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Sample records for insulated gate field

  1. Gate protective device for insulated gate field-effect transistors

    NASA Technical Reports Server (NTRS)

    Sunshine, R. A.

    1972-01-01

    Device, which protects insulated gate field-effect transistors, improves reliability through utilization of layers of conductive material on top of each alternating semiconductor material region. Separation of layers is necessary to prevent shorting out junctions between alternating regions.

  2. Pressure Sensitive Insulated Gate Field Effect Transistor

    NASA Astrophysics Data System (ADS)

    Suminto, James Tjan-Meng

    A pressure sensitive insulated gate field effect transistor has been developed. The device is an elevated gate field-effect-transistor. It consists of a p-type silicon substrate in which two n^+ region, the source and drain, are formed. The gate electrode is a metal film sandwiched in an insulated micro-diaphragm resembling a pill-box which covers the gate oxide, drain, and source. The space between the gate electrode and the oxide is vacuum or an air-gap. When pressure is applied on the diaphragm it deflects and causes a change in the gate capacitance, and thus modulates the conductance of the channel between source and drain. A general theory dealing with the characteristic of this pressure sensitive insulated gate field effect transistor has been derived, and the device fabricated. The fabrication process utilizes the standard integrated circuit fabrication method. It features a batch fabrication of field effect devices followed by the batch fabrication of the deposited diaphragm on top of each field effect device. The keys steps of the diaphragm fabrication are the formation of spacer layer, formation of the diaphragm layer, and the subsequent removal of the spacer layer. The chip size of the device is 600 μm x 1050 mum. The diaphragm size is 200 μm x 200 mum. Characterization of the device has been performed. The current-voltage characteristics with pressure as parameters have been demonstrated and the current-pressure transfer curves obtained. They show non-linear characteristics as those of conventional capacitive pressure sensors. The linearity of threshold voltage versus pressure transfer curves has been demonstrated. The temperature effect on the device performances has been tested. The temperature coefficient of threshold voltage, rather than the electron mobility, has dominated the temperature coefficient of the device. Two temperature compensation schemes have been tested: one method is by connecting two identical PSIGFET in a differential amplifier

  3. Multiplexer uses insulated gate-field effect transistors

    NASA Technical Reports Server (NTRS)

    Gussow, S. S.

    1967-01-01

    Small lightweight multiplexer incorporates IG-FETs /Insulated Gate-Field Effect Transistors/ for all digital logic functions, including the internally generated 3.6-kHz clock. It consists of 30 primary channels, each of which is sampled 120 times per second.

  4. Radiation tolerant silicon nitride insulated gate field effect transistors

    NASA Technical Reports Server (NTRS)

    Newman, P. A.

    1969-01-01

    Metal-Insulated-Semiconductor Field Effect Transistor /MISFET/ device uses a silicon nitride passivation layer over a thin silicon oxide layer to enhance the radiation tolerance. It is useful in electronic systems exposed to space radiation environment or the effects of nuclear weapons.

  5. High-mobility bio-organic field effect transistors with photoreactive DNAs as gate insulators

    NASA Astrophysics Data System (ADS)

    Kim, Youn Sun; Jung, Ki Hwa; Lee, U. Ra; Kim, Kyung Hwan; Hoang, Mai Ha; Jin, Jung-Il; Choi, Dong Hoon

    2010-03-01

    Organic-soluble DNAs bearing chalcone moieties were synthesized by using purified natural sodium DNA. In addition to the chalcone-containing DNA homopolymer (CcDNA), a copolymer (CTMADNA-co-CcDNA) was synthesized. They were employed as gate insulators for fabricating organic thin-film transistors. An organic semiconductor (5,5'-(9,10-bis((4-hexylphenyl)ethynyl)anthracene-2,6-yl-diyl)bis(ethyne-2,1-diyl)bis(2-hexylthiophene; HB-ant-THT) was deposited on the photocrosslinked DNA-based gate insulators via a solution process. Interestingly, the resulting TFT devices had extremely high field-effect mobilities, and their corresponding transfer curves indicated low hysteresis. The carrier mobility of the device with HB-ant-THT deposited on the CTMADNA-co-CcDNA gate insulator was the best, i.e., 0.31 cm2 V-1 s-1 (Ion/Ioff=1.0×104).

  6. H-terminated diamond field effect transistor with ferroelectric gate insulator

    NASA Astrophysics Data System (ADS)

    Karaya, Ryota; Furuichi, Hiroki; Nakajima, Takashi; Tokuda, Norio; Kawae, Takeshi

    2016-06-01

    An H-terminated diamond field-effect-transistor (FET) with a ferroelectric vinylidene fluoride (VDF)-trifluoroethylene (TrFE) copolymer gate insulator was fabricated. The VDF-TrFE film was deposited on the H-terminated diamond by the spin-coating method and low-temperature annealing was performed to suppress processing damage to the H-terminated diamond surface channel layer. The fabricated FET structure showed the typical properties of depletion-type p-channel FET and showed clear saturation of the drain current with a maximum value of 50 mA/mm. The drain current versus gate voltage curves of the proposed FET showed clockwise hysteresis loops due to the ferroelectricity of the VDF-TrFE gate insulator, and the memory window width was 19 V, when the gate voltage was swept from 20 to -20 V. The maximum on/off current ratio and the linear mobility were 108 and 398 cm2/V s, respectively. In addition, we modulated the drain current of the fabricated FET structure via the remnant polarization of the VDF-TrFE gate and obtained an on/off current ratio of 103 without applying a DC gate voltage.

  7. Demonstration of large field effect in topological insulator films via a high-κ back gate

    NASA Astrophysics Data System (ADS)

    Wang, C. Y.; Lin, H. Y.; Yang, S. R.; Chen, K. H. M.; Lin, Y. H.; Chen, K. H.; Young, L. B.; Cheng, C. K.; Fanchiang, Y. T.; Tseng, S. C.; Hong, M.; Kwo, J.

    2016-05-01

    The spintronics applications long anticipated for topological insulators (TIs) has been hampered due to the presence of high density intrinsic defects in the bulk states. In this work we demonstrate the back-gating effect on TIs by integrating Bi2Se3 films 6-10 quintuple layer (QL) thick with amorphous high-κ oxides of Al2O3 and Y2O3. Large gating effect of tuning the Fermi level EF to very close to the band gap was observed, with an applied bias of an order of magnitude smaller than those of the SiO2 back gate, and the modulation of film resistance can reach as high as 1200%. The dependence of the gating effect on the TI film thickness was investigated, and ΔN2D/ΔVg varies with TI film thickness as ˜t-0.75. To enhance the gating effect, a Y2O3 layer thickness 4 nm was inserted into Al2O3 gate stack to increase the total κ value to 13.2. A 1.4 times stronger gating effect is observed, and the increment of induced carrier numbers is in good agreement with additional charges accumulated in the higher κ oxides. Moreover, we have reduced the intrinsic carrier concentration in the TI film by doping Te to Bi2Se3 to form Bi2TexSe1-x. The observation of a mixed state of ambipolar field that both electrons and holes are present indicates that we have tuned the EF very close to the Dirac Point. These results have demonstrated that our capability of gating TIs with high-κ back gate to pave the way to spin devices of tunable EF for dissipationless spintronics based on well-established semiconductor technology.

  8. Gate Tunable Relativistic Mass and Berry's phase in Topological Insulator Nanoribbon Field Effect Devices

    PubMed Central

    Jauregui, Luis A.; Pettes, Michael T.; Rokhinson, Leonid P.; Shi, Li; Chen, Yong P.

