Tensile strained Ge tunnel field-effect transistors: k · p material modeling and numerical device simulation

International Nuclear Information System (INIS)

Kao, Kuo-Hsing; De Meyer, Kristin; Verhulst, Anne S.; Van de Put, Maarten; Soree, Bart; Magnus, Wim; Vandenberghe, William G.

2014-01-01

Group IV based tunnel field-effect transistors generally show lower on-current than III-V based devices because of the weaker phonon-assisted tunneling transitions in the group IV indirect bandgap materials. Direct tunneling in Ge, however, can be enhanced by strain engineering. In this work, we use a 30-band k · p method to calculate the band structure of biaxial tensile strained Ge and then extract the bandgaps and effective masses at Γ and L symmetry points in k-space, from which the parameters for the direct and indirect band-to-band tunneling (BTBT) models are determined. While transitions from the heavy and light hole valence bands to the conduction band edge at the L point are always bridged by phonon scattering, we highlight a new finding that only the light-hole-like valence band is strongly coupling to the conduction band at the Γ point even in the presence of strain based on the 30-band k · p analysis. By utilizing a Technology Computer Aided Design simulator equipped with the calculated band-to-band tunneling BTBT models, the electrical characteristics of tensile strained Ge point and line tunneling devices are self-consistently computed considering multiple dynamic nonlocal tunnel paths. The influence of field-induced quantum confinement on the tunneling onset is included. Our simulation predicts that an on-current up to 160 (260) μA/μm can be achieved along with on/off ratio > 10 6 for V DD  = 0.5 V by the n-type (p-type) line tunneling device made of 2.5% biaxial tensile strained Ge

Tensile strained Ge tunnel field-effect transistors: k · p material modeling and numerical device simulation

Energy Technology Data Exchange (ETDEWEB)

Kao, Kuo-Hsing; De Meyer, Kristin [IMEC, Kapeldreef 75, 3001 Leuven (Belgium); Department of Electrical Engineering, Katholieke Universiteit Leuven, 3000 Leuven (Belgium); Verhulst, Anne S. [IMEC, Kapeldreef 75, 3001 Leuven (Belgium); Van de Put, Maarten; Soree, Bart; Magnus, Wim [IMEC, Kapeldreef 75, 3001 Leuven (Belgium); Department of Physics, Universiteit Antwerpen, 2000 Antwerpen (Belgium); Vandenberghe, William G. [Department of Materials Science and Engineering, University of Texas at Dallas, Richardson, Texas 75080 (United States)

2014-01-28

Group IV based tunnel field-effect transistors generally show lower on-current than III-V based devices because of the weaker phonon-assisted tunneling transitions in the group IV indirect bandgap materials. Direct tunneling in Ge, however, can be enhanced by strain engineering. In this work, we use a 30-band k · p method to calculate the band structure of biaxial tensile strained Ge and then extract the bandgaps and effective masses at Γ and L symmetry points in k-space, from which the parameters for the direct and indirect band-to-band tunneling (BTBT) models are determined. While transitions from the heavy and light hole valence bands to the conduction band edge at the L point are always bridged by phonon scattering, we highlight a new finding that only the light-hole-like valence band is strongly coupling to the conduction band at the Γ point even in the presence of strain based on the 30-band k · p analysis. By utilizing a Technology Computer Aided Design simulator equipped with the calculated band-to-band tunneling BTBT models, the electrical characteristics of tensile strained Ge point and line tunneling devices are self-consistently computed considering multiple dynamic nonlocal tunnel paths. The influence of field-induced quantum confinement on the tunneling onset is included. Our simulation predicts that an on-current up to 160 (260) μA/μm can be achieved along with on/off ratio > 10{sup 6} for V{sub DD} = 0.5 V by the n-type (p-type) line tunneling device made of 2.5% biaxial tensile strained Ge.

Flexible spintronic devices on Kapton

DEFF Research Database (Denmark)

Bedoya-Pinto, Amilcar; Donolato, Marco; Gobbi, Marco

2014-01-01

Magnetic tunnel junctions and nano-sized domain-wall conduits have been fabricated on the flexible substrate Kapton. Despite the delicate nature of tunneling barriers and zig-zag shaped nanowires, the devices show an outstanding integrity and robustness upon mechanical bending. High values of ben...

Tunnel splitting in biaxial spin models investigated with spin-coherent-state path integrals

International Nuclear Information System (INIS)

Chen Zhide; Liang, J.-Q.; Pu, F.-C.

2003-01-01

Tunnel splitting in biaxial spin models is investigated with a full evaluation of the fluctuation functional integrals of the Euclidean kernel in the framework of spin-coherent-state path integrals which leads to a magnitude of tunnel splitting quantitatively comparable with the numerical results in terms of diagonalization of the Hamilton operator. An additional factor resulted from a global time transformation converting the position-dependent mass to a constant one seems to be equivalent to the semiclassical correction of the Lagrangian proposed by Enz and Schilling. A long standing question whether the spin-coherent-state representation of path integrals can result in an accurate tunnel splitting is therefore resolved

Non-equilibrium properties of Josephson critical current in Nb-based three terminal superconducting tunnel devices

International Nuclear Information System (INIS)

Ammendola, G.; Parlato, L.; Peluso, G.; Pepe, G.

1998-01-01

Tunnel quasi-particle injection into a superconducting film provides useful information on the non-equilibrium state inside the perturbed superconductor as well as on the potential application to electronic devices. Three terminal injector-detector superconducting devices have a long history in non-equilibrium superconductivity. In the recent past non-equilibrium phenomena have attracted again considerable attention because of many superconducting based detectors involve processes substantially non-equilibrium in nature. The possibility of using a stacked double tunnel junction to study the influence of non-equilibrium superconductivity on the Josephson critical current is now considered. An experimental study of the effect of quasi-particle injection on the Josephson current both in steady-state and pulsed experiments down to T=1.2 K is presented using 3 terminal Nb-based stacked double tunnel devices. The feasibility of a new class of particle detectors based on the direct measurement of the change in the Josephson current following the absorption of a X-ray quantum is also discussed in terms of non-equilibrium theories. (orig.)

In situ scanning tunneling microscope tip treatment device for spin polarization imaging

Science.gov (United States)

Li, An-Ping [Oak Ridge, TN; Jianxing, Ma [Oak Ridge, TN; Shen, Jian [Knoxville, TN

2008-04-22

A tip treatment device for use in an ultrahigh vacuum in situ scanning tunneling microscope (STM). The device provides spin polarization functionality to new or existing variable temperature STM systems. The tip treatment device readily converts a conventional STM to a spin-polarized tip, and thereby converts a standard STM system into a spin-polarized STM system. The tip treatment device also has functions of tip cleaning and tip flashing a STM tip to high temperature (>2000.degree. C.) in an extremely localized fashion. Tip coating functions can also be carried out, providing the tip sharp end with monolayers of coating materials including magnetic films. The device is also fully compatible with ultrahigh vacuum sample transfer setups.

Integrated control rod monitoring device

International Nuclear Information System (INIS)

Saito, Katsuhiro

1997-01-01

The present invention provides a device in which an entire control rod driving time measuring device and a control rod position support device in a reactor building and a central control chamber are integrated systematically to save hardwares such as a signal input/output device and signal cables between boards. Namely, (1) functions of the entire control rod driving time measuring device for monitoring control rods which control the reactor power and a control rod position indication device are integrated into one identical system. Then, the entire devices can be made compact by the integration of the functions. (2) The functions of the entire control rod driving time measuring device and the control rod position indication device are integrated in a central operation board and a board in the site. Then, the place for the installation of them can be used in common in any of the cases. (3) The functions of the entire control rod driving time measuring device and the control rod position indication device are integrated to one identical system to save hardware to be used. Then, signal input/output devices and drift branching panel boards in the site and the central operation board can be saved, and cables for connecting both of the boards is no more necessary. (I.S.)

Feasibilty of a Multi-bit Cell Perpendicular Magnetic Tunnel Junction Device

Science.gov (United States)

Kim, Chang Soo

The ultimate objective of this research project was to explore the feasibility of making a multi-bit cell perpendicular magnetic tunnel junction (PMTJ) device to increase the storage density of spin-transfer-torque random access memory (STT-RAM). As a first step toward demonstrating a multi-bit cell device, this dissertation contributed a systematic and detailed study of developing a single cell PMTJ device using L10 FePt films. In the beginning of this research, 13 up-and-coming non-volatile memory (NVM) technologies were investigated and evaluated to see whether one of them might outperform NAND flash memories and even HDDs on a cost-per-TB basis in 2020. This evaluation showed that STT-RAM appears to potentially offer superior power efficiency, among other advantages. It is predicted that STTRAM's density could make it a promising candidate for replacing NAND flash memories and possibly HDDs if STTRAM could be improved to store multiple bits per cell. Ta/Mg0 under-layers were used first in order to develop (001) L1 0 ordering of FePt at a low temperature of below 400 °C. It was found that the tradeoff between surface roughness and (001) L10 ordering of FePt makes it difficult to achieve low surface roughness and good perpendicular magnetic properties simultaneously when Ta/Mg0 under-layers are used. It was, therefore, decided to investigate MgO/CrRu under-layers to simultaneously achieve smooth films with good ordering below 400°C. A well ordered 4 nm L10 FePt film with RMS surface roughness close to 0.4 nm, perpendicular coercivity of about 5 kOe, and perpendicular squareness near 1 was obtained at a deposition temperature of 390 °C on a thermally oxidized Si substrate when MgO/CrRu under-layers are used. A PMTJ device was developed by depositing a thin MgO tunnel barrier layer and a top L10 FePt film and then being postannealed at 450 °C for 30 minutes. It was found that the sputtering power needs to be minimized during the thin MgO tunnel barrier

Fabrication of Gate-tunable Graphene Devices for Scanning Tunneling Microscopy Studies with Coulomb Impurities

Science.gov (United States)

Jung, Han Sae; Tsai, Hsin-Zon; Wong, Dillon; Germany, Chad; Kahn, Salman; Kim, Youngkyou; Aikawa, Andrew S.; Desai, Dhruv K.; Rodgers, Griffin F.; Bradley, Aaron J.; Velasco, Jairo; Watanabe, Kenji; Taniguchi, Takashi; Wang, Feng; Zettl, Alex; Crommie, Michael F.

2015-01-01

Owing to its relativistic low-energy charge carriers, the interaction between graphene and various impurities leads to a wealth of new physics and degrees of freedom to control electronic devices. In particular, the behavior of graphene’s charge carriers in response to potentials from charged Coulomb impurities is predicted to differ significantly from that of most materials. Scanning tunneling microscopy (STM) and scanning tunneling spectroscopy (STS) can provide detailed information on both the spatial and energy dependence of graphene's electronic structure in the presence of a charged impurity. The design of a hybrid impurity-graphene device, fabricated using controlled deposition of impurities onto a back-gated graphene surface, has enabled several novel methods for controllably tuning graphene’s electronic properties.1-8 Electrostatic gating enables control of the charge carrier density in graphene and the ability to reversibly tune the charge2 and/or molecular5 states of an impurity. This paper outlines the process of fabricating a gate-tunable graphene device decorated with individual Coulomb impurities for combined STM/STS studies.2-5 These studies provide valuable insights into the underlying physics, as well as signposts for designing hybrid graphene devices. PMID:26273961

Engineering few-layer MoTe2 devices by Co/hBN tunnel contacts

Science.gov (United States)

Zhu, Mengjian; Luo, Wei; Wu, Nannan; Zhang, Xue-ao; Qin, Shiqiao

2018-04-01

2H phase Molybdenum ditelluride (MoTe2) is a layered two-dimensional (2D) semiconductor that has recently gained extensive attention for its intriguing properties, demonstrating great potential for nanoelectronics and optoelectronics. Optimizing the electric contacts to MoTe2 is a critical step for realizing high performance devices. Here, we demonstrate Co/hBN tunnel contacts to few-layer MoTe2. In sharp contrast to the p-type conduction of Co contacted MoTe2, Co/hBN tunnel contacted MoTe2 devices show clear n-type transport properties. Our first principles calculation reveals that the inserted few-layer hBN strongly interacts with Co and significantly reduces its work-function by ˜1.2 eV, while MoTe2 itself has a much weaker influence on the work-function of Co. This allows us to build MoTe2 diodes using the mixed Co/hBN and Co contact architecture, which can be switched from p-n type to n-p type by changing the gate-voltage, paving the way for engineering multi-functional devices based on atomically thin 2D semiconductors.

Early integration of a bone plug in the femoral tunnel in rectangular tunnel ACL reconstruction with a bone-patellar tendon-bone graft: a prospective computed tomography analysis.

Science.gov (United States)

Suzuki, Tomoyuki; Shino, Konsei; Nakagawa, Shigeto; Nakata, Ken; Iwahashi, Takehiko; Kinugasa, Kazutaka; Otsubo, Hidenori; Yamashita, Toshihiko

2011-12-01

The purpose of this prospective study was to evaluate how early the bone plug was integrated into the rectangular femoral tunnel after anatomical ACL reconstruction using a bone-patellar tendon-bone (BTB) graft via a rectangular tunnel (RT BTB ACL-R). Twenty consecutive patients who had undergone the reconstruction procedure were evaluated by CT scans at 4 and 8 weeks postoperatively. In each scan, 30 slices for multiplanar reconstruction were collected parallel to the long axis of the parallelepiped femoral tunnel and perpendicular to the tendinous plane of the bone plug. Each slice was classified as "complete," indicating no visible gap between the plug and the tunnel wall or trabecular continuity or "incomplete," showing a visible gap. Bone plug-tunnel integration was evaluated as "excellent," "good," "fair," or "poor" for >20, 11-20, 5-10, and values at the anterior interface between the bone plug and the tunnel wall were also measured on both scans. The mean changes in CT value at 8 weeks were significantly lower than those at 4 weeks. This study shows that bone plug-femoral tunnel integration was almost complete by 8 weeks after surgery using RT BTB ACL-R.

Photo-Detectors Integrated with Resonant Tunneling Diodes

Directory of Open Access Journals (Sweden)

José M. L. Figueiredo

2013-07-01

Full Text Available We report on photo-detectors consisting of an optical waveguide that incorporates a resonant tunneling diode (RTD. Operating at wavelengths around 1.55 μm in the optical communications C band we achieve maximum sensitivities of around 0.29 A/W which is dependent on the bias voltage. This is due to the nature of RTD nonlinear current-voltage characteristic that has a negative differential resistance (NDR region. The resonant tunneling diode photo-detector (RTD-PD can be operated in either non-oscillating or oscillating regimes depending on the bias voltage quiescent point. The oscillating regime is apparent when the RTD-PD is biased in the NDR region giving rise to electrical gain and microwave self-sustained oscillations Taking advantage of the RTD’s NDR distinctive characteristics, we demonstrate efficient detection of gigahertz (GHz modulated optical carriers and optical control of a RTD GHz oscillator. RTD-PD based devices can have applications in generation and optical control of GHz low-phase noise oscillators, clock recovery systems, and fiber optic enabled radio frequency communication systems.

Anisotropic sensor and memory device with a ferromagnetic tunnel barrier as the only magnetic element.

Science.gov (United States)

Lόpez-Mir, L; Frontera, C; Aramberri, H; Bouzehouane, K; Cisneros-Fernández, J; Bozzo, B; Balcells, L; Martínez, B

2018-01-16

Multiple spin functionalities are probed on Pt/La 2 Co 0.8 Mn 1.2 O 6 /Nb:SrTiO 3 , a device composed by a ferromagnetic insulating barrier sandwiched between non-magnetic electrodes. Uniquely, La 2 Co 0.8 Mn 1.2 O 6 thin films present strong perpendicular magnetic anisotropy of magnetocrystalline origin, property of major interest for spintronics. The junction has an estimated spin-filtering efficiency of 99.7% and tunneling anisotropic magnetoresistance (TAMR) values up to 30% at low temperatures. This remarkable angular dependence of the magnetoresistance is associated with the magnetic anisotropy whose origin lies in the large spin-orbit interaction of Co 2+ which is additionally tuned by the strain of the crystal lattice. Furthermore, we found that the junction can operate as an electrically readable magnetic memory device. The findings of this work demonstrate that a single ferromagnetic insulating barrier with strong magnetocrystalline anisotropy is sufficient for realizing sensor and memory functionalities in a tunneling device based on TAMR.

Failure Analysis in Magnetic Tunnel Junction Nanopillar with Interfacial Perpendicular Magnetic Anisotropy

Directory of Open Access Journals (Sweden)

Weisheng Zhao

2016-01-01

Full Text Available Magnetic tunnel junction nanopillar with interfacial perpendicular magnetic anisotropy (PMA-MTJ becomes a promising candidate to build up spin transfer torque magnetic random access memory (STT-MRAM for the next generation of non-volatile memory as it features low spin transfer switching current, fast speed, high scalability, and easy integration into conventional complementary metal oxide semiconductor (CMOS circuits. However, this device suffers from a number of failure issues, such as large process variation and tunneling barrier breakdown. The large process variation is an intrinsic issue for PMA-MTJ as it is based on the interfacial effects between ultra-thin films with few layers of atoms; the tunneling barrier breakdown is due to the requirement of an ultra-thin tunneling barrier (e.g., <1 nm to reduce the resistance area for the spin transfer torque switching in the nanopillar. These failure issues limit the research and development of STT-MRAM to widely achieve commercial products. In this paper, we give a full analysis of failure mechanisms for PMA-MTJ and present some eventual solutions from device fabrication to system level integration to optimize the failure issues.

Charge Islands Through Tunneling

Science.gov (United States)

Robinson, Daryl C.

2002-01-01

It has been recently reported that the electrical charge in a semiconductive carbon nanotube is not evenly distributed, but rather it is divided into charge "islands." This paper links the aforementioned phenomenon to tunneling and provides further insight into the higher rate of tunneling processes, which makes tunneling devices attractive. This paper also provides a basis for calculating the charge profile over the length of the tube so that nanoscale devices' conductive properties may be fully exploited.

Integrity inspection of main access tunnel using ground penetrating radar

Science.gov (United States)

Ismail, M. A.; Abas, A. A.; Arifin, M. H.; Ismail, M. N.; Othman, N. A.; Setu, A.; Ahmad, M. R.; Shah, M. K.; Amin, S.; Sarah, T.

2017-11-01

This paper discusses the Ground Penetrating Radar (GPR) survey performed to determine the integrity of wall of tunnel at a hydroelectric power generation facility. GPR utilises electromagnetic waves that are transmitted into the medium of survey. Any reflectors in the medium will reflect the transmitted waves and picked up by the GPR antenna. The survey was done using MALA GeoScience RAMAC CUII with 250MHz antenna. Survey was done on the left, the crown and the right walls of the underground tunnels. Distance was measured using wheel encoders. The results of the survey is discussed in this paper.

Use of an augmented-vision device for visual search by patients with tunnel vision.

Science.gov (United States)

Luo, Gang; Peli, Eli

2006-09-01

To study the effect of an augmented-vision device that superimposes minified contour images over natural vision on visual search performance of patients with tunnel vision. Twelve subjects with tunnel vision searched for targets presented outside their visual fields (VFs) on a blank background under three cue conditions (with contour cues provided by the device, with auditory cues, and without cues). Three subjects (VF, 8 degrees -11 degrees wide) carried out the search over a 90 degrees x 74 degrees area, and nine subjects (VF, 7 degrees -16 degrees wide) carried out the search over a 66 degrees x 52 degrees area. Eye and head movements were recorded for performance analyses that included directness of search path, search time, and gaze speed. Directness of the search path was greatly and significantly improved when the contour or auditory cues were provided in the larger and the smaller area searches. When using the device, a significant reduction in search time (28% approximately 74%) was demonstrated by all three subjects in the larger area search and by subjects with VFs wider than 10 degrees in the smaller area search (average, 22%). Directness and gaze speed accounted for 90% of the variability of search time. Although performance improvement with the device for the larger search area was obvious, whether it was helpful for the smaller search area depended on VF and gaze speed. Because improvement in directness was demonstrated, increased gaze speed, which could result from further training and adaptation to the device, might enable patients with small VFs to benefit from the device for visual search tasks.

Photon-phonon-enhanced infrared rectification in a two-dimensional nanoantenna-coupled tunnel diode

International Nuclear Information System (INIS)

Kadlec, Emil A.; Jarecki, Robert L.; Starbuck, Andrew; Peters, David W.; Davids, Paul S.

2016-01-01

The interplay of strong infrared photon-phonon coupling with electromagnetic confinement in nanoscale devices is demonstrated to have a large impact on ultrafast photon-assisted tunneling in metal-oxide-semiconductor (MOS) structures. Infrared active optical phonon modes in polar oxides lead to strong dispersion and enhanced electric fields at material interfaces. We find that the infrared dispersion of SiO_2 near a longitudinal optical phonon mode can effectively impedance match a photonic surface mode into a nanoscale tunnel gap that results in large transverse-field confinement. An integrated 2D nanoantenna structure on a distributed large-area MOS tunnel-diode rectifier is designed and built to resonantly excite infrared surface modes and is shown to efficiently channel infrared radiation into nanometer-scale gaps in these MOS devices. This enhanced-gap transverse-electric field is converted to a rectified tunneling displacement current resulting in a dc photocurrent. We examine the angular and polarization-dependent spectral photocurrent response of these 2D nanoantenna-coupled tunnel diodes in the photon-enhanced tunneling spectral region. Lastly, our 2D nanoantenna-coupled infrared tunnel-diode rectifier promises to impact large-area thermal energy harvesting and infrared direct detectors.

Emerging materials and devices in spintronic integrated circuits for energy-smart mobile computing and connectivity

International Nuclear Information System (INIS)

Kang, S.H.; Lee, K.

2013-01-01

A spintronic integrated circuit (IC) is made of a combination of a semiconductor IC and a dense array of nanometer-scale magnetic tunnel junctions. This emerging field is of growing scientific and engineering interest, owing to its potential to bring disruptive device innovation to the world of electronics. This technology is currently being pursued not only for scalable non-volatile spin-transfer-torque magnetoresistive random access memory, but also for various forms of non-volatile logic (Spin-Logic). This paper reviews recent advances in spintronic IC. Key discoveries and breakthroughs in materials and devices are highlighted in light of the broader perspective of their application in low-energy mobile computing and connectivity systems, which have emerged as leading drivers for the prevailing electronics ecosystem

Band to Band Tunneling (BBT) Induced Leakage Current Enhancement in Irradiated Fully Depleted SOI Devices

Science.gov (United States)

Adell, Phillipe C.; Barnaby, H. J.; Schrimpf, R. D.; Vermeire, B.

2007-01-01

We propose a model, validated with simulations, describing how band-to-band tunneling (BBT) affects the leakage current degradation in some irradiated fully-depleted SOI devices. The dependence of drain current on gate voltage, including the apparent transition to a high current regime is explained.

Operating modes of superconducting tunnel junction device

Energy Technology Data Exchange (ETDEWEB)

Maehata, Keisuke [Kyushu Univ., Fukuoka (Japan). Faculty of Engineering

1998-07-01

In the Electrotechnical Laboratory, an Nb type superconducting tunnel junction (STJ) device with 200 x 200 sq. micron in area and super high quality was manufactured. By using 55-fe source, response of this large area STJ to X-ray was measured. In this measurement, two action modes with different output wave height from front amplifier were observed. Then, in this study, current-voltage feature of the element in each action mode was analyzed to elucidate a mechanism to form such two action modes. The feature was analyzed by using first order approximate solution on cavity resonance mode of Sine-Gordon equation. From the analytical results, it could be supposed that direction and magnitude of effective magnetic field penetrating into jointed area changed by an induction current effect owing to impressing speed of the magnetic field, which brings two different current-voltage features to make possible to observe two action modes with different pulse wave height. (G.K.)

Integrated lenses in polystyrene microfluidic devices

KAUST Repository

Fan, Yiqiang; Li, Huawei; Foulds, Ian G.

2013-01-01

This paper reports a new method for integrating microlenses into microfluidic devices for improved observation. Two demonstration microfluidic devices were provided which were fabricated using this new technique. The integrated microlenses were

Extended wearing trial of Trifield lens device for 'tunnel vision'.

Science.gov (United States)

Woods, Russell L; Giorgi, Robert G; Berson, Eliot L; Peli, Eli

2010-05-01

Severe visual field constriction (tunnel vision) impairs the ability to navigate and walk safely. We evaluated Trifield glasses as a mobility rehabilitation device for tunnel vision in an extended wearing trial. Twelve patients with tunnel vision (5-22 degrees wide) due to retinitis pigmentosa or choroideremia participated in the 5-visit wearing trial. To expand the horizontal visual field, one spectacle lens was fitted with two apex-to-apex prisms that vertically bisected the pupil on primary gaze. This provides visual field expansion at the expense of visual confusion (two objects with the same visual direction). Patients were asked to wear these spectacles as much as possible for the duration of the wearing trial (median 8, range 6-60 weeks). Clinical success (continued wear, indicating perceived overall benefit), visual field expansion, perceived direction and perceived visual ability were measured. Of 12 patients, nine chose to continue wearing the Trifield glasses at the end of the wearing trial. Of those nine patients, at long-term follow-up (35-78 weeks), three reported still wearing the Trifield glasses. Visual field expansion (median 18, range 9-38 degrees) was demonstrated for all patients. No patient demonstrated adaptation to the change in visual direction produced by the Trifield glasses (prisms). For reported difficulty with obstacles, some differences between successful and non-successful wearers were found. Trifield glasses provided reported benefits in obstacle avoidance to 7 of the 12 patients completing the wearing trial. Crowded environments were particularly difficult for most wearers. Possible reasons for long-term discontinuation and lack of adaptation to perceived direction are discussed.

High performance bio-integrated devices

Science.gov (United States)

Kim, Dae-Hyeong; Lee, Jongha; Park, Minjoon

2014-06-01

In recent years, personalized electronics for medical applications, particularly, have attracted much attention with the rise of smartphones because the coupling of such devices and smartphones enables the continuous health-monitoring in patients' daily life. Especially, it is expected that the high performance biomedical electronics integrated with the human body can open new opportunities in the ubiquitous healthcare. However, the mechanical and geometrical constraints inherent in all standard forms of high performance rigid wafer-based electronics raise unique integration challenges with biotic entities. Here, we describe materials and design constructs for high performance skin-mountable bio-integrated electronic devices, which incorporate arrays of single crystalline inorganic nanomembranes. The resulting electronic devices include flexible and stretchable electrophysiology electrodes and sensors coupled with active electronic components. These advances in bio-integrated systems create new directions in the personalized health monitoring and/or human-machine interfaces.

Ultralarge area MOS tunnel devices for electron emission

DEFF Research Database (Denmark)

Thomsen, Lasse Bjørchmar; Nielsen, Gunver; Vendelbo, Søren Bastholm

2007-01-01

density. Oxide thicknesses have been extracted by fitting a model based on Fermi-Dirac statistics to the C-V characteristics. By plotting I-V characteristics in a Fowler plot, a measure of the thickness of the oxide can be extracted from the tunnel current. These apparent thicknesses show a high degree......A comparative analysis of metal-oxide-semiconductor (MOS) capacitors by capacitance-voltage (C-V) and current-voltage (I-V) characteristics has been employed to characterize the thickness variations of the oxide on different length scales. Ultralarge area (1 cm(2)) ultrathin (similar to 5 nm oxide......) MOS capacitors have been fabricated to investigate their functionality and the variations in oxide thickness, with the use as future electron emission devices as the goal. I-V characteristics show very low leakage current and excellent agreement to the Fowler-Nordheim expression for the current...

Modelling of optoelectronic circuits based on resonant tunneling diodes

Science.gov (United States)

Rei, João. F. M.; Foot, James A.; Rodrigues, Gil C.; Figueiredo, José M. L.

2017-08-01

Resonant tunneling diodes (RTDs) are the fastest pure electronic semiconductor devices at room temperature. When integrated with optoelectronic devices they can give rise to new devices with novel functionalities due to their highly nonlinear properties and electrical gain, with potential applications in future ultra-wide-band communication systems (see e.g. EU H2020 iBROW Project). The recent coverage on these devices led to the need to have appropriated simulation tools. In this work, we present RTD based optoelectronic circuits simulation packages to provide circuit signal level analysis such as transient and frequency responses. We will present and discuss the models, and evaluate the simulation packages.

Resonant Tunneling Spin Pump

Science.gov (United States)

Ting, David Z.

2007-01-01

The resonant tunneling spin pump is a proposed semiconductor device that would generate spin-polarized electron currents. The resonant tunneling spin pump would be a purely electrical device in the sense that it would not contain any magnetic material and would not rely on an applied magnetic field. Also, unlike prior sources of spin-polarized electron currents, the proposed device would not depend on a source of circularly polarized light. The proposed semiconductor electron-spin filters would exploit the Rashba effect, which can induce energy splitting in what would otherwise be degenerate quantum states, caused by a spin-orbit interaction in conjunction with a structural-inversion asymmetry in the presence of interfacial electric fields in a semiconductor heterostructure. The magnitude of the energy split is proportional to the electron wave number. Theoretical studies have suggested the possibility of devices in which electron energy states would be split by the Rashba effect and spin-polarized currents would be extracted by resonant quantum-mechanical tunneling.

Probing spin-polarized tunneling at high bias and temperature with a magnetic tunnel transistor

NARCIS (Netherlands)

Park, B.G.; Banerjee, T.; Min, B.C.; Sanderink, Johannes G.M.; Lodder, J.C.; Jansen, R.

2005-01-01

The magnetic tunnel transistor (MTT) is a three terminal hybrid device that consists of a tunnel emitter, a ferromagnetic (FM) base, and a semiconductor collector. In the MTT with a FM emitter and a single FM base, spin-polarized hot electrons are injected into the base by tunneling. After

Potentials and challenges of integration for complex metal oxides in CMOS devices and beyond

International Nuclear Information System (INIS)

Kim, Y; Pham, C; Chang, J P

2015-01-01

This review focuses on recent accomplishments on complex metal oxide based multifunctional materials and the potential they hold in advancing integrated circuits. It begins with metal oxide based high-κ materials to highlight the success of their integration since 45 nm complementary metal–oxide–semiconductor (CMOS) devices. By simultaneously offering a higher dielectric constant for improved capacitance as well as providing a thicker physical layer to prevent the quantum mechanical tunnelling of electrons, high-κ materials have enabled the continued down-scaling of CMOS based devices. The most recent technology driver has been the demand to lower device power consumption, which requires the design and synthesis of novel materials, such as complex metal oxides that exhibit remarkable tunability in their ferromagnetic, ferroelectric and multiferroic properties. These properties make them suitable for a wide variety of applications such as magnetoelectric random access memory, radio frequency band pass filters, antennae and magnetic sensors. Single-phase multiferroics, while rare, offer unique functionalities which have motivated much scientific and technological research to ascertain the origins of their multiferroicity and their applicability to potential devices. However, due to the weak magnetoelectric coupling for single-phase multiferroics, engineered multiferroic composites based on magnetostrictive ferromagnets interfacing piezoelectrics or ferroelectrics have shown enhanced multiferroic behaviour from effective strain coupling at the interface. In addition, nanostructuring of the ferroic phases has demonstrated further improvement in the coupling effect. Therefore, single-phase and engineered composite multiferroics consisting of complex metal oxides are reviewed in terms of magnetoelectric coupling effects and voltage controlled ferromagnetic properties, followed by a review on the integration challenges that need to be overcome to realize the

NASA ERA Integrated CFD for Wind Tunnel Testing of Hybrid Wing-Body Configuration

Science.gov (United States)

Garcia, Joseph A.; Melton, John E.; Schuh, Michael; James, Kevin D.; Long, Kurt R.; Vicroy, Dan D.; Deere, Karen A.; Luckring, James M.; Carter, Melissa B.; Flamm, Jeffrey D.;

A 2D analytical cylindrical gate tunnel FET (CG-TFET) model: impact of shortest tunneling distance

Science.gov (United States)

Dash, S.; Mishra, G. P.

2015-09-01

A 2D analytical tunnel field-effect transistor (FET) potential model with cylindrical gate (CG-TFET) based on the solution of Laplace’s equation is proposed. The band-to-band tunneling (BTBT) current is derived by the help of lateral electric field and the shortest tunneling distance. However, the analysis is extended to obtain the subthreshold swing (SS) and transfer characteristics of the device. The dependency of drain current, SS and transconductance on gate voltage and shortest tunneling distance is discussed. Also, the effect of scaling the gate oxide thickness and the cylindrical body diameter on the electrical parameters of the device is analyzed.

A 2D analytical cylindrical gate tunnel FET (CG-TFET) model: impact of shortest tunneling distance

International Nuclear Information System (INIS)

Dash, S; Mishra, G P

2015-01-01

A 2D analytical tunnel field-effect transistor (FET) potential model with cylindrical gate (CG-TFET) based on the solution of Laplace’s equation is proposed. The band-to-band tunneling (BTBT) current is derived by the help of lateral electric field and the shortest tunneling distance. However, the analysis is extended to obtain the subthreshold swing (SS) and transfer characteristics of the device. The dependency of drain current, SS and transconductance on gate voltage and shortest tunneling distance is discussed. Also, the effect of scaling the gate oxide thickness and the cylindrical body diameter on the electrical parameters of the device is analyzed. (paper)

Integrated lenses in polystyrene microfluidic devices

KAUST Repository

Fan, Yiqiang

2013-04-01

This paper reports a new method for integrating microlenses into microfluidic devices for improved observation. Two demonstration microfluidic devices were provided which were fabricated using this new technique. The integrated microlenses were fabricated using a free-surface thermo-compression molding method on a polystyrene (PS) sheet which was then bonded on top of microfluidic channels as a cover plate, with the convex microlenses providing a magnified image of the channel for the easier observation of the flow in the microchannels. This approach for fabricating the integrated microlens in microfluidic devices is rapid, low cost and without the requirement of cleanroom facilities. © 2013 IEEE.

New Tunneling Features in Polar III-Nitride Resonant Tunneling Diodes

Directory of Open Access Journals (Sweden)

Jimy Encomendero

2017-10-01

Full Text Available For the past two decades, repeatable resonant tunneling transport of electrons in III-nitride double barrier heterostructures has remained elusive at room temperature. In this work we theoretically and experimentally study III-nitride double-barrier resonant tunneling diodes (RTDs, the quantum transport characteristics of which exhibit new features that are unexplainable using existing semiconductor theory. The repeatable and robust resonant transport in our devices enables us to track the origin of these features to the broken inversion symmetry in the uniaxial crystal structure, which generates built-in spontaneous and piezoelectric polarization fields. Resonant tunneling transport enabled by the ground state as well as by the first excited state is demonstrated for the first time over a wide temperature window in planar III-nitride RTDs. An analytical transport model for polar resonant tunneling heterostructures is introduced for the first time, showing a good quantitative agreement with experimental data. From this model we realize that tunneling transport is an extremely sensitive measure of the built-in polarization fields. Since such electric fields play a crucial role in the design of electronic and photonic devices, but are difficult to measure, our work provides a completely new method to accurately determine their magnitude for the entire class of polar heterostructures.

Scalability of Ferroelectric Tunnel Junctions to Sub-100 nm Dimensions

Science.gov (United States)

Abuwasib, Mohammad

The ferroelectric tunnel junction (FTJ) is an emerging low-power device that has potential application as a non-volatile memory and logic element in beyond-CMOS circuits. As a beyond- CMOS device, it is necessary to investigate the device scaling limit of FTJs to sub-50 nm dimensions. In addition to the fabrication of scaled FTJs, the integration challenges and CMOS compatibility of the device needs to be addressed. FTJ device performance including ON/OFF ratio, memory retention time, switching endurance, write /read speed and power dissipation need to be characterized for benchmarking of this emerging device, compared to its charge-based counterparts such as DRAM, NAND/NOR flash, as well as to other emerging memory devices. In this dissertation, a detailed investigation of scaling of BaTiO3 (BTO) based FTJs was performed, from full-scale integration to electrical characterization. Two types of FTJs with La0.67Sr0.33MnO3 (LSMO) and SrRuO3 (SRO) bottom electrodes were investigated in this work namely; Co/BTO/LSMO and Co/BTO/SRO. A CMOS compatible fabrication process for integration of Co/BTO/LSMO FTJ devices ( 3x3 microm 2) was demonstrated for the first time using standard photolithography and self-aligned RIE technique. The fabricated FTJ device showed switching behavior, however, degradation of the LSMO contact was observed during the fabrication process. A detailed investigation of the contact properties of bottom electrode materials (LSMO, SRO) for BTO-based FTJs was performed. The process and thermal stability of different contact overlayers (Ti, Pt) was explained to understand the nature of the ohmic contacts for metal to SRO and LSMO layers. Noble metals-to-SRO was found to form the most stable contacts for FTJs. Based on this study, a systematic scalability study of Co/BTO/SRO FTJs was carried out from micron ( 3x3 microm2) to submicron ( 200x200 nm2) dimensions. Positive UP Negative Down (PUND) measurement confirms the ferroelectric properties of the BTO

Homoepitaxial graphene tunnel barriers for spin transport

Directory of Open Access Journals (Sweden)

Adam L. Friedman

2016-05-01

Full Text Available Tunnel barriers are key elements for both charge-and spin-based electronics, offering devices with reduced power consumption and new paradigms for information processing. Such devices require mating dissimilar materials, raising issues of heteroepitaxy, interface stability, and electronic states that severely complicate fabrication and compromise performance. Graphene is the perfect tunnel barrier. It is an insulator out-of-plane, possesses a defect-free, linear habit, and is impervious to interdiffusion. Nonetheless, true tunneling between two stacked graphene layers is not possible in environmental conditions usable for electronics applications. However, two stacked graphene layers can be decoupled using chemical functionalization. Here, we demonstrate that hydrogenation or fluorination of graphene can be used to create a tunnel barrier. We demonstrate successful tunneling by measuring non-linear IV curves and a weakly temperature dependent zero-bias resistance. We demonstrate lateral transport of spin currents in non-local spin-valve structures, and determine spin lifetimes with the non-local Hanle effect. We compare the results for hydrogenated and fluorinated tunnel and we discuss the possibility that ferromagnetic moments in the hydrogenated graphene tunnel barrier affect the spin transport of our devices.

Homoepitaxial graphene tunnel barriers for spin transport

Science.gov (United States)

Friedman, Adam L.; van't Erve, Olaf M. J.; Robinson, Jeremy T.; Whitener, Keith E.; Jonker, Berend T.

2016-05-01

Tunnel barriers are key elements for both charge-and spin-based electronics, offering devices with reduced power consumption and new paradigms for information processing. Such devices require mating dissimilar materials, raising issues of heteroepitaxy, interface stability, and electronic states that severely complicate fabrication and compromise performance. Graphene is the perfect tunnel barrier. It is an insulator out-of-plane, possesses a defect-free, linear habit, and is impervious to interdiffusion. Nonetheless, true tunneling between two stacked graphene layers is not possible in environmental conditions usable for electronics applications. However, two stacked graphene layers can be decoupled using chemical functionalization. Here, we demonstrate that hydrogenation or fluorination of graphene can be used to create a tunnel barrier. We demonstrate successful tunneling by measuring non-linear IV curves and a weakly temperature dependent zero-bias resistance. We demonstrate lateral transport of spin currents in non-local spin-valve structures, and determine spin lifetimes with the non-local Hanle effect. We compare the results for hydrogenated and fluorinated tunnel and we discuss the possibility that ferromagnetic moments in the hydrogenated graphene tunnel barrier affect the spin transport of our devices.

Device-quality tunnel junctions on the high Tc superconductor HgBa2CuO4+δ

International Nuclear Information System (INIS)

Zasadzinski, J.; Chen, J.; Romano, P.; Gray, K.E.; Wagner, J.L.; Hinks, D.G.

1995-01-01

SIN and SIS tunnel junction devices (e.g. photon detectors, logic elements) require quasiparticle characteristics that exhibit sharp current onsets at the gap voltage and very low sub-gap conductances. Progress is reported on the development of such junctions on High Tc cuprates using mechanical point contacts. In general, these contacts display the optimum characteristics that can be obtained from HTS native-surface tunnel barriers. Most cuprates display a sub-gap conductance which monotonically increases with voltage about the minimum value at zero bias. However, tunneling data of unusually high quality have been obtained for the recently discovered Hg-based cuprate, HgBa 2 CuO 4 (T c =96K). SIS' tunneling data using a Nb tip are presented which exhibit very low and flat sub-gap conductances and sharp conductance peaks as expected from a BCS density of states. These results are slightly improved over earlier published results with SIN junctions. Use of the experimental data to simulate the performance of a quasiparticle mixer demonstrates that noise temperatures approaching the quantum limit are possible for SIS and SIN mixers in the range 1-5 THz

The effect of density-of-state tails on band-to-band tunneling: Theory and application to tunnel field effect transistors

Science.gov (United States)

Sant, S.; Schenk, A.

2017-10-01

It is demonstrated how band tail states in the semiconductor influence the performance of a Tunnel Field Effect Transistor (TFET). As a consequence of the smoothened density of states (DOS) around the band edges, the energetic overlap of conduction and valence band states occurs gradually at the onset of band-to-band tunneling (BTBT), thus degrading the sub-threshold swing (SS) of the TFET. The effect of the band tail states on the current-voltage characteristics is modelled quantum-mechanically based on the idea of zero-phonon trap-assisted tunneling between band and tail states. The latter are assumed to arise from a 3-dimensional pseudo-delta potential proposed by Vinogradov [1]. This model potential allows the derivation of analytical expressions for the generation rate covering the whole range from very strong to very weak localization of the tail states. Comparison with direct BTBT in the one-band effective mass approximation reveals the essential features of tail-to-band tunneling. Furthermore, an analytical solution for the problem of tunneling from continuum states of the disturbed DOS to states in the opposite band is found, and the differences to direct BTBT are worked out. Based on the analytical expressions, a semi-classical model is implemented in a commercial device simulator which involves numerical integration along the tunnel paths. The impact of the tail states on the device performance is analyzed for a nanowire Gate-All-Around TFET. The simulations show that tail states notably impact the transfer characteristics of a TFET. It is found that exponentially decaying band tails result in a stronger degradation of the SS than tail states with a Gaussian decay of their density. The developed model allows more realistic simulations of TFETs including their non-idealities.

Graphene-Molybdenum Disulfide-Graphene Tunneling Junctions with Large-Area Synthesized Materials.

Science.gov (United States)

Joiner, Corey A; Campbell, Philip M; Tarasov, Alexey A; Beatty, Brian R; Perini, Chris J; Tsai, Meng-Yen; Ready, William J; Vogel, Eric M

2016-04-06

Tunneling devices based on vertical heterostructures of graphene and other 2D materials can overcome the low on-off ratios typically observed in planar graphene field-effect transistors. This study addresses the impact of processing conditions on two-dimensional materials in a fully integrated heterostructure device fabrication process. In this paper, graphene-molybdenum disulfide-graphene tunneling heterostructures were fabricated using only large-area synthesized materials, unlike previous studies that used small exfoliated flakes. The MoS2 tunneling barrier is either synthesized on a sacrificial substrate and transferred to the bottom-layer graphene or synthesized directly on CVD graphene. The presence of graphene was shown to have no impact on the quality of the grown MoS2. The thickness uniformity of MoS2 grown on graphene and SiO2 was found to be 1.8 ± 0.22 nm. XPS and Raman spectroscopy are used to show how the MoS2 synthesis process introduces defects into the graphene structure by incorporating sulfur into the graphene. The incorporation of sulfur was shown to be greatly reduced in the absence of molybdenum suggesting molybdenum acts as a catalyst for sulfur incorporation. Tunneling simulations based on the Bardeen transfer Hamiltonian were performed and compared to the experimental tunneling results. The simulations show the use of MoS2 as a tunneling barrier suppresses contributions to the tunneling current from the conduction band. This is a result of the observed reduction of electron conduction within the graphene sheets.

Integrated tunneling sensor for nanoelectromechanical systems

DEFF Research Database (Denmark)

Sadewasser, S.; Abadal, G.; Barniol, N.

2006-01-01

Transducers based on quantum mechanical tunneling provide an extremely sensitive sensor principle, especially for nanoelectromechanical systems. For proper operation a gap between the electrodes of below 1 nm is essential, requiring the use of structures with a mobile electrode. At such small...... distances, attractive van der Waals and capillary forces become sizable, possibly resulting in snap-in of the electrodes. The authors present a comprehensive analysis and evaluation of the interplay between the involved forces and identify requirements for the design of tunneling sensors. Based...... on this analysis, a tunneling sensor is fabricated by Si micromachining technology and its proper operation is demonstrated. (c) 2006 American Institute of Physics....

Vector spin modeling for magnetic tunnel junctions with voltage dependent effects

International Nuclear Information System (INIS)

Manipatruni, Sasikanth; Nikonov, Dmitri E.; Young, Ian A.

2014-01-01

Integration and co-design of CMOS and spin transfer devices requires accurate vector spin conduction modeling of magnetic tunnel junction (MTJ) devices. A physically realistic model of the MTJ should comprehend the spin torque dynamics of nanomagnet interacting with an injected vector spin current and the voltage dependent spin torque. Vector spin modeling allows for calculation of 3 component spin currents and potentials along with the charge currents/potentials in non-collinear magnetic systems. Here, we show 4-component vector spin conduction modeling of magnetic tunnel junction devices coupled with spin transfer torque in the nanomagnet. Nanomagnet dynamics, voltage dependent spin transport, and thermal noise are comprehended in a self-consistent fashion. We show comparison of the model with experimental magnetoresistance (MR) of MTJs and voltage degradation of MR with voltage. Proposed model enables MTJ circuit design that comprehends voltage dependent spin torque effects, switching error rates, spin degradation, and back hopping effects

Band-to-band tunneling in a carbon nanotube metal-oxide-semiconductor field-effect transistor is dominated by phonon assisted tunneling

OpenAIRE

Koswatta, Siyuranga O.; Lundstrom, Mark S.; Nikonov, Dmitri E.

2007-01-01

Band-to-band tunneling (BTBT) devices have recently gained a lot of interest due to their potential for reducing power dissipation in integrated circuits. We have performed extensive simulations for the BTBT operation of carbon nanotube metal-oxide-semiconductor field-effect transistors (CNT-MOSFETs) using the non-equilibrium Green's functions formalism for both ballistic and dissipative quantum transport. In comparison with recently reported experimental data (Y. Lu et al, J. Am. Chem. Soc.,...

Extended Wearing Trial of Trifield Lens Device for “Tunnel Vision”

Science.gov (United States)

Woods, Russell L.; Giorgi, Robert G.; Berson, Eliot L.; Peli, Eli

2009-01-01

Severe visual field constriction (tunnel vision) impairs the ability to navigate and walk safely. We evaluated Trifield glasses as a mobility rehabilitation device for tunnel vision in an extended wearing trial. Twelve patients with tunnel vision (5 to 22 degrees wide) due to retinitis pigmentosa or choroideremia participated in the 5-visit wearing trial. To expand the horizontal visual field, one spectacle lens was fitted with two apex-to-apex prisms that vertically bisected the pupil on primary gaze. This provides visual field expansion at the expense of visual confusion (two objects with the same visual direction). Patients were asked to wear these spectacles as much as possible for the duration of the wearing trial (median 8, range 6 to 60, weeks). Clinical success (continued wear, indicating perceived overall benefit), visual field expansion, perceived direction and perceived visual ability were measured. Of 12 patients, 9 chose to continue wearing the Trifield glasses at the end of the wearing trial. Of those 9 patients, at long-term follow-up (35 to 78 weeks), 3 reported still wearing the Trifield glasses. Visual field expansion (median 18, range 9 to 38, degrees) was demonstrated for all patients. No patient demonstrated adaptation to the change in visual direction produced by the Trifield glasses (prisms). For difficulty with obstacles, some differences between successful and non-successful wearers were found. Trifield glasses provided reported benefits in obstacle avoidance to 7 of the 12 patients completing the wearing trial. Crowded environments were particularly difficult for most wearers. Possible reasons for long-term discontinuation and lack of adaptation to perceived direction are discussed. PMID:20444130

Two-dimensional analytical model for dual-material control-gate tunnel FETs

Science.gov (United States)

Xu, Hui Fang; Dai, Yue Hua; Gui Guan, Bang; Zhang, Yong Feng

2016-09-01

An analytical model for a dual-material control-gate (DMCG) tunnel field effect transistor (TFET) is presented for the first time in this paper, and the influence of the mobile charges on the potential profile is taken into account. On the basis of the potential profile, the lateral electric field is derived and the expression for the drain current is obtained by integrating the band-to-band tunneling (BTBT) generation rate applicable to low-bandgap and high-bandgap materials over the tunneling region. The model also predicts the impacts of the control-gate work function on the potential and drain current. The advantage of this work is that it not only offers physical insight into device physics but also provides the basic designing guideline for DMCG TFETs, enabling the designer to optimize the device in terms of the on-state current, the on-off current ratio, and suppressed ambipolar behavior. Very good agreements for both the potential and drain current are observed between the model calculations and the simulated results.

Development of the tunneling junction simulation environment for scanning tunneling microscope evaluation

International Nuclear Information System (INIS)

Gajewski, Krzysztof; Piasecki, Tomasz; Kopiec, Daniel; Gotszalk, Teodor

2017-01-01

Proper configuration of scanning tunneling microscope electronics plays an important role in the atomic scale resolution surface imaging. Device evaluation in the tunneling contact between scanning tip and sample may be prone to the surface quality or mechanical disturbances. Thus the use of tunneling junction simulator makes electronics testing more reliable and increases its repeatability. Here, we present the theoretical background enabling the proper selection of electronic components circuitry used as a tunneling junction simulator. We also show how to simulate mechanics related to the piezoelectric scanner, which is applied in real experiments. Practical use of the proposed simulator and its application in metrological characterization of the developed scanning tunneling microscope is also shown. (paper)

A new spin-functional MOSFET based on magnetic tunnel junction technology: pseudo-spin-MOSFET

OpenAIRE

Shuto, Yusuke; Nakane, Ryosho; Wang, Wenhong; Sukegawa, Hiroaki; Yamamoto, Shuu'ichirou; Tanaka, Masaaki; Inomata, Koichiro; Sugahara, Satoshi

2009-01-01

We fabricated and characterized a new spin-functional MOSFET referred to as a pseudo-spin-MOSFET (PS-MOSFET). The PS-MOSFET is a circuit using an ordinary MOSFET and magnetic tunnel junction (MTJ) for reproducing functions of spin-transistors. Device integration techniques for a bottom gate MOSFET using a silicon-on-insulator (SOI) substrate and for an MTJ with a full-Heusler alloy electrode and MgO tunnel barrier were developed. The fabricated PS-MOSFET exhibited high and low transconductanc...

Resonant tunnelling and negative differential conductance in graphene transistors

Science.gov (United States)

Britnell, L.; Gorbachev, R. V.; Geim, A. K.; Ponomarenko, L. A.; Mishchenko, A.; Greenaway, M. T.; Fromhold, T. M.; Novoselov, K. S.; Eaves, L.

2013-04-01

The chemical stability of graphene and other free-standing two-dimensional crystals means that they can be stacked in different combinations to produce a new class of functional materials, designed for specific device applications. Here we report resonant tunnelling of Dirac fermions through a boron nitride barrier, a few atomic layers thick, sandwiched between two graphene electrodes. The resonance occurs when the electronic spectra of the two electrodes are aligned. The resulting negative differential conductance in the device characteristics persists up to room temperature and is gate voltage-tuneable due to graphene’s unique Dirac-like spectrum. Although conventional resonant tunnelling devices comprising a quantum well sandwiched between two tunnel barriers are tens of nanometres thick, the tunnelling carriers in our devices cross only a few atomic layers, offering the prospect of ultra-fast transit times. This feature, combined with the multi-valued form of the device characteristics, has potential for applications in high-frequency and logic devices.

Tunneling effect on double potential barriers GaAs and PbS

Science.gov (United States)

Prastowo, S. H. B.; Supriadi, B.; Ridlo, Z. R.; Prihandono, T.

2018-04-01

A simple model of transport phenomenon tunnelling effect through double barrier structure was developed. In this research we concentrate on the variation of electron energy which entering double potential barriers to transmission coefficient. The barriers using semiconductor materials GaAs (Galium Arsenide) with band-gap energy 1.424 eV, distance of lattice 0.565 nm, and PbS (Lead Sulphide) with band gap energy 0.41 eV distance of lattice is 18 nm. The Analysisof tunnelling effect on double potentials GaAs and PbS using Schrodinger’s equation, continuity, and matrix propagation to get transmission coefficient. The maximum energy of electron that we use is 1.0 eV, and observable from 0.0025 eV- 1.0 eV. The shows the highest transmission coefficient is0.9982 from electron energy 0.5123eV means electron can pass the barriers with probability 99.82%. Semiconductor from materials GaAs and PbS is one of selected material to design semiconductor device because of transmission coefficient directly proportional to bias the voltage of semiconductor device. Application of the theoretical analysis of resonant tunnelling effect on double barriers was used to design and develop new structure and combination of materials for semiconductor device (diode, transistor, and integrated circuit).

Achievement report for fiscal 1998 on the research and development of quantum function device. Research on technological trend; 1998 nendo ryoshika kino soshi no kenkyu kaihatsu seika hokokusho. Gijutsu doko chosa kenkyu

Energy Technology Data Exchange (ETDEWEB)

NONE

1999-03-01

To effectively promote the research and development of quantum function devices, the advancement of the research and development concerned is surveyed and problems in the course of research and development are isolated, analyzed, and discussed, and a survey is conducted on technological trends. Researches are conducted through research committee meetings, on-the-spot surveys of overseas activities, and international conferences. As the result, reports are compiled on the integration of multi-value logic devices using tunnelling control function devices, integration of logic memory devices based on quantum levels, integration of quantum interband coupled multifunction devices, silicon insulation film tunnel memory device, mass dot function memory, quantum wave switching function device, integration of single electron logic devices, integration of CMOS coupled type single electron devices, basic technology of single electron device, etc. As for common basic technology, an integrated device in which a quantum function element and CMOS are merged, superspeed quantum device using light, spontaneous formation of InGaN quantum dot and GaSb/GaAs quantum dot, electron moderation mechanism in quantum dot, etc., are compiled into reports. (NEDO)

Spin-dependent tunneling transport into CrO2 nanorod devices with nonmagnetic contacts.

