Capacitor Charging System Through an Inductive Link.

PubMed

Lee, Hyung-Min; Ghovanloo, Maysam

2013-10-01

A power-efficient wireless capacitor charging system for inductively powered applications has been presented. A bank of capacitors can be directly charged from an ac source by generating a current through a series charge injection capacitor and a capacitor charger circuit. The fixed charging current reduces energy loss in switches, while maximizing the charging efficiency. An adaptive capacitor tuner compensates for the resonant capacitance variations during charging to keep the amplitude of the ac input voltage at its peak. We have fabricated the capacitor charging system prototype in a 0.35- μ m 4-metal 2-poly standard CMOS process in 2.1 mm 2 of chip area. It can charge four pairs of capacitors sequentially. While receiving 2.7-V peak ac input through a 2-MHz inductive link, the capacitor charging system can charge each pair of 1 μ F capacitors up to ±2 V in 420 μ s, achieving a high measured charging efficiency of 82%.

Synthesis of Stable Interfaces on SnO2 Surfaces for Charge-Transfer Applications

NASA Astrophysics Data System (ADS)

Benson, Michelle C.

The commercial market for solar harvesting devices as an alternative energy source requires them to be both low-cost and efficient to replace or reduce the dependence on fossil fuel burning. Over the last few decades there has been promising efforts towards improving solar devices by using abundant and non-toxic metal oxide nanomaterials. One particular metal oxide of interest has been SnO2 due to its high electron mobility, wide-band gap, and aqueous stability. However SnO2 based solar cells have yet to reach efficiency values of other metal oxides, like TiO2. The advancement of SnO2 based devices is dependent on many factors, including improved methods of surface functionalization that can yield stable interfaces. This work explores the use of a versatile functionalization method through the use of the Cu(I)-catalyzed azide-alkyne cycloaddition (CuAAC) reaction. The CuAAC reaction is capable of producing electrochemically, photochemically, and electrocatalytically active surfaces on a variety of SnO2 materials. The resulting charge-transfer characteristics were investigated as well as an emphasis on understanding the stability of the resulting molecular linkage. We determined the CuAAC reaction is able to proceed through both azide-modified and alkyne-modified surfaces. The resulting charge-transfer properties showed that the molecular tether was capable of supporting charge separation at the interface. We also investigated the enhancement of electron injection upon the introduction of an ultra-thin ZrO2 coating on SnO2. Several complexes were used to fully understand the charge-transfer capabilities, including model systems of ferrocene and a ruthenium coordination complex, a ruthenium mononuclear water oxidation catalyst, and a commercial ruthenium based dye.

Photo-reactive charge trapping memory based on lanthanide complex.

PubMed

Zhuang, Jiaqing; Lo, Wai-Sum; Zhou, Li; Sun, Qi-Jun; Chan, Chi-Fai; Zhou, Ye; Han, Su-Ting; Yan, Yan; Wong, Wing-Tak; Wong, Ka-Leung; Roy, V A L

2015-10-09

Traditional utilization of photo-induced excitons is popularly but restricted in the fields of photovoltaic devices as well as photodetectors, and efforts on broadening its function have always been attempted. However, rare reports are available on organic field effect transistor (OFET) memory employing photo-induced charges. Here, we demonstrate an OFET memory containing a novel organic lanthanide complex Eu(tta)3ppta (Eu(tta)3 = Europium(III) thenoyltrifluoroacetonate, ppta = 2-phenyl-4,6-bis(pyrazol-1-yl)-1,3,5-triazine), in which the photo-induced charges can be successfully trapped and detrapped. The luminescent complex emits intense red emission upon ultraviolet (UV) light excitation and serves as a trapping element of holes injected from the pentacene semiconductor layer. Memory window can be significantly enlarged by light-assisted programming and erasing procedures, during which the photo-induced excitons in the semiconductor layer are separated by voltage bias. The enhancement of memory window is attributed to the increasing number of photo-induced excitons by the UV light. The charges are stored in this luminescent complex for at least 10(4) s after withdrawing voltage bias. The present study on photo-assisted novel memory may motivate the research on a new type of light tunable charge trapping photo-reactive memory devices.

Photo-reactive charge trapping memory based on lanthanide complex

NASA Astrophysics Data System (ADS)

Zhuang, Jiaqing; Lo, Wai-Sum; Zhou, Li; Sun, Qi-Jun; Chan, Chi-Fai; Zhou, Ye; Han, Su-Ting; Yan, Yan; Wong, Wing-Tak; Wong, Ka-Leung; Roy, V. A. L.

2015-10-01

Traditional utilization of photo-induced excitons is popularly but restricted in the fields of photovoltaic devices as well as photodetectors, and efforts on broadening its function have always been attempted. However, rare reports are available on organic field effect transistor (OFET) memory employing photo-induced charges. Here, we demonstrate an OFET memory containing a novel organic lanthanide complex Eu(tta)3ppta (Eu(tta)3 = Europium(III) thenoyltrifluoroacetonate, ppta = 2-phenyl-4,6-bis(pyrazol-1-yl)-1,3,5-triazine), in which the photo-induced charges can be successfully trapped and detrapped. The luminescent complex emits intense red emission upon ultraviolet (UV) light excitation and serves as a trapping element of holes injected from the pentacene semiconductor layer. Memory window can be significantly enlarged by light-assisted programming and erasing procedures, during which the photo-induced excitons in the semiconductor layer are separated by voltage bias. The enhancement of memory window is attributed to the increasing number of photo-induced excitons by the UV light. The charges are stored in this luminescent complex for at least 104 s after withdrawing voltage bias. The present study on photo-assisted novel memory may motivate the research on a new type of light tunable charge trapping photo-reactive memory devices.

Active charge trapping control in dielectrics under ionizing radiation

NASA Astrophysics Data System (ADS)

Dominguez-Pumar, M.; Bheesayagari, C.; Gorreta, S.; Pons-Nin, J.

2017-12-01

Charge trapping is is a design and reliability factor in plasma sensors. Examples can be found in microchannel plate detectors in plasma analyzers, where multiple layers have been devised to ensure filled trapped electrons for enhanced secondary emission [1]. Charge trap mapping is used to recover distortion in telescope CCDs [2]. Specific technologies are designed to mitigate the effect of ionizing radiation in monolithic Active Pixel Sensors [3]. We report in this paper a control loop designed to control charge in Metal-Oxide-Semiconductor capacitors. We find that the net trapped charge in the device can be set within some limits to arbitrary values that can be changed with time. The control loop periodically senses the net trapped charge by detecting shifts in the capacitance vs voltage characteristic, and generates adequate waveform sequences to keep the trapped charge at the desired level [4]. The waveforms continuously applied have been chosen to provide different levels of charge injection into the dielectric. The control generates the adequate average charge injection to reach and maintain the desired level of trapped charge, compensating external disturbances. We also report that this control can compensate charge generated by ionizing radiation. Experiments will be shown in which this compensation is obtained with X-rays and gamma radiation. The presented results open the possibility of applying active compensation techniques for the first time in a wide number of devices such as radiation sensors, MOS transistors and other devices. The continuous drive towards integration may allow the implementation of this type of controls in devices needing to reject external disturbances, or needing to optimize their response to radiation or ion fluxes. References: [1] patent US 2009/0212680 A1. [2] A&A 534, A20 (2011). [3] Hemperek, Nucl. Instr. and Meth. in Phys. Res. Sect. A.796, pp 8-12, 2015. [4] Dominguez, IEEE Trans. Ind. Electr, 64 (4), 3023-3029, 2017.

Source Determination for Substorm-Related Ion Injections

NASA Technical Reports Server (NTRS)

Strangeway, Robert J.; Evans, David (Technical Monitor)

2001-01-01

The grant supported an effort to restore and analyze data from the Spacecraft Charging at High Altitude (SCATHA) spacecraft. This spacecraft, which was originally an Air Force mission, was launched into a near geo-synchronous orbit in early 1979 to, investigate the inner magnetosphere at altitudes where it was known that spacecraft can undergo significant charging events. SCATHA included an ion composition experiment (designated SC8) and in many ways was a precursor to other missions, such as the AMPTE Charge Composition Explorer.

Scintillator-fiber charged-particle track-imaging detector

NASA Technical Reports Server (NTRS)

Binns, W. R.; Israel, M. H.; Klarmann, J.

1983-01-01

A scintillator-fiber charged-particle track-imaging detector has been developed using a bundle of square cross-section plastic scintillator fiber optics, proximity focused onto an image intensified Charge Injection Device (CID) camera. Detector to beams of 15 MeV protons and relativistic Neon, Manganese, and Gold nuclei have been exposed and images of their tracks are obtained. This paper presents details of the detector technique, properties of the tracks obtained, and range measurements of 15 MeV protons stopping in the fiber bundle.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dearling, Jason L. J.; Smith, Suzanne V.; Paterson, Brett M.

The development of biomolecules as imaging probes requires radiolabeling methods that do not significantly influence their biodistribution. Sarcophagine (Sar) chelators form extremely stable complexes with copper, and are therefore a promising option for labeling proteins with ⁶⁴Cu. However, initial studies using the first-generation sarcophagine bifunctional chelator SarAr to label the engineered antibody fragment ch14.18-ΔC H2 (MW 120 kDa) with ⁶⁴Cu showed high tracer retention in the kidneys,(>38% injected dose per gram (ID/g) 48 h post-injection), presumably because the high local positive charge on the Cu II-SarAr moiety resulted in increased binding of the labeled protein to the negatively charged basalmore » cells of the glomerulus. To test this hypothesis, ch14.18-ΔC H2 was conjugated with a series of Sar derivatives of decreasing positive charge and three commonly used macrocyclic polyaza polycarboxylate (PAC) BFCs. The immunoconjugates were labeled with ⁶⁴Cu and injected into mice, and PET/CT images were obtained at 24 and 48 h post injection (p.i.). At 48 h p.i., ex vivo biodistribution was carried out. In addition, to demonstrate the potential of metastasis detection using ⁶⁴Cu-labeled ch14.18-ΔC H2, a preclinical imaging study of intrahepatic neuroblastoma tumors was performed carried out. Reducing the positive charge on the Sar chelators decreased kidney uptake of Cu-labeled ch14.18-ΔC H2 by more than 6-fold, from >45 ID/g to <6% ID/g, while the uptake in most other tissues, including liver, was relatively unchanged. However, despite this dramatic decrease, the renal uptake of the PAC BFCs was generally lower than that of the Sar derivatives, as was the liver uptake. Uptake of ⁶⁴Cu-labeled ch14.18-ΔC H2 in neuroblastoma hepatic metastases was detected using PET.« less

Double heterojunction nanowire photocatalysts for hydrogen generation.

PubMed

Tongying, P; Vietmeyer, F; Aleksiuk, D; Ferraudi, G J; Krylova, G; Kuno, M

2014-04-21

Charge separation and charge transfer across interfaces are key aspects in the design of efficient photocatalysts for solar energy conversion. In this study, we investigate the hydrogen generating capabilities and underlying photophysics of nanostructured photocatalysts based on CdSe nanowires (NWs). Systems studied include CdSe, CdSe/CdS core/shell nanowires and their Pt nanoparticle-decorated counterparts. Femtosecond transient differential absorption measurements reveal how semiconductor/semiconductor and metal/semiconductor heterojunctions affect the charge separation and hydrogen generation efficiencies of these hybrid photocatalysts. In turn, we unravel the role of surface passivation, charge separation at semiconductor interfaces and charge transfer to metal co-catalysts in determining photocatalytic H2 generation efficiencies. This allows us to rationalize why Pt nanoparticle decorated CdSe/CdS NWs, a double heterojunction system, performs best with H2 generation rates of ∼434.29 ± 27.40 μmol h(-1) g(-1) under UV/Visible irradiation. In particular, we conclude that the CdS shell of this double heterojunction system serves two purposes. The first is to passivate CdSe NW surface defects, leading to long-lived charges at the CdSe/CdS interface capable of carrying out reduction chemistries. Upon photoexcitation, we also find that CdS selectively injects charges into Pt NPs, enabling simultaneous reduction chemistries at the Pt NP/solvent interface. Pt nanoparticle decorated CdSe/CdS NWs thus enable reduction chemistries at not one, but rather two interfaces, taking advantage of each junction's optimal catalytic activities.

TARGET/CRYOCHIL - THERMODYNAMIC ANALYSIS AND SUBSCALE MODELING OF SPACE-BASED ORBIT TRANSFER VEHICLE CRYOGENIC PROPELLANT RESUPPLY

NASA Technical Reports Server (NTRS)

Defelice, D. M.

1994-01-01

The resupply of the cryogenic propellants is an enabling technology for space-based transfer vehicles. As part of NASA Lewis's ongoing efforts in micro-gravity fluid management, thermodynamic analysis and subscale modeling techniques have been developed to support an on-orbit test bed for cryogenic fluid management technologies. These efforts have been incorporated into two FORTRAN programs, TARGET and CRYOCHIL. The TARGET code is used to determine the maximum temperature at which the filling of a given tank can be initiated and subsequently filled to a specified pressure and fill level without venting. The main process is the transfer of the energy stored in the thermal mass of the tank walls into the inflowing liquid. This process is modeled by examining the end state of the no-vent fill process. This state is assumed to be at thermal equilibrium between the tank and the fluid which is well mixed and saturated at the tank pressure. No specific assumptions are made as to the processes or the intermediate thermodynamic states during the filling. It is only assumed that the maximum tank pressure occurs at the final state. This assumption implies that, during the initial phases of the filling, the injected liquid must pass through the bulk vapor in such a way that it absorbs a sufficient amount of its superheat so that moderate tank pressures can be maintained. It is believed that this is an achievable design goal for liquid injection systems. TARGET can be run with any fluid for which the user has a properties data base. Currently it will only run for hydrogen, oxygen, and nitrogen since pressure-enthalpy data sets have been included for these fluids only. CRYOCHIL's primary function is to predict the optimum liquid charge to be injected for each of a series of charge-hold-vent chilldown cycles. This information can then be used with specified mass flow rates and valve response times to control a liquid injection system for tank chilldown operations. This will insure that the operations proceed quickly and efficiently. These programs are written in FORTRAN for batch execution on IBM 370 class mainframe computers. It requires 360K of RAM for execution. The standard distribution medium for this program is a 1600 BPI 9track magnetic tape in EBCDIC format. TARGET/CRYOCHIL was developed in 1988.

Light-emitting diodes based on solution-processed nontoxic quantum dots: oxides as carrier-transport layers and introducing molybdenum oxide nanoparticles as a hole-inject layer.

PubMed

Bhaumik, Saikat; Pal, Amlan J

2014-07-23

We report fabrication and characterization of solution-processed quantum dot light-emitting diodes (QDLEDs) based on a layer of nontoxic and Earth-abundant zinc-diffused silver indium disulfide (AIZS) nanoparticles as an emitting material. In the QDLEDs fabricated on indium tin oxide (ITO)-coated glass substrates, we use layers of oxides, such as graphene oxide (GO) and zinc oxide (ZnO) nanoparticles as a hole- and electron-transport layer, respectively. In addition, we introduce a layer of MoO3 nanoparticles as a hole-inject one. We report a comparison of the characteristics of different device architectures. We show that an inverted device architecture, ITO/ZnO/AIZS/GO/MoO3/Al, yields a higher electroluminescence (EL) emission, compared to direct ones, for three reasons: (1) the GO/MoO3 layers introduce barriers for electrons to reach the Al electrode, and, similarly, the ZnO layers acts as a barrier for holes to travel to the ITO electrode; (2) the introduction of a layer of MoO3 nanoparticles as a hole-inject layer reduces the barrier height for holes and thereby balances charge injection in the inverted structure; and (3) the wide-bandgap zinc oxide next to the ITO electrode does not absorb the EL emission during its exit from the device. In the QDLEDs with oxides as carrier inject and transport layers, the EL spectrum resembles the photoluminescence emission of the emitting material (AIZS), implying that excitons are formed in the quaternary nanocrystals and decay radiatively.

Optimal Coordinated EV Charging with Reactive Power Support in Constrained Distribution Grids

DOE Office of Scientific and Technical Information (OSTI.GOV)

Paudyal, Sumit; Ceylan, Oğuzhan; Bhattarai, Bishnu P.

Electric vehicle (EV) charging/discharging can take place in any P-Q quadrants, which means EVs could support reactive power to the grid while charging the battery. In controlled charging schemes, distribution system operator (DSO) coordinates with the charging of EV fleets to ensure grid’s operating constraints are not violated. In fact, this refers to DSO setting upper bounds on power limits for EV charging. In this work, we demonstrate that if EVs inject reactive power into the grid while charging, DSO could issue higher upper bounds on the active power limits for the EVs for the same set of grid constraints.more » We demonstrate the concept in an 33-node test feeder with 1,500 EVs. Case studies show that in constrained distribution grids in coordinated charging, average costs of EV charging could be reduced if the charging takes place in the fourth P-Q quadrant compared to charging with unity power factor.« less

Studies on ocular and parenteral application potentials of azithromycin- loaded anionic, cationic and neutral-charged emulsions.