    2015-01-01

    Transport due to spin-helical massless Dirac fermion surface state is of paramount importance to realize various new physical phenomena in topological insulators, ranging from quantum anomalous Hall effect to Majorana fermions. However, one of the most important hallmarks of topological surface states, the Dirac linear band dispersion, has been difficult to reveal directly in transport measurements. Here we report experiments on Bi2Te3 nanoribbon ambipolar field effect devices on high-κ SrTiO3 substrates, where we achieve a gate-tuned bulk metal-insulator transition and the topological transport regime with substantial surface state conduction. In this regime, we report two unambiguous transport evidences for gate-tunable Dirac fermions through π Berry's phase in Shubnikov-de Haas oscillations and effective mass proportional to the Fermi momentum, indicating linear energy-momentum dispersion. We also measure a gate-tunable weak anti-localization (WAL) with 2 coherent conduction channels (indicating 2 decoupled surfaces) near the charge neutrality point, and a transition to weak localization (indicating a collapse of the Berry's phase) when the Fermi energy approaches the bulk conduction band. The gate-tunable Dirac fermion topological surface states pave the way towards a variety of topological electronic devices. PMID:25677703

  9. Gate Tunable Relativistic Mass and Berry's phase in Topological Insulator Nanoribbon Field Effect Devices

    NASA Astrophysics Data System (ADS)

    Jauregui, Luis A.; Pettes, Michael T.; Rokhinson, Leonid P.; Shi, Li; Chen, Yong P.

    2015-02-01

    Transport due to spin-helical massless Dirac fermion surface state is of paramount importance to realize various new physical phenomena in topological insulators, ranging from quantum anomalous Hall effect to Majorana fermions. However, one of the most important hallmarks of topological surface states, the Dirac linear band dispersion, has been difficult to reveal directly in transport measurements. Here we report experiments on Bi2Te3 nanoribbon ambipolar field effect devices on high-κ SrTiO3 substrates, where we achieve a gate-tuned bulk metal-insulator transition and the topological transport regime with substantial surface state conduction. In this regime, we report two unambiguous transport evidences for gate-tunable Dirac fermions through π Berry's phase in Shubnikov-de Haas oscillations and effective mass proportional to the Fermi momentum, indicating linear energy-momentum dispersion. We also measure a gate-tunable weak anti-localization (WAL) with 2 coherent conduction channels (indicating 2 decoupled surfaces) near the charge neutrality point, and a transition to weak localization (indicating a collapse of the Berry's phase) when the Fermi energy approaches the bulk conduction band. The gate-tunable Dirac fermion topological surface states pave the way towards a variety of topological electronic devices.

  10. Field effect transistor with HfO2/Parylene-C bilayer hybrid gate insulator

    NASA Astrophysics Data System (ADS)

    Kumar, Neeraj; Kito, Ai; Inoue, Isao

    2015-03-01

    We have investigated the electric field control of the carrier density and the mobility at the surface of SrTiO3, a well known transition-metal oxide, in a field effect transistor (FET) geometry. We have used a Parylene-C (8 nm)/HfO2 (20 nm) double-layer gate insulator (GI), which can be a potential candidate for a solid state GI for the future Mott FETs. So far, only examples of the Mott FET used liquid electrolyte or ferroelectric oxides for the GI. However, possible electrochemical reaction at the interface causes damage to the surface of the Mott insulator. Thus, an alternative GI has been highly desired. We observed that even an ultra thin Parylene-C layer is effective for keeping the channel surface clean and free from oxygen vacancies. The 8 nm Parylene-C film has a relatively low resistance and consequentially its capacitance does not dominate the total capacitance of the Parylene-C/HfO2 GI. The breakdown gate voltage at 300 K is usually more than 10 V (~ 3.4 MV/cm). At gate voltage of 3 V the carrier density measured by the Hall effect is about 3 ×1013 cm-2, competent to cause the Mott transition. Moreover, the field effect mobility reaches in the range of 10 cm2/Vs indicating the Parylene-C passivated surface is actually very clean.

  11. Characterization of a vertically movable gate field effect transistor using a silicon-on-insulator wafer

    NASA Astrophysics Data System (ADS)

    Song, In-Hyouk; Forfang, William B. D.; Cole, Bryan; You, Byoung Hee

    2014-10-01

    The vertically movable gate field effect transistor (VMGFET) is a FET-based sensing element, whose gate moves in a vertical direction over the channel. A VMGFET gate covers the region between source and drain. A 1 μm thick air layer separates the gate and the substrate of the VMGFET. A novel fabrication process to form a VMGFET using a silicon-on-insulator (SOI) wafer provides minimal internal stress of the gate structure. The enhancement-type n-channel VMGFET is fabricated with the threshold voltage of 2.32 V in steady state. A non-inverting amplifier is designed and integrated on a printable circuit board (PCB) to characterize device sensitivity and mechanical properties. The VMGFET is mechanically coupled to a speaker membrane to apply mechanical vibration. The oscillated drain current of FET are monitored and sampled with NI LabVIEW. The frequency of the output signal correlates with that of the input stimulus. The resonance frequency of the fabricated VMGFET is measured to be 1.11 kHz. The device sensitivity linearly increases by 0.106 mV/g Hz in the range of 150 Hz and 1 kHz.

  12. Plasma Deposited SiO2 for Planar Self-Aligned Gate Metal-Insulator-Semiconductor Field Effect Transistors on Semi-Insulating InP

    NASA Technical Reports Server (NTRS)

    Tabory, Charles N.; Young, Paul G.; Smith, Edwyn D.; Alterovitz, Samuel A.

    1994-01-01

    Metal-insulator-semiconductor (MIS) field effect transistors were fabricated on InP substrates using a planar self-aligned gate process. A 700-1000 A gate insulator of Si02 doped with phosphorus was deposited by a direct plasma enhanced chemical vapor deposition at 400 mTorr, 275 C, 5 W, and power density of 8.5 MW/sq cm. High frequency capacitance-voltage measurements were taken on MIS capacitors which have been subjected to a 700 C anneal and an interface state density of lxl0(exp 11)/eV/cq cm was found. Current-voltage measurements of the capacitors show a breakdown voltage of 107 V/cm and a insulator resistivity of 10(exp 14) omega cm. Transistors were fabricated on semi-insulating InP using a standard planar self-aligned gate process in which the gate insulator was subjected to an ion implantation activation anneal of 700 C. MIS field effect transistors gave a maximum extrinsic transconductance of 23 mS/mm for a gate length of 3 microns. The drain current drift saturated at 87.5% of the initial current, while reaching to within 1% of the saturated value after only 1x10(exp 3). This is the first reported viable planar InP self-aligned gate transistor process reported to date.

  13. Plasma-deposited germanium nitride gate insulators for indium phosphide metal-insulator-semiconductor field-effect transistors

    NASA Technical Reports Server (NTRS)

    Johnson, Gregory A.; Kapoor, Vik J.

    1991-01-01

    Plasma-deposited germanium nitride was investigated for the first time as a possible gate insulator for InP compound semiconductor metal-insulator-semiconductor FET (MISFET) technology. The germanium nitride films were successfully deposited in a capacitively coupled parallel plate reactor at 13.56 MHz operation using GeH4/N2/NH3 and GeH4/N2 mixtures as reactant gases. The former process produced better quality films with enhanced uniformity, increased deposition rates, and increased resistivity. The breakdown field strength of the films was greater than 10 to the 6th V/cm. Auger electron spectroscopy did not indicate significant chemical composition differences between the two processes. For MISFETs with 2-micron channel lengths fabricated on InP, the device transconductance and threshold voltage for the GeH4/N2/NH3 process were 17 mS/mm and -3.6 V, respectively. The drain-source breakdown voltages were greater than 10 V.

  14. Silicon dioxide with a silicon interfacial layer as an insulating gate for highly stable indium phosphide metal-insulator-semiconductor field effect transistors

    NASA Technical Reports Server (NTRS)

    Kapoor, V. J.; Shokrani, M.