Science.gov (United States)

Song, Yipu; Schmitt, Andrew L; Jin, Song

2008-08-01

Single-crystal nanorods of half-metallic chromium dioxide (CrO2) were synthesized and structurally characterized. Spin-dependent electrical transport was investigated in individual CrO2 nanorod devices contacted with nonmagnetic metallic electrodes. Negative magnetoresistance (MR) was observed at low temperatures due to the spin-dependent direct tunneling through the contact barrier and the high spin polarization in the half-metallic nanorods. The magnitude of this negative magnetoresistance decreases with increasing bias voltage and temperature due to spin-independent inelastic hopping through the barrier, and a small positive magnetoresistance was found at room temperature. It is believed that the contact barrier and the surface state of the nanorods have great influence on the spin-dependent transport limiting the magnitude of MR effect in this first attempt at spin filter devices of CrO2 nanorods with nonmagnetic contacts.

Enhanced voltage-controlled magnetic anisotropy in magnetic tunnel junctions with an MgO/PZT/MgO tunnel barrier

Science.gov (United States)

Chien, Diana; Li, Xiang; Wong, Kin; Zurbuchen, Mark A.; Robbennolt, Shauna; Yu, Guoqiang; Tolbert, Sarah; Kioussis, Nicholas; Khalili Amiri, Pedram; Wang, Kang L.; Chang, Jane P.

2016-03-01

Compared with current-controlled magnetization switching in a perpendicular magnetic tunnel junction (MTJ), electric field- or voltage-induced magnetization switching reduces the writing energy of the memory cell, which also results in increased memory density. In this work, an ultra-thin PZT film with high dielectric constant was integrated into the tunneling oxide layer to enhance the voltage-controlled magnetic anisotropy (VCMA) effect. The growth of MTJ stacks with an MgO/PZT/MgO tunnel barrier was performed using a combination of sputtering and atomic layer deposition techniques. The fabricated MTJs with the MgO/PZT/MgO barrier demonstrate a VCMA coefficient, which is ˜40% higher (19.8 ± 1.3 fJ/V m) than the control sample MTJs with an MgO barrier (14.3 ± 2.7 fJ/V m). The MTJs with the MgO/PZT/MgO barrier also possess a sizeable tunneling magnetoresistance (TMR) of more than 50% at room temperature, comparable to the control MTJs with an MgO barrier. The TMR and enhanced VCMA effect demonstrated simultaneously in this work make the MgO/PZT/MgO barrier-based MTJs potential candidates for future voltage-controlled, ultralow-power, and high-density magnetic random access memory devices.

Quantum dot resonant tunneling diode single photon detector with aluminum oxide aperture defined tunneling area

DEFF Research Database (Denmark)

Li, H.W.; Kardynal, Beata; Ellis, D.J.P.

2008-01-01

Quantum dot resonant tunneling diode single photon detector with independently defined absorption and sensing areas is demonstrated. The device, in which the tunneling is constricted to an aperture in an insulating layer in the emitter, shows electrical characteristics typical of high quality res...

Integration Research on Gas Turbine and Tunnel Kiln Combined System

Science.gov (United States)

Shi, Hefei; Ma, Liangdong; Liu, Mingsheng

2018-04-01

Through the integrated modeling of gas turbine and tunnel kiln combined system, a thermodynamic calculation method of combined system is put forward, and the combined system operation parameters are obtained. By this method, the optimization of the combined system is analyzed and the optimal configuration of the gas turbine is calculated. At the same time, the thermal efficiency of the combined system is analyzed, and the heat distribution and thermal efficiency of the system before and after the improvement are explained. Taking the 1500 kg/h ceramic production as an example, pointed out that if the tunnel kiln has a gas turbine with a power of 342 kw. The amount of electricity of the combined system that produced per unit volume of the fuel which consumes more than it used to will be 7.19 kwh, the system thermal efficiency will reach 57.49%, which higher than the individual gas turbine’s cycle thermal efficiency 20% at least.

Proton tunneling in solids

Energy Technology Data Exchange (ETDEWEB)

Kondo, J.

1998-10-01

The tunneling rate of the proton and its isotopes between interstitial sites in solids is studied theoretically. The phonons and/or the electrons in the solid have two effects on the tunneling phenomenon. First, they suppress the transfer integral between two neighbouring states. Second, they give rise to a finite lifetime of the proton state. Usually the second effect is large and the tunneling probability per unit time (tunneling rate) can be defined. In some cases, however, a coherent tunneling is expected and actually observed. (author)

Proton tunneling in solids

International Nuclear Information System (INIS)

Kondo, J.

1998-01-01

The tunneling rate of the proton and its isotopes between interstitial sites in solids is studied theoretically. The phonons and/or the electrons in the solid have two effects on the tunneling phenomenon. First, they suppress the transfer integral between two neighbouring states. Second, they give rise to a finite lifetime of the proton state. Usually the second effect is large and the tunneling probability per unit time (tunneling rate) can be defined. In some cases, however, a coherent tunneling is expected and actually observed. (author)

Integrated Ultrasonic-Photonic Devices

DEFF Research Database (Denmark)

Barretto, Elaine Cristina Saraiva

in channel waveguides and Mach-Zehnder interferometers. Numerical models are developed based on the finite element method, and applied to several scenarios, such as optimization of the geometrical parameters of waveguides, use of slow light in photonic crystal waveguides and use of Lamb waves in membranized......This thesis deals with the modeling, design, fabrication and characterization of integrated ultrasonic-photonic devices, with particular focus on the use of standard semiconductor materials such as GaAs and silicon. The devices are based on the use of guided acoustic waves to modulate the light...... investigated. Comparisons are made with the numerical and experimental results, and they validate the obtained response of the acoustic and photonic components of the device. Finally, a new design for an optical frequency shifter is proposed, posing several advantages over existing devices in terms of size...

The anisotropic tunneling behavior of spin transport in graphene-based magnetic tunneling junction

Science.gov (United States)

Pan, Mengchun; Li, Peisen; Qiu, Weicheng; Zhao, Jianqiang; Peng, Junping; Hu, Jiafei; Hu, Jinghua; Tian, Wugang; Hu, Yueguo; Chen, Dixiang; Wu, Xuezhong; Xu, Zhongjie; Yuan, Xuefeng

2018-05-01

Due to the theoretical prediction of large tunneling magnetoresistance (TMR), graphene-based magnetic tunneling junction (MTJ) has become an important branch of high-performance spintronics device. In this paper, the non-collinear spin filtering and transport properties of MTJ with the Ni/tri-layer graphene/Ni structure were studied in detail by utilizing the non-equilibrium Green's formalism combined with spin polarized density functional theory. The band structure of Ni-C bonding interface shows that Ni-C atomic hybridization facilitates the electronic structure consistency of graphene and nickel, which results in a perfect spin filtering effect for tri-layer graphene-based MTJ. Furthermore, our theoretical results show that the value of tunneling resistance changes with the relative magnetization angle of two ferromagnetic layers, displaying the anisotropic tunneling behavior of graphene-based MTJ. This originates from the resonant conduction states which are strongly adjusted by the relative magnetization angles. In addition, the perfect spin filtering effect is demonstrated by fitting the anisotropic conductance with the Julliere's model. Our work may serve as guidance for researches and applications of graphene-based spintronics device.

Path integral approach to multidimensional quantum tunnelling

International Nuclear Information System (INIS)

Balantekin, A.B.; Takigawa, N.

1985-01-01

Path integral formulation of the coupled channel problem in the case of multidimensional quantum tunneling is presented and two-time influence functionals are introduced. The two-time influence functionals are calculated explicitly for the three simplest cases: Harmonic oscillators linearly or quadratically coupled to the translational motion and a system with finite number of equidistant energy levels linearly coupled to the translational motion. The effects of these couplings on the transmission probability are studied for two limiting cases, adiabatic case and when the internal system has a degenerate energy spectrum. The condition for the transmission probability to show a resonant structure is discussed and exemplified. Finally, the properties of the dissipation factor in the adiabatic limit and its correlation with the friction coefficient in the classically accessible region are studied

Small-size low-temperature scanning tunnel microscope

International Nuclear Information System (INIS)

Al'tfeder, I.B.; Khajkin, M.S.

1989-01-01

A small-size scanning tunnel microscope, designed for operation in transport helium-filled Dewar flasks is described. The microscope design contains a device moving the pin to the tested sample surface and a piezoelectric fine positioning device. High vibration protection of the microscope is provided by its suspension using silk threads. The small-size scanning tunnel microscope provides for atomic resolution

FUNDAMENTAL TUNNELING PROCESSES IN MOSa SOLAR CELLS

OpenAIRE

Balberg , I.; Hanak , J.; Weakliem , H.; Gal , E.

1981-01-01

In previous studies of tunneling through a MOSa tunnel junction, where Sa was a-Si : H, it was shown that their characteristics resemble those of MOSc devices where Sc was crystalline silicon. In the present work we would like to report a demonstration of fundamental tunneling processes in such tunnel junctions. In particular, the transition from semiconductor controlled regime to tunneling controlled regime can be clearly distinguished. The present results represent one of the rare cases whe...

Rectified tunneling current response of bio-functionalized metal-bridge-metal junctions.

Science.gov (United States)

Liu, Yaqing; Offenhäusser, Andreas; Mayer, Dirk

2010-01-15

Biomolecular bridged nanostructures allow direct electrical addressing of electroactive biomolecules, which is of interest for the development of bioelectronic and biosensing hybrid junctions. In the present paper, the electroactive biomolecule microperoxidase-11 (MP-11) was integrated into metal-bridge-metal (MBM) junctions assembled from a scanning tunneling microscope (STM) setup. Before immobilization of MP-11, the Au working electrode was first modified by a self-assembled monolayer of 1-undecanethiol (UDT). A symmetric and potential independent response of current-bias voltage (I(t)/V(b)) was observed for the Au (substrate)/UDT/Au (tip) junction. However, the I(t)/V(b) characteristics became potential dependent and asymmetrical after binding of MP-11 between the electrodes of the junction. The rectification ratio of the asymmetric current response varies with gate electrode modulation. A resonant tunneling process between metal electrode and MP-11 enhances the tunneling current and is responsible for the observed rectification. Our investigations demonstrated that functional building blocks of proteins can be reassembled into new conceptual devices with operation modes deviating from their native function, which could prove highly useful in the design of future biosensors and bioelectronic devices. Copyright 2009 Elsevier B.V. All rights reserved.

Integrated Optical lightguide device

NARCIS (Netherlands)

Heideman, Rene; Lambeck, Paul; Veldhuis, G.J.

2005-01-01

In an integrated optical lightguide device including a light-transmitting core layer, an inclusion or buffer layer, and an active or cladding layer. The cladding layer is divided into segments. Groups of different segments exhibit different refractive indices, light intensity profiles or different

Integrated Optical lightguide device

NARCIS (Netherlands)

Heideman, Rene; Lambeck, Paul; Veldhuis, G.J.

2000-01-01

In an integrated optical lightguide device including a light-transmitting core layer, an inclusion or buffer layer, and an active or cladding layer. The cladding layer is divided into segments. Groups of different segments exhibit different refractive indices, light intensity profiles or different

Spin-filter scanning tunneling microscopy : a novel technique for the analysis of spin polarization on magnetic surfaces and spintronic devices

NARCIS (Netherlands)

Vera Marun, I.J.

2010-01-01

This thesis deals with the development of a versatile technique to measure spin polarization with atomic resolution. A microscopy technique that can measure electronic spin polarization is relevant for characterization of magnetic nanostructures and spintronic devices. Scanning tunneling microscopy

Effect of an Interfacial Layer on Electron Tunneling through Atomically Thin Al2O3 Tunnel Barriers.

Science.gov (United States)

Wilt, Jamie; Sakidja, Ridwan; Goul, Ryan; Wu, Judy Z

2017-10-25

Electron tunneling through high-quality, atomically thin dielectric films can provide a critical enabling technology for future microelectronics, bringing enhanced quantum coherent transport, fast speed, small size, and high energy efficiency. A fundamental challenge is in controlling the interface between the dielectric and device electrodes. An interfacial layer (IL) will contain defects and introduce defects in the dielectric film grown atop, preventing electron tunneling through the formation of shorts. In this work, we present the first systematic investigation of the IL in Al 2 O 3 dielectric films of 1-6 Å's in thickness on an Al electrode. We integrated several advanced approaches: molecular dynamics to simulate IL formation, in situ high vacuum sputtering atomic layer deposition (ALD) to synthesize Al 2 O 3 on Al films, and in situ ultrahigh vacuum scanning tunneling spectroscopy to probe the electron tunneling through the Al 2 O 3 . The IL had a profound effect on electron tunneling. We observed a reduced tunnel barrier height and soft-type dielectric breakdown which indicate that defects are present in both the IL and in the Al 2 O 3 . The IL forms primarily due to exposure of the Al to trace O 2 and/or H 2 O during the pre-ALD heating step of fabrication. As the IL was systematically reduced, by controlling the pre-ALD sample heating, we observed an increase of the ALD Al 2 O 3 barrier height from 0.9 to 1.5 eV along with a transition from soft to hard dielectric breakdown. This work represents a key step toward the realization of high-quality, atomically thin dielectrics with electron tunneling for the next generation of microelectronics.

Magnitude of the current in 2D interlayer tunneling devices.

Science.gov (United States)

Feenstra, Randall M; de la Barrera, Sergio C; Li, Jun; Nie, Yifan; Cho, Kyeongjae

2018-01-15

Using the Bardeen tunneling method with first-principles wave functions, computations are made of the tunneling current in graphene/hexagonal-boron-nitride/graphene (G/h-BN/G) vertical structures. Detailed comparison with prior experimental results is made, focusing on the magnitude of the achievable tunnel current. With inclusion of the effects of translational and rotational misalignment of the graphene and the h-BN, predicted currents are found to be about 15×  larger than experimental values. A reduction in this discrepancy, to a factor of 2.5×, is achieved by utilizing a realistic size for the band gap of the h-BN, hence affecting the exponential decay constant for the tunneling.

Magnitude of the Current in Two-Dimensional Interlayer Tunneling Devices.

Science.gov (United States)

Feenstra, Randall; de la Barrera, Sergio; Li, Jun; Nie, Yifan; Cho, Kyeongjae

2018-01-02

Using the Bardeen tunneling method with first-principles wave functions, computations are made of the tunneling current in graphene / hexagonal-boron-nitride / graphene (G/h-BN/G) vertical structures. Detailed comparison with prior experimental results is made, focusing on the magnitude of the achievable tunnel current. With inclusion of the effects of translational and rotational misalignment of the graphene and the h-BN, predicted currents are found to be about 15x larger than experimental values. A reduction in this discrepancy, to a factor of 2.5x, is achieved by utilizing a realistic size for the band gap of the h-BN, hence affecting the exponential decay constant for the tunneling. © 2018 IOP Publishing Ltd.

Thermionic cooling devices based on resonant-tunneling AlGaAs/GaAs heterostructure

Science.gov (United States)

Bescond, M.; Logoteta, D.; Michelini, F.; Cavassilas, N.; Yan, T.; Yangui, A.; Lannoo, M.; Hirakawa, K.

2018-02-01

We study by means of full quantum simulations the operating principle and performance of a semiconductor heterostructure refrigerator combining resonant tunneling filtering and thermionic emission. Our model takes into account the coupling between the electric and thermal currents by self-consistently solving the transport equations within the non-equilibrium Green’s function framework and the heat equation. We show that the device can achieve relatively high cooling power values, while in the considered implementation, the maximum lattice temperature drop is severely limited by the thermal conductivity of the constituting materials. In such an out-of-equilibrium structure, we then emphasize the significant deviation of the phonon temperature from its electronic counterpart which can vary over several hundred Kelvin. The interplay between those two temperatures and the impact on the electrochemical potential is also discussed. Finally, viable options toward an optimization of the device are proposed.

Design and electrical performance of CdS/Sb2Te3 tunneling heterojunction devices

Science.gov (United States)

Khusayfan, Najla M.; Qasrawi, A. F.; Khanfar, Hazem K.

2018-02-01

In the current work, a tunneling barrier device made of 20 nm thick Sb2Te3 layer deposited onto 500 nm thick CdS is designed and characterized. The design included a Yb metallic substrate and Ag point contact of area of 10-3 cm2. The heterojunction properties are investigated by means of x-ray diffraction and impedance spectroscopy techniques. It is observed that the coating of the Sb2Te3 onto the surface of CdS causes a further deformation to the already strained structure of hexagonal CdS. The designed energy band diagram for the CdS/Sb2Te3 suggests a straddling type of heterojunction with an estimated conduction and valence band offsets of 0.35 and 1.74 eV, respectively. In addition, the analysis of the capacitance-voltage characteristic curve revealed a depletion region width of 14 nm. On the other hand, the capacitance and conductivity spectra which are analyzed in the frequency domain of 0.001-1.80 GHz indicated that the conduction in the device is dominated by the quantum mechanical tunneling in the region below 0.26 GHz and by the correlated barrier hopping in the remaining region. While the modeling of the conductivity spectra allowed investigation of the density of states near Fermi levels and an average scattering time of 1.0 ns, the capacitance spectra exhibited resonance at 0.26 GHz followed by negative differential capacitance effect in the frequency domain of 0.26-1.8 GHz. Furthermore, the evaluation of the impedance and reflection coefficient spectra indicated the usability of these devices as wide range low pass filters with ideal values of voltage standing wave ratios.

Homoepitaxial graphene tunnel barriers for spin transport (Presentation Recording)

Science.gov (United States)

Friedman, Adam L.

2015-09-01

Tunnel barriers are key elements for both charge-and spin-based electronics, offering devices with reduced power consumption and new paradigms for information processing. Such devices require mating dissimilar materials, raising issues of heteroepitaxy, interface stability, and electronic states that severely complicate fabrication and compromise performance. Graphene is the perfect tunnel barrier. It is an insulator out-of-plane, possesses a defect-free, linear habit, and is impervious to interdiffusion. Nonetheless, true tunneling between two stacked graphene layers is not possible in environmental conditions (magnetic field, temperature, etc.) usable for electronics applications. However, two stacked graphene layers can be decoupled using chemical functionalization. Here, we demonstrate homoepitaxial tunnel barrier devices in which graphene serves as both the tunnel barrier and the high mobility transport channel. Beginning with multilayer graphene, we fluorinate or hydrogenate the top layer to decouple it from the bottom layer, so that it serves as a single monolayer tunnel barrier for both charge and spin injection into the lower graphene transport channel. We demonstrate successful tunneling by measuring non-linear IV curves, and a weakly temperature dependent zero bias resistance. We perform lateral transport of spin currents in non-local spin-valve structures and determine spin lifetimes with the non-local Hanle effect to be commensurate with previous studies (~200 ps). However, we also demonstrate the highest spin polarization efficiencies (~45%) yet measured in graphene-based spin devices [1]. [1] A.L. Friedman, et al., Homoepitaxial tunnel barriers with functionalized graphene-on-graphene for charge and spin transport, Nat. Comm. 5, 3161 (2014).

Resonant Tunneling Analog-To-Digital Converter

Science.gov (United States)

Broekaert, T. P. E.; Seabaugh, A. C.; Hellums, J.; Taddiken, A.; Tang, H.; Teng, J.; vanderWagt, J. P. A.

1995-01-01

As sampling rates continue to increase, current analog-to-digital converter (ADC) device technologies will soon reach a practical resolution limit. This limit will most profoundly effect satellite and military systems used, for example, for electronic countermeasures, electronic and signal intelligence, and phased array radar. New device and circuit concepts will be essential for continued progress. We describe a novel, folded architecture ADC which could enable a technological discontinuity in ADC performance. The converter technology is based on the integration of multiple resonant tunneling diodes (RTD) and hetero-junction transistors on an indium phosphide substrate. The RTD consists of a layered semiconductor hetero-structure AlAs/InGaAs/AlAs(2/4/2 nm) clad on either side by heavily doped InGaAs contact layers. Compact quantizers based around the RTD offer a reduction in the number of components and a reduction in the input capacitance Because the component count and capacitance scale with the number of bits N, rather than by 2 (exp n) as in the flash ADC, speed can be significantly increased, A 4-bit 2-GSps quantizer circuit is under development to evaluate the performance potential. Circuit designs for ADC conversion with a resolution of 6-bits at 25GSps may be enabled by the resonant tunneling approach.

Simplified nonplanar wafer bonding for heterogeneous device integration

Science.gov (United States)

Geske, Jon; Bowers, John E.; Riley, Anton

2004-07-01

We demonstrate a simplified nonplanar wafer bonding technique for heterogeneous device integration. The improved technique can be used to laterally integrate dissimilar semiconductor device structures on a lattice-mismatched substrate. Using the technique, two different InP-based vertical-cavity surface-emitting laser active regions have been integrated onto GaAs without compromising the quality of the photoluminescence. Experimental and numerical simulation results are presented.

FY 1999 report on the research and development project of industrial scientific technology - quantum functional devices. Systematical arrangement of the development technology (FY 1991 - 1999); 1999 nendo ryoshika kino soshi no kenkyu kaihatsu. Kaihatsu sareta gijutsu no keitoteki seiri (1991 nendo kara 1999 nendo)

Energy Technology Data Exchange (ETDEWEB)

NONE

2000-03-01

The FY 1991 to 1999 R and D results of quantum functional devices are systematically summarized. The basic action of the MIM-based single electron tunneling devices is succeeded for the first time in the world. The quantum fine-wire device transistor is realized. The surface tunnel transistor is proposed, application to action demonstration and memories is suggested, and possibility of applicability to multi-value logic circuits is suggested. The multi-emitter RHET is developed to have one device provided with memory and multi-input logic functions, and increase integration 10 times. The TSR quantum dot HEMT memory is developed on a trial basis, to demonstrate 150 K action. The principle of a tera-bit class high-capacity memory is demonstrated using the InAs dot memory. Integration of the quantum band-bonded multi-functional device is described. Possibility is demonstrated for the Si insulation film tunnel device multi-value memory, working on the principle of tunneling between bands via the Si insulation film. The integrated quantum dot functional memory and polariton switch are also described. The single electron logic circuit works for the first time in the world. The integrated CMOS/SET device, which uses high driving force of CMOS, is proposed. (NEDO)

A method to design high SNR nanoscale magnetic sensors using an array of tunnelling magneto-resistance (TMR) devices

International Nuclear Information System (INIS)

Gomez, P; Litvinov, D; Khizroev, S

2007-01-01

This paper presents a systematic method to design and calculate tunnelling magneto-resistance (TMR) sensors with high signal-to-noise ratio (SNR). The sensing module consists of four TMR devices arranged in a Wheatstone-bridge configuration. Closed-form equations were obtained to calculate TMR sensor current, array output voltage, magneto-resistance ratio, overall noise (thermal and shot) and SNR for a given bandwidth. Using this technique we were able to maximize the SNR by tuning the many parameters of the TMR devices. Typical SNR values are in excess of 45 dB

InP tunnel junction for InGaAs/InP tandem solar cells

Science.gov (United States)

Vilela, M. F.; Freundlich, A.; Bensaoula, A.; Medelci, N.; Renaud, P.

1995-01-01

Chemical beam epitaxy (CBE) has been shown to allow the growth of high quality materials with reproducible complex compositional and doping profiles. The main advantage of CBE compared to metalorganic chemical vapor deposition (MOCVD), the most popular technique for InP-based photovoltaic device fabrication, is the ability to grow high purity epilayers at much lower temperatures (450-530 C). We have previously shown that CBE is perfectly suited toward the fabrication of complex photovoltaic devices such as InP/InGaAs monolithically integrated tandem solar cells, because its low process temperature preserves the electrical characteristics of the InGaAs tunnel junction commonly used as an ohmic interconnect. In this work using CBE for the fabrication of optically transparent (with respect to the bottom cell) InP tunnel diodes is demonstrated. Epitaxial growth were performed in a Riber CBE 32 system using PH3 and TMIn as III and V precursors. Solid Be (p-type) and Si (n-type) have been used as doping sources, allowing doping levels up to 2 x 10(exp -19)/cu cm and 1 x 10(exp -19)/cu cm for n and p type respectively. The InP tunnel junction characteristics and the influence of the growth's conditions (temperature, growth rate) over its performance have been carefully investigated. InP p(++)/n(++) tunnel junction with peak current densities up to 1600 A/sq cm and maximum specific resistivities (V(sub p)/I(sub p) - peak voltage to peak current ratio) in the range of 10(exp -4) Omega-sq cm were obtained. The obtained peak current densities exceed the highest results previously reported for their lattice matched counterparts, In(0.53)Ga( 0.47)As and should allow the realization of improved minimal absorption losses in the interconnect InP/InGaAs tandem devices for Space applications. Owing to the low process temperature required for the top cell, these devices exhibit almost no degradation of its characteristics after the growth of subsequent thick InP layer suggesting

Spin polarized electron tunneling and magnetoresistance in molecular junctions.

Science.gov (United States)

Szulczewski, Greg

2012-01-01

This chapter reviews tunneling of spin-polarized electrons through molecules positioned between ferromagnetic electrodes, which gives rise to tunneling magnetoresistance. Such measurements yield important insight into the factors governing spin-polarized electron injection into organic semiconductors, thereby offering the possibility to manipulate the quantum-mechanical spin degrees of freedom for charge carriers in optical/electrical devices. In the first section of the chapter a brief description of the Jullière model of spin-dependent electron tunneling is reviewed. Next, a brief description of device fabrication and characterization is presented. The bulk of the review highlights experimental studies on spin-polarized electron tunneling and magnetoresistance in molecular junctions. In addition, some experiments describing spin-polarized scanning tunneling microscopy/spectroscopy on single molecules are mentioned. Finally, some general conclusions and prospectus on the impact of spin-polarized tunneling in molecular junctions are offered.

Development of an integrated pointing device driver for the disabled.

Science.gov (United States)

Shih, Ching-Hsiang; Shih, Ching-Tien

2010-01-01

To help people with disabilities such as those with spinal cord injury (SCI) to effectively utilise commercial pointing devices to operate computers. This study proposes a novel method to integrate the functions of commercial pointing devices. Utilising software technology to develop an integrated pointing device driver (IPDD) for a computer operating system. The proposed IPDD has the following benefits: (1) it does not require additional hardware cost or circuit preservations, (2) it supports all standard interfaces of commercial pointing devices, including PS/2, USB and wireless interfaces and (3) it can integrate any number of devices. The IPDD can be selected and combined according to their physical restriction. The IPDD is a novel method of integrating commercial pointing devices. Through IPDD, people with disabilities can choose a suitable combination of commercial pointing devices to achieve full cursor control and optimise operational performance. In contrast with previous studies, the software-based solution does not require additional hardware or circuit preservations, and it can support unlimited devices. In summary, the IPDD has the benefits of flexibility, low cost and high-device compatibility.

Dual metal gate tunneling field effect transistors based on MOSFETs: A 2-D analytical approach

Science.gov (United States)

Ramezani, Zeinab; Orouji, Ali A.

2018-01-01

A novel 2-D analytical drain current model of novel Dual Metal Gate Tunnel Field Effect Transistors Based on MOSFETs (DMG-TFET) is presented in this paper. The proposed Tunneling FET is extracted from a MOSFET structure by employing an additional electrode in the source region with an appropriate work function to induce holes in the N+ source region and hence makes it as a P+ source region. The electric field is derived which is utilized to extract the expression of the drain current by analytically integrating the band to band tunneling generation rate in the tunneling region based on the potential profile by solving the Poisson's equation. Through this model, the effects of the thin film thickness and gate voltage on the potential, the electric field, and the effects of the thin film thickness on the tunneling current can be studied. To validate our present model we use SILVACO ATLAS device simulator and the analytical results have been compared with it and found a good agreement.

Interlayer tunnel field-effect transistor (ITFET): physics, fabrication and applications

Science.gov (United States)

Kang, Sangwoo; Mou, Xuehao; Fallahazad, Babak; Prasad, Nitin; Wu, Xian; Valsaraj, Amithraj; Movva, Hema C. P.; Kim, Kyounghwan; Tutuc, Emanuel; Register, Leonard F.; Banerjee, Sanjay K.

2017-09-01

The scaling challenges of complementary metal oxide semiconductors (CMOS) are increasing with the pace of scaling showing marked signs of slowing down. This slowing has brought about a widespread search for an alternative beyond-CMOS device concept. While the charge tunneling phenomenon has been known for almost a century, and tunneling based transistors have been studied in the past few decades, its possibilities are being re-examined with the emergence of a new class of two-dimensional (2D) materials. By stacking varying 2D materials together, with two electrode layers sandwiching a tunnel dielectric layer, it could be possible to make vertical tunnel transistors without the limitations that have plagued such devices implemented within other material systems. When the two electrode layers are of the same material, under certain conditions, one can achieve resonant tunneling between the two layers, manifesting as negative differential resistance (NDR) in the interlayer current-voltage characteristics. We call this type of device an interlayer tunnel FET (ITFET). We review the basic operation principles of this device, experimental and theoretical studies, and benchmark simulation results for several digital logic gates based on a compact model that we developed. The results are placed in the context of work going on in other groups.

Tunneling Negative Magnetoresistance via δ Doping in a Graphene-Based Magnetic Tunnel Junction

International Nuclear Information System (INIS)

Yuan Jian-Hui; Chen Ni; Mo Hua; Zhang Yan; Zhang Zhi-Hai

2016-01-01

We investigate the tunneling magnetoresistance via δ doping in a graphene-based magnetic tunnel junction in detail. It is found that the transmission probability and the conductance oscillates with the position and the aptitude of the δ doping. Also, both the transmission probability and the conductance at the parallel configuration are suppressed by the magnetic field more obviously than that at the antiparallel configuration, which implies a large negative magnetoresistance for this device. The results show that the negative magnetoresistance of over 300% at B = 1.0 T is observed by choosing suitable doped parameters, and the temperature plays an important role in the magnetoresistance. Thus it is possible to open a way to effectively manipulate the magnetoresistance devices, and to make a type of magnetoresistance device by controlling the structural parameter of the δ doping. (paper)

Flexible MgO Barrier Magnetic Tunnel Junctions.

Science.gov (United States)

Loong, Li Ming; Lee, Wonho; Qiu, Xuepeng; Yang, Ping; Kawai, Hiroyo; Saeys, Mark; Ahn, Jong-Hyun; Yang, Hyunsoo

2016-07-01

Flexible MgO barrier magnetic tunnel junction (MTJ) devices are fabricated using a transfer printing process. The flexible MTJ devices yield significantly enhanced tunneling magnetoresistance of ≈300% and improved abruptness of switching, as residual strain in the MTJ structure is released during the transfer process. This approach could be useful for flexible electronic systems that require high-performance memory components. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Band structure effects on resonant tunneling in III-V quantum wells versus two-dimensional vertical heterostructures

Energy Technology Data Exchange (ETDEWEB)

Campbell, Philip M., E-mail: philip.campbell@gatech.edu [School of Materials Science and Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332 (United States); Electronic Systems Laboratory, Georgia Tech Research Institute, Atlanta, Georgia 30332 (United States); Tarasov, Alexey; Joiner, Corey A.; Vogel, Eric M. [School of Materials Science and Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332 (United States); Ready, W. Jud [Electronic Systems Laboratory, Georgia Tech Research Institute, Atlanta, Georgia 30332 (United States)

2016-01-14

Since the invention of the Esaki diode, resonant tunneling devices have been of interest for applications including multi-valued logic and communication systems. These devices are characterized by the presence of negative differential resistance in the current-voltage characteristic, resulting from lateral momentum conservation during the tunneling process. While a large amount of research has focused on III-V material systems, such as the GaAs/AlGaAs system, for resonant tunneling devices, poor device performance and device-to-device variability have limited widespread adoption. Recently, the symmetric field-effect transistor (symFET) was proposed as a resonant tunneling device incorporating symmetric 2-D materials, such as transition metal dichalcogenides (TMDs), separated by an interlayer barrier, such as hexagonal boron-nitride. The achievable peak-to-valley ratio for TMD symFETs has been predicted to be higher than has been observed for III-V resonant tunneling devices. This work examines the effect that band structure differences between III-V devices and TMDs has on device performance. It is shown that tunneling between the quantized subbands in III-V devices increases the valley current and decreases device performance, while the interlayer barrier height has a negligible impact on performance for barrier heights greater than approximately 0.5 eV.

Band structure effects on resonant tunneling in III-V quantum wells versus two-dimensional vertical heterostructures

Science.gov (United States)

Campbell, Philip M.; Tarasov, Alexey; Joiner, Corey A.; Ready, W. Jud; Vogel, Eric M.

2016-01-01

Since the invention of the Esaki diode, resonant tunneling devices have been of interest for applications including multi-valued logic and communication systems. These devices are characterized by the presence of negative differential resistance in the current-voltage characteristic, resulting from lateral momentum conservation during the tunneling process. While a large amount of research has focused on III-V material systems, such as the GaAs/AlGaAs system, for resonant tunneling devices, poor device performance and device-to-device variability have limited widespread adoption. Recently, the symmetric field-effect transistor (symFET) was proposed as a resonant tunneling device incorporating symmetric 2-D materials, such as transition metal dichalcogenides (TMDs), separated by an interlayer barrier, such as hexagonal boron-nitride. The achievable peak-to-valley ratio for TMD symFETs has been predicted to be higher than has been observed for III-V resonant tunneling devices. This work examines the effect that band structure differences between III-V devices and TMDs has on device performance. It is shown that tunneling between the quantized subbands in III-V devices increases the valley current and decreases device performance, while the interlayer barrier height has a negligible impact on performance for barrier heights greater than approximately 0.5 eV.

Charge Transport in 2D DNA Tunnel Junction Diodes

KAUST Repository

Yoon, Minho

2017-11-06

Recently, deoxyribonucleic acid (DNA) is studied for electronics due to its intrinsic benefits such as its natural plenitude, biodegradability, biofunctionality, and low-cost. However, its applications are limited to passive components because of inherent insulating properties. In this report, a metal-insulator-metal tunnel diode with Au/DNA/NiOx junctions is presented. Through the self-aligning process of DNA molecules, a 2D DNA nanosheet is synthesized and used as a tunneling barrier, and semitransparent conducting oxide (NiOx ) is applied as a top electrode for resolving metal penetration issues. This molecular device successfully operates as a nonresonant tunneling diode, and temperature-variable current-voltage analysis proves that Fowler-Nordheim tunneling is a dominant conduction mechanism at the junctions. DNA-based tunneling devices appear to be promising prototypes for nanoelectronics using biomolecules.

Charge Transport in 2D DNA Tunnel Junction Diodes

KAUST Repository

Yoon, Minho; Min, Sung-Wook; Dugasani, Sreekantha Reddy; Lee, Yong Uk; Oh, Min Suk; Anthopoulos, Thomas D.; Park, Sung Ha; Im, Seongil

2017-01-01

Recently, deoxyribonucleic acid (DNA) is studied for electronics due to its intrinsic benefits such as its natural plenitude, biodegradability, biofunctionality, and low-cost. However, its applications are limited to passive components because of inherent insulating properties. In this report, a metal-insulator-metal tunnel diode with Au/DNA/NiOx junctions is presented. Through the self-aligning process of DNA molecules, a 2D DNA nanosheet is synthesized and used as a tunneling barrier, and semitransparent conducting oxide (NiOx ) is applied as a top electrode for resolving metal penetration issues. This molecular device successfully operates as a nonresonant tunneling diode, and temperature-variable current-voltage analysis proves that Fowler-Nordheim tunneling is a dominant conduction mechanism at the junctions. DNA-based tunneling devices appear to be promising prototypes for nanoelectronics using biomolecules.

Superconducting tunnel-junction refrigerator

International Nuclear Information System (INIS)

Melton, R.G.; Paterson, J.L.; Kaplan, S.B.

1980-01-01

The dc current through an S 1 -S 2 tunnel junction, with Δ 2 greater than Δ 1 , when biased with eV 1 +Δ 2 , will lower the energy in S 1 . This energy reduction will be shared by the phonons and electrons. This device is shown to be analogous to a thermoelectric refrigerator with an effective Peltier coefficient π* approx. Δ 1 /e. Tunneling calculations yield the cooling power P/sub c/, the electrical power P/sub e/ supplied by the bias supply, and the cooling efficiency eta=P/sub c//P/sub e/. The maximum cooling power is obtained for eV= +- (Δ 2 -Δ 1 ) and t 1 =T 1 /T/sub c/1 approx. 0.9. Estimates are made of the temperature difference T 2 -T 1 achievable in Al-Pb and Sn-Pb junctions with an Al 2 O 3 tunneling barrier. The performance of this device is shown to yield a maximum cooling efficiency eta approx. = Δ 1 /(Δ 2 -Δ 1 ) which can be compared with that available in an ideal Carnot refrigerator of eta=T 1 /(T 2 -T 1 ). The development of a useful tunnel-junction refrigerator requires a tunneling barrier with an effective thermal conductance per unit area several orders of magnitude less than that provided by the A1 2 O 3 barrier in the Al-Pb and Sn-Pb systems

High current density 2D/3D MoS2/GaN Esaki tunnel diodes

Science.gov (United States)

Krishnamoorthy, Sriram; Lee, Edwin W.; Lee, Choong Hee; Zhang, Yuewei; McCulloch, William D.; Johnson, Jared M.; Hwang, Jinwoo; Wu, Yiying; Rajan, Siddharth

2016-10-01

The integration of two-dimensional materials such as transition metal dichalcogenides with bulk semiconductors offer interesting opportunities for 2D/3D heterojunction-based device structures without any constraints of lattice matching. By exploiting the favorable band alignment at the GaN/MoS2 heterojunction, an Esaki interband tunnel diode is demonstrated by transferring large area Nb-doped, p-type MoS2 onto heavily n-doped GaN. A peak current density of 446 A/cm2 with repeatable room temperature negative differential resistance, peak to valley current ratio of 1.2, and minimal hysteresis was measured in the MoS2/GaN non-epitaxial tunnel diode. A high current density of 1 kA/cm2 was measured in the Zener mode (reverse bias) at -1 V bias. The GaN/MoS2 tunnel junction was also modeled by treating MoS2 as a bulk semiconductor, and the electrostatics at the 2D/3D interface was found to be crucial in explaining the experimentally observed device characteristics.

Si light-emitting device in integrated photonic CMOS ICs

Science.gov (United States)

Xu, Kaikai; Snyman, Lukas W.; Aharoni, Herzl

2017-07-01

The motivation for integrated Si optoelectronics is the creation of low-cost photonics for mass-market applications. Especially, the growing demand for sensitive biochemical sensors in the environmental control or medicine leads to the development of integrated high resolution sensors. Here CMOS-compatible Si light-emitting device structures are presented for investigating the effect of various depletion layer profiles and defect engineering on the photonic transition in the 1.4-2.8 eV. A novel Si device is proposed to realize both a two-terminal Si-diode light-emitting device and a three-terminal Si gate-controlled diode light-emitting device in the same device structure. In addition to the spectral analysis, differences between two-terminal and three-terminal devices are discussed, showing the light emission efficiency change. The proposed Si optical source may find potential applications in micro-photonic systems and micro-optoelectro-mechanical systems (MOEMS) in CMOS integrated circuitry.

Integrated Photonic Devices Incorporating Low-Loss Fluorinated Polymer Materials

Directory of Open Access Journals (Sweden)

Hyung-Jong Lee

2011-06-01

Full Text Available Low-loss polymer materials incorporating fluorinated compounds have been utilized for the investigation of various functional optical devices useful for optical communication and optical sensor systems. Since reliability issues concerning the polymer device have been resolved, polymeric waveguide devices have been gradually adopted for commercial application systems. The two most successfully commercialized polymeric integrated optic devices, variable optical attenuators and digital optical switches, are reviewed in this paper. Utilizing unique properties of optical polymers which are not available in other optical materials, novel polymeric optical devices are proposed including widely tunable external cavity lasers and integrated optical current sensors.

Fabrication of magnetic tunnel junctions connected through a continuous free layer to enable spin logic devices

Science.gov (United States)

Wan, Danny; Manfrini, Mauricio; Vaysset, Adrien; Souriau, Laurent; Wouters, Lennaert; Thiam, Arame; Raymenants, Eline; Sayan, Safak; Jussot, Julien; Swerts, Johan; Couet, Sebastien; Rassoul, Nouredine; Babaei Gavan, Khashayar; Paredis, Kristof; Huyghebaert, Cedric; Ercken, Monique; Wilson, Christopher J.; Mocuta, Dan; Radu, Iuliana P.

2018-04-01

Magnetic tunnel junctions (MTJs) interconnected via a continuous ferromagnetic free layer were fabricated for spin torque majority gate (STMG) logic. The MTJs are biased independently and show magnetoelectric response under spin transfer torque. The electrical control of these devices paves the way to future spin logic devices based on domain wall (DW) motion. In particular, it is a significant step towards the realization of a majority gate. To our knowledge, this is the first fabrication of a cross-shaped free layer shared by several perpendicular MTJs. The fabrication process can be generalized to any geometry and any number of MTJs. Thus, this framework can be applied to other spin logic concepts based on magnetic interconnect. Moreover, it allows exploration of spin dynamics for logic applications.

Reactive tunnel junctions in electrically driven plasmonic nanorod metamaterials

Science.gov (United States)

Wang, Pan; Krasavin, Alexey V.; Nasir, Mazhar E.; Dickson, Wayne; Zayats, Anatoly V.

2018-02-01

Non-equilibrium hot carriers formed near the interfaces of semiconductors or metals play a crucial role in chemical catalysis and optoelectronic processes. In addition to optical illumination, an efficient way to generate hot carriers is by excitation with tunnelling electrons. Here, we show that the generation of hot electrons makes the nanoscale tunnel junctions highly reactive and facilitates strongly confined chemical reactions that can, in turn, modulate the tunnelling processes. We designed a device containing an array of electrically driven plasmonic nanorods with up to 1011 tunnel junctions per square centimetre, which demonstrates hot-electron activation of oxidation and reduction reactions in the junctions, induced by the presence of O2 and H2 molecules, respectively. The kinetics of the reactions can be monitored in situ following the radiative decay of tunnelling-induced surface plasmons. This electrically driven plasmonic nanorod metamaterial platform can be useful for the development of nanoscale chemical and optoelectronic devices based on electron tunnelling.

Tunnel junctions with multiferroic barriers

Science.gov (United States)

Gajek, Martin; Bibes, Manuel; Fusil, Stéphane; Bouzehouane, Karim; Fontcuberta, Josep; Barthélémy, Agnès; Fert, Albert

2007-04-01

Multiferroics are singular materials that can exhibit simultaneously electric and magnetic orders. Some are ferroelectric and ferromagnetic and provide the opportunity to encode information in electric polarization and magnetization to obtain four logic states. However, such materials are rare and schemes allowing a simple electrical readout of these states have not been demonstrated in the same device. Here, we show that films of La0.1Bi0.9MnO3 (LBMO) are ferromagnetic and ferroelectric, and retain both ferroic properties down to a thickness of 2nm. We have integrated such ultrathin multiferroic films as barriers in spin-filter-type tunnel junctions that exploit the magnetic and ferroelectric degrees of freedom of LBMO. Whereas ferromagnetism permits read operations reminiscent of magnetic random access memories (MRAM), the electrical switching evokes a ferroelectric RAM write operation. Significantly, our device does not require the destructive ferroelectric readout, and therefore represents an advance over the original four-state memory concept based on multiferroics.

A Seamless Ubiquitous Telehealthcare Tunnel

Directory of Open Access Journals (Sweden)

Sao-Jie Chen

2013-08-01

Full Text Available Mobile handheld devices are rapidly using to implement healthcare services around the World. Fundamentally, these services utilize telemedicine technologies. A disconnection of a mobile telemedicine system usually results in an interruption, which is embarrassing, and reconnection is necessary during the communication session. In this study, the Stream Control Transmission Protocol (SCTP is adopted to build a stable session tunnel to guarantee seamless switching among heterogeneous wireless communication standards, such as Wi-Fi and 3G. This arrangement means that the telemedicine devices will not be limited by a fixed wireless connection and can switch to a better wireless channel if necessary. The tunnel can transmit plain text, binary data, and video streams. According to the evaluation of the proposed software-based SCTP-Tunnel middleware shown, the performance is lower than anticipated and is slightly slower than a fixed connection. However, the transmission throughput is still acceptable for healthcare professionals in a healthcare enterprise or home care site. It is necessary to build more heterogeneous wireless protocols into the proposed tunnel-switching scheme to support all possible communication protocols. In addition, SCTP is another good choice for promoting communication in telemedicine and healthcare fields.

Atomic layer deposition for graphene device integration

NARCIS (Netherlands)

Vervuurt, R.H.J.; Kessels, W.M.M.; Bol, A.A.

2017-01-01

Graphene is a two dimensional material with extraordinary properties, which make it an interesting material for many optical and electronic devices. The integration of graphene in these devices often requires the deposition of thin dielectric layers on top of graphene. Atomic layer deposition (ALD)

Integration in design and manufacturing of polymer smart devices

NARCIS (Netherlands)

Bolt, P.J.; Zwart, R.M. de; Tacken, R.A.; Rendering, H.

2009-01-01

Integration of functions in single components is pursued in order to manufacture smaller and smarter polymer micro devices at less cost, through e.g. less assembly steps. It requires integration on both product and production side. This paper addresses the use of molded interconnect device (MID)

N-state random switching based on quantum tunnelling

Science.gov (United States)

Bernardo Gavito, Ramón; Jiménez Urbanos, Fernando; Roberts, Jonathan; Sexton, James; Astbury, Benjamin; Shokeir, Hamzah; McGrath, Thomas; Noori, Yasir J.; Woodhead, Christopher S.; Missous, Mohamed; Roedig, Utz; Young, Robert J.

2017-08-01

In this work, we show how the hysteretic behaviour of resonant tunnelling diodes (RTDs) can be exploited for new functionalities. In particular, the RTDs exhibit a stochastic 2-state switching mechanism that could be useful for random number generation and cryptographic applications. This behaviour can be scaled to N-bit switching, by connecting various RTDs in series. The InGaAs/AlAs RTDs used in our experiments display very sharp negative differential resistance (NDR) peaks at room temperature which show hysteresis cycles that, rather than having a fixed switching threshold, show a probability distribution about a central value. We propose to use this intrinsic uncertainty emerging from the quantum nature of the RTDs as a source of randomness. We show that a combination of two RTDs in series results in devices with three-state outputs and discuss the possibility of scaling to N-state devices by subsequent series connections of RTDs, which we demonstrate for the up to the 4-state case. In this work, we suggest using that the intrinsic uncertainty in the conduction paths of resonant tunnelling diodes can behave as a source of randomness that can be integrated into current electronics to produce on-chip true random number generators. The N-shaped I-V characteristic of RTDs results in a two-level random voltage output when driven with current pulse trains. Electrical characterisation and randomness testing of the devices was conducted in order to determine the validity of the true randomness assumption. Based on the results obtained for the single RTD case, we suggest the possibility of using multi-well devices to generate N-state random switching devices for their use in random number generation or multi-valued logic devices.

Electron tunneling in proteins program.

Science.gov (United States)

Hagras, Muhammad A; Stuchebrukhov, Alexei A

2016-06-05

We developed a unique integrated software package (called Electron Tunneling in Proteins Program or ETP) which provides an environment with different capabilities such as tunneling current calculation, semi-empirical quantum mechanical calculation, and molecular modeling simulation for calculation and analysis of electron transfer reactions in proteins. ETP program is developed as a cross-platform client-server program in which all the different calculations are conducted at the server side while only the client terminal displays the resulting calculation outputs in the different supported representations. ETP program is integrated with a set of well-known computational software packages including Gaussian, BALLVIEW, Dowser, pKip, and APBS. In addition, ETP program supports various visualization methods for the tunneling calculation results that assist in a more comprehensive understanding of the tunneling process. © 2016 Wiley Periodicals, Inc. © 2016 Wiley Periodicals, Inc.

Hybrid tunnel junction contacts to III–nitride light-emitting diodes

KAUST Repository

Young, Erin C.; Yonkee, Benjamin P.; Wu, Feng; Oh, Sang Ho; DenBaars, Steven P.; Nakamura, Shuji; Speck, James S.

2016-01-01

In this work, we demonstrate highly doped GaN p–n tunnel junction (TJ) contacts on III–nitride heterostructures where the active region of the device and the top p-GaN layers were grown by metal organic chemical vapor deposition and highly doped n-GaN was grown by NH3 molecular beam epitaxy to form the TJ. The regrowth interface in these hybrid devices was found to have a high concentration of oxygen, which likely enhanced tunneling through the diode. For optimized regrowth, the best tunnel junction device had a total differential resistivity of 1.5 × 10−4 Ω cm2, including contact resistance. As a demonstration, a blue-light-emitting diode on a ($20\\bar{2}\\bar{1}$) GaN substrate with a hybrid tunnel junction and an n-GaN current spreading layer was fabricated and compared with a reference sample with a transparent conducting oxide (TCO) layer. The tunnel junction LED showed a lower forward operating voltage and a higher efficiency at a low current density than the TCO LED.

Hybrid tunnel junction contacts to III–nitride light-emitting diodes

KAUST Repository

Young, Erin C.

2016-01-26

In this work, we demonstrate highly doped GaN p–n tunnel junction (TJ) contacts on III–nitride heterostructures where the active region of the device and the top p-GaN layers were grown by metal organic chemical vapor deposition and highly doped n-GaN was grown by NH3 molecular beam epitaxy to form the TJ. The regrowth interface in these hybrid devices was found to have a high concentration of oxygen, which likely enhanced tunneling through the diode. For optimized regrowth, the best tunnel junction device had a total differential resistivity of 1.5 × 10−4 Ω cm2, including contact resistance. As a demonstration, a blue-light-emitting diode on a ($20\\\\bar{2}\\\\bar{1}$) GaN substrate with a hybrid tunnel junction and an n-GaN current spreading layer was fabricated and compared with a reference sample with a transparent conducting oxide (TCO) layer. The tunnel junction LED showed a lower forward operating voltage and a higher efficiency at a low current density than the TCO LED.

Tunnel magnetoresistance in thermally robust Mo/CoFeB/MgO tunnel junction with perpendicular magnetic anisotropy

Directory of Open Access Journals (Sweden)

B. Fang

2015-06-01

Full Text Available We report on tunnel magnetoresistance and electric-field effect in the Mo buffered and capped CoFeB/MgO magnetic tunnel junctions (MTJs with perpendicular magnetic anisotropy. A large tunnel magnetoresistance of 120% is achieved. Furthermore, this structure shows greatly improved thermal stability and stronger electric-field-induced modulation effect in comparison with the Ta/CoFeB/MgO-based MTJs. These results suggest that the Mo-based MTJs are more desirable for next generation spintronic devices.

Design and simulation of nanoscale double-gate TFET/tunnel CNTFET

Science.gov (United States)

Bala, Shashi; Khosla, Mamta

2018-04-01

A double-gate tunnel field-effect transistor (DG tunnel FET) has been designed and investigated for various channel materials such as silicon (Si), gallium arsenide (GaAs), alminium gallium arsenide (Al x Ga1‑x As) and CNT using a nano ViDES Device and TCAD SILVACO ATLAS simulator. The proposed devices are compared on the basis of inverse subthreshold slope (SS), I ON/I OFF current ratio and leakage current. Using Si as the channel material limits the property to reduce leakage current with scaling of channel, whereas the Al x Ga1‑x As based DG tunnel FET provides a better I ON/I OFF current ratio (2.51 × 106) as compared to other devices keeping the leakage current within permissible limits. The performed silmulation of the CNT based channel in the double-gate tunnel field-effect transistor using the nano ViDES shows better performace for a sub-threshold slope of 29.4 mV/dec as the channel is scaled down. The proposed work shows the potential of the CNT channel based DG tunnel FET as a futuristic device for better switching and high retention time, which makes it suitable for memory based circuits.

A Study of Vertical Transport through Graphene toward Control of Quantum Tunneling.

Science.gov (United States)

Zhu, Xiaodan; Lei, Sidong; Tsai, Shin-Hung; Zhang, Xiang; Liu, Jun; Yin, Gen; Tang, Min; Torres, Carlos M; Navabi, Aryan; Jin, Zehua; Tsai, Shiao-Po; Qasem, Hussam; Wang, Yong; Vajtai, Robert; Lake, Roger K; Ajayan, Pulickel M; Wang, Kang L

2018-02-14

Vertical integration of van der Waals (vdW) materials with atomic precision is an intriguing possibility brought forward by these two-dimensional (2D) materials. Essential to the design and analysis of these structures is a fundamental understanding of the vertical transport of charge carriers into and across vdW materials, yet little has been done in this area. In this report, we explore the important roles of single layer graphene in the vertical tunneling process as a tunneling barrier. Although a semimetal in the lateral lattice plane, graphene together with the vdW gap act as a tunneling barrier that is nearly transparent to the vertically tunneling electrons due to its atomic thickness and the transverse momenta mismatch between the injected electrons and the graphene band structure. This is accentuated using electron tunneling spectroscopy (ETS) showing a lack of features corresponding to the Dirac cone band structure. Meanwhile, the graphene acts as a lateral conductor through which the potential and charge distribution across the tunneling barrier can be tuned. These unique properties make graphene an excellent 2D atomic grid, transparent to charge carriers, and yet can control the carrier flux via the electrical potential. A new model on the quantum capacitance's effect on vertical tunneling is developed to further elucidate the role of graphene in modulating the tunneling process. This work may serve as a general guideline for the design and analysis of vdW vertical tunneling devices and heterostructures, as well as the study of electron/spin injection through and into vdW materials.

Spin tunneling and manipulation in nanostructures.