PubMed

Tamilvanan, Shunmugaperumal; Khanum, Ramona; Senthilkumar, Sudalimuthu Ramachandran; Muthuraman, Marimuthu; Rajasekharan, Thenrajan

2013-10-01

Ocular and parenteral application potentials of azithromycin-containing, non-phospholipid-based cationic nanosized emulsion in comparison to the phospholipid-based anionic and neutral-charged nanosized emulsions were investigated. Various physical, chemical, nonclinical toxicity and antimicrobial activity studies (mean droplet diameter, surface charge, creaming index, entrapment efficiency, accelerated, long-term and freeze-thaw cycling stabilities, TLC study, modified hen's egg chorioallantoic membrane (HET-CAM) test, in vitro hemolysis test, in vitro and in vivo myotoxicity, and in vitro antimicrobial activity) were conducted for assessing the potentials of these three types of emulsions. Following autoclave sterilization, all of these emulsions exhibited a nanometer range mean particle diameter (200 ± 29 to 434 ± 13 nm). While the anionic and cationic emulsions did show high negative (-34.2 ± 1.23 mV) and positive zeta potential (42.6 ± 1.45 mV) values, the neutral-charged emulsion did not. Even with 5 freeze-thaw cycles, the cationic emulsion remained stable whereas other two emulsions underwent phase-separation. The hen's egg chorioallantoic membrane test revealed an irritation score value that was higher for the anionic emulsion than for cationic or neutral-charged emulsion. A significantly higher % hemolysis value was also noticed for the anionic emulsion when compared to the % hemolysis value of cationic emulsion (ANOVA, P ‹ 0.05). However, all of the emulsions showed a lesser intracellular creatine kinase (CK) release/plasma CK level in comparison to the positive control (phenytoin) indicating their lesser myotoxicity at the injection site . When compared to anionic and neutral-charged emulsions, the possible controlled drug release from cationic emulsion delayed the in vitro antimicrobial action against H.influenzae and S.pneumoniae.

Ligand-Asymmetric Janus Quantum Dots for Efficient Blue-Quantum Dot Light-Emitting Diodes.

PubMed

Cho, Ikjun; Jung, Heeyoung; Jeong, Byeong Guk; Hahm, Donghyo; Chang, Jun Hyuk; Lee, Taesoo; Char, Kookheon; Lee, Doh C; Lim, Jaehoon; Lee, Changhee; Cho, Jinhan; Bae, Wan Ki

2018-06-19

We present ligand-asymmetric Janus quantum dots (QDs) to improve the device performance of quantum dot light-emitting diodes (QLEDs). Specifically, we devise blue QLEDs incorporating blue QDs with asymmetrically modified ligands, in which the bottom ligand of QDs in contact with ZnO electron-transport layer serves as a robust adhesive layer and an effective electron-blocking layer and the top ligand ensures uniform deposition of organic hole transport layers with enhanced hole injection properties. Suppressed electron overflow by the bottom ligand and stimulated hole injection enabled by the top ligand contribute synergistically to boost the balance of charge injection in blue QDs and therefore the device performance of blue QLEDs. As an ultimate achievement, the blue QLED adopting ligand-asymmetric QDs displays 2-fold enhancement in peak external quantum efficiency (EQE = 3.23%) compared to the case of QDs with native ligands (oleic acid) (peak EQE = 1.49%). The present study demonstrates an integrated strategy to control over the charge injection properties into QDs via ligand engineering that enables enhancement of the device performance of blue QLEDs and thus promises successful realization of white light-emitting devices using QDs.

Electromechanical response of amorphous LaAlO{sub 3} thin film probed by scanning probe microscopies

DOE Office of Scientific and Technical Information (OSTI.GOV)

Borowiak, Alexis S.; Baboux, Nicolas; Albertini, David

The electromechanical response of a 3 nm thick amorphous LaAlO{sub 3} layer obtained by molecular beam epitaxy has been studied using scanning probe microscopies. Although this kind of sample is not ferroelectric due to its amorphous nature, the resulting images are identical to what is generally obtained on truly ferroelectric samples probed by piezoresponse force microscopy: domains of apparently opposite polarisation are detected, and perfect, square shaped hysteresis loops are recorded. Moreover, written patterns are stable within 72 h. We discuss in the general case the possible origins of this behaviour in terms of charge injection, ionic conduction and motion ofmore » oxygen vacancies. In the case presented in this paper, since the writing process has been conducted with applied voltages lower than the injection threshold measured by conductive atomic force Microscopy, allowing to withdraw the hypothesis of charge injection in the sample, we propose that a bistable distribution of oxygen vacancies is responsible for this contrast.« less

Electron beam induced current in the high injection regime.

PubMed

Haney, Paul M; Yoon, Heayoung P; Koirala, Prakash; Collins, Robert W; Zhitenev, Nikolai B

2015-07-24

Electron beam induced current (EBIC) is a powerful technique which measures the charge collection efficiency of photovoltaics with sub-micron spatial resolution. The exciting electron beam results in a high generation rate density of electron-hole pairs, which may drive the system into nonlinear regimes. An analytic model is presented which describes the EBIC response when the total electron-hole pair generation rate exceeds the rate at which carriers are extracted by the photovoltaic cell, and charge accumulation and screening occur. The model provides a simple estimate of the onset of the high injection regime in terms of the material resistivity and thickness, and provides a straightforward way to predict the EBIC lineshape in the high injection regime. The model is verified by comparing its predictions to numerical simulations in one- and two-dimensions. Features of the experimental data, such as the magnitude and position of maximum collection efficiency versus electron beam current, are consistent with the three-dimensional model.

Visual tracing of diffusion and biodistribution for amphiphilic cationic nanoparticles using photoacoustic imaging after ex vivo intravitreal injections

PubMed Central

Xu, Xu; Xu, Zhaokang; Liu, Junyi; Zhang, Zhaoliang; Chen, Hao; Li, Xingyi; Shi, Shuai

2016-01-01

To visually trace the diffusion and biodistribution of amphiphilic cation micelles after vitreous injection, various triblock copolymers of monomethoxy poly(ethylene glycol)–poly(ε-caprolactone)–polyethylenimine were synthesized with different structures of hydrophilic and hydrophobic segments, followed by labeling with near-infrared fluorescent dye Cyanine5 or Cyanine7. The micellar size, polydispersity index, and surface charge were measured by dynamic light scattering. The diffusion was monitored using photoacoustic imaging in real time after intravitreal injections. Moreover, the labeled nanoparticle distribution in the posterior segment of the eye was imaged histologically by confocal microscopy. The results showed that the hydrophilic segment increased vitreous diffusion, while a positive charge on the particle surface hindered diffusion. In addition, the particles diffused through the retinal layers and were enriched in the retinal pigment epithelial layer. This work tried to study the diffusion rate via a simple method by using visible images, and then provided basic data for the development of intraocular drug carriers. PMID:27785015

Comparative study of cross-field and field-aligned electron beams in active experiments. [in upper atmosphere

NASA Technical Reports Server (NTRS)

Winglee, R. M.; Pritchett, P. L.

1988-01-01

Beam-plasma interactions associated with the cross-field and field-aligned injection of electron beams from spacecraft were investigated using a two-dimensional (three velocity component) electrostatic particle simulations. It is shown that the beam properties and plasma response can be characterized well by the ratio between the stagnation time and the plasma response time, which depends on the ratio of the ambient plasma density to the beam density, the beam width, the beam energy, and the spacecraft length. It was found that the beams injected across the field lines tend to lose their coherence after about one or two gyrations due to space-charge oscillations induced by the beam, irrespective of the spacecraft charging. These oscillations scatter the beam electrons into a hollow cylinder of a radius equal to a beam electron gyroradius and thickness of the order of two beam Debye lengths. Parallel injected beams are subjected to similar oscillations, which cause the beam to expand to fill a solid cylinder of a comparable thickness.

Enhancement of plasmon-induced charge separation efficiency by coupling silver nanocubes with a thin gold film

NASA Astrophysics Data System (ADS)

Akiyoshi, Kazutaka; Saito, Koichiro; Tatsuma, Tetsu

2016-10-01

Plasmon-induced charge separation (PICS), in which an energetic electron is injected from a plasmonic nanoparticle (NP) to a semiconductor on contact, is often inhibited by a protecting agent adsorbed on the NP. We addressed this issue for an Ag nanocube-TiO2 system by coating it with a thin Au layer or by inserting the Au layer between the nanocubes (NCs) and TiO2. Both of the electrodes exhibit much higher photocurrents due to PICS than the electrodes without the Au film or the Ag NCs. These photocurrent enhancements can be explained in terms of PICS with accelerated electron transfer, in which electron injection from the Ag NCs or Ag@Au core-shell NCs to TiO2 is promoted by the Au film, or PICS enhanced by a nanoantenna effect, in which the electron injection from the Au film to TiO2 is enhanced by optical near field generated by the Ag NC.

Visual tracing of diffusion and biodistribution for amphiphilic cationic nanoparticles using photoacoustic imaging after ex vivo intravitreal injections.

PubMed

Xu, Xu; Xu, Zhaokang; Liu, Junyi; Zhang, Zhaoliang; Chen, Hao; Li, Xingyi; Shi, Shuai

To visually trace the diffusion and biodistribution of amphiphilic cation micelles after vitreous injection, various triblock copolymers of monomethoxy poly(ethylene glycol)-poly(ε-caprolactone)-polyethylenimine were synthesized with different structures of hydrophilic and hydrophobic segments, followed by labeling with near-infrared fluorescent dye Cyanine5 or Cyanine7. The micellar size, polydispersity index, and surface charge were measured by dynamic light scattering. The diffusion was monitored using photoacoustic imaging in real time after intravitreal injections. Moreover, the labeled nanoparticle distribution in the posterior segment of the eye was imaged histologically by confocal microscopy. The results showed that the hydrophilic segment increased vitreous diffusion, while a positive charge on the particle surface hindered diffusion. In addition, the particles diffused through the retinal layers and were enriched in the retinal pigment epithelial layer. This work tried to study the diffusion rate via a simple method by using visible images, and then provided basic data for the development of intraocular drug carriers.

Electromechanical response of amorphous LaAlO3 thin film probed by scanning probe microscopies

NASA Astrophysics Data System (ADS)

Borowiak, Alexis S.; Baboux, Nicolas; Albertini, David; Vilquin, Bertrand; Saint Girons, Guillaume; Pelloquin, Sylvain; Gautier, Brice

2014-07-01

The electromechanical response of a 3 nm thick amorphous LaAlO3 layer obtained by molecular beam epitaxy has been studied using scanning probe microscopies. Although this kind of sample is not ferroelectric due to its amorphous nature, the resulting images are identical to what is generally obtained on truly ferroelectric samples probed by piezoresponse force microscopy: domains of apparently opposite polarisation are detected, and perfect, square shaped hysteresis loops are recorded. Moreover, written patterns are stable within 72 h. We discuss in the general case the possible origins of this behaviour in terms of charge injection, ionic conduction and motion of oxygen vacancies. In the case presented in this paper, since the writing process has been conducted with applied voltages lower than the injection threshold measured by conductive atomic force Microscopy, allowing to withdraw the hypothesis of charge injection in the sample, we propose that a bistable distribution of oxygen vacancies is responsible for this contrast.

Study of status of safe injection practice and knowledge regarding injection safety among primary health care workers in Baglung district, western Nepal.

PubMed

Gyawali, Sudesh; Rathore, Devendra S; Kc, Bhuvan; Shankar, P Ravi

2013-01-03

Unsafe injection practices and injection overuse are widespread in developing countries harming the patient and inviting risks to the health care workers. In Nepal, there is a dearth of documented information about injection practices so the present study was carried out: a) to determine whether the selected government health facilities satisfy the conditions for safe injections in terms of staff training, availability of sterile injectable equipment and their proper disposal after use and b) to assess knowledge and attitudes of healthcare workers in these health care facilities with regard to injection safety. A descriptive cross-sectional mixed type (qualitative and quantitative) survey was carried out from 18th May to 16th June 2012. In-depth interviews with the in-charges were conducted using a semi-structured questionnaire. Observation of the health facilities using a structured observation tool was done. The data were analysed manually by summarizing, tabulating and presenting in various formats. The in-charges (eight males, two females) who participated in the study ranged in age from 30 to 50 years with a mean age of 37.8 years. Severe infection followed by pain was the most important cause for injection use with injection Gentamicin being most commonly prescribed. New single use (disposable) injections and auto-disable syringes were used to inject curative drugs and vaccines respectively. Sufficient safety boxes were also supplied to dispose the used syringe. All health care workers had received full course of Hepatitis B vaccine and were knowledgeable about at least one pathogen transmitted through unsafe injection practices. Injection safety management policy and waste disposal guideline was not available for viewing in any of the facilities. The office staff who disposed the bio-medical wastes did so without taking any safety measures. Moreover, none of these staff had received any formal training in waste management. Certain safe injection practices were noticed in the studied health care facilities but there remain a number of grey areas where unsafe practices still persists placing patient and health workers at risk of associated hazards. Training concentrating on injection safety, guidelines to dispose biomedical waste and monitoring of the activity is needed.

Study of status of safe injection practice and knowledge regarding injection safety among primary health care workers in Baglung district, western Nepal

PubMed Central

2013-01-01

Background Unsafe injection practices and injection overuse are widespread in developing countries harming the patient and inviting risks to the health care workers. In Nepal, there is a dearth of documented information about injection practices so the present study was carried out: a) to determine whether the selected government health facilities satisfy the conditions for safe injections in terms of staff training, availability of sterile injectable equipment and their proper disposal after use and b) to assess knowledge and attitudes of healthcare workers in these health care facilities with regard to injection safety. Methodology A descriptive cross-sectional mixed type (qualitative and quantitative) survey was carried out from 18th May to 16th June 2012. In-depth interviews with the in-charges were conducted using a semi-structured questionnaire. Observation of the health facilities using a structured observation tool was done. The data were analysed manually by summarizing, tabulating and presenting in various formats. Results The in-charges (eight males, two females) who participated in the study ranged in age from 30 to 50 years with a mean age of 37.8 years. Severe infection followed by pain was the most important cause for injection use with injection Gentamicin being most commonly prescribed. New single use (disposable) injections and auto-disable syringes were used to inject curative drugs and vaccines respectively. Sufficient safety boxes were also supplied to dispose the used syringe. All health care workers had received full course of Hepatitis B vaccine and were knowledgeable about at least one pathogen transmitted through unsafe injection practices. Injection safety management policy and waste disposal guideline was not available for viewing in any of the facilities. The office staff who disposed the bio-medical wastes did so without taking any safety measures. Moreover, none of these staff had received any formal training in waste management. Conclusions Certain safe injection practices were noticed in the studied health care facilities but there remain a number of grey areas where unsafe practices still persists placing patient and health workers at risk of associated hazards. Training concentrating on injection safety, guidelines to dispose biomedical waste and monitoring of the activity is needed. PMID:23286907

Room-Temperature Triple-Ligand Surface Engineering Synergistically Boosts Ink Stability, Recombination Dynamics, and Charge Injection toward EQE-11.6% Perovskite QLEDs.

PubMed

Song, Jizhong; Li, Jinhang; Xu, Leimeng; Li, Jianhai; Zhang, Fengjuan; Han, Boning; Shan, Qingsong; Zeng, Haibo

2018-06-10

Developing low-cost and high-quality quantum dots (QDs) or nanocrystals (NCs) and their corresponding efficient light-emitting diodes (LEDs) is crucial for the next-generation ultra-high-definition flexible displays. Here, there is a report on a room-temperature triple-ligand surface engineering strategy to play the synergistic role of short ligands of tetraoctylammonium bromide (TOAB), didodecyldimethylammonium bromide (DDAB), and octanoic acid (OTAc) toward "ideal" perovskite QDs with a high photoluminescence quantum yield (PLQY) of >90%, unity radiative decay in its intrinsic channel, stable ink characteristics, and effective charge injection and transportation in QD films, resulting in the highly efficient QD-based LEDs (QLEDs). Furthermore, the QD films with less nonradiative recombination centers exhibit improved PL properties with a PLQY of 61% through dopant engineering in A-site. The robustness of such properties is demonstrated by the fabrication of green electroluminescent LEDs based on CsPbBr 3 QDs with the peak external quantum efficiency (EQE) of 11.6%, and the corresponding peak internal quantum efficiency (IQE) and power efficiency are 52.2% and 44.65 lm W -1 , respectively, which are the most-efficient perovskite QLEDs with colloidal CsPbBr 3 QDs as emitters up to now. These results demonstrate that the as-obtained QD inks have a wide range application in future high-definition QD displays and high-quality lightings. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

A transistor based on 2D material and silicon junction

NASA Astrophysics Data System (ADS)

Kim, Sanghoek; Lee, Seunghyun

2017-07-01

A new type of graphene-silicon junction transistor based on bipolar charge-carrier injection was designed and investigated. In contrast to many recent studies on graphene field-effect transistor (FET), this device is a new type of bipolar junction transistor (BJT). The transistor fully utilizes the Fermi level tunability of graphene under bias to increase the minority-carrier injection efficiency of the base-emitter junction in the BJT. Single-layer graphene was used to form the emitter and the collector, and a p-type silicon was used as the base. The output of this transistor was compared with a metal-silicon junction transistor ( i.e. surface-barrier transistor) to understand the difference between a graphene-silicon junction and metal-silicon Schottky junction. A significantly higher current gain was observed in the graphene-silicon junction transistor as the base current was increased. The graphene-semiconductor heterojunction transistor offers several unique advantages, such as an extremely thin device profile, a low-temperature (< 110 °C) fabrication process, low cost (no furnace process), and high-temperature tolerance due to graphene's stability. A transistor current gain ( β) of 33.7 and a common-emitter amplifier voltage gain of 24.9 were achieved.

Highly Efficient and Fully Solution-Processed Inverted Light-Emitting Diodes with Charge Control Interlayers.