    1991-01-01

    A novel gate insulator consisting of silicon dioxide (SiO2) with a thin silicon (Si) interfacial layer has been investigated for high-power microwave indium phosphide (InP) metal-insulator-semiconductor field effect transistors (MISFETs). The role of the silicon interfacial layer on the chemical nature of the SiO2/Si/InP interface was studied by high-resolution X-ray photoelectron spectroscopy. The results indicated that the silicon interfacial layer reacted with the native oxide at the InP surface, thus producing silicon dioxide, while reducing the native oxide which has been shown to be responsible for the instabilities in InP MISFETs. While a 1.2-V hysteresis was present in the capacitance-voltage (C-V) curve of the MIS capacitors with silicon dioxide, less than 0.1 V hysteresis was observed in the C-V curve of the capacitors with the silicon interfacial layer incorporated in the insulator. InP MISFETs fabricated with the silicon dioxide in combination with the silicon interfacial layer exhibited excellent stability with drain current drift of less than 3 percent in 10,000 sec, as compared to 15-18 percent drift in 10,000 sec for devices without the silicon interfacial layer. High-power microwave InP MISFETs with Si/SiO2 gate insulators resulted in an output power density of 1.75 W/mm gate width at 9.7 GHz, with an associated power gain of 2.5 dB and 24 percent power added efficiency.

  15. Advanced insulated gate bipolar transistor gate drive

    DOEpatents

    Short, James Evans; West, Shawn Michael; Fabean, Robert J.

    2009-08-04

    A gate drive for an insulated gate bipolar transistor (IGBT) includes a control and protection module coupled to a collector terminal of the IGBT, an optical communications module coupled to the control and protection module, a power supply module coupled to the control and protection module and an output power stage module with inputs coupled to the power supply module and the control and protection module, and outputs coupled to a gate terminal and an emitter terminal of the IGBT. The optical communications module is configured to send control signals to the control and protection module. The power supply module is configured to distribute inputted power to the control and protection module. The control and protection module outputs on/off, soft turn-off and/or soft turn-on signals to the output power stage module, which, in turn, supplies a current based on the signal(s) from the control and protection module for charging or discharging an input capacitance of the IGBT.

  16. A Pt-Ti-O gate Si-metal-insulator-semiconductor field-effect transistor hydrogen gas sensor

    NASA Astrophysics Data System (ADS)

    Usagawa, Toshiyuki; Kikuchi, Yota

    2010-10-01

    A hydrogen gas sensor based on platinum-titanium-oxygen (Pt-Ti-O) gate silicon-metal-insulator-semiconductor field-effect transistors (Si-MISFETs) was developed. The sensor has a unique gate structure composed of titanium and oxygen accumulated around platinum grains on top of a novel mixed layer of nanocrystalline TiOx and superheavily oxygen-doped amorphous titanium formed on SiO2/Si substrates. The FET hydrogen sensor shows high reliability and high sensing amplitude (Δ Vg) defined by the magnitude of the threshold voltage shift. Δ Vg is well fitted by a linear function of the logarithm of air-diluted hydrogen concentration C (ppm), i.e., Δ Vg(V) =0.355 log C(ppm ) -0.610 , between 100 ppm and 1%. This high gradient coefficient of Δ Vg for the wide sensing range demonstrates that the sensor is suitable for most hydrogen-safety-monitoring sensor systems. The Pt-Ti-O structures of the sensor are typically realized by annealing Pt (15 nm)/Ti (5 nm)-gate Si-metal-oxide-semiconductor structures in air at 400 °C for 2 h. The Pt-Ti-O gate MIS structures were analyzed by transmission electron microscope (TEM), x-ray diffraction, Auger electron spectroscopy, and TEM energy dispersive x-ray spectroscopy. From the viewpoint of practical sensing applications, hydrogen postannealing of the Pt-Ti-O gate Si-MISFETs is necessary to reduce the residual sensing amplitudes with long tailing profiles.

  17. High quality interfaces of InAs-on-insulator field-effect transistors with ZrO2 gate dielectrics

    NASA Astrophysics Data System (ADS)

    Takei, Kuniharu; Kapadia, Rehan; Fang, Hui; Plis, E.; Krishna, Sanjay; Javey, Ali

    2013-04-01

    Interface quality of InAs-on-insulator (XOI) field-effect transistors (FETs) with a ZrO2 gate dielectric is examined as a function of various chemical treatments. With a forming gas anneal, InAs XOI FETs exhibit a low subthreshold swing of ˜72 mV/dec with an interface trap density of ˜1.5 × 1012 states/cm2 eV—both of which are comparable to the best reported epitaxially grown III-V devices on III-V substrates. Importantly, the results indicate that the surface properties of InAs are preserved during the layer transfer process, thereby, enabling the realization of high performance III-V FETs on Si substrates using the XOI configuration.

  18. High performance organic field-effect transistors with ultra-thin HfO{sub 2} gate insulator deposited directly onto the organic semiconductor

    SciTech Connect

    Ono, S.; Häusermann, R.; Chiba, D.; Shimamura, K.; Ono, T.; Batlogg, B.

    2014-01-06

    We have produced stable organic field-effect transistors (OFETs) with an ultra-thin HfO{sub 2} gate insulator deposited directly on top of rubrene single crystals by atomic layer deposition (ALD). We find that ALD is a gentle deposition process to grow thin films without damaging rubrene single crystals, as results these devices have a negligibly small threshold voltage and are very stable against gate-bias-stress, and the mobility exceeds 1 cm{sup 2}/V s. Moreover, the devices show very little degradation even when kept in air for more than 2 months. These results demonstrate thin HfO{sub 2} layers deposited by ALD to be well suited as high capacitance gate dielectrics in OFETs operating at small gate voltage. In addition, the dielectric layer acts as an effective passivation layer to protect the organic semiconductor.

  19. Top-gated graphene field-effect transistors by low-temperature synthesized SiN x insulator on SiC substrates

    NASA Astrophysics Data System (ADS)

    Ohno, Yasuhide; Kanai, Yasushi; Mori, Yuki; Nagase, Masao; Matsumoto, Kazuhiko

    2016-06-01

    Top-gated devices made from an epitaxial graphene film on a 4H-SiC substrate were fabricated. Atomic force microscopy and Raman spectroscopy results showed that a large-scale highly uniform monolayer graphene film was synthesized on the SiC substrate. A SiN x passivation film was deposited on a SiC graphene device as a top gate insulator by catalytic chemical-vapor deposition (Cat-CVD) below 65 °C. After the top gate electrode was formed on the SiN x film, no leakage current flowed between the gate and source electrodes. The transport characteristics showed clear ambipolar characteristics from 8 to 280 K, and the temperature dependences of the conductance and field-effect mobility of the devices implied that monolayer graphene devices can be successfully fabricated. Moreover, the position of the charge neutrality point after SiN x deposition was around 0 V, indicating p-doping characteristics. These results indicate that SiN x films synthesized by Cat-CVD can be used as gate insulators and that the carrier type may be controlled by adjusting the deposition conditions.

  20. Persistent optical gating of a topological insulator

    PubMed Central

    Yeats, Andrew L.; Pan, Yu; Richardella, Anthony; Mintun, Peter J.; Samarth, Nitin; Awschalom, David D.

    2015-01-01

    The spin-polarized surface states of topological insulators (TIs) are attractive for applications in spintronics and quantum computing. A central challenge with these materials is to reliably tune the chemical potential of their electrons with respect to the Dirac point and the bulk bands. We demonstrate persistent, bidirectional optical control of the chemical potential of (Bi,Sb)2Te3 thin films grown on SrTiO3. By optically modulating a space-charge layer in the SrTiO3 substrates, we induce a persistent field effect in the TI films comparable to electrostatic gating techniques but without additional materials or processing. This enables us to optically pattern arbitrarily shaped p- and n-type regions in a TI, which we subsequently image with scanning photocurrent microscopy. The ability to optically write and erase mesoscopic electronic structures in a TI may aid in the investigation of the unique properties of the topological insulating phase. The gating effect also generalizes to other thin-film materials, suggesting that these phenomena could provide optical control of chemical potential in a wide range of ultrathin electronic systems. PMID:26601300

  1. Low-voltage organic field-effect transistors based on novel high-κ organometallic lanthanide complex for gate insulating materials

    SciTech Connect

    Liu, Qi; Li, Yi; Zhang, Yang; Song, You E-mail: yli@nju.edu.cn Wang, Xizhang E-mail: yli@nju.edu.cn Hu, Zheng; Sun, Huabin; Li, Yun E-mail: yli@nju.edu.cn Shi, Yi

    2014-08-15

    A novel high-κ organometallic lanthanide complex, Eu(tta){sub 3}L (tta=2-thenoyltrifluoroacetonate, L = 4,5-pinene bipyridine), is used as gate insulating material to fabricate low-voltage pentacene field-effect transistors (FETs). The optimized gate insulator exhibits the excellent properties such as low leakage current density, low surface roughness, and high dielectric constant. When operated under a low voltage of −5 V, the pentacene FET devices show the attractive electrical performance, e.g. carrier mobility (μ{sub FET}) of 0.17 cm{sup 2} V{sup −1} s{sup −1}, threshold voltage (V{sub th}) of −0.9 V, on/off current ratio of 5 × 10{sup 3}, and subthreshold slope (SS) of 1.0 V dec{sup −1}, which is much better than that of devices obtained on conventional 300 nm SiO{sub 2} substrate (0.13 cm{sup 2} V{sup −1} s{sup −1}, −7.3 V and 3.1 V dec{sup −1} for μ{sub FET}, V{sub th} and SS value when operated at −30 V). These results indicate that this kind of high-κ organometallic lanthanide complex becomes a promising candidate as gate insulator for low-voltage organic FETs.