Science.gov (United States)

Sherman, E Ya; Ban, Yue; Gulyaev, L V; Khomitsky, D V

2012-09-01

The results for joint effects of tunneling and spin-orbit coupling on spin dynamics in nanostructures are presented for systems with discrete and continuous spectra. We demonstrate that tunneling plays the crucial role in the spin dynamics and the abilities of spin manipulation by external electric field. This result can be important for design of nanostructures-based spintronics devices.

Structure factors for tunneling ionization rates of molecules: General Hartree-Fock-based integral representation

Science.gov (United States)

Madsen, Lars Bojer; Jensen, Frank; Dnestryan, Andrey I.; Tolstikhin, Oleg I.

2017-07-01

In the leading-order approximation of the weak-field asymptotic theory (WFAT), the dependence of the tunneling ionization rate of a molecule in an electric field on its orientation with respect to the field is determined by the structure factor of the ionizing molecular orbital. The WFAT yields an expression for the structure factor in terms of a local property of the orbital in the asymptotic region. However, in general quantum chemistry approaches molecular orbitals are expanded in a Gaussian basis which does not reproduce their asymptotic behavior correctly. This hinders the application of the WFAT to polyatomic molecules, which are attracting increasing interest in strong-field physics. Recently, an integral-equation approach to the WFAT for tunneling ionization of one electron from an arbitrary potential has been developed. The structure factor is expressed in an integral form as a matrix element involving the ionizing orbital. The integral is not sensitive to the asymptotic behavior of the orbital, which resolves the difficulty mentioned above. Here, we extend the integral representation for the structure factor to many-electron systems treated within the Hartree-Fock method and show how it can be implemented on the basis of standard quantum chemistry software packages. We validate the methodology by considering noble-gas atoms and the CO molecule, for which accurate structure factors exist in the literature. We also present benchmark results for CO2 and for NH3 in the pyramidal and planar geometries.

Sidewall GaAs tunnel junctions fabricated using molecular layer epitaxy

Directory of Open Access Journals (Sweden)

Takeo Ohno and Yutaka Oyama

2012-01-01

Full Text Available In this article we review the fundamental properties and applications of sidewall GaAs tunnel junctions. Heavily impurity-doped GaAs epitaxial layers were prepared using molecular layer epitaxy (MLE, in which intermittent injections of precursors in ultrahigh vacuum were applied, and sidewall tunnel junctions were fabricated using a combination of device mesa wet etching of the GaAs MLE layer and low-temperature area-selective regrowth. The fabricated tunnel junctions on the GaAs sidewall with normal mesa orientation showed a record peak current density of 35 000 A cm-2. They can potentially be used as terahertz devices such as a tunnel injection transit time effect diode or an ideal static induction transistor.

Doped Josephson tunneling junction for use in a sensitive IR detector

International Nuclear Information System (INIS)

Fletcher, J.C.; Saffren, M.M.

1975-01-01

A superconductive tunneling device having a modified tunnel barrier capable of supporting Josephson tunneling current is provided. The tunnel barrier located between a pair of electrodes includes a molecular species which is capable of coupling incident radiation of a spectrum characteristic of the molecular species into the tunnel barrier. The coupled radiation modulates the known Josephson characteristics of the superconducting device. As a result of the present invention, a superconductive tunneling device can be tuned or made sensitive to a particular radiation associated with the dopant molecular species. The present invention is particularly useful in providing an improved infrared detector. The tunnel barrier region can be, for example, an oxide of an electrode or frozen gas. The molecular species can be intermixed with the barrier region such as the frozen gas or deposited as one or more layers of molecules on the barrier region. The deposited molecules of the molecular species are unbonded and capable of responding to a radiation characteristic of the molecules. Semi-conductor material can be utilized as the molecular species to provide an increased selective bandwidth response. Finally, appropriate detector equipment can be utilized to measure the modulation of any of the Josephson characteristics such as critical current, voltage steps, Lambe-Jaklevic peaks and plasma frequency. (auth)

Characterization of 10,12-pentacosadiynoic acid Langmuir–Blodgett monolayers and their use in metal–insulator–metal tunnel devices

Directory of Open Access Journals (Sweden)

Saumya Sharma

2014-11-01

Full Text Available The characterization of Langmuir–Blodgett thin films of 10,12-pentacosadiynoic acid (PDA and their use in metal–insulator–metal (MIM devices were studied. The Langmuir monolayer behavior of the PDA film was studied at the air/water interface using surface tension–area isotherms of polymeric and monomeric PDA. Langmuir–Blodgett (LB, vertical deposition and Langmuir–Schaefer (LS, horizontal deposition techniques were used to deposit the PDA film on various substrates (glass, quartz, silicon, and nickel-coated film on glass. The electrochemical, electrical and optical properties of the LB and LS PDA films were studied using cyclic voltammetry, current–voltage characteristics (I–V, and UV–vis and FTIR spectroscopies. Atomic force microscopy measurements were performed in order to analyze the surface morphology and roughness of the films. A MIM tunnel diode was fabricated using a PDA monolayer assembly as the insulating barrier, which was sandwiched between two nickel layers. The precise control of the thickness of the insulating monolayers proved critical for electron tunneling to take place in the MIM structure. The current–voltage characteristics of the MIM diode revealed tunneling behavior in the fabricated Ni–PDA LB film–Ni structures.

Large-scale fabrication of BN tunnel barriers for graphene spintronics

International Nuclear Information System (INIS)

Fu, Wangyang; Makk, Péter; Maurand, Romain; Bräuninger, Matthias; Schönenberger, Christian

2014-01-01

We have fabricated graphene spin-valve devices utilizing scalable materials made from chemical vapor deposition (CVD). Both the spin-transporting graphene and the tunnel barrier material are CVD-grown. The tunnel barrier is realized by Hexagonal boron nitride, used either as a monolayer or bilayer and placed over the graphene. Spin transport experiments were performed using ferromagnetic contacts deposited onto the barrier. We find that spin injection is still greatly suppressed in devices with a monolayer tunneling barrier due to resistance mismatch. This is, however, not the case for devices with bilayer barriers. For those devices, a spin relaxation time of ∼260 ps intrinsic to the CVD graphene material is deduced. This time scale is comparable to those reported for exfoliated graphene, suggesting that this CVD approach is promising for spintronic applications which require scalable materials

Adaptation of the model of tunneling in a metal/CaF{sub 2}/Si(111) system for use in industrial simulators of MIS devices

Energy Technology Data Exchange (ETDEWEB)

Vexler, M. I., E-mail: shulekin@mail.ioffe.ru; Illarionov, Yu. Yu.; Tyaginov, S. E. [Russian Academy of Sciences, Ioffe Physical-Technical Institute (Russian Federation); Grasser, T. [Institute for Microelectronics, TU Vienna (Austria)

2015-02-15

An approach toward simplification of the model of the tunneling transport of electrons through a thin layer of crystalline calcium fluoride into a silicon (111) substrate with subsequent implementation in simulators of semiconductor devices is suggested. The validity of the approach is proven by comparing the results of modeling using simplified formulas with the results of precise calculations and experimental data. The approach can be applied to calculations of tunneling currents in structures with any crystalline insulators on Si (111)

New Knowledge of tunneling from photonic experiments

International Nuclear Information System (INIS)

Nimtz, G.

1997-01-01

Photonic experiments have shown, that the propagation of evanescent (tunneling) modes can proceed at speeds faster than the velocity of light in vacuum (superluminal). The superluminal velocities include signal and energy propagation. The analogy between the classical Helmholtz equation and the quantum mechanical Schroedinger equation was quantitatively proved in classical photonic experiments. The Hartman effect, i.e. the prediction that the tunneling time is independent of the barrier length was for the first time evidenced in a photonic analogous tunneling experiment by Enders and Nimtz. It is also shown, that the resonant state life time is not determined by the barrier traversal time. For electronic tunneling devices it follows, that the quantum mechanical phase time calculations indeed deliver the relevant intrinsic tunneling time and consequently allow to predict the dynamical specification of a device. The present theoretical descriptions of the propagation of evanescent modes is not fully compatible with the experimental situation. Superluminal signal and energy transport has been measured, and this has to be properly analyzed. May the advanced field solutions help to obtain a satisfactory theoretical description of the recent experimental results of the propagation of evanescent modes? (author)

Resonant Tunneling in Gated Vertical One- dimensional Structures

Science.gov (United States)

Kolagunta, V. R.; Janes, D. B.; Melloch, M. R.; Webb, K. J.

1997-03-01

Vertical sub-micron transistors incorporating resonant tunneling multiple quantum well heterostructures are interesting in applications for both multi-valued logic devices and the study of quantization effects in vertical quasi- one-, zero- dimensional structures. Earlier we have demonstrated room temperature pinch-off of the resonant peak in sub-micron vertical resonant tunneling transistors structures using a self-aligned sidewall gating technique ( V.R. Kolagunta et. al., Applied Physics Lett., 69), 374(1996). In this paper we present the study of gating effects in vertical multiple quantum well resonant tunneling transistors. Multiple well quasi-1-D sidewall gated transistors with mesa dimensions of L_x=0.5-0.9μm and L_y=10-40μm were fabricated. The quantum heterostructure in these devices consists of two non-symmetric (180 ÅÅi-GaAs wells separated from each other and from the top and bottom n^+ GaAs/contacts region using Al_0.3Ga_0.7As tunneling barriers. Room temperature pinch-off of the multiple resonant peaks similar to that reported in the case of single well devices is observed in these devices^1. Current-voltage characteristics at liquid nitrogen temperatures show splitting of the resonant peaks into sub-bands with increasing negative gate bias indicative of quasi- 1-D confinement. Room-temperature and low-temperature current-voltage measurements shall be presented and discussed.

Analytical modeling of Schottky tunneling source impact ionization MOSFET with reduced breakdown voltage

Directory of Open Access Journals (Sweden)

Sangeeta Singh

2016-03-01

Full Text Available In this paper, we have investigated a novel Schottky tunneling source impact ionization MOSFET (STS-IMOS to lower the breakdown voltage of conventional impact ionization MOS (IMOS and developed an analytical model for the same. In STS-IMOS there is an accumulative effect of both impact ionization and source induced barrier tunneling. The silicide source offers very low parasitic resistance, the outcome of which is an increment in voltage drop across the intrinsic region for the same applied bias. This reduces operating voltage and hence, it exhibits a significant reduction in both breakdown and threshold voltage. STS-IMOS shows high immunity against hot electron damage. As a result of this the device reliability increases magnificently. The analytical model for impact ionization current (Iii is developed based on the integration of ionization integral (M. Similarly, to get Schottky tunneling current (ITun expression, Wentzel–Kramers–Brillouin (WKB approximation is employed. Analytical models for threshold voltage and subthreshold slope is optimized against Schottky barrier height (ϕB variation. The expression for the drain current is computed as a function of gate-to-drain bias via integral expression. It is validated by comparing it with the technology computer-aided design (TCAD simulation results as well. In essence, this analytical framework provides the physical background for better understanding of STS-IMOS and its performance estimation.

A review on all-perovskite multiferroic tunnel junctions

Directory of Open Access Journals (Sweden)

Yuewei Yin

2017-12-01

Full Text Available Although the basic concept was proposed only about 10 years ago, multiferroic tunnel junctions (MFTJs with a ferroelectric barrier sandwiched between two ferromagnetic electrodes have already drawn considerable interests, driven mainly by its potential applications in multi-level memories and electric field controlled spintronics. The purpose of this article is to review the recent progress of all-perovskite MFTJs. Starting from the key functional properties of the tunneling magnetoresistance, tunneling electroresistance, and tunneling electromagnetoresistance effects, we discuss the main origins of the tunneling electroresistance effect, recent progress in achieving multilevel resistance states in a single device, and the electrical control of spin polarization and transport through the ferroelectric polarization reversal of the tunneling barrier.

Modeling of switching energy of magnetic tunnel junction devices with tilted magnetization

International Nuclear Information System (INIS)

Surawanitkun, C.; Kaewrawang, A.; Siritaratiwat, A.; Kruesubthaworn, A.; Sivaratana, R.; Jutong, N.; Mewes, C.K.A.; Mewes, T.

2015-01-01

For spin transfer torque (STT), the switching energy and thermal stability of magnetic tunnel junctions (MTJ) bits utilized in memory devices are important factors that have to be considered simultaneously. In this article, we examined the minimum energy for STT induced magnetization switching in MTJ devices for different in-plane angles of the magnetization in the free layer and the pinned layer with respect to the major axis of the elliptical cylinder of the cell. Simulations were performed by comparing the analytical solution with macrospin and full micromagnetic calculations. The results show good agreement of the switching energy calculated by using the three approaches for different initial angles of the magnetization of the free layer. Also, the low-energy location specifies the suitable value of both time and current in order to reduce the heat effect during the switching process. - Highlights: • Switching energy model was firstly examined with tiled magnetization in STT-RAM. • Simulation was performed by analytical solution, macrospin and micromagnetic models. • Low energy results from three models show agreement for tilt angle in free layer. • We also found an optimal tilt angle of the pinned layer. • Low-energy location specifies the suitable switching location to reduce heat effect

Features of carrier tunneling between the silicon valence band and metal in devices based on the Al/high-K oxide/SiO_2/Si structure

International Nuclear Information System (INIS)

Vexler, M. I.; Grekhov, I. V.

2016-01-01

The features of electron tunneling from or into the silicon valence band in a metal–insulator–semiconductor system with the HfO_2(ZrO_2)/SiO_2 double-layer insulator are theoretically analyzed for different modes. It is demonstrated that the valence-band current plays a less important role in structures with HfO_2(ZrO_2)/SiO_2 than in structures containing only silicon dioxide. In the case of a very wide-gap high-K oxide ZrO_2, nonmonotonic behavior related to tunneling through the upper barrier is predicted for the valence-band–metal current component. The use of an insulator stack can offer certain advantages for some devices, including diodes, bipolar tunnel-emitter transistors, and resonant-tunneling diodes, along with the traditional use of high-K insulators in a field-effect transistor.

Strain-enhanced tunneling magnetoresistance in MgO magnetic tunnel junctions.

Science.gov (United States)

Loong, Li Ming; Qiu, Xuepeng; Neo, Zhi Peng; Deorani, Praveen; Wu, Yang; Bhatia, Charanjit S; Saeys, Mark; Yang, Hyunsoo

2014-09-30

While the effects of lattice mismatch-induced strain, mechanical strain, as well as the intrinsic strain of thin films are sometimes detrimental, resulting in mechanical deformation and failure, strain can also be usefully harnessed for applications such as data storage, transistors, solar cells, and strain gauges, among other things. Here, we demonstrate that quantum transport across magnetic tunnel junctions (MTJs) can be significantly affected by the introduction of controllable mechanical strain, achieving an enhancement factor of ~2 in the experimental tunneling magnetoresistance (TMR) ratio. We further correlate this strain-enhanced TMR with coherent spin tunneling through the MgO barrier. Moreover, the strain-enhanced TMR is analyzed using non-equilibrium Green's function (NEGF) quantum transport calculations. Our results help elucidate the TMR mechanism at the atomic level and can provide a new way to enhance, as well as tune, the quantum properties in nanoscale materials and devices.

Tunnelling anisotropic magnetoresistance due to antiferromagnetic CoO tunnel barriers

Science.gov (United States)

Wang, K.; Sanderink, J. G. M.; Bolhuis, T.; van der Wiel, W. G.; de Jong, M. P.

2015-01-01

A new approach in spintronics is based on spin-polarized charge transport phenomena governed by antiferromagnetic (AFM) materials. Recent studies have demonstrated the feasibility of this approach for AFM metals and semiconductors. We report tunneling anisotropic magnetoresistance (TAMR) due to the rotation of antiferromagnetic moments of an insulating CoO layer, incorporated into a tunnel junction consisting of sapphire(substrate)/fcc-Co/CoO/AlOx/Al. The ferromagnetic Co layer is exchange coupled to the AFM CoO layer and drives rotation of the AFM moments in an external magnetic field. The results may help pave the way towards the development of spintronic devices based on AFM insulators. PMID:26486931

Manipulating the voltage dependence of tunneling spin torques

KAUST Repository

Manchon, Aurelien

2012-10-01

Voltage-driven spin transfer torques in magnetic tunnel junctions provide an outstanding tool to design advanced spin-based devices for memory and reprogrammable logic applications. The non-linear voltage dependence of the torque has a direct impact on current-driven magnetization dynamics and on devices performances. After a brief overview of the progress made to date in the theoretical description of the spin torque in tunnel junctions, I present different ways to alter and control the bias dependence of both components of the spin torque. Engineering the junction (barrier and electrodes) structural asymmetries or controlling the spin accumulation profile in the free layer offer promising tools to design effcient spin devices.

Simulation of single-electron tunnelling circuits using SPICE

NARCIS (Netherlands)

Van de Haar, R.

2004-01-01

Single-electron tunnelling (SET) devices have very promising properties, like their extremely low power consumption, their extremely high switching speeds and their extremely small physical dimensions. Since the field of SET devices is far from being fully exploited, and their device properties seem

Electrochemical device

Science.gov (United States)

Grimes, Patrick G.; Einstein, Harry; Bellows, Richard J.

1988-01-12

A tunnel protected electrochemical device features channels fluidically communicating between manifold, tunnels and cells. The channels are designed to provide the most efficient use of auxiliary power. The channels have a greater hydraulic pressure drop and electrical resistance than the manifold. This will provide a design with the optimum auxiliary energy requirements.

CMOS and BiCMOS process integration and device characterization

CERN Document Server

El-Kareh, Badih

2009-01-01

Covers both the theoretical and practical aspects of modern silicon devices and the relationship between their electrical properties and processing conditions. This book also covers silicon devices and integrated process technologies. It discusses modern silicon devices, their characteristics, and interactions with process parameters.

Wind tunnel study of natural ventilation of building integrated photovoltaics double skin façade

Science.gov (United States)

Hudişteanu, Sebastian Valeriu; Popovici, Cătălin George; Cherecheş, Nelu-Cristian

2018-02-01

The paper presents a wind tunnel experimental analysis of a small-scale building model (1:30). The objective of the study is to determine the wind influence on the ventilation of a double skin façade channel (DSF) and the cooling effect over integrated photovoltaic panels. The tests were achieved by conceiving and implementation of an experimental program using a wind tunnel with atmospheric boundary layer. The effect of the wind over the ventilation of the horizontal channels of double skin façades is evaluated for different incident velocities. The results are generalized for the average steady state values of the velocities analysed. The experimental results put in evidence the correlation between the reference wind velocity and the dynamics of the air movement inside the double skin façade. These values are used to determine the convective heat transfer and the cooling effect of the air streams inside the channel upon the integrated photovoltaic panels. The decrease of the photovoltaic panels temperature determines a raise of 11% in efficiency and power generated.

Wind tunnel study of natural ventilation of building integrated photovoltaics double skin façade

Directory of Open Access Journals (Sweden)

Hudişteanu Sebastian Valeriu

2018-01-01

Full Text Available The paper presents a wind tunnel experimental analysis of a small-scale building model (1:30. The objective of the study is to determine the wind influence on the ventilation of a double skin façade channel (DSF and the cooling effect over integrated photovoltaic panels. The tests were achieved by conceiving and implementation of an experimental program using a wind tunnel with atmospheric boundary layer. The effect of the wind over the ventilation of the horizontal channels of double skin façades is evaluated for different incident velocities. The results are generalized for the average steady state values of the velocities analysed. The experimental results put in evidence the correlation between the reference wind velocity and the dynamics of the air movement inside the double skin façade. These values are used to determine the convective heat transfer and the cooling effect of the air streams inside the channel upon the integrated photovoltaic panels. The decrease of the photovoltaic panels temperature determines a raise of 11% in efficiency and power generated.

Modulation of Quantum Tunneling via a Vertical Two-Dimensional Black Phosphorus and Molybdenum Disulfide p-n Junction.

Science.gov (United States)

Liu, Xiaochi; Qu, Deshun; Li, Hua-Min; Moon, Inyong; Ahmed, Faisal; Kim, Changsik; Lee, Myeongjin; Choi, Yongsuk; Cho, Jeong Ho; Hone, James C; Yoo, Won Jong

2017-09-26

Diverse diode characteristics were observed in two-dimensional (2D) black phosphorus (BP) and molybdenum disulfide (MoS 2 ) heterojunctions. The characteristics of a backward rectifying diode, a Zener diode, and a forward rectifying diode were obtained from the heterojunction through thickness modulation of the BP flake or back gate modulation. Moreover, a tunnel diode with a precursor to negative differential resistance can be realized by applying dual gating with a solid polymer electrolyte layer as a top gate dielectric material. Interestingly, a steep subthreshold swing of 55 mV/dec was achieved in a top-gated 2D BP-MoS 2 junction. Our simple device architecture and chemical doping-free processing guaranteed the device quality. This work helps us understand the fundamentals of tunneling in 2D semiconductor heterostructures and shows great potential in future applications in integrated low-power circuits.

Impact of device engineering on analog/RF performances of tunnel field effect transistors

Science.gov (United States)

Vijayvargiya, V.; Reniwal, B. S.; Singh, P.; Vishvakarma, S. K.

2017-06-01

The tunnel field effect transistor (TFET) and its analog/RF performance is being aggressively studied at device architecture level for low power SoC design. Therefore, in this paper we have investigated the influence of the gate-drain underlap (UL) and different dielectric materials for the spacer and gate oxide on DG-TFET (double gate TFET) and its analog/RF performance for low power applications. Here, it is found that the drive current behavior in DG-TFET with a UL feature while implementing dielectric material for the spacer is different in comparison to that of DG-FET. Further, hetero gate dielectric-based DG-TFET (HGDG-TFET) is more resistive against drain-induced barrier lowering (DIBL) as compared to DG-TFET with high-k (HK) gate dielectric. Along with that, as compared to DG-FET, this paper also analyses the attributes of UL and dielectric material on analog/RF performance of DG-TFET in terms of transconductance (gm ), transconductance generation factor (TGF), capacitance, intrinsic resistance (Rdcr), cut-off frequency (F T), and maximum oscillation frequency (F max). The LK spacer-based HGDG-TFET with a gate-drain UL has the potential to improve the RF performance of device.

Integrated Solar-Energy-Harvesting and -Storage Device

Science.gov (United States)

whitacre, Jay; Fleurial, Jean-Pierre; Mojarradi, Mohammed; Johnson, Travis; Ryan, Margaret Amy; Bugga, Ratnakumar; West, William; Surampudi, Subbarao; Blosiu, Julian

2004-01-01

A modular, integrated, completely solid-state system designed to harvest and store solar energy is under development. Called the power tile, the hybrid device consists of a photovoltaic cell, a battery, a thermoelectric device, and a charge-control circuit that are heterogeneously integrated to maximize specific energy capacity and efficiency. Power tiles could be used in a variety of space and terrestrial environments and would be designed to function with maximum efficiency in the presence of anticipated temperatures, temperature gradients, and cycles of sunlight and shadow. Because they are modular in nature, one could use a single power tile or could construct an array of as many tiles as needed. If multiple tiles are used in an array, the distributed and redundant nature of the charge control and distribution hardware provides an extremely fault-tolerant system. The figure presents a schematic view of the device.

Chaos regularization of quantum tunneling rates

International Nuclear Information System (INIS)

Pecora, Louis M.; Wu Dongho; Lee, Hoshik; Antonsen, Thomas; Lee, Ming-Jer; Ott, Edward

2011-01-01

Quantum tunneling rates through a barrier separating two-dimensional, symmetric, double-well potentials are shown to depend on the classical dynamics of the billiard trajectories in each well and, hence, on the shape of the wells. For shapes that lead to regular (integrable) classical dynamics the tunneling rates fluctuate greatly with eigenenergies of the states sometimes by over two orders of magnitude. Contrarily, shapes that lead to completely chaotic trajectories lead to tunneling rates whose fluctuations are greatly reduced, a phenomenon we call regularization of tunneling rates. We show that a random-plane-wave theory of tunneling accounts for the mean tunneling rates and the small fluctuation variances for the chaotic systems.

Size dependence of spin-torque induced magnetic switching in CoFeB-based perpendicular magnetization tunnel junctions (invited)

Science.gov (United States)

Sun, J. Z.; Trouilloud, P. L.; Gajek, M. J.; Nowak, J.; Robertazzi, R. P.; Hu, G.; Abraham, D. W.; Gaidis, M. C.; Brown, S. L.; O'Sullivan, E. J.; Gallagher, W. J.; Worledge, D. C.

2012-04-01

CoFeB-based magnetic tunnel junctions with perpendicular magnetic anisotropy are used as a model system for studies of size dependence in spin-torque-induced magnetic switching. For integrated solid-state memory applications, it is important to understand the magnetic and electrical characteristics of these magnetic tunnel junctions as they scale with tunnel junction size. Size-dependent magnetic anisotropy energy, switching voltage, apparent damping, and anisotropy field are systematically compared for devices with different materials and fabrication treatments. Results reveal the presence of sub-volume thermal fluctuation and reversal, with a characteristic length-scale of the order of approximately 40 nm, depending on the strength of the perpendicular magnetic anisotropy and exchange stiffness. To have the best spin-torque switching efficiency and best stability against thermal activation, it is desirable to optimize the perpendicular anisotropy strength with the junction size for intended use. It also is important to ensure strong exchange-stiffness across the magnetic thin film. These combine to give an exchange length that is comparable or larger than the lateral device size for efficient spin-torque switching.

Characteristics and optimisation of vertical and planar tunnelling-FETs

International Nuclear Information System (INIS)

Sterkel, M; Wang, P-F; Nirschl, T; Fabel, B; Bhuwalka, K K; Schulze, J; Eisele, I; Schmitt-Landsiedel, D; Hansch, W

2005-01-01

Scaling MOSFETs becomes more and more difficult. The tunnelling-FET is a possible successor of today's MOSFET with better scaling possibilities. Two different device structures, a vertical and a planar version of a tunnelling-FET are presented and evaluated

Integrating Touch-Enabled and Mobile Devices into Contemporary Mathematics Education

Science.gov (United States)

Meletiou-Mavrotheris, Maria, Ed.; Mavrou, Katerina, Ed.; Paparistodemou, Efi, Ed.

2015-01-01

Despite increased interest in mobile devices as learning tools, the amount of available primary research studies on their integration into mathematics teaching and learning is still relatively small due to the novelty of these technologies. "Integrating Touch-Enabled and Mobile Devices into Contemporary Mathematics Education" presents…

A full-duplex working integrated optoelectronic device for optical interconnect

Science.gov (United States)

Liu, Kai; Fan, Huize; Huang, Yongqing; Duan, Xiaofeng; Wang, Qi; Ren, Xiaomin; Wei, Qi; Cai, Shiwei

2018-05-01

In this paper, a full-duplex working integrated optoelectronic device is proposed. It is constructed by integrating a vertical cavity surface emitting laser (VCSEL) unit above a resonant cavity enhanced photodetector (RCE-PD) unit. Analysis shows that, the VCSEL unit has a threshold current of 1 mA and a slop efficiency of 0.66 W/A at 849.7 nm, the RCE-PD unit obtains its maximal absorption quantum efficiency of 90.24% at 811 nm with a FWHM of 4 nm. Moreover, the two units of the proposed integrated device can work independently from each other. So that the proposed integrated optoelectronic device can work full-duplex. It can be applied for single fiber bidirectional optical interconnects system.

Large current modulation and spin-dependent tunneling of vertical graphene/MoS2 heterostructures.

Science.gov (United States)

Myoung, Nojoon; Seo, Kyungchul; Lee, Seung Joo; Ihm, G

2013-08-27

Vertical graphene heterostructures have been introduced as an alternative architecture for electronic devices by using quantum tunneling. Here, we present that the current on/off ratio of vertical graphene field-effect transistors is enhanced by using an armchair graphene nanoribbon as an electrode. Moreover, we report spin-dependent tunneling current of the graphene/MoS2 heterostructures. When an atomically thin MoS2 layer sandwiched between graphene electrodes becomes magnetic, Dirac fermions with different spins feel different heights of the tunnel barrier, leading to spin-dependent tunneling. Our finding will develop the present graphene heterostructures for electronic devices by improving the device performance and by adding the possibility of spintronics based on graphene.

Performance analysis of AlGaAs/GaAs tunnel junctions for ultra-high concentration photovoltaics

International Nuclear Information System (INIS)

García, I; Rey-Stolle, I; Algora, C

2012-01-01

An n ++ -GaAs/p ++ -AlGaAs tunnel junction with a peak current density of 10 100 A cm -2 is developed. This device is a tunnel junction for multijunction solar cells, grown lattice-matched on standard GaAs or Ge substrates, with the highest peak current density ever reported. The voltage drop for a current density equivalent to the operation of the multijunction solar cell up to 10 000 suns is below 5 mV. Trap-assisted tunnelling is proposed to be behind this performance, which cannot be justified by simple band-to-band tunnelling. The metal-organic vapour-phase epitaxy growth conditions, which are in the limits of the transport-limited regime, and the heavy tellurium doping levels are the proposed origins of the defects enabling trap-assisted tunnelling. The hypothesis of trap-assisted tunnelling is supported by the observed annealing behaviour of the tunnel junctions, which cannot be explained in terms of dopant diffusion or passivation. For the integration of these tunnel junctions into a triple-junction solar cell, AlGaAs barrier layers are introduced to suppress the formation of parasitic junctions, but this is found to significantly degrade the performance of the tunnel junctions. However, the annealed tunnel junctions with barrier layers still exhibit a peak current density higher than 2500 A cm -2 and a voltage drop at 10 000 suns of around 20 mV, which are excellent properties for tunnel junctions and mean they can serve as low-loss interconnections in multijunction solar cells working at ultra-high concentrations. (paper)

Inelastic scattering in resonant tunneling

DEFF Research Database (Denmark)

Wingreen, Ned S.; Jacobsen, Karsten Wedel; Wilkins, John W.

1989-01-01

The exact resonant-tunneling transmission probability for an electron interacting with phonons is presented in the limit that the elastic coupling to the leads is independent of energy. The phonons produce transmission sidebands but do not affect the integrated transmission probability or the esc......The exact resonant-tunneling transmission probability for an electron interacting with phonons is presented in the limit that the elastic coupling to the leads is independent of energy. The phonons produce transmission sidebands but do not affect the integrated transmission probability...

A hybrid approach to device integration on a genetic analysis platform

International Nuclear Information System (INIS)

Brennan, Des; Justice, John; Aherne, Margaret; Galvin, Paul; Jary, Dorothee; Kurg, Ants; Berik, Evgeny; Macek, Milan

2012-01-01

Point-of-care (POC) systems require significant component integration to implement biochemical protocols associated with molecular diagnostic assays. Hybrid platforms where discrete components are combined in a single platform are a suitable approach to integration, where combining multiple device fabrication steps on a single substrate is not possible due to incompatible or costly fabrication steps. We integrate three devices each with a specific system functionality: (i) a silicon electro-wetting-on-dielectric (EWOD) device to move and mix sample and reagent droplets in an oil phase, (ii) a polymer microfluidic chip containing channels and reservoirs and (iii) an aqueous phase glass microarray for fluorescence microarray hybridization detection. The EWOD device offers the possibility of fully integrating on-chip sample preparation using nanolitre sample and reagent volumes. A key challenge is sample transfer from the oil phase EWOD device to the aqueous phase microarray for hybridization detection. The EWOD device, waveguide performance and functionality are maintained during the integration process. An on-chip biochemical protocol for arrayed primer extension (APEX) was implemented for single nucleotide polymorphism (SNiP) analysis. The prepared sample is aspirated from the EWOD oil phase to the aqueous phase microarray for hybridization. A bench-top instrumentation system was also developed around the integrated platform to drive the EWOD electrodes, implement APEX sample heating and image the microarray after hybridization. (paper)

"Size-Independent" Single-Electron Tunneling.

Science.gov (United States)

Zhao, Jianli; Sun, Shasha; Swartz, Logan; Riechers, Shawn; Hu, Peiguang; Chen, Shaowei; Zheng, Jie; Liu, Gang-Yu

2015-12-17

Incorporating single-electron tunneling (SET) of metallic nanoparticles (NPs) into modern electronic devices offers great promise to enable new properties; however, it is technically very challenging due to the necessity to integrate ultrasmall (<10 nm) particles into the devices. The nanosize requirements are intrinsic for NPs to exhibit quantum or SET behaviors, for example, 10 nm or smaller, at room temperature. This work represents the first observation of SET that defies the well-known size restriction. Using polycrystalline Au NPs synthesized via our newly developed solid-state glycine matrices method, a Coulomb Blockade was observed for particles as large as tens of nanometers, and the blockade voltage exhibited little dependence on the size of the NPs. These observations are counterintuitive at first glance. Further investigations reveal that each observed SET arises from the ultrasmall single crystalline grain(s) within the polycrystal NP, which is (are) sufficiently isolated from the nearest neighbor grains. This work demonstrates the concept and feasibility to overcome orthodox spatial confinement requirements to achieve quantum effects.

Thermal stability of tunneling spin polarization

International Nuclear Information System (INIS)

Kant, C.H.; Kohlhepp, J.T.; Paluskar, P.V.; Swagten, H.J.M.; Jonge, W.J.M. de

2005-01-01

We present a study of the thermal stability of tunneling spin polarization in Al/AlOx/ferromagnet junctions based on the spin-polarized tunneling technique, in which the Zeeman-split superconducting density of states in the Al electrode is used as a detector for the spin polarization. Thermal robustness of the polarization, which is of key importance for the performance of magnetic tunnel junction devices, is demonstrated for post-deposition anneal temperatures up to 500 o C with Co and Co 90 Fe 10 top electrodes, independent of the presence of an FeMn layer on top of the ferromagnet

Simulations of Resonant Intraband and Interband Tunneling Spin Filters

Science.gov (United States)

Ting, David; Cartoixa-Soler, Xavier; McGill, T. C.; Smith, Darryl L.; Schulman, Joel N.

2001-01-01

This viewgraph presentation reviews resonant intraband and interband tunneling spin filters It explores the possibility of building a zero-magnetic-field spin polarizer using nonmagnetic III-V semiconductor heterostructures. It reviews the extensive simulations of quantum transport in asymmetric InAs/GaSb/AlSb resonant tunneling structures with Rashba spin splitting and proposes a. new device concept: side-gated asymmetric Resonant Interband Tunneling Diode (a-RITD).

Extended device profiles and testing procedures for the approval process of integrated medical devices using the IEEE 11073 communication standard.

Science.gov (United States)

Janß, Armin; Thorn, Johannes; Schmitz, Malte; Mildner, Alexander; Dell'Anna-Pudlik, Jasmin; Leucker, Martin; Radermacher, Klaus

2018-02-23

Nowadays, only closed and proprietary integrated operating room systems (IORS) from big manufacturers are available on the market. Hence, the interconnection of components from third-party vendors is only possible with increased time and costs. In the context of the German Federal Ministry of Education and Research (BMBF)-funded project OR.NET (2012-2016), the open integration of medical devices from different manufacturers was addressed. An integrated operating theater based on the open communication standard IEEE 11073 shall give clinical operators the opportunity to choose medical devices independently of the manufacturer. This approach would be advantageous especially for hospital operators and small- and medium-sized enterprises (SME) of medical devices. Actual standards and concepts regarding technical feasibility and the approval process do not cope with the requirements for a modular integration of medical devices in the operating room (OR), based on an open communication standard. Therefore, innovative approval strategies and corresponding certification and test procedures, which cover actual legal and normative standards, have to be developed in order to support the future risk management and the usability engineering process of open integrated medical devices in the OR. The use of standardized device and service profiles and a three-step testing procedure, including conformity, interoperability and integration tests are described in this paper and shall support the manufacturers to integrate their medical devices without disclosing the medical devices' risk analysis and related confidential expertise or proprietary information.

Silicon nano crystal-based non-volatile memory devices

International Nuclear Information System (INIS)

Ng, C.Y.; Chen, T.P.; Sreeduth, D.; Chen, Q.; Ding, L.; Du, A.

2006-01-01

In this work, we have investigated the performance and reliability of a Flash memory based on silicon nanocrystal synthesized with very-low energy ion beams. The devices are fabricated with a conventional CMOS process and the size of the nanocrystal is ∼ 4 nm as determined from TEM measurement. Electrical properties of the devices with a tunnel oxide of either 3 nm or 7 nm are evaluated. The devices exhibit good endurance up to 10 5 W/E cycles even at the high operation temperature of 85 deg. C for both the tunnel oxide thicknesses. For the thicker tunnel oxide (i.e., the 7-nm tunnel oxide), a good retention performance with an extrapolated 10-year memory window of ∼ 0.3 V (or ∼ 20% of charge lose after 10 years) is achieved. However, ∼ 70% of charge loss after 10 years is expected for the thinner tunnel oxide (i.e., the 3-nm tunnel oxide)

Dissipative tunneling and orthogonality catastrophe in molecular transistors

DEFF Research Database (Denmark)

Braig, S.; Flensberg, Karsten

2004-01-01

Transport through molecular devices with weak tunnel coupling to the leads but with strong coupling to a single vibrational mode is considered in the case where the vibration is damped by coupling to the environment. In particular, we investigate what influence the electrostatic coupling of the c......Transport through molecular devices with weak tunnel coupling to the leads but with strong coupling to a single vibrational mode is considered in the case where the vibration is damped by coupling to the environment. In particular, we investigate what influence the electrostatic coupling...

Circular polarization in a non-magnetic resonant tunneling device

Directory of Open Access Journals (Sweden)

Airey Robert

2011-01-01

Full Text Available Abstract We have investigated the polarization-resolved photoluminescence (PL in an asymmetric n-type GaAs/AlAs/GaAlAs resonant tunneling diode under magnetic field parallel to the tunnel current. The quantum well (QW PL presents strong circular polarization (values up to -70% at 19 T. The optical emission from GaAs contact layers shows evidence of highly spin-polarized two-dimensional electron and hole gases which affects the spin polarization of carriers in the QW. However, the circular polarization degree in the QW also depends on various other parameters, including the g-factors of the different layers, the density of carriers along the structure, and the Zeeman and Rashba effects.

Electronic-Reconstruction-Enhanced Tunneling Conductance at Terrace Edges of Ultrathin Oxide Films.

Science.gov (United States)

Wang, Lingfei; Kim, Rokyeon; Kim, Yoonkoo; Kim, Choong H; Hwang, Sangwoon; Cho, Myung Rae; Shin, Yeong Jae; Das, Saikat; Kim, Jeong Rae; Kalinin, Sergei V; Kim, Miyoung; Yang, Sang Mo; Noh, Tae Won

2017-11-01

Quantum mechanical tunneling of electrons across ultrathin insulating oxide barriers has been studied extensively for decades due to its great potential in electronic-device applications. In the few-nanometers-thick epitaxial oxide films, atomic-scale structural imperfections, such as the ubiquitously existed one-unit-cell-high terrace edges, can dramatically affect the tunneling probability and device performance. However, the underlying physics has not been investigated adequately. Here, taking ultrathin BaTiO 3 films as a model system, an intrinsic tunneling-conductance enhancement is reported near the terrace edges. Scanning-probe-microscopy results demonstrate the existence of highly conductive regions (tens of nanometers wide) near the terrace edges. First-principles calculations suggest that the terrace-edge geometry can trigger an electronic reconstruction, which reduces the effective tunneling barrier width locally. Furthermore, such tunneling-conductance enhancement can be discovered in other transition metal oxides and controlled by surface-termination engineering. The controllable electronic reconstruction can facilitate the implementation of oxide electronic devices and discovery of exotic low-dimensional quantum phases. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Integrated multiscale modeling of molecular computing devices

International Nuclear Information System (INIS)

Cummings, Peter T; Leng Yongsheng

2005-01-01

Molecular electronics, in which single organic molecules are designed to perform the functions of transistors, diodes, switches and other circuit elements used in current siliconbased microelecronics, is drawing wide interest as a potential replacement technology for conventional silicon-based lithographically etched microelectronic devices. In addition to their nanoscopic scale, the additional advantage of molecular electronics devices compared to silicon-based lithographically etched devices is the promise of being able to produce them cheaply on an industrial scale using wet chemistry methods (i.e., self-assembly from solution). The design of molecular electronics devices, and the processes to make them on an industrial scale, will require a thorough theoretical understanding of the molecular and higher level processes involved. Hence, the development of modeling techniques for molecular electronics devices is a high priority from both a basic science point of view (to understand the experimental studies in this field) and from an applied nanotechnology (manufacturing) point of view. Modeling molecular electronics devices requires computational methods at all length scales - electronic structure methods for calculating electron transport through organic molecules bonded to inorganic surfaces, molecular simulation methods for determining the structure of self-assembled films of organic molecules on inorganic surfaces, mesoscale methods to understand and predict the formation of mesoscale patterns on surfaces (including interconnect architecture), and macroscopic scale methods (including finite element methods) for simulating the behavior of molecular electronic circuit elements in a larger integrated device. Here we describe a large Department of Energy project involving six universities and one national laboratory aimed at developing integrated multiscale methods for modeling molecular electronics devices. The project is funded equally by the Office of Basic

Topography-specific isotropic tunneling in nanoparticle monolayer with sub-nm scale crevices.

Science.gov (United States)

Wang, Guisheng; Jiao, Weihong; Yi, Lizhi; Zhang, Yuejiao; Wu, Ke; Zhang, Chao; Lv, Xianglong; Qian, Lihua; Li, Jianfeng; Yuan, Songliu; Chen, Liang

2016-10-07

Material used in flexible devices may experience anisotropic strain with identical magnitude, outputting coherent signals that tend to have a serious impact on device reliability. In this work, the surface topography of the nanoparticles (NPs) is proposed to be a parameter to control the performance of strain gauge based on tunneling behavior. In contrast to anisotropic tunneling in a monolayer of spherical NPs, electron tunneling in a monolayer of urchin-like NPs actually exhibits a nearly isotropic response to strain with different loading orientations. Isotropic tunneling of the urchin-like NPs is caused by the interlocked pikes of these urchin-like NPs in a random manner during external mechanical stimulus. Topography-dependent isotropic tunneling in two dimensions reported here opens a new opportunity to create highly reliable electronics with superior performance.

David Adler Lectureship Award Talk: III-V Semiconductor Nanowires on Silicon for Future Devices

Science.gov (United States)

Riel, Heike

Bottom-up grown nanowires are very attractive materials for direct integration of III-V semiconductors on silicon thus opening up new possibilities for the design and fabrication of nanoscale devices for electronic, optoelectronic as well as quantum information applications. Template-Assisted Selective Epitaxy (TASE) allows the well-defined and monolithic integration of complex III-V nanostructures and devices on silicon. Achieving atomically abrupt heterointerfaces, high crystal quality and control of dimension down to 1D nanowires enabled the demonstration of FETs and tunnel devices based on In(Ga)As and GaSb. Furthermore, the strong influence of strain on nanowires as well as results on quantum transport studies of InAs nanowires with well-defined geometry will be presented.

Toward an Integrated Optical Data System for Wind Tunnel Testing

National Research Council Canada - National Science Library

Ruyten, Wim

1999-01-01

...) of the test article in a wind tunnel test. The theory for such P&A determinations is developed and applied to data from a recent pressure sensitive paint test in AEDC's 16 ft transonic wind tunnel...

Superconducting tunneling with the tunneling Hamiltonian. II. Subgap harmonic structure

International Nuclear Information System (INIS)

Arnold, G.B.

1987-01-01

The theory of superconducting tunneling without the tunneling Hamiltonian is extended to treat superconductor/insulator/superconductor junctions in which the transmission coefficient of the insulating barrier approaches unity. The solution for the current in such junctions is obtained by solving the problem of a particle hopping in a one-dimensional lattice of sites, with forward and reverse transfer integrals that depend on the site. The results are applied to the problem of subgap harmonic structure in superconducting tunneling. The time-dependent current at finite voltage through a junction exhibiting subgap structure is found to have terms that oscillate at all integer multiples of the Josephson frequency, n(2eV/h). The amplitudes of these new, and as yet unmeasured, ac current contributions as a function of voltage are predicted

Classification of DNA nucleotides with transverse tunneling currents

DEFF Research Database (Denmark)

Pedersen, Jonas Nyvold; Boynton, Paul; Ventra, Massimiliano Di

2017-01-01

, however. In realistic liquid environments, typical currents in tunneling devices are of the order of picoamps. This corresponds to only six electrons per microsecond, and this number affects the integration time required to do current measurements in real experiments. This limits the speed of sequencing......, though current fluctuations due to Brownian motion of the molecule average out during the required integration time. Moreover, data acquisition equipment introduces noise, and electronic filters create correlations in time-series data. We discuss how these effects must be included in the analysis of, e.......g., the assignment of specific nucleobases to current signals. As the signals from different molecules overlap, unambiguous classification is impossible with a single measurement. We argue that the assignment of molecules to a signal is a standard pattern classification problem and calculation of the error rates...

An analytical gate tunneling current model for MOSFETs

Energy Technology Data Exchange (ETDEWEB)

Kazerouni, Iman Abaspur, E-mail: imanabaspur@gmail.com; Hosseini, Seyed Ebrahim [Sabzevar Tarbiat Moallem University, Electrical and Computer Department (Iran, Islamic Republic of)

2012-03-15

Gate tunneling current of MOSFETs is an important factor in modeling ultra small devices. In this paper, gate tunneling in present-generation MOSFETs is studied. In the proposed model, we calculate the electron wave function at the semiconductor-oxide interface and inversion charge by treating the inversion layer as a potential well, including some simplifying assumptions. Then we compute the gate tunneling current using the calculated wave function. The proposed model results have an excellent agreement with experimental results in the literature.

Integrated biocircuits: engineering functional multicellular circuits and devices

Science.gov (United States)

Prox, Jordan; Smith, Tory; Holl, Chad; Chehade, Nick; Guo, Liang

2018-04-01

Objective. Implantable neurotechnologies have revolutionized neuromodulatory medicine for treating the dysfunction of diseased neural circuitry. However, challenges with biocompatibility and lack of full control over neural network communication and function limits the potential to create more stable and robust neuromodulation devices. Thus, we propose a platform technology of implantable and programmable cellular systems, namely Integrated Biocircuits, which use only cells as the functional components of the device. Approach. We envision the foundational principles for this concept begins with novel in vitro platforms used for the study and reconstruction of cellular circuitry. Additionally, recent advancements in organoid and 3D culture systems account for microenvironment factors of cytoarchitecture to construct multicellular circuits as they are normally formed in the brain. We explore the current state of the art of these platforms to provide knowledge of their advancements in circuit fabrication and identify the current biological principles that could be applied in designing integrated biocircuit devices. Main results. We have highlighted the exemplary methodologies and techniques of in vitro circuit fabrication and propose the integration of selected controllable parameters, which would be required in creating suitable biodevices. Significance. We provide our perspective and propose new insights into the future of neuromodulaion devices within the scope of living cellular systems that can be applied in designing more reliable and biocompatible stimulation-based neuroprosthetics.

Integrated circuit devices in control systems of coal mining complexes

Energy Technology Data Exchange (ETDEWEB)

1983-01-01

Systems of automatic monitoring and control of coal mining complexes developed in the 1960's used electromagnetic relays, thyristors, and flip-flops on transistors of varying conductivity. The circuits' designers, devoted much attention to ensuring spark safety, lowering power consumption, and raising noise immunity and repairability of functional devices. The fast development of integrated circuitry led to the use of microelectronic components in most devices of mine automation. An analysis of specifications and experimental research into integrated circuits (IMS) shows that the series K 176 IMS components made by CMOS technology best meet mine conditions of operation. The use of IMS devices under mine conditions has demonstrated their high reliability. Further development of integrated circuitry involve using microprocessors and microcomputers. (SC)

Integrated microfluidic device for single-cell trapping and spectroscopy

KAUST Repository

Liberale, Carlo

2013-02-13

Optofluidic microsystems are key components towards lab-on-a-chip devices for manipulation and analysis of biological specimens. In particular, the integration of optical tweezers (OT) in these devices allows stable sample trapping, while making available mechanical, chemical and spectroscopic analyses.

Integrated microfluidic device for single-cell trapping and spectroscopy

KAUST Repository

Liberale, Carlo; Cojoc, G.; Bragheri, F.; Minzioni, P.; Perozziello, G.; La Rocca, R.; Ferrara, L.; Rajamanickam, V.; Di Fabrizio, Enzo M.; Cristiani, I.

2013-01-01

Optofluidic microsystems are key components towards lab-on-a-chip devices for manipulation and analysis of biological specimens. In particular, the integration of optical tweezers (OT) in these devices allows stable sample trapping, while making available mechanical, chemical and spectroscopic analyses.

Band-to-band tunneling in a carbon nanotube metal-oxide-semiconductor field-effect transistor is dominated by phonon-assisted tunneling.

Science.gov (United States)

Koswatta, Siyuranga O; Lundstrom, Mark S; Nikonov, Dmitri E

2007-05-01

Band-to-band tunneling (BTBT) devices have recently gained a lot of interest due to their potential for reducing power dissipation in integrated circuits. We have performed extensive simulations for the BTBT operation of carbon nanotube metal-oxide-semiconductor field-effect transistors (CNT-MOSFETs) using the nonequilibrium Green's function formalism for both ballistic and dissipative quantum transport. In comparison with recently reported experimental data (J. Am. Chem. Soc. 2006, 128, 3518-3519), we have obtained strong evidence that BTBT in CNT-MOSFETs is dominated by optical phonon assisted inelastic transport, which can have important implications on the transistor characteristics. It is shown that, under large biasing conditions, two-phonon scattering may also become important.

Plated lamination structures for integrated magnetic devices

Science.gov (United States)

Webb, Bucknell C.

2014-06-17

Semiconductor integrated magnetic devices such as inductors, transformers, etc., having laminated magnetic-insulator stack structures are provided, wherein the laminated magnetic-insulator stack structures are formed using electroplating techniques. For example, an integrated laminated magnetic device includes a multilayer stack structure having alternating magnetic and insulating layers formed on a substrate, wherein each magnetic layer in the multilayer stack structure is separated from another magnetic layer in the multilayer stack structure by an insulating layer, and a local shorting structure to electrically connect each magnetic layer in the multilayer stack structure to an underlying magnetic layer in the multilayer stack structure to facilitate electroplating of the magnetic layers using an underlying conductive layer (magnetic or seed layer) in the stack as an electrical cathode/anode for each electroplated magnetic layer in the stack structure.

Automated Boundary Conditions for Wind Tunnel Simulations

Science.gov (United States)

Carlson, Jan-Renee

2018-01-01

Computational fluid dynamic (CFD) simulations of models tested in wind tunnels require a high level of fidelity and accuracy particularly for the purposes of CFD validation efforts. Considerable effort is required to ensure the proper characterization of both the physical geometry of the wind tunnel and recreating the correct flow conditions inside the wind tunnel. The typical trial-and-error effort used for determining the boundary condition values for a particular tunnel configuration are time and computer resource intensive. This paper describes a method for calculating and updating the back pressure boundary condition in wind tunnel simulations by using a proportional-integral-derivative controller. The controller methodology and equations are discussed, and simulations using the controller to set a tunnel Mach number in the NASA Langley 14- by 22-Foot Subsonic Tunnel are demonstrated.

Effect of low and staggered gap quantum wells inserted in GaAs tunnel junctions

Science.gov (United States)

Louarn, K.; Claveau, Y.; Marigo-Lombart, L.; Fontaine, C.; Arnoult, A.; Piquemal, F.; Bounouh, A.; Cavassilas, N.; Almuneau, G.

2018-04-01

In this article, we investigate the impact of the insertion of either a type I InGaAs or a type II InGaAs/GaAsSb quantum well on the performances of MBE-grown GaAs tunnel junctions (TJs). The devices are designed and simulated using a quantum transport model based on the non-equilibrium Green’s function formalism and a 6-band k.p Hamiltonian. We experimentally observe significant improvements of the peak tunneling current density on both heterostructures with a 460-fold increase for a moderately doped GaAs TJ when the InGaAs QW is inserted at the junction interface, and a 3-fold improvement on a highly doped GaAs TJ integrating a type II InGaAs/GaAsSb QW. Thus, the simple insertion of staggered band lineup heterostructures enables us to reach a tunneling current well above the kA cm‑2 range, equivalent to the best achieved results for Si-doped GaAs TJs, implying very interesting potential for TJ-based components, such as multi-junction solar cells, vertical cavity surface emitting lasers and tunnel-field effect transistors.

Fiber coupled ultrafast scanning tunneling microscope

DEFF Research Database (Denmark)

Keil, Ulrich Dieter Felix; Jensen, Jacob Riis; Hvam, Jørn Märcher

1997-01-01

We report on a scanning tunneling microscope with a photoconductive gate in the tunneling current circuit. The tunneling tip is attached to a coplanar transmission line with an integrated photoconductive switch. The switch is illuminated through a fiber which is rigidly attached to the switch...... waveguide. The measurements show that the probe works as a transient voltage detector in contact and a capacitively coupled transient field detector in tunneling mode. We do not measure the transient voltage change in the ohmic tunneling current. In this sense, the spatial resolution for propagating...... substrate. By using a firmly attached fiber we achieve an excellent reproducibility and unconstrained positioning of the tip. We observe a transient signal with 2.9 ps pulse width in tunneling mode and 5 ps in contact mode. The instrument is applied to investigating the mode structure on a coplanar...

76 FR 58041 - Certain Digital Televisions Containing Integrated Circuit Devices and Components Thereof; Notice...

Science.gov (United States)

2011-09-19

... Integrated Circuit Devices and Components Thereof; Notice of Institution of Investigation; Institution of... integrated circuit devices and components thereof by reason of infringement of certain claims of U.S. Patent... after importation of certain digital televisions containing integrated circuit devices and components...