PubMed

Fu, Yan; Jiang, Wei; Kim, Daekyoung; Lee, Woosuk; Chae, Heeyeop

2018-05-23

In this work, we developed a charge control sandwich structure around QD layers for the inverted QLEDs, the performance of which is shown to exceed that of the conventional QLEDs in terms of the external quantum efficiency (EQE) and the current efficiency (CE). The QD light-emitting layer (EML) is sandwiched with two ultrathin interfacial layers: one is a poly(9-vinlycarbazole) (PVK) layer to prevent excess electrons, and the other is a polyethylenimine ethoxylated (PEIE) layer to reduce the hole injection barrier. The sandwich structure resolves the imbalance between injected holes and electrons and brings the level of balanced charge carriers to a maximum. We demonstrated the highly improved performance of 89.8 cd/A of current efficiency, 22.4% of external quantum efficiency, and 72 814 cd m -2 of maximum brightness with the solution-processed inverted QLED. This sandwich structure (PVK/QD/PEIE), as a framework, can be applied to various QLED devices for enhancing performance.

Switching Hole and Electron Transports of Molecules on Metal Oxides by Energy Level Alignment Tuning.

PubMed

Bao, Zhong-Min; Xu, Rui-Peng; Li, Chi; Xie, Zhong-Zhi; Zhao, Xin-Dong; Zhang, Yi-Bo; Li, Yan-Qing; Tang, Jian-Xin

2016-08-31

Charge transport at organic/inorganic hybrid contacts significantly affects the performance of organic optoelectronic devices because the unfavorable energy level offsets at these interfaces can hinder charge injection or extraction due to large barrier heights. Herein, we report a technologically relevant method to functionalize a traditional hole-transport layer of solution-processed nickel oxide (NiOx) with various interlayers. The photoemission spectroscopy measurements reveal the continuous tuning of the NiOx substrate work function ranging from 2.5 to 6.6 eV, enabling the alignment transition of energy levels between the Schottky-Mott limit and Fermi level pinning at the organic/composite NiOx interface. As a result, switching hole and electron transport for the active organic material on the composite NiOx layer is achieved due to the controlled carrier injection/extraction barriers. The experimental findings indicate that tuning the work function of metal oxides with optimum energy level offsets can facilitate the charge transport at organic/electrode contacts.

Effect of the NACA Injection Impeller on the Mixture Distribution of a Double-row Radial Aircraft Engine

NASA Technical Reports Server (NTRS)

Marble, Frank E.; Ritter, William K.; Miller, Mahlon A.

1946-01-01

For the normal range of engine power the impeller provided marked improvement over the standard spray-bar injection system. Mixture distribution at cruising was excellent, maximum cylinder temperatures were reduced about 30 degrees F, and general temperature distribution was improved. The uniform mixture distribution restored the normal response of cylinder temperature to mixture enrichment and it reduced the possibility of carburetor icing, while no serious loss in supercharger pressure rise resulted from injection of fuel near the impeller outlet. The injection impeller also furnished a convenient means of adding water to the charge mixture for internal cooling.

A study of effects of electrode contacts on performance of organic-based light-emitting field-effect transistors

NASA Astrophysics Data System (ADS)

Kim, Dae-Kyu; Choi, Jong-Ho

2018-02-01

Herein is presented a comparative performance analysis of heterojunction organic-based light-emitting field-effect transistors (OLEFETs) with symmetric (Au only) and asymmetric (Au and LiF/Al) electrode contacts. The devices had a top source-drain contact with long-channel geometry and were produced by sequentially depositing p-type pentacene and n-type N,N‧-ditridecylperylene-3,4,9,10-tetracarboxylic diimide (P13) using a neutral cluster beam deposition apparatus. The spectroscopic, structural and morphological properties of the organic thin films were examined using photoluminescence (PL) spectroscopy, X-ray diffraction (XRD) method, laser scanning confocal and atomic force microscopy (LSCM, AFM). Based upon the growth of high-quality, well-packed crystalline thin films, the devices demonstrated ambipolar field-effect characteristics, stress-free operational stability, and light emission under ambient conditions. Various device parameters were derived from the fits of the observed characteristics. The hole mobilities were nearly equal irrespective of the electrode contacts, whereas the electron mobilities of the transistors with LiF/Al drain electrodes were higher due to the low injection barrier. For the OLEFETs with symmetric electrodes, electroluminescence (EL) occurred only in the vicinity of the hole-injecting electrode, whereas for the OLEFETs with asymmetric electrodes, the emission occurred in the vicinity of both hole- and electron-injecting electrodes. By tuning the carrier injection and transport through high- and low-work function metals, the hole-electron recombination sites could be controlled. The operating conduction and light emission mechanism are discussed with the aid of EL images obtained using a charge-coupled device (CCD) camera.

Minimization of power consumption during charging of superconducting accelerating cavities

NASA Astrophysics Data System (ADS)

Bhattacharyya, Anirban Krishna; Ziemann, Volker; Ruber, Roger; Goryashko, Vitaliy

2015-11-01

The radio frequency cavities, used to accelerate charged particle beams, need to be charged to their nominal voltage after which the beam can be injected into them. The standard procedure for such cavity filling is to use a step charging profile. However, during initial stages of such a filling process a substantial amount of the total energy is wasted in reflection for superconducting cavities because of their extremely narrow bandwidth. The paper presents a novel strategy to charge cavities, which reduces total energy reflection. We use variational calculus to obtain analytical expression for the optimal charging profile. Energies, reflected and required, and generator peak power are also compared between the charging schemes and practical aspects (saturation, efficiency and gain characteristics) of power sources (tetrodes, IOTs and solid state power amplifiers) are also considered and analysed. The paper presents a methodology to successfully identify the optimal charging scheme for different power sources to minimize total energy requirement.

Analysis of Turbulent Combustion in Simplified Stratified Charge Conditions

NASA Astrophysics Data System (ADS)

Moriyoshi, Yasuo; Morikawa, Hideaki; Komatsu, Eiji

The stratified charge combustion system has been widely studied due to the significant potentials for low fuel consumption rate and low exhaust gas emissions. The fuel-air mixture formation process in a direct-injection stratified charge engine is influenced by various parameters, such as atomization, evaporation, and in-cylinder gas motion at high temperature and high pressure conditions. It is difficult to observe the in-cylinder phenomena in such conditions and also challenging to analyze the following stratified charge combustion. Therefore, the combustion phenomena in simplified stratified charge conditions aiming to analyze the fundamental stratified charge combustion are examined. That is, an experimental apparatus which can control the mixture distribution and the gas motion at ignition timing was developed, and the effects of turbulence intensity, mixture concentration distribution, and mixture composition on stratified charge combustion were examined. As a result, the effects of fuel, charge stratification, and turbulence on combustion characteristics were clarified.

DESIGN OF A HIGH COMPRESSION, DIRECT INJECTION, SPARK-IGNITION, METHANOL FUELED RESEARCH ENGINE WITH AN INTEGRAL INJECTOR-IGNITION SOURCE INSERT, SAE PAPER 2001-01-3651

EPA Science Inventory

A stratified charge research engine and test stand were designed and built for this work. The primary goal of this project was to evaluate the feasibility of using a removal integral injector ignition source insert which allows a convenient method of charging the relative locat...

Revealing the ultrafast charge carrier dynamics in organo metal halide perovskite solar cell materials using time resolved THz spectroscopy

NASA Astrophysics Data System (ADS)

Ponseca, C. S., Jr.; Sundström, V.

2016-03-01

Ultrafast charge carrier dynamics in organo metal halide perovskite has been probed using time resolved terahertz (THz) spectroscopy (TRTS). Current literature on its early time characteristics is unanimous: sub-ps charge carrier generation, highly mobile charges and very slow recombination rationalizing the exceptionally high power conversion efficiency for a solution processed solar cell material. Electron injection from MAPbI3 to nanoparticles (NP) of TiO2 is found to be sub-ps while Al2O3 NPs do not alter charge dynamics. Charge transfer to organic electrodes, Spiro-OMeTAD and PCBM, is sub-ps and few hundreds of ps respectively, which is influenced by the alignment of energy bands. It is surmised that minimizing defects/trap states is key in optimizing charge carrier extraction from these materials.

Design and operation of the pellet charge exchange diagnostic for measurement of energetic confined alphas and tritons on TFTR

DOE Office of Scientific and Technical Information (OSTI.GOV)

Medley, S.S.; Duong, H.H.; Fisher, R.K.

1996-05-01

Radially-resolved energy and density distributions of the energetic confined alpha particles in D-T experiments on TFTR are being measured by active neutral particle analysis using low-Z impurity pellet injection. When injected into a high temperature plasma, an impurity pellet (e.g. Lithium or Boron) rapidly ablates forming an elongated cloud which is aligned with the magnetic field and moves with the pellet. This ablation cloud provides a dense target with which the alpha particles produced in D-T fusion reactions can charge exchange. A small fraction of the alpha particles incident on the pellet ablation cloud will be converted to helium neutralsmore » whose energy is essentially unchanged by the charge transfer process. By measuring the resultant helium neutrals escaping from the plasma using a mass and energy resolving charge exchange analyzer, this technique offers a direct measurement of the energy distribution of the incident high-energy alpha particles. Other energetic ion species can be detected as well, such as tritons generated in D-D plasmas and H or He{sup 3} RF-driven minority ion tails. The diagnostic technique and its application on TFTR are described in detail.« less

Laboratory studies of aerosol electrification and experimental evidence for electrical breakdown at different scales.

NASA Astrophysics Data System (ADS)

Alois, Stefano; Merrison, Jonathan; Iversen, Jens Jacob; Sesterhenn, Joern

2017-04-01

Contact electrification between different particles size/material can lead to electric field generation high enough to produce electrical breakdown. Experimental studies of solid aerosol contact electrification (Alois et al., 2016) has shown various electrical breakdown phenomena; these range from field emission at the contact site (nm-scale) limiting particle surface charge concentration, to visible electrical discharges (cm-scale) observed both with the use of an electrometer and high-speed camera. In these experiments micron-size particles are injected into a low-pressure chamber, where they are deviated by an applied electric field. A laser Doppler velocimeter allows the simultaneous determination of particle size and charge of single grains. Results have shown an almost constant surface charge concentration, which is likely to be due to charge limitation by field emission at the contact site between particle and injector. In a second measurement technique, the electrically isolated injector tube (i.e. a Faraday cage) is connected to an oscilloscope and synchronised to a high speed camera filming the injection. Here the electrification of a large cloud of particles can be quantified and discharging effects studied. This study advances our understanding on the physical processes leading to electrification and electrical breakdown mechanisms.

High efficiency ZnO-based dye-sensitized solar cells with a 1H,1H,2H,2H-perfluorodecyltriethoxysilane chain barrier for cutting on interfacial recombination

NASA Astrophysics Data System (ADS)

Xie, Yahong; Zhou, Xiaofeng; Mi, Hongyu; Ma, Junhong; Yang, Jianya; Cheng, Jian

2018-03-01

Charge recombination at the ZnO photoanode/electrolyte interface is one of the major limitations for high performance dye-sensitized solar cells (DSSCs) toward their theoretical power conversion efficiency (PCE). Here, we proposed an efficient approach for reducing this interfacial losses and consequently facilitating charge transfer by decorating a hydrophobic thin-film on the surface of the dye-coated zinc oxide photoanode via 1H,1H,2H,2H-perfluorodecyltriethoxysilane (PFDTES) hexane solution immersing. As a result, a high PCE of 8.22% was obtained, which far exceeded the efficiency of 5.40% in a conventional DSSC without PFDTES treatment. Furthermore, PFDTES treatment also largely elongated the lifetime of photogenerated electrons, and maintained a good photo-response at the photoelectrode. This work provides a comprehensive explanation of electron injection, transfer and recombination at the ZnO photoanode/electrolyte interface, and a promising strategy to explore high efficiency ZnO-based DSSCs.

Comparison of Detector Technologies for CAPS

NASA Technical Reports Server (NTRS)

Stockum, Jana L.

2005-01-01

In this paper, several different detectors are examined for use in a Comet/Asteroid Protection System (CAPS), a conceptual study for a possible future space-based system. Each detector will be examined for its future (25 years or more in the future) ability to find and track near-Earth Objects (NEOs) from a space-based detection platform. Within the CAPS study are several teams of people who each focus on different aspects of the system concept. This study s focus is on detection devices. In particular, evaluations on the following devices have been made: charge-coupled devices (CCDs), charge-injected devices (CIDs), superconducting tunneling junctions (STJs), and transition edge sensors (TESs). These devices can be separated into two main categories; the first category includes detectors that are currently being widely utilized, such as CCDs and CIDs. The second category includes experimental detectors, such as STJs and TESs. After the discussion of the detectors themselves, there will be a section devoted to the explicit use of these detectors with CAPS.

Trains of electron micro-bunches in plasma wake-field acceleration

NASA Astrophysics Data System (ADS)

Lécz, Zsolt; Andreev, Alexander; Konoplev, Ivan; Seryi, Andrei; Smith, Jonathan

2018-07-01

Plasma-based charged particle accelerators have been intensively investigated in the past three decades due to their capability to open up new horizons in accelerator science and particle physics yielding electric field accelerating gradient more than three orders of magnitudes higher than in conventional devices. At the current stage the most advanced and reliable mechanism for accelerating electrons is based on the propagation of an intense laser pulse or a relativistic electron beam in a low density gaseous target. In this paper we concentrate on the electron beam-driven plasma wake-field acceleration and demonstrate using 3D PiC simulations that a train of electron micro-bunches with ∼10 fs period can be generated behind the driving beam propagating in a density down-ramp. We will discuss the conditions and properties of the micro-bunches generated aiming at understanding and study of multi-bunch mechanism of injection. It is show that the periodicity and duration of micro-bunches can be controlled by adjusting the plasma density gradient and driving beam charge.

Extraction of contaminants from a gas

DOEpatents

Babko-Malyi, Sergei

2000-01-01

A method of treating industrial gases to remove contaminants is disclosed. Ions are generated in stream of injectable gas. These ions are propelled through the contaminated gas as it flows through a collection unit. An electric field is applied to the contaminated gas. The field causes the ions to move through the contaminated gases, producing electrical charges on the contaminants. The electrically charged contaminants are then collected at one side of the electric field. The injectable gas is selected to produce ions which will produce reactions with particular contaminants. The process is thus capable of removing particular contaminants. The process does not depend on diffusion as a transport mechanism and is therefore suitable for removing contaminants which exist in very low concentrations.

Apparatus for extraction of contaminants from a gas

DOEpatents

Babko-Malyi, Sergei

2001-01-01

A method of treating industrial gases to remove contaminants is disclosed. Ions are generated in stream of injectable gas. These ions are propelled through the contaminated gas as it flows through a collection unit. An electric field is applied to the contaminated gas. The field causes the ions to move through the contaminated gases, producing electrical charges on the contaminants. The electrically charged contaminants are then collected at one side of the electric field. The injectable gas is selected to produce ions which will produce reactions with particular contaminants. The process is thus capable of removing particular contaminants. The process does not depend on diffusion as a transport mechanism and is therefore suitable for removing contaminants which exist in very low concentrations.

A study of a direct-injection stratified-charge rotary engine for motor vehicle application

NASA Astrophysics Data System (ADS)

Kagawa, Ryoji; Okazaki, Syunki; Somyo, Nobuhiro; Akagi, Yuji

1993-03-01

A study of a direct-injection stratified-charge system (DISC), as applied to a rotary engine (RE) for motor vehicle usage, was undertaken. The goals of this study were improved fuel consumption and reduced exhaust emissions. These goals were thought feasible due to the high thermal efficiency associated with the DISC-RE. This was the first application of this technology to a motor vehicle engine. Stable ignition and ideal stratification systems were developed by means of numerical calculations, air-fuel mixture measurements, and actual engine tests. The use of DISC resulted in significantly improved fuel consumption and reduced exhaust emissions. The use of an exhaust gas recirculating system was studied and found to be beneficial in NOx reduction.

UVIS CTE Monitor: Star Clusters

NASA Astrophysics Data System (ADS)

Noeske, Kai

2010-09-01

*** NOTE 2: 2ND CHANGE MAR 26 2011: VISIT 13 HAD FAILED. APPROVED FOR REPETITION. ****** NEW VISIT 14 IS IDENTICAL TO FORMER VISIT 13, WITH EXCEPTIONS THAT SOME SUBEXPOSURES ARE REMOVED. ****** SEE OBSERVING DESCRIPTION FOR DETAILS. ****** NOTE: THIS IS A CHANGED PHASE II PROPOSAL AFTER VISITS 1,2,7 HAD BEEN EXECUTED ****** CHANGES BECAME NECESSARY AFTER ANALYSIS OF INCOMING CALIBRATION DATA FROM 12379 AND 12348 ****** THIS REVISED PHASE II {submission 14FEB2011} ADDS THE EVALUATION OF CHARGE INJECTION***The changes amount to:1} dropping the 3rd epoch {August 2011} of external CTE monitoring {3 orbits}2} simplifying the CTE monitor observations in the second epoch {March 2011}, freeing up 1 orbit3} using the freed up orbits from 1} and 2}, together with two additional external orbits that we were granted, to thoroughly assess the data quality of charge - injected data under realistic observing setups.These charge-injected observations will be obtained during the 2nd epoch of the CTE monitor program, in the March 2011 window.------ Original Text prior to 14 Feb 2011 below this line -----------This program extends the Cycle 17 external CTE calibration {CAL/WFC3 ID 11924} program for WFC3/UVIS over Cycle 18. Targets are {i} the sparse cluster NGC 6791 observed in Cycle 17, to continue a consistent set of observations that allows to isolate the time evolution of the CTE, and {ii} a denser field in 47 Tuc {NGC 104}. The latter will provide data to measure the dependence of the CTE on field crowding. It will also provide a consistent comparison between the CTE evolution of WFC3/UVIS and that of ACS/WFC at the same time into the flight {1 year}, because ACS/WFC CTE data were based on 47 Tuc observations. Additional observations of 47 Tuc in the CVZ will provide a wide range of background levels to measure the background dependence of the UVIS CTE.Goals are {i} the continued monitoring of the time evolution of the WFC3/UVIS CTE, {ii} establishing the detector X,Y dependence of the CTE, {iii} CTE dependence of the background level and {iv} an improved CTE correction model based on these measurements. These goals include CTE effects on both photometry and astrometry.