  2. Dual insulated-gate field-effect transistors with cadmium sulfide active layer and a laminated polymer dielectric

    NASA Astrophysics Data System (ADS)

    Meth, J. S.; Zane, S. G.; Nunes, G.

    2004-04-01

    We report the fabrication of dual insulated gate thin-film transistors with chemical-bath deposited cadmium sulfide active layers. The cadmium sulfide was deposited from solution onto thermally oxidized silicon wafers to form the first semiconductor-dielectric interface. The terpolymer poly(tetrafluoroethylene-co-vinylidenefluoride-co-propylene) was laminated onto the semiconductor to create the second semiconductor-dielectric interface. This device geometry allows direct comparison of the behavior of the accumulated charge at these two very different interfaces. The mobility values for these devices are in the 0.1-1 cm2/Vs range, while the on/off ratios vary from 102 to 105. The ability to laminate a dielectric to a semiconductor enables new processing routes for large area transistor arrays.

  3. Silicon-on-insulator-based high-voltage, high-temperature integrated circuit gate driver for silicon carbide-based power field effect transistors

    SciTech Connect

    Tolbert, Leon M; Huque, Mohammad A; Blalock, Benjamin J; Islam, Syed K

    2010-01-01

    Silicon carbide (SiC)-based field effect transistors (FETs) are gaining popularity as switching elements in power electronic circuits designed for high-temperature environments like hybrid electric vehicle, aircraft, well logging, geothermal power generation etc. Like any other power switches, SiC-based power devices also need gate driver circuits to interface them with the logic units. The placement of the gate driver circuit next to the power switch is optimal for minimising system complexity. Successful operation of the gate driver circuit in a harsh environment, especially with minimal or no heat sink and without liquid cooling, can increase the power-to-volume ratio as well as the power-to-weight ratio for power conversion modules such as a DC-DC converter, inverter etc. A silicon-on-insulator (SOI)-based high-voltage, high-temperature integrated circuit (IC) gate driver for SiC power FETs has been designed and fabricated using a commercially available 0.8--m, 2-poly and 3-metal bipolar-complementary metal oxide semiconductor (CMOS)-double diffused metal oxide semiconductor (DMOS) process. The prototype circuit-s maximum gate drive supply can be 40-V with peak 2.3-A sourcing/sinking current driving capability. Owing to the wide driving range, this gate driver IC can be used to drive a wide variety of SiC FET switches (both normally OFF metal oxide semiconductor field effect transistor (MOSFET) and normally ON junction field effect transistor (JFET)). The switching frequency is 20-kHz and the duty cycle can be varied from 0 to 100-. The circuit has been successfully tested with SiC power MOSFETs and JFETs without any heat sink and cooling mechanism. During these tests, SiC switches were kept at room temperature and ambient temperature of the driver circuit was increased to 200-C. The circuit underwent numerous temperature cycles with negligible performance degradation.

  4. Nanoscale Electrical Imaging of Metal-Insulator Transition in Ion-Gel Gated ZnO Field Effect Transistors

    NASA Astrophysics Data System (ADS)

    Ren, Yuan; Yuan, Hongtao; Wu, Xiaoyu; Iwasa, Yoshihiro; Cui, Yi; Hwang, Harold; Lai, Keji

    2015-03-01

    Electric double-layer transistors (EDLTs) using ionic liquid as the gate dielectric have demonstrated a remarkably wide range of density modulation, a condition crucial for the study of novel electronic phases in complex quantum materials. Yet little is known microscopically when carriers are modulated in the EDLT structure because of the technical challenge to image the buried electrolyte-semiconductor interface with nanoscale resolution. Using a cryogenic microwave impedance microscope, we demonstrate the real-space conductivity mapping in ZnO EDLTs with a spatial resolution of 100nm. A thin layer of ion gel, which solidifies below the glass transition temperature of 200K, was spin-coated on the ZnO surface to induce the metal-insulator transition. The microwave images acquired at different channel conductance clearly showed the spatial evolution of local conductivity through the transition. In addition, by applying a large source-drain bias, electrical inhomogeneity was also observed across the source and drain electrodes.

  5. Numerical investigation of temperature field Induced by dual wavelength lasers in sub-microsecond laser annealing technology for insulated gate bipolar transistor

    NASA Astrophysics Data System (ADS)

    Cui, GuoDong; Ma, Mingying; Wang, Fan; Sun, Gang; Lan, Yanping; Xu, Wen

    2015-07-01

    To enhance the performance of the Insulated Gate Bipolar Transistor (IGBT), sub-microsecond laser annealing (LA) is propitious to achieve maximal dopant activation with minimal diffusion. In this work, two different lasers are used as annealing resource: a continuous 808 nm laser with larger spot is applied to preheat the wafer and another sub-microsecond pulsed 527 nm laser is responsible to activate the dopant. To optimize the system's performance, a physical model is presented to predict the thermal effect of two laser fields interacting on wafer. Using the Finite-Element method (FEM), we numerically investigate the temperature field induced by lasers in detail. The process window corresponding to the lasers is also acquired which can satisfy the requirements of the IGBT's annealing.

  6. Enhanced Total Ionizing Dose Hardness of Deep Sub-Micron Partially Depleted Silicon-on-Insulator n-Type Metal-Oxide-Semiconductor Field Effect Transistors by Applying Larger Back-Gate Voltage Stress

    NASA Astrophysics Data System (ADS)

    Zheng, Qi-Wen; Cui, Jiang-Wei; Yu, Xue-Feng; Guo, Qi; Zhou, Hang; Ren, Di-Yuan

    2014-12-01

    The larger back-gate voltage stress is applied on 130 nm partially depleted silicon-on-insulator n-type metal-oxide-semiconductor field-effect transistors isolated by shallow trench isolation. The experimental results show that the back-gate sub-threshold hump of the device is eliminated by stress. This observed behavior is caused by the high electric field in the oxide near the bottom corner of the silicon island. The total ionizing dose hardness of devices with pre back-gate stress is enhanced by the interface states induced by stress.

  7. Kinetic study of light-driven processes in photochromic dye-doped polymers used as gate insulators in photoswitchable organic field effect transistors

    NASA Astrophysics Data System (ADS)

    Lutsyk, Petro; Janus, Krzysztof; Sworakowski, Juliusz; Kochalska, Anna; Nešpůrek, Stanislav

    2012-08-01

    The paper reports on kinetic measurements of coloring and bleaching reactions in the spiropyran - merocyanine photochromic system dissolved in poly(methyl methacrylate) matrix (PMMA/SP). The system was earlier used as the gate insulator in a photo-switchable organic field effect transistor (OFET), and the switching was attributed to the photochromic reaction taking place in the polymer matrix. The present measurements aimed at elucidating the mechanism of the switching by comparing the rate constants of the coloring and bleaching reactions with the rate constants of processes responsible for capacitance changes. The comparison of the rate constants seems to confirm the role of the photochromic process: to within experimental uncertainty the rate constants determined from the two methods are similar. Measurements of the temporal evolution of absorbance additionally reveal existence of an irreversible fatigue reaction, probably associated with admission of oxygen to some samples. The presence of oxygen is also responsible for a deterioration of performance of the OFETs under study.