Roll-to-roll embedded conductive structures integrated into organic photovoltaic devices

International Nuclear Information System (INIS)

Van de Wiel, H J; Galagan, Y; Van Lammeren, T J; De Riet, J F J; Gilot, J; Nagelkerke, M G M; Lelieveld, R H C A T; Shanmugam, S; Pagudala, A; Groen, W A; Hui, D

2013-01-01

Highly conductive screen printed metallic (silver) structures (current collecting grids) combined with poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) are a viable replacement for indium tin oxide (ITO) and inkjet printed silver as transparent electrode materials. To provide successful integration into organic photovoltaic (OPV) devices, screen printed silver current collecting grids should be embedded into a substrate to avoid topology issues. In this study micron-thick conductive structures are embedded and integrated into OPV devices. The embedded structures are produced roll-to-roll with optimized process settings and materials. Topology measurements show that the embedded grids are well suited for integration into OPV devices since the surface is almost without spikes and has low surface roughness. JV measurements of OPV devices with embedded structures on a polyethylene terephthalate/silicon nitride (PET/SiN) substrate show an efficiency of 2.15%, which is significantly higher than identical flexible devices with ITO (1.02%) and inkjet printed silver (1.48%). The use of embedded screen printed silver instead of ITO and inkjet printed silver in OPV devices will allow for higher efficiency devices which can be produced with larger design and process freedom. (paper)

Tunneling with dissipation in open quantum systems

International Nuclear Information System (INIS)

Adamyan, G.G.; Antonenko, N.V.; Scheid, W.

1997-01-01

Based on the general form of the master equation for open quantum systems the tunneling is considered. Using the path integral technique a simple closed form expression for the tunneling rate through a parabolic barrier is obtained. The tunneling in the open quantum systems strongly depends on the coupling with environment. We found the cases when the dissipation prohibits tunneling through the barrier but decreases the crossing of the barrier for the energies above the barrier. As a particular application, the case of decay from the metastable state is considered

Resonant TMR inversion in LiF/EuS based spin-filter tunnel junctions

Directory of Open Access Journals (Sweden)

Fen Liu

2016-08-01

Full Text Available Resonant tunneling can lead to inverse tunnel magnetoresistance when impurity levels rather than direct tunneling dominate the transport process. We fabricated hybrid magnetic tunnel junctions of CoFe/LiF/EuS/Ti, with an epitaxial LiF energy barrier joined with a polycrystalline EuS spin-filter barrier. Due to the water solubility of LiF, the devices were fully packaged in situ. The devices showed sizeable positive TMR up to 16% at low bias voltages but clearly inverted TMR at higher bias voltages. The TMR inversion depends sensitively on the thickness of LiF, and the tendency of inversion disappears when LiF gets thick enough and recovers its intrinsic properties.

Investigation into scanning tunnelling luminescence microscopy

International Nuclear Information System (INIS)

Manson-Smith, S.K.

2001-01-01

This work reports on the development of a scanning tunnelling luminescence (STL) microscope and its application to the study of Ill-nitride semiconductor materials used in the production of light emitting devices. STL microscopy is a technique which uses the high resolution topographic imaging capabilities of the scanning tunnelling microscope (STM) to generate high resolution luminescence images. The STM tunnelling current acts as a highly localised source of electrons (or holes) which generates luminescence in certain materials. Light generated at the STM tunnelling junction is collected concurrently with the height variation of the tunnelling probe as it is scanned across a sample surface, producing simultaneous topographic and luminescence images. Due to the very localised excitation source, high resolution luminescence images can be obtained. Spectroscopic resolution can be obtained by using filters. Additionally, the variation of luminescence intensity with tunnel current and with bias voltage can provide information on recombination processes and material properties. The design and construction of a scanning tunnelling luminescence microscope is described in detail. Operating under ambient conditions, the microscope has several novel features, including a new type of miniature inertial slider-based approach motor, large solid-angle light collection optical arrangement and a tip-height regulation system which requires the minimum of operator input. (author)

Effective Passivation and Tunneling Hybrid a-SiOx(In) Layer in ITO/n-Si Heterojunction Photovoltaic Device.

Science.gov (United States)

Gao, Ming; Wan, Yazhou; Li, Yong; Han, Baichao; Song, Wenlei; Xu, Fei; Zhao, Lei; Ma, Zhongquan

2017-05-24

In this article, using controllable magnetron sputtering of indium tin oxide (ITO) materials on single crystal silicon at 100 °C, the optoelectronic heterojunction frame of ITO/a-SiO x (In)/n-Si is simply fabricated for the purpose of realizing passivation contact and hole tunneling. It is found that the gradation profile of indium (In) element together with silicon oxide (SiO x /In) within the ultrathin boundary zone between ITO and n-Si occurs and is characterized by X-ray photoelectron spectroscopy with the ion milling technique. The atomistic morphology and physical phase of the interfacial layer has been observed with a high-resolution transmission electron microscope. X-ray diffraction, Hall effect measurement, and optical transmittance with Tauc plot have been applied to the microstructure and property analyses of ITO thin films, respectively. The polycrystalline and amorphous phases have been verified for ITO films and SiO x (In) hybrid layer, respectively. For the quantum transport, both direct and defect-assisted tunneling of photogenerated holes through the a-SiO x (In) layer is confirmed. Besides, there is a gap state correlative to the indium composition and located at E v + 4.60 eV in the ternary hybrid a-SiO x (In) layer that is predicted by density functional theory of first-principles calculation, which acts as an "extended delocalized state" for direct tunneling of the photogenerated holes. The reasonable built-in potential (V bi = 0.66 V) and optimally controlled ternary hybrid a-SiO x (In) layer (about 1.4 nm) result in that the device exhibits excellent PV performance, with an open-circuit voltage of 0.540 V, a short-circuit current density of 30.5 mA/cm 2 , a high fill factor of 74.2%, and a conversion efficiency of 12.2%, under the AM 1.5 illumination. The work function difference between ITO (5.06 eV) and n-Si (4.31 eV) is determined by ultraviolet photoemission spectroscopy and ascribed to the essence of the built-in-field of the PV device

Scaling Projections on Spin-Transfer Torque Magnetic Tunnel Junctions

Science.gov (United States)

Das, Debasis; Tulapurkar, Ashwin; Muralidharan, Bhaskaran

2018-02-01

We investigate scaling of technologically relevant magnetic tunnel junction devices in the trilayer and pentalayer configurations by varying the cross-sectional area along the transverse direction using the non-equilibrium Green's function spin transport formalism. We study the geometry dependence by considering square and circular cross-sections. As the transverse dimension in each case reduces, we demonstrate that the transverse mode energy profile plays a major role in the resistance-area product. Both types of devices show constant tunnel magnetoresistance at larger cross-sectional areas but achieve ultra-high magnetoresistance at small cross-sectional areas, while maintaining low resistance-area products. We notice that although the critical switching voltage for switching the magnetization of the free layer nanomagnet in the trilayer case remains constant at larger areas, it needs more energy to switch at smaller areas. In the pentalayer case, we observe an oscillatory behavior at smaller areas as a result of double barrier tunneling. We also describe how switching characteristics of both kinds of devices are affected by the scaling.

Thin-film chemical sensors based on electron tunneling

Science.gov (United States)

Khanna, S. K.; Lambe, J.; Leduc, H. G.; Thakoor, A. P.

1985-01-01

The physical mechanisms underlying a novel chemical sensor based on electron tunneling in metal-insulator-metal (MIM) tunnel junctions were studied. Chemical sensors based on electron tunneling were shown to be sensitive to a variety of substances that include iodine, mercury, bismuth, ethylenedibromide, and ethylenedichloride. A sensitivity of 13 parts per billion of iodine dissolved in hexane was demonstrated. The physical mechanisms involved in the chemical sensitivity of these devices were determined to be the chemical alteration of the surface electronic structure of the top metal electrode in the MIM structure. In addition, electroreflectance spectroscopy (ERS) was studied as a complementary surface-sensitive technique. ERS was shown to be sensitive to both iodine and mercury. Electrolyte electroreflectance and solid-state MIM electroreflectance revealed qualitatively the same chemical response. A modified thin-film structure was also studied in which a chemically active layer was introduced at the top Metal-Insulator interface of the MIM devices. Cobalt phthalocyanine was used for the chemically active layer in this study. Devices modified in this way were shown to be sensitive to iodine and nitrogen dioxide. The chemical sensitivity of the modified structure was due to conductance changes in the active layer.

Tunneling in BP-MoS2 heterostructure

Science.gov (United States)

Liu, Xiaochi; Qu, Deshun; Kim, Changsik; Ahmed, Faisal; Yoo, Won Jong

Tunnel field effect transistor (TFET) is considered to be a leading option for achieving SS mV/dec. In this work, black phosphorus (BP) and molybdenum disulfide (MoS2) heterojunction devices are fabricated. We find that thin BP flake and MoS2 form normal p-n junctions, tunneling phenomena can be observed when BP thickness increases to certain level. PEO:CsClO4 is applied on the surface of the device together with a side gate electrode patterned together with source and drain electrodes. The Fermi level of MoS2 on top of BP layer can be modulated by the side gating, and this enables to vary the MoS2-BP tunnel diode property from off-state to on-state. Since tunneling is the working mechanism of MoS2-BP junction, and PEO:CsClO4\\ possesses ultra high dielectric constant and small equivalent oxide thickness (EOT), a low SS of 55 mV/dec is obtained from MoS2-BP TFET. This work was supported by the Global Research Laboratory and Global Frontier R&D Programs at the Center for Hybrid Interface Materials, both funded by the Ministry of Science, ICT & Future Planning via the National Research Foundation of Korea (NRF).

Spin tunnelling in mesoscopic systems

Science.gov (United States)

Garg, Anupam

2001-02-01

We study spin tunnelling in molecular magnets as an instance of a mesoscopic phenomenon, with special emphasis on the molecule Fe8. We show that the tunnel splitting between various pairs of Zeeman levels in this molecule oscillates as a function of applied magnetic field, vanishing completely at special points in the space of magnetic fields, known as diabolical points. This phenomena is explained in terms of two approaches, one based on spin-coherent-state path integrals, and the other on a generalization of the phase integral (or WKB) method to difference equations. Explicit formulas for the diabolical points are obtained for a model Hamiltonian.

Addressing the challenges of using ferromagnetic electrodes in the magnetic tunnel junction-based molecular spintronics devices

International Nuclear Information System (INIS)

Tyagi, Pawan; Friebe, Edward; Baker, Collin

2015-01-01

Addressing the challenges of using high-Curie temperature ferromagnetic (FM) electrodes is critical for molecular spintronics devices (MSDs) research. Two FM electrodes simultaneously chemically bonded with a thiol-functionalized molecule can produce novel MSDs to exploring new quantum mechanical phenomenon and computer technologies. For developing a commercially viable MSD, it is crucial to developing a device fabrication scheme that carefully considers FM electrodes’ susceptibility to oxidation, chemical etching, and stress-induced deformations during fabrication and usage. This paper studies NiFe, an alloy extensively used in present-day memory devices and high-temperature engineering applications, as a candidate FM electrode for the fabrication of MSDs. Our spectroscopic reflectance studies show that NiFe oxidized aggressively after heating beyond ∼90 °C. The NiFe surfaces, aged for several months or heated for several minutes below ∼90 °C, exhibited remarkable electrochemical activity and were found suitable for chemical bonding with the thiol-functionalized molecular device elements. NiFe also demonstrated excellent etching resistance against commonly used solvents and lithography related chemicals. Additionally, NiFe mitigated the adverse effects of mechanical stress by subsiding the stress-induced deformities. A magnetic tunnel junction-based MSD approach was designed by carefully considering the merits and limitations of NiFe. The device fabrication protocol considers the safe temperature limit to avoiding irreversible surface oxidation, the effect of mechanical stresses, surface roughness, and chemical etching. This paper provides foundational experimental insights in realizing a versatile MSD allowing a wide range of transport and magnetic studies

FeGa/MgO/Fe/GaAs(001) magnetic tunnel junction: Growth and magnetic properties

International Nuclear Information System (INIS)

Gobaut, B.; Ciprian, R.; Salles, B.R.; Krizmancic, D.; Rossi, G.; Panaccione, G.; Eddrief, M.; Marangolo, M.; Torelli, P.

2015-01-01

Research on spintronics and on multiferroics leads now to the possibility of combining the properties of these materials in order to develop new functional devices. Here we report the integration of a layer of magnetostrictive material into a magnetic tunnel junction. A FeGa/MgO/Fe heterostructure has been grown on a GaAs(001) substrate by molecular beam epitaxy (MBE) and studied by X-ray magnetic circular dichroism (XMCD). The comparison between magneto optical Kerr effect (MOKE) measurements and hysteresis performed in total electron yield allowed distinguishing the ferromagnetic hysteresis loop of the FeGa top layer from that of the Fe buried layer, evidencing a different switching field of the two layers. This observation indicates an absence of magnetic coupling between the two ferromagnetic layers despite the thickness of the MgO barrier of only 2.5 nm. The in-plane magnetic anisotropy has also been investigated. Overall results show the good quality of the heterostructure and the general feasibility of such a device using magnetostrictive materials in magnetic tunnel junction

Probing the limits of Si:P δ-doped devices patterned by a scanning tunneling microscope in a field-emission mode

Energy Technology Data Exchange (ETDEWEB)

Rudolph, M.; Carr, S. M.; Ten Eyck, G.; Dominguez, J.; Carroll, M. S.; Bussmann, E. [Sandia National Laboratories, Albuquerque, New Mexico 87185 (United States); Subramania, G. [Sandia National Laboratories, Albuquerque, New Mexico 87185 (United States); Department of Electrical and Computer Engineering, University of New Mexico, Albuquerque, New Mexico 87131 (United States); Lilly, M. P. [Sandia National Laboratories, Albuquerque, New Mexico 87185 (United States); Center for Integrated Nanotechnologies, Sandia National Laboratories, Albuquerque, New Mexico 87185 (United States); Pluym, T.

2014-10-20

Recently, a single atom transistor was deterministically fabricated using phosphorus in Si by H-desorption lithography with a scanning tunneling microscope (STM). This milestone in precision, achieved by operating the STM in the conventional tunneling mode, typically utilizes slow (∼10{sup 2} nm{sup 2}/s) patterning speeds. By contrast, using the STM in a high-voltage (>10 V) field-emission mode, patterning speeds can be increased by orders of magnitude to ≳10{sup 4} nm{sup 2}/s. We show that the rapid patterning negligibly affects the functionality of relatively large micron-sized features, which act as contacting pads for these devices. For nanoscale structures, we show that the resulting electrical transport is consistent with the donor incorporation chemistry constraining the electrical dimensions to a scale of 10 nm even though the pattering spot size is 40 nm.

Phase-quantum tunnel device

International Nuclear Information System (INIS)

Sugahara, M.; Ando, N.; Kaneda, H.; Nagai, M.; Ogawa, Y.; Yoshikawa, N.

1985-01-01

Theoretical and Experimental study on granular superconductors shows that they are classified into two groups; fixed-phase superconductor (theta-superconductor) and fixed-pair-number superconductor (N-superconductor) and that a new macroscopic quantum device with conjugate property to Josephson effect can be made by use of N-superconductors

Investigations of quantum effect semiconductor devices: The tunnel switch diode and the velocity modulation transistor

Science.gov (United States)

Daniel, Erik Stephen

In this thesis we present the results of experimental and theoretical studies of two quantum effect devices--the Tunnel Switch Diode (TSD) and the Velocity Modulation Transistor (VMT). We show that TSD devices can be fabricated such that they behave (semi-quantitatively) as predicted by simple analytical models and more advanced drift-diffusion simulations. These devices possess characteristics, such as on-state currents which range over nearly five orders of magnitude, and on/off current ratios which are even larger, which may allow for a practical implementation of a very dense transistorless SRAM architecture and possibly other novel circuit designs. We demonstrate that many TSD properties can be explained by analogy to a thyristor. In particular, we show that the thin oxide layer in the TSD plays a critical role, and that this can be understood in terms of current injection through the oxide, analogous to transport through the "current limiting" layer in a thyristor. As this oxide layer can be subjected to extreme stress during device operation, we have studied the effect of this stress on device behavior. We demonstrate many significant stress-dependent effects, and identify structures and operation modes which minimize these effects. We propose an InAs/GaSb/AlSb VMT which may allow for larger conductance modulation and higher temperature operation than has been demonstrated in similar GaAs/AlAs structures. Fundamental differences in device operation in the two materials systems and unusual transport mechanisms in the InAs/GaSb/AlSb system are identified as a result of the band lineups in the two systems. Boltzmann transport simulations are developed and presented, allowing a qualitative description of the transport in the InAs/GaSb/AlSb structure. Band structure calculations are carried out, allowing for device design. While no working VMT devices were produced, this is believed to be due to processing and crystal growth problems. We present methods used to

Reliability of IP Tunnels in Military Networks

Directory of Open Access Journals (Sweden)

Pólkowski Marcin

2016-10-01

Full Text Available The military networks, contrary to commercial ones, require standards which provide the highest level of security and reliability. The process to assuring redundancy of the main connections through applying various protocols and transmission media causes problem with time needed to re-establish virtual tunnels between different locations in case of damaged link. This article compares reliability of different IP (Internet Protocol tunnels, which were implemented on military network devices.

RFID and Memory Devices Fabricated Integrally on Substrates

Science.gov (United States)

Schramm, Harry F.

2004-01-01

Electronic identification devices containing radio-frequency identification (RFID) circuits and antennas would be fabricated integrally with the objects to be identified, according to a proposal. That is to say, the objects to be identified would serve as substrates for the deposition and patterning of the materials of the devices used to identify them, and each identification device would be bonded to the identified object at the molecular level. Vacuum arc vapor deposition (VAVD) is the NASA derived process for depositing layers of material on the substrate. This proposal stands in contrast to the current practice of fabricating RFID and/or memory devices as wafer-based, self-contained integrated-circuit chips that are subsequently embedded in or attached to plastic cards to make smart account-information cards and identification badges. If one relies on such a chip to store data on the history of an object to be tracked and the chip falls off or out of the object, then one loses both the historical data and the means to track the object and verify its identity electronically. Also, in contrast is the manufacturing philosophy in use today to make many memory devices. Today s methods involve many subtractive processes such as etching. This proposal only uses additive methods, building RFID and memory devices from the substrate up in thin layers. VAVD is capable of spraying silicon, copper, and other materials commonly used in electronic devices. The VAVD process sprays most metals and some ceramics. The material being sprayed has a very strong bond with the substrate, whether that substrate is metal, ceramic, or even wood, rock, glass, PVC, or paper. An object to be tagged with an identification device according to the proposal must be compatible with a vacuum deposition process. Temperature is seldom an issue as the substrate rarely reaches 150 F (66 C) during the deposition process. A portion of the surface of the object would be designated as a substrate for

Tunneling anisotropic magnetoresistance driven by magnetic phase transition.

Science.gov (United States)

Chen, X Z; Feng, J F; Wang, Z C; Zhang, J; Zhong, X Y; Song, C; Jin, L; Zhang, B; Li, F; Jiang, M; Tan, Y Z; Zhou, X J; Shi, G Y; Zhou, X F; Han, X D; Mao, S C; Chen, Y H; Han, X F; Pan, F

2017-09-06

The independent control of two magnetic electrodes and spin-coherent transport in magnetic tunnel junctions are strictly required for tunneling magnetoresistance, while junctions with only one ferromagnetic electrode exhibit tunneling anisotropic magnetoresistance dependent on the anisotropic density of states with no room temperature performance so far. Here, we report an alternative approach to obtaining tunneling anisotropic magnetoresistance in α'-FeRh-based junctions driven by the magnetic phase transition of α'-FeRh and resultantly large variation of the density of states in the vicinity of MgO tunneling barrier, referred to as phase transition tunneling anisotropic magnetoresistance. The junctions with only one α'-FeRh magnetic electrode show a magnetoresistance ratio up to 20% at room temperature. Both the polarity and magnitude of the phase transition tunneling anisotropic magnetoresistance can be modulated by interfacial engineering at the α'-FeRh/MgO interface. Besides the fundamental significance, our finding might add a different dimension to magnetic random access memory and antiferromagnet spintronics.Tunneling anisotropic magnetoresistance is promising for next generation memory devices but limited by the low efficiency and functioning temperature. Here the authors achieved 20% tunneling anisotropic magnetoresistance at room temperature in magnetic tunnel junctions with one α'-FeRh magnetic electrode.

Experimental Investigation on an Energy Efficient Solar Tunnel Dryer

OpenAIRE

M. R. Seshan Ram

2012-01-01

The research determines the effectiveness of the solar tunnel dryer developed and the product dried in the device is superior in quality and also it is compatible with branded products available in the market. The study also determines Acetamide as Phase Key words: Solar Tunnel Dryer, Acetamide as Phase Change Materials, Conversion into Thermal Energy, Thermocouple, and Pyranometer

A Nuclear Microbattery for MEMS Devices

International Nuclear Information System (INIS)

Blanchard, James; Henderson, Douglass; Lal, Amit

2002-01-01

This project was designed to demonstrate the feasibility of producing on-board power for MEMS devices using radioisotopes. MEMS is a fast growing field, with hopes for producing a wide variety of revolutionary applications, including ''labs on a chip,'' micromachined scanning tunneling microscopes, microscopic detectors for biological agents, microsystems for DNA identification, etc. Currently, these applications are limited by the lack of an on-board power source. Research is ongoing to study approaches such as fuel cells, fossil fuels, and chemical batteries, but all these concepts have limitations. For long-lived, high energy density applications, on-board radioisotope power offers the best choice. We have succeeded in producing such devices using a variety of isotopes, incorporation methods, and device geometries. These experiments have demonstrated the feasibility of using radioisotope power and that there are a variety of options available for MEMS designers. As an example of an integrated, self-powered application, we have created an oscillating cantilever beam that is capable of consistent, periodic oscillations over very long time periods without the need for refueling. Ongoing work will demonstrate that this cantilever is capable of radio frequency transmission, allowing MEMS devices to communicate with one another wirelessly. Thus, this will be the first self-powered wireless transmitter available for use in MEMS devices, permitting such applications as sensors embedded in buildings for continuous monitoring of the building performance and integrity

Tunnel magnetoresistance in alumina, magnesia and composite tunnel barrier magnetic tunnel junctions

International Nuclear Information System (INIS)

Schebaum, Oliver; Drewello, Volker; Auge, Alexander; Reiss, Guenter; Muenzenberg, Markus; Schuhmann, Henning; Seibt, Michael; Thomas, Andy

2011-01-01

Using magnetron sputtering, we have prepared Co-Fe-B/tunnel barrier/Co-Fe-B magnetic tunnel junctions with tunnel barriers consisting of alumina, magnesia, and magnesia-alumina bilayer systems. The highest tunnel magnetoresistance ratios we found were 73% for alumina and 323% for magnesia-based tunnel junctions. Additionally, tunnel junctions with a unified layer stack were prepared for the three different barriers. In these systems, the tunnel magnetoresistance ratios at optimum annealing temperatures were found to be 65% for alumina, 173% for magnesia, and 78% for the composite tunnel barriers. The similar tunnel magnetoresistance ratios of the tunnel junctions containing alumina provide evidence that coherent tunneling is suppressed by the alumina layer in the composite tunnel barrier. - Research highlights: → Transport properties of Co-Fe-B/tunnel barrier/Co-Fe-B magnetic tunnel junctions. → Tunnel barrier consists of MgO, Al-Ox, or MgO/Al-Ox bilayer systems. → Limitation of TMR-ratio in composite barrier tunnel junctions to Al-Ox values. → Limitation indicates that Al-Ox layer is causing incoherent tunneling.

IIE`s wind tunnel calibration; Calibracion del tunel de viento del IIE

Energy Technology Data Exchange (ETDEWEB)

Pena Garcia, Raymundo [Instituto de Investigaciones Electricas, Cuernavaca (Mexico)

1986-12-31

The calibration of a wind tunnel is performed in such a way as to warrant a very low turbulence grade. When there is recently built tunnel, as is the case of the IIE`s tunnel, the turbulence in its testing chambers is large; for this reason it is necessary to integrate in it aerodynamic devices and elements capable of reducing it. At the end of the calibration studies can be performed in models with controlled scale. From these and from the results obtained it will be decided if the designed prototypes are built or modified. [Espanol] La calibracion de un tunel de viento se realiza de tal forma que garantiza un grado de turbulencia muy bajo. Cuando se tiene un tunel recien construido, como es el caso del tunel de viento del IIE, la turbulencia en sus camaras de prueba es grande; por lo que es necesario integrarle dispositivos y elementos aerodinamicos que sean capaces de reducirla. Al terminar la calibracion pueden realizarse estudios en modelos con escala controlada. De estos y de los resultados que se obtengan se decidira si se construyen o se modifican los prototipos disenados.

IIE`s wind tunnel calibration; Calibracion del tunel de viento del IIE

Energy Technology Data Exchange (ETDEWEB)

Pena Garcia, Raymundo [Instituto de Investigaciones Electricas, Cuernavaca (Mexico)

1985-12-31

The calibration of a wind tunnel is performed in such a way as to warrant a very low turbulence grade. When there is recently built tunnel, as is the case of the IIE`s tunnel, the turbulence in its testing chambers is large; for this reason it is necessary to integrate in it aerodynamic devices and elements capable of reducing it. At the end of the calibration studies can be performed in models with controlled scale. From these and from the results obtained it will be decided if the designed prototypes are built or modified. [Espanol] La calibracion de un tunel de viento se realiza de tal forma que garantiza un grado de turbulencia muy bajo. Cuando se tiene un tunel recien construido, como es el caso del tunel de viento del IIE, la turbulencia en sus camaras de prueba es grande; por lo que es necesario integrarle dispositivos y elementos aerodinamicos que sean capaces de reducirla. Al terminar la calibracion pueden realizarse estudios en modelos con escala controlada. De estos y de los resultados que se obtengan se decidira si se construyen o se modifican los prototipos disenados.

Medical Device Integration Model Based on the Internet of Things

Science.gov (United States)

Hao, Aiyu; Wang, Ling

2015-01-01

At present, hospitals in our country have basically established the HIS system, which manages registration, treatment, and charge, among many others, of patients. During treatment, patients need to use medical devices repeatedly to acquire all sorts of inspection data. Currently, the output data of the medical devices are often manually input into information system, which is easy to get wrong or easy to cause mismatches between inspection reports and patients. For some small hospitals of which information construction is still relatively weak, the information generated by the devices is still presented in the form of paper reports. When doctors or patients want to have access to the data at a given time again, they can only look at the paper files. Data integration between medical devices has long been a difficult problem for the medical information system, because the data from medical devices are lack of mandatory unified global standards and have outstanding heterogeneity of devices. In order to protect their own interests, manufacturers use special protocols, etc., thus causing medical decices to still be the "lonely island" of hospital information system. Besides, unfocused application of the data will lead to failure to achieve a reasonable distribution of medical resources. With the deepening of IT construction in hospitals, medical information systems will be bound to develop towards mobile applications, intelligent analysis, and interconnection and interworking, on the premise that there is an effective medical device integration (MDI) technology. To this end, this paper presents a MDI model based on the Internet of Things (IoT). Through abstract classification, this model is able to extract the common characteristics of the devices, resolve the heterogeneous differences between them, and employ a unified protocol to integrate data between devices. And by the IoT technology, it realizes interconnection network of devices and conducts associate matching

Quantum Hall Effect: proposed multi-electron tunneling experiment

International Nuclear Information System (INIS)

Kostadinov, I.Z.

1985-11-01

Here we propose a tunneling experiment for the fractional and Integral Quantum Hall Effect. It may demonstrate multi-electron tunneling and may provide information about the nature of the macroscopic quantum states of 2D electronic liquid or solid. (author)

Study of the Integration of the CNU-TS-1 Mobile Tunnel Monitoring System.

Science.gov (United States)

Du, Liming; Zhong, Ruofei; Sun, Haili; Zhu, Qiang; Zhang, Zhen

2018-02-01

A rapid, precise and automated means for the regular inspection and maintenance of a large number of tunnels is needed. Based on the depth study of the tunnel monitoring method, the CNU-TS-1 mobile tunnel monitoring system (TS1) is developed and presented. It can efficiently obtain the cross-sections that are orthogonal to the tunnel in a dynamic way, and the control measurements that depend on design data are eliminated. By using odometers to locate the cross-sections and correcting the data based on longitudinal joints of tunnel segment lining, the cost of the system has been significantly reduced, and the interval between adjacent cross-sections can reach 1-2 cm when pushed to collect data at a normal walking speed. Meanwhile, the relative deformation of tunnel can be analyzed by selecting cross-sections from original data. Through the measurement of the actual tunnel, the applicability of the system for tunnel deformation detection is verified, and the system is shown to be 15 times more efficient than that of the total station. The simulation experiment of the tunnel deformation indicates that the measurement accuracy of TS1 for cross-sections is 1.1 mm. Compared with the traditional method, TS1 improves the efficiency as well as increases the density of the obtained points.

Study of the Integration of the CNU-TS-1 Mobile Tunnel Monitoring System

Directory of Open Access Journals (Sweden)

Liming Du

2018-02-01

Full Text Available A rapid, precise and automated means for the regular inspection and maintenance of a large number of tunnels is needed. Based on the depth study of the tunnel monitoring method, the CNU-TS-1 mobile tunnel monitoring system (TS1 is developed and presented. It can efficiently obtain the cross-sections that are orthogonal to the tunnel in a dynamic way, and the control measurements that depend on design data are eliminated. By using odometers to locate the cross-sections and correcting the data based on longitudinal joints of tunnel segment lining, the cost of the system has been significantly reduced, and the interval between adjacent cross-sections can reach 1–2 cm when pushed to collect data at a normal walking speed. Meanwhile, the relative deformation of tunnel can be analyzed by selecting cross-sections from original data. Through the measurement of the actual tunnel, the applicability of the system for tunnel deformation detection is verified, and the system is shown to be 15 times more efficient than that of the total station. The simulation experiment of the tunnel deformation indicates that the measurement accuracy of TS1 for cross-sections is 1.1 mm. Compared with the traditional method, TS1 improves the efficiency as well as increases the density of the obtained points.

Optical investigation of carrier tunneling in semiconductor nanostructures

Science.gov (United States)

Emiliani, V.; Ceccherini, S.; Bogani, F.; Colocci, M.; Frova, A.; Shi, Song Stone

1997-08-01

The tunneling dynamics of excitons and free carriers in AlxGa1-xAs/GaAs asymmetric double quantum well and near-surface quantum well structures has been investigated by means of time-resolved optical techniques. The competing processes of carrier tunneling out of the quantum well and exciton formation and recombination inside the quantum well have been thoroughly studied in the range of the excitation densities relevant to device applications. A consistent picture capable of fully describing the carrier and exciton-tunneling mechanisms in both types of structures has been obtained and apparently contrasting results in the recent literature are clarified.

Multiferroic tunnel junctions and ferroelectric control of magnetic state at interface (invited)

KAUST Repository

Yin, Y. W.

2015-03-03

As semiconductor devices reach ever smaller dimensions, the challenge of power dissipation and quantum effect place a serious limit on the future device scaling. Recently, a multiferroic tunnel junction (MFTJ) with a ferroelectric barrier sandwiched between two ferromagnetic electrodes has drawn enormous interest due to its potential applications not only in multi-level data storage but also in electric field controlled spintronics and nanoferronics. Here, we present our investigations on four-level resistance states, giant tunneling electroresistance (TER) due to interfacial magnetoelectric coupling, and ferroelectric control of spin polarized tunneling in MFTJs. Coexistence of large tunneling magnetoresistance and TER has been observed in manganite/(Ba, Sr)TiO3/manganite MFTJs at low temperatures and room temperature four-resistance state devices were also obtained. To enhance the TER for potential logic operation with a magnetic memory, La0.7Sr0.3MnO3/BaTiO3/La0.5Ca0.5MnO3 /La0.7Sr0.3MnO3 MFTJs were designed by utilizing a bilayer tunneling barrier in which BaTiO3 is ferroelectric and La0.5Ca0.5MnO3 is close to ferromagnetic metal to antiferromagnetic insulator phase transition. The phase transition occurs when the ferroelectric polarization is reversed, resulting in an increase of TER by two orders of magnitude. Tunneling magnetoresistance can also be controlled by the ferroelectric polarization reversal, indicating strong magnetoelectric coupling at the interface.

Spin and tunneling dynamics in an asymmetrical double quantum dot with spin-orbit coupling: Selective spin transport device

Science.gov (United States)

Singh, Madhav K.; Jha, Pradeep K.; Bhattacherjee, Aranya B.

2017-09-01

In this article, we study the spin and tunneling dynamics as a function of magnetic field in a one-dimensional GaAs double quantum dot with both the Dresselhaus and Rashba spin-orbit coupling. In particular, we consider different spatial widths for the spin-up and spin-down electronic states. We find that the spin dynamics is a superposition of slow as well as fast Rabi oscillations. It is found that the Rashba interaction strength as well as the external magnetic field strongly modifies the slow Rabi oscillations which is particularly useful for implementing solid state selective spin transport device.

FY 1999 Report on research and development project results of industrial science and technology. Research and development of quantum functional devices; 1999 nendo ryoshika kino soshi no kenkyu kaihatsu seika hokokusho

Energy Technology Data Exchange (ETDEWEB)

NONE

2000-03-01

Described herein are the FY 1999 research and development results of quantum functional devices. This project is aimed at establishment of the basic technologies related to quantum functional devices, which utilize various quantum mechanical effects appearing in superfine regions, for development of the microelectronics technologies serving as the bases for superhigh-speed, superhigh-function information processing. The technologies are developed for advancing the elementary devices by quantum functions and development of integrated devices. The results include development, on a trial basis, of the world smallest MOS transistor with a gate length of 10 nm or less and analysis of its behavior, improved characteristics of the tunnel devices, and development, on a trial basis, of a semiconductor memory working based on the principle of single electron capturing/releasing and evaluation thereof. The device-building techniques are developed. The results include demonstration of the logic circuit which controls a small number of electrons, and development of an opto-electronic device on a trial basis, which are the world first results. Progresses are noted in confirmation of behavior of the 3-value basic logic circuit which uses an InGaAs-based tunnel device, demonstration of behavior of the SRAM circuit which uses ME-RHET device, confirmation of possibility of terabit-size memory integration, advancing performance of the quantum MMIC, and designs of the single electron-CMOS integrated circuit. (NEDO)

Tunnel magnetoresistance in double spin filter junctions

International Nuclear Information System (INIS)

Saffarzadeh, Alireza

2003-01-01

We consider a new type of magnetic tunnel junction, which consists of two ferromagnetic tunnel barriers acting as spin filters (SFs), separated by a nonmagnetic metal (NM) layer. Using the transfer matrix method and the free-electron approximation, the dependence of the tunnel magnetoresistance (TMR) on the thickness of the central NM layer, bias voltage and temperature in the double SF junction are studied theoretically. It is shown that the TMR and electron-spin polarization in this structure can reach very large values under suitable conditions. The highest value of the TMR can reach 99%. By an appropriate choice of the thickness of the central NM layer, the degree of spin polarization in this structure will be higher than that of the single SF junctions. These results may be useful in designing future spin-polarized tunnelling devices

AlGaAs/InGaAlP tunnel junctions for multijunction solar cells

Energy Technology Data Exchange (ETDEWEB)

SHARPS,P.R.; LI,N.Y.; HILLS,J.S.; HOU,H.; CHANG,PING-CHIH; BACA,ALBERT G.

2000-05-16

Optimization of GaInP{sub 2}/GaAs dual and GaInP{sub 2}/GaAs/Ge triple junction cells, and development of future generation monolithic multi-junction cells will involve the development of suitable high bandgap tunnel junctions. There are three criteria that a tunnel junction must meet. First, the resistance of the junction must be kept low enough so that the series resistance of the overall device is not increased. For AMO, 1 sun operation, the tunnel junction resistance should be below 5 x 10{sup {minus}2} {Omega}-cm. Secondly, the peak current density for the tunnel junction must also be larger than the J{sub sc} of the cell so that the tunnel junction I-V curve does not have a deleterious effect on the I-V curve of the multi-junction device. Finally, the tunnel junction must be optically transparent, i.e., there must be a minimum of optical absorption of photons that will be collected by the underlying subcells. The paper reports the investigation of four high bandgap tunnel junctions grown by metal-organic chemical vapor deposition.

Medical device integration using mobile telecommunications infrastructure.

Science.gov (United States)

Moorman, Bridget A; Cockle, Richard A

2013-01-01

Financial pressures, an aging population, and a rising number of patients with chronic diseases, have encouraged the use of remote monitoring technologies. This usually entails at least one physiological parameter measurement for a clinician. Mobile telecommunication technologies lend themselves to this functionality, and in some cases, avoid some of the issues encountered with device integration. Moreover, the inherent characteristics of the mobile telecommunications infrastructure allow a coupling of business and clinical functions that were not possible before. Table I compares and contrasts some key aspect of device integration in and out of a healthcare facility. An HTM professional may be part of the team that acquires and/or manages a system using a mobile telecommunications technology. It is important for HTM professionals to ensure the data is in a standard format so that the interfaces across this system don't become brittle and break easily if one part changes. Moreover, the security and safety considerations of the system and the data should be a primary consideration in and y purchase, with attention given to the proper environmental and encryption mechanisms. Clinical engineers and other HTM professionals are unique in that they understand the patient/clinician/device interface and the need to ensure its safety and effectiveness regardless of geographical environment.

Integration of semiconductor and ceramic superconductor devices for microwave applications

NARCIS (Netherlands)

Klopman, B.B.G.; Klopman, B.B.G.; Wijers, H.W.; Gao, J.; Gao, J.; Gerritsma, G.J.; Rogalla, Horst

1991-01-01

Due to the very-low-loss properties of ceramic superconductors, high-performance microwave resonators and filters can be realized. The fact that these devices may be operated at liquid nitrogen temperature facilitates integration with semiconductor devices. Examples are bandpass amplifiers,

The Integration of Bacteriorhodopsin Proteins with Semiconductor Heterostructure Devices

Science.gov (United States)

Xu, Jian

2008-03-01

Bioelectronics has emerged as one of the most rapidly developing fields among the active frontiers of interdisciplinary research. A major thrust in this field is aimed at the coupling of the technologically-unmatched performance of biological systems, such as neural and sensing functions, with the well developed technology of microelectronics and optoelectronics. To this end we have studied the integration of a suitably engineered protein, bacteriorhodopsin (BR), with semiconductor optoelectronic devices and circuits. Successful integration will potentially lead to ultrasensitive sensors with polarization selectivity and built-in preprocessing capabilities that will be useful for high speed tracking, motion and edge detection, biological detection, and artificial vision systems. In this presentation we will summarize our progresses in this area, which include fundamental studies on the transient dynamics of photo-induced charge shift in BR and the coupling mechanism at protein-semiconductor interface for effective immobilizing and selectively integrating light sensitive proteins with microelectronic devices and circuits, and the device engineering of BR-transistor-integrated optical sensors as well as their applications in phototransceiver circuits. Work done in collaboration with Pallab Bhattacharya, Jonghyun Shin, Department of Electrical Engineering and Computer Science, University of Michigan, Ann Arbor, MI; Robert R. Birge, Department of Chemistry, University of Connecticut, Storrs, CT 06269; and György V'ar'o, Institute of Biophysics, Biological Research Center of the Hungarian Academy of Science, H-6701 Szeged, Hungary.

Resonant tunneling measurements of size-induced strain relaxation

Science.gov (United States)

Akyuz, Can Deniz

Lattice mismatch strain available in such semiconductor heterostructures as Si/SiGe or GaAs/AlGaAs can be employed to alter the electronic and optoelectronic properties of semiconductor structures and devices. When deep submicron structures are fabricated from strained material, strained layers relax by sidewall expansion giving rise to size- and geometry-dependent strain gradients throughout the structure. This thesis describes a novel experimental technique to probe the size-induced strain relaxation by studying the tunneling current characteristics of strained p-type Si/SiGe resonant tunneling diodes. Our current-voltage measurements on submicron strained p-Si/SiGe double- and triple-barrier resonant tunneling structures as a function of device diameter, D, provide experimental access to both the average strain relaxation (which leads to relative shifts in the tunneling current peak positions) and strain gradients (which give rise to a fine structure in the current peaks due to inhomogeneous strain-induced lateral quantization). We find that strain relaxation is significant, with a large fraction of the strain energy relaxed on average in D ≤ 0.25 m m devices. Further, the in-plane potentials that arise from inhomogeneous strain gradients are large. In the D ˜ 0.2 m m devices, the corresponding lateral potentials are approximately parabolic exceeding ˜ 25 meV near the perimeter. These potentials create discrete hole states in double-barrier structures (single well), and coupled hole states in triple-barrier structures (two wells). Our results are in excellent agreement with finite-element strain calculations in which the strained layers are permitted to relax to a state of minimum energy by sidewall expansion. Size-induced strain relaxation will undoubtedly become a serious technological issue once strained devices are scaled down to the deep submicron regime. Interestingly, our calculations predict and our measurements are consistent with the appearance of

Investigating Mobile Devices Integration in Higher Education in Cyprus: Faculty Perspectives

Directory of Open Access Journals (Sweden)

Nikleia Eteokleous

2009-01-01

Full Text Available Mobile devices are everywhere and mobile learning has emerged as a potential educational environment; however it is relatively new to Cyprus educational system. The purpose of this research work is to assess and determine the readiness; and evaluate the viability of integrating mobile technology in Cyprus higher education level. To address the above, a mixed method approach is employed making use of quantitative and qualitative data from faculty members working in three private universities in Cyprus. Faculty reactions were mixed with some of them seeing the benefits for mobile learning while others have doubts. The results summarize the technological and pedagogical aspects to be considered prior integrating mobile devices. Additionally, the study supports that one of the major barriers to educators is the lack of understanding regarding mobile devices integration in the teaching and learning process. Finally, there is a need to develop well-defined and well-structured requirements for mobile integration in the classroom.

Medicine Delivery Device with Integrated Sterilization and Detection

Science.gov (United States)

Shearn, Michael J.; Greer, Harold F.; Manohara, Harish

2013-01-01

Sterile delivery devices can be created by integrating a medicine delivery instrument with surfaces that are coated with germicidal and anti-fouling material. This requires that a large-surface-area template be developed within a constrained volume to ensure good contact between the delivered medicine and the germicidal material. Both of these can be integrated using JPL-developed silicon nanotip or cryo-etch black silicon technologies with atomic layer deposition (ALD) coating of specific germicidal layers. The application of semiconductor processing techniques and technologies to the problems of fluid manipulation and delivery has enabled the integration of chemical, electrical, and mechanical manipulation of samples all within a single microfluidic device. This approach has been successfully applied at JPL to the automated processing, detection, and analysis of minute quantities (parts per trillion level) of biomaterials to develop instruments for in situ exploration or extraterrestrial bodies. The same nanofabrication techniques that are used to produce a microfluidics device are also capable of synthesizing extremely high-surface-area templates in precise locations, and coating those surfaces with conformal films to manipulate their surface properties. This methodology has been successfully applied at JPL to produce patterned and coated silicon nanotips (also known as black silicon) to manipulate the hydrophilicity of surfaces to direct the spreading of fluids in microdevices. JPL's ALD technique is an ideal method to produce the highly conformal coatings required for this type of application. Certain materials, such as TiO2, have germicidal and anti-fouling properties when they are illuminated with UV light. The proposed delivery device contacts medicine with this high-surface-area black silicon surface coated with a thin-film germicidal deposited conformally with ALD. The coating can also be illuminated with ultraviolet light for the purpose of sterilization

77 FR 35426 - Certain Radio Frequency Integrated Circuits and Devices Containing Same; Institution of...

Science.gov (United States)

2012-06-13

... of certain radio frequency integrated circuits and devices containing same by reason of infringement... importation of certain radio frequency integrated circuits and devices containing same that infringe one or... INTERNATIONAL TRADE COMMISSION [Investigation No. 337-TA-848] Certain Radio Frequency Integrated...

A manufacturable process integration approach for graphene devices

Science.gov (United States)

Vaziri, Sam; Lupina, Grzegorz; Paussa, Alan; Smith, Anderson D.; Henkel, Christoph; Lippert, Gunther; Dabrowski, Jarek; Mehr, Wolfgang; Östling, Mikael; Lemme, Max C.

2013-06-01

In this work, we propose an integration approach for double gate graphene field effect transistors. The approach includes a number of process steps that are key for future integration of graphene in microelectronics: bottom gates with ultra-thin (2 nm) high-quality thermally grown SiO2 dielectrics, shallow trench isolation between devices and atomic layer deposited Al2O3 top gate dielectrics. The complete process flow is demonstrated with fully functional GFET transistors and can be extended to wafer scale processing. We assess, through simulation, the effects of the quantum capacitance and band bending in the silicon substrate on the effective electric fields in the top and bottom gate oxide. The proposed process technology is suitable for other graphene-based devices such as graphene-based hot electron transistors and photodetectors.

Spin torque switching of 20 nm magnetic tunnel junctions with perpendicular anisotropy

Science.gov (United States)

Gajek, M.; Nowak, J. J.; Sun, J. Z.; Trouilloud, P. L.; O'Sullivan, E. J.; Abraham, D. W.; Gaidis, M. C.; Hu, G.; Brown, S.; Zhu, Y.; Robertazzi, R. P.; Gallagher, W. J.; Worledge, D. C.

2012-03-01

Spin-transfer torque magnetic random access memory (STT-MRAM) is one of the most promising emerging non-volatile memory technologies. MRAM has so far been demonstrated with a unique combination of density, speed, and non-volatility in a single chip, however, without the capability to replace any single mainstream memory. In this paper, we demonstrate the basic physics of spin torque switching in 20 nm diameter magnetic tunnel junctions with perpendicular magnetic anisotropy materials. This deep scaling capability clearly indicates the STT MRAM device itself may be suitable for integration at much higher densities than previously proven.

Resonant tunneling quantum waveguides of variable cross-section, asymptotics, numerics, and applications

CERN Document Server

Baskin, Lev; Plamenevskii, Boris; Sarafanov, Oleg

2015-01-01

This volume studies electron resonant tunneling in two- and three-dimensional quantum waveguides of variable cross-sections in the time-independent approach. Mathematical models are suggested for the resonant tunneling and develop asymptotic and numerical approaches for investigating the models. Also, schemes are presented for several electronics devices based on the phenomenon of resonant tunneling.   Devices based on the phenomenon of electron resonant tunneling are widely used in electronics. Efforts are directed towards refining properties of resonance structures. There are prospects for building new nanosize electronics elements based on quantum dot systems.   However, the role of resonance structure can also be given to a quantum wire of variable cross-section. Instead of an "electrode - quantum dot - electrode" system, one can use a quantum wire with two narrows. A waveguide narrow is an effective potential barrier for longitudinal electron motion along a waveguide. The part of the waveguide between ...

Tunable SnSe2 /WSe2 Heterostructure Tunneling Field Effect Transistor.

Science.gov (United States)

Yan, Xiao; Liu, Chunsen; Li, Chao; Bao, Wenzhong; Ding, Shijin; Zhang, David Wei; Zhou, Peng

2017-09-01

The burgeoning 2D semiconductors can maintain excellent device electrostatics with an ultranarrow channel length and can realize tunneling by electrostatic gating to avoid deprivation of band-edge sharpness resulting from chemical doping, which make them perfect candidates for tunneling field effect transistors. Here this study presents SnSe 2 /WSe 2 van der Waals heterostructures with SnSe 2 as the p-layer and WSe 2 as the n-layer. The energy band alignment changes from a staggered gap band offset (type-II) to a broken gap (type-III) when changing the negative back-gate voltage to positive, resulting in the device operating as a rectifier diode (rectification ratio ~10 4 ) or an n-type tunneling field effect transistor, respectively. A steep average subthreshold swing of 80 mV dec -1 for exceeding two decades of drain current with a minimum of 37 mV dec -1 at room temperature is observed, and an evident trend toward negative differential resistance is also accomplished for the tunneling field effect transistor due to the high gate efficiency of 0.36 for single gate devices. The I ON /I OFF ratio of the transfer characteristics is >10 6 , accompanying a high ON current >10 -5 A. This work presents original phenomena of multilayer 2D van der Waals heterostructures which can be applied to low-power consumption devices. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Evaluation of polymer based third order nonlinear integrated optics devices

NARCIS (Netherlands)

Driessen, A.; Hoekstra, Hugo; Blom, F.C.; Horst, F.; Horst, F.; Krijnen, Gijsbertus J.M.; van Schoot, J.B.P.; van Schoot, J.B.P.; Lambeck, Paul; Popma, T.J.A.; Diemeer, Mart

Nonlinear polymers are promising materials for high speed active integrated optics devices. In this paper we evaluate the perspectives polymer based nonlinear optical devices can offer. Special attention is directed to the materials aspects. In our experimental work we applied mainly Akzo Nobel DANS

Non-equilibrium quasiparticle processes in superconductor tunneling structures

International Nuclear Information System (INIS)

Perold, W.J.

1990-01-01

A broad overview is presented of the phenomenon of superconductivity. The tunneling of quasiparticles in superconducter-insulator structures is described. Related non-equilibrium processes, such as superconductor bandgap suppresion, quasiparticle diffusion and recombination, and excess quasiparticle collection are discussed. The processes are illustrated with numerical computer simulation data. The importance of the inter-relationship between these processes in practical multiple tunneling junction superconducting device structures is also emphasized. 14 refs., 8 figs

The Beginner's Guide to Wind Tunnels with TunnelSim and TunnelSys

Science.gov (United States)

Benson, Thomas J.; Galica, Carol A.; Vila, Anthony J.

2010-01-01

The Beginner's Guide to Wind Tunnels is a Web-based, on-line textbook that explains and demonstrates the history, physics, and mathematics involved with wind tunnels and wind tunnel testing. The Web site contains several interactive computer programs to demonstrate scientific principles. TunnelSim is an interactive, educational computer program that demonstrates basic wind tunnel design and operation. TunnelSim is a Java (Sun Microsystems Inc.) applet that solves the continuity and Bernoulli equations to determine the velocity and pressure throughout a tunnel design. TunnelSys is a group of Java applications that mimic wind tunnel testing techniques. Using TunnelSys, a team of students designs, tests, and post-processes the data for a virtual, low speed, and aircraft wing.

Dynamical tunneling in systems with a mixed phase space

International Nuclear Information System (INIS)

Loeck, Steffen

2010-01-01

Tunneling is one of the most prominent features of quantum mechanics. While the tunneling process in one-dimensional integrable systems is well understood, its quantitative prediction for systems with a mixed phase space is a long-standing open challenge. In such systems regions of regular and chaotic dynamics coexist in phase space, which are classically separated but quantum mechanically coupled by the process of dynamical tunneling. We derive a prediction of dynamical tunneling rates which describe the decay of states localized inside the regular region towards the so-called chaotic sea. This approach uses a fictitious integrable system which mimics the dynamics inside the regular domain and extends it into the chaotic region. Excellent agreement with numerical data is found for kicked systems, billiards, and optical microcavities, if nonlinear resonances are negligible. Semiclassically, however, such nonlinear resonance chains dominate the tunneling process. Hence, we combine our approach with an improved resonance-assisted tunneling theory and derive a unified prediction which is valid from the quantum to the semiclassical regime. We obtain results which show a drastically improved accuracy of several orders of magnitude compared to previous studies. (orig.)

Dynamical tunneling in systems with a mixed phase space

Energy Technology Data Exchange (ETDEWEB)

Loeck, Steffen

2010-04-22

Tunneling is one of the most prominent features of quantum mechanics. While the tunneling process in one-dimensional integrable systems is well understood, its quantitative prediction for systems with a mixed phase space is a long-standing open challenge. In such systems regions of regular and chaotic dynamics coexist in phase space, which are classically separated but quantum mechanically coupled by the process of dynamical tunneling. We derive a prediction of dynamical tunneling rates which describe the decay of states localized inside the regular region towards the so-called chaotic sea. This approach uses a fictitious integrable system which mimics the dynamics inside the regular domain and extends it into the chaotic region. Excellent agreement with numerical data is found for kicked systems, billiards, and optical microcavities, if nonlinear resonances are negligible. Semiclassically, however, such nonlinear resonance chains dominate the tunneling process. Hence, we combine our approach with an improved resonance-assisted tunneling theory and derive a unified prediction which is valid from the quantum to the semiclassical regime. We obtain results which show a drastically improved accuracy of several orders of magnitude compared to previous studies. (orig.)

Vibrational Properties of h-BN and h-BN-Graphene Heterostructures Probed by Inelastic Electron Tunneling Spectroscopy.

Science.gov (United States)

Jung, Suyong; Park, Minkyu; Park, Jaesung; Jeong, Tae-Young; Kim, Ho-Jong; Watanabe, Kenji; Taniguchi, Takashi; Ha, Dong Han; Hwang, Chanyong; Kim, Yong-Sung

2015-11-13

Inelastic electron tunneling spectroscopy is a powerful technique for investigating lattice dynamics of nanoscale systems including graphene and small molecules, but establishing a stable tunnel junction is considered as a major hurdle in expanding the scope of tunneling experiments. Hexagonal boron nitride is a pivotal component in two-dimensional Van der Waals heterostructures as a high-quality insulating material due to its large energy gap and chemical-mechanical stability. Here we present planar graphene/h-BN-heterostructure tunneling devices utilizing thin h-BN as a tunneling insulator. With much improved h-BN-tunneling-junction stability, we are able to probe all possible phonon modes of h-BN and graphite/graphene at Γ and K high symmetry points by inelastic tunneling spectroscopy. Additionally, we observe that low-frequency out-of-plane vibrations of h-BN and graphene lattices are significantly modified at heterostructure interfaces. Equipped with an external back gate, we can also detect high-order coupling phenomena between phonons and plasmons, demonstrating that h-BN-based tunneling device is a wonderful playground for investigating electron-phonon couplings in low-dimensional systems.

Hybrid High-Temperature-Superconductor–Semiconductor Tunnel Diode

Directory of Open Access Journals (Sweden)

Alex Hayat

2012-12-01

Full Text Available We report the demonstration of hybrid high-T_{c}-superconductor–semiconductor tunnel junctions, enabling new interdisciplinary directions in condensed matter research. The devices are fabricated by our newly developed mechanical-bonding technique, resulting in high-T_{c}-superconductor–semiconductor tunnel diodes. Tunneling-spectra characterization of the hybrid junctions of Bi_{2}Sr_{2}CaCu_{2}O_{8+δ} combined with bulk GaAs, or a GaAs/AlGaAs quantum well, exhibits excess voltage and nonlinearity, similarly to spectra obtained in scanning-tunneling microscopy, and is in good agreement with theoretical predictions for a d-wave-superconductor–normal-material junction. Additional junctions are demonstrated using Bi_{2}Sr_{2}CaCu_{2}O_{8+δ} combined with graphite or Bi_{2}Te_{3}. Our results pave the way for new methods in unconventional superconductivity studies, novel materials, and quantum technology applications.