TOPSIS-based parametric optimization of compression ignition engine performance and emission behavior with bael oil blends for different EGR and charge inlet temperature.

PubMed

Muniappan, Krishnamoorthi; Rajalingam, Malayalamurthi

2018-05-02

The demand for higher fuel energy and lesser exhaust emissions of diesel engines can be achieved by fuel being used and engine operating parameters. In the present work, effects of engine speed (RPM), injection timing (IT), injection pressure (IP), and compression ratio (CR) on performance and emission characteristics of a compression ignition (CI) engine were investigated. The ternary test fuel of 65% diesel + 25% bael oil + 10% diethyl ether (DEE) was used in this work and test was conducted at different charge inlet temperature (CIT) and exhaust gas recirculation (EGR). All the experiments are conducted at the tradeoff engine load that is 75% engine load. When operating the diesel engine with 320 K CIT, brake thermal efficiency (BTE) is improved to 28.6%, and carbon monoxide (CO) and hydrocarbon (HC) emissions have been reduced to 0.025% and 12.5 ppm at 18 CR. The oxide of nitrogen (NOx) has been reduced to 240 ppm at 1500 rpm for 30% EGR mode. Technique for Order of Preference by Similarity to Ideal Solution (TOPSIS) method is frequently used in multi-factor selection and gray correlation analysis method is used to study uncertain of the systems.

Optoelectronic retinal prosthesis: system design and performance

NASA Astrophysics Data System (ADS)

Loudin, J. D.; Simanovskii, D. M.; Vijayraghavan, K.; Sramek, C. K.; Butterwick, A. F.; Huie, P.; McLean, G. Y.; Palanker, D. V.

2007-03-01

The design of high-resolution retinal prostheses presents many unique engineering and biological challenges. Ever smaller electrodes must inject enough charge to stimulate nerve cells, within electrochemically safe voltage limits. Stimulation sites should be placed within an electrode diameter from the target cells to prevent 'blurring' and minimize current. Signals must be delivered wirelessly from an external source to a large number of electrodes, and visual information should, ideally, maintain its natural link to eye movements. Finally, a good system must have a wide range of stimulation currents, external control of image processing and the option of either anodic-first or cathodic-first pulses. This paper discusses these challenges and presents solutions to them for a system based on a photodiode array implant. Video frames are processed and imaged onto the retinal implant by a head-mounted near-to-eye projection system operating at near-infrared wavelengths. Photodiodes convert light into pulsed electric current, with charge injection maximized by applying a common biphasic bias waveform. The resulting prosthesis will provide stimulation with a frame rate of up to 50 Hz in a central 10° visual field, with a full 30° field accessible via eye movements. Pixel sizes are scalable from 100 to 25 µm, corresponding to 640-10 000 pixels on an implant 3 mm in diameter.

Spin interactions in InAs quantum dots

NASA Astrophysics Data System (ADS)

Doty, M. F.; Ware, M. E.; Stinaff, E. A.; Scheibner, M.; Bracker, A. S.; Gammon, D.; Ponomarev, I. V.; Reinecke, T. L.; Korenev, V. L.

2006-03-01

Fine structure splittings in optical spectra of self-assembled InAs quantum dots (QDs) generally arise from spin interactions between particles confined in the dots. We present experimental studies of the fine structure that arises from multiple charges confined in a single dot [1] or in molecular orbitals of coupled pairs of dots. To probe the underlying spin interactions we inject particles with a known spin orientation (by using polarized light to perform photoluminescence excitation spectroscopy experiments) or use a magnetic field to orient and/or mix the spin states. We develop a model of the spin interactions that aids in the development of quantum information processing applications based on controllable interactions between spins confined to QDs. [1] Polarized Fine Structure in the Photoluminescence Excitation Spectrum of a Negatively Charged Quantum Dot, Phys. Rev. Lett. 95, 177403 (2005)

Efficient exciton generation in atomic passivated CdSe/ZnS quantum dots light-emitting devices

PubMed Central

Kang, Byoung-Ho; Lee, Jae-Sung; Lee, Sang-Won; Kim, Sae-Wan; Lee, Jun-Woo; Gopalan, Sai-Anand; Park, Ji-Sub; Kwon, Dae-Hyuk; Bae, Jin-Hyuk; Kim, Hak-Rin; Kang, Shin-Won

2016-01-01

We demonstrate the first-ever surface modification of green CdSe/ZnS quantum dots (QDs) using bromide anions (Br-) in cetyl trimethylammonium bromide (CTAB). The Br- ions reduced the interparticle spacing between the QDs and induced an effective charge balance in QD light-emitting devices (QLEDs). The fabricated QLEDs exhibited efficient charge injection because of the reduced emission quenching effect and their enhanced thin film morphology. As a result, they exhibited a maximum luminance of 71,000 cd/m2 and an external current efficiency of 6.4 cd/A, both significantly better than those of their counterparts with oleic acid surface ligands. In addition, the lifetime of the Br- treated QD based QLEDs is significantly improved due to ionic passivation at the QDs surface. PMID:27686147

Use of incomplete energy recovery for the energy compression of large energy spread charged particle beams

DOEpatents

Douglas, David R [Newport News, VA; Benson, Stephen V [Yorktown, VA

2007-01-23

A method of energy recovery for RF-base linear charged particle accelerators that allows energy recovery without large relative momentum spread of the particle beam involving first accelerating a waveform particle beam having a crest and a centroid with an injection energy E.sub.o with the centroid of the particle beam at a phase offset f.sub.o from the crest of the accelerating waveform to an energy E.sub.full and then recovering the beam energy centroid a phase f.sub.o+Df relative to the crest of the waveform particle beam such that (E.sub.full-E.sub.o)(1+cos(f.sub.o+Df))>dE/2 wherein dE=the full energy spread, dE/2=the full energy half spread and Df=the wave form phase distance.

A graphene solution to conductivity mismatch: spin injection from ferromagnetic metal/graphene tunnel contacts into silicon

NASA Astrophysics Data System (ADS)

van't Erve, Olaf

2014-03-01

New paradigms for spin-based devices, such as spin-FETs and reconfigurable logic, have been proposed and modeled. These devices rely on electron spin being injected, transported, manipulated and detected in a semiconductor channel. This work is the first demonstration on how a single layer of graphene can be used as a low resistance tunnel barrier solution for electrical spin injection into Silicon at room temperature. We will show that a FM metal / monolayer graphene contact serves as a spin-polarized tunnel barrier which successfully circumvents the classic metal / semiconductor conductivity mismatch issue for electrical spin injection. We demonstrate electrical injection and detection of spin accumulation in Si above room temperature, and show that the corresponding spin lifetimes correlate with the Si carrier concentration, confirming that the spin accumulation measured occurs in the Si and not in interface trap states. An ideal tunnel barrier should exhibit several key material characteristics: a uniform and planar habit with well-controlled thickness, minimal defect / trapped charge density, a low resistance-area product for minimal power consumption, and compatibility with both the FM metal and semiconductor, insuring minimal diffusion to/from the surrounding materials at temperatures required for device processing. Graphene, offers all of the above, while preserving spin injection properties, making it a compelling solution to the conductivity mismatch for spin injection into Si. Although Graphene is very conductive in plane, it exhibits poor conductivity perpendicular to the plane. Its sp2 bonding results in a highly uniform, defect free layer, which is chemically inert, thermally robust, and essentially impervious to diffusion. The use of a single monolayer of graphene at the Si interface provides a much lower RA product than any film of an oxide thick enough to prevent pinholes (1 nm). Our results identify a new route to low resistance-area product spin-polarized contacts, a crucial requirement enabling future semiconductor spintronic devices, which rely upon two-terminal magnetoresistance, including spin-based transistors, logic and memory.

INJECTION SYSTEM DESIGN FOR THE BSNS/RCS.

DOE Office of Scientific and Technical Information (OSTI.GOV)

WEI, J.; TANG, J.Y.; CHEN, Y.

2006-06-23

The BSNS injection system is designed to take one uninterrupted long drift in one of the four dispersion-free straight sections to host all the injection devices. Painting bumper magnets are used for both horizontal and vertical phase space painting. Closed-orbit bumper magnets are used for facilitating the installation of the injection septa and decreasing proton traversal in the stripping foil. Even with large beam emittance of about 300 {pi}mm.mrad used, BSNS/RCS still approaches the space charge limit during the injection/trapping phase for the accumulated particles of 1.9*10{sup 13} and at the low injection energy of 80 MeV. Uniform-like beam distributionmore » by well-designed painting scheme is then obtained to decrease the tune shift/spread. ORBIT code is used for the 3D simulations. Upgrading to higher injection energy has also been considered.« less

The push for increased coal injection rates -- Blast furnace experience at AK Steel Corporation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dibert, W.A.; Duncan, J.H.; Keaton, D.E.

1994-12-31

An effort has been undertaken to increase the coal injection rate on Amanda blast furnace at AK Steel Corporation`s Ashland Works in Ashland, Kentucky to decrease fuel costs and reduce coke demand. Operating practices have been implemented to achieve a sustained coal injection rate of 140 kg/MT, increased from 100--110 kg/MT. In order to operate successfully at the 140 kg/MT injection rate; changes were implemented to the furnace charging practice, coal rate control methodology, orientation of the injection point, and the manner of distribution of coal to the multiple injection points. Additionally, changes were implemented in the coal processing facilitymore » to accommodate the higher demand of pulverized coal; grinding 29 tonnes per hour, increased from 25 tonnes per hour. Further increases in injection rate will require a supplemental supply of fuel.« less

Researches on direct injection in internal-combustion engines

NASA Technical Reports Server (NTRS)

Tuscher, Jean E

1941-01-01

These researches present a solution for reducing the fatigue of the Diesel engine by permitting the preservation of its components and, at the same time, raising its specific horsepower to a par with that of carburetor engines, while maintaining for the Diesel engine its perogative of burning heavy fuel under optimum economical conditions. The feeding of Diesel engines by injection pumps actuated by engine compression achieves the required high speeds of injection readily and permits rigorous control of the combustible charge introduced into each cylinder and of the peak pressure in the resultant cycle.

Scintillator-fiber charged particle track-imaging detector

NASA Technical Reports Server (NTRS)

Binns, W. R.; Israel, M. H.; Klarmann, J.

1983-01-01

A scintillator-fiber charged-particle track-imaging detector was developed using a bundle of square cross section plastic scintillator fiber optics, proximity focused onto an image intensified charge injection device (CID) camera. The tracks of charged particle penetrating into the scintillator fiber bundle are projected onto the CID camera and the imaging information is read out in video format. The detector was exposed to beams of 15 MeV protons and relativistic Neon, Manganese, and Gold nuclei and images of their tracks were obtained. Details of the detector technique, properties of the tracks obtained, and preliminary range measurements of 15 MeV protons stopping in the fiber bundle are presented.

CCD radiation damage in ESA Cosmic Visions missions: assessment and mitigation

NASA Astrophysics Data System (ADS)

Lumb, David H.

2009-08-01

Charge Coupled Device (CCD) imagers have been widely used in space-borne astronomical instruments. A frequent concern has been the radiation damage effects on the CCD charge transfer properties. We review some methods for assessing the Charge Transfer Inefficiency (CTI) in CCDs. Techniques to minimise degradation using background charge injection and p-channel CCD architectures are discussed. A critical review of the claims for p-channel architectures is presented. The performance advantage for p-channel CCD performance is shown to be lower than claimed previously. Finally we present some projections for the performance in the context of some future ESA missions.

Tuning charge balance in PHOLEDs with ambipolar host materials to achieve high efficiency

DOE Office of Scientific and Technical Information (OSTI.GOV)

Padmaperuma, Asanga B.; Koech, Phillip K.; Cosimbescu, Lelia

2009-08-27

The efficiency and stability of blue organic light emitting devices (OLEDs) continue to be a primary roadblock to developing organic solid state white lighting. For OLEDs to meet the high power conversion efficiency goal, they will require both close to 100% internal quantum efficiency and low operating voltage in a white light emitting device.1 It is generally accepted that such high quantum efficiency, can only be achieved with the use of organometallic phosphor doped OLEDs. Blue OLEDs are particularly important for solid state lighting. The simplest (and therefore likely the lowest cost) method of generating white light is to downmore » convert part of the emission from a blue light source with a system of external phosphors.2 A second method of generating white light requires the superposition of the light from red, green and blue OLEDs in the correct ratio. Either of these two methods (and indeed any method of generating white light with a high color rendering index) critically depends on a high efficiency blue light component.3 A simple OLED generally consists of a hole-injecting anode, a preferentially hole transporting organic layer (HTL), an emissive layer that contains the recombination zone and ideally transports both holes and electrons, a preferentially electron-transporting layer (ETL) and an electron-injecting cathode. Color in state-of-the-art OLEDs is generated by an organometallic phosphor incorporated by co-sublimation into the emissive layer (EML).4 New materials functioning as hosts, emitters, charge transporting, and charge blocking layers have been developed along with device architectures leading to electrophosphorescent based OLEDs with high quantum efficiencies near the theoretical limit. However, the layers added to the device architecture to enable high quantum efficiencies lead to higher operating voltages and correspondingly lower power efficiencies. Achievement of target luminance power efficiencies will require new strategies for lowering operating voltages, particularly if this is to be achieved in a device that can be manufactured at low cost. To avoid the efficiency losses associated with phosphorescence quenching by back-energy transfer from the dopant onto the host, the triplet excited states of the host material must be higher in energy than the triplet excited state of the dopant.5 This must be accomplished without sacrificing the charge transporting properties of the composite.6 Similar problems limit the efficiency of OLED-based displays, where blue light emitters are the least efficient and least stable. We previously demonstrated the utility of organic phosphine oxide (PO) materials as electron transporting HMs for FIrpic in blue OLEDs.7 However, the high reluctance of PO materials to oxidation and thus, hole injection limits the ability to balance charge injection and transport in the EML without relying on charge transport by the phosphorescent dopant. PO host materials were engineered to transport both electrons and holes in the EML and still maintain high triplet exciton energy to ensure efficient energy transfer to the dopant (Figure 1). There are examples of combining hole transporting moieties (mainly aromatic amines) with electron transport moieties (e.g., oxadiazoles, triazines, boranes)8 to develop new emitter and host materials for small molecule and polymer9 OLEDs. The challenge is to combine the two moieties without lowering the triplet energy of the target molecule. For example, coupling of a dimesitylphenylboryl moiety with a tertiary aromatic amine (FIAMBOT) results in intramolecular electron transfer from the amine to the boron atom through the bridging phenyl. The mesomeric effect of the dimesitylphenylboryl unit acts to extend conjugation and lowers triplet exciton energies (< 2.8 eV) rendering such systems inadequate as ambipolar hosts for blue phosphors.« less

Microneedle-mediated transcutaneous immunization with plasmid DNA coated on cationic PLGA nanoparticles.

PubMed

Kumar, Amit; Wonganan, Piyanuch; Sandoval, Michael A; Li, Xinran; Zhu, Saijie; Cui, Zhengrong

2012-10-28

Previously, it was shown that microneedle-mediated transcutaneous immunization with plasmid DNA can potentially induce a stronger immune response than intramuscular injection of the same plasmid DNA. In the present study, we showed that the immune responses induced by transcutaneous immunization by applying plasmid DNA onto a skin area pretreated with solid microneedles were significantly enhanced by coating the plasmid DNA on the surface of cationic nanoparticles. In addition, the net surface charge of the DNA-coated nanoparticles significantly affected their in vitro skin permeation and their ability to induce immune responses in vivo. Transcutaneous immunization with plasmid DNA-coated net positively charged nanoparticles elicited a stronger immune response than with plasmid DNA-coated net negatively charged nanoparticles or by intramuscular immunization with plasmid DNA alone. Transcutaneous immunization with plasmid DNA-coated net positively charged nanoparticles induced comparable immune responses as intramuscular injection of them, but transcutaneous immunization was able to induce specific mucosal immunity and a more balanced T helper type 1 and type 2 response. The ability of the net positively charged DNA-coated nanoparticles to induce a strong immune response through microneedle-mediated transcutaneous immunization may be attributed to their ability to increase the expression of the antigen gene encoded by the plasmid and to more effectively stimulate the maturation of antigen-presenting cells. Copyright © 2012 Elsevier B.V. All rights reserved.

Recovery and identification of bacterial DNA from illicit drugs.