  8. Poole Frenkel current and Schottky emission in SiN gate dielectric in AlGaN/GaN metal insulator semiconductor heterostructure field effect transistors

    NASA Astrophysics Data System (ADS)

    Hanna, Mina J.; Zhao, Han; Lee, Jack C.

    2012-10-01

    We analyze the anomalous I-V behavior in SiN prepared by plasma enhanced chemical vapor deposition for use as a gate insulator in AlGaN/GaN metal insulator semiconductor heterostructure filed effect transistors (HFETs). We observe leakage current across the dielectric with opposite polarity with respect to the applied electric field once the voltage sweep reaches a level below a determined threshold. This is observed as the absolute minimum of the leakage current does not occur at minimum voltage level (0 V) but occurs earlier in the sweep interval. Curve-fitting analysis suggests that the charge-transport mechanism in this region is Poole-Frenkel current, followed by Schottky emission due to band bending. Despite the current anomaly, the sample devices have shown a notable reduction of leakage current of over 2 to 6 order of magnitudes compared to the standard Schottky HFET. We show that higher pressures and higher silane concentrations produce better films manifesting less trapping. This conforms to our results that we reported in earlier publications. We found that higher chamber pressure achieves higher sheet carrier concentration that was found to be strongly dependent on the trapped space charge at the SiN/GaN interface. This would suggest that a lower chamber pressure induces more trap states into the SiN/GaN interface.

  9. Diamondlike carbon films on semiconductors for insulated-gate technology

    NASA Technical Reports Server (NTRS)

    Kapoor, V. J.; Mirtich, M. J.; Banks, B. A.

    1986-01-01

    MIS structures are fabricated on p-type InP, GaAs, and Si substrated by direct ionization of 25-percent CH4 in Ar and ion-beam deposition of 70-nm-thick diamondlike films, followed by application of Al gate electrodes and ohmic contacts. The films are found to have bandgap 0.9-1.1 eV, resistivity 8.1 Mohm cm, breakdown field strength 1 MV/cm, and density 1.8 g/cu cm, to be thermally stable up to 400 C, and to undergo rapid decomposition above 450 C. The electrical properties of the MIS structures are significantly improved by sputter cleaning the substrates with a 1-keV 2-mA/sq cm Ar beam for 2 min at 300 microtorr prior to C-film deposition. The resulting structures have fixed insulator charge number densities 4 x 10 to the 12th/sq cm (InP), 7.5 x 10 to the 12th/sq cm (GaAs), and 9 x 10 to the 11th/sq cm (Si) and interface state densities (5, 200, and 0.5) x 10 to the 12th/ sq cm eV, respectively. It is suggested that the low optical bandgap and resistivity of the C films and the high insulator-charge and interface-state densities make them unstable as gate dielectrics for microelectronics.

  10. Steep subthreshold swing and energy efficiency in MOSFFETs utilizing nonlinear gate dielectric insulators

    NASA Astrophysics Data System (ADS)

    Ota, Hiroyuki; Migita, Shinji; Fukuda, Koichi; Toriumi, Akira

    2016-04-01

    In this paper, we propose a novel MOSFET in which an ordinary paraelectric insulator is replaced with one in which permittivity is nonlinearly dependent on the electric field. Technology computer-aided design simulation reveals that a variation in the permittivity of the gate insulator in conjunction with a variation in the gate electric field can lead to excellent subthermal subthreshold swings (34 mV/decade), with high on-currents comparable to those of conventional MOSFETs. We also demonstrate the advantages of nonlinear dielectric MOSFETS (NLD-MOSFETs) over conventional MOSFETs by showing a 10-fold shorter intrinsic delay at a supply voltage of 0.2 V.

  11. Chemically gated electronic structure of a superconducting doped topological insulator system

    NASA Astrophysics Data System (ADS)

    Wray, L. A.; Xu, S.; Neupane, M.; Fedorov, A. V.; Hor, Y. S.; Cava, R. J.; Hasan, M. Z.

    2013-07-01

    Angle resolved photoemission spectroscopy is used to observe changes in the electronic structure of bulk-doped topological insulator CuxBi2Se3 as additional copper atoms are deposited onto the cleaved crystal surface. Carrier density and surface-normal electrical field strength near the crystal surface are estimated to consider the effect of chemical surface gating on atypical superconducting properties associated with topological insulator order, such as the dynamics of theoretically predicted Majorana Fermion vortices.

  12. A scheme for a topological insulator field effect transistor

    NASA Astrophysics Data System (ADS)

    Vali, Mehran; Dideban, Daryoosh; Moezi, Negin

    2015-05-01

    We propose a scheme for a topological insulator field effect transistor. The idea is based on the gate voltage control of the Dirac fermions in a ferromagnetic topological insulator channel with perpendicular magnetization connecting to two metallic topological insulator leads. Our theoretical analysis shows that the proposed device displays a switching effect with high on/off current ratio and a negative differential conductance with a good peak to valley ratio.

  13. Atomistic characterization of SAM coatings as gate insulators in Si-based FET devices

    NASA Astrophysics Data System (ADS)

    Gala, F.; Zollo, G.

    2014-06-01

    Many nano-material systems are currently under consideration as possible candidates for gate dielectric insulators in both metal-oxide-semiconductor (MOSFET) and organic (OFET) field-effect transistors. In this contribution, the possibility of employing self-assembled monolayers (SAMs) of hydroxylated octadecyltrichlorosilane (OTS) chains on a (111) Si substrate as gate dielectrics is discussed; in particular ab initio theoretical simulations have been employed to study the structural properties, work function modifications, and the insulating properties of OTS thin film coatings on Si substrates.

  14. Atomistic characterization of SAM coatings as gate insulators in Si-based FET devices

    SciTech Connect

    Gala, F.; Zollo, G.

    2014-06-19

    Many nano-material systems are currently under consideration as possible candidates for gate dielectric insulators in both metal-oxide-semiconductor (MOSFET) and organic (OFET) field-effect transistors. In this contribution, the possibility of employing self-assembled monolayers (SAMs) of hydroxylated octadecyltrichlorosilane (OTS) chains on a (111) Si substrate as gate dielectrics is discussed; in particular ab initio theoretical simulations have been employed to study the structural properties, work function modifications, and the insulating properties of OTS thin film coatings on Si substrates.

  15. Gas insulated transmission line with insulators having field controlling recesses

    DOEpatents

    Cookson, Alan H.; Pederson, Bjorn O.

    1984-01-01

    A gas insulated transmission line having a novel insulator for supporting an inner conductor concentrically within an outer sheath. The insulator has a recess contiguous with the periphery of one of the outer and inner conductors. The recess is disposed to a depth equal to an optimum gap for the dielectric insulating fluid used for the high voltage insulation or alternately disposed to a large depth so as to reduce the field at the critical conductor/insulator interface.