Verification of Fowler–Nordheim electron tunneling mechanism in Ni/SiO{sub 2}/n-4H SiC and n{sup +} poly-Si/SiO{sub 2}/n-4H SiC MOS devices by different models

Energy Technology Data Exchange (ETDEWEB)

Kodigala, Subba Ramaiah, E-mail: kodigala@gmail.com [Department of Electrical Engineering, University of South Carolina, Columbia, SC 29208 (United States); Department of Physics and Astronomy, Department of Electrical and Computer Engineering, California State University, Northridge, CA 91330 (United States)

2016-11-01

This article emphasizes verification of Fowler–Nordheim electron tunneling mechanism in the Ni/SiO{sub 2}/n-4H SiC MOS devices by developing three different kinds of models. The standard semiconductor equations are categorically solved to obtain the change in Fermi energy level of semiconductor with effect of temperature and field that extend support to determine sustainable and accurate tunneling current through the oxide layer. The forward and reverse bias currents with variation of electric field are simulated with help of different models developed by us for MOS devices by applying adequate conditions. The latter is quite different from former in terms of tunneling mechanism in the MOS devices. The variation of barrier height with effect of quantum mechanical, temperature, and fields is considered as effective barrier height for the generation of current–field (J–F) curves under forward and reverse biases but quantum mechanical effect is void in the latter. In addition, the J–F curves are also simulated with variation of carrier concentration in the n-type 4H SiC semiconductor of MOS devices and the relation between them is established.

NIS tunnel junction as an x-ray photon sensor

Science.gov (United States)

Azgui, Fatma; Mears, Carl A.; Labov, Simon E.; Frank, Matthias A.; Sadoulet, Bernard; Brunet, E.; Hiller, Lawrence J.; Lindeman, Mark A.; Netel, Harrie

1995-09-01

This work presents the first results of our development of normal-insulating-superconducting tunnel junctions used as energy dispersive detectors for low energy particles. The device described here is a Ag/Al(subscript 2)O(subscript 3)/Al tunnel junction of area 1.5 multiplied by 10(superscript 4) micrometer squared with thicknesses of 200 nm for the normal Ag strip and 100 nm for the superconducting Al film. Two different high-speed SQUID systems manufactured by quantum magnetics and HYPRES, respectively, were used for the readout of this device. At 80 mK bath temperature we obtained an energy resolution DeltaE(subscript FWHM) equals 250 eV for 5.89 keV x rays absorbed directly in the normal metal. This energy resolution appears to be limited in large part by the observed strong position dependence of the device response.

Device- and service profiles for integrated or systems based on open standards

Directory of Open Access Journals (Sweden)

Mildner Alexander

2015-09-01

Full Text Available Integrated OR systems nowadays are closed and proprietary, so that the interconnection of components from third-party vendors is only possible with high time and cost effort. An integrated operating theatre with open interfaces, giving clinical operators the opportunity to choose individual medical devices from different manufacturers, is currently being developed in the framework of the BMBF (Federal Ministry of Education and Research funded project OR.NET [1]. Actual standards and concepts regarding technical feasibility and accreditation process do not cope with the requirements for modular integration based on an open standard. Therefore, strategies as well as service and device profiles to enable a procedure for risk management and certifiability are in the focus of the project work. Amongst others, a concept for User Interface Profiles (UI-Profiles has been conceived in order to describe medical device functions and the entire user interface regarding Human-Machine-Interaction (HMI characteristics with the aim to identify human-induced risks of central user interfaces. The use of standardized device and service profiles shall allow the manufacturers to integrate their medical devices in the OR.NET network, without disclosing the medical devices’ risk analysis and related confidential knowledge or proprietary information.

The weak π − π interaction originated resonant tunneling and fast switching in the carbon based electronic devices

Directory of Open Access Journals (Sweden)

Jun He

2012-03-01

Full Text Available By means of the nonequilibrium Green's functions and the density functional theory, we have investigated the electronic transport properties of C60 based electronic device with different intermolecular interactions. It is found that the electronic transport properties vary with the types of the interaction between two C60 molecules. A fast electrical switching behavior based on negative differential resistance has been found when two molecules are coupled by the weak π − π interaction. Compared to the solid bonding, the weak interaction is found to induce resonant tunneling, which is responsible for the fast response to the applied electric field and hence the velocity of switching.

Tunnel magnetoresistance of magnetic molecules with spin-vibron coupling

Directory of Open Access Journals (Sweden)

Ahmed Kenawy

2017-05-01

Full Text Available The effect of molecular vibrations on the tunnel magnetoresistance (TMR of a magnetic tunnel junction with a single spin-anisotropic molecule interconnecting its electrodes is investigated theoretically. We demonstrate that if these vibrations couple at the same time to the charge of tunneling electrons and to the spin of the molecule, the spin anisotropy of such a molecule becomes enhanced. This has, in turn, a profound impact on the TMR of such a device showing that molecular vibrations lead to a significant change of spin-polarized transport, differing for the parallel and antiparallel magnetic configuration of the junction.

Phonon tunneling through a double barrier system

International Nuclear Information System (INIS)

Villegas, Diosdado; León-Pérez, Fernando de; Pérez-Álvarez, R.; Arriaga, J.

2015-01-01

The tunneling of optical and acoustic phonons at normal incidence on a double-barrier is studied in this paper. Transmission coefficients and resonance conditions are derived theoretically under the assumption that the long-wavelength approximation is valid. It is shown that the behavior of the transmission coefficients for the symmetric double barrier has a Lorentzian form close to resonant frequencies and that Breit–Wigner's formula have a general validity in one-dimensional phonon tunneling. Authors also study the so-called generalized Hartman effect in the tunneling of long-wavelength phonons and show that this effect is a numerical artifact resulting from taking the opaque limit before exploring the variation with a finite barrier width. This study could be useful for the design of acoustic devices

Phonon tunneling through a double barrier system

Energy Technology Data Exchange (ETDEWEB)

Villegas, Diosdado [Departamento de Física, Universidad Central “Marta Abreu” de Las Villas, CP 54830, Santa Clara, Villa Clara (Cuba); Instituto de Física, Universidad Autónoma de Puebla, 18 Sur y San Claudio, Edif. 110A, Ciudad Universitaria, 72570 Puebla (Mexico); León-Pérez, Fernando de [Centro Universitario de la Defensa de Zaragoza, Ctra. de Huesca s/n, E-50090 Zaragoza (Spain); Pérez-Álvarez, R. [Universidad Autónoma del Estado de Morelos, Av. Universidad 1001, CP 62209 Cuernavaca (Mexico); Arriaga, J., E-mail: arriaga@ifuap.buap.mx [Instituto de Física, Universidad Autónoma de Puebla, 18 Sur y San Claudio, Edif. 110A, Ciudad Universitaria, 72570 Puebla (Mexico)

2015-04-15

The tunneling of optical and acoustic phonons at normal incidence on a double-barrier is studied in this paper. Transmission coefficients and resonance conditions are derived theoretically under the assumption that the long-wavelength approximation is valid. It is shown that the behavior of the transmission coefficients for the symmetric double barrier has a Lorentzian form close to resonant frequencies and that Breit–Wigner's formula have a general validity in one-dimensional phonon tunneling. Authors also study the so-called generalized Hartman effect in the tunneling of long-wavelength phonons and show that this effect is a numerical artifact resulting from taking the opaque limit before exploring the variation with a finite barrier width. This study could be useful for the design of acoustic devices.

Tunable spin-tunnel contacts to silicon using low-work-function ferromagnets

Science.gov (United States)

Min, Byoung-Chul; Motohashi, Kazunari; Lodder, Cock; Jansen, Ron

2006-10-01

Magnetic tunnel junctions have become ubiquitous components appearing in magnetic random-access memory, read heads of magnetic disk drives and semiconductor-based spin devices. Inserting a tunnel barrier has been key to achieving spin injection from ferromagnetic (FM) metals into GaAs, but spin injection into Si has remained elusive. We show that Schottky barrier formation leads to a huge conductivity mismatch of the FM tunnel contact and Si, which cannot be solved by the well-known method of adjusting the tunnel barrier thickness. We present a radically different approach for spin-tunnelling resistance control using low-work-function ferromagnets, inserted at the FM/tunnel barrier interface. We demonstrate that in this way the resistance-area (RA) product of FM/Al2O3/Si contacts can be tuned over eight orders of magnitude, while simultaneously maintaining a reasonable tunnel spin polarization. This raises prospects for Si-based spintronics and presents a new category of ferromagnetic materials for spin-tunnel contacts in low-RA-product applications.

Time-dependent resonant tunnelling for parallel-coupled double quantum dots

International Nuclear Information System (INIS)

Dong Bing; Djuric, Ivana; Cui, H L; Lei, X L

2004-01-01

We derive the quantum rate equations for an Aharonov-Bohm interferometer with two vertically coupled quantum dots embedded in each of two arms by means of the nonequilibrium Green function in the sequential tunnelling regime. Based on these equations, we investigate time-dependent resonant tunnelling under a small amplitude irradiation and find that the resonant photon-assisted tunnelling peaks in photocurrent demonstrate a combination behaviour of Fano and Lorentzian resonances due to the interference effect between the two pathways in this parallel configuration, which is controllable by threading the magnetic flux inside this device

Tunneling in cuprate and bismuthate superconductors

International Nuclear Information System (INIS)

Zasadzinski, J.F.; Huang, Qiang; Tralshawala, N.

1991-10-01

Tunneling measurements using a point-contact technique are reported for the following high temperature superconducting oxides: Ba 1-x K x BiO 3 (BKBO), Nd 2-x Ce x CuO 4 (NCCO), Bi 2 Sr 2 CaCu 2 O 7 (BSCCO) and Tl 2 Ba 2 CaCu 2 O x (TBCCO). For the bismuthate, BKBO, ideal, S-I-N tunneling characteristics are observed using a Au tip. The normalized conductance is fitted to a BCS density of states and thermal smearing only proving there is no fundamental limitation in BKBO for device applications. For the cuprates, the normalized conductance displays BCS-like characteristics, but with a broadening larger than from thermal smearing. Energy gap values are presented for each material. For BKBO and NCCO the Eliashberg functions, α 2 F(ω), obtained from the tunneling are shown to be in good agreement with neutron scattering results. Proximity effect tunneling studies are reported for Au/BSCCO bilayers and show that the energy gap of BSCCO can be observed through Au layers up to 600 Angstrom thick

Tunnel field-effect transistor with two gated intrinsic regions

Directory of Open Access Journals (Sweden)

Y. Zhang

2014-07-01

Full Text Available In this paper, we propose and validate (using simulations a novel design of silicon tunnel field-effect transistor (TFET, based on a reverse-biased p+-p-n-n+ structure. 2D device simulation results show that our devices have significant improvements of switching performance compared with more conventional devices based on p-i-n structure. With independent gate voltages applied to two gated intrinsic regions, band-to-band tunneling (BTBT could take place at the p-n junction, and no abrupt degenerate doping profile is required. We developed single-side-gate (SSG structure and double-side-gate (DSG structure. SSG devices with HfO2 gate dielectric have a point subthreshold swing of 9.58 mV/decade, while DSG devices with polysilicon gate electrode material and HfO2 gate dielectric have a point subthreshold swing of 16.39 mV/decade. These DSG devices have ON-current of 0.255 μA/μm, while that is lower for SSG devices. Having two nano-scale independent gates will be quite challenging to realize with good uniformity across the wafer and the improved behavior of our TFET makes it a promising steep-slope switch candidate for further investigations.

Polarization-engineered GaN/InGaN/GaN tunnel diodes

International Nuclear Information System (INIS)

Krishnamoorthy, Sriram; Nath, Digbijoy N.; Akyol, Fatih; Park, Pil Sung; Esposto, Michele; Rajan, Siddharth

2010-01-01

We report on the design and demonstration of polarization-engineered GaN/InGaN/GaN tunnel junction diodes with high current density and low tunneling turn-on voltage. Wentzel-Kramers-Brillouin calculations were used to model and design tunnel junctions with narrow band gap InGaN-based barrier layers. N-polar p-GaN/In 0.33 Ga 0.67 N/n-GaN heterostructure tunnel diodes were grown using molecular beam epitaxy. Efficient interband tunneling was achieved close to zero bias with a high current density of 118 A/cm 2 at a reverse bias of 1 V, reaching a maximum current density up to 9.2 kA/cm 2 . These results represent the highest current density reported in III-nitride tunnel junctions and demonstrate the potential of III-nitride tunnel devices for a broad range of optoelectronic and electronic applications.

Comparison of costs of integrating working level devices

International Nuclear Information System (INIS)

Langner, G.H. Jr.

1977-01-01

For the purpose of deciding upon the method for making routine field measurements of radon and radon daughter products there are primarily two factors to be taken into consideration: how well the various methods measure the parameter of interest and how much they cost. For the purpose of measuring the annual average working level within a structure there are available basically two devices: the integrating air sampler and track etch film. The cost and manpower requirements for each of these two devices are discussed

Towards Integrating Distributed Energy Resources and Storage Devices in Smart Grid.

Science.gov (United States)

Xu, Guobin; Yu, Wei; Griffith, David; Golmie, Nada; Moulema, Paul

2017-02-01

Internet of Things (IoT) provides a generic infrastructure for different applications to integrate information communication techniques with physical components to achieve automatic data collection, transmission, exchange, and computation. The smart grid, as one of typical applications supported by IoT, denoted as a re-engineering and a modernization of the traditional power grid, aims to provide reliable, secure, and efficient energy transmission and distribution to consumers. How to effectively integrate distributed (renewable) energy resources and storage devices to satisfy the energy service requirements of users, while minimizing the power generation and transmission cost, remains a highly pressing challenge in the smart grid. To address this challenge and assess the effectiveness of integrating distributed energy resources and storage devices, in this paper we develop a theoretical framework to model and analyze three types of power grid systems: the power grid with only bulk energy generators, the power grid with distributed energy resources, and the power grid with both distributed energy resources and storage devices. Based on the metrics of the power cumulative cost and the service reliability to users, we formally model and analyze the impact of integrating distributed energy resources and storage devices in the power grid. We also use the concept of network calculus, which has been traditionally used for carrying out traffic engineering in computer networks, to derive the bounds of both power supply and user demand to achieve a high service reliability to users. Through an extensive performance evaluation, our data shows that integrating distributed energy resources conjointly with energy storage devices can reduce generation costs, smooth the curve of bulk power generation over time, reduce bulk power generation and power distribution losses, and provide a sustainable service reliability to users in the power grid.

InN/InGaN complementary heterojunction-enhanced tunneling field-effect transistor with enhanced subthreshold swing and tunneling current

Science.gov (United States)

Peng, Yue; Han, Genquan; Wang, Hongjuan; Zhang, Chunfu; Liu, Yan; Wang, Yibo; Zhao, Shenglei; Zhang, Jincheng; Hao, Yue

2016-05-01

InN/In0.75Ga0.25N complementary heterojunction-enhanced tunneling field-effect transistors (HE-TFETs) were characterized using the numerical simulation. InN/In0.75Ga0.25N HE-TFET has an InN/In0.75Ga0.25N heterojunction located in the channel region with a distance of LT-H from the source/channel tunneling junction. We demonstrate that, for both n- and p-channel devices, HE-TFETs have a delay of onset voltage VONSET, a steeper subthreshold swing (SS), and an enhanced on-state current ION in comparison with the homo-TFETs. InN/In0.75Ga0.25N n- and p-channel HE-TFETs with a gate length LG of 25 nm and a LT-H of 5 nm achieve a 7 and 9 times ION improvement in comparison with the homo devices, respectively, at a supply voltage of 0.3 V. The performance enhancement in HE-TFETs is attributed to the modulating effect of heterojunction on band-to-band tunneling (BTBT). Because InN/In0.75Ga0.25N heterointerface shows the similar band offsets at conduction and valence bands, the InN/In0.75Ga0.25N heterojunction exhibits the improved effect on BTBT for both n- and p-channel devices. This makes InN/In0.75Ga0.25N heterojunction a promising structure for high performance complementary TFETs.

Single-electron tunneling in double-barrier nanostructures

International Nuclear Information System (INIS)

Goldman, V.J.; Su, B.; Cunningham, J.E.

1992-01-01

In this paper, the authors review experimental study of charge transport in nanometer double-barrier resonant tunneling devices. Heterostructure material is asymmetric: one barrier is substantially less transparent than the other. Resonant tunneling through size-quantized well states and single-electron charging of the well are thus largely separated in the two bias polarities. When the emitter barrier is more transparent than the collector barrier, electrons accumulate in the well; incremental electron occupation of the well is accompanied by Coulomb blockade leading to sharp steps of the tunneling current. When the emitter barrier is less transparent, the current reflects resonant tunneling of just one electron at a time through size-quantized well states; the current peaks and/or steps (depending on experimental parameters) appear in current-voltage characteristics. Magnetic field and temperature effects are also reviewed. Good agreement is achieved in comparison of many features of experimental data with simple theoretical models

A graphene integrated highly transparent resistive switching memory device

Science.gov (United States)

Dugu, Sita; Pavunny, Shojan P.; Limbu, Tej B.; Weiner, Brad R.; Morell, Gerardo; Katiyar, Ram S.

2018-05-01

We demonstrate the hybrid fabrication process of a graphene integrated highly transparent resistive random-access memory (TRRAM) device. The indium tin oxide (ITO)/Al2O3/graphene nonvolatile memory device possesses a high transmittance of >82% in the visible region (370-700 nm) and exhibits stable and non-symmetrical bipolar switching characteristics with considerably low set and reset voltages (ITO/Al2O3/Pt device and studied its switching characteristics for comparison and a better understanding of the ITO/Al2O3/graphene device characteristics. The conduction mechanisms in high and low resistance states were analyzed, and the observed polarity dependent resistive switching is explained based on electro-migration of oxygen ions.

Proximity effect and hot-electron diffusion in Ag/Al2O3/Al tunnel junctions

International Nuclear Information System (INIS)

Netel, H.; Jochum, J.; Labov, S.E.; Mears, C.A.; Frank, M.; Chow, D.; Lindeman, M.A.; Hiller, L.J.

1997-01-01

We have fabricated Ag/Al 2 O 3 /Al tunnel junctions on Si substrates using a new process. This process was developed to fabricate superconducting tunnel junctions (STJs) on the surface of a superconductor. These junctions allow us to study the proximity effect of a superconducting Al film on a normal metal trapping layer. In addition, these devices allow us to measure the hot-electron diffusion constant using a single junction. Lastly these devices will help us optimize the design and fabrication of tunnel junctions on the surface of high-Z, ultra-pure superconducting crystals. 5 refs., 8 figs

Resonant tunneling assisted propagation and amplification of plasmons in high electron mobility transistors

International Nuclear Information System (INIS)

Bhardwaj, Shubhendu; Sensale-Rodriguez, Berardi; Xing, Huili Grace; Rajan, Siddharth; Volakis, John L.

2016-01-01

A rigorous theoretical and computational model is developed for the plasma-wave propagation in high electron mobility transistor structures with electron injection from a resonant tunneling diode at the gate. We discuss the conditions in which low-loss and sustainable plasmon modes can be supported in such structures. The developed analytical model is used to derive the dispersion relation for these plasmon-modes. A non-linear full-wave-hydrodynamic numerical solver is also developed using a finite difference time domain algorithm. The developed analytical solutions are validated via the numerical solution. We also verify previous observations that were based on a simplified transmission line model. It is shown that at high levels of negative differential conductance, plasmon amplification is indeed possible. The proposed rigorous models can enable accurate design and optimization of practical resonant tunnel diode-based plasma-wave devices for terahertz sources, mixers, and detectors, by allowing a precise representation of their coupling when integrated with other electromagnetic structures

Integrated-optic current sensors with a multimode interference waveguide device.

Science.gov (United States)

Kim, Sung-Moon; Chu, Woo-Sung; Kim, Sang-Guk; Oh, Min-Cheol

2016-04-04

Optical current sensors based on polarization-rotated reflection interferometry are demonstrated using polymeric integrated optics and various functional optical waveguide devices. Interferometric sensors normally require bias feedback control for maintaining the operating point, which increases the cost. In order to resolve this constraint of feedback control, a multimode interference (MMI) waveguide device is integrated onto the current-sensor optical chip in this work. From the multiple outputs of the MMI, a 90° phase-shifted transfer function is obtained. Using passive quadrature demodulation, we demonstrate that the sensor could maintain the output signal regardless of the drift in the operating bias-point.

Current-induced magnetization switching in atom-thick tungsten engineered perpendicular magnetic tunnel junctions with large tunnel magnetoresistance.

Science.gov (United States)

Wang, Mengxing; Cai, Wenlong; Cao, Kaihua; Zhou, Jiaqi; Wrona, Jerzy; Peng, Shouzhong; Yang, Huaiwen; Wei, Jiaqi; Kang, Wang; Zhang, Youguang; Langer, Jürgen; Ocker, Berthold; Fert, Albert; Zhao, Weisheng

2018-02-14

Perpendicular magnetic tunnel junctions based on MgO/CoFeB structures are of particular interest for magnetic random-access memories because of their excellent thermal stability, scaling potential, and power dissipation. However, the major challenge of current-induced switching in the nanopillars with both a large tunnel magnetoresistance ratio and a low junction resistance is still to be met. Here, we report spin transfer torque switching in nano-scale perpendicular magnetic tunnel junctions with a magnetoresistance ratio up to 249% and a resistance area product as low as 7.0 Ω µm 2 , which consists of atom-thick W layers and double MgO/CoFeB interfaces. The efficient resonant tunnelling transmission induced by the atom-thick W layers could contribute to the larger magnetoresistance ratio than conventional structures with Ta layers, in addition to the robustness of W layers against high-temperature diffusion during annealing. The critical switching current density could be lower than 3.0 MA cm -2 for devices with a 45-nm radius.

Integrated Photoelectrochemical Solar Energy Conversion and Organic Redox Flow Battery Devices

KAUST Repository

Li, Wenjie; Fu, Hui-chun; Li, Linsen; Cabá n-Acevedo, Miguel; He, Jr-Hau; Jin, Song

2016-01-01

photoelectrochemical solar energy conversion and electrochemical storage device is developed by integrating regenerative silicon solar cells and 9,10-anthraquinone-2,7-disulfonic acid (AQDS)/1,2-benzoquinone-3,5-disulfonic acid (BQDS) RFBs. The device can be directly

Scanning Tunneling Optical Resonance Microscopy

Science.gov (United States)

Bailey, Sheila; Wilt, Dave; Raffaelle, Ryne; Gennett, Tom; Tin, Padetha; Lau, Janice; Castro, Stephanie; Jenkins, Philip; Scheiman, Dave

2003-01-01

Scanning tunneling optical resonance microscopy (STORM) is a method, now undergoing development, for measuring optoelectronic properties of materials and devices on the nanoscale by means of a combination of (1) traditional scanning tunneling microscopy (STM) with (2) tunable laser spectroscopy. In STORM, an STM tip probing a semiconductor is illuminated with modulated light at a wavelength in the visible-to-near-infrared range and the resulting photoenhancement of the tunneling current is measured as a function of the illuminating wavelength. The photoenhancement of tunneling current occurs when the laser photon energy is sufficient to excite charge carriers into the conduction band of the semiconductor. Figure 1 schematically depicts a proposed STORM apparatus. The light for illuminating the semiconductor specimen at the STM would be generated by a ring laser that would be tunable across the wavelength range of interest. The laser beam would be chopped by an achromatic liquid-crystal modulator. A polarization-maintaining optical fiber would couple the light to the tip/sample junction of a commercial STM. An STM can be operated in one of two modes: constant height or constant current. A STORM apparatus would be operated in the constant-current mode, in which the height of the tip relative to the specimen would be varied in order to keep the tunneling current constant. In this mode, a feedback control circuit adjusts the voltage applied to a piezoelectric actuator in the STM that adjusts the height of the STM tip to keep the tunneling current constant. The exponential relationship between the tunneling current and tip-to-sample distance makes it relatively easy to implement this mode of operation. The choice of method by which the photoenhanced portion of the tunneling current would be measured depends on choice of the frequency at which the input illumination would be modulated (chopped). If the frequency of modulation were low enough (typically tunneling current

Light-induced negative differential resistance in graphene/Si-quantum-dot tunneling diodes.

Science.gov (United States)

Lee, Kyeong Won; Jang, Chan Wook; Shin, Dong Hee; Kim, Jong Min; Kang, Soo Seok; Lee, Dae Hun; Kim, Sung; Choi, Suk-Ho; Hwang, Euyheon

2016-07-28

One of the interesing tunneling phenomena is negative differential resistance (NDR), the basic principle of resonant-tunneling diodes. NDR has been utilized in various semiconductor devices such as frequency multipliers, oscillators, relfection amplifiers, logic switches, and memories. The NDR in graphene has been also reported theoretically as well as experimentally, but should be further studied to fully understand its mechanism, useful for practical device applications. Especially, there has been no observation about light-induced NDR (LNDR) in graphene-related structures despite very few reports on the LNDR in GaAs-based heterostructures. Here, we report first observation of LNDR in graphene/Si quantum dots-embedded SiO2 (SQDs:SiO2) multilayers (MLs) tunneling diodes. The LNDR strongly depends on temperature (T) as well as on SQD size, and the T dependence is consistent with photocurrent (PC)-decay behaviors. With increasing light power, the PC-voltage curves are more structured with peak-to-valley ratios over 2 at room temperature. The physical mechanism of the LNDR, governed by resonant tunneling of charge carriers through the minibands formed across the graphene/SQDs:SiO2 MLs and by their nonresonant phonon-assisted tunneling, is discussed based on theoretical considerations.

Tunable negative differential resistance in planar graphene superlattice resonant tunneling diode

Science.gov (United States)

Sattari-Esfahlan, S. M.; Fouladi-Oskuei, J.; Shojaei, S.

2017-04-01

Here, we study the negative differential resistance (NDR) of Dirac electrons in biased planar graphene superlattice (PGSL) and investigate the transport characteristics by adopted transfer matrix method within Landauer-Buttiker formalism. Our model device is based on one-dimensional Kronig-Penney type electrostatic potential in monolayer graphene deposited on a substrate, where the bias voltage is applied by two electrodes in the left and right. At Low bias voltages, we found that NDR appears due to breaking of minibands to Wannier-Stark ladders (WSLs). At the critical bias voltage, delocalization appeared by WS states leads to tunneling peak current in current-voltage (I-V) characteristics. With increasing bias voltage, crossing of rungs from various WSL results in multi-peak NDR. The results demonstrate that the structure parameters like barrier/well thickness and barrier height have remarkable effect on I-V characteristics of PGSL. In addition, Dirac gap enhances peak to valley (PVR) value due to suppressing Klein tunneling. Our results show that the tunable PVR in PGSL resonant tunneling diode can be achievable by structure parameters engineering. NDR at ultra-low bias voltages, such as 100 mV, with giant PVR of 20 is obtained. In our device, the multiple same NDR peaks with ultra-low bias voltage provide promising prospect for multi-valued memories and the low power nanoelectronic tunneling devices.

Assessment of field-induced quantum confinement in heterogate germanium electron–hole bilayer tunnel field-effect transistor

International Nuclear Information System (INIS)

Padilla, J. L.; Alper, C.; Ionescu, A. M.; Gámiz, F.

2014-01-01

The analysis of quantum mechanical confinement in recent germanium electron–hole bilayer tunnel field-effect transistors has been shown to substantially affect the band-to-band tunneling (BTBT) mechanism between electron and hole inversion layers that constitutes the operating principle of these devices. The vertical electric field that appears across the intrinsic semiconductor to give rise to the bilayer configuration makes the formerly continuous conduction and valence bands become a discrete set of energy subbands, therefore increasing the effective bandgap close to the gates and reducing the BTBT probabilities. In this letter, we present a simulation approach that shows how the inclusion of quantum confinement and the subsequent modification of the band profile results in the appearance of lateral tunneling to the underlap regions that greatly degrades the subthreshold swing of these devices. To overcome this drawback imposed by confinement, we propose an heterogate configuration that proves to suppress this parasitic tunneling and enhances the device performance.

Assessment of field-induced quantum confinement in heterogate germanium electron–hole bilayer tunnel field-effect transistor

Energy Technology Data Exchange (ETDEWEB)

Padilla, J. L., E-mail: jose.padilladelatorre@epfl.ch; Alper, C.; Ionescu, A. M. [Nanoelectronic Devices Laboratory, École Polytechnique Fédérale de Lausanne, Lausanne CH-1015 (Switzerland); Gámiz, F. [Departamento de Electrónica y Tecnología de los Computadores, Universidad de Granada, Avda. Fuentenueva s/n, 18071 Granada (Spain)

2014-08-25

The analysis of quantum mechanical confinement in recent germanium electron–hole bilayer tunnel field-effect transistors has been shown to substantially affect the band-to-band tunneling (BTBT) mechanism between electron and hole inversion layers that constitutes the operating principle of these devices. The vertical electric field that appears across the intrinsic semiconductor to give rise to the bilayer configuration makes the formerly continuous conduction and valence bands become a discrete set of energy subbands, therefore increasing the effective bandgap close to the gates and reducing the BTBT probabilities. In this letter, we present a simulation approach that shows how the inclusion of quantum confinement and the subsequent modification of the band profile results in the appearance of lateral tunneling to the underlap regions that greatly degrades the subthreshold swing of these devices. To overcome this drawback imposed by confinement, we propose an heterogate configuration that proves to suppress this parasitic tunneling and enhances the device performance.

Voltage-driven versus current-driven spin torque in anisotropic tunneling junctions

KAUST Repository

Manchon, Aurelien

2011-01-01

Nonequilibrium spin transport in a magnetic tunnel junction comprising a single magnetic layer in the presence of interfacial spin-orbit interaction (SOI) is studied theoretically. The interfacial SOI generates a spin torque of the form T=T∥ M×(z× M)+T⊥ z× M, even in the absence of an external spin polarizer. For thick and large tunnel barriers, the torque reduces to the perpendicular component T⊥, which can be electrically tuned by applying a voltage across the insulator. In the limit of thin and low tunnel barriers, the in-plane torque T∥ emerges, proportional to the tunneling current density. Experimental implications on magnetic devices are discussed. © 2011 IEEE.

Voltage-driven versus current-driven spin torque in anisotropic tunneling junctions

KAUST Repository

Manchon, Aurelien

2011-10-01

Nonequilibrium spin transport in a magnetic tunnel junction comprising a single magnetic layer in the presence of interfacial spin-orbit interaction (SOI) is studied theoretically. The interfacial SOI generates a spin torque of the form T=T∥ M×(z× M)+T⊥ z× M, even in the absence of an external spin polarizer. For thick and large tunnel barriers, the torque reduces to the perpendicular component T⊥, which can be electrically tuned by applying a voltage across the insulator. In the limit of thin and low tunnel barriers, the in-plane torque T∥ emerges, proportional to the tunneling current density. Experimental implications on magnetic devices are discussed. © 2011 IEEE.

Integration of Capacitive Micromachined Ultrasound Transducers to Microfluidic Devices

KAUST Repository

Viržonis, Darius; Kodzius, Rimantas; Vanagas, Galius

2013-01-01

The design and manufacturing flexibility of capacitive micromachined ultrasound transducers (CMUT) makes them attractive option for integration with microfluidic devices both for sensing and fluid manipulation. CMUT concept is introduced here

A new approximation of Fermi-Dirac integrals of order 1/2 for degenerate semiconductor devices

Science.gov (United States)

AlQurashi, Ahmed; Selvakumar, C. R.

2018-06-01

There had been tremendous growth in the field of Integrated circuits (ICs) in the past fifty years. Scaling laws mandated both lateral and vertical dimensions to be reduced and a steady increase in doping densities. Most of the modern semiconductor devices have invariably heavily doped regions where Fermi-Dirac Integrals are required. Several attempts have been devoted to developing analytical approximations for Fermi-Dirac Integrals since numerical computations of Fermi-Dirac Integrals are difficult to use in semiconductor devices, although there are several highly accurate tabulated functions available. Most of these analytical expressions are not sufficiently suitable to be employed in semiconductor device applications due to their poor accuracy, the requirement of complicated calculations, and difficulties in differentiating and integrating. A new approximation has been developed for the Fermi-Dirac integrals of the order 1/2 by using Prony's method and discussed in this paper. The approximation is accurate enough (Mean Absolute Error (MAE) = 0.38%) and easy enough to be used in semiconductor device equations. The new approximation of Fermi-Dirac Integrals is applied to a more generalized Einstein Relation which is an important relation in semiconductor devices.

Experimental Device for Learning of Logical Circuit Design using Integrated Circuits

OpenAIRE

石橋, 孝昭

2012-01-01

This paper presents an experimental device for learning of logical circuit design using integrated circuits and breadboards. The experimental device can be made at a low cost and can be used for many subjects such as logical circuits, computer engineering, basic electricity, electrical circuits and electronic circuits. The proposed device is effective to learn the logical circuits than the usual lecture.

Band-to-band tunneling in Γ valley for Ge source lateral tunnel field effect transistor: Thickness scaling

Science.gov (United States)

Jain, Prateek; Rastogi, Priyank; Yadav, Chandan; Agarwal, Amit; Chauhan, Yogesh Singh

2017-07-01

The direct and indirect valleys in Germanium (Ge) are separated by a very small offset, which opens up the prospect of direct tunneling in the Γ valley of an extended Ge source tunnel field effect transistor (TFET). We explore the impact of thickness scaling of extended Ge source lateral TFET on the band to band tunneling (BTBT) current. The Ge source is extended inside the gate by 2 nm to confine the tunneling in Ge only. We observe that as the thickness is scaled, the band alignment at the Si/Ge heterojunction changes significantly, which results in an increase in Ge to Si BTBT current. Based on density functional calculations, we first obtain the band structure parameters (bandgap, effective masses, etc.) for the Ge and Si slabs of varying thickness, and these are then used to obtain the thickness dependent Kane's BTBT tunneling parameters. We find that electrostatics improves as the thickness is reduced in the ultra-thin Ge film ( ≤ 10 nm). The ON current degrades as we scale down in thickness; however, the subthreshold slope ( S S AVG ) improves remarkably with thickness scaling due to subsurface BTBT. We predict that 8 nm thin devices offer the best option for optimized ON current and S S AVG .

Wearable Fall Detector using Integrated Sensors and Energy Devices

Science.gov (United States)

Jung, Sungmook; Hong, Seungki; Kim, Jaemin; Lee, Sangkyu; Hyeon, Taeghwan; Lee, Minbaek; Kim, Dae-Hyeong

2015-11-01

Wearable devices have attracted great attentions as next-generation electronic devices. For the comfortable, portable, and easy-to-use system platform in wearable electronics, a key requirement is to replace conventional bulky and rigid energy devices into thin and deformable ones accompanying the capability of long-term energy supply. Here, we demonstrate a wearable fall detection system composed of a wristband-type deformable triboelectric generator and lithium ion battery in conjunction with integrated sensors, controllers, and wireless units. A stretchable conductive nylon is used as electrodes of the triboelectric generator and the interconnection between battery cells. Ethoxylated polyethylenimine, coated on the surface of the conductive nylon electrode, tunes the work function of a triboelectric generator and maximizes its performance. The electrical energy harvested from the triboelectric generator through human body motions continuously recharges the stretchable battery and prolongs hours of its use. The integrated energy supply system runs the 3-axis accelerometer and related electronics that record human body motions and send the data wirelessly. Upon the unexpected fall occurring, a custom-made software discriminates the fall signal and an emergency alert is immediately sent to an external mobile device. This wearable fall detection system would provide new opportunities in the mobile electronics and wearable healthcare.

Tunneling between edge states in a quantum spin Hall system.

Science.gov (United States)

Ström, Anders; Johannesson, Henrik

2009-03-06

We analyze a quantum spin Hall device with a point contact connecting two of its edges. The contact supports a net spin tunneling current that can be probed experimentally via a two-terminal resistance measurement. We find that the low-bias tunneling current and the differential conductance exhibit scaling with voltage and temperature that depend nonlinearly on the strength of the electron-electron interaction.

Tunneling magnetoresistance dependence on the temperature in a ferromagnetic Zener diode

Energy Technology Data Exchange (ETDEWEB)

Comesana, E; Aldegunde, M; GarcIa-Loureiro, A, E-mail: enrique.comesana@usc.e [Departamento de Electronica e Computacion, Universidade de Santiago de Compostela, 15782 Santiago de Compostela (Spain)

2009-11-15

In the present work we focus on the study of the temperature dependence of the tunnelling current in a ferromagnetic Zener diode. We predict the tunneling magnetoresistance dependence on the temperature. Large doping concentrations lead to magnetic semiconductors with Curie temperature T{sub C} near or over room temperature and this will facilitate the introduction of new devices that make use of the ferromagnetism effects. According to our calculations the tunneling magnetoresistance has the form TMR {proportional_to} (T{sup n}{sub C}-T{sup n}).

Production of oscillatory flow in wind tunnels

Science.gov (United States)

Al-Asmi, K.; Castro, I. P.

1993-06-01

A method for producing oscillatory flow in open-circuit wind tunnels driven by centrifugal fans is described. Performance characteristics of a new device installed on two such tunnels of greatly differing size are presented. It is shown that sinusoidal variations of the working section flow, having peak-to-peak amplitudes up to at least 30 percent of the mean flow speed and frequencies up to, typically, that corresponding to the acoustic quarter-wave-length frequency determined by the tunnel size, can be obtained with negligible harmonic distortion or acoustic noise difficulties. A brief review of the various methods that have been used previously is included, and the advantages and disadvantages of these different techniques are highlighted. The present technique seems to represent a significant improvement over many of them.

A Monolithic Interconnected module with a tunnel Junction for Enhanced Electrical and Optical Performance

Energy Technology Data Exchange (ETDEWEB)

Murray, Christopher Sean; Wilt, David Morgan

1999-06-30

An improved thermophotovoltaic (TPV) n/p/n device is provided. Monolithic Interconnected Modules (MIMs), semiconductor devices converting infrared radiation to electricity, have been developed with improved electrical and optical performance. The structure is an n-type emitter on a p-type base with an n-type lateral conduction layer. The incorporation of a tunnel junction and the reduction in the amount of p-type material used results in negligible parasitic absorption, decreased series resistance, increased voltage and increased active area. The novel use of a tunnel junction results in the potential for a TPV device with efficiency greater than 24%.

Transit time for resonant tunneling

International Nuclear Information System (INIS)

Garcia Calderon, G.; Rubio, A.

1990-09-01

This work considers properties of the partial widths in one dimensional elastic resonant tunneling in order to propose a transit-time τ tr = (h/2π)/Γ n T res ) where Γ n is the elastic width and T res the transmission coefficient at resonance energy. This time is interpreted as an average over the resonance energy width. It is shown that the tunneling current density integrated across a sharp resonance is inversely proportional to τ tr . This transit time may be much larger than the values predicted by other definitions. (author). 20 refs

Integration of Capacitive Micromachined Ultrasound Transducers to Microfluidic Devices

KAUST Repository

Viržonis, Darius

2013-10-22

The design and manufacturing flexibility of capacitive micromachined ultrasound transducers (CMUT) makes them attractive option for integration with microfluidic devices both for sensing and fluid manipulation. CMUT concept is introduced here by presentin

3D integration of planar crossbar memristive devices with CMOS substrate

International Nuclear Information System (INIS)

Lin, Peng; Pi, Shuang; Xia, Qiangfei

2014-01-01

Planar memristive devices with bottom electrodes embedded into the substrates were integrated on top of CMOS substrates using nanoimprint lithography to implement hybrid circuits with a CMOL-like architecture. The planar geometry eliminated the mechanically and electrically weak parts, such as kinks in the top electrodes in a traditional crossbar structure, and allowed the use of thicker and thus less resistive metal wires as the bottom electrodes. Planar memristive devices integrated with CMOS have demonstrated much lower programing voltages and excellent switching uniformity. With the inclusion of the Moiré pattern, the integration process has sub-20 nm alignment accuracy, opening opportunities for 3D hybrid circuits in applications in the next generation of memory and unconventional computing. (paper)

Integration Head Mounted Display Device and Hand Motion Gesture Device for Virtual Reality Laboratory

Science.gov (United States)

Rengganis, Y. A.; Safrodin, M.; Sukaridhoto, S.

2018-01-01

Virtual Reality Laboratory (VR Lab) is an innovation for conventional learning media which show us whole learning process in laboratory. There are many tools and materials are needed by user for doing practical in it, so user could feel new learning atmosphere by using this innovation. Nowadays, technologies more sophisticated than before. So it would carry in education and it will be more effective, efficient. The Supported technologies are needed us for making VR Lab such as head mounted display device and hand motion gesture device. The integration among them will be used us for making this research. Head mounted display device for viewing 3D environment of virtual reality laboratory. Hand motion gesture device for catching user real hand and it will be visualized in virtual reality laboratory. Virtual Reality will show us, if using the newest technologies in learning process it could make more interesting and easy to understand.

Large room-temperature tunneling anisotropic magnetoresistance and electroresistance in single ferromagnet/Nb:SrTiO3 Schottky devices.

Science.gov (United States)

Kamerbeek, Alexander M; Ruiter, Roald; Banerjee, Tamalika

2018-01-22

There is a large effort in research and development to realize electronic devices capable of storing information in new ways - for instance devices which simultaneously exhibit electro and magnetoresistance. However it remains a challenge to create devices in which both effects coexist. In this work we show that the well-known electroresistance in noble metal-Nb:SrTiO 3 Schottky junctions can be augmented by a magnetoresistance effect in the same junction. This is realized by replacing the noble metal electrode with ferromagnetic Co. This magnetoresistance manifests as a room temperature tunneling anisotropic magnetoresistance (TAMR). The maximum room temperature TAMR (1.6%) is significantly larger and robuster with bias than observed earlier, not using Nb:SrTiO 3 . In a different set of devices, a thin amorphous AlO x interlayer inserted between Co and Nb:SrTiO 3 , reduces the TAMR by more than 2 orders of magnitude. This points to the importance of intimate contact between the Co and Nb:SrTiO 3 for the TAMR effect. This is explained by electric field enhanced spin-orbit coupling of the interfacial Co layer in contact with Nb:SrTiO 3 . We propose that the large TAMR likely has its origin in the 3d orbital derived conduction band and large relative permittivity of Nb:SrTiO 3 and discuss ways to further enhance the TAMR.

Manipulating the voltage dependence of tunneling spin torques

KAUST Repository

Manchon, Aurelien

2012-01-01

Voltage-driven spin transfer torques in magnetic tunnel junctions provide an outstanding tool to design advanced spin-based devices for memory and reprogrammable logic applications. The non-linear voltage dependence of the torque has a direct impact

Synthesis, fabrication and characterization of Ge/Si axial nanowire heterostructure tunnel FETs

Energy Technology Data Exchange (ETDEWEB)

Picraux, Samuel T [Los Alamos National Laboratory; Dayeh, Shadi A [Los Alamos National Laboratory

2010-01-01

Axial Ge/Si heterostructure nanowires allow energy band-edge engineering along the axis of the nanowire, which is the charge transport direction, and the realization of asymmetric devices for novel device architectures. This work reports on two advances in the area of heterostructure nanowires and tunnel FETs: (i) the realization of 100% compositionally modulated Si/Ge axial heterostructure nanowires with lengths suitable for device fabrication and (ii) the design and implementation of Schottky barrier tunnel FETs on these nanowires for high-on currents and suppressed ambipolar behavior. Initial prototype devices resulted in a current drive in excess of 100 {micro}A/{micro}m (I/{pi}D) and 10{sup 5} I{sub on}/I{sub off} ratios. These results demonstrate the potential of such asymmetric heterostructures (both in the semiconductor channel and metal-semiconductor barrier heights) for low-power and high performance electronics.

Integrated devices for quantum information and quantum simulation with polarization encoded qubits

Science.gov (United States)

Sansoni, Linda; Sciarrino, Fabio; Mataloni, Paolo; Crespi, Andrea; Ramponi, Roberta; Osellame, Roberto

2012-06-01

The ability to manipulate quantum states of light by integrated devices may open new perspectives both for fundamental tests of quantum mechanics and for novel technological applications. The technology for handling polarization-encoded qubits, the most commonly adopted approach, was still missing in quantum optical circuits until the ultrafast laser writing (ULW) technique was adopted for the first time to realize integrated devices able to support and manipulate polarization encoded qubits.1 Thanks to this method, polarization dependent and independent devices can be realized. In particular the maintenance of polarization entanglement was demonstrated in a balanced polarization independent integrated beam splitter1 and an integrated CNOT gate for polarization qubits was realized and carachterized.2 We also exploited integrated optics for quantum simulation tasks: by adopting the ULW technique an integrated quantum walk circuit was realized3 and, for the first time, we investigate how the particle statistics, either bosonic or fermionic, influences a two-particle discrete quantum walk. Such experiment has been realized by adopting two-photon entangled states and an array of integrated symmetric directional couplers. The polarization entanglement was exploited to simulate the bunching-antibunching feature of non interacting bosons and fermions. To this scope a novel three-dimensional geometry for the waveguide circuit is introduced, which allows accurate polarization independent behaviour, maintaining a remarkable control on both phase and balancement of the directional couplers.

Axial Ge/Si nanowire heterostructure tunnel FETs.

Energy Technology Data Exchange (ETDEWEB)

Dayeh, Shadi A. (Los Alamos National Laboratory); Gin, Aaron V.; Huang, Jian Yu; Picraux, Samuel Thomas (Los Alamos National Laboratory)

2010-03-01

Axial Ge/Si heterostructure nanowires (NWs) allow energy band-edge engineering along the axis of the NW, which is the charge transport direction, and the realization of asymmetric devices for novel device architectures. This work reports on two significant advances in the area of heterostructure NWs and tunnel FETs: (i) the realization of 100% compositionally modulated Si/Ge axial heterostructure NWs with lengths suitable for device fabrication and (ii) the design and implementation of Schottky barrier tunnel FETs on these NWs for high-on currents and suppressed ambipolar behavior. Initial prototype devices with 10 nm PECVD SiN{sub x} gate dielectric resulted in a very high current drive in excess of 100 {micro}A/{micro}m (I/{pi}D) and 10{sup 5} I{sub on}/I{sub off} ratios. Prior work on the synthesis of Ge/Si axial NW heterostructures through the VLS mechanism have resulted in axial Si/Si{sub 1-x}Ge{sub x} NW heterostructures with x{sub max} {approx} 0.3, and more recently 100% composition modulation was achieved with a solid growth catalyst. In this latter case, the thickness of the heterostructure cannot exceed few atomic layers due to the slow axial growth rate and concurrent radial deposition on the NW sidewalls leading to a mixture of axial and radial deposition, which imposes a big challenge for fabricating useful devices form these NWs in the near future. Here, we report the VLS growth of 100% doping and composition modulated axial Ge/Si heterostructure NWs with lengths appropriate for device fabrication by devising a growth procedure that eliminates Au diffusion on the NW sidewalls and minimizes random kinking in the heterostructure NWs as deduced from detailed microscopy analysis. Fig. 1 a shows a cross-sectional SEM image of epitaxial Ge/Si axial NW heterostructures grown on a Ge(111) surface. The interface abruptness in these Ge/Si heterostructure NWs is of the order of the NW diameter. Some of these NWs develop a crystallographic kink that is {approx

Tunneling magnetoresistance in Si nanowires

KAUST Repository

Montes Muñoz, Enrique

2016-11-09

We investigate the tunneling magnetoresistance of small diameter semiconducting Si nanowires attached to ferromagnetic Fe electrodes, using first principles density functional theory combined with the non-equilibrium Green\\'s functions method for quantum transport. Silicon nanowires represent an interesting platform for spin devices. They are compatible with mature silicon technology and their intrinsic electronic properties can be controlled by modifying the diameter and length. Here we systematically study the spin transport properties for neutral nanowires and both n and p doping conditions. We find a substantial low bias magnetoresistance for the neutral case, which halves for an applied voltage of about 0.35 V and persists up to 1 V. Doping in general decreases the magnetoresistance, as soon as the conductance is no longer dominated by tunneling.

Interband cascade (IC) photovoltaic (PV) architecture for PV devices

Science.gov (United States)

Yang, Rui Q.; Tian, Zhaobing; Mishima, Tetsuya D.; Santos, Michael B.; Johnson, Matthew B.; Klem, John F.

2015-10-20

A photovoltaic (PV) device, comprising a PV interband cascade (IC) stage, wherein the IC PV stage comprises an absorption region with a band gap, the absorption region configured to absorb photons, an intraband transport region configured to act as a hole barrier, and an interband tunneling region configured to act as an electron barrier. An IC PV architecture for a photovoltaic device, the IC PV architecture comprising an absorption region, an intraband transport region coupled to the absorption region, and an interband tunneling region coupled to the intraband transport region and to the adjacent absorption region, wherein the absorption region, the intraband transport region, and the interband tunneling region are positioned such that electrons will flow from the absorption region to the intraband transport region to the interband tunneling region.

Integrating nanosphere lithography in device fabrication

Science.gov (United States)

Laurvick, Tod V.; Coutu, Ronald A.; Lake, Robert A.

2016-03-01

This paper discusses the integration of nanosphere lithography (NSL) with other fabrication techniques, allowing for nano-scaled features to be realized within larger microelectromechanical system (MEMS) based devices. Nanosphere self-patterning methods have been researched for over three decades, but typically not for use as a lithography process. Only recently has progress been made towards integrating many of the best practices from these publications and determining a process that yields large areas of coverage, with repeatability and enabled a process for precise placement of nanospheres relative to other features. Discussed are two of the more common self-patterning methods used in NSL (i.e. spin-coating and dip coating) as well as a more recently conceived variation of dip coating. Recent work has suggested the repeatability of any method depends on a number of variables, so to better understand how these variables affect the process a series of test vessels were developed and fabricated. Commercially available 3-D printing technology was used to incrementally alter the test vessels allowing for each variable to be investigated individually. With these deposition vessels, NSL can now be used in conjunction with other fabrication steps to integrate features otherwise unattainable through current methods, within the overall fabrication process of larger MEMS devices. Patterned regions in 1800 series photoresist with a thickness of ~700nm are used to capture regions of self-assembled nanospheres. These regions are roughly 2-5 microns in width, and are able to control the placement of 500nm polystyrene spheres by controlling where monolayer self-assembly occurs. The resulting combination of photoresist and nanospheres can then be used with traditional deposition or etch methods to utilize these fine scale features in the overall design.

Aerodynamic results of wind tunnel tests on a 0.010-scale model (32-QTS) space shuttle integrated vehicle in the AEDC VKF-40-inch supersonic wind tunnel (IA61)

Science.gov (United States)

Daileda, J. J.

1976-01-01

Plotted and tabulated aerodynamic coefficient data from a wind tunnel test of the integrated space shuttle vehicle are presented. The primary test objective was to determine proximity force and moment data for the orbiter/external tank and solid rocket booster (SRB) with and without separation rockets firing for both single and dual booster runs. Data were obtained at three points (t = 0, 1.25, and 2.0 seconds) on the nominal SRB separation trajectory.

Analysis of Co-Tunneling Current in Fullerene Single-Electron Transistor

Science.gov (United States)

KhademHosseini, Vahideh; Dideban, Daryoosh; Ahmadi, MohammadTaghi; Ismail, Razali

2018-05-01

Single-electron transistors (SETs) are nano devices which can be used in low-power electronic systems. They operate based on coulomb blockade effect. This phenomenon controls single-electron tunneling and it switches the current in SET. On the other hand, co-tunneling process increases leakage current, so it reduces main current and reliability of SET. Due to co-tunneling phenomenon, main characteristics of fullerene SET with multiple islands are modelled in this research. Its performance is compared with silicon SET and consequently, research result reports that fullerene SET has lower leakage current and higher reliability than silicon counterpart. Based on the presented model, lower co-tunneling current is achieved by selection of fullerene as SET island material which leads to smaller value of the leakage current. Moreover, island length and the number of islands can affect on co-tunneling and then they tune the current flow in SET.

Nano devices and circuit techniques for low-energy applications and energy harvesting

CERN Document Server

2016-01-01

This book describes the development of core technologies to address two of the most challenging issues in research for future IT platform development, namely innovative device design and reduction of energy consumption. Three key devices, the FinFET, the TunnelFET, and the electromechanical nanoswitch are described with extensive details of use for practical applications. Energy issues are also covered in a tutorial fashion from material physics, through device technology, to innovative circuit design. The strength of this book lies in its holistic approach dealing with material trends, state-of-the-art of key devices, new examples of circuits and systems applications.    This is the first of three books based on the Integrated Smart Sensors research project, which describe the development of innovative devices, circuits, and system-level enabling technologies.  The aim of the project was to develop common platforms on which various devices and sensors can be loaded, and to create systems offering signific...

Spin accumulation in Si channels using CoFe/MgO/Si and CoFe/AlOx/Si tunnel contacts with high quality tunnel barriers prepared by radical-oxygen annealing

International Nuclear Information System (INIS)

Akushichi, T.; Shuto, Y.; Sugahara, S.; Takamura, Y.

2015-01-01

We investigate spin injection into Si channels using three-terminal spin-accumulation (3T-SA) devices with high-quality CoFe/MgO/n-Si and CoFe/AlO x /n-Si tunnel spin-injectors whose tunnel barriers are formed by radical oxidation of Mg and Al thin films deposited on Si(100) substrates and successive annealing under radical-oxygen exposure. When the MgO and AlO x barriers are not treated by the radical-oxygen annealing, the Hanle-effect signals obtained from the 3T-SA devices are closely fitted by a single Lorentz function representing a signal due to trap spins. On the other hand, when the tunnel barriers are annealed under radical-oxygen exposure, the Hanle-effect signals can be accurately fitted by the superposition of a Lorentz function and a non-Lorentz function representing a signal due to accumulated spins in the Si channel. These results suggest that the quality improvement of tunnel barriers treated by radical-oxygen annealing is highly effective for spin-injection into Si channels

Development and Testing of an Integrated Sandia Cooler Thermoelectric Device (SCTD).