PubMed

Cho, Kaymann T; Richardson, Michelle M; Kirkbride, K Paul; McNevin, Dennis; Nelson, Michelle; Pianca, Dennis; Roffey, Paul; Gahan, Michelle E

2014-02-01

Bacterial infections, including Bacillus anthracis (anthrax), are a common risk associated with illicit drug use, particularly among injecting drug users. There is, therefore, an urgent need to survey illicit drugs used for injection for the presence of bacteria and provide valuable information to health and forensic authorities. The objectives of this study were to develop a method for the extraction of bacterial DNA from illicit drugs and conduct a metagenomic survey of heroin and methamphetamine seized in the Australian Capital Territory during 2002-2011 for the presence of pathogens. Trends or patterns in drug contamination and their health implications for injecting drug users were also investigated. Methods based on the ChargeSwitch(®)gDNA mini kit (Invitrogen), QIAamp DNA extraction mini kit (QIAGEN) with and without bead-beating, and an organic phenol/chloroform extraction with ethanol precipitation were assessed for the recovery efficiency of both free and cellular bacterial DNA. Bacteria were identified using polymerase chain reaction and electrospray ionization-mass spectrometry (PCR/ESI-MS). An isopropanol pre-wash to remove traces of the drug and diluents, followed by a modified ChargeSwitch(®) method, was found to efficiently lyse cells and extract free and cellular DNA from Gram-positive and Gram-negative bacteria in heroin and methamphetamine which could then be identified by PCR/ESI-MS. Analysis of 12 heroin samples revealed the presence of DNA from species of Comamonas, Weissella, Bacillus, Streptococcus and Arthrobacter. No organisms were detected in the nine methamphetamine samples analysed. This study develops a method to extract and identify Gram-positive and Gram-negative bacteria from illicit drugs and demonstrates the presence of a range of bacterial pathogens in seized drug samples. These results will prove valuable for future work investigating trends or patterns in drug contamination and their health implications for injecting drug users as well as enabling forensic links between seizures to be examined. Copyright © 2014 Elsevier Ireland Ltd. All rights reserved.

SELF ALIGNED TIP DEINSULATION OF ATOMIC LAYER DEPOSITED AL2O3 AND PARYLENE C COATED UTAH ELECTRODE ARRAY BASED NEURAL INTERFACES

PubMed Central

Xie, Xianzong; Rieth, Loren; Negi, Sandeep; Bhandari, Rajmohan; Caldwell, Ryan; Sharma, Rohit; Tathireddy, Prashant; Solzbacher, Florian

2014-01-01

The recently developed alumina and Parylene C bi-layer encapsulation improved the lifetime of neural interfaces. Tip deinsulation of Utah electrode array based neural interfaces is challenging due to the complex 3D geometries and high aspect ratios of the devices. A three-step self-aligned process was developed for tip deinsulation of bilayer encapsulated arrays. The deinsulation process utilizes laser ablation to remove Parylene C, O2 reactive ion etching to remove carbon and Parylene residues, and buffered oxide etch to remove alumina deposited by atomic layer deposition, and expose the IrOx tip metallization. The deinsulated iridium oxide area was characterized by scanning electron microscopy, atomic force microscopy, X-ray photoelectron spectroscopy, and electrochemical impedance spectroscopy to determine the morphology, surface morphology, composition, and electrical properties of the deposited layers and deinsulated tips. The alumina layer was found to prevent the formation of micro cracks on iridium oxide during the laser ablation process, which has been previously reported as a challenge for laser deinsulation of Parylene films. The charge injection capacity, charge storage capacity, and impedance of deinsulated iridium oxide were characterized to determine the deinsulation efficacy compared to Parylene-only insulation. Deinsulated iridium oxide with bilayer encapsulation had higher charge injection capacity (240 vs 320 nC) and similar electrochemical impedance (2.5 vs 2.5 kΩ) compared to deinsulated iridium oxide with only Parylene coating for an area of 2 × 10−4 cm2. Tip impedances were in the ranges of 20 to 50 kΩ, with median of 32 KΩ and standard deviation of 30 kΩ, showing the effectiveness of the self-aligned deinsulation process for alumina and Parylene C bi-layer encapsulation. The relatively uniform tip impedance values demonstrated the consistency of tip exposures. PMID:24771981

A cooler Penning trap for the TITAN mass measurement facility

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chowdhury, U.; Kootte, B.; Good, M.

The TITAN facility at TRIUMF makes use of highly charged ions, charge-bred in an electron beam ion trap, to carry out accurate mass measurements on radioactive isotopes. We report on our progress to develop a cooler Penning trap, CPET, which aims at reducing the energy spread of the ions to ≈ 1 eV/charge prior to injection into the mass measurement trap. In off-line mode, we can now trap electron plasmas for minutes, and we observe the damping of the m = 1 diocotron plasma mode within ≈ 2 s.

Injectable nano-network for glucose-mediated insulin delivery.

PubMed

Gu, Zhen; Aimetti, Alex A; Wang, Qun; Dang, Tram T; Zhang, Yunlong; Veiseh, Omid; Cheng, Hao; Langer, Robert S; Anderson, Daniel G

2013-05-28

Diabetes mellitus, a disorder of glucose regulation, is a global burden affecting 366 million people across the world. An artificial "closed-loop" system able to mimic pancreas activity and release insulin in response to glucose level changes has the potential to improve patient compliance and health. Herein we develop a glucose-mediated release strategy for the self-regulated delivery of insulin using an injectable and acid-degradable polymeric network. Formed by electrostatic interaction between oppositely charged dextran nanoparticles loaded with insulin and glucose-specific enzymes, the nanocomposite-based porous architecture can be dissociated and subsequently release insulin in a hyperglycemic state through the catalytic conversion of glucose into gluconic acid. In vitro insulin release can be modulated in a pulsatile profile in response to glucose concentrations. In vivo studies validated that these formulations provided improved glucose control in type 1 diabetic mice subcutaneously administered with a degradable nano-network. A single injection of the developed nano-network facilitated stabilization of the blood glucose levels in the normoglycemic state (<200 mg/dL) for up to 10 days.

Dynamics of Singlet Fission and Electron Injection in Self-Assembled Acene Monolayers on Titanium Dioxide

DOE Office of Scientific and Technical Information (OSTI.GOV)

Johnson, Justin C; Pace, Natalie A; Arias, Dylan H

We employ a combination of linear spectroscopy, electrochemistry, and transient absorption spectroscopy to characterize the interplay between electron transfer and singlet fission dynamics in polyacene-based dyes attached to nanostructured TiO2. For triisopropyl silylethynyl (TIPS)-pentacene, we find that the singlet fission time constant increases to 6.5 ps on a nanostructured TiO2 surface relative to a thin film time constant of 150 fs, and that triplets do not dissociate after they are formed. In contrast, TIPS-tetracene singlets quickly dissociate in 2 ps at the molecule/TiO2 interface, and this dissociation outcompetes the relatively slow singlet fission process. The addition of an alumina layermore » slows down electron injection, allowing the formation of triplets from singlet fission in 40 ps. However, the triplets do not inject electrons, which is likely due to a lack of sufficient driving force for triplet dissociation. These results point to the critical balance required between efficient singlet fission and appropriate energetics for interfacial charge transfer.« less

Precipitation regions on the Earth of high energy electrons, injected by a point source moving along a circular Earth orbit

NASA Astrophysics Data System (ADS)

Kolesnikov, E. K.; Klyushnikov, G. N.

2018-05-01

In the paper we continue the study of precipitation regions of high-energy charged particles, carried out by the authors since 2002. In contrast to previous papers, where a stationary source of electrons was considered, it is assumed that the source moves along a low circular near-earth orbit with a constant velocity. The orbit position is set by the inclination angle of the orbital plane to the equatorial plane and the longitude of the ascending node. The total number of injected electrons is determined by the source strength and the number of complete revolutions that the source makes along the circumference. Construction of precipitation regions is produced using the computational algorithm based on solving of the system of ordinary differential equations. The features of the precipitation regions structure for the dipole approximation of the geomagnetic field and the symmetrical arrangement of the orbit relative to the equator are noted. The dependencies of the precipitation regions on different orbital parametres such as the incline angle, the ascending node position and kinetic energy of injected particles have been considered.

Ion Heating During Local Helicity Injection Plasma Startup in the Pegasus ST

NASA Astrophysics Data System (ADS)

Burke, M. G.; Barr, J. L.; Bongard, M. W.; Fonck, R. J.; Hinson, E. T.; Perry, J. M.; Reusch, J. A.

2015-11-01

Plasmas in the Pegasus ST are initiated either through standard, MHD stable, inductive current drive or non-solenoidal local helicity injection (LHI) current drive with strong reconnection activity, providing a rich environment to study ion dynamics. During LHI discharges, a large amount of impurity ion heating has been observed, with the passively measured impurity Ti as high as 800 eV compared to Ti ~ 60 eV and Te ~ 175 eV during standard inductive current drive discharges. In addition, non-thermal ion velocity distributions are observed and appear to be strongest near the helicity injectors. The ion heating is hypothesized to be a result of large-scale magnetic reconnection activity, as the amount of heating scales with increasing fluctuation amplitude of the dominant, edge localized, n =1 MHD mode. An approximate temporal scaling of the heating with the amplitude of higher frequency magnetic fluctuations has also been observed, with large amounts of power spectral density present at several impurity ion cyclotron frequencies. Recent experiments have focused on investigating the impurity ion heating scaling with the ion charge to mass ratio as well as the reconnecting field strength. The ion charge to mass ratio was modified by observing different impurity charge states in similar LHI plasmas while the reconnecting field strength was modified by changing the amount of injected edge current. Work supported by US DOE grant DE-FG02-96ER54375.

The harmonic impact of electric vehicle battery charging

NASA Astrophysics Data System (ADS)

Staats, Preston Trent

The potential widespread introduction of the electric vehicle (EV) presents both opportunities and challenges to the power systems engineers who will be required to supply power to EV batteries. One of the challenges associated with EV battery charging comes from the potentially high harmonic currents associated with the conversion of ac power system voltages to dc EV battery voltages. Harmonic currents lead to increased losses in distribution circuits and reduced life expectancy of such power distribution components as capacitors and transformers. Harmonic current injections also cause harmonic voltages on power distribution networks. These distorted voltages can affect power system loads and specific standards exist regulating acceptable voltage distortion. This dissertation develops and presents the theory required to evaluate the electric vehicle battery charger as a harmonic distorting load and its possible harmonic impact on various aspects of power distribution systems. The work begins by developing a method for evaluating the net harmonic current injection of a large collection of EV battery chargers which accounts for variation in the start-time and initial battery state-of-charge between individual chargers. Next, this method is analyzed to evaluate the effect of input parameter variation on the net harmonic currents predicted by the model. We then turn to an evaluation of the impact of EV charger harmonic currents on power distribution systems, first evaluating the impact of these currents on a substation transformer and then on power distribution system harmonic voltages. The method presented accounts for the uncertainty in EV harmonic current injections by modeling the start-time and initial battery state-of-charge (SOC) of an individual EV battery charger as random variables. Thus, the net harmonic current, and distribution system harmonic voltages are formulated in a stochastic framework. Results indicate that considering variation in start-time and SOC leads to reduced estimates of harmonic current injection when compared to more traditional methods that do not account for variation. Evaluation of power distribution system harmonic voltages suggests that for any power distribution network there is a definite threshold penetration of EVs, below which the total harmonic distortion of voltage exceeds 5% at an insignificant number of buses. Thus, most existing distribution systems will probably be able to accommodate the early introduction of EV battery charging without widespread harmonic voltage problems.

Charge transport in organic semiconductors.

PubMed

Bässler, Heinz; Köhler, Anna

2012-01-01

Modern optoelectronic devices, such as light-emitting diodes, field-effect transistors and organic solar cells require well controlled motion of charges for their efficient operation. The understanding of the processes that determine charge transport is therefore of paramount importance for designing materials with improved structure-property relationships. Before discussing different regimes of charge transport in organic semiconductors, we present a brief introduction into the conceptual framework in which we interpret the relevant photophysical processes. That is, we compare a molecular picture of electronic excitations against the Su-Schrieffer-Heeger semiconductor band model. After a brief description of experimental techniques needed to measure charge mobilities, we then elaborate on the parameters controlling charge transport in technologically relevant materials. Thus, we consider the influences of electronic coupling between molecular units, disorder, polaronic effects and space charge. A particular focus is given to the recent progress made in understanding charge transport on short time scales and short length scales. The mechanism for charge injection is briefly addressed towards the end of this chapter.

Ducted fuel injection

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mueller, Charles J.

Various technologies presented herein relate to enhancing mixing inside a combustion chamber to form one or more locally premixed mixtures comprising fuel and charge-gas with low peak fuel to charge-gas ratios to enable minimal, or no, generation of soot and other undesired emissions during ignition and subsequent combustion of the locally premixed mixtures. To enable sufficient mixing of the fuel and charge-gas, a jet of fuel can be directed to pass through a bore of a duct causing charge-gas to be drawn into the bore creating turbulence to mix the fuel and the drawn charge-gas. The duct can be locatedmore » proximate to an opening in a tip of a fuel injector. The duct can comprise of one or more holes along its length to enable charge-gas to be drawn into the bore, and further, the duct can cool the fuel and/or charge-gas prior to combustion.« less

Redesign of negatively charged 111In-DTPA-octreotide derivative to reduce renal radioactivity.

PubMed

Oshima, Nobuhiro; Akizawa, Hiromichi; Kawashima, Hidekazu; Zhao, Songji; Zhao, Yan; Nishijima, Ken-Ichi; Kitamura, Yoji; Arano, Yasushi; Kuge, Yuji; Ohkura, Kazue

2017-05-01

Radiolabeled octreotide derivatives have been studied as diagnostic and therapeutic agents for somatostatin receptor-positive tumors. To prevent unnecessary radiation exposure during their clinical application, the present study aimed to develop radiolabeled peptides which could reduce radioactivity levels in the kidney at both early and late post-injection time points by introducing a negative charge with an acidic amino acid such as L-aspartic acid (Asp) at a suitable position in 111 In-DTPA-conjugated octreotide derivatives. Biodistribution of the radioactivity was evaluated in normal mice after administration of a novel radiolabeled peptide by a counting method. The radiolabeled species remaining in the kidney were identified by comparing their HPLC data with those obtained by alternative synthesis. The designed and synthesized radiolabeled peptide 111 In-DTPA-d-Phe -1 -Asp 0 -d-Phe 1 -octreotide exhibited significantly lower renal radioactivity levels than those of the known 111 In-DTPA-d-Phe 1 -octreotide at 3 and 24h post-injection. The radiolabeled species in the kidney at 24h after the injection of new octreotide derivative represented 111 In-DTPA-d-Phe-OH and 111 In-DTPA-d-Phe-Asp-OH as the metabolites. Their radiometabolites and intact 111 In-DTPA-conjugated octreotide derivative were observed in urine within 24h post-injection. The present study provided a new example of an 111 In-DTPA-conjugated octreotide derivative having the characteristics of both reduced renal uptake and shortened residence time of radioactivity in the kidney. It is considered that this kinetic control was achieved by introducing a negative charge on the octreotide derivative thereby suppressing the reabsorption in the renal tubules and affording the radiometabolites with appropriate lipophilicity. Copyright © 2017 Elsevier Inc. All rights reserved.

Microscopic studies of the fate of charges in organic semiconductors: Scanning Kelvin probe measurements of charge trapping, transport, and electric fields in p- and n-type devices

NASA Astrophysics Data System (ADS)

Smieska, Louisa Marion

Organic semiconductors could have wide-ranging applications in lightweight, efficient electronic circuits. However, several fundamental questions regarding organic electronic device behavior have not yet been fully addressed, including the nature of chemical charge traps, and robust models for injection and transport. Many studies focus on engineering devices through bulk transport measurements, but it is not always possible to infer the microscopic behavior leading to the observed measurements. In this thesis, we present scanning-probe microscope studies of organic semiconductor devices in an effort to connect local properties with local device behavior. First, we study the chemistry of charge trapping in pentacene transistors. Working devices are doped with known pentacene impurities and the extent of charge trap formation is mapped across the transistor channel. Trap-clearing spectroscopy is employed to measure an excitation of the pentacene charge trap species, enabling identification of the degradationrelated chemical trap in pentacene. Second, we examine transport and trapping in peryelene diimide (PDI) transistors. Local mobilities are extracted from surface potential profiles across a transistor channel, and charge injection kinetics are found to be highly sensitive to electrode cleanliness. Trap-clearing spectra generally resemble PDI absorption spectra, but one derivative yields evidence indicating variation in trap-clearing mechanisms for different surface chemistries. Trap formation rates are measured and found to be independent of surface chemistry, contradicting a proposed silanol trapping mechanism. Finally, we develop a variation of scanning Kelvin probe microscopy that enables measurement of electric fields through a position modulation. This method avoids taking a numeric derivative of potential, which can introduce high-frequency noise into the electric field signal. Preliminary data is presented, and the theoretical basis for electric field noise in both methods is examined.

Theoretical investigation of the charge-transfer properties in different meso-linked zinc porphyrins for highly efficient dye-sensitized solar cells.