  16. Magnetic gating of a 2D topological insulator.

    PubMed

    Dang, Xiaoqian; Burton, J D; Tsymbal, Evgeny Y

    2016-09-28

    Deterministic control of transport properties through manipulation of spin states is one of the paradigms of spintronics. Topological insulators offer a new playground for exploring interesting spin-dependent phenomena. Here, we consider a ferromagnetic 'gate' representing a magnetic adatom coupled to the topologically protected edge state of a two-dimensional (2D) topological insulator to modulate the electron transmission of the edge state. Due to the locked spin and wave vector of the transport electrons the transmission across the magnetic gate depends on the mutual orientation of the adatom magnetic moment and the current. If the Fermi energy matches an exchange-split bound state of the adatom, the electron transmission can be blocked due to the full back scattering of the incident wave. This antiresonance behavior is controlled by the adatom magnetic moment orientation so that the transmission of the edge state can be changed from 1 to 0. Expanding this consideration to a ferromagnetic gate representing a 1D chain of atoms shows a possibility to control the spin-dependent current of a strip of a 2D topological insulator by magnetization orientation of the ferromagnetic gate. PMID:27437829

  17. Positive-bias gate-controlled metal–insulator transition in ultrathin VO2 channels with TiO2 gate dielectrics

    PubMed Central

    Yajima, Takeaki; Nishimura, Tomonori; Toriumi, Akira

    2015-01-01

    The next generation of electronics is likely to incorporate various functional materials, including those exhibiting ferroelectricity, ferromagnetism and metal–insulator transitions. Metal–insulator transitions can be controlled by electron doping, and so incorporating such a material in transistor channels will enable us to significantly modulate transistor current. However, such gate-controlled metal–insulator transitions have been challenging because of the limited number of electrons accumulated by gate dielectrics, or possible electrochemical reaction in ionic liquid gate. Here we achieve a positive-bias gate-controlled metal–insulator transition near the transition temperature. A significant number of electrons were accumulated via a high-permittivity TiO2 gate dielectric with subnanometre equivalent oxide thickness in the inverse-Schottky-gate geometry. An abrupt transition in the VO2 channel is further exploited, leading to a significant current modulation far beyond the capacitive coupling. This solid-state operation enables us to discuss the electrostatic mechanism as well as the collective nature of gate-controlled metal–insulator transitions, paving the pathway for developing functional field effect transistors. PMID:26657761

  18. Field insulation materials and problems

    NASA Astrophysics Data System (ADS)

    Vogt, G. H.

    1981-12-01

    In a turbine generator the rotating field requires insulation materials and design considerations much different from the high voltage insulation used for armature windings. The principal properties to be looked for are mechanical strength, resistance to abrasion and resistance to thermal degradation. Electrical strength is also important because field windings are required to withstand a high potential test of ten times rated voltage. Some of the materials used over the years ranged from various kinds of fibers and flake mica composites, to asbestos, fiberglass epoxy or polyester laminates, Nomex and combinations of fiberglass, Nomex and insulating films. New materials have been applied to satisfy demands for better properties as generators grew in size and output, and it is the new materials that have made it possible to obtain more power from smaller machines. Field insulation materials and problems are discussed further.

  19. Magnetic gating of a 2D topological insulator

    NASA Astrophysics Data System (ADS)

    Dang, Xiaoqian; Burton, J. D.; Tsymbal, Evgeny Y.

    2016-09-01

    Deterministic control of transport properties through manipulation of spin states is one of the paradigms of spintronics. Topological insulators offer a new playground for exploring interesting spin-dependent phenomena. Here, we consider a ferromagnetic ‘gate’ representing a magnetic adatom coupled to the topologically protected edge state of a two-dimensional (2D) topological insulator to modulate the electron transmission of the edge state. Due to the locked spin and wave vector of the transport electrons the transmission across the magnetic gate depends on the mutual orientation of the adatom magnetic moment and the current. If the Fermi energy matches an exchange-split bound state of the adatom, the electron transmission can be blocked due to the full back scattering of the incident wave. This antiresonance behavior is controlled by the adatom magnetic moment orientation so that the transmission of the edge state can be changed from 1 to 0. Expanding this consideration to a ferromagnetic gate representing a 1D chain of atoms shows a possibility to control the spin-dependent current of a strip of a 2D topological insulator by magnetization orientation of the ferromagnetic gate.

  20. Modelling and extraction procedure for gate insulator and fringing gate capacitance components of an MIS structure

    NASA Astrophysics Data System (ADS)

    Tinoco, J. C.; Martinez-Lopez, A. G.; Lezama, G.; Mendoza-Barrera, C.; Cerdeira, A.; Estrada, M.

    2016-07-01

    CMOS technology has been guided by the continuous reduction of MOS transistors used to fabricate integrated circuits. Additionally, the use of high-k dielectrics as well as a metal gate electrode have promoted the development of nanometric MOS transistors. Under this scenario, the proper modelling of the gate capacitance, with the aim of adequately evaluating the dielectric film thickness, becomes challenging for nanometric metal-insulator-semiconductor (MIS) structures due to the presence of extrinsic fringing capacitance components which affect the total gate capacitance. In this contribution, a complete intrinsic–extrinsic model for gate capacitance under accumulation of an MIS structure, together with an extraction procedure in order to independently determine the different capacitance components, is presented. ATLAS finite element simulation has been used to validate the proposed methodology.

  1. Gate-tuned normal and superconducting transport at the surface of a topological insulator

    PubMed Central

    Sacépé, Benjamin; Oostinga, Jeroen B.; Li, Jian; Ubaldini, Alberto; Couto, Nuno J.G.; Giannini, Enrico; Morpurgo, Alberto F.

    2011-01-01

    Three-dimensional topological insulators are characterized by the presence of a bandgap in their bulk and gapless Dirac fermions at their surfaces. New physical phenomena originating from the presence of the Dirac fermions are predicted to occur, and to be experimentally accessible via transport measurements in suitably designed electronic devices. Here we study transport through superconducting junctions fabricated on thin Bi2Se3 single crystals, equipped with a gate electrode. In the presence of perpendicular magnetic field B, sweeping the gate voltage enables us to observe the filling of the Dirac fermion Landau levels, whose character evolves continuously from electron- to hole-like. When B=0, a supercurrent appears, whose magnitude can be gate tuned, and is minimum at the charge neutrality point determined from the Landau level filling. Our results demonstrate how gated nano-electronic devices give control over normal and superconducting transport of Dirac fermions at an individual surface of a three-dimensional topological insulators. PMID:22146394

  2. Gate-tuned normal and superconducting transport at the surface of a topological insulator.

    PubMed

    Sacépé, Benjamin; Oostinga, Jeroen B; Li, Jian; Ubaldini, Alberto; Couto, Nuno J G; Giannini, Enrico; Morpurgo, Alberto F

    2011-01-01

    Three-dimensional topological insulators are characterized by the presence of a bandgap in their bulk and gapless Dirac fermions at their surfaces. New physical phenomena originating from the presence of the Dirac fermions are predicted to occur, and to be experimentally accessible via transport measurements in suitably designed electronic devices. Here we study transport through superconducting junctions fabricated on thin Bi(2)Se(3) single crystals, equipped with a gate electrode. In the presence of perpendicular magnetic field B, sweeping the gate voltage enables us to observe the filling of the Dirac fermion Landau levels, whose character evolves continuously from electron- to hole-like. When B=0, a supercurrent appears, whose magnitude can be gate tuned, and is minimum at the charge neutrality point determined from the Landau level filling. Our results demonstrate how gated nano-electronic devices give control over normal and superconducting transport of Dirac fermions at an individual surface of a three-dimensional topological insulators. PMID:22146394

  3. Conductance modulation in topological insulator Bi{sub 2}Se{sub 3} thin films with ionic liquid gating

    SciTech Connect

    Son, Jaesung; Banerjee, Karan; Yang, Hyunsoo; Brahlek, Matthew; Koirala, Nikesh; Oh, Seongshik; Lee, Seoung-Ki; Ahn, Jong-Hyun

    2013-11-18

    A Bi{sub 2}Se{sub 3} topological insulator field effect transistor is investigated by using ionic liquid as an electric double layer gating material, leading to a conductance modulation of 365% at room temperature. We discuss the role of charged impurities on the transport properties. The conductance modulation with gate bias is due to a change in the carrier concentration, whereas the temperature dependent conductance change is originated from a change in mobility. Large conductance modulation at room temperature along with the transparent optical properties makes topological insulators as an interesting (opto)electronic material.

  4. Gas-controlled dynamic vacuum insulation with gas gate

    DOEpatents

    Benson, David K.; Potter, Thomas F.

    1994-06-07

    Disclosed is a dynamic vacuum insulation comprising sidewalls enclosing an evacuated chamber and gas control means for releasing hydrogen gas into a chamber to increase gas molecule conduction of heat across the chamber and retrieving hydrogen gas from the chamber. The gas control means includes a metal hydride that absorbs and retains hydrogen gas at cooler temperatures and releases hydrogen gas at hotter temperatures; a hydride heating means for selectively heating the metal hydride to temperatures high enough to release hydrogen gas from the metal hydride; and gate means positioned between the metal hydride and the chamber for selectively allowing hydrogen to flow or not to flow between said metal hydride and said chamber.