Energy Technology Data Exchange (ETDEWEB)

Johnson, Terry A.; Staats, Wayne Lawrence,; Leick, Michael Thomas; Zimmerman, Mark D.; Radermacher, Reinhard; Martin, Cara; Nasuta, Dennis; Kalinowski, Paul; Hoffman, William

2014-12-01

This report describes a FY14 effort to develop an integrated Sandia Cooler T hermoelectric D evice (SCTD) . The project included a review of feasible thermoelectric (TE) cooling applications, baseline performance testing of an existing TE device, analysis and design development of an integrated SCTD assembly, and performance measurement and validation of the integrated SCTD prototype.

Macroscopic quantum tunneling in a dc SQUID

International Nuclear Information System (INIS)

Chen, Y.C.

1986-01-01

The theory of macroscopic quantum tunneling is applied to a current-biased dc SQUID whose dynamics can be described by a two-dimensional mechanical system with a dissipative environment. Based on the phenomenological model proposed by Caldeira and Leggett, the dissipative environment is represented by a set of harmonic oscillators coupling to the system. After integrating out the environmental degrees of freedom, an effective Euclidean action is found for the two-dimensional system. The action is used to provide the quantum tunneling rate formalism for the dc SQUID. Under certain conditions, the tunneling rate reduces to that of a single current-biased Josephson junction with an adjustable effective critical current

An architecture for integrating planar and 3D cQED devices

Energy Technology Data Exchange (ETDEWEB)

Axline, C.; Reagor, M.; Heeres, R.; Reinhold, P.; Wang, C.; Shain, K.; Pfaff, W.; Chu, Y.; Frunzio, L.; Schoelkopf, R. J. [Department of Applied Physics, Yale University, New Haven, Connecticut 06511 (United States)

2016-07-25

Numerous loss mechanisms can limit coherence and scalability of planar and 3D-based circuit quantum electrodynamics (cQED) devices, particularly due to their packaging. The low loss and natural isolation of 3D enclosures make them good candidates for coherent scaling. We introduce a coaxial transmission line device architecture with coherence similar to traditional 3D cQED systems. Measurements demonstrate well-controlled external and on-chip couplings, a spectrum absent of cross-talk or spurious modes, and excellent resonator and qubit lifetimes. We integrate a resonator-qubit system in this architecture with a seamless 3D cavity, and separately pattern a qubit, readout resonator, Purcell filter, and high-Q stripline resonator on a single chip. Device coherence and its ease of integration make this a promising tool for complex experiments.

Atomic scale investigations of the gate controlled tunneling effect in graphyne nanoribbon

International Nuclear Information System (INIS)

Yang, Wen; Wang, Lu-Hao; Geng, Yang; Sun, Qing-Qing; Zhou, Peng; Ding, Shi-Jing; Wei Zhang, David

2013-01-01

Configuration and transport properties of zigzag graphyne nanoribbon (n = 2) are investigated by means of the first-principles calculations and non-equilibrium Green's function in this work. We demonstrated the controllability of the graphyne's conductivity by gate bias, and the tunneling behavior induced by gate and drain voltages was investigated systemically. The characteristics of I d -V d , I d -V g , as well as the evolutions of current with electron temperature elevation were explored. The device exhibits a tunneling ratio around 10 3 , and the state art of tunneling operations of the tunneling field effect transistor in this split-new material was achieved

Tunneling technologies for the collider ring tunnels

International Nuclear Information System (INIS)

Frobenius, P.

1989-01-01

The Texas site chosen for the Superconducting Super Collider has been studied, and it has been determined that proven, conventional technology and accepted engineering practice are suitable for constructing the collider tunnels. The Texas National Research Laboratory Commission report recommended that two types of tunneling machines be used for construction of the tunnels: a conventional hard rock tunnel boring machine (TBM) for the Austin chalk and a double shielded, rotary TBM for the Taylor marl. Since the tunneling machines usually set the pace for the project, efficient planning, operation, and coordination of the tunneling system components will be critical to the schedule and cost of the project. During design, tunneling rate prediction should be refined by focusing on the development of an effective tunneling system and evaluating its capacity to meet or exceed the required schedules. 8 refs., 13 figs

Intermediate-band photosensitive device with quantum dots having tunneling barrier embedded in organic matrix

Science.gov (United States)

Forrest, Stephen R.

2008-08-19

A plurality of quantum dots each have a shell. The quantum dots are embedded in an organic matrix. At least the quantum dots and the organic matrix are photoconductive semiconductors. The shell of each quantum dot is arranged as a tunneling barrier to require a charge carrier (an electron or a hole) at a base of the tunneling barrier in the organic matrix to perform quantum mechanical tunneling to reach the respective quantum dot. A first quantum state in each quantum dot is between a lowest unoccupied molecular orbital (LUMO) and a highest occupied molecular orbital (HOMO) of the organic matrix. Wave functions of the first quantum state of the plurality of quantum dots may overlap to form an intermediate band.

A study of inelastic electron-phonon interactions on tunneling magnetoresistance of a nano-scale device

International Nuclear Information System (INIS)

Modarresi, M.; Roknabadi, M.R.; Shahtahmasbi, N.; Vahedi Fakhrabad, D.; Arabshahi, H.

2011-01-01

In this research, we have studied the effect of inelastic electron-phonon interactions on current-voltage characteristic and tunneling magnetoresistance of a polythiophene molecule that is sandwiched between two cobalt electrodes using modified Green's function method as proposed by Walczak. The molecule is described with a modified Su-Schrieffer-Heeger Hamiltonian. The ground state of the molecule is obtained by Hellman-Feynman theorem. Electrodes are described in the wide-band approximation and spin-flip is neglected during conduction. Our calculation results show that with increase in voltage the currents increase and tunneling magnetoresistance decreases. Change in tunneling magnetoresistance due to inelastic interactions is limited in a small bias voltage interval and can be neglected in the other bias voltages. -- Research Highlights: →We investigate the effect of inelastic interaction on transport properties. →Due to inelastic interactions tunneling magnetoresistance decreases. →Decrease in TMR is restricted in a small voltage interval.

A Sensor Middleware for integration of heterogeneous medical devices.

Science.gov (United States)

Brito, M; Vale, L; Carvalho, P; Henriques, J

2010-01-01

In this paper, the architecture of a modular, service-oriented, Sensor Middleware for data acquisition and processing is presented. The described solution was developed with the purpose of solving two increasingly relevant problems in the context of modern pHealth systems: i) to aggregate a number of heterogeneous, off-the-shelf, devices from which clinical measurements can be acquired and ii) to provide access and integration with an 802.15.4 network of wearable sensors. The modular nature of the Middleware provides the means to easily integrate pre-processing algorithms into processing pipelines, as well as new drivers for adding support for new sensor devices or communication technologies. Tests performed with both real and artificially generated data streams show that the presented solution is suitable for use both in a Windows PC or a Windows Mobile PDA with minimal overhead.

Development of a process control computer device for the adaptation of flexible wind tunnel walls

Science.gov (United States)

Barg, J.

1982-01-01

In wind tunnel tests, the problems arise of determining the wall pressure distribution, calculating the wall contour, and controlling adjustment of the walls. This report shows how these problems have been solved for the high speed wind tunnel of the Technical University of Berlin.

Simulation of hydrogen releases from fuel-cell vehicles in tunnels

Energy Technology Data Exchange (ETDEWEB)

Houf, William G.; Evans, Greg H.; James, Scott C. [Sandia National Labs., Livermore, CA (United States); Merilo, Erik; Groethe, Mark [SRI International, Menlo Park, CA (United States)

2010-07-01

Simulation results for a hydrogen fuel-cell vehicle in a full-scale tunnel have been performed for the case where hydrogen gas is vented from the vehicle as a result of thermal activation of the pressure relief device (PRD). The same modeling approach used in the full-scale tunnel modeling was validated in a scaled model by comparing simulated results with measured results from a series of scaled-tunnel test experiments performed at the SRI Corral Hollow test facility. Results of the simulations were found to be in good agreement with the experimental data. Finally, a rudimentary risk analysis indicated that the level of potential risk from hydrogen vehicles accidents involving thermally activated PRDs in tunnels does not appear to significantly increase the current level of individual risk to the public from everyday life. (orig.)

GaAs integrated circuits and heterojunction devices

Science.gov (United States)

Fowlis, Colin

1986-06-01

The state of the art of GaAs technology in the U.S. as it applies to digital and analog integrated circuits is examined. In a market projection, it is noted that whereas analog ICs now largely dominate the market, in 1994 they will amount to only 39 percent vs. 57 percent for digital ICs. The military segment of the market will remain the largest (42 percent in 1994 vs. 70 percent today). ICs using depletion-mode-only FETs can be constructed in various forms, the closest to production being BFL or buffered FET logic. Schottky diode FET logic - a lower power approach - can reach higher complexities and strong efforts are being made in this direction. Enhancement type devices appear essential to reach LSI and VLSI complexity, but process control is still very difficult; strong efforts are under way, both in the U.S. and in Japan. Heterojunction devices appear very promising, although structures are fairly complex, and special fabrication techniques, such as molecular beam epitaxy and MOCVD, are necessary. High-electron-mobility-transistor (HEMT) devices show significant performance advantages over MESFETs at low temperatures. Initial results of heterojunction bipolar transistor devices show promise for high speed A/D converter applications.

Integration of active devices on smart polymers for neural interfaces

Science.gov (United States)

Avendano-Bolivar, Adrian Emmanuel

The increasing ability to ever more precisely identify and measure neural interactions and other phenomena in the central and peripheral nervous systems is revolutionizing our understanding of the human body and brain. To facilitate further understanding, more sophisticated neural devices, perhaps using microelectronics processing, must be fabricated. Materials often used in these neural interfaces, while compatible with these fabrication processes, are not optimized for long-term use in the body and are often orders of magnitude stiffer than the tissue with which they interact. Using the smart polymer substrates described in this work, suitability for processing as well as chronic implantation is demonstrated. We explore how to integrate reliable circuitry onto these flexible, biocompatible substrates that can withstand the aggressive environment of the body. To increase the capabilities of these devices beyond individual channel sensing and stimulation, active electronics must also be included onto our systems. In order to add this functionality to these substrates and explore the limits of these devices, we developed a process to fabricate single organic thin film transistors with mobilities up to 0.4 cm2/Vs and threshold voltages close to 0V. A process for fabricating organic light emitting diodes on flexible substrates is also addressed. We have set a foundation and demonstrated initial feasibility for integrating multiple transistors onto thin-film flexible devices to create new applications, such as matrix addressable functionalized electrodes and organic light emitting diodes. A brief description on how to integrate waveguides for their use in optogenetics is addressed. We have built understanding about device constraints on mechanical, electrical and in vivo reliability and how various conditions affect the electronics' lifetime. We use a bi-layer gate dielectric using an inorganic material such as HfO 2 combined with organic Parylene-c. A study of

Sub-10 nm colloidal lithography for circuit-integrated spin-photo-electronic devices

Directory of Open Access Journals (Sweden)

Adrian Iovan

2012-12-01

Full Text Available Patterning of materials at sub-10 nm dimensions is at the forefront of nanotechnology and employs techniques of various complexity, efficiency, areal scale, and cost. Colloid-based patterning is known to be capable of producing individual sub-10 nm objects. However, ordered, large-area nano-arrays, fully integrated into photonic or electronic devices have remained a challenging task. In this work, we extend the practice of colloidal lithography to producing large-area sub-10 nm point-contact arrays and demonstrate their circuit integration into spin-photo-electronic devices. The reported nanofabrication method should have broad application areas in nanotechnology as it allows ballistic-injection devices, even for metallic materials with relatively short characteristic relaxation lengths.

Theory of tunneling in metal--superconductor devices: Supercurrents in the superconductor gap at zero temperature

International Nuclear Information System (INIS)

Garcia, N.; Flores, F.; Guinea, F.

1988-01-01

Tunneling experiments in metal-oxide superconductor have shown the existence of ''leakage'' currents for applied voltages V smaller than one-half of the superconductor gap Δ. These currents are independent of temperature T. Recently experiments with scanning tunneling microscopy (STM) and squeezable tunnel junctions have shown that the observation of the superconductor gap depends strongly on the resistance in the junction. In fact only for resistances larger than ∼10 6 Ω the gap is clearly observable. These experiments have been explained in terms of the perturbative Hamiltonian formalism of Bardeen. However, it may happen that this theory while applicable for very large resistances may not be so for small tunnel resistances. We present here a nonperturbative theory in all orders of the transmitivity chemical bondTochemical bond 2 and show the existence of supercurrents for values of V 2 . We believe that experiments in STM and other junctions should be interpreted in the frame of this theory

Chiral tunneling in gated inversion symmetric Weyl semimetal

Science.gov (United States)

Bai, Chunxu; Yang, Yanling; Chang, Kai

2016-01-01

Based on the chirality-resolved transfer-matrix method, we evaluate the chiral transport tunneling through Weyl semimetal multi-barrier structures created by periodic gates. It is shown that, in sharp contrast to the cases of three dimensional normal semimetals, the tunneling coefficient as a function of incident angle shows a strong anisotropic behavior. Importantly, the tunneling coefficients display an interesting periodic oscillation as a function of the crystallographic angle of the structures. With the increasement of the barriers, the tunneling current shows a Fabry-Perot type interferences. For superlattice structures, the fancy miniband effect has been revealed. Our results show that the angular dependence of the first bandgap can be reduced into a Lorentz formula. The disorder suppresses the oscillation of the tunneling conductance, but would not affect its average amplitude. This is in sharp contrast to that in multi-barrier conventional semiconductor structures. Moreover, numerical results for the dependence of the angularly averaged conductance on the incident energy and the structure parameters are presented and contrasted with those in two dimensional relativistic materials. Our work suggests that the gated Weyl semimetal opens a possible new route to access to new type nanoelectronic device. PMID:26888491

Integrated neuron circuit for implementing neuromorphic system with synaptic device

Science.gov (United States)

Lee, Jeong-Jun; Park, Jungjin; Kwon, Min-Woo; Hwang, Sungmin; Kim, Hyungjin; Park, Byung-Gook

2018-02-01

In this paper, we propose and fabricate Integrate & Fire neuron circuit for implementing neuromorphic system. Overall operation of the circuit is verified by measuring discrete devices and the output characteristics of the circuit. Since the neuron circuit shows asymmetric output characteristic that can drive synaptic device with Spike-Timing-Dependent-Plasticity (STDP) characteristic, the autonomous weight update process is also verified by connecting the synaptic device and the neuron circuit. The timing difference of the pre-neuron and the post-neuron induce autonomous weight change of the synaptic device. Unlike 2-terminal devices, which is frequently used to implement neuromorphic system, proposed scheme of the system enables autonomous weight update and simple configuration by using 4-terminal synapse device and appropriate neuron circuit. Weight update process in the multi-layer neuron-synapse connection ensures implementation of the hardware-based artificial intelligence, based on Spiking-Neural- Network (SNN).

Integrated Photoelectrochemical Solar Energy Conversion and Organic Redox Flow Battery Devices

KAUST Repository

Li, Wenjie

2016-09-21

Building on regenerative photoelectrochemical solar cells and emerging electrochemical redox flow batteries (RFBs), more efficient, scalable, compact, and cost-effective hybrid energy conversion and storage devices could be realized. An integrated photoelectrochemical solar energy conversion and electrochemical storage device is developed by integrating regenerative silicon solar cells and 9,10-anthraquinone-2,7-disulfonic acid (AQDS)/1,2-benzoquinone-3,5-disulfonic acid (BQDS) RFBs. The device can be directly charged by solar light without external bias, and discharged like normal RFBs with an energy storage density of 1.15 Wh L−1 and a solar-to-output electricity efficiency (SOEE) of 1.7 % over many cycles. The concept exploits a previously undeveloped design connecting two major energy technologies and promises a general approach for storing solar energy electrochemically with high theoretical storage capacity and efficiency.

Evaluating and Predicting Patient Safety for Medical Devices With Integral Information Technology

Science.gov (United States)

2005-01-01

323 Evaluating and Predicting Patient Safety for Medical Devices with Integral Information Technology Jiajie Zhang, Vimla L. Patel, Todd R...errors are due to inappropriate designs for user interactions, rather than mechanical failures. Evaluating and predicting patient safety in medical ...the users on the identified trouble spots in the devices. We developed two methods for evaluating and predicting patient safety in medical devices

Framework for the Integration of Mobile Device Features in PLM

OpenAIRE

Hopf, Jens Michael

2016-01-01

Currently, companies have covered their business processes with stationary workstations while mobile business applications have limited relevance. Companies can cover their overall business processes more time-efficiently and cost-effectively when they integrate mobile users in workflows using mobile device features. The objective is a framework that can be used to model and control business applications for PLM processes using mobile device features to allow a totally new user experience.

Heterogenous integration of a thin-film GaAs photodetector and a microfluidic device on a silicon substrate

International Nuclear Information System (INIS)

Song, Fuchuan; Xiao, Jing; Udawala, Fidaali; Seo, Sang-Woo

2011-01-01

In this paper, heterogeneous integration of a III–V semiconductor thin-film photodetector (PD) with a microfluidic device is demonstrated on a SiO 2 –Si substrate. Thin-film format of optical devices provides an intimate integration of optical functions with microfluidic devices. As a demonstration of a multi-material and functional system, the biphasic flow structure in the polymeric microfluidic channels was co-integrated with a III–V semiconductor thin-film PD. The fluorescent drops formed in the microfluidic device are successfully detected with an integrated thin-film PD on a silicon substrate. The proposed three-dimensional integration structure is an alternative approach to combine optical functions with microfluidic functions on silicon-based electronic functions.

Leading research report for fiscal 1999. Fundamental technology of spin electronic device; 1999 nendo spin toronikusu soshi kiban gijutsu kenkyu hokokusho

Energy Technology Data Exchange (ETDEWEB)

NONE

2000-03-01

The project, with attention paid to both spin and charge of electrons, aims to draw the best of the said two attributes of electrons by use of the state of the art in manufacturing technology for the creation of novel electronic devices. The nonvolatile MRAM (magnetic random access memory), which is the nearest to commercialization, is a tunnel device consisting of two sheet-shape ferromagnetic metal electrodes and an insulator film sandwiched between the said two electrodes, with the lower electrode magnetized only in one direction. The tunnel resistance changes when the magnetization direction in the upper electrode changes left and right (1, 0) according to an external writing magnetic field, and this enables nondestructive readout. The upper electrode magnetization direction remains unchanged thanks to hysteresis when the external writing magnetic field is turned off, and this allows the device to serve as a nonvolatile memory device. The device has a potential for higher speeds and enhanced integration. Much is also expected from a spin conduction functional device utilizing spin-dependent electric conduction, spin optical function device, spin quantum calculation directly utilizing quantum state, magnetic field sensor, etc. Their importance is great economically and socially, and technologies relating to magnetism and semiconductor should be merged for their further development. (NEDO)

Restoring proximal caries lesions conservatively with tunnel restorations.

Science.gov (United States)

Chu, Chun-Hung; Mei, May L; Cheung, Chloe; Nalliah, Romesh P

2013-07-30

The tunnel restoration has been suggested as a conservative alternative to the conventional box preparation for treating proximal caries. The main advantage of tunnel restoration over the conventional box or slot preparation includes being more conservative and increasing tooth integrity and strength by preserving the marginal ridge. However, tunnel restoration is technique-sensitive and can be particularly challenging for inexperienced restorative dentists. Recent advances in technology, such as the contemporary design of dental handpieces with advanced light-emitting diode (LED) and handheld comfort, offer operative dentists better vision, illumination, and maneuverability. The use of magnifying loupes also enhances the visibility of the preparation. The advent of digital radiographic imaging has improved dental imaging and reduced radiation. The new generation of restorative materials has improved mechanical properties. Tunnel restoration can be an option to restore proximal caries if the dentist performs proper case selection and pays attention to the details of the restorative procedures. This paper describes the clinical technique of tunnel restoration and reviews the studies of tunnel restorations.

Tunneling Photocurrent Assisted by Interlayer Excitons in Staggered van der Waals Hetero-Bilayers.

Science.gov (United States)

Luong, Dinh Hoa; Lee, Hyun Seok; Neupane, Guru Prakash; Roy, Shrawan; Ghimire, Ganesh; Lee, Jin Hee; Vu, Quoc An; Lee, Young Hee

2017-09-01

Vertically stacked van der Waals (vdW) heterostructures have been suggested as a robust platform for studying interfacial phenomena and related electric/optoelectronic devices. While the interlayer Coulomb interaction mediated by the vdW coupling has been extensively studied for carrier recombination processes in a diode transport, its correlation with the interlayer tunneling transport has not been elucidated. Here, a contrast is reported between tunneling and drift photocurrents tailored by the interlayer coupling strength in MoSe 2 /MoS 2 hetero-bilayers (HBs). The interfacial coupling modulated by thermal annealing is identified by the interlayer phonon coupling in Raman spectra and the emerging interlayer exciton peak in photoluminescence spectra. In strongly coupled HBs, positive photocurrents are observed owing to the inelastic band-to-band tunneling assisted by interlayer excitons that prevail over exciton recombinations. By contrast, weakly coupled HBs exhibit a negative photovoltaic diode behavior, manifested as a drift current without interlayer excitonic emissions. This study sheds light on tailoring the tunneling transport for numerous optoelectronic HB devices. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Using Quantum Confinement to Uniquely Identify Devices

Science.gov (United States)

Roberts, J.; Bagci, I. E.; Zawawi, M. A. M.; Sexton, J.; Hulbert, N.; Noori, Y. J.; Young, M. P.; Woodhead, C. S.; Missous, M.; Migliorato, M. A.; Roedig, U.; Young, R. J.

2015-11-01

Modern technology unintentionally provides resources that enable the trust of everyday interactions to be undermined. Some authentication schemes address this issue using devices that give a unique output in response to a challenge. These signatures are generated by hard-to-predict physical responses derived from structural characteristics, which lend themselves to two different architectures, known as unique objects (UNOs) and physically unclonable functions (PUFs). The classical design of UNOs and PUFs limits their size and, in some cases, their security. Here we show that quantum confinement lends itself to the provision of unique identities at the nanoscale, by using fluctuations in tunnelling measurements through quantum wells in resonant tunnelling diodes (RTDs). This provides an uncomplicated measurement of identity without conventional resource limitations whilst providing robust security. The confined energy levels are highly sensitive to the specific nanostructure within each RTD, resulting in a distinct tunnelling spectrum for every device, as they contain a unique and unpredictable structure that is presently impossible to clone. This new class of authentication device operates with minimal resources in simple electronic structures above room temperature.

Magnetoresistance of galfenol-based magnetic tunnel junction

International Nuclear Information System (INIS)

Gobaut, B.; Vinai, G.; Castán-Guerrero, C.; Krizmancic, D.; Panaccione, G.; Torelli, P.; Rafaqat, H.; Roddaro, S.; Rossi, G.; Eddrief, M.; Marangolo, M.

2015-01-01

The manipulation of ferromagnetic layer magnetization via electrical pulse is driving an intense research due to the important applications that this result will have on memory devices and sensors. In this study we realized a magnetotunnel junction in which one layer is made of Galfenol (Fe 1-x Ga x ) which possesses one of the highest magnetostrictive coefficient known. The multilayer stack has been grown by molecular beam epitaxy and e-beam evaporation. Optical lithography and physical etching have been combined to obtain 20x20 micron sized pillars. The obtained structures show tunneling conductivity across the junction and a tunnel magnetoresistance (TMR) effect of up to 11.5% in amplitude

Valley current characterization of high current density resonant tunnelling diodes for terahertz-wave applications

Science.gov (United States)

Jacobs, K. J. P.; Stevens, B. J.; Baba, R.; Wada, O.; Mukai, T.; Hogg, R. A.

2017-10-01

We report valley current characterisation of high current density InGaAs/AlAs/InP resonant tunnelling diodes (RTDs) grown by metal-organic vapour phase epitaxy (MOVPE) for THz emission, with a view to investigate the origin of the valley current and optimize device performance. By applying a dual-pass fabrication technique, we are able to measure the RTD I-V characteristic for different perimeter/area ratios, which uniquely allows us to investigate the contribution of leakage current to the valley current and its effect on the PVCR from a single device. Temperature dependent (20 - 300 K) characteristics for a device are critically analysed and the effect of temperature on the maximum extractable power (PMAX) and the negative differential conductance (NDC) of the device is investigated. By performing theoretical modelling, we are able to explore the effect of typical variations in structural composition during the growth process on the tunnelling properties of the device, and hence the device performance.

Suppression of tunneling by interference in half-integer--spin particles

OpenAIRE

Loss, Daniel; DiVincenzo, David P.; Grinstein, G.

1992-01-01

Within a wide class of ferromagnetic and antiferromagnetic systems, quantum tunneling of magnetization direction is spin-parity dependent: it vanishes for magnetic particles with half-integer spin, but is allowed for integer spin. A coherent-state path integral calculation shows that this topological effect results from interference between tunneling paths.

Near quantum limited amplification from inelastic Cooper-pair tunneling

Science.gov (United States)

Hofheinz, Max; Jebari, Salha; Blanchet, Florian; Grimm, Alexander; Hazra, Dibyendu; Albert, Romain; Portier, Fabien

Josephson parametric amplifiers approach quantum-limited noise performance but require strong external microwave pump tones which make them more difficult to use than DC powered amplifiers: The pump tone can affect the device under test and requires expensive room-temperature equipment. Inelastic Cooper pair tunneling processes through a small DC voltage-biased Josephson junction, where a tunneling Cooper pair dissipates its energy 2 eV in the form of two photons are reminiscent of parametric down conversion. We show that these processes can be used to provide amplification near the quantum limit without external microwave pump tone. We explain the measured gain and noise based on the P (E) theory of inelastic Cooper pair tunneling and general fluctuation-dissipation relations.

High performance vertical tunneling diodes using graphene/hexagonal boron nitride/graphene hetero-structure

Energy Technology Data Exchange (ETDEWEB)

Hwan Lee, Seung; Lee, Jia; Ho Ra, Chang; Liu, Xiaochi; Hwang, Euyheon [Samsung-SKKU Graphene Center (SSGC), Sungkyunkwan University, 2066, Seobu-ro, Jangan-gu, Suwon, Gyeonggi-do 440-746 (Korea, Republic of); Department of Nano Science and Technology, SKKU Advanced Institute of Nano-Technology (SAINT), Sungkyunkwan University, 2066, Seobu-ro, Jangan-gu, Suwon, Gyeonggi-do 440-746 (Korea, Republic of); Sup Choi, Min [Department of Nano Science and Technology, SKKU Advanced Institute of Nano-Technology (SAINT), Sungkyunkwan University, 2066, Seobu-ro, Jangan-gu, Suwon, Gyeonggi-do 440-746 (Korea, Republic of); Center for Human Interface Nano Technology (HINT), Sungkyunkwan University, 2066, Seobu-ro, Jangan-gu, Suwon, Gyeonggi-do 440-746 (Korea, Republic of); Hee Choi, Jun [Frontier Research Laboratory, Samsung Advanced Institute of Technology, Samsung Electronics Co., Ltd., Yongin, Gyeonggi-do 446-711 (Korea, Republic of); Zhong, Jianqiang; Chen, Wei [Department of Physics, National University of Singapore, 2 Science Drive 3, Singapore 117542 (Singapore); Department of Chemistry, National University of Singapore, 3 Science Drive 3, Singapore 117543 (Singapore); Jong Yoo, Won, E-mail: yoowj@skku.edu [Samsung-SKKU Graphene Center (SSGC), Sungkyunkwan University, 2066, Seobu-ro, Jangan-gu, Suwon, Gyeonggi-do 440-746 (Korea, Republic of); Department of Nano Science and Technology, SKKU Advanced Institute of Nano-Technology (SAINT), Sungkyunkwan University, 2066, Seobu-ro, Jangan-gu, Suwon, Gyeonggi-do 440-746 (Korea, Republic of); Center for Human Interface Nano Technology (HINT), Sungkyunkwan University, 2066, Seobu-ro, Jangan-gu, Suwon, Gyeonggi-do 440-746 (Korea, Republic of)

2014-02-03

A tunneling rectifier prepared from vertically stacked two-dimensional (2D) materials composed of chemically doped graphene electrodes and hexagonal boron nitride (h-BN) tunneling barrier was demonstrated. The asymmetric chemical doping to graphene with linear dispersion property induces rectifying behavior effectively, by facilitating Fowler-Nordheim tunneling at high forward biases. It results in excellent diode performances of a hetero-structured graphene/h-BN/graphene tunneling diode, with an asymmetric factor exceeding 1000, a nonlinearity of ∼40, and a peak sensitivity of ∼12 V{sup −1}, which are superior to contending metal-insulator-metal diodes, showing great potential for future flexible and transparent electronic devices.

Probability density of tunneled carrier states near heterojunctions calculated numerically by the scattering method.

Energy Technology Data Exchange (ETDEWEB)

Wampler, William R. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Myers, Samuel M. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Modine, Normand A. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

2017-09-01

The energy-dependent probability density of tunneled carrier states for arbitrarily specified longitudinal potential-energy profiles in planar bipolar devices is numerically computed using the scattering method. Results agree accurately with a previous treatment based on solution of the localized eigenvalue problem, where computation times are much greater. These developments enable quantitative treatment of tunneling-assisted recombination in irradiated heterojunction bipolar transistors, where band offsets may enhance the tunneling effect by orders of magnitude. The calculations also reveal the density of non-tunneled carrier states in spatially varying potentials, and thereby test the common approximation of uniform- bulk values for such densities.

Integrated Photoelectrochemical Solar Energy Conversion and Organic Redox Flow Battery Devices.

Science.gov (United States)

Li, Wenjie; Fu, Hui-Chun; Li, Linsen; Cabán-Acevedo, Miguel; He, Jr-Hau; Jin, Song

2016-10-10

Building on regenerative photoelectrochemical solar cells and emerging electrochemical redox flow batteries (RFBs), more efficient, scalable, compact, and cost-effective hybrid energy conversion and storage devices could be realized. An integrated photoelectrochemical solar energy conversion and electrochemical storage device is developed by integrating regenerative silicon solar cells and 9,10-anthraquinone-2,7-disulfonic acid (AQDS)/1,2-benzoquinone-3,5-disulfonic acid (BQDS) RFBs. The device can be directly charged by solar light without external bias, and discharged like normal RFBs with an energy storage density of 1.15 Wh L -1 and a solar-to-output electricity efficiency (SOEE) of 1.7 % over many cycles. The concept exploits a previously undeveloped design connecting two major energy technologies and promises a general approach for storing solar energy electrochemically with high theoretical storage capacity and efficiency. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

CMOS-compatible spintronic devices: a review

Science.gov (United States)

Makarov, Alexander; Windbacher, Thomas; Sverdlov, Viktor; Selberherr, Siegfried

2016-11-01

For many decades CMOS devices have been successfully scaled down to achieve higher speed and increased performance of integrated circuits at lower cost. Today’s charge-based CMOS electronics encounters two major challenges: power dissipation and variability. Spintronics is a rapidly evolving research and development field, which offers a potential solution to these issues by introducing novel ‘more than Moore’ devices. Spin-based magnetoresistive random-access memory (MRAM) is already recognized as one of the most promising candidates for future universal memory. Magnetic tunnel junctions, the main elements of MRAM cells, can also be used to build logic-in-memory circuits with non-volatile storage elements on top of CMOS logic circuits, as well as versatile compact on-chip oscillators with low power consumption. We give an overview of CMOS-compatible spintronics applications. First, we present a brief introduction to the physical background considering such effects as magnetoresistance, spin-transfer torque (STT), spin Hall effect, and magnetoelectric effects. We continue with a comprehensive review of the state-of-the-art spintronic devices for memory applications (STT-MRAM, domain wall-motion MRAM, and spin-orbit torque MRAM), oscillators (spin torque oscillators and spin Hall nano-oscillators), logic (logic-in-memory, all-spin logic, and buffered magnetic logic gate grid), sensors, and random number generators. Devices with different types of resistivity switching are analyzed and compared, with their advantages highlighted and challenges revealed. CMOS-compatible spintronic devices are demonstrated beginning with predictive simulations, proceeding to their experimental confirmation and realization, and finalized by the current status of application in modern integrated systems and circuits. We conclude the review with an outlook, where we share our vision on the future applications of the prospective devices in the area.

Energy efficient hybrid computing systems using spin devices

Science.gov (United States)

Sharad, Mrigank

Emerging spin-devices like magnetic tunnel junctions (MTJ's), spin-valves and domain wall magnets (DWM) have opened new avenues for spin-based logic design. This work explored potential computing applications which can exploit such devices for higher energy-efficiency and performance. The proposed applications involve hybrid design schemes, where charge-based devices supplement the spin-devices, to gain large benefits at the system level. As an example, lateral spin valves (LSV) involve switching of nanomagnets using spin-polarized current injection through a metallic channel such as Cu. Such spin-torque based devices possess several interesting properties that can be exploited for ultra-low power computation. Analog characteristic of spin current facilitate non-Boolean computation like majority evaluation that can be used to model a neuron. The magneto-metallic neurons can operate at ultra-low terminal voltage of ˜20mV, thereby resulting in small computation power. Moreover, since nano-magnets inherently act as memory elements, these devices can facilitate integration of logic and memory in interesting ways. The spin based neurons can be integrated with CMOS and other emerging devices leading to different classes of neuromorphic/non-Von-Neumann architectures. The spin-based designs involve `mixed-mode' processing and hence can provide very compact and ultra-low energy solutions for complex computation blocks, both digital as well as analog. Such low-power, hybrid designs can be suitable for various data processing applications like cognitive computing, associative memory, and currentmode on-chip global interconnects. Simulation results for these applications based on device-circuit co-simulation framework predict more than ˜100x improvement in computation energy as compared to state of the art CMOS design, for optimal spin-device parameters.

Four-state non-volatile memory in a multiferroic spin filter tunnel junction

Science.gov (United States)

Ruan, Jieji; Li, Chen; Yuan, Zhoushen; Wang, Peng; Li, Aidong; Wu, Di

2016-12-01

We report a spin filter type multiferroic tunnel junction with a ferromagnetic/ferroelectric bilayer barrier. Memory functions of a spin filter magnetic tunnel junction and a ferroelectric tunnel junction are combined in this single device, producing four non-volatile resistive states that can be read out in a non-destructive manner. This concept is demonstrated in a LaNiO3/Pr0.8Ca0.2MnO3/BaTiO3/La0.7Sr0.3MnO3 all-oxide tunnel junction. The ferromagnetic insulator Pr0.8Ca0.2MnO3 serves as the spin filter and the ferromagnetic metal La0.7Sr0.3MnO3 is the spin analyzer. The ferroelectric polarization reversal in the BaTiO3 barrier switches the tunneling barrier height to produce a tunneling electroresistance. The ferroelectric switching also modulates the spin polarization and the spin filtering efficiency in Pr0.8Ca0.2MnO3.

Improved multidimensional semiclassical tunneling theory.

Science.gov (United States)

Wagner, Albert F

2013-12-12

We show that the analytic multidimensional semiclassical tunneling formula of Miller et al. [Miller, W. H.; Hernandez, R.; Handy, N. C.; Jayatilaka, D.; Willets, A. Chem. Phys. Lett. 1990, 172, 62] is qualitatively incorrect for deep tunneling at energies well below the top of the barrier. The origin of this deficiency is that the formula uses an effective barrier weakly related to the true energetics but correctly adjusted to reproduce the harmonic description and anharmonic corrections of the reaction path at the saddle point as determined by second order vibrational perturbation theory. We present an analytic improved semiclassical formula that correctly includes energetic information and allows a qualitatively correct representation of deep tunneling. This is done by constructing a three segment composite Eckart potential that is continuous everywhere in both value and derivative. This composite potential has an analytic barrier penetration integral from which the semiclassical action can be derived and then used to define the semiclassical tunneling probability. The middle segment of the composite potential by itself is superior to the original formula of Miller et al. because it incorporates the asymmetry of the reaction barrier produced by the known reaction exoergicity. Comparison of the semiclassical and exact quantum tunneling probability for the pure Eckart potential suggests a simple threshold multiplicative factor to the improved formula to account for quantum effects very near threshold not represented by semiclassical theory. The deep tunneling limitations of the original formula are echoed in semiclassical high-energy descriptions of bound vibrational states perpendicular to the reaction path at the saddle point. However, typically ab initio energetic information is not available to correct it. The Supporting Information contains a Fortran code, test input, and test output that implements the improved semiclassical tunneling formula.

Fabricating a multi-level barrier-integrated microfluidic device using grey-scale photolithography

International Nuclear Information System (INIS)

Nam, Yoonkwang; Kim, Minseok; Kim, Taesung

2013-01-01

Most polymer-replica-based microfluidic devices are mainly fabricated by using standard soft-lithography technology so that multi-level masters (MLMs) require multiple spin-coatings, mask alignments, exposures, developments, and bakings. In this paper, we describe a simple method for fabricating MLMs for planar microfluidic channels with multi-level barriers (MLBs). A single photomask is necessary for standard photolithography technology to create a polydimethylsiloxane grey-scale photomask (PGSP), which adjusts the total amount of UV absorption in a negative-tone photoresist via a wide range of dye concentrations. Since the PGSP in turn adjusts the degree of cross-linking of the photoresist, this method enables the fabrication of MLMs for an MLB-integrated microfluidic device. Since the PGSP-based soft-lithography technology provides a simple but powerful fabrication method for MLBs in a microfluidic device, we believe that the fabrication method can be widely used for micro total analysis systems that benefit from MLBs. We demonstrate an MLB-integrated microfluidic device that can separate microparticles. (paper)

Spin-transfer torque in spin filter tunnel junctions

KAUST Repository

Ortiz Pauyac, Christian

2014-12-08

Spin-transfer torque in a class of magnetic tunnel junctions with noncollinear magnetizations, referred to as spin filter tunnel junctions, is studied within the tight-binding model using the nonequilibrium Green\\'s function technique within Keldysh formalism. These junctions consist of one ferromagnet (FM) adjacent to a magnetic insulator (MI) or two FM separated by a MI. We find that the presence of the magnetic insulator dramatically enhances the magnitude of the spin-torque components compared to conventional magnetic tunnel junctions. The fieldlike torque is driven by the spin-dependent reflection at the MI/FM interface, which results in a small reduction of its amplitude when an insulating spacer (S) is inserted to decouple MI and FM layers. Meanwhile, the dampinglike torque is dominated by the tunneling electrons that experience the lowest barrier height. We propose a device of the form FM/(S)/MI/(S)/FM that takes advantage of these characteristics and allows for tuning the spin-torque magnitudes over a wide range just by rotation of the magnetization of the insulating layer.

Spin-transfer torque in spin filter tunnel junctions

KAUST Repository

Ortiz Pauyac, Christian; Kalitsov, Alan; Manchon, Aurelien; Chshiev, Mairbek

2014-01-01

Spin-transfer torque in a class of magnetic tunnel junctions with noncollinear magnetizations, referred to as spin filter tunnel junctions, is studied within the tight-binding model using the nonequilibrium Green's function technique within Keldysh formalism. These junctions consist of one ferromagnet (FM) adjacent to a magnetic insulator (MI) or two FM separated by a MI. We find that the presence of the magnetic insulator dramatically enhances the magnitude of the spin-torque components compared to conventional magnetic tunnel junctions. The fieldlike torque is driven by the spin-dependent reflection at the MI/FM interface, which results in a small reduction of its amplitude when an insulating spacer (S) is inserted to decouple MI and FM layers. Meanwhile, the dampinglike torque is dominated by the tunneling electrons that experience the lowest barrier height. We propose a device of the form FM/(S)/MI/(S)/FM that takes advantage of these characteristics and allows for tuning the spin-torque magnitudes over a wide range just by rotation of the magnetization of the insulating layer.

Numerical Simulation of Tunneling Current in an Anisotropic Metal-Oxide-Semiconductor Capacitor

Directory of Open Access Journals (Sweden)

Khairurrijal khairurrijal

2012-09-01

Full Text Available In this paper, we have developed a model of the tunneling currents through a high-k dielectric stack in MOS capacitors with anisotropic masses. The transmittance was numerically calculated by employing a transfer matrix method and including longitudinal-transverse kinetic energy coupling which is represented by an electron phase velocity in the gate. The transmittance was then applied to calculate tunneling currents in TiN/HfSiOxN/SiO2/p-Si MOS capacitors. The calculated results show that as the gate electron velocity increases, the transmittance decreases and therefore the tunneling current reduces. The tunneling current becomes lower as the effective oxide thickness (EOT of HfSiOxN layer increases. When the incident electron passed through the barriers in the normal incident to the interface, the electron tunneling process becomes easier. It was also shown that the tunneling current was independent of the substrate orientation. Moreover, the model could be used in designing high speed MOS devices with low tunneling currents.

Silicon integrated circuits advances in materials and device research

CERN Document Server

Kahng, Dawon

1981-01-01

Silicon Integrated Circuits, Part B covers the special considerations needed to achieve high-power Si-integrated circuits. The book presents articles about the most important operations needed for the high-power circuitry, namely impurity diffusion and oxidation; crystal defects under thermal equilibrium in silicon and the development of high-power device physics; and associated technology. The text also describes the ever-evolving processing technology and the most promising approaches, along with the understanding of processing-related areas of physics and chemistry. Physicists, chemists, an

Understanding quantum tunneling using diffusion Monte Carlo simulations

Science.gov (United States)

Inack, E. M.; Giudici, G.; Parolini, T.; Santoro, G.; Pilati, S.

2018-03-01

In simple ferromagnetic quantum Ising models characterized by an effective double-well energy landscape the characteristic tunneling time of path-integral Monte Carlo (PIMC) simulations has been shown to scale as the incoherent quantum-tunneling time, i.e., as 1 /Δ2 , where Δ is the tunneling gap. Since incoherent quantum tunneling is employed by quantum annealers (QAs) to solve optimization problems, this result suggests that there is no quantum advantage in using QAs with respect to quantum Monte Carlo (QMC) simulations. A counterexample is the recently introduced shamrock model (Andriyash and Amin, arXiv:1703.09277), where topological obstructions cause an exponential slowdown of the PIMC tunneling dynamics with respect to incoherent quantum tunneling, leaving open the possibility for potential quantum speedup, even for stoquastic models. In this work we investigate the tunneling time of projective QMC simulations based on the diffusion Monte Carlo (DMC) algorithm without guiding functions, showing that it scales as 1 /Δ , i.e., even more favorably than the incoherent quantum-tunneling time, both in a simple ferromagnetic system and in the more challenging shamrock model. However, a careful comparison between the DMC ground-state energies and the exact solution available for the transverse-field Ising chain indicates an exponential scaling of the computational cost required to keep a fixed relative error as the system size increases.

Tunneling current in HfO2 and Hf0.5Zr0.5O2-based ferroelectric tunnel junction

Science.gov (United States)

Dong, Zhipeng; Cao, Xi; Wu, Tong; Guo, Jing

2018-03-01

Ferroelectric tunnel junctions (FTJs) have been intensively explored for future low power data storage and information processing applications. Among various ferroelectric (FE) materials studied, HfO2 and H0.5Zr0.5O2 (HZO) have the advantage of CMOS process compatibility. The validity of the simple effective mass approximation, for describing the tunneling process in these materials, is examined by computing the complex band structure from ab initio simulations. The results show that the simple effective mass approximation is insufficient to describe the tunneling current in HfO2 and HZO materials, and quantitative accurate descriptions of the complex band structures are indispensable for calculation of the tunneling current. A compact k . p Hamiltonian is parameterized to and validated by ab initio complex band structures, which provides a method for efficiently and accurately computing the tunneling current in HfO2 and HZO. The device characteristics of a metal/FE/metal structure and a metal/FE/semiconductor (M-F-S) structure are investigated by using the non-equilibrium Green's function formalism with the parameterized effective Hamiltonian. The result shows that the M-F-S structure offers a larger resistance window due to an extra barrier in the semiconductor region at off-state. A FTJ utilizing M-F-S structure is beneficial for memory design.

Toward Wearable Self-Charging Power Systems: The Integration of Energy-Harvesting and Storage Devices.

Science.gov (United States)

Pu, Xiong; Hu, Weiguo; Wang, Zhong Lin

2018-01-01

One major challenge for wearable electronics is that the state-of-the-art batteries are inadequate to provide sufficient energy for long-term operations, leading to inconvenient battery replacement or frequent recharging. Other than the pursuit of high energy density of secondary batteries, an alternative approach recently drawing intensive attention from the research community, is to integrate energy-generation and energy-storage devices into self-charging power systems (SCPSs), so that the scavenged energy can be simultaneously stored for sustainable power supply. This paper reviews recent developments in SCPSs with the integration of various energy-harvesting devices (including piezoelectric nanogenerators, triboelectric nanogenerators, solar cells, and thermoelectric nanogenerators) and energy-storage devices, such as batteries and supercapacitors. SCPSs with multiple energy-harvesting devices are also included. Emphasis is placed on integrated flexible or wearable SCPSs. Remaining challenges and perspectives are also examined to suggest how to bring the appealing SCPSs into practical applications in the near future. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Simplified tunnelling current calculation for MOS structures with ultra-thin oxides for conductive atomic force microscopy investigations

International Nuclear Information System (INIS)

Frammelsberger, Werner; Benstetter, Guenther; Stamp, Richard; Kiely, Janice; Schweinboeck, Thomas

2005-01-01

As charge tunnelling through thin and ultra-thin silicon dioxide layers is regarded as the driving force for MOS device degradation the determination and characterisation of electrically week spots is of paramount importance for device reliability and failure analysis. Conductive atomic force microscopy (C-AFM) is able to address this issue with a spatial resolution smaller than the expected breakdown spot. For the determination of the electrically active oxide thickness in practice an easy to use model with sufficient accuracy and which is largely independent of the oxide thickness is required. In this work a simplified method is presented that meets these demands. The electrically active oxide thickness is determined by matching of C-AFM voltage-current curves and a tunnelling current model, which is based on an analytical tunnelling current approximation. The model holds for both the Fowler-Nordheim tunnelling and the direct tunnelling regime with one single tunnelling parameter set. The results show good agreement with macroscopic measurements for gate voltages larger than approximately 0.5-1 V, and with microscopic C-AFM measurements. For this reason arbitrary oxides in the DT and the FNT regime may be analysed with high lateral resolution by C-AFM, without the need of a preselection of the tunnelling regime to be addressed

Integrated nanohole array surface plasmon resonance sensing device using a dual-wavelength source

International Nuclear Information System (INIS)

Escobedo, C; Vincent, S; Choudhury, A I K; Campbell, J; Gordon, R; Brolo, A G; Sinton, D

2011-01-01

In this paper, we demonstrate a compact integrated nanohole array-based surface plasmon resonance sensing device. The unit includes a LED light source, driving circuitry, CCD detector, microfluidic network and computer interface, all assembled from readily available commercial components. A dual-wavelength LED scheme was implemented to increase spectral diversity and isolate intensity variations to be expected in the field. The prototype shows bulk sensitivity of 266 pixel intensity units/RIU and a limit of detection of 6 × 10 −4 RIU. Surface binding tests were performed, demonstrating functionality as a surface-based sensing system. This work is particularly relevant for low-cost point-of-care applications, especially those involving multiple tests and field studies. While nanohole arrays have been applied to many sensing applications, and their suitability to device integration is well established, this is the first demonstration of a fully integrated nanohole array-based sensing device.

Classification of DNA nucleotides with transverse tunneling currents

Science.gov (United States)

Pedersen, Jonas Nyvold; Boynton, Paul; Ventra, Massimiliano Di; Jauho, Antti-Pekka; Flyvbjerg, Henrik

2016-01-01

It has been theoretically suggested and experimentally demonstrated that fast and low-cost sequencing of DNA, RNA, and peptide molecules might be achieved by passing such molecules between electrodes embedded in a nanochannel. The experimental realization of this scheme faces major challenges, however. In realistic liquid environments, typical currents in tunnelling devices are of the order of picoamps. This corresponds to only six electrons per microsecond, and this number affects the integration time required to do current measurements in real experiments. This limits the speed of sequencing, though current fluctuations due to Brownian motion of the molecule average out during the required integration time. Moreover, data acquisition equipment introduces noise, and electronic filters create correlations in time-series data. We discuss how these effects must be included in the analysis of, e.g., the assignment of specific nucleobases to current signals. As the signals from different molecules overlap, unambiguous classification is impossible with a single measurement. We argue that the assignment of molecules to a signal is a standard pattern classification problem and calculation of the error rates is straightforward. The ideas presented here can be extended to other sequencing approaches of current interest. PMID:27897144

Classification of DNA nucleotides with transverse tunneling currents

Science.gov (United States)

Nyvold Pedersen, Jonas; Boynton, Paul; Di Ventra, Massimiliano; Jauho, Antti-Pekka; Flyvbjerg, Henrik

2017-01-01

It has been theoretically suggested and experimentally demonstrated that fast and low-cost sequencing of DNA, RNA, and peptide molecules might be achieved by passing such molecules between electrodes embedded in a nanochannel. The experimental realization of this scheme faces major challenges, however. In realistic liquid environments, typical currents in tunneling devices are of the order of picoamps. This corresponds to only six electrons per microsecond, and this number affects the integration time required to do current measurements in real experiments. This limits the speed of sequencing, though current fluctuations due to Brownian motion of the molecule average out during the required integration time. Moreover, data acquisition equipment introduces noise, and electronic filters create correlations in time-series data. We discuss how these effects must be included in the analysis of, e.g., the assignment of specific nucleobases to current signals. As the signals from different molecules overlap, unambiguous classification is impossible with a single measurement. We argue that the assignment of molecules to a signal is a standard pattern classification problem and calculation of the error rates is straightforward. The ideas presented here can be extended to other sequencing approaches of current interest.

Nb/NiCu bilayers in single and stacked superconductive tunnel junctions: preliminary results

International Nuclear Information System (INIS)

Pepe, G.P.; Ruotolo, A.; Parlato, L.; Peluso, G.; Ausanio, G.; Carapella, G.; Latempa, R.

2004-01-01

We present preliminary experimental results concerning both single and stacked tunnel junctions in which one of the electrodes was formed by a superconductor/ferromagnet (S/F) bi-layer. In particular, in the stacked configuration a Nb/NiCu bi-layer was used as the intermediate electrode, and it was probed by tunneling on both sides. Tunnel junctions have been characterized in terms of current-voltage characteristics (IVC), and differential conductance. Preliminary steady-state injection-detection measurements performed in the stacked devices at T=4.2 K are also presented and discussed

Low band-to-band tunnelling and gate tunnelling current in novel nanoscale double-gate architecture: simulations and investigation

International Nuclear Information System (INIS)

Datta, Deepanjan; Ganguly, Samiran; Dasgupta, S

2007-01-01

Large band-to-band tunnelling (BTBT) and gate leakage current can limit scalability of nanoscale devices. In this paper, we have proposed a novel nanoscale parallel connected heteromaterial double gate (PCHEM-DG) architecture with triple metal gate which significantly suppress BTBT leakage, making it efficient for low power design in the sub-10 nm regime. We have also proposed a triple gate device with p + poly-n + poly-p + poly gate which has substantially low gate leakage over symmetric DG MOSFET. Simulations are performed using a 2D Poisson-Schroedinger simulator and verified with a 2D device simulator ATLAS. We conclude that, due to intrinsic body doping, negligible gate leakage, suppressed BTBT over symmetric DG devices, metal gate (MG) PCHEM-DG MOSFET is efficient for low power circuit design in the nanometre regime

Power and hydrogen production from ammonia in a micro-thermophotovoltaic device integrated with a micro-reformer

International Nuclear Information System (INIS)

Um, Dong Hyun; Kim, Tae Young; Kwon, Oh Chae

2014-01-01

Power and hydrogen (H 2 ) production by burning and reforming ammonia (NH 3 ) in a micro-TPV (microscale-thermophotovoltaic) device integrated with a micro-reformer is studied experimentally. A heat-recirculating micro-emitter with the cyclone and helical adapters that enhance the residence time of fed fuel-air mixtures and uniform burning burns H 2 -added NH 3 -air mixtures. A micro-reformer that converts NH 3 to H 2 using ruthenium as a catalyst surrounds the micro-emitter as a heat source. The micro-reformer is surrounded by a chamber, the inner and outer walls of which have installations of gallium antimonide photovoltaic cells and cooling fins. For the micro-reformer-integrated micro-TPV device the maximum overall efficiency of 8.1% with electrical power of 4.5 W and the maximum NH 3 conversion rate of 96.0% with the H 2 production rate of 22.6 W (based on lower heating value) are obtained, indicating that the overall efficiency is remarkably enhanced compared with 2.0% when the micro-TPV device operates alone. This supports the potential of improving the overall efficiency of a micro-TPV device through integrating it with a micro-reformer. Also, the feasibility of using NH 3 as a carbon-free fuel for both burning and reforming in practical micro power and H 2 generation devices has been demonstrated. - Highlights: • Performance of micro-TPV device integrated with micro-reformer is evaluated. • Feasibility of using NH 3 –H 2 blends in integrated system has been demonstrated. • Integration with micro-reformer improves performance of micro-TPV device. • Maximum overall efficiency of 8.1% is found compared with 2.0% without integration

Performance improvement in novel germanium-tin/germanium heterojunction-enhanced p-channel tunneling field-effect transistor

Science.gov (United States)

Wang, Hongjuan; Liu, Yan; Liu, Mingshan; Zhang, Qingfang; Zhang, Chunfu; Ma, Xiaohua; Zhang, Jincheng; Hao, Yue; Han, Genquan

2015-07-01

We design a novel GeSn-based heterojunction-enhanced p-channel tunneling field-effect transistor (HE-PTFET) with a Ge0.92Sn0.08/Ge heterojunction located in channel region, at a distance of LT-H from the Ge0.92Sn0.08 source-channel tunneling junction (TJ). HE-PTFETs demonstrate the negative shift of onset voltage VONSET, the steeper subthreshold swing S, and the improved on-state current ION compared to Ge0.92Sn0.08 homo-PTFET. At low VGS, the suppression of BTBT due to the widening of the tunneling barrier caused by the heterojunction leads to a negative shift of VONSET in HE-PTFETs. At high VGS, ION enhancement in HE-PTFETs is achieved over the homo device, which is attributed to the confinement of BTBT in Ge0.92Sn0.08 source-channel TJ region by the heterojunction, where the short tunneling paths lead to a high tunneling probability. Due to the steeper average S, HE-PTFET with a 6 nm LT-H achieves a 4 times higher ION compared to homo device at a VDD of -0.3 V.