PubMed

Namuangruk, Supawadee; Sirithip, Kanokkorn; Rattanatwan, Rattanawelee; Keawin, Tinnagon; Kungwan, Nawee; Sudyodsuk, Taweesak; Promarak, Vinich; Surakhot, Yaowarat; Jungsuttiwong, Siriporn

2014-06-28

The charge transfer effect of different meso-substituted linkages on porphyrin analogue 1 (A1, B1 and C1) was theoretically investigated using density functional theory (DFT) and time-dependent DFT (TDDFT) calculations. The calculated geometry parameters and natural bond orbital analysis reveal that the twisted conformation between porphyrin macrocycle and meso-substituted linkages leads to blocking of the conjugation of the conjugated backbone, and the frontier molecular orbital plot shows that the intramolecular charge transfer of A1, B1 and C1 hardly takes place. In an attempt to improve the photoinduced intramolecular charge transfer ability of the meso-linked zinc porphyrin sensitizer, a strong electron-withdrawing group (CN) was introduced into the anchoring group of analogue 1 forming analogue 2 (A2, B2 and C2). The density difference plot of A2, B2 and C2 shows that the charge transfer properties dramatically improved. The electron injection process has been performed using TDDFT; the direct charge-transfer transition in the A2-(TiO2)38 interacting system takes place; our results strongly indicated that introducing electron-withdrawing groups into the acceptor part of porphyrin dyes can fine-tune the effective conjugation length of the π-spacer and improve intramolecular charge transfer properties, consequently inducing the electron injection process from the anchoring group of the porphyrin dye to the (TiO2)38 surface which may improve the conversion efficiency of the DSSCs. Our calculated results can provide valuable information and a promising outlook for computation-aided sensitizer design with anticipated good properties in further experimental synthesis.

Current injection and transport in polyfluorene

NASA Astrophysics Data System (ADS)

Yang, Chieh-Kai; Yang, Chia-Ming; Liao, Hua-Hsien; Horng, Sheng-Fu; Meng, Hsin-Fei

2007-08-01

A comprehensive numerical model is established for the electrical processes in a sandwich organic semiconductor device with high carrier injection barrier. The charge injection at the anode interface with 0.8eV energy barrier is dominated by the hopping among the gap states of the semiconductor caused by disorders. The Ohmic behavior at low voltage is demonstrated to be not due to the background doping but the filaments formed by conductive clusters. In bipolar devices with low work function cathode it is shown that near the anode the electron traps significantly enhance hole injection through Fowler-Nordheim tunneling, resulting in rapid increases of the hole carrier and current in comparison with the hole-only devices.

Apparatus and method for recharging a string a avalanche transistors within a pulse generator

DOEpatents

Fulkerson, E. Stephen

2000-01-01

An apparatus and method for recharging a string of avalanche transistors within a pulse generator is disclosed. A plurality of amplification stages are connected in series. Each stage includes an avalanche transistor and a capacitor. A trigger signal, causes the apparatus to generate a very high voltage pulse of a very brief duration which discharges the capacitors. Charge resistors inject current into the string of avalanche transistors at various points, recharging the capacitors. The method of the present invention includes the steps of supplying current to charge resistors from a power supply; using the charge resistors to charge capacitors connected to a set of serially connected avalanche transistors; triggering the avalanche transistors; generating a high-voltage pulse from the charge stored in the capacitors; and recharging the capacitors through the charge resistors.

CdSe quantum dot-fullerene hybrid nanocomposite for solar energy conversion: electron transfer and photoelectrochemistry.

PubMed

Bang, Jin Ho; Kamat, Prashant V

2011-12-27

The development of organic/inorganic hybrid nanocomposite systems that enable efficient solar energy conversion has been important for applications in solar cell research. Nanostructured carbon-based systems, in particular C(60), offer attractive strategies to collect and transport electrons generated in a light harvesting assembly. We have assembled CdSe-C(60) nanocomposites by chemically linking CdSe quantum dots (QDs) with thiol-functionalized C(60). The photoinduced charge separation and collection of electrons in CdSe QD-C(60) nanocomposites have been evaluated using transient absorption spectroscopy and photoelectrochemical measurements. The rate constant for electron transfer between excited CdSe QD and C(60) increased with the decreasing size of the CdSe QD (7.9 × 10(9) s(-1) (4.5 nm), 1.7 × 10(10) s(-1) (3.2 nm), and 9.0 × 10(10) s(-1) (2.6 nm)). Slower hole transfer and faster charge recombination and transport events were found to dominate over the forward electron injection process, thus limiting the deliverance of maximum power in CdSe QD-C(60)-based solar cells. The photoinduced charge separation between CdSe QDs and C(60) opens up new design strategies for developing light harvesting assemblies.

Oriented Covalent Organic Framework Film on Graphene for Robust Ambipolar Vertical Organic Field-Effect Transistor

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sun, Bing; Zhu, Chen-Hui; Liu, Yi

Periodically eclipsed π-stacking columns in two-dimensional covalent organic frameworks (2D COFs) could function as direct channel paths for charge carrier transport. Incorporating a welldefined 2D COF into organic electronic devices, however, is still a challenge. Herein, we reported the solvothermal synthesis of a COF TFPy-PPDA film on single layer graphene (SLG), which was constructed via covalent imine-type linkage by employing 1,3,6,8-tetrakis(p-formylphenyl)pyrene (TFPy) and p-phenylenediamine (PPDA) as building blocks. A vertical field-effect transistor (VFET) based on the heterostructure of COF TFPy-PPDA film and SLG shows ambipolar charge carrier behavior under lower modulating voltages. Work-function-tunable contact between SLG and COFTFPy-PPDA film andmore » suitable injection barriers of charge carriers lead to the ambipolar transport with high current density on/off ratio (>10 5) and high on-current density (>4.1 Acm -2). Interfacing 2D COF with graphene for VFET could shed the promising application prospect of 2D COFs in organic electronics and optoelectronics.« less

Charge Transfer from Carbon Nanotubes to Silicon in Flexible Carbon Nanotube/Silicon Solar Cells.

PubMed

Li, Xiaokai; Mariano, Marina; McMillon-Brown, Lyndsey; Huang, Jing-Shun; Sfeir, Matthew Y; Reed, Mark A; Jung, Yeonwoong; Taylor, André D

2017-12-01

Mechanical fragility and insufficient light absorption are two major challenges for thin flexible crystalline Si-based solar cells. Flexible hybrid single-walled carbon nanotube (SWNT)/Si solar cells are demonstrated by applying scalable room-temperature processes for the fabrication of solar-cell components (e.g., preparation of SWNT thin films and SWNT/Si p-n junctions). The flexible SWNT/Si solar cells present an intrinsic efficiency ≈7.5% without any additional light-trapping structures. By using these solar cells as model systems, the charge transport mechanisms at the SWNT/Si interface are investigated using femtosecond transient absorption. Although primary photon absorption occurs in Si, transient absorption measurements show that SWNTs also generate and inject excited charge carriers to Si. Such effects can be tuned by controlling the thickness of the SWNTs. Findings from this study could open a new pathway for designing and improving the efficiency of photocarrier generation and absorption for high-performance ultrathin hybrid SWNT/Si solar cells. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

All-printed diode operating at 1.6 GHz

PubMed Central

Sani, Negar; Robertsson, Mats; Cooper, Philip; Wang, Xin; Svensson, Magnus; Andersson Ersman, Peter; Norberg, Petronella; Nilsson, Marie; Nilsson, David; Liu, Xianjie; Hesselbom, Hjalmar; Akesso, Laurent; Fahlman, Mats; Crispin, Xavier; Engquist, Isak; Berggren, Magnus; Gustafsson, Göran

2014-01-01

Printed electronics are considered for wireless electronic tags and sensors within the future Internet-of-things (IoT) concept. As a consequence of the low charge carrier mobility of present printable organic and inorganic semiconductors, the operational frequency of printed rectifiers is not high enough to enable direct communication and powering between mobile phones and printed e-tags. Here, we report an all-printed diode operating up to 1.6 GHz. The device, based on two stacked layers of Si and NbSi2 particles, is manufactured on a flexible substrate at low temperature and in ambient atmosphere. The high charge carrier mobility of the Si microparticles allows device operation to occur in the charge injection-limited regime. The asymmetry of the oxide layers in the resulting device stack leads to rectification of tunneling current. Printed diodes were combined with antennas and electrochromic displays to form an all-printed e-tag. The harvested signal from a Global System for Mobile Communications mobile phone was used to update the display. Our findings demonstrate a new communication pathway for printed electronics within IoT applications. PMID:25002504

Oriented Covalent Organic Framework Film on Graphene for Robust Ambipolar Vertical Organic Field-Effect Transistor

DOE PAGES

Sun, Bing; Zhu, Chen-Hui; Liu, Yi; ...

2017-04-13

Periodically eclipsed π-stacking columns in two-dimensional covalent organic frameworks (2D COFs) could function as direct channel paths for charge carrier transport. Incorporating a welldefined 2D COF into organic electronic devices, however, is still a challenge. Herein, we reported the solvothermal synthesis of a COF TFPy-PPDA film on single layer graphene (SLG), which was constructed via covalent imine-type linkage by employing 1,3,6,8-tetrakis(p-formylphenyl)pyrene (TFPy) and p-phenylenediamine (PPDA) as building blocks. A vertical field-effect transistor (VFET) based on the heterostructure of COF TFPy-PPDA film and SLG shows ambipolar charge carrier behavior under lower modulating voltages. Work-function-tunable contact between SLG and COFTFPy-PPDA film andmore » suitable injection barriers of charge carriers lead to the ambipolar transport with high current density on/off ratio (>10 5) and high on-current density (>4.1 Acm -2). Interfacing 2D COF with graphene for VFET could shed the promising application prospect of 2D COFs in organic electronics and optoelectronics.« less

A numerical study on liquid charging inside electrostatic atomizers

NASA Astrophysics Data System (ADS)

Kashir, Babak; Perri, Anthony; Sankaran, Abhilash; Staszel, Christopher; Yarin, Alexander; Mashayek, Farzad

2016-11-01

The charging of the dielectric liquid inside an electrostatic atomizer is studied numerically by developing codes based on the OpenFOAM platform. Electrostatic atomization is an appealing technology in painting, fuel injection and oil coating systems due to improved particle-size distribution, enhanced controlability of droplets' trajectories and lower power consumption. The numerical study is conducted concurrently to an experimental investigation to facilitate the validation and deliver feedback for further development. The atomizer includes a pin electrode that is placed at the center of a converging chamber. The chamber orifice is located at a known distance from the electrode tip. The pin electrode is connected to a high voltage that leads to the charging of the liquid. In the present work, the theoretical foundations of separated treatment of the polarized layer and the electronuetral bulk flow are set by describing the governing equations, relevant boundary conditions and the matching condition between these two domains. The resulting split domains are solved numerically to find the distribution of velocity and electrostatic fields over the specified regions. National Science Foundation Award Number: 1505276.

Investigation of ionization-induced electron injection in a wakefield driven by laser inside a gas cell

DOE PAGES

Audet, T. L.; Hansson, M.; Lee, P.; ...

2016-02-16

Ionization-induced electron injection was investigated experimentally by focusing a driving laser pulse with a maximum normalized potential of 1.2 at different positions along the plasma density profile inside a gas cell, filled with a gas mixture composed of 99%H 2+1%N 2. Changing the laser focus position relative to the gas cell entrance controls the accelerated electron bunch properties, such as the spectrum width, maximum energy, and accelerated charge. Simulations performed using the 3D particle-in-cell code WARP with a realistic density profile give results that are in good agreement with the experimental ones. Lastly, we discuss the interest of this regimemore » for optimizing the bunch charge in a selected energy window.« less

Fuel-air mixing and distribution in a direct-injection stratified-charge rotary engine

NASA Technical Reports Server (NTRS)

Abraham, J.; Bracco, F. V.

1989-01-01

A three-dimensional model for flows and combustion in reciprocating and rotary engines is applied to a direct-injection stratified-charge rotary engine to identify the main parameters that control its burning rate. It is concluded that the orientation of the six sprays of the main injector with respect to the air stream is important to enhance vaporization and the production of flammable mixture. In particular, no spray should be in the wake of any other spray. It was predicted that if such a condition is respected, the indicated efficiency would increase by some 6 percent at higher loads and 2 percent at lower loads. The computations led to the design of a new injector tip that has since yielded slightly better efficiency gains than predicted.

Characterization of Defects in Scaled Mis Dielectrics with Variable Frequency Charge Pumping

NASA Astrophysics Data System (ADS)

Paulsen, Ronald Eugene

1995-01-01

Historically, the interface trap has been extensively investigated to determine the effects on device performance. Recently, much attention has been paid to trapping in near-interface oxide traps. Performance of high precision analog circuitry is affected by charge trapping in near-interface oxide traps which produces hysteresis, charge redistribution errors, and dielectric relaxation effects. In addition, the performance of low power digital circuitry, with reduced noise margins, may be drastically affected by the threshold voltage shifts associated with charge trapping in near -interface oxide traps. Since near-interface oxide traps may substantially alter the performance of devices, complete characterization of these defects is necessary. In this dissertation a new characterization technique, variable frequency charge pumping, is introduced which allows charge trapped at the interface to be distinguished from the charge trapped within the oxide. The new experimental technique is an extension of the charge pumping technique to low frequencies such that tunneling may occur from interface traps to near-interface oxide traps. A generalized charge pumping model, based on Shockley-Read-Hall statistics and trap-to-trap tunneling theory, has been developed which allows a more complete characterization of near-interface oxide traps. A pair of coupled differential equations governing the rate of change of occupied interface and near-interface oxide traps have been developed. Due to the experimental conditions in the charge pumping technique the equations may be decoupled, leading to an equation governing the rate of change of occupied interface traps and an equation governing the rate of change of occcupied near-interface oxide traps. Solving the interface trap equation and applying non-steady state charge dynamics leads to an interface trap component of the charge pumping current. In addition, solution to the near-interface oxide trap equation leads to an additional oxide trap component to the charge pumping current. Numerical simulations have been performed to support the analytical development of the generalized charge pumping model. By varying the frequency of the applied charge pumping waveform and monitoring the charge recombined per cycle, the contributions from interface traps may be separated from the contributions of the near-interface oxide traps. The generalized charge pumping model allows characterization of the density and spatial distribution of near-interface oxide traps from this variable frequency charge pumping technique. Characterization of interface and near-interface oxide trap generation has been performed on devices exposed to ionizing radiation, hot electron injection, and high -field/Fowler-Nordheim stressing. Finally, using SONOS nonvolatile memory devices, a framework has been established for experimentally determining not only the spatial distribution of near-interface oxide traps, but also the energetic distribution. An experimental approach, based on tri-level charge pumping, is discussed which allows the energetic distribution of near-interface oxide traps to be determined.

Cationic PLGA/Eudragit RL nanoparticles for increasing retention time in synovial cavity after intra-articular injection in knee joint.

PubMed

Kim, Sung Rae; Ho, Myoung Jin; Lee, Eugene; Lee, Joon Woo; Choi, Young Wook; Kang, Myung Joo

2015-01-01

Positively surface-charged poly(lactide-co-glycolide) (PLGA)/Eudragit RL nanoparticles (NPs) were designed to increase retention time and sustain release profile in joints after intra-articular injection, by forming micrometer-sized electrostatic aggregates with hyaluronic acid, an endogenous anionic polysaccharide found in high amounts in synovial fluid. The cationic NPs consisting of PLGA, Eudragit RL, and polyvinyl alcohol were fabricated by solvent evaporation technique. The NPs were 170.1 nm in size, with a zeta potential of 21.3 mV in phosphate-buffered saline. Hyperspectral imaging (CytoViva(®)) revealed the formation of the micrometer-sized filamentous aggregates upon admixing, due to electrostatic interaction between NPs and the polysaccharides. NPs loaded with a fluorescent probe (1,1'-dioctadecyl-3,3,3',3' tetramethylindotricarbocyanine iodide, DiR) displayed a significantly improved retention time in the knee joint, with over 50% preservation of the fluorescent signal 28 days after injection. When DiR solution was injected intra-articularly, the fluorescence levels rapidly decreased to 30% of the initial concentration within 3 days in mice. From these findings, we suggest that PLGA-based cationic NPs could be a promising tool for prolonged delivery of therapeutic agents in joints selectively.

Electrically injected visible vertical cavity surface emitting laser diodes

DOEpatents

Schneider, Richard P.; Lott, James A.

1994-01-01

Visible laser light output from an electrically injected vertical cavity surface emitting laser (VSCEL) diode is enabled by the addition of phase-matching spacer layers on either side of the active region to form the optical cavity. The spacer layers comprise InAlP which act as charge carrier confinement means. Distributed Bragg reflector layers are formed on either side of the optical cavity to act as mirrors.

Electrically injected visible vertical cavity surface emitting laser diodes

DOEpatents

Schneider, R.P.; Lott, J.A.

1994-09-27

Visible laser light output from an electrically injected vertical cavity surface emitting laser (VSCEL) diode is enabled by the addition of phase-matching spacer layers on either side of the active region to form the optical cavity. The spacer layers comprise InAlP which act as charge carrier confinement means. Distributed Bragg reflector layers are formed on either side of the optical cavity to act as mirrors. 5 figs.

Rotary engine developments at Curtiss-Wright over the past 20 years and review of general aviation engine potential. [with direct chamber injection

NASA Technical Reports Server (NTRS)

Jones, C.

1978-01-01

The development of the rotary engine as a viable power plant capable of wide application is reviewed. Research results on the stratified charge engine with direct chamber injection are included. Emission control, reduced fuel consumption, and low noise level are among the factors discussed in terms of using the rotary engine in general aviation aircraft.

A simulation study of interactions of Space-Shuttle generated electron beams with ambient plasma and neutral gas

NASA Technical Reports Server (NTRS)

1991-01-01

The object was to conduct large scale simulations of electron beams injected into space. The study of active injection of electron beams from spacecraft is important since it provides valuable insight into beam-plasma interactions and the development of current systems in the ionosphere. However, the beam injection itself is not simple, being constrained by the ability of the spacecraft to draw return current from the ambient plasma. The generation of these return currents is dependent on several factors, including the density of the ambient plasma relative to the beam density, the presence of neutrals around the spacecraft, the configuration of the spacecraft, and the motion of the spacecraft through the plasma. Two dimensional particle simulations with collisional processes included are used to show how these different and often coupled processes can be utilized to enhance beam propagation from the spacecraft. To understand the radical expansion of mechanism of an electron beam from a highly charged spacecraft, two dimensional particle in cell simulations were conducted for a high density electron beam injected parallel to magnetic fields from an isolated equipotential conductor into a cold background plasma. The simulations indicate that charge buildup at the beam stagnation point causes the beam to expand radially to the beam electron gyroradius.