  5. Gas-controlled dynamic vacuum insulation with gas gate

    DOEpatents

    Benson, D.K.; Potter, T.F.

    1994-06-07

    Disclosed is a dynamic vacuum insulation comprising sidewalls enclosing an evacuated chamber and gas control means for releasing hydrogen gas into a chamber to increase gas molecule conduction of heat across the chamber and retrieving hydrogen gas from the chamber. The gas control means includes a metal hydride that absorbs and retains hydrogen gas at cooler temperatures and releases hydrogen gas at hotter temperatures; a hydride heating means for selectively heating the metal hydride to temperatures high enough to release hydrogen gas from the metal hydride; and gate means positioned between the metal hydride and the chamber for selectively allowing hydrogen to flow or not to flow between said metal hydride and said chamber. 25 figs.

  6. Duo gating on a 3D topological insulator - independent tuning of both topological surface states

    NASA Astrophysics Data System (ADS)

    Li, Chuan; de Ronde, Bob; Snelder, Marieke; Stehno, Martin; Huang, Yingkai; Golden, Mark; Brinkman, Alexander; ICE Team; IOP Collaboration

    ABSTRACT: Topological insulators are associated with a trove of exciting physics, such as the ability to host robust anyons, Majorana Bound States, which can be used for quantum computation. For future Majorana devices it is desirable to have the Fermi energy tuned as close as possible to the Dirac point of the topological surface state. Based on previous work on gating BSTS, we report the experimental progress towards gate-tuning of the top and bottom topological surface states of BiSbTeSe2 crystal flakes. When the Fermi level is moved across the Dirac point conduction is shown to change from electron dominated transport to hole dominated transport independently for either surface. In the high magnetic field, one can tune the system precisely between the different landau levels of both surfaces, thus a full gating map of the possible landau levels combination is established. In addition, we provide a simple capacitance model to explain the general hysteresis behaviors in topological insulator systems.

  7. Gate-tunable tunneling resistance in graphene/topological insulator vertical junctions

    NASA Astrophysics Data System (ADS)

    Zhang, Liang; Yan, Yuan; Wu, Han-Chun; Liao, Zhi-Min; Yu, Da-Peng

    The emergence of graphene-based vertical heterostructures, especially stacked by various layered materials, opens up new promising possibilities for investigations and applications. The junction based on two famous Dirac materials, graphene and topological insulator, Bi2Se3, can considerably enlarge the family of van der Waals heterostructures, while the experimental approach to obtain controllable interface of these junctions is still a challenge. Here we show the experimental realization of the vertical heterojunction between Bi2Se3 and monolayer graphene. The tunneling-mediated quantum oscillations are identified to arise from several two-dimensional conducting layers. The electrostatic field induced by back gate voltage, as well as the magnetic field, is applied to tailor the available density of states near the Fermi surface. We observe exotic gate-tunable tunneling resistance in high magnetic field, which is attributed to semimetal-quantum Hall insulator transition in the underlying graphene. This work was supported by MOST (Nos. 2013CB934600, 2013CB932602) and NSFC (Nos. 11274014, 11234001).

  8. Gate-Tunable Superconductor-Insulator Transition in Bilayer-Graphene Josephson Junctions

    NASA Astrophysics Data System (ADS)

    Jeong, Dongchan; Lee, Gil-Ho; Doh, Yong-Joo; Lee, Hu-Jong

    2012-02-01

    Bilayer graphene shows opening of electric-field-induced band gap, the size of which is proportional to the intensity of the electric field. We report electronic transport measurements on superconducting proximity effect in planar dual-gated bilayer-graphene Josephson junction with Pb0.93In0.07 (PbIn) electrodes (δPbIn ˜ 1.1meV, Tc = 7.0 K). The junction resistance along the charge-neutral point (CNP) increases as we modulate top- and back-gate voltages away from the zero-gap CNP. The resistive state near the CNP shows a variable-range-hopping-type insulating behavior in R-T curve with lowering temperature crossing the superconducting transition of PbIn electrodes. However, a highly doped regime shows metallic R-T behavior and junction becomes superconducting below Tc. Moreover, magnetic-field-induced Fraunhofer supercurrent modulation, microwave-induced Shapiro steps, and multiple Andreev reflection (MAR) are observed, which indicate the formation of genuine Josephson coupling across the planar junctions below Tc with sufficiently transparent superconductor-bilayer graphene interface. The separatrix of the superconductor-insulator transition corresponds to the square junction conductance of Gsq˜ 6-8e^2/h.

  9. High-mobility BaSnO3 thin-film transistor with HfO2 gate insulator

    NASA Astrophysics Data System (ADS)

    Kim, Young Mo; Park, Chulkwon; Kim, Useong; Ju, Chanjong; Char, Kookrin

    2016-01-01

    Thin-film transistors have been fabricated using La-doped BaSnO3 as n-type channels and (In,Sn)2O3 as source, drain, and gate electrodes. HfO2 was grown as gate insulators by atomic layer deposition. The field-effect mobility, Ion/Ioff ratio, and subthreshold swing of the device are 24.9 cm2 V-1 s-1, 6.0 × 106, and 0.42 V dec-1, respectively. The interface trap density, evaluated to be higher than 1013 cm-2 eV-1, was found to be slightly lower than that of the thin-film transistor with an Al2O3 gate insulator. We attribute the much smaller subthreshold swing values to the higher dielectric constant of HfO2.

  10. Quantum Dot Channel (QDC) FETs with Wraparound II-VI Gate Insulators: Numerical Simulations

    NASA Astrophysics Data System (ADS)

    Jain, F.; Lingalugari, M.; Kondo, J.; Mirdha, P.; Suarez, E.; Chandy, J.; Heller, E.

    2016-08-01

    This paper presents simulations predicting the feasibility of 9-nm wraparound quantum dot channel (QDC) field-effect transistors (FETs). In particular, II-VI lattice-matched layers which reduce the density of interface states, serving as top (tunnel gate), side, and bottom gate insulators, have been simulated. Quantum simulations show FET operation with voltage swing of ~0.2 V. Incorporation of cladded quantum dots, such as SiO x -Si and GeO x -Ge, under the gate tunnel oxide results in electrical transport in one or more quantum dot layers which form a quantum dot superlattice (QDSL). Long-channel QDC FETs have experimental multistate drain current (I D)-gate voltage (V G) and drain current (I D)-drain voltage (V D) characteristics, which can be attributed to the manifestation of extremely narrow energy minibands formed in the QDSL. An approach for modeling the multistate I D-V G characteristics is reported. The multistate characteristics of QDC FETs permit design of compact two-bit multivalued logic circuits.

  11. Electrical Probing of Inherent Spin Polarization in a Topological Insulator with Electrical Gating

    NASA Astrophysics Data System (ADS)

    Lee, Joon Sue; Richardella, Anthony; Samarth, Nitin

    2015-03-01

    The hallmark of a time-reversal symmetry protected three-dimensional topological insulator is the helically spin-textured surface state. Although electrical detection of spin polarization in topological insulators has been demonstrated very recently, there have not been any electrical measurements to demonstrate the entire mapping of the spin polarization throughout the surface state. We report the electrical probing of the spin-polarized surface state using a magnetic tunnel junction as a spin detector while the chemical potential of a topological insulator (Bi,Sb)2Te3 is tuned by back gating. Hysteretic spin signals were observed as the magnetization of the detector ferromagnet (permalloy) switches with in-plane magnetic field. Changing the direction of bias current through the topological insulator channel flips the direction of the spin polarization, resulting in the reverse of sign of the detected spin signals. We demonstrate the control of the Fermi energy, which has importance not only in further understanding of the spin-momentum locking in the surface state but also in possible electrical tuning of the spin polarization for potential spin-based devices. Supported by C-SPIN & DARPA/SRC.