Impact of semiconducting electrodes on the electroresistance of ferroelectric tunnel junctions

Science.gov (United States)

Asa, M.; Bertacco, R.

2018-02-01

Ferroelectric tunnel junctions are promising candidates for the realization of energy-efficient digital memories and analog memcomputing devices. In this work, we investigate the impact of a semiconducting layer in series to the junction on the sign of electroresistance. To this scope, we compare tunnel junctions fabricated out of Pt/BaTiO3/La1/3Sr2/3MnO3 (LSMO) and Pt/BaTiO3/Nb:SrTiO3 (Nb:STO) heterostructures, displaying an opposite sign of the electroresistance. By capacitance-voltage profiling, we observe a behavior typical of Metal-Oxide-Semiconductor tunnel devices in both cases but compatible with the opposite sign of charge carriers in the semiconducting layer. While Nb:STO displays the expected n-type semiconducting character, metallic LSMO develops an interfacial p-type semiconducting layer. The different types of carriers at the semiconducting interfaces and the modulation of the depleted region by the ferroelectric charge have a deep impact on electroresistance, possibly accounting for the different sign observed in the two systems.

Step tunneling enhanced asymmetry in metal-insulator-insulator-metal (MIIM) diodes for rectenna applications

Science.gov (United States)

Alimardani, N.; Conley, J. F.

2013-09-01

We combine nanolaminate bilayer insulator tunnel barriers (Al2O3/HfO2, HfO2/Al2O3, Al2O3/ZrO2) deposited via atomic layer deposition (ALD) with asymmetric work function metal electrodes to produce MIIM diodes with enhanced I-V asymmetry and non-linearity. We show that the improvements in MIIM devices are due to step tunneling rather than resonant tunneling. We also investigate conduction processes as a function of temperature in MIM devices with Nb2O5 and Ta2O5 high electron affinity insulators. For both Nb2O5 and Ta2O5 insulators, the dominant conduction process is established as Schottky emission at small biases and Frenkel-Poole emission at large biases. The energy depth of the traps that dominate Frenkel-Poole emission in each material are estimated.

Detecting stray microwaves and nonequilibrium quasiparticles in thin films by single-electron tunneling

Science.gov (United States)

Saira, Olli-Pentti; Maisi, Ville; Kemppinen, Antti; Möttönen, Mikko; Pekola, Jukka

2013-03-01

Superconducting thin films and tunnel junctions are the building blocks of many state-of-the-art technologies related to quantum information processing, microwave detection, and electronic amplification. These devices operate at millikelvin temperatures, and - in a naive picture - their fidelity metrics are expected to improve as the temperature is lowered. However, very often one finds in the experiment that the device performance levels off around 100-150 mK. In my presentation, I will address three common physical mechanisms that can cause such saturation: stray microwaves, nonequilibrium quasiparticles, and sub-gap quasiparticle states. The new experimental data I will present is based on a series of studies on quasiparticle transport in Coulomb-blockaded normal-insulator-superconductor tunnel junction devices. We have used a capacitively coupled SET electrometer to detect individual quasiparticle tunneling events in real time. We demonstrate the following record-low values for thin film aluminum: quasiparticle density nqp < 0 . 033 / μm3 , normalized density of sub-gap quasiparticle states (Dynes parameter) γ < 1 . 6 ×10-7 . I will also discuss some sample stage and chip designs that improve microwave shielding.

Magnetoresistance of galfenol-based magnetic tunnel junction

Energy Technology Data Exchange (ETDEWEB)

Gobaut, B., E-mail: benoit.gobaut@elettra.eu [Sincrotrone Trieste S.C.p.A., S.S. 14 Km 163.5, Area Science Park, 34149 Trieste (Italy); Vinai, G.; Castán-Guerrero, C.; Krizmancic, D.; Panaccione, G.; Torelli, P. [Laboratorio TASC, IOM-CNR, S.S. 14km 163.5, Basovizza, 34149 Trieste (Italy); Rafaqat, H. [Laboratorio TASC, IOM-CNR, S.S. 14km 163.5, Basovizza, 34149 Trieste (Italy); ICTP, Trieste (Italy); Roddaro, S. [Laboratorio TASC, IOM-CNR, S.S. 14km 163.5, Basovizza, 34149 Trieste (Italy); NEST, Scuola Normale Superiore and Istituto Nanoscienze-CNR, Piazza S. Silvestro 12, 56127 Pisa (Italy); Rossi, G. [Laboratorio TASC, IOM-CNR, S.S. 14km 163.5, Basovizza, 34149 Trieste (Italy); Dipartimento di Fisica, Università di Milano, via Celoria 16, 20133 Milano (Italy); Eddrief, M.; Marangolo, M. [Sorbonne Universités, UPMC Paris 06, CNRS-UMR 7588, Institut des Nanosciences de Paris, 75005, Paris (France)

2015-12-15

The manipulation of ferromagnetic layer magnetization via electrical pulse is driving an intense research due to the important applications that this result will have on memory devices and sensors. In this study we realized a magnetotunnel junction in which one layer is made of Galfenol (Fe{sub 1-x}Ga{sub x}) which possesses one of the highest magnetostrictive coefficient known. The multilayer stack has been grown by molecular beam epitaxy and e-beam evaporation. Optical lithography and physical etching have been combined to obtain 20x20 micron sized pillars. The obtained structures show tunneling conductivity across the junction and a tunnel magnetoresistance (TMR) effect of up to 11.5% in amplitude.

Reflection effect of localized absorptive potential on non-resonant and resonant tunneling

International Nuclear Information System (INIS)

Rubio, A.; Kumar, N.

1992-06-01

The reflection due to absorptive potential (-iV i ) for resonant and non-resonant tunneling has been considered. We show that the effect of reflection leads to a non-monotonic dependence of absorption on the strength V i with a maximum absorption of typically 0.5. This has implications for the operation of resonant tunneling devices. General conceptual aspects of absorptive potentials are discussed. (author). 9 refs, 2 figs

Auger generation as an intrinsic limit to tunneling field-effect transistor performance

International Nuclear Information System (INIS)

Teherani, James T.; Agarwal, Sapan; Chern, Winston; Antoniadis, Dimitri A.; Solomon, Paul M.; Yablonovitch, Eli

2016-01-01

Many in the microelectronics field view tunneling field-effect transistors (TFETs) as society's best hope for achieving a >10× power reduction for electronic devices; however, despite a decade of considerable worldwide research, experimental TFET results have significantly underperformed simulations and conventional MOSFETs. To explain the discrepancy between TFET experiments and simulations, we investigate the parasitic leakage current due to Auger generation, an intrinsic mechanism that cannot be mitigated with improved material quality or better device processing. We expose the intrinsic link between the Auger and band-to-band tunneling rates, highlighting the difficulty of increasing one without the other. From this link, we show that Auger generation imposes a fundamental limit on ultimate TFET performance.

Auger generation as an intrinsic limit to tunneling field-effect transistor performance

Energy Technology Data Exchange (ETDEWEB)

Teherani, James T., E-mail: j.teherani@columbia.edu [Department of Electrical Engineering, Columbia University, New York, New York 10027 (United States); Agarwal, Sapan [Sandia National Laboratories, Albuquerque, New Mexico 87123 (United States); Chern, Winston; Antoniadis, Dimitri A. [Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States); Solomon, Paul M. [IBM T.J. Watson Research Center, Yorktown Heights, New York 10598 (United States); Yablonovitch, Eli [Department of Electrical Engineering and Computer Sciences, University of California, Berkeley, California 94720 (United States)

2016-08-28

Many in the microelectronics field view tunneling field-effect transistors (TFETs) as society's best hope for achieving a >10× power reduction for electronic devices; however, despite a decade of considerable worldwide research, experimental TFET results have significantly underperformed simulations and conventional MOSFETs. To explain the discrepancy between TFET experiments and simulations, we investigate the parasitic leakage current due to Auger generation, an intrinsic mechanism that cannot be mitigated with improved material quality or better device processing. We expose the intrinsic link between the Auger and band-to-band tunneling rates, highlighting the difficulty of increasing one without the other. From this link, we show that Auger generation imposes a fundamental limit on ultimate TFET performance.

Self-Assembled Core-Satellite Gold Nanoparticle Networks for Ultrasensitive Detection of Chiral Molecules by Recognition Tunneling Current.

Science.gov (United States)

Zhang, Yuanchao; Liu, Jingquan; Li, Da; Dai, Xing; Yan, Fuhua; Conlan, Xavier A; Zhou, Ruhong; Barrow, Colin J; He, Jin; Wang, Xin; Yang, Wenrong

2016-05-24

Chirality sensing is a very challenging task. Here, we report a method for ultrasensitive detection of chiral molecule l/d-carnitine based on changes in the recognition tunneling current across self-assembled core-satellite gold nanoparticle (GNP) networks. The recognition tunneling technique has been demonstrated to work at the single molecule level where the binding between the reader molecules and the analytes in a nanojunction. This process was observed to generate a unique and sensitive change in tunneling current, which can be used to identify the analytes of interest. The molecular recognition mechanism between amino acid l-cysteine and l/d-carnitine has been studied with the aid of SERS. The different binding strength between homo- or heterochiral pairs can be effectively probed by the copper ion replacement fracture. The device resistance was measured before and after the sequential exposures to l/d-carnitine and copper ions. The normalized resistance change was found to be extremely sensitive to the chirality of carnitine molecule. The results suggested that a GNP networks device optimized for recognition tunneling was successfully built and that such a device can be used for ultrasensitive detection of chiral molecules.

Inducer Hydrodynamic Load Measurement Devices

Science.gov (United States)

Skelley, Stephen E.; Zoladz, Thomas F.

2002-01-01

Marshall Space Flight Center (MSFC) has demonstrated two measurement devices for sensing and resolving the hydrodynamic loads on fluid machinery. The first - a derivative of the six component wind tunnel balance - senses the forces and moments on the rotating device through a weakened shaft section instrumented with a series of strain gauges. This "rotating balance" was designed to directly measure the steady and unsteady hydrodynamic loads on an inducer, thereby defining both the amplitude and frequency content associated with operating in various cavitation modes. The second device - a high frequency response pressure transducer surface mounted on a rotating component - was merely an extension of existing technology for application in water. MSFC has recently completed experimental evaluations of both the rotating balance and surface-mount transducers in a water test loop. The measurement bandwidth of the rotating balance was severely limited by the relative flexibility of the device itself, resulting in an unexpectedly low structural bending mode and invalidating the higher frequency response data. Despite these limitations, measurements confirmed that the integrated loads on the four-bladed inducer respond to both cavitation intensity and cavitation phenomena. Likewise, the surface-mount pressure transducers were subjected to a range of temperatures and flow conditions in a non-rotating environment to record bias shifts and transfer functions between the transducers and a reference device. The pressure transducer static performance was within manufacturer's specifications and dynamic response accurately followed that of the reference.

Characteristics of titanium oxide memristor with coexistence of dopant drift and a tunnel barrier

International Nuclear Information System (INIS)

Tian Xiao-Bo; Xu Hui

2014-01-01

The recent published experimental data of titanium oxide memristor devices which are tested under the same experimental conditions exhibit the strange instability and complexity of these devices. Such undesired characteristics preclude the understanding of the device conductive processes and the memristor-based practical applications. The possibility of the coexistence of dopant drift and tunnel barrier conduction in a memristor provides preliminary explanations for the undesired characteristics. However, current research lacks detailed discussion about the coexistence case. In this paper, dopant drift and tunnel barrier-based theories are first analyzed for studying the relations between parameters and physical variables which affect characteristics of memristors, and then the influences of each parameter change on the conductive behaviors in the single and coexistence cases of the two mechanisms are simulated and discussed respectively. The simulation results provide further explanations of the complex device conduction. Theoretical methods of eliminating or reducing the coexistence of the two mechanisms are proposed, in order to increase the stability of the device conduction. This work also provides the support for optimizing the fabrications of memristor devices with excellent performance

Tunnel boring machine applications

International Nuclear Information System (INIS)

Bhattacharyya, K.K.; McDonald, R.; Saunders, R.S.

1992-01-01

This paper reports that characterization of Yucca Mountain for a potential repository requires construction of an underground Exploratory Studies Facility (ESF). Mechanical excavating methods have been proposed for construction of the ESF as they offer a number of advantages over drilling and blasting at the Yucca Mountain site, including; less ground disturbance and therefore a potential for less adverse effects on the integrity of the site, creation of a more stable excavation cross section requiring less ground support, and an inherently safer and cleaner working environment. The tunnel boring machine (TBM) provides a proven technology for excavating the welded and unwelded Yucca Mountain tuffs. The access ramps and main underground tunnels form the largest part of the ESF underground construction work, and have been designed for excavation by TBM

The two Josephson junction flux qubit with large tunneling amplitude

International Nuclear Information System (INIS)

Shnurkov, V.I.; Soroka, A.A.; Mel'nik, S.I.

2008-01-01

In this paper we discuss solid-state nanoelectronic realizations of Josephson flux qubits with large tunneling amplitude between the two macroscopic states. The latter can be controlled via the height and form of the potential barrier, which is determined by quantum-state engineering of the flux qubit circuit. The simplest circuit of the flux qubit is a superconducting loop interrupted by a Josephson nanoscale tunnel junction. The tunneling amplitude between two macroscopically different states can be increased substantially by engineering of the qubit circuit if the tunnel junction is replaced by a ScS contact. However, only Josephson tunnel junctions are particularly suitable for large-scale integration circuits and quantum detectors with present-day technology. To overcome this difficulty we consider here a flux qubit with high energy-level separation between the 'ground' and 'excited' states, consisting of a superconducting loop with two low-capacitance Josephson tunnel junctions in series. We demonstrate that for real parameters of resonant superposition between the two macroscopic states the tunneling amplitude can reach values greater than 1 K. Analytical results for the tunneling amplitude obtained within the semiclassical approximation by the instanton technique show good correlation with a numerical solution

A design approach for integrating thermoelectric devices using topology optimization

DEFF Research Database (Denmark)

Soprani, Stefano; Haertel, Jan Hendrik Klaas; Lazarov, Boyan Stefanov

2016-01-01

Efficient operation of thermoelectric devices strongly relies on the thermal integration into the energy conversion system in which they operate. Effective thermal integration reduces the temperature differences between the thermoelectric module and its thermal reservoirs, allowing the system...... to operate more efficiently. This work proposes and experimentally demonstrates a topology optimization approach as a design tool for efficient integration of thermoelectric modules into systems with specific design constraints. The approach allows thermal layout optimization of thermoelectric systems...... for different operating conditions and objective functions, such as temperature span, efficiency, and power recoveryrate. As a specific application, the integration of a thermoelectric cooler into the electronics section ofa downhole oil well intervention tool is investigated, with the objective of minimizing...

Interconnected magnetic tunnel junctions for spin-logic applications

Science.gov (United States)

Manfrini, Mauricio; Vaysset, Adrien; Wan, Danny; Raymenants, Eline; Swerts, Johan; Rao, Siddharth; Zografos, Odysseas; Souriau, Laurent; Gavan, Khashayar Babaei; Rassoul, Nouredine; Radisic, Dunja; Cupak, Miroslav; Dehan, Morin; Sayan, Safak; Nikonov, Dmitri E.; Manipatruni, Sasikanth; Young, Ian A.; Mocuta, Dan; Radu, Iuliana P.

2018-05-01

With the rapid progress of spintronic devices, spin-logic concepts hold promises of energy-delay conscious computation for efficient logic gate operations. We report on the electrical characterization of domain walls in interconnected magnetic tunnel junctions. By means of spin-transfer torque effect, domains walls are produced at the common free layer and its propagation towards the output pillar sensed by tunneling magneto-resistance. Domain pinning conditions are studied quasi-statically showing a strong dependence on pillar size, ferromagnetic free layer width and inter-pillar distance. Addressing pinning conditions are detrimental for cascading and fan-out of domain walls across nodes, enabling the realization of domain-wall-based logic technology.

Semiconductor Devices Inspired By and Integrated With Biology

Energy Technology Data Exchange (ETDEWEB)

Rogers, John [University of Illinois

2012-04-25

Biology is curved, soft and elastic; silicon wafers are not. Semiconductor technologies that can bridge this gap in form and mechanics will create new opportunities in devices that adopt biologically inspired designs or require intimate integration with the human body. This talk describes the development of ideas for electronics that offer the performance of state-of-the-art, wafer- based systems but with the mechanical properties of a rubber band. We explain the underlying materials science and mechanics of these approaches, and illustrate their use in (1) bio- integrated, ‘tissue-like’ electronics with unique capabilities for mapping cardiac and neural electrophysiology, and (2) bio-inspired, ‘eyeball’ cameras with exceptional imaging properties enabled by curvilinear, Petzval designs.

Integrating mobile devices into nursing curricula: opportunities for implementation using Rogers' Diffusion of Innovation model.

Science.gov (United States)

Doyle, Glynda J; Garrett, Bernie; Currie, Leanne M

2014-05-01

To identify studies reporting mobile device integration into undergraduate and graduate nursing curricula. To explore the potential use of Rogers' Diffusion of Innovation model as a framework to guide implementation of mobile devices into nursing curricula. Literature review and thematic categorization. Literature published up until June 2013 was searched using EBSCO, PubMed, and Google Scholar. The literature was reviewed for research articles pertaining to mobile device use in nursing education. Research articles were grouped by study design, and articles were classified by: 1) strategies for individual adopters and 2) strategies for organizations. Rogers' Diffusion of Innovation theory was used to categorize reported implementation strategies. Fifty-two research studies were identified. Strategies for implementation were varied, and challenges to integrating mobile devices include lack of administrative support and time/funding to educate faculty as well as students. Overall, the use of mobile devices appears to provide benefits to nursing students; however the research evidence is limited. Anticipating challenges and ensuring a well laid out strategic plan can assist in supporting successful integration of mobile devices. Crown Copyright © 2013. Published by Elsevier Ltd. All rights reserved.

Does the graft-tunnel friction influence knee joint kinematics and biomechanics after anterior cruciate ligament reconstruction? A finite element study.

Science.gov (United States)

Wan, Chao; Hao, Zhixiu

2018-02-01

Graft tissues within bone tunnels remain mobile for a long time after anterior cruciate ligament (ACL) reconstruction. However, whether the graft-tunnel friction affects the finite element (FE) simulation of the ACL reconstruction is still unclear. Four friction coefficients (from 0 to 0.3) were simulated in the ACL-reconstructed joint model as well as two loading levels of anterior tibial drawer. The graft-tunnel friction did not affect joint kinematics and the maximal principal strain of the graft. By contrast, both the relative graft-tunnel motion and equivalent strain for the bone tunnels were altered, which corresponded to different processes of graft-tunnel integration and bone remodeling, respectively. It implies that the graft-tunnel friction should be defined properly for studying the graft-tunnel integration or bone remodeling after ACL reconstruction using numerical simulation.

Final report on the Controlled Cold Helium Spill Test in the LHC tunnel at CERN

CERN Document Server

Dufay-Chanat, L; Casas-Cubillos, J; Chorowski, M; Grabowski, M; Jedrusyna, A; Lindell, G; Nonis, M; Koettig, T; Vauthier, N; van Weelderen, R; Winkler, T

2015-01-01

The 27 km circumference LHC underground tunnel is a space in which the helium cooled LHC magnets are installed. The vacuum enclosures of the superconducting magnets are protected by over-pressure safety relief devices that open whenever cold helium escapes either from the magnet cold enclosure or from the helium supply headers, into this vacuum enclosure. A 3-m long no stay zone around these devices is defined based on scale model studies, protecting the personnel against cold burns or asphyxia caused by such a helium release event. Recently, several simulation studies have been carried out modelling the propagation of the helium/air mixture, resulting from the opening of such a safety device, along the tunnel. The released helium flows vary in the range between 1 kg/s and 0.1 kg/s. To validate these different simulation studies, real life mock-up tests have been performed inside the LHC tunnel, releasing helium flow rates of 1 kg/s, 0.3 kg/s and 0.1 kg/s. For each test, up to 1000 liters of liquid helium wer...

Performance of overlapped shield tunneling through an integrated physical model tests, numerical simulations and real-time field monitoring

Directory of Open Access Journals (Sweden)

Junlong Yang

2017-03-01

Full Text Available In this work, deformations and internal forces of an existing tunnel subjected to a closely overlapped shield tunneling are monitored and analyzed using a series of physical model experiments and numerical simulations. Effects of different excavation sequences and speeds are explicitly considered in the analysis. The results of the physical model experiments show that the bottom-up tunneling procedure is better than the top-down tunneling procedure. The incurred deformations and internal forces of the existing tunnel increase with the excavation speed and the range of influence areas also increase accordingly. For construction process control, real-time monitoring of the power tunnel is used. The monitoring processes feature full automation, adjustable frequency, real-time monitor and dynamic feedback, which are used to guide the construction to achieve micro-disturbance control. In accordance with the situation of crossing construction, a numerical study on the performance of power tunnel is carried out. Construction control measures are given for the undercrossing construction, which helps to accomplish the desired result and meet protection requirements of the existing tunnel structure. Finally, monitoring data and numerical results are compared, and the displacement and joint fracture change models in the power tunnel subject to the overlapped shield tunnel construction are analyzed. Keywords: Overlapped tunnel, Automatic monitoring, Micro-disturbance control

Wide bandgap, strain-balanced quantum well tunnel junctions on InP substrates

International Nuclear Information System (INIS)

Lumb, M. P.; Yakes, M. K.; Schmieder, K. J.; Affouda, C. A.; Walters, R. J.; González, M.; Bennett, M. F.; Herrera, M.; Delgado, F. J.; Molina, S. I.

2016-01-01

In this work, the electrical performance of strain-balanced quantum well tunnel junctions with varying designs is presented. Strain-balanced quantum well tunnel junctions comprising compressively strained InAlAs wells and tensile-strained InAlAs barriers were grown on InP substrates using solid-source molecular beam epitaxy. The use of InAlAs enables InP-based tunnel junction devices to be produced using wide bandgap layers, enabling high electrical performance with low absorption. The impact of well and barrier thickness on the electrical performance was investigated, in addition to the impact of Si and Be doping concentration. Finally, the impact of an InGaAs quantum well at the junction interface is presented, enabling a peak tunnel current density of 47.6 A/cm 2 to be realized.

Wide bandgap, strain-balanced quantum well tunnel junctions on InP substrates

Energy Technology Data Exchange (ETDEWEB)

Lumb, M. P. [The George Washington University, Washington, DC 20037 (United States); US Naval Research Laboratory, Washington, DC 20375 (United States); Yakes, M. K.; Schmieder, K. J.; Affouda, C. A.; Walters, R. J. [US Naval Research Laboratory, Washington, DC 20375 (United States); González, M.; Bennett, M. F. [Sotera Defense Solutions, Annapolis Junction, Maryland 20701 (United States); US Naval Research Laboratory, Washington, DC 20375 (United States); Herrera, M.; Delgado, F. J.; Molina, S. I. [University of Cádiz, 11510, Puerto Real, Cádiz (Spain)

2016-05-21

In this work, the electrical performance of strain-balanced quantum well tunnel junctions with varying designs is presented. Strain-balanced quantum well tunnel junctions comprising compressively strained InAlAs wells and tensile-strained InAlAs barriers were grown on InP substrates using solid-source molecular beam epitaxy. The use of InAlAs enables InP-based tunnel junction devices to be produced using wide bandgap layers, enabling high electrical performance with low absorption. The impact of well and barrier thickness on the electrical performance was investigated, in addition to the impact of Si and Be doping concentration. Finally, the impact of an InGaAs quantum well at the junction interface is presented, enabling a peak tunnel current density of 47.6 A/cm{sup 2} to be realized.

Final report on the Controlled Cold Helium Spill Test in the LHC tunnel at CERN

International Nuclear Information System (INIS)

Dufay-Chanat, L; Bremer, J; Casas-Cubillos, J; Koettig, T; Vauthier, N; Van Weelderen, R; Winkler, T; Chorowski, M; Grabowski, M; Jedrusyna, A; Lindell, G; Nonis, M

2015-01-01

The 27 km circumference LHC underground tunnel is a space in which the helium cooled LHC magnets are installed. The vacuum enclosures of the superconducting magnets are protected by over-pressure safety relief devices that open whenever cold helium escapes either from the magnet cold enclosure or from the helium supply headers, into this vacuum enclosure. A 3-m long no stay zone around these devices is defined based on scale model studies, protecting the personnel against cold burns or asphyxia caused by such a helium release event. Recently, several simulation studies have been carried out modelling the propagation of the helium/air mixture, resulting from the opening of such a safety device, along the tunnel. The released helium flows vary in the range between 1 kg/s and 0.1 kg/s. To validate these different simulation studies, real life mock-up tests have been performed inside the LHC tunnel, releasing helium flow rates of 1 kg/s, 0.3 kg/s and 0.1 kg/s. For each test, up to 1000 liters of liquid helium were released under standard operational tunnel conditions. The data recorded include oxygen concentration, temperature and flow speed measurements, and video footage used to assess qualitatively the visibility. These measurements have been made in the up- and downstream directions, with respect to the air ventilation flow, of the spill point.This paper presents the experimental set-up under which these release tests were made, the effects of these releases on the atmospheric tunnel condition as a function of the release flow rate. We discuss the modification to the personnel access conditions to the LHC tunnel that are presently implemented as a result of these tests. (paper)

Final report on the Controlled Cold Helium Spill Test in the LHC tunnel at CERN

Science.gov (United States)

Dufay-Chanat, L.; Bremer, J.; Casas-Cubillos, J.; Chorowski, M.; Grabowski, M.; Jedrusyna, A.; Lindell, G.; Nonis, M.; Koettig, T.; Vauthier, N.; van Weelderen, R.; Winkler, T.

2015-12-01

The 27 km circumference LHC underground tunnel is a space in which the helium cooled LHC magnets are installed. The vacuum enclosures of the superconducting magnets are protected by over-pressure safety relief devices that open whenever cold helium escapes either from the magnet cold enclosure or from the helium supply headers, into this vacuum enclosure. A 3-m long no stay zone around these devices is defined based on scale model studies, protecting the personnel against cold burns or asphyxia caused by such a helium release event. Recently, several simulation studies have been carried out modelling the propagation of the helium/air mixture, resulting from the opening of such a safety device, along the tunnel. The released helium flows vary in the range between 1 kg/s and 0.1 kg/s. To validate these different simulation studies, real life mock-up tests have been performed inside the LHC tunnel, releasing helium flow rates of 1 kg/s, 0.3 kg/s and 0.1 kg/s. For each test, up to 1000 liters of liquid helium were released under standard operational tunnel conditions. The data recorded include oxygen concentration, temperature and flow speed measurements, and video footage used to assess qualitatively the visibility. These measurements have been made in the up- and downstream directions, with respect to the air ventilation flow, of the spill point. This paper presents the experimental set-up under which these release tests were made, the effects of these releases on the atmospheric tunnel condition as a function of the release flow rate. We discuss the modification to the personnel access conditions to the LHC tunnel that are presently implemented as a result of these tests.

Restoring proximal caries lesions conservatively with tunnel restorations

Directory of Open Access Journals (Sweden)

Chu CH

2013-07-01

Full Text Available Chun-Hung Chu1, May L Mei,1 Chloe Cheung,1 Romesh P Nalliah2 1Faculty of Dentistry, The University of Hong Kong, Hong Kong, People's Republic of China; 2Department of Restorative Dentistry and Biomaterials Sciences, Harvard School of Dental Medicine, Boston, MA, USA Abstract: The tunnel restoration has been suggested as a conservative alternative to the conventional box preparation for treating proximal caries. The main advantage of tunnel restoration over the conventional box or slot preparation includes being more conservative and increasing tooth integrity and strength by preserving the marginal ridge. However, tunnel restoration is technique-sensitive and can be particularly challenging for inexperienced restorative dentists. Recent advances in technology, such as the contemporary design of dental handpieces with advanced light-emitting diode (LED and handheld comfort, offer operative dentists better vision, illumination, and maneuverability. The use of magnifying loupes also enhances the visibility of the preparation. The advent of digital radiographic imaging has improved dental imaging and reduced radiation. The new generation of restorative materials has improved mechanical properties. Tunnel restoration can be an option to restore proximal caries if the dentist performs proper case selection and pays attention to the details of the restorative procedures. This paper describes the clinical technique of tunnel restoration and reviews the studies of tunnel restorations. Keywords: operative, practice, tunnel preparation, composite, amalgam, glass ionomer

Low band-to-band tunnelling and gate tunnelling current in novel nanoscale double-gate architecture: simulations and investigation

Energy Technology Data Exchange (ETDEWEB)

Datta, Deepanjan [Department of Electrical and Computer Engineering, Purdue University, West Lafayette, IN 47906 (United States); Ganguly, Samiran [Department of Electronics Engineering, Indian School of Mines, Dhanbad-826004 (India); Dasgupta, S [Department of Electronics and Computer Engineering, Indian Institute of Technology, Roorkee-247667 (India)

2007-05-30

Large band-to-band tunnelling (BTBT) and gate leakage current can limit scalability of nanoscale devices. In this paper, we have proposed a novel nanoscale parallel connected heteromaterial double gate (PCHEM-DG) architecture with triple metal gate which significantly suppress BTBT leakage, making it efficient for low power design in the sub-10 nm regime. We have also proposed a triple gate device with p{sup +} poly-n{sup +} poly-p{sup +} poly gate which has substantially low gate leakage over symmetric DG MOSFET. Simulations are performed using a 2D Poisson-Schroedinger simulator and verified with a 2D device simulator ATLAS. We conclude that, due to intrinsic body doping, negligible gate leakage, suppressed BTBT over symmetric DG devices, metal gate (MG) PCHEM-DG MOSFET is efficient for low power circuit design in the nanometre regime.

Lithography for enabling advances in integrated circuits and devices.

Science.gov (United States)

Garner, C Michael

2012-08-28

Because the transistor was fabricated in volume, lithography has enabled the increase in density of devices and integrated circuits. With the invention of the integrated circuit, lithography enabled the integration of higher densities of field-effect transistors through evolutionary applications of optical lithography. In 1994, the semiconductor industry determined that continuing the increase in density transistors was increasingly difficult and required coordinated development of lithography and process capabilities. It established the US National Technology Roadmap for Semiconductors and this was expanded in 1999 to the International Technology Roadmap for Semiconductors to align multiple industries to provide the complex capabilities to continue increasing the density of integrated circuits to nanometre scales. Since the 1960s, lithography has become increasingly complex with the evolution from contact printers, to steppers, pattern reduction technology at i-line, 248 nm and 193 nm wavelengths, which required dramatic improvements of mask-making technology, photolithography printing and alignment capabilities and photoresist capabilities. At the same time, pattern transfer has evolved from wet etching of features, to plasma etch and more complex etching capabilities to fabricate features that are currently 32 nm in high-volume production. To continue increasing the density of devices and interconnects, new pattern transfer technologies will be needed with options for the future including extreme ultraviolet lithography, imprint technology and directed self-assembly. While complementary metal oxide semiconductors will continue to be extended for many years, these advanced pattern transfer technologies may enable development of novel memory and logic technologies based on different physical phenomena in the future to enhance and extend information processing.

Integrated visualization of simulation results and experimental devices in virtual-reality space

International Nuclear Information System (INIS)

Ohtani, Hiroaki; Ishiguro, Seiji; Shohji, Mamoru; Kageyama, Akira; Tamura, Yuichi

2011-01-01

We succeeded in integrating the visualization of both simulation results and experimental device data in virtual-reality (VR) space using CAVE system. Simulation results are shown using Virtual LHD software, which can show magnetic field line, particle trajectory, and isosurface of plasma pressure of the Large Helical Device (LHD) based on data from the magnetohydrodynamics equilibrium simulation. A three-dimensional mouse, or wand, determines the initial position and pitch angle of a drift particle or the starting point of a magnetic field line, interactively in the VR space. The trajectory of a particle and the stream-line of magnetic field are calculated using the Runge-Kutta-Huta integration method on the basis of the results obtained after pointing the initial condition. The LHD vessel is objectively visualized based on CAD-data. By using these results and data, the simulated LHD plasma can be interactively drawn in the objective description of the LHD experimental vessel. Through this integrated visualization, it is possible to grasp the three-dimensional relationship of the positions between the device and plasma in the VR space, opening a new path in contribution to future research. (author)

Controlling spin-dependent tunneling by bandgap tuning in epitaxial rocksalt MgZnO films.

Science.gov (United States)

Li, D L; Ma, Q L; Wang, S G; Ward, R C C; Hesjedal, T; Zhang, X-G; Kohn, A; Amsellem, E; Yang, G; Liu, J L; Jiang, J; Wei, H X; Han, X F

2014-12-02

Widespread application of magnetic tunnel junctions (MTJs) for information storage has so far been limited by the complicated interplay between tunnel magnetoresistance (TMR) ratio and the product of resistance and junction area (RA). An intricate connection exists between TMR ratio, RA value and the bandgap and crystal structure of the barrier, a connection that must be unravelled to optimise device performance and enable further applications to be developed. Here, we demonstrate a novel method to tailor the bandgap of an ultrathin, epitaxial Zn-doped MgO tunnel barrier with rocksalt structure. This structure is attractive due to its good Δ1 spin filtering effect, and we show that MTJs based on tunable MgZnO barriers allow effective balancing of TMR ratio and RA value. In this way spin-dependent transport properties can be controlled, a key challenge for the development of spintronic devices.

Measurement of mesoscopic Si:P delta-doped devices fabricated by rapid STM hydrogen depassivation lithography via field-emission

Science.gov (United States)

Rudolph, M.; Carr, S. M.; Subramania, G.; Ten Eyck, G.; Dominguez, J.; Lilly, M. P.; Carroll, M. S.; Bussmann, E.

2014-03-01

Recently, a method to fabricate nanoelectronic and quantum devices has been developed that utilizes scanning tunneling microscopy (STM) to place dopants (P) into Si with deterministic atomic-precision. Dopant placement is achieved via STM hydrogen depassivation lithography (HDL). Typically HDL is performed in a low-voltage tunneling mode where electrons desorb one H at a time, which requires extremely slow scan rates. Here, we introduce a high-voltage field-emission HDL, increasing patterning scan rate by an order of magnitude. Using the field-emission mode, we fabricated several HDL-patterned Si:P delta-doped devices, including a microscale multi-terminal Hall Effect device and a nanoscale quantum point contact. Low temperature transport measurements of the Hall device reveal a dopant density of 1014 cm-2, resistance of 2 k Ω/square, and mobility of 30 cm2/Vs. The quantum point contact showed a blockaded voltage range of 80 mV, comparable to other similar devices patterned using conventional HDL. This work was performed, in part, at the Center for Integrated Nanotechnologies, a U.S. DOE, Office of Basic Energy Sciences user facility. The work was supported by the Sandia National Laboratories Directed Research and Development Program. Sandia National Laboratories is a multi-program laboratory operated by Sandia Corporation, a Lockheed-Martin Company, for the U. S. Department of Energy under Contract No. DE-AC04-94AL85000.

Optical device terahertz integration in a two-dimensional-three-dimensional heterostructure.

Science.gov (United States)

Feng, Zhifang; Lin, Jie; Feng, Shuai

2018-01-10

The transmission properties of an off-planar integrated circuit including two wavelength division demultiplexers are designed, simulated, and analyzed in detail by the finite-difference time-domain method. The results show that the wavelength selection for different ports (0.404[c/a] at B 2 port, 0.389[c/a] at B 3 port, and 0.394[c/a] at B 4 port) can be realized by adjusting the parameters. It is especially important that the off-planar integration between two complex devices is also realized. These simulated results give valuable promotions in the all-optical integrated circuit, especially in compact integration.

Electron tunnelling through single azurin molecules can be on/off switched by voltage pulses

Energy Technology Data Exchange (ETDEWEB)

Baldacchini, Chiara [Biophysics and Nanoscience Centre, DEB-CNISM, Università della Tuscia, I-01100 Viterbo (Italy); Institute of Agro-Environmental and Forest Biology, CNR, I-05010 Porano (Italy); Kumar, Vivek; Bizzarri, Anna Rita; Cannistraro, Salvatore, E-mail: cannistr@unitus.it [Biophysics and Nanoscience Centre, DEB-CNISM, Università della Tuscia, I-01100 Viterbo (Italy)

2015-05-04

Redox metalloproteins are emerging as promising candidates for future bio-optoelectronic and nano-biomemory devices, and the control of their electron transfer properties through external signals is still a crucial task. Here, we show that a reversible on/off switching of the electron current tunnelling through a single protein can be achieved in azurin protein molecules adsorbed on gold surfaces, by applying appropriate voltage pulses through a scanning tunnelling microscope tip. The observed changes in the hybrid system tunnelling properties are discussed in terms of long-sustained charging of the protein milieu.

ON current enhancement of nanowire Schottky barrier tunnel field effect transistors

Science.gov (United States)

Takei, Kohei; Hashimoto, Shuichiro; Sun, Jing; Zhang, Xu; Asada, Shuhei; Xu, Taiyu; Matsukawa, Takashi; Masahara, Meishoku; Watanabe, Takanobu

2016-04-01

Silicon nanowire Schottky barrier tunnel field effect transistors (NW-SBTFETs) are promising structures for high performance devices. In this study, we fabricated NW-SBTFETs to investigate the effect of nanowire structure on the device characteristics. The NW-SBTFETs were operated with a backgate bias, and the experimental results demonstrate that the ON current density is enhanced by narrowing the width of the nanowire. We confirmed using the Fowler-Nordheim plot that the drain current in the ON state mainly comprises the quantum tunneling component through the Schottky barrier. Comparison with a technology computer aided design (TCAD) simulation revealed that the enhancement is attributed to the electric field concentration at the corners of cross-section of the NW. The study findings suggest an effective approach to securing the ON current by Schottky barrier width modulation.

Supporting Command and Control (C2) of an Embarked Commander: Tunneling SIPRNet Data Across an UNCLAS Wireless LAN

Science.gov (United States)

2011-09-01

that you did to help me through this process. Your efforts and guidance truly made this a success. To SPAWAR SCTD expert Stephanie Koontz , your...ty%20and%20Safety%20Services/05– 500%20Security%20Services/5510.36A.pdf [accessed June 19, 2011]. [28] S. Koontz . “Secret client tunneling...devices - KOV-26 talon user procedures.” Unpublished survey, SPAWAR, Point Loma, CA. [29] S. Koontz . “Secret client tunneling devices - KIV-54 user

Tunnel - history of

International Nuclear Information System (INIS)

1998-11-01

This book introduces history of tunnel in ancient times, the middle ages and modern times, survey of tunnel and classification of bedrock like environment survey of position, survey of the ground, design of tunnel on basic thing of the design, and design of tunnel of bedrock, analysis of stability of tunnel and application of the data, construction of tunnel like lattice girder and steel fiber reinforced shot crete, and maintenance control and repair of tunnel.

Tibial tunnel and pretibial cysts following ACL graft reconstruction: MR imaging diagnosis

Energy Technology Data Exchange (ETDEWEB)

Ghazikhanian, Varand [Brigham and Women' s Hospital, Musculoskeletal Imaging and Intervention, Department of Radiology, Boston, MA (United States); Beltran, Javier [Maimonides Medical Center, Brooklyn, NY (United States); Nikac, Violeta [Maimonides Medical Center, Department of Radiology, Brooklyn, NY (United States); Bencardino, Jenny T. [NYU Hospital for Joint Diseases, New York, NY (United States); Feldman, Marina

2012-11-15

Tunnel cyst formation is a rare complication after anterior cruciate ligament reconstruction, usually occurring 1-5 years post-operatively, which may occasionally be symptomatic. There are multiple proposed theories regarding the etiology of tunnel cysts. Theories include necrosis, foreign-body reaction, lack of complete graft osteo-integration, and intravasation of articular fluid. It is important to know if the tunnel cysts are communicating or not communicating with the joint, as surgical management may be different. Imaging characteristics on magnetic resonance images (MRI) include tibial tunnel widening, multilocular or unilocular cyst formation in the graft or tibial tunnel, with possible extension into the pretibial space, intercondylar notch, and/or popliteal fossa. The MR imaging differential diagnosis of tibial tunnel cysts includes infection, foreign-body granuloma, or tibial screw extrusion. Importantly, to the best of our knowledge, graft failure or instability has not been reported in association with tibial tunnel cysts. (orig.)

Integration of semiconductor and ceramic superconductor devices for microwave applications

International Nuclear Information System (INIS)

Klopman, B.B.G.; Weijers, H.W.; Gao, J.; Gerritsma, G.J.; Rogalla, H.

1991-01-01

Due to the very low-loss properties of ceramic superconductors high-performance microwave resonators and filters can be realized. The fact that these devices may be operated at liquid nitrogen temperature, facilitates the integration with semiconductor devices. Examples are bandpass amplifiers, microwave-operated SQUIDs combined with GaAs preamplifiers, detectors, and MOSFET low-frequency amplifiers. This paper discusses the design of such circuits on a single one inch alumina substrate using surface mount techniques. Furthermore data on circuits that have been realized in our laboratory will be presented

Growth of Si nanocrystals on alumina and integration in memory devices

Science.gov (United States)

Baron, T.; Fernandes, A.; Damlencourt, J. F.; De Salvo, B.; Martin, F.; Mazen, F.; Haukka, S.

2003-06-01

We present a detailed study of the growth of Si quantum dots (Si QDs) by low pressure chemical vapor deposition on alumina dielectric deposited by atomic layer deposition. The Si QDs density is very high, 1012 cm-2, for a mean diameter between 5 and 10 nm. Al2O3/Si QD stacks have been integrated in memory devices as granular floating gate. The devices demonstrate good charge storage and data retention characteristics.

Infrared thermal annealing device

International Nuclear Information System (INIS)

Gladys, M.J.; Clarke, I.; O'Connor, D.J.

2003-01-01

A device for annealing samples within an ultrahigh vacuum (UHV) scanning tunneling microscopy system was designed, constructed, and tested. The device is based on illuminating the sample with infrared radiation from outside the UHV chamber with a tungsten projector bulb. The apparatus uses an elliptical mirror to focus the beam through a sapphire viewport for low absorption. Experiments were conducted on clean Pd(100) and annealing temperatures in excess of 1000 K were easily reached

A Klein-tunneling transistor with ballistic graphene

Energy Technology Data Exchange (ETDEWEB)

Wilmart, Quentin; Fève, Gwendal; Berroir, Jean-Marc; Plaçais, Bernard [Laboratoire Pierre Aigrain, Ecole Normale Supérieure, CNRS (UMR 8551), Université P et M Curie, Université D Diderot, 24, rue Lhomond, 75231 Paris Cedex 05 (France); Berrada, Salim; Hung Nguyen, V; Dollfus, Philippe [Institute of Fundamental Electronics, Univ. Paris-Sud, CNRS, Orsay (France); Torrin, David [Département de Physique, Ecole Polytechnique, 91128 Palaiseau (France)

2014-06-15

Today, the availability of high mobility graphene up to room temperature makes ballistic transport in nanodevices achievable. In particular, p-n-p transistors in the ballistic regime give access to Klein tunneling physics and allow the realization of devices exploiting the optics-like behavior of Dirac Fermions (DFs) as in the Veselago lens or the Fabry–Pérot cavity. Here we propose a Klein tunneling transistor based on the geometrical optics of DFs. We consider the case of a prismatic active region delimited by a triangular gate, where total internal reflection may occur, which leads to the tunable suppression of transistor transmission. We calculate the transmission and the current by means of scattering theory and the finite bias properties using non-equilibrium Green's function (NEGF) simulation. (letter)

Typical Underwater Tunnels in the Mainland of China and Related Tunneling Technologies

Directory of Open Access Journals (Sweden)

Kairong Hong

2017-12-01

Full Text Available In the past decades, many underwater tunnels have been constructed in the mainland of China, and great progress has been made in related tunneling technologies. This paper presents the history and state of the art of underwater tunnels in the mainland of China in terms of shield-bored tunnels, drill-and-blast tunnels, and immersed tunnels. Typical underwater tunnels of these types in the mainland of China are described, along with innovative technologies regarding comprehensive geological prediction, grouting-based consolidation, the design and construction of large cross-sectional tunnels with shallow cover in weak strata, cutting tool replacement under limited drainage and reduced pressure conditions, the detection and treatment of boulders, the construction of underwater tunnels in areas with high seismic intensity, and the treatment of serious sedimentation in a foundation channel of immersed tunnels. Some suggestions are made regarding the three potential great strait-crossing tunnels—the Qiongzhou Strait-Crossing Tunnel, Bohai Strait-Crossing Tunnel, and Taiwan Strait-Crossing Tunnel—and issues related to these great strait-crossing tunnels that need further study are proposed. Keywords: Underwater tunnel, Strait-crossing tunnel, Shield-bored tunnel, Immersed tunnel, Drill and blast

Integrating bar-code devices with computerized MC and A systems

International Nuclear Information System (INIS)

Anderson, L.K.; Boor, M.G.; Hurford, J.M.

1998-01-01

Over the past seven years, Los Alamos National Laboratory developed several generations of computerized nuclear materials control and accountability (MC and A) systems for tracking and reporting the storage, movement, and management of nuclear materials at domestic and international facilities. During the same period, Oak Ridge National Laboratory was involved with automated data acquisition (ADA) equipment, including installation of numerous bar-code scanning stations at various facilities to serve as input devices to computerized systems. Bar-code readers, as well as other ADA devices, reduce input errors, provide faster input, and allow the capture of data in remote areas where workstations do not exist. Los Alamos National Laboratory and Oak Ridge National Laboratory teamed together to implement the integration of bar-code hardware technology with computerized MC and A systems. With the expertise of both sites, the two technologies were successfully merged with little difficulty. Bar-code input is now available with several functions of the MC and A systems: material movements within material balance areas (MBAs), material movements between MBAs, and physical inventory verification. This paper describes the various components required for the integration of these MC and A systems with the installed bar-code reader devices and the future directions for these technologies

Fabricating process of hollow out-of-plane Ni microneedle arrays and properties of the integrated microfluidic device

Science.gov (United States)

Zhu, Jun; Cao, Ying; Wang, Hong; Li, Yigui; Chen, Xiang; Chen, Di

2013-07-01

Although microfluidic devices that integrate microfluidic chips with hollow out-of-plane microneedle arrays have many advantages in transdermal drug delivery applications, difficulties exist in their fabrication due to the special three-dimensional structures of hollow out-of-plane microneedles. A new, cost-effective process for the fabrication of a hollow out-of-plane Ni microneedle array is presented. The integration of PDMS microchips with the Ni hollow microneedle array and the properties of microfluidic devices are also presented. The integrated microfluidic devices provide a new approach for transdermal drug delivery.

Analog/RF performance of two tunnel FETs with symmetric structures

Science.gov (United States)

Chen, Shupeng; Liu, Hongxia; Wang, Shulong; Li, Wei; Wang, Qianqiong

2017-11-01

In this paper, the radio frequency and analog performance of two tunnel field-effect transistors with symmetric structures are analyzed. The symmetric U-shape gate tunnel field-effect transistor (SUTFET) and symmetric tunnel field-effect transistor (STFET) are investigated by Silvaco Atlas simulation. The basic electrical properties and the parameters related to frequency and analog characteristics are analyzed. Due to the lower off-state leakage current, the STFET has better power consumption performance. The SUTFET obtains larger operating current (242 μA/μm), transconductance (490 μS/μm), output conductance (494 μS/μm), gain bandwidth product (3.2 GHz) and cut-off frequency (27.7 GHz). The simulation result of these two devices can be used as a guideline for their analog/RF applications.

Energy-Saving Tunnel Illumination System Based on LED's Intelligent Control

International Nuclear Information System (INIS)

Guo Shanshan; Wu Lan; Gu Hanting; Jiang Shuixiu

2011-01-01

At present there is a lot of electric energy wastage in tunnel illumination, whose design is based on the maximum brightness outside and the maximum vehicle speed all year round. LED's energy consumption is low, and the control of its brightness is simple and effective. It can be quickly adjusted between 0-100% of its maximum brightness, and will not affect the service life. Therefore, using LED as tunnel's illumination source, we can achieve a good energy saving effect. According to real-time data acquisition of vehicle speed, traffic flow and brightness outside the tunnel, the auto real-time control of tunnel illumination can be achieved. And the system regulated the LED luminance by means of combination of LED power module and intelligent control module. The tunnel information was detected by inspection equipments, which included luminometer, vehicle detector, and received by RTU(Remote Terminal Unit), then synchronously transmitted to PC. After data processing, RTU emitted the dimming signal to the LED driver to adjust the brightness of LED. Despite the relatively high cost of high-power LED lights, the enormous energy-saving effect and the well-behaved controllability is beyond compare to other lighting devices.

Thermionic emission and tunneling at carbon nanotube-organic semiconductor interface.

Science.gov (United States)

Sarker, Biddut K; Khondaker, Saiful I

2012-06-26

We study the charge carrier injection mechanism across the carbon nanotube (CNT)-organic semiconductor interface using a densely aligned carbon nanotube array as electrode and pentacene as organic semiconductor. The current density-voltage (J-V) characteristics measured at different temperatures show a transition from a thermal emission mechanism at high temperature (above 200 K) to a tunneling mechanism at low temperature (below 200 K). A barrier height of ∼0.16 eV is calculated from the thermal emission regime, which is much lower compared to the metal/pentacene devices. At low temperatures, the J-V curves exhibit a direct tunneling mechanism at low bias, corresponding to a trapezoidal barrier, while at high bias the mechanism is well described by Fowler-Nordheim tunneling, which corresponds to a triangular barrier. A transition from direct tunneling to Fowler-Nordheim tunneling further signifies a small injection barrier at the CNT/pentacene interface. Our results presented here are the first direct experimental evidence of low charge carrier injection barrier between CNT electrodes and an organic semiconductor and are a significant step forward in realizing the overall goal of using CNT electrodes in organic electronics.

Inter-ribbon tunneling in graphene: An atomistic Bardeen approach

Energy Technology Data Exchange (ETDEWEB)

Van de Put, Maarten L., E-mail: maarten.vandeput@uantwerpen.be; Magnus, Wim [Department of Physics, Universiteit Antwerpen, B-2020 Antwerpen (Belgium); imec, B-3001 Heverlee (Belgium); Vandenberghe, William G.; Fischetti, Massimo V. [Department of Material Science, University of Texas at Dallas, Texas 75080 (United States); Sorée, Bart [Department of Physics, Universiteit Antwerpen, B-2020 Antwerpen (Belgium); imec, B-3001 Heverlee (Belgium); Department of Electrical Engineering, KU Leuven, B-3001 Leuven (Belgium)

2016-06-07

A weakly coupled system of two crossed graphene nanoribbons exhibits direct tunneling due to the overlap of the wavefunctions of both ribbons. We apply the Bardeen transfer Hamiltonian formalism, using atomistic band structure calculations to account for the effect of the atomic structure on the tunneling process. The strong quantum-size confinement of the nanoribbons is mirrored by the one-dimensional character of the electronic structure, resulting in properties that differ significantly from the case of inter-layer tunneling, where tunneling occurs between bulk two-dimensional graphene sheets. The current-voltage characteristics of the inter-ribbon tunneling structures exhibit resonance, as well as stepwise increases in current. Both features are caused by the energetic alignment of one-dimensional peaks in the density-of-states of the ribbons. Resonant tunneling occurs if the sign of the curvature of the coupled energy bands is equal, whereas a step-like increase in the current occurs if the signs are opposite. Changing the doping modulates the onset-voltage of the effects as well as their magnitude. Doping through electrostatic gating makes these structures promising for application towards steep slope switching devices. Using the atomistic empirical pseudopotentials based Bardeen transfer Hamiltonian method, inter-ribbon tunneling can be studied for the whole range of two-dimensional materials, such as transition metal dichalcogenides. The effects of resonance and of step-like increases in the current we observe in graphene ribbons are also expected in ribbons made from these alternative two-dimensional materials, because these effects are manifestations of the one-dimensional character of the density-of-states.

Multiband corrections for the semi-classical simulation of interband tunneling in GaAs tunnel junctions

Science.gov (United States)

Louarn, K.; Claveau, Y.; Hapiuk, D.; Fontaine, C.; Arnoult, A.; Taliercio, T.; Licitra, C.; Piquemal, F.; Bounouh, A.; Cavassilas, N.; Almuneau, G.

2017-09-01

The aim of this study is to investigate the impact of multiband corrections on the current density in GaAs tunnel junctions (TJs) calculated with a refined yet simple semi-classical interband tunneling model (SCITM). The non-parabolicity of the considered bands and the spin-orbit effects are considered by using a recently revisited SCITM available in the literature. The model is confronted to experimental results from a series of molecular beam epitaxy grown GaAs TJs and to numerical results obtained with a full quantum model based on the non-equilibrium Green’s function formalism and a 6-band k.p Hamiltonian. We emphasize the importance of considering the non-parabolicity of the conduction band by two different measurements of the energy-dependent electron effective mass in N-doped GaAs. We also propose an innovative method to compute the non-uniform electric field in the TJ for the SCITM simulations, which is of prime importance for a successful operation of the model. We demonstrate that, when considering the multiband corrections and this new computation of the non-uniform electric field, the SCITM succeeds in predicting the electrical characteristics of GaAs TJs, and are also in agreement with the quantum model. Besides the fundamental study of the tunneling phenomenon in TJs, the main benefit of this SCITM is that it can be easily embedded into drift-diffusion software, which are the most widely-used simulation tools for electronic and opto-electronic devices such as multi-junction solar cells, tunnel field-effect transistors, or vertical-cavity surface-emitting lasers.