Proton Injection into the Fermilab Integrable Optics Test Accelerator (IOTA)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Prebys, Eric; Antipov, Sergey; Piekarz, Henryk

The Integrable Optics Test Accelerator (IOTA) is an experimental synchrotron being built at Fermilab to test the concept of non-linear "integrable optics". These optics are based on a lattice including non-linear elements that satisfies particular conditions on the Hamiltonian. The resulting particle motion is predicted to be stable but without a unique tune. The system is therefore insensitive to resonant instabilities and can in principle store very intense beams, with space charge tune shifts larger than those which are possible in conventional linear synchrotrons. The ring will initially be tested with pencil electron beams, but this poster describes the ultimatemore » plan to install a 2.5 MeV RFQ to inject protons, which will produce tune shifts on the order of unity. Technical details will be presented, as well as simulations of protons in the ring.« less

Transient fault behavior in a microprocessor: A case study

NASA Technical Reports Server (NTRS)

Duba, Patrick

1989-01-01

An experimental analysis is described which studies the susceptibility of a microprocessor based jet engine controller to upsets caused by current and voltage transients. A design automation environment which allows the run time injection of transients and the tracing from their impact device to the pin level is described. The resulting error data are categorized by the charge levels of the injected transients by location and by their potential to cause logic upsets, latched errors, and pin errors. The results show a 3 picoCouloumb threshold, below which the transients have little impact. An Arithmetic and Logic Unit transient is most likely to result in logic upsets and pin errors (i.e., impact the external environment). The transients in the countdown unit are potentially serious since they can result in latched errors, thus causing latent faults. Suggestions to protect the processor against these errors, by incorporating internal error detection and transient suppression techniques, are also made.

Hepatitis B vaccination for injection drug users--Pierce County, Washington, 2000.

PubMed

2001-05-18

Hepatitis B vaccination has been recommended for injection drug users (IDUs) since 1982, but vaccination coverage of IDUs remains low (1), and outbreaks of hepatitis B among IDUs continue to occur. An outbreak of hepatitis B primarily among IDUs in Pierce County, Washington, detected in April 2000, included 60 cases and resulted in three deaths among IDUs co-infected with hepatitis delta virus. A program to administer hepatitis B vaccine to IDUs was implemented to control the outbreak, and the number of cases identified decreased from 13 per month in May to two cases since November. This report describes a vaccination program during which IDUs accepted hepatitis B vaccination provided free of charge in community-based settings and illustrates how effective hepatitis B vaccination programs targeted at IDUs can be implemented through collaborations between departments of health and corrections and community organizations.

Advanced diesel electronic fuel injection and turbocharging

NASA Astrophysics Data System (ADS)

Beck, N. J.; Barkhimer, R. L.; Steinmeyer, D. C.; Kelly, J. E.

1993-12-01

The program investigated advanced diesel air charging and fuel injection systems to improve specific power, fuel economy, noise, exhaust emissions, and cold startability. The techniques explored included variable fuel injection rate shaping, variable injection timing, full-authority electronic engine control, turbo-compound cooling, regenerative air circulation as a cold start aid, and variable geometry turbocharging. A Servojet electronic fuel injection system was designed and manufactured for the Cummins VTA-903 engine. A special Servojet twin turbocharger exhaust system was also installed. A series of high speed combustion flame photos was taken using the single cylinder optical engine at Michigan Technological University. Various fuel injection rate shapes and nozzle configurations were evaluated. Single-cylinder bench tests were performed to evaluate regenerative inlet air heating techniques as an aid to cold starting. An exhaust-driven axial cooling air fan was manufactured and tested on the VTA-903 engine.

Injection of electrons with predominantly perpendicular energy into an area of toroidal field ripple in a tokamak plasma to improve plasma confinement

DOEpatents

Ono, Masayuki; Furth, Harold

1993-01-01

An electron injection scheme for controlling transport in a tokamak plasma. Electrons with predominantly perpendicular energy are injected into a ripple field region created by a group of localized poloidal field bending magnets. The trapped electrons then grad-B drift vertically toward the plasma interior until they are detrapped, charging the plasma negative. Calculations indicate that the highly perpendicular velocity electrons can remain stable against kinetic instabilities in the regime of interest for tokamak experiments. The penetration distance can be controlled by controlling the "ripple mirror ratio", the energy of the injected electrons, and their v.sub..perp. /v.sub.51 ratio. In this scheme, the poloidal torque due to the injected radial current is taken by the magnets and not by the plasma. Injection is accomplished by the flat cathode containing an ECH cavity to pump electrons to high v.sub..perp..

Non-adiabatic processes in the charge transfer reaction of O{sub 2} molecules with potassium surfaces without dissociation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Krix, David; Nienhaus, Hermann, E-mail: hermann.nienhaus@uni-due.de

2014-08-21

Thin potassium films grown on Si(001) substrates are used to measure internal chemicurrents and the external emission of exoelectrons simultaneously during adsorption of molecular oxygen on K surfaces at 120 K. The experiments clarify the dynamics of electronic excitations at a simple metal with a narrow valence band. X-ray photoemission reveals that for exposures below 5 L almost exclusively peroxide K{sub 2}O{sub 2} is formed, i.e., no dissociation of the molecule occurs during interaction. Still a significant chemicurrent and a delayed exoelectron emission are detected due to a rapid injection of unoccupied molecular levels below the Fermi level. Since themore » valence band width of potassium is approximately equal to the potassium work function (2.4 eV) the underlying mechanism of exoemission is an Auger relaxation whereas chemicurrents are detected after resonant charge transfer from the metal valence band into the injected level. The change of the chemicurrent and exoemission efficiencies with oxygen coverage can be deduced from the kinetics of the reaction and the recorded internal and external emission currents traces. It is shown that the non-adiabaticity of the reaction increases with coverage due to a reduction of the electronic density of states at the surface while the work function does not vary significantly. Therefore, the peroxide formation is one of the first reaction systems which exhibits varying non-adiabaticity and efficiencies during the reaction. Non-adiabatic calculations based on model Hamiltonians and density functional theory support the picture of chemicurrent generation and explain the rapid injection of hot hole states by an intramolecular motion, i.e., the expansion of the oxygen molecule on the timescale of a quarter of a vibrational period.« less

Multifuel rotary aircraft engine

NASA Technical Reports Server (NTRS)

Jones, C.; Berkowitz, M.

1980-01-01

The broad objectives of this paper are the following: (1) to summarize the Curtiss-Wright design, development and field testing background in the area of rotary aircraft engines; (2) to briefly summarize past activity and update development work in the area of stratified charge rotary combustion engines; and (3) to discuss the development of a high-performance direct injected unthrottled stratified charge rotary combustion aircraft engine. Efficiency improvements through turbocharging are also discussed.

Advanced rotary engines

NASA Technical Reports Server (NTRS)

Jones, C.

1983-01-01

The broad objectives of this paper are the following: (1) to summarize the Curtiss-Wright design, development and field testing background in the area of rotary aircraft engines; (2) to briefly summarize past activity and update development work in the area of stratified charge rotary combustion engines; and (3) to discuss the development of a high-performance direct injected unthrottled stratified charge rotary combustion aircraft engine. Efficiency improvements through turbocharging are also discussed.

Planar-Processed Polymer Transistors.

PubMed

Xu, Yong; Sun, Huabin; Shin, Eul-Yong; Lin, Yen-Fu; Li, Wenwu; Noh, Yong-Young

2016-10-01

Planar-processed polymer transistors are proposed where the effective charge injection and the split unipolar charge transport are all on the top surface of the polymer film, showing ideal device characteristics with unparalleled performance. This technique provides a great solution to the problem of fabrication limitations, the ambiguous operating principle, and the performance improvements in practical applications of conjugated-polymer transistors. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Charge carrier dynamics investigation of CuInS2 quantum dots films using injected charge extraction by linearly increasing voltage (i-CELIV): the role of ZnS Shell

NASA Astrophysics Data System (ADS)

Bi, Ke; Sui, Ning; Zhang, Liquan; Wang, Yinghui; Liu, Qinghui; Tan, Mingrui; Zhou, Qiang; Zhang, Hanzhuang

2016-12-01

The role of ZnS shell on the photo-physical properties within CuInS2/ZnS quantum dots (QDs) is carefully studied in optoelectronic devices. Linearly increasing voltage technique has been employed to investigate the charge carrier dynamics of both CuInS2 and CuInS2/ZnS QDs films. This study shows that charge carriers follow a similar behavior of monomolecular recombination in this film, with their charge transfer rate correlates to the increase of applied voltage. It turns out that the ZnS shell could affect the carrier diffusion process through depressing the trapping states and would build up a potential barrier.

Massless charged particles: Cosmic censorship, and the third law of black hole mechanics

NASA Astrophysics Data System (ADS)

Fairoos, C.; Ghosh, Avirup; Sarkar, Sudipta

2017-10-01

The formulation of the laws of Black hole mechanics assumes the stability of black holes under perturbations in accordance with the "cosmic censorship hypothesis" (CCH). CCH prohibits the formation of a naked singularity by a physical process from a regular black hole solution with an event horizon. Earlier studies show that naked singularities can indeed be formed leading to the violation of CCH if a near-extremal black hole is injected with massive charged particles and the backreaction effects are neglected. We investigate the validity of CCH by considering the infall of charged massless particles as well as a charged null shell. We also discuss the issue of the third law of Black hole mechanics in the presence of null charged particles by considering various possibilities.

Impact of gate work-function on memory characteristics in Al2O3/HfOx/Al2O3/graphene charge-trap memory devices

NASA Astrophysics Data System (ADS)

Lee, Sejoon; Song, Emil B.; Kim, Sungmin; Seo, David H.; Seo, Sunae; Won Kang, Tae; Wang, Kang L.

2012-01-01

Graphene-based non-volatile memory devices composed of a single-layer graphene channel and an Al2O3/HfOx/Al2O3 charge-storage layer exhibit memory functionality. The impact of the gate material's work-function (Φ) on the memory characteristics is investigated using different types of metals [Ti (ΦTi = 4.3 eV) and Ni (ΦNi = 5.2 eV)]. The ambipolar carrier conduction of graphene results in an enlargement of memory window (ΔVM), which is ˜4.5 V for the Ti-gate device and ˜9.1 V for the Ni-gate device. The increase in ΔVM is attributed to the change in the flat-band condition and the suppression of electron back-injection within the gate stack.

Study on effective MOSFET channel length extracted from gate capacitance

NASA Astrophysics Data System (ADS)

Tsuji, Katsuhiro; Terada, Kazuo; Fujisaka, Hisato

2018-01-01

The effective channel length (L GCM) of metal-oxide-semiconductor field-effect transistors (MOSFETs) is extracted from the gate capacitances of actual-size MOSFETs, which are measured by charge-injection-induced-error-free charge-based capacitance measurement (CIEF CBCM). To accurately evaluate the capacitances between the gate and the channel of test MOSFETs, the parasitic capacitances are removed by using test MOSFETs having various channel sizes and a source/drain reference device. A strong linear relationship between the gate-channel capacitance and the design channel length is obtained, from which L GCM is extracted. It is found that L GCM is slightly less than the effective channel length (L CRM) extracted from the measured MOSFET drain current. The reason for this is discussed, and it is found that the capacitance between the gate electrode and the source and drain regions affects this extraction.

A Compact Nuclear Fusion Reactor for Space Flights

NASA Astrophysics Data System (ADS)

Nastoyashchiy, Anatoly F.

2006-05-01

A small-scale nuclear fusion reactor is suggested based on the concepts of plasma confinement (with a high pressure gas) which have been patented by the author. The reactor considered can be used as a power setup in space flights. Among the advantages of this reactor is the use of a D3He fuel mixture which at burning gives main reactor products — charged particles. The energy balance considerably improves, as synchrotron radiation turn out "captured" in the plasma volume, and dangerous, in the case of classical magnetic confinement, instabilities in the direct current magnetic field configuration proposed do not exist. As a result, the reactor sizes are quite suitable (of the order of several meters). A possibility of making reactive thrust due to employment of ejection of multiply charged ions formed at injection of pellets from some adequate substance into the hot plasma center is considered.

Deceleration, precooling, and multi-pass stopping of highly charged ions in Be{sup +} Coulomb crystals

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schmöger, L., E-mail: lisa.schmoeger@mpi-hd.mpg.de; Schwarz, M.; Versolato, O. O.

2015-10-15

Preparing highly charged ions (HCIs) in a cold and strongly localized state is of particular interest for frequency metrology and tests of possible spatial and temporal variations of the fine structure constant. Our versatile preparation technique is based on the generic modular combination of a pulsed ion source with a cryogenic linear Paul trap. Both instruments are connected by a compact beamline with deceleration and precooling properties. We present its design and commissioning experiments regarding these two functionalities. A pulsed buncher tube allows for the deceleration and longitudinal phase-space compression of the ion pulses. External injection of slow HCIs, specificallymore » Ar{sup 13+}, into the linear Paul trap and their subsequent retrapping in the absence of sympathetic cooling is demonstrated. The latter proved to be a necessary prerequisite for the multi-pass stopping of HCIs in continuously laser-cooled Be{sup +} Coulomb crystals.« less

Strong correlation induced charge localization in antiferromagnets

PubMed Central

Zhu, Zheng; Jiang, Hong-Chen; Qi, Yang; Tian, Chushun; Weng, Zheng-Yu

2013-01-01

The fate of a hole injected in an antiferromagnet is an outstanding issue of strongly correlated physics. It provides important insights into doped Mott insulators closely related to high-temperature superconductivity. Here, we report a systematic numerical study of t-J ladder systems based on the density matrix renormalization group. It reveals a surprising result for the single hole's motion in an otherwise well-understood undoped system. Specifically, we find that the common belief of quasiparticle picture is invalidated by the self-localization of the doped hole. In contrast to Anderson localization caused by disorders, the charge localization discovered here is an entirely new phenomenon purely of strong correlation origin. It results from destructive quantum interference of novel signs picked up by the hole, and since the same effect is of a generic feature of doped Mott physics, our findings unveil a new paradigm which may go beyond the single hole doped system. PMID:24002668

Ultra-high gain diffusion-driven organic transistor.

PubMed

Torricelli, Fabrizio; Colalongo, Luigi; Raiteri, Daniele; Kovács-Vajna, Zsolt Miklós; Cantatore, Eugenio

2016-02-01

Emerging large-area technologies based on organic transistors are enabling the fabrication of low-cost flexible circuits, smart sensors and biomedical devices. High-gain transistors are essential for the development of large-scale circuit integration, high-sensitivity sensors and signal amplification in sensing systems. Unfortunately, organic field-effect transistors show limited gain, usually of the order of tens, because of the large contact resistance and channel-length modulation. Here we show a new organic field-effect transistor architecture with a gain larger than 700. This is the highest gain ever reported for organic field-effect transistors. In the proposed organic field-effect transistor, the charge injection and extraction at the metal-semiconductor contacts are driven by the charge diffusion. The ideal conditions of ohmic contacts with negligible contact resistance and flat current saturation are demonstrated. The approach is general and can be extended to any thin-film technology opening unprecedented opportunities for the development of high-performance flexible electronics.

Ultra-high gain diffusion-driven organic transistor

NASA Astrophysics Data System (ADS)

Torricelli, Fabrizio; Colalongo, Luigi; Raiteri, Daniele; Kovács-Vajna, Zsolt Miklós; Cantatore, Eugenio

2016-02-01

Emerging large-area technologies based on organic transistors are enabling the fabrication of low-cost flexible circuits, smart sensors and biomedical devices. High-gain transistors are essential for the development of large-scale circuit integration, high-sensitivity sensors and signal amplification in sensing systems. Unfortunately, organic field-effect transistors show limited gain, usually of the order of tens, because of the large contact resistance and channel-length modulation. Here we show a new organic field-effect transistor architecture with a gain larger than 700. This is the highest gain ever reported for organic field-effect transistors. In the proposed organic field-effect transistor, the charge injection and extraction at the metal-semiconductor contacts are driven by the charge diffusion. The ideal conditions of ohmic contacts with negligible contact resistance and flat current saturation are demonstrated. The approach is general and can be extended to any thin-film technology opening unprecedented opportunities for the development of high-performance flexible electronics.

Investigation on the Characteristics of Pellet Ablation in a Toroidal Plasma

NASA Astrophysics Data System (ADS)

Sato, K. N.; Sakakita, H.; Fujita, H.

2003-06-01

Characteristics of a cloud ablated from an ice pellet has been investigated in detail in the JIPP T-IIU tokamak plasma by utilizing a new scheme of pellet injection system, "the injection-angle controllable system". A long "helical tail" of ablation light has been observed using CCD cameras and a high speed framing photograph in the case of on-axis and off-axis injection with the injection angle smaller than a certain value. The direction of the helical tail is found to be independent to that of the total magnetic field lines of the torus. From the experiments with the combination of two toroildal filed directions and two plasma current directions, it is considered that the tail seems to rotate, in most cases, to the electron diamagnetic direction poloidally, and to the opposite to the plasma current direction toroidally. Consideration on various cross sections including charge exchange, ionization and elastic collisions leads us to the conclusion that the tail-shaped phenomena may come from the situation of charge exchange equilibrium of hydrogen ions and neutrals at extremely high density regime in the cloud. The relation of ablation behavior with plasma potential and rotation has also been studied. Potential measurements of pellet-injected plasmas using heavy ion beam probe (HIBP) method were carried out for the first time. In the case of an injection angle to be anti-parallel to the electron diamagnetic direction in the poloidal plane, the result shows that the direction of potential change is negative, and consequently the potential after the injection should be negative because it has been measured to be negative in usual ohmic plasmas without pellet injection. Thus, the direction of the "tail" structure seems to be consistent to that of the plasma potential measured, if it is considered that tail structure may be caused by the effect of the plasma potential and the rotation.