Direct, coherent and incoherent intermediate state tunneling and scanning tunnel microscopy (STM)

International Nuclear Information System (INIS)

Halbritter, J.

1997-01-01

Theory and experiment in tunneling are still qualitative in nature, which hold true also for the latest developments in direct-, resonant-, coherent- and incoherent-tunneling. Those tunnel processes have recently branched out of the field of ''solid state tunnel junctions'' into the fields of scanning tunnel microscopy (STM), single electron tunneling (SET) and semiconducting resonant tunnel structures (RTS). All these fields have promoted the understanding of tunneling in different ways reaching from the effect of coherence, of incoherence and of charging in tunneling, to spin flip or inelastic effects. STM allows not only the accurate measurements of the tunnel current and its voltage dependence but, more importantly, the easy quantification via the (quantum) tunnel channel conductance and the distance dependence. This new degree of freedom entering exponentially the tunnel current allows an unique identification of individual tunnel channels and their quantification. In STM measurements large tunnel currents are observed for large distances d > 1 nm explainable by intermediate state tunneling. Direct tunneling with its reduced tunnel time and reduced off-site Coulomb charging bridges distances below 1 nm, only. The effective charge transfer process with its larger off-site and on-site charging at intermediate states dominates tunnel transfer in STM, biology and chemistry over distances in the nm-range. Intermediates state tunneling becomes variable range hopping conduction for distances larger than d > 2 nm, for larger densities of intermediate states n 1 (ε) and for larger temperatures T or voltages U, still allowing high resolution imaging

Impact of edge states on device performance of phosphorene heterojunction tunneling field effect transistors.

Science.gov (United States)

Liu, Fei; Wang, Jian; Guo, Hong

2016-10-27

Black phosphorus (BP) tunneling field effect transistors (TFETs) using heterojunctions (Hes) are investigated by atomistic quantum transport simulations. It is observed that edge states have a great impact on the transport characteristics of BP He-TFETs, which results in the potential pinning effect and deterioration of gate control. However, the on-state current can be effectively enhanced by using hydrogen to saturate the edge dangling bonds in BP He-TFETs, by which means edge states are quenched. By extending layered BP with a smaller band gap to the channel region and modulating the BP thickness, the device performance of BP He-TFETs can be further optimized and can fulfil the requirements of the international technology road-map for semiconductors (ITRS) 2013 for low power applications. In 15 nm 3L-1L and 4L-1L BP He-TFETs along the armchair direction the on-state currents are over two times larger than the current required by ITRS 2013 and can reach above 10 3 μA μm -1 with the fixed off-state current of 10 pA μm -1 . It is also found that the ambipolar effect can be effectively suppressed in BP He-TFETs.

Process automation system for integration and operation of Large Volume Plasma Device

International Nuclear Information System (INIS)

Sugandhi, R.; Srivastava, P.K.; Sanyasi, A.K.; Srivastav, Prabhakar; Awasthi, L.M.; Mattoo, S.K.

2016-01-01

Highlights: • Analysis and design of process automation system for Large Volume Plasma Device (LVPD). • Data flow modeling for process model development. • Modbus based data communication and interfacing. • Interface software development for subsystem control in LabVIEW. - Abstract: Large Volume Plasma Device (LVPD) has been successfully contributing towards understanding of the plasma turbulence driven by Electron Temperature Gradient (ETG), considered as a major contributor for the plasma loss in the fusion devices. Large size of the device imposes certain difficulties in the operation, such as access of the diagnostics, manual control of subsystems and large number of signals monitoring etc. To achieve integrated operation of the machine, automation is essential for the enhanced performance and operational efficiency. Recently, the machine is undergoing major upgradation for the new physics experiments. The new operation and control system consists of following: (1) PXIe based fast data acquisition system for the equipped diagnostics; (2) Modbus based Process Automation System (PAS) for the subsystem controls and (3) Data Utilization System (DUS) for efficient storage, processing and retrieval of the acquired data. In the ongoing development, data flow model of the machine’s operation has been developed. As a proof of concept, following two subsystems have been successfully integrated: (1) Filament Power Supply (FPS) for the heating of W- filaments based plasma source and (2) Probe Positioning System (PPS) for control of 12 number of linear probe drives for a travel length of 100 cm. The process model of the vacuum production system has been prepared and validated against acquired pressure data. In the next upgrade, all the subsystems of the machine will be integrated in a systematic manner. The automation backbone is based on 4-wire multi-drop serial interface (RS485) using Modbus communication protocol. Software is developed on LabVIEW platform using

Process automation system for integration and operation of Large Volume Plasma Device

Energy Technology Data Exchange (ETDEWEB)

Sugandhi, R., E-mail: ritesh@ipr.res.in; Srivastava, P.K.; Sanyasi, A.K.; Srivastav, Prabhakar; Awasthi, L.M.; Mattoo, S.K.

2016-11-15

Highlights: • Analysis and design of process automation system for Large Volume Plasma Device (LVPD). • Data flow modeling for process model development. • Modbus based data communication and interfacing. • Interface software development for subsystem control in LabVIEW. - Abstract: Large Volume Plasma Device (LVPD) has been successfully contributing towards understanding of the plasma turbulence driven by Electron Temperature Gradient (ETG), considered as a major contributor for the plasma loss in the fusion devices. Large size of the device imposes certain difficulties in the operation, such as access of the diagnostics, manual control of subsystems and large number of signals monitoring etc. To achieve integrated operation of the machine, automation is essential for the enhanced performance and operational efficiency. Recently, the machine is undergoing major upgradation for the new physics experiments. The new operation and control system consists of following: (1) PXIe based fast data acquisition system for the equipped diagnostics; (2) Modbus based Process Automation System (PAS) for the subsystem controls and (3) Data Utilization System (DUS) for efficient storage, processing and retrieval of the acquired data. In the ongoing development, data flow model of the machine’s operation has been developed. As a proof of concept, following two subsystems have been successfully integrated: (1) Filament Power Supply (FPS) for the heating of W- filaments based plasma source and (2) Probe Positioning System (PPS) for control of 12 number of linear probe drives for a travel length of 100 cm. The process model of the vacuum production system has been prepared and validated against acquired pressure data. In the next upgrade, all the subsystems of the machine will be integrated in a systematic manner. The automation backbone is based on 4-wire multi-drop serial interface (RS485) using Modbus communication protocol. Software is developed on LabVIEW platform using

Self-field effects in window-type Josephson tunnel junctions

DEFF Research Database (Denmark)

Monaco, Roberto; Koshelets, Valery P; Mukhortova, Anna

2013-01-01

The properties of Josephson devices are strongly affected by geometrical effects such as those associated with the magnetic field induced by the bias current. The generally adopted analysis of Owen and Scalapino (1967 Phys. Rev. 164, 538) for the critical current, Ic, of an in-line Josephson tunnel...

Results of wind tunnel tests of an ASRM configured 0.03 scale Space Shuttle integrated vehicle model (47-OTS) in the AEDC 16-foot transonic wind tunnel, volume 2

Science.gov (United States)

Marroquin, J.; Lemoine, P.

1992-01-01

An experimental Aerodynamic and Aero-Acoustic loads data base was obtained at transonic Mach numbers for the Space Shuttle Launch Vehicle configured with the ASRM Solid Rocket Boosters as an increment to the current flight configuration (RSRB). These data were obtained during transonic wind tunnel tests (IA 613A) conducted in the Arnold Engineering Development Center 16-Foot transonic propulsion wind tunnel from March 27, 1991 through April 12, 1991. This test is the first of a series of two tests covering the Mach range from 0.6 to 3.5. Steady state surface static and fluctuating pressure distributions over the Orbiter, External Tank and Solid Rocket Boosters of the Shuttle Integrated Vehicle were measured. Total Orbiter forces, Wing forces and Elevon hinge moments were directly measured as well from force balances. Two configurations of Solid Rocket Boosters were tested, the Redesigned Solid Rocket Booster (RSRB) and the Advanced Solid Rocket Motor (ASRM). The effects of the position (i.e., top, bottom, top and bottom) of the Integrated Electronics Assembly (IEA) box, mounted on the SRB attach ring, were obtained on the ASRM configured model. These data were obtained with and without Solid Plume Simulators which, when used, matched as close as possible the flight derived pressures on the Orbiter and External Tank base. Data were obtained at Mach numbers ranging from 0.6 to 1.55 at a Unit Reynolds Number of 2.5 million per foot through model angles of attack from -8 to +4 degrees at sideslip angles of 0, +4 and -4 degrees.

Spectroscopy of bulk and few-layer superconducting NbSe2 with van der Waals tunnel junctions.

Science.gov (United States)

Dvir, T; Massee, F; Attias, L; Khodas, M; Aprili, M; Quay, C H L; Steinberg, H

2018-02-09

Tunnel junctions, an established platform for high resolution spectroscopy of superconductors, require defect-free insulating barriers; however, oxides, the most common barrier, can only grow on a limited selection of materials. We show that van der Waals tunnel barriers, fabricated by exfoliation and transfer of layered semiconductors, sustain stable currents with strong suppression of sub-gap tunneling. This allows us to measure the spectra of bulk (20 nm) and ultrathin (3- and 4-layer) NbSe 2 devices at 70 mK. These exhibit two distinct superconducting gaps, the larger of which decreases monotonically with thickness and critical temperature. The spectra are analyzed using a two-band model incorporating depairing. In the bulk, the smaller gap exhibits strong depairing in in-plane magnetic fields, consistent with high out-of-plane Fermi velocity. In the few-layer devices, the large gap exhibits negligible depairing, consistent with out-of-plane spin locking due to Ising spin-orbit coupling. In the 3-layer device, the large gap persists beyond the Pauli limit.

Spin-Polarized Tunneling through Chemical Vapor Deposited Multilayer Molybdenum Disulfide.

Science.gov (United States)

Dankert, André; Pashaei, Parham; Kamalakar, M Venkata; Gaur, Anand P S; Sahoo, Satyaprakash; Rungger, Ivan; Narayan, Awadhesh; Dolui, Kapildeb; Hoque, Md Anamul; Patel, Ram Shanker; de Jong, Michel P; Katiyar, Ram S; Sanvito, Stefano; Dash, Saroj P

2017-06-27

The two-dimensional (2D) semiconductor molybdenum disulfide (MoS 2 ) has attracted widespread attention for its extraordinary electrical-, optical-, spin-, and valley-related properties. Here, we report on spin-polarized tunneling through chemical vapor deposited multilayer MoS 2 (∼7 nm) at room temperature in a vertically fabricated spin-valve device. A tunnel magnetoresistance (TMR) of 0.5-2% has been observed, corresponding to spin polarization of 5-10% in the measured temperature range of 300-75 K. First-principles calculations for ideal junctions result in a TMR up to 8% and a spin polarization of 26%. The detailed measurements at different temperature, bias voltages, and density functional theory calculations provide information about spin transport mechanisms in vertical multilayer MoS 2 spin-valve devices. These findings form a platform for exploring spin functionalities in 2D semiconductors and understanding the basic phenomena that control their performance.

Efficient evaluation of atom tunneling combined with electronic structure calculations.

Science.gov (United States)

Ásgeirsson, Vilhjálmur; Arnaldsson, Andri; Jónsson, Hannes

2018-03-14

Methodology for finding optimal tunneling paths and evaluating tunneling rates for atomic rearrangements is described. First, an optimal JWKB tunneling path for a system with fixed energy is obtained using a line integral extension of the nudged elastic band method. Then, a calculation of the dynamics along the path is used to determine the temperature at which it corresponds to an optimal Feynman path for thermally activated tunneling (instanton) and a harmonic approximation is used to estimate the transition rate. The method is illustrated with calculations for a modified two-dimensional Müller-Brown surface but is efficient enough to be used in combination with electronic structure calculations of the energy and atomic forces in systems containing many atoms. An example is presented where tunneling is the dominant mechanism well above room temperature as an H 3 BNH 3 molecule dissociates to form H 2 . Also, a solid-state example is presented where density functional theory calculations of H atom tunneling in a Ta crystal give close agreement with experimental measurements on hydrogen diffusion over a wide range in temperature.

FY 1998 R and D project on industrial science technology; 1998 nendo ryoshi kino soshi no kenkyu kaihatsu seika hokokusho

Energy Technology Data Exchange (ETDEWEB)

NONE

1999-03-01

The R and D on quantum functional devices (QFDs) were conducted, and the FY 1998 results were summed up. In the comprehensive survey on QFDs, the following were carried out for the efficient R and D promotion: R and D progress state survey/problem extraction/analytical study, technical trend survey, overseas survey ordered from overseas supplier, common basement technology study, etc. In the R and D on technology for QFDs, integration of multivalued logical devices using tunneling control functional devices, integration of logical memory devices using quantum levels, integration of quantum band combination-type multi-functional devices, silicon insulating film tunnel memory devices, assembly quantum dot functional memory, quantum wave switching functional devices, integration of single electron logical devices, integration of CMOS combination-type single electron devices, etc. Moreover, in the development of the basement technology of single electron devices, technology to construct element devices using quantum functions, basement technology of single electron device integration devices, architecture of single electron device information processing circuit system, etc. (NEDO)

Micromagnetic Design of Spin Dependent Tunnel Junctions for Optimized Sensing Performance

National Research Council Canada - National Science Library

Tondra, Mark; Daughton, James M; Nordman, Catherine; Wang, Dexin; Taylor, John

1999-01-01

Pinned Spin Dependent Tunneling (SDT) devices have been fabricated into high sensitivity magnetic field sensors with many favorable properties including high sensitivity (̃ 10 umOe / Hz @ 1 Hz and ̃ 100 nOe / Hz @ > 10 kHz...

Enhanced Tunnel Spin Injection into Graphene using Chemical Vapor Deposited Hexagonal Boron Nitride

Science.gov (United States)

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

Design of double gate vertical tunnel field effect transistor using HDB and its performance estimation

Science.gov (United States)

Seema; Chauhan, Sudakar Singh

2018-05-01

In this paper, we demonstrate the double gate vertical tunnel field-effect transistor using homo/hetero dielectric buried oxide (HDB) to obtain the optimized device characteristics. In this concern, the existence of double gate, HDB and electrode work-function engineering enhances DC performance and Analog/RF performance. The use of electrostatic doping helps to achieve higher on-current owing to occurrence of higher tunneling generation rate of charge carriers at the source/epitaxial interface. Further, lightly doped drain region and high- k dielectric below channel and drain region are responsible to suppress the ambipolar current. Simulated results clarifies that proposed device have achieved the tremendous performance in terms of driving current capability, steeper subthreshold slope (SS), drain induced barrier lowering (DIBL), hot carrier effects (HCEs) and high frequency parameters for better device reliability.

Towards nanoscale magnetic memory elements : fabrication and properties of sub - 100 nm magnetic tunnel junctions

NARCIS (Netherlands)

Fabrie, C.G.C.H.M.

2008-01-01

The rapidly growing field of spintronics has recently attracted much attention. Spintronics is electronics in which the spin degree of freedom has been added to conventional chargebased electronic devices. A magnetic tunnel junction (MTJ) is an example of a spintronic device. MTJs consist of two

Reduction of conductance mismatch in Fe/Al2O3/MoS2 system by tunneling-barrier thickness control

Science.gov (United States)

Hayakawa, Naoki; Muneta, Iriya; Ohashi, Takumi; Matsuura, Kentaro; Shimizu, Jun’ichi; Kakushima, Kuniyuki; Tsutsui, Kazuo; Wakabayashi, Hitoshi

2018-04-01

Molybdenum disulfide (MoS2) among two-dimensional semiconductor films is promising for spintronic devices because it has a longer spin-relaxation time with contrasting spin splitting than silicon. However, it is difficult to fabricate integrated circuits by the widely used exfoliation method. Here, we investigate the contact characteristics in the Fe/Al2O3/sputtered-MoS2 system with various thicknesses of the Al2O3 film. Current density increases with increasing thickness up to 2.5 nm because of both thermally-assisted and direct tunneling currents. On the other hand, it decreases with increasing thickness over 2.5 nm limited by direct tunneling currents. These results suggest that the Schottky barrier width can be controlled by changing thicknesses of the Al2O3 film, as supported by calculations. The reduction of conductance mismatch with this technique can lead to highly efficient spin injection from iron into the MoS2 film.

Thermal management in MoS{sub 2} based integrated device using near-field radiation

Energy Technology Data Exchange (ETDEWEB)

Peng, Jiebin [Department of Physics, National University of Singapore, Singapore 117546 (Singapore); Zhang, Gang, E-mail: zhangg@ihpc.a-star.edu.sg [Institute of High Performance Computing, A*STAR, Singapore 138632 (Singapore); Li, Baowen [Department of Mechanical Engineering, University of Colorado, Boulder, Colorado 80309 (United States)

2015-09-28

Recently, wafer-scale growth of monolayer MoS{sub 2} films with spatial homogeneity is realized on SiO{sub 2} substrate. Together with the latest reported high mobility, MoS{sub 2} based integrated electronic devices are expected to be fabricated in the near future. Owing to the low lattice thermal conductivity in monolayer MoS{sub 2}, and the increased transistor density accompanied with the increased power density, heat dissipation will become a crucial issue for these integrated devices. In this letter, using the formalism of fluctuation electrodynamics, we explored the near-field radiative heat transfer from a monolayer MoS{sub 2} to graphene. We demonstrate that in resonance, the maximum heat transfer via near-field radiation between MoS{sub 2} and graphene can be ten times higher than the in-plane lattice thermal conduction for MoS{sub 2} sheet. Therefore, an efficient thermal management strategy for MoS{sub 2} integrated device is proposed: Graphene sheet is brought into close proximity, 10–20 nm from MoS{sub 2} device; heat energy transfer from MoS{sub 2} to graphene via near-field radiation; this amount of heat energy then be conducted to contact due to ultra-high lattice thermal conductivity of graphene. Our work sheds light for developing cooling strategy for nano devices constructing with low thermal conductivity materials.

An integrated semiconductor device enabling non-optical genome sequencing.

Science.gov (United States)

Rothberg, Jonathan M; Hinz, Wolfgang; Rearick, Todd M; Schultz, Jonathan; Mileski, William; Davey, Mel; Leamon, John H; Johnson, Kim; Milgrew, Mark J; Edwards, Matthew; Hoon, Jeremy; Simons, Jan F; Marran, David; Myers, Jason W; Davidson, John F; Branting, Annika; Nobile, John R; Puc, Bernard P; Light, David; Clark, Travis A; Huber, Martin; Branciforte, Jeffrey T; Stoner, Isaac B; Cawley, Simon E; Lyons, Michael; Fu, Yutao; Homer, Nils; Sedova, Marina; Miao, Xin; Reed, Brian; Sabina, Jeffrey; Feierstein, Erika; Schorn, Michelle; Alanjary, Mohammad; Dimalanta, Eileen; Dressman, Devin; Kasinskas, Rachel; Sokolsky, Tanya; Fidanza, Jacqueline A; Namsaraev, Eugeni; McKernan, Kevin J; Williams, Alan; Roth, G Thomas; Bustillo, James

2011-07-20

The seminal importance of DNA sequencing to the life sciences, biotechnology and medicine has driven the search for more scalable and lower-cost solutions. Here we describe a DNA sequencing technology in which scalable, low-cost semiconductor manufacturing techniques are used to make an integrated circuit able to directly perform non-optical DNA sequencing of genomes. Sequence data are obtained by directly sensing the ions produced by template-directed DNA polymerase synthesis using all-natural nucleotides on this massively parallel semiconductor-sensing device or ion chip. The ion chip contains ion-sensitive, field-effect transistor-based sensors in perfect register with 1.2 million wells, which provide confinement and allow parallel, simultaneous detection of independent sequencing reactions. Use of the most widely used technology for constructing integrated circuits, the complementary metal-oxide semiconductor (CMOS) process, allows for low-cost, large-scale production and scaling of the device to higher densities and larger array sizes. We show the performance of the system by sequencing three bacterial genomes, its robustness and scalability by producing ion chips with up to 10 times as many sensors and sequencing a human genome.

Integrated Lateral Flow Device for Flow Control with Blood Separation and Biosensing

Directory of Open Access Journals (Sweden)

Veronica Betancur

2017-12-01

Full Text Available Lateral flow devices are versatile and serve a wide variety of purposes, including medical, agricultural, environmental, and military applications. Yet, the most promising opportunities of these devices for diagnosis might reside in point-of-care (POC applications. Disposable paper-based lateral flow strips have been of particular interest, because they utilize low-cost materials and do not require expensive fabrication instruments. However, there are constraints on tuning flow rates and immunoassays functionalization in papers, as well as technical challenges in sensors’ integration and concentration units for low-abundant molecular detection. In the present work, we demonstrated an integrated lateral flow device that applied the capillary forces with functionalized polymer-based microfluidics as a strategy to realize a portable, simplified, and self-powered lateral flow device (LFD. The polydimethylsiloxane (PDMS surface was rendered hydrophilic via functionalization with different concentrations of Pluronic F127. Controlled flow is a key variable for immunoassay-based applications for providing enough time for protein binding to antibodies. The flow rate of the integrated LFD was regulated by the combination of multiple factors, including Pluronic F127 functionalized surface properties and surface treatments of microchannels, resistance of the integrated flow resistor, the dimensions of the microstructures and the spacing between them in the capillary pump, the contact angles, and viscosity of the fluids. Various plasma flow rates were regulated and achieved in the whole device. The LFD combined the ability to separate high quality plasma from human whole blood by using a highly asymmetric plasma separation membrane, and created controlled and steady fluid flow using capillary forces produced by the interfacial tensions. Biomarker immunoglobulin G (IgG detection from plasma was demonstrated with a graphene nanoelectronic sensor integrated

Giant magneto-resistance devices

CERN Document Server

Hirota, Eiichi; Inomata, Koichiro

2002-01-01

This book deals with the application of giant magneto-resistance (GMR) effects to electronic devices. It will appeal to engineers and graduate students in the fields of electronic devices and materials. The main subjects are magnetic sensors with high resolution and magnetic read heads with high sensitivity, required for hard-disk drives with recording densities of several gigabytes. Another important subject is novel magnetic random-access memories (MRAM) with non-volatile non-destructive and radiation-resistant characteristics. Other topics include future GMR devices based on bipolar spin transistors, spin field-effect transistors (FETs) and double-tunnel junctions.

Fabrication of coupled graphene–nanotube quantum devices

International Nuclear Information System (INIS)

Engels, S; Weber, P; Terrés, B; Dauber, J; Volk, C; Wichmann, U; Stampfer, C; Meyer, C; Trellenkamp, S

2013-01-01

We report on the fabrication and characterization of all-carbon hybrid quantum devices based on graphene and single-walled carbon nanotubes. We discuss both carbon nanotube quantum dot devices with graphene charge detectors and nanotube quantum dots with graphene leads. The devices are fabricated by chemical vapor deposition growth of carbon nanotubes and subsequent structuring of mechanically exfoliated graphene. We study the detection of individual charging events in the carbon nanotube quantum dot by a nearby graphene nanoribbon and show that they lead to changes of up to 20% of the conductance maxima in the graphene nanoribbon, acting as a well performing charge detector. Moreover, we discuss an electrically coupled graphene–nanotube junction, which exhibits a tunneling barrier with tunneling rates in the low GHz regime. This allows us to observe Coulomb blockade on a carbon nanotube quantum dot with graphene source and drain leads. (paper)

Closed-loop model: An optimization of integrated thin-film magnetic devices

Energy Technology Data Exchange (ETDEWEB)

El-Ghazaly, Amal, E-mail: amale@stanford.edu [Electrical Engineering, Stanford University, Stanford, CA 94305 (United States); Sato, Noriyuki [Electrical Engineering, Stanford University, Stanford, CA 94305 (United States); White, Robert M. [Materials Science and Engineering, Stanford University, Stanford, CA 94305 (United States); Wang, Shan X. [Electrical Engineering, Stanford University, Stanford, CA 94305 (United States); Materials Science and Engineering, Stanford University, Stanford, CA 94305 (United States)

2017-06-15

Highlights: • An analytical model for inductance of thin-film magnetic devices was developed. • Different device topologies and magnetic permeabilities were addressed. • Inductance of various topologies were calculated and compared with simulation. • The model predicts simulated values with excellent accuracy. - Abstract: A generic analytical model has been developed to fully describe the flux closure through magnetic inductors. The model was applied to multiple device topologies including solenoidal single return path and dual return path inductors as well as spiral magnetic inductors for a variety of permeabilities and dimensions. The calculated inductance values from the analytical model were compared with simulated results for each of the analyzed device topologies and found to agree within 0.1 nH for the range of typical thin-film magnetic permeabilities (∼10{sup 2} to 10{sup 3}). Furthermore, the model can be used to evaluate behavior in other integrated or discrete magnetic devices with either non-isotropic or isotropic permeability and used to produce more efficient device designs in the future.

Medical Device Integrated Vital Signs Monitoring Application with Real-Time Clinical Decision Support.

Science.gov (United States)

Moqeem, Aasia; Baig, Mirza; Gholamhosseini, Hamid; Mirza, Farhaan; Lindén, Maria

2018-01-01

This research involves the design and development of a novel Android smartphone application for real-time vital signs monitoring and decision support. The proposed application integrates market available, wireless and Bluetooth connected medical devices for collecting vital signs. The medical device data collected by the app includes heart rate, oxygen saturation and electrocardiograph (ECG). The collated data is streamed/displayed on the smartphone in real-time. This application was designed by adopting six screens approach (6S) mobile development framework and focused on user-centered approach and considered clinicians-as-a-user. The clinical engagement, consultations, feedback and usability of the application in the everyday practices were considered critical from the initial phase of the design and development. Furthermore, the proposed application is capable to deliver rich clinical decision support in real-time using the integrated medical device data.

The Marketing Plan: An Integrative Device for Teaching Marketing Management.

Science.gov (United States)

Berdine, W. R.; Petersen, James C.

1980-01-01

The importance of the marketing plan is stressed as an integrative device for teaching marketing management, and a structure is presented to assist students in designing a marketing plan. Components of this plan include marketing objectives, targeting market and buying motives, external environment and competition, product, price, and promotion.…

Metallic spintronic devices

CERN Document Server

Wang, Xiaobin

2014-01-01

Metallic Spintronic Devices provides a balanced view of the present state of the art of metallic spintronic devices, addressing both mainstream and emerging applications from magnetic tunneling junction sensors and spin torque oscillators to spin torque memory and logic. Featuring contributions from well-known and respected industrial and academic experts, this cutting-edge work not only presents the latest research and developments but also: Describes spintronic applications in current and future magnetic recording devicesDiscusses spin-transfer torque magnetoresistive random-access memory (STT-MRAM) device architectures and modelingExplores prospects of STT-MRAM scaling, such as detailed multilevel cell structure analysisInvestigates spintronic device write and read optimization in light of spintronic memristive effectsConsiders spintronic research directions based on yttrium iron garnet thin films, including spin pumping, magnetic proximity, spin hall, and spin Seebeck effectsProposes unique solutions for ...

The MMI Device Ontology: Enabling Sensor Integration

Science.gov (United States)

Rueda, C.; Galbraith, N.; Morris, R. A.; Bermudez, L. E.; Graybeal, J.; Arko, R. A.; Mmi Device Ontology Working Group

2010-12-01

The Marine Metadata Interoperability (MMI) project has developed an ontology for devices to describe sensors and sensor networks. This ontology is implemented in the W3C Web Ontology Language (OWL) and provides an extensible conceptual model and controlled vocabularies for describing heterogeneous instrument types, with different data characteristics, and their attributes. It can help users populate metadata records for sensors; associate devices with their platforms, deployments, measurement capabilities and restrictions; aid in discovery of sensor data, both historic and real-time; and improve the interoperability of observational oceanographic data sets. We developed the MMI Device Ontology following a community-based approach. By building on and integrating other models and ontologies from related disciplines, we sought to facilitate semantic interoperability while avoiding duplication. Key concepts and insights from various communities, including the Open Geospatial Consortium (eg., SensorML and Observations and Measurements specifications), Semantic Web for Earth and Environmental Terminology (SWEET), and W3C Semantic Sensor Network Incubator Group, have significantly enriched the development of the ontology. Individuals ranging from instrument designers, science data producers and consumers to ontology specialists and other technologists contributed to the work. Applications of the MMI Device Ontology are underway for several community use cases. These include vessel-mounted multibeam mapping sonars for the Rolling Deck to Repository (R2R) program and description of diverse instruments on deepwater Ocean Reference Stations for the OceanSITES program. These trials involve creation of records completely describing instruments, either by individual instances or by manufacturer and model. Individual terms in the MMI Device Ontology can be referenced with their corresponding Uniform Resource Identifiers (URIs) in sensor-related metadata specifications (e

Nanoelectromechanical switch operating by tunneling of an entire C-60 molecule

DEFF Research Database (Denmark)

Danilov, Andrey V.; Hedegård, Per; Golubev, Dimitrii S.

2008-01-01

(i) the relative contribution of tunneling, current induced heating and thermal fluctuations to the switching mechanism, (ii) the voltage dependent energy barrier (similar to 100-200 meV) separating the two states of the switch and (iii) the switching attempt frequency, omega(0) corresponding to a 2......We present a solid state single molecule electronic device where switching between two states with different conductance happens predominantly by tunneling of an entire C-60 molecule. This conclusion is based on a novel statistical analysis of similar to 10(5) switching events. The analysis yields...

A Klein-tunneling transistor with ballistic graphene

International Nuclear Information System (INIS)

Wilmart, Quentin; Fève, Gwendal; Berroir, Jean-Marc; Plaçais, Bernard; Berrada, Salim; Hung Nguyen, V; Dollfus, Philippe; Torrin, David

2014-01-01

Today, the availability of high mobility graphene up to room temperature makes ballistic transport in nanodevices achievable. In particular, p-n-p transistors in the ballistic regime give access to Klein tunneling physics and allow the realization of devices exploiting the optics-like behavior of Dirac Fermions (DFs) as in the Veselago lens or the Fabry–Pérot cavity. Here we propose a Klein tunneling transistor based on the geometrical optics of DFs. We consider the case of a prismatic active region delimited by a triangular gate, where total internal reflection may occur, which leads to the tunable suppression of transistor transmission. We calculate the transmission and the current by means of scattering theory and the finite bias properties using non-equilibrium Green's function (NEGF) simulation. (letter)

Quantum Tunneling and Chaos in Classical Scale Walkers

Science.gov (United States)

Su, Jenny; Dijksman, Joshua; Ward, Jeremy; Behringer, Robert

2014-03-01

We study the behavior of `walkers' small droplets bouncing on a fluid layer vibrated at amplitudes just below the onset of Faraday instability. It was shown recently that despite their macroscopic size, the droplet dynamics are stochastic in nature and reminiscent of the dual particle-wave dynamics in the realm of quantum mechanics (Couder PRL 2006). We use these walkers to study how chaos, which is macroscopically unpredictable, will manifest in a quantum setting. Pecora showed in 2011 that tunneling for particles that have a chaotic ground state is different from tunneling for particles with a regular ground state (PRE 2011). In the experiment we gather data that illustrates the particle trajectory and tunneling behavior as particles transition across the barrier in the double well system with both integrable and chaotic shapes.

Haptic-STM: a human-in-the-loop interface to a scanning tunneling microscope.

Science.gov (United States)

Perdigão, Luís M A; Saywell, Alex

2011-07-01

The operation of a haptic device interfaced with a scanning tunneling microscope (STM) is presented here. The user moves the STM tip in three dimensions by means of a stylus attached to the haptic instrument. The tunneling current measured by the STM is converted to a vertical force, applied to the stylus and felt by the user, with the user being incorporated into the feedback loop that controls the tip-surface distance. A haptic-STM interface of this nature allows the user to feel atomic features on the surface and facilitates the tactile manipulation of the adsorbate/substrate system. The operation of this device is demonstrated via the room temperature STM imaging of C(60) molecules adsorbed on an Au(111) surface in ultra-high vacuum.

Highway tunnel safety; Le gallerie infrastrutturali e la loro sicurezza

Energy Technology Data Exchange (ETDEWEB)

Sacripanti, A [ENEA, Divisione Robotica Informatica Avanzata, Rome (Italy)

2001-04-01

Guaranteeing an acceptable level of fire safety in tunnels requires the targeted and integrated use of innovative technologies and systems. However, their deployment to improve safety against a variable risk like fire must be based on a risk analysis capable of developing a dynamic vision of the tunnel. [Italian] Per assicurare un livello di sicurezza accettabile nei tunnel, in caso di incendio e' necessario l'uso mirato ed integrato di tecnologie e sistemi innovativi. Alla base, pero', ci deve essere una analisi di rischio in grado di sviluppare una visione dinamica della galleria, per migliorarne la sicurezza a fronte di un rischio variabile nel tempo.

Highway tunnel safety; Le gallerie infrastrutturali e la loro sicurezza

Energy Technology Data Exchange (ETDEWEB)

Sacripanti, A. [ENEA, Divisione Robotica Informatica Avanzata, Rome (Italy)

2001-04-01

Guaranteeing an acceptable level of fire safety in tunnels requires the targeted and integrated use of innovative technologies and systems. However, their deployment to improve safety against a variable risk like fire must be based on a risk analysis capable of developing a dynamic vision of the tunnel. [Italian] Per assicurare un livello di sicurezza accettabile nei tunnel, in caso di incendio e' necessario l'uso mirato ed integrato di tecnologie e sistemi innovativi. Alla base, pero', ci deve essere una analisi di rischio in grado di sviluppare una visione dinamica della galleria, per migliorarne la sicurezza a fronte di un rischio variabile nel tempo.

Tunnelling anomalous and planar Hall effects (Conference Presentation)

Science.gov (United States)

Matos-Abiague, Alex; Scharf, Benedikt; Han, Jong E.; Hankiewicz, Ewelina M.; Zutic, Igor

2016-10-01

We theoretically show how the interplay between spin-orbit coupling (SOC) and magnetism can result in a finite tunneling Hall conductance, transverse to the applied bias. For two-dimensional tunnel junctions with a ferromagnetic lead and magnetization perpendicular to the current flow, the detected anomalous Hall voltage can be used to extract information not only about the spin polarization but also about the strength of the interfacial SOC. In contrast, a tunneling current across a ferromagnetic barrier on the surface of a three-dimensional topological insulator (TI) can induce a planar Hall response even when the magnetization is oriented along the current flow[1]. The tunneling nature of the states contributing to the planar Hall conductance can be switched from the ordinary to the Klein regimes by the electrostatic control of the barrier strength. This allows for an enhancement of the transverse response and a giant Hall angle, with the tunneling planar Hall conductance exceeding the longitudinal component. Despite the simplicity of a single ferromagnetic region, the TI/ferromagnet system exhibits a variety of functionalities. In addition to a spin-valve operation for magnetic sensing and storing information, positive, negative, and negative differential conductances can be tuned by properly adjusting the barrier potential and/or varying the magnetization direction. Such different resistive behaviors in the same system are attractive for potential applications in reconfigurable spintronic devices. [1] B. Scharf, A. Matos-Abiague, J. E. Han, E. M. Hankiewicz, and I. Zutic, arXiv:1601.01009 (2016).

Integrated Microfibre Device for Refractive Index and Temperature Sensing

Directory of Open Access Journals (Sweden)

Sulaiman W. Harun

2012-08-01

Full Text Available A microfibre device integrating a microfibre knot resonator in a Sagnac loop reflector is proposed for refractive index and temperature sensing. The reflective configuration of this optical structure offers the advantages of simple fabrication and ease of sensing. To achieve a balance between responsiveness and robustness, the entire microfibre structure is embedded in low index Teflon, except for the 0.5–2 mm diameter microfibre knot resonator sensing region. The proposed sensor has exhibited a linear spectral response with temperature and refractive index. A small change in free spectral range is observed when the microfibre device experiences a large refractive index change in the surrounding medium. The change is found to be in agreement with calculated results based on dispersion relationships.

Thin-film luminescent concentrators for integrated devices: a cookbook.

Science.gov (United States)

Evenson, S A; Rawicz, A H

1995-11-01

A luminescent concentrator (LC) is a nonimaging optical device used for collecting light energy. As a result of its unique properties, a LC also offers the possibility of separating different portions of the spectrum and concentrating them at the same time. Hence, LC's can be applied to a whole range of problems requiring the collection, manipulation, and distribution or measurement of light. Further-more, as described in our previous research, thin-film LC elements can be deposited directly over sensor and processing electronics in the form of integrated LC devices. As an aid to further research, the materials and technology required to fabricate these thin-film LC elements through the use of an ultraviolet-curable photopolymer are documented in detail.

Monitoring pilot projects on bored tunnelling : The Second Heinenoord Tunnel and the Botlek Rail Tunnel

NARCIS (Netherlands)

Bakker, K.J.; De Boer, F.; Admiraal, J.B.M.; Van Jaarsveld, E.P.

1999-01-01

Two pilot projects for bored tunnelling in soft soil have been undertaken in the Netherlands. The monitoring was commissioned under the authority of the Centre for Underground Construction (COB). A description of the research related to the Second Heinenoord Tunnel and the Botlek Rail Tunnel will be

InP monolithically integrated label swapper device for spectral amplitude coded optical packet networks

NARCIS (Netherlands)

Muñoz, P.; García-Olcina, R.; Doménech, J.D.; Rius, M.; Sancho, J.C.; Capmany, J.; Chen, L.R.; Habib, C.; Leijtens, X.J.M.; Vries, de T.; Heck, M.J.R.; Augustin, L.M.; Nötzel, R.; Robbins, D.J.

2010-01-01

In this paper a label swapping device, for spectral amplitude coded optical packet networks, fully integrated using InP technology is presented. Compared to previous demonstrations using discrete component assembly, the device footprint is reduced by a factor of 105 and the operation speed is

A design approach for integrating thermoelectric devices using topology optimization

International Nuclear Information System (INIS)

Soprani, S.; Haertel, J.H.K.; Lazarov, B.S.; Sigmund, O.; Engelbrecht, K.

2016-01-01

Highlights: • The integration of a thermoelectric (TE) cooler into a robotic tool is optimized. • Topology optimization is suggested as design tool for TE integrated systems. • A 3D optimization technique using temperature dependent TE properties is presented. • The sensitivity of the optimization process to the boundary conditions is studied. • A working prototype is constructed and compared to the model results. - Abstract: Efficient operation of thermoelectric devices strongly relies on the thermal integration into the energy conversion system in which they operate. Effective thermal integration reduces the temperature differences between the thermoelectric module and its thermal reservoirs, allowing the system to operate more efficiently. This work proposes and experimentally demonstrates a topology optimization approach as a design tool for efficient integration of thermoelectric modules into systems with specific design constraints. The approach allows thermal layout optimization of thermoelectric systems for different operating conditions and objective functions, such as temperature span, efficiency, and power recovery rate. As a specific application, the integration of a thermoelectric cooler into the electronics section of a downhole oil well intervention tool is investigated, with the objective of minimizing the temperature of the cooled electronics. Several challenges are addressed: ensuring effective heat transfer from the load, minimizing the thermal resistances within the integrated system, maximizing the thermal protection of the cooled zone, and enhancing the conduction of the rejected heat to the oil well. The design method incorporates temperature dependent properties of the thermoelectric device and other materials. The 3D topology optimization model developed in this work was used to design a thermoelectric system, complete with insulation and heat sink, that was produced and tested. Good agreement between experimental results and

Spectral response, dark current, and noise analyses in resonant tunneling quantum dot infrared photodetectors.

Science.gov (United States)

Jahromi, Hamed Dehdashti; Mahmoodi, Ali; Sheikhi, Mohammad Hossein; Zarifkar, Abbas

2016-10-20

Reduction of dark current at high-temperature operation is a great challenge in conventional quantum dot infrared photodetectors, as the rate of thermal excitations resulting in the dark current increases exponentially with temperature. A resonant tunneling barrier is the best candidate for suppression of dark current, enhancement in signal-to-noise ratio, and selective extraction of different wavelength response. In this paper, we use a physical model developed by the authors recently to design a proper resonant tunneling barrier for quantum infrared photodetectors and to study and analyze the spectral response of these devices. The calculated transmission coefficient of electrons by this model and its dependency on bias voltage are in agreement with experimental results. Furthermore, based on the calculated transmission coefficient, the dark current of a quantum dot infrared photodetector with a resonant tunneling barrier is calculated and compared with the experimental data. The validity of our model is proven through this comparison. Theoretical dark current by our model shows better agreement with the experimental data and is more accurate than the previously developed model. Moreover, noise in the device is calculated. Finally, the effect of different parameters, such as temperature, size of quantum dots, and bias voltage, on the performance of the device is simulated and studied.

An optoelectronic integrated device including a laser and its driving circuit

Energy Technology Data Exchange (ETDEWEB)

Matsueda, H.; Nakano, H.; Tanaka, T.P.

1984-10-01

A monolithic optoelectronic integrated circuit (OEIC) including a laser diode, photomonitor and driving and detecting circuits has been fabricated on a semi-insulating GaAs substrate. The OEIC has a horizontal integrating structure which is suitable for realising high-density multifunctional devices. The fabricating process and the static and dynamic characteristics of the optical and electronic elements are described. The preliminary results of the co-operative operation of the laser and its driving circuit are also presented.

Josephson tunneling current in the presence of a time-dependent voltage

International Nuclear Information System (INIS)

Harris, R.E.

1975-01-01

The expression for the current through a small Josephson tunnel junction in the presence of a time-dependent voltage is presented. Four terms appear: the usual sine, cosine, and quasiparticle terms, and a reactive part of the quasiparticle current. The latter is displayed graphically as a function of both energy and temperature. It is shown that in the limit of zero dc voltage and small ac voltage, the Josephson device behaves linearly. Interpretation of the in- and out-of-phase components of the current in this linear limit is given to provide physical insight into some of the details of the general expression. Finally, the tunneling current in the linear limit is shown for thin tunneling barriers to be proportional to the current in a single superconductor in the presence of an electromagnetic field

New memory devices based on the proton transfer process

Science.gov (United States)

Wierzbowska, Małgorzata

2016-01-01

Memory devices operating due to the fast proton transfer (PT) process are proposed by the means of first-principles calculations. Writing information is performed using the electrostatic potential of scanning tunneling microscopy (STM). Reading information is based on the effect of the local magnetization induced at the zigzag graphene nanoribbon (Z-GNR) edge—saturated with oxygen or the hydroxy group—and can be realized with the use of giant magnetoresistance (GMR), a magnetic tunnel junction or spin-transfer torque devices. The energetic barriers for the hop forward and backward processes can be tuned by the distance and potential of the STM tip; this thus enables us to tailor the non-volatile logic states. The proposed system enables very dense packing of the logic cells and could be used in random access and flash memory devices.

The role of the tunneling matrix element and nuclear reorganization in the design of quantum-dot cellular automata molecules

Science.gov (United States)

Henry, Jackson; Blair, Enrique P.

2018-02-01

Mixed-valence molecules provide an implementation for a high-speed, energy-efficient paradigm for classical computing known as quantum-dot cellular automata (QCA). The primitive device in QCA is a cell, a structure with multiple quantum dots and a few mobile charges. A single mixed-valence molecule can function as a cell, with redox centers providing quantum dots. The charge configuration of a molecule encodes binary information, and device switching occurs via intramolecular electron transfer between dots. Arrays of molecular cells adsorbed onto a substrate form QCA logic. Individual cells in the array are coupled locally via the electrostatic electric field. This device networking enables general-purpose computing. Here, a quantum model of a two-dot molecule is built in which the two-state electronic system is coupled to the dominant nuclear vibrational mode via a reorganization energy. This model is used to explore the effects of the electronic inter-dot tunneling (coupling) matrix element and the reorganization energy on device switching. A semi-classical reduction of the model also is made to investigate the competition between field-driven device switching and the electron-vibrational self-trapping. A strong electron-vibrational coupling (high reorganization energy) gives rise to self-trapping, which inhibits the molecule's ability to switch. Nonetheless, there remains an expansive area in the tunneling-reorganization phase space where molecules can support adequate tunneling. Thus, the relationship between the tunneling matrix element and the reorganization energy affords significant leeway in the design of molecules viable for QCA applications.

Numerical solution of multiband k.p model for tunnelling in type-II heterostructures

Directory of Open Access Journals (Sweden)

A.E. Botha

2010-01-01

Full Text Available A new and very general method was developed for calculating the charge and spin-resolved electron tunnelling in type-II heterojunctions. Starting from a multiband k.p description of the bulk energy-band structure, a multiband k.p Riccati equation was derived. The reflection and transmission coefficients were obtained for each channel by integrating the Riccati equation over the entire heterostructure. Numerical instability was reduced through this method, in which the multichannel log-derivative of the envelope function matrix, rather than the envelope function itself, was propagated. As an example, a six-band k.p Hamiltonian was used to calculate the current-voltage characteristics of a 10-nm wide InAs/ GaSb/InAs single quantum well device which exhibited negative differential resistance at room temperature. The calculated current as a function of applied (bias voltage was found to be in semiquantitative agreement with the experiment, a result which indicated that inelastic transport mechanisms do not contribute significantly to the valley currents measured in this particular device.

A Printed Equilibrium Dialysis Device with Integrated Membranes for Improved Binding Affinity Measurements.

Science.gov (United States)

Pinger, Cody W; Heller, Andrew A; Spence, Dana M

2017-07-18

Equilibrium dialysis is a simple and effective technique used for investigating the binding of small molecules and ions to proteins. A three-dimensional (3D) printer was used to create a device capable of measuring binding constants between a protein and a small ion based on equilibrium dialysis. Specifically, the technology described here enables the user to customize an equilibrium dialysis device to fit their own experiments by choosing membranes of various material and molecular-weight cutoff values. The device has dimensions similar to that of a standard 96-well plate, thus being amenable to automated sample handlers and multichannel pipettes. The device consists of a printed base that hosts multiple windows containing a porous regenerated-cellulose membrane with a molecular-weight cutoff of ∼3500 Da. A key step in the fabrication process is a print-pause-print approach for integrating membranes directly into the windows subsequently inserted into the base. The integrated membranes display no leaking upon placement into the base. After characterizing the system's requirements for reaching equilibrium, the device was used to successfully measure an equilibrium dissociation constant for Zn 2+ and human serum albumin (K d = (5.62 ± 0.93) × 10 -7 M) under physiological conditions that is statistically equal to the constants reported in the literature.

Spin-dependent tunneling transport in a lateral magnetic diode

International Nuclear Information System (INIS)

Wang, Yu; Shi, Ying

2012-01-01

Based on the gate-tunable two-dimensional electron gas, we have constructed laterally a double-barrier resonant tunneling structure by employing a peculiar triple-gate configuration, namely a ferromagnetic gate sandwiched closely by a pair of Schottky gates. Because of the in-plane stray field of ferromagnetic gate, the resulting bound spin state in well gives rise to the remarkable resonant spin polarization following the spin-dependent resonant tunneling regime. Importantly, by aligning the bound spin state through surface gate-voltage configuration, this resonant spin polarization can be externally manipulated, showing the desirable features for the spin-logic device applications. -- Highlights: ► A lateral spin-RTD was proposed by applying triple-gate modulated 2DEG. ► Spin-dependent resonant tunneling transport and large resonant spin polarization has been clarified from the systematic simulation. ► Both electric and/or magnetic strategies can be employed to modulate the system spin transport, providing the essential features for the spin-logic application.

Microfluidic device for continuous single cells analysis via Raman spectroscopy enhanced by integrated plasmonic nanodimers

KAUST Repository

Perozziello, Gerardo; Candeloro, Patrizio; De Grazia, Antonio; Esposito, Francesco; Allione, Marco; Coluccio, Maria Laura; Tallerico, Rossana; Valpapuram, Immanuel; Tirinato, Luca; Das, Gobind; Giugni, Andrea; Torre, Bruno; Veltri, Pierangelo; Kruhne, Ulrich; Della Valle, Giuseppe; Di Fabrizio, Enzo M.

2015-01-01

In this work a Raman flow cytometer is presented. It consists of a microfluidic device that takes advantages of the basic principles of Raman spectroscopy and flow cytometry. The microfluidic device integrates calibrated microfluidic channels- where

Study of the tunnelling initiated leakage current through the carbon nanotube embedded gate oxide in metal oxide semiconductor structures

International Nuclear Information System (INIS)

Chakraborty, Gargi; Sarkar, C K; Lu, X B; Dai, J Y

2008-01-01

The tunnelling currents through the gate dielectric partly embedded with semiconducting single-wall carbon nanotubes in a silicon metal-oxide-semiconductor (MOS) structure have been investigated. The application of the gate voltage to such an MOS device results in the band bending at the interface of the partly embedded oxide dielectric and the surface of the silicon, initiating tunnelling through the gate oxide responsible for the gate leakage current whenever the thickness of the oxide is scaled. A model for silicon MOS structures, where carbon nanotubes are confined in a narrow layer embedded in the gate dielectric, is proposed to investigate the direct and the Fowler-Nordheim (FN) tunnelling currents of such systems. The idea of embedding such elements in the gate oxide is to assess the possibility for charge storage for memory device applications. Comparing the FN tunnelling onset voltage between the pure gate oxide and the gate oxide embedded with carbon nanotubes, it is found that the onset voltage decreases with the introduction of the nanotubes. The direct tunnelling current has also been studied at very low gate bias, for the thin oxide MOS structure which plays an important role in scaling down the MOS transistors. The FN tunnelling current has also been studied with varying nanotube diameter

A novel Tunneling Graphene Nano Ribbon Field Effect Transistor with dual material gate: Numerical studies

Science.gov (United States)

Ghoreishi, Seyed Saleh; Saghafi, Kamyar; Yousefi, Reza; Moravvej-farshi, Mohammad Kazem

2016-09-01

In this work, we present Dual Material Gate Tunneling Graphene Nano-Ribbon Field Effect Transistors (DMG-T-GNRFET) mainly to suppress the am-bipolar current with assumption that sub-threshold swing which is one of the important characteristics of tunneling transistors must not be degraded. In the proposed structure, dual material gates with different work functions are used. Our investigations are based on numerical simulations which self-consistently solves the 2D Poisson based on an atomistic mode-space approach and Schrodinger equations, within the Non-Equilibrium Green's (NEGF). The proposed device shows lower off-current and on-off ratio becomes 5order of magnitude greater than the conventional device. Also two different short channel effects: Drain Induced Barrier Shortening (DIBS) and hot-electron effect are improved in the proposed device compare to the main structure.

Fabrication and current–voltage characteristics of NiOx/ZnO based MIIM tunnel diode

Energy Technology Data Exchange (ETDEWEB)

Singh, Aparajita, E-mail: asing044@fiu.edu [BioMEMS and Microsystems Laboratory, Department of Electrical and Computer Engineering, Florida International University, Miami, Florida 33174, United States of America (United States); Ratnadurai, Rudraskandan [Global Foundaries, Malta, New York 12020 (United States); Kumar, Rajesh [BioMEMS and Microsystems Laboratory, Department of Electrical and Computer Engineering, Florida International University, Miami, Florida 33174 (United States); Department of Physics, Panjab University, Chandigarh 160014 (India); Krishnan, Subramanian [BioMEMS and Microsystems Laboratory, Department of Electrical and Computer Engineering, Florida International University, Miami, Florida 33174 (United States); Emirov, Yusuf [Advanced Materials Engineering Research Institute, Florida International University, Miami, Florida 33174 (United States); Bhansali, Shekhar [BioMEMS and Microsystems Laboratory, Department of Electrical and Computer Engineering, Florida International University, Miami, Florida 33174 (United States)

2015-04-15

Highlights: • Fabrication of single and bilayer tunnel diodes by sputter deposition. • Current–voltage characteristics study. • Enhanced asymmetry and non-linearity. • Study of tunneling mechanism. - Abstract: Enhanced asymmetric and non-linear characteristics of Ni–NiOx based MIM diode has been reported by the addition of a second insulator layer ZnO to form MIIM configuration. These properties are required for applications like energy-harvesting devices, terahertz electronics, macro electronics, etc. In this work, single insulator layer Ni–NiOx–Cr and double insulator Ni–NiOx–ZnO–Cr tunnel diodes were fabricated and their I–V characteristics were studied. A significant increase by one order of magnitude in asymmetry has been observed in case of bilayer NiOx/ZnO dielectric configuration at low voltages. The sensitivity of the NiOx and NiOx/ZnO dielectric configuration in MIM stack was 11 V{sup −1} and 16 V{sup −1}. The improved performance of the bilayer insulator diode is due to the second insulator which enables resonant tunneling or step-tunneling. Resonant tunneling was found to be dominant through trap assisted tunneling in the NiOx/ZnO diode.

Tunneling explains efficient electron transport via protein junctions.

Science.gov (United States)

Fereiro, Jerry A; Yu, Xi; Pecht, Israel; Sheves, Mordechai; Cuevas, Juan Carlos; Cahen, David

2018-05-15

Metalloproteins, proteins containing a transition metal ion cofactor, are electron transfer agents that perform key functions in cells. Inspired by this fact, electron transport across these proteins has been widely studied in solid-state settings, triggering the interest in examining potential use of proteins as building blocks in bioelectronic devices. Here, we report results of low-temperature (10 K) electron transport measurements via monolayer junctions based on the blue copper protein azurin (Az), which strongly suggest quantum tunneling of electrons as the dominant charge transport mechanism. Specifically, we show that, weakening the protein-electrode coupling by introducing a spacer, one can switch the electron transport from off-resonant to resonant tunneling. This is a consequence of reducing the electrode's perturbation of the Cu(II)-localized electronic state, a pattern that has not been observed before in protein-based junctions. Moreover, we identify vibronic features of the Cu(II) coordination sphere in transport characteristics that show directly the active role of the metal ion in resonance tunneling. Our results illustrate how quantum mechanical effects may dominate electron transport via protein-based junctions.