Three-dimensional finite amplitude electroconvection in dielectric liquids

NASA Astrophysics Data System (ADS)

Luo, Kang; Wu, Jian; Yi, Hong-Liang; Tan, He-Ping

2018-02-01

Charge injection induced electroconvection in a dielectric liquid lying between two parallel plates is numerically simulated in three dimensions (3D) using a unified lattice Boltzmann method (LBM). Cellular flow patterns and their subcritical bifurcation phenomena of 3D electroconvection are numerically investigated for the first time. A unit conversion is also derived to connect the LBM system to the real physical system. The 3D LBM codes are validated by three carefully chosen cases and all results are found to be highly consistent with the analytical solutions or other numerical studies. For strong injection, the steady state roll, polygon, and square flow patterns are observed under different initial disturbances. Numerical results show that the hexagonal cell with the central region being empty of charge and centrally downward flow is preferred in symmetric systems under random initial disturbance. For weak injection, the numerical results show that the flow directly passes from the motionless state to turbulence once the system loses its linear stability. In addition, the numerically predicted linear and finite amplitude stability criteria of different flow patterns are discussed.

Ultrafast Recombination Dynamics in Dye-Sensitized SnO2/TiO2 Core/Shell Films.

PubMed

Gish, Melissa K; Lapides, Alexander M; Brennaman, M Kyle; Templeton, Joseph L; Meyer, Thomas J; Papanikolas, John M

2016-12-15

Interfacial dynamics are investigated in SnO 2 /TiO 2 core/shell films derivatized with a Ru(II)-polypyridyl chromophore ([Ru II (bpy) 2 (4,4'-(PO 3 H 2 ) 2 bpy)] 2+ , RuP) using transient absorption methods. Electron injection from the chromophore into the TiO 2 shell occurs within a few picoseconds after photoexcitation. Loss of the oxidized dye through recombination occurs across time scales spanning 10 orders of magnitude. The majority (60%) of charge recombination events occur shortly after injection (τ = 220 ps), while a small fraction (≤20%) of the oxidized chromophores persists for milliseconds. The lifetime of long-lived charge-separated states (CSS) depends exponentially on shell thickness, suggesting that the injected electrons reside in the SnO 2 core and must tunnel through the TiO 2 shell to recombine with oxidized dyes. While the core/shell architecture extends the lifetime in a small fraction of the CSS, making water oxidation possible, the subnanosecond recombination process has profound implications for the overall efficiencies of dye-sensitized photoelectrosynthesis cells (DSPECs).

Contact engineering for efficient charge injection in organic transistors with low-cost metal electrodes

NASA Astrophysics Data System (ADS)

Panigrahi, D.; Kumar, S.; Dhar, A.

2017-10-01

Controlling charge injection at the metal-semiconductor interface is very crucial for organic electronic devices in general as it can significantly influence the overall device performance. Herein, we report a facile, yet efficient contact modification approach, to enhance the hole injection efficiency through the incorporation of a high vacuum deposited TPD [N,N'-Bis(3-methylphenyl)-N,N'-diphenylbenzidine] interlayer between the electrodes and the active semiconducting layer. The device performance parameters such as mobility and on/off ratio improved significantly after the inclusion of the TPD buffer layer, and more interestingly, the devices with cost effective Ag and Cu electrodes were able to exhibit a superior device performance than the typically used Au source-drain devices. We have also observed that this contact modification technique can be even more effective than commonly used metal oxide interface modifying layers. Our investigations demonstrate the efficacy of the TPD interlayer in effectively reducing the interfacial contact resistance through the modification of pentacene energy levels, which consequently results in the substantial improvement in the device performances.

Reprint of : Hanbury-Brown Twiss noise correlation with time controlled quasi-particles in ballistic quantum conductors

NASA Astrophysics Data System (ADS)

Glattli, D. C.; Roulleau, P.

2016-08-01

We study the Hanbury Brown and Twiss correlation of electronic quasi-particles injected in a quantum conductor using current noise correlations and we experimentally address the effect of finite temperature. By controlling the relative time of injection of two streams of electrons it is possible to probe the fermionic antibunching, performing the electron analog of the optical Hong Ou Mandel (HOM) experiment. The electrons are injected using voltage pulses with either sine-wave or Lorentzian shape. In the latter case, we propose a set of orthogonal wavefunctions, describing periodic trains of multiply charged electron pulses, which give a simple interpretation to the HOM shot noise. The effect of temperature is then discussed and experimentally investigated. We observe a perfect electron anti-bunching for a large range of temperature, showing that, as recently predicted, thermal mixing of the states does not affect anti-bunching properties, a feature qualitatively different from dephasing. For single charge Lorentzian pulses, we provide experimental evidence of the prediction that the HOM shot noise variation versus the emission time delay is remarkably independent of the temperature.

Chronic intracortical microstimulation (ICMS) of cat sensory cortex using the Utah Intracortical Electrode Array.

PubMed

Rousche, P J; Normann, R A

1999-03-01

In an effort to assess the safety and efficacy of focal intracortical microstimulation (ICMS) of cerebral cortex with an array of penetrating electrodes as might be applied to a neuroprosthetic device to aid the deaf or blind, we have chronically implanted three trained cats in primary auditory cortex with the 100-electrode Utah Intracortical Electrode Array (UIEA). Eleven of the 100 electrodes were hard-wired to a percutaneous connector for chronic access. Prior to implant, cats were trained to "lever-press" in response to pure tone auditory stimulation. After implant, this behavior was transferred to "lever-presses" in response to current injections via single electrodes of the implanted arrays. Psychometric function curves relating injected charge level to the probability of response were obtained for stimulation of 22 separate electrodes in the three implanted cats. The average threshold charge/phase required for electrical stimulus detection in each cat was, 8.5, 8.6, and 11.6 nC/phase respectively, with a maximum charge/phase of 26 nC/phase and a minimum of 1.5 nC/phase thresholds were tracked for varying time intervals, and seven electrodes from two cats were tracked for up to 100 days. Electrodes were stimulated for no more than a few minutes each day. Neural recordings taken from the same electrodes before and after multiple electrical stimulation sessions were very similar in signal/noise ratio and in the number of recordable units, suggesting that the range of electrical stimulation levels used did not damage neurons in the vicinity of the electrodes. Although a few early implants failed, we conclude that ICMS of cerebral cortex to evoke a behavioral response can be achieved with the penetrating UIEA. Further experiments in support of a sensory cortical prosthesis based on ICMS are warranted.

SIMULATIONS OF TRANSVERSE STACKING IN THE NSLS-II BOOSTER

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fliller III, R.; Shaftan, T.

2011-03-28

The NSLS-II injection system consists of a 200 MeV linac and a 3 GeV booster. The linac needs to deliver 15 nC in 80 - 150 bunches to the booster every minute to achieve current stability goals in the storage ring. This is a very stringent requirement that has not been demonstrated at an operating light source. We have developed a scheme to transversely stack two bunch trains in the NSLS-II booster in order to alleviate the charge requirements on the linac. This scheme has been outlined previously. In this paper we show particle tracking simulations of the tracking scheme.more » We show simulations of the booster ramp with a stacked beam for a variety of lattice errors and injected beam parameters. In all cases the performance of the proposed stacking method is sufficient to reduce the required charge from the linac. For this reason the injection system of the NSLS-II booster is being designed to include this feature. The NSLS-II injection system consists of a 200 MeV linac and a 3 GeV booster. The injectors must provide 7.5nC in bunch trains 80-150 bunches long every minute for top off operation of the storage ring. Top off then requires that the linac deliver 15nC of charge once losses in the injector chain are taken into consideration. This is a very stringent requirement that has not been demonstrated at an operating light source. For this reason we have developed a method to transversely stack two bunch trains in the booster while maintaining the charge transport efficiency. This stacking scheme has been discussed previously. In this paper we show the simulations of the booster ramp with a single bunch train in the booster. Then we give a brief overview of the stacking scheme. Following, we show the results of stacking two bunch trains in the booster with varying beam emittances and train separations. The behavior of the beam through the ramp is examined showing that it is possible to stack two bunch trains in the booster.« less

POLAR 5 - An electron accelerator experiment within an aurora. III - Evidence for significant spacecraft charging by an electron accelerator at ionospheric altitudes

NASA Technical Reports Server (NTRS)

Jacobsen, T. A.; Maynard, N. C.

1980-01-01

The POLAR 5 rocket experiment carried an electron accelerator on a 'daughter' payload which injected a 0.1 A beam of 10 keV electrons in a pulsed mode every 410 ms. With spin and precession, injections were made over a wide range of pitch angles. Measurements from a double probe electric field instrument and from particle detectors on the 'mother' payload and from a crude RPA on the 'daughter' payload are interpreted to indicate that the 'daughter' charges to a potential between several hundred volts and 1 kV. The neutralizing return current to the 'daughter' is shown to be asymmetrically distributed with the majority being collected from the direction of the beam. The additional electrons necessary to neutralize the daughter are thought to be produced and heated through beam-plasma interactions postulated by Maehlum et al. (1980) and Grandal et al. (1980) to explain the particle and optical measurements. Significant electric fields emanating from the charged 'daughter' and the beam are seen at distances exceeding 100 m at the 'mother' payload.

Fast imaging measurements and modeling of neutral and impurity density on C-2U

NASA Astrophysics Data System (ADS)

Granstedt, Erik; Deng, B.; Dettrick, S.; Gupta, D. K.; Osin, D.; Roche, T.; Zhai, K.; TAE Team

2016-10-01

The C-2U device employed neutral beam injection and end-biasing to sustain an advanced beam-driven Field-Reversed Configuration plasma for 5+ ms, beyond characteristic transport time-scales. Three high-speed, filtered cameras observed visible light emission from neutral hydrogen and impurities, as well as deuterium pellet ablation and compact-toroid injection which were used for auxiliary particle fueling. Careful vacuum practices and titanium gettering successfully reduced neutral recycling from the confinement vessel wall. As a result, a large fraction of the remaining neutrals originate from charge-exchange between the neutral beams and plasma ions. Measured H/D- α emission is used with DEGAS2 neutral particle modeling to reconstruct the strongly non-axissymmetric neutral distribution. This is then used in fast-ion modeling to more accurately estimate their charge-exchange loss rate. Oxygen emission due to electron-impact excitation and charge-exchange recombination has also been measured using fast imaging. Reconstructed emissivity of O4+ is localized on the outboard side of the core plasma near the estimated location of the separatrix inferred by external magnetic measurements. Tri Alpha Energy.

Development of a repetitive compact torus injector

NASA Astrophysics Data System (ADS)

Onchi, Takumi; McColl, David; Dreval, Mykola; Rohollahi, Akbar; Xiao, Chijin; Hirose, Akira; Zushi, Hideki

2013-10-01

A system for Repetitive Compact Torus Injection (RCTI) has been developed at the University of Saskatchewan. CTI is a promising fuelling technology to directly fuel the core region of tokamak reactors. In addition to fuelling, CTI has also the potential for (a) optimization of density profile and thus bootstrap current and (b) momentum injection. For steady-state reactor operation, RCTI is necessary. The approach to RCTI is to charge a storage capacitor bank with a large capacitance and quickly charge the CT capacitor bank through a stack of integrated-gate bipolar transistors (IGBTs). When the CT bank is fully charged, the IGBT stack will be turned off to isolate banks, and CT formation/acceleration sequence will start. After formation of each CT, the fast bank will be replenished and a new CT will be formed and accelerated. Circuits for the formation and the acceleration in University of Saskatchewan CT Injector (USCTI) have been modified. Three CT shots at 10 Hz or eight shots at 1.7 Hz have been achieved. This work has been sponsored by the CRC and NSERC, Canada.

High intensity high charge state ion beam production with an evaporative cooling magnet ECRIS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lu, W., E-mail: luwang@impcas.ac.cn; Qian, C.; Sun, L. T.

2016-02-15

LECR4 (Lanzhou ECR ion source No. 4) is a room temperature electron cyclotron resonance ion source, designed to produce high current, high charge state ion beams for the SSC-LINAC injector (a new injector for sector separated cyclotron) at the Institute of Modern Physics. LECR4 also serves as a PoP machine for the application of evaporative cooling technology in accelerator field. To achieve those goals, LECR4 ECR ion source has been optimized for the operation at 18 GHz. During 2014, LECR4 ion source was commissioned at 18 GHz microwave of 1.6 kW. To further study the influence of injection stage tomore » the production of medium and high charge state ion beams, in March 2015, the injection stage with pumping system was installed, and some optimum results were produced, such as 560 eμA of O{sup 7+}, 620 eμA of Ar{sup 11+}, 430 eμA of Ar{sup 12+}, 430 eμA of Xe{sup 20+}, and so on. The comparison will be discussed in the paper.« less

Street Policing, Injecting Drug Use and Harm Reduction in a Russian City: A Qualitative Study of Police Perspectives

PubMed Central

Platt, Lucy; Sarang, Anya; Vlasov, Alexander; Mikhailova, Larissa; Monaghan, Geoff

2006-01-01

We undertook a qualitative exploration of police perspectives on injecting drug use and needle and syringe access among injecting drug users (IDUs) in a Russian city which has witnessed explosive spread of HIV associated with drug injecting. Twenty-seven in-depth qualitative interviews were conducted in May 2002 with police officers of varying rank who reported having regular contact with IDUs. All interviews were tape-recorded, transcribed, translated and coded thematically. Accounts upheld an approach to policing which emphasised high street-based visibility and close surveillance of IDUs. IDUs were depicted as ‘potential criminals’ warranting a ‘pre-emptive’ approach to the prevention of drug-related crime. Street policing was described as a means of maintaining close surveillance leading to the official registration of persons suspected or proven to be users of illicit drugs. Such registration enabled further ongoing surveillance, including through stop and search procedures. While aware of drug users' reluctance to carry injecting equipment linked to their fears of detention or arrest, accounts suggested that the confiscation of previously used injecting equipment can constitute evidence in relation to drugs possession charges and that discovery of clean injecting equipment may be sufficient to raise suspicion and/or further investigation, including through stop and search or questioning. Our findings suggest an uneasy relationship between street policing and needle and syringe access, whereby policing strategies can undermine an HIV prevention ethos promoting needle and syringe accessibility among IDUs. We conclude that facilitating partnerships between policing agencies and HIV prevention initiatives are a critical feature of creating environments conducive for risk reduction. PMID:16855880

Improved electron injection in all-solution-processed n-type organic field-effect transistors with an inkjet-printed ZnO electron injection layer

NASA Astrophysics Data System (ADS)

Roh, Jeongkyun; Kim, Hyeok; Park, Myeongjin; Kwak, Jeonghun; Lee, Changhee

2017-10-01

Interface engineering for the improved injection properties of all-solution-processed n-type organic field-effect transistors (OFETs) arising from the use of an inkjet-printed ZnO electron injection layer were demonstrated. The characteristics of ZnO in terms of electron injection and transport were investigated, and then we employed ZnO as the electron injection layer via inkjet-printing during the fabrication of all-solution-processed, n-type OFETs. With the inkjet-printed ZnO electron injection layer, the devices exhibited approximately five-fold increased mobility (0.0058 cm2/V s to 0.030 cm2/V s), more than two-fold increased charge concentration (2.76 × 1011 cm-2 to 6.86 × 1011 cm-2), and two orders of magnitude reduced device resistance (120 MΩ cm to 3 MΩ cm). Moreover, n-type polymer form smoother film with ZnO implying denser packing of polymer, which results in higher mobility.

Charge transport model in solid-state avalanche amorphous selenium and defect suppression design

NASA Astrophysics Data System (ADS)

Scheuermann, James R.; Miranda, Yesenia; Liu, Hongyu; Zhao, Wei

2016-01-01

Avalanche amorphous selenium (a-Se) in a layer of High Gain Avalanche Rushing Photoconductor (HARP) is being investigated for its use in large area medical imagers. Avalanche multiplication of photogenerated charge requires electric fields greater than 70 V μm-1. For a-Se to withstand this high electric field, blocking layers are used to prevent the injection of charge carriers from the electrodes. Blocking layers must have a high injection barrier and deep trapping states to reduce the electric field at the interface. In the presence of a defect in the blocking layer, a distributed resistive layer (DRL) must be included into the structure to build up space charge and reduce the electric field in a-Se and the defect. A numerical charge transport model has been developed to optimize the properties of blocking layers used in various HARP structures. The model shows the incorporation of a DRL functionality into the p-layer can reduce dark current at a point defect by two orders of magnitude by reducing the field in a-Se to the avalanche threshold. Hole mobility in a DRL of ˜10-8 cm2 V-1 s-1 at 100 V μm-1 as demonstrated by the model can be achieved experimentally by varying the hole mobility of p-type organic or inorganic semiconductors through doping, e.g., using Poly(9-vinylcarbozole) doped with 1%-3% (by weight) of poly(3-hexylthiopene).