  12. Gate-Tunable Tunneling Resistance in Graphene/Topological Insulator Vertical Junctions.

    PubMed

    Zhang, Liang; Yan, Yuan; Wu, Han-Chun; Yu, Dapeng; Liao, Zhi-Min

    2016-03-22

    Graphene-based vertical heterostructures, particularly stacks incorporated with other layered materials, are promising for nanoelectronics. The stacking of two model Dirac materials, graphene and topological insulator, can considerably enlarge the family of van der Waals heterostructures. Despite good understanding of the two individual materials, the electron transport properties of a combined vertical heterojunction are still unknown. Here, we show the experimental realization of a vertical heterojunction between Bi2Se3 nanoplate and monolayer graphene. At low temperatures, the electron transport through the vertical heterojunction is dominated by the tunneling process, which can be effectively tuned by gate voltage to alter the density of states near the Fermi surface. In the presence of a magnetic field, quantum oscillations are observed due to the quantized Landau levels in both graphene and the two-dimensional surface states of Bi2Se3. Furthermore, we observe an exotic gate-tunable tunneling resistance under high magnetic field, which displays resistance maxima when the underlying graphene becomes a quantum Hall insulator. PMID:26930548

  13. Ultraflexible and ultrathin polymeric gate insulator for 2 V organic transistor circuits

    NASA Astrophysics Data System (ADS)

    Kondo, Masaya; Uemura, Takafumi; Matsumoto, Takafumi; Araki, Teppei; Yoshimoto, Shusuke; Sekitani, Tsuyoshi

    2016-06-01

    We have developed a high-yield process for fabricating organic transistors with ultraflexible and ultrathin polymeric (parylene) insulators. In a top-contact bottom-gate configuration, an oxygen plasma treatment for a Au gate surface before parylene deposition significantly improved the yield of transistors, enabling the parylene thickness to be reduced to 18 nm. Taking full advantage of the ultraflexible and ultrathin insulator, we have demonstrated 2 V ring oscillator circuits, where the yield was 97% for 360 transistors inside the area of 7 × 7 cm2. The highly reliable ultrathin insulator is useful for large-area circuits with low-voltage organic transistors.

  14. Liquid-gated superconductor-insulator transition in an electron-doped cuprate

    NASA Astrophysics Data System (ADS)

    Zeng, Shengwei; Huang, Zhen; Bao, Nina; Lv, Weiming; Liu, Zhiqi; Herng, T. S.; Gopinadhan, K.; Jian, Linke; Ding, J.; Venkatesan, T.; Ariando, Ariando

    2014-03-01

    Doping charge carriers will causes the change of cuprates from antiferromagnetic Mott insulators to high-Tc superconductors. Continuous changing of carrier density is necessary to understand the nature of such phase transition, and thus, further our understanding of cuprate superconductors. Electric field-effect doping, especially with electronic double layer transistors (EDLT) configuration which use ionic liquids (ILs) and polymer electrolyte as the gate dielectrics, is a potential avenue for this investigation and it has been shown its effectiveness in inducing phase transition in strongly correlated electron system. Owing to EDLT, superconductor-to-insulator transition (SIT) has been observed in hole-doped cuprates La2-xSrxCuO4 and YBa2Cu3Oy. Here we use EDLT to tune the carrier density in electron-doped cuprates Pr2-xCexCuO4 ultrathin films and cause the sample evolves from a superconducting state to an insulating state. This present results could be helpful to study SIT between electron- and hole-doped cuprates.

  15. Gate-tuned superconductor-insulator transition in (Li,Fe)OHFeSe

    NASA Astrophysics Data System (ADS)

    Lei, B.; Xiang, Z. J.; Lu, X. F.; Wang, N. Z.; Chang, J. R.; Shang, C.; Zhang, A. M.; Zhang, Q. M.; Luo, X. G.; Wu, T.; Sun, Z.; Chen, X. H.

    2016-02-01

    The antiferromagnetic (AFM) insulator-superconductor transition has always been a center of interest in the underlying physics of unconventional superconductors. However, in the family of iron-based high-Tc superconductors, no intrinsic superconductor-insulator transition has been confirmed so far. Here, we report a first-order transition from superconductor to AFM insulator with a strong charge doping induced by ionic gating in the thin flakes of single crystal (Li,Fe)OHFeSe. The superconducting transition temperature (Tc) is continuously enhanced with electron doping by ionic gating up to a maximum Tc of 43 K, and a striking superconductor-insulator transition occurs just at the verge of optimal doping with highest Tc. A phase diagram of temperature-gating voltage with the superconductor-insulator transition is mapped out, indicating that the superconductor-insulator transition is a common feature for unconventional superconductivity. These results help to uncover the underlying physics of iron-based superconductivity as well as the universal mechanism of high-Tc superconductivity. Our finding also suggests that the gate-controlled strong charge doping makes it possible to explore novel states of matter in a way beyond traditional methods.

  16. Gate-Tunable Superconducting-Insulating Transition in Tin-Decorated Graphene

    NASA Astrophysics Data System (ADS)

    Bouchiat, Vincent; Han, Zheng; Allain, Adrien

    2012-02-01

    We report the measurement of electrostatically tuned superconducting-insulating transition in macroscopic, CVD-Grown samples of graphene which decorated with tin nanoparticles. The self assembled network of Tin islands generates superconducting correlations locally in the Graphene by means of proximity effect. Correlations eventually leads to percolation of a supercurrent This system exhibits features related to granular superconductivity, a giant magnetoresistance peak, as well as an intermediate metallic behavior. We emphasize outstanding dynamics of the transition, which exhibit a change in resistance of more than 7 orders of magnitude within 40V of gate voltage, thus realizing a real electrostatically driven superconducting-insulating transition. The intense positive magnetoresistance observed for fields below the critical field of Tin nanoparticles is a signature of the localization of Cooper pairs. This hybrid superconductor provides a model system to better understand the physics of inhomogeneous superconductivity, as crossing the transition by adjusting the carrier density is conceptually simpler than using a magnetic field. It also allows to cross the transition continuously and under constant disorder.

  17. Topological insulator Bi2Te3 nanowire field effect devices

    NASA Astrophysics Data System (ADS)

    Jauregui, Luis A.; Zhang, Genqiang; Wu, Yue; Chen, Yong P.

    2012-02-01

    Bismuth telluride (Bi2Te3) has been studied extensively as one of the best thermoelectric materials and recently shown to be a prototype topological insulator with nontrivial conducting surface states. We have grown Bi2Te3 nanowires by a two-step solution phase reaction and characterized their material and structural properties by XRD, TEM, XPS and EDS. We fabricate both backgated (on SiO2/Si) and top-gated (with ALD high-k gate dielectric such as Al2O3 or HfO2) field effect devices on such nanowires with diameters ˜50nm. Ambipolar field effect and a resistance modulation of up to 600% at low temperatures have been observed. The 4-terminal resistance shows insulating behavior (increasing with decreasing temperature) from 300 K to 50K, then saturates in a plateau for temperatures below 50K, consistent with the presence of metallic surface state. Aharonov--Bohm (AB) oscillations are observed in the magneto-resistance with a magnetic field parallel to the nanowire, providing further evidence of the presence of surface state conduction Finally, a prominent weak anti-localization (WAL) feature that weakens with increasing magnetic field and/or temperature is observed in the magneto-resistance with a magnetic field perpendicular to the nanowire.

  18. A high-conductivity insulated gate bipolar transistor with Schottky hole barrier contact

    NASA Astrophysics Data System (ADS)

    Mengxuan, Jiang; John, Shen Z.; Jun, Wang; Xin, Yin; Zhikang, Shuai; Jiang, Lu

    2016-02-01

    This letter proposes a high-conductivity insulated gate bipolar transistor (HC-IGBT) with Schottky contact formed on the p-base, which forms a hole barrier at the p-base side to enhance the conductivity modulation effect. TCAD simulation shows that the HC-IGBT provides a current density increase by 53% and turn-off losses decrease by 27% when compared to a conventional field-stop IGBT (FS-IGBT). Hence, the proposed IGBT exhibits superior electrical performance for high-efficiency power electronic systems. Project supported by the National High Technology Research and Development Program of China (No. 2014AA052601) and the National Natural Science Foundation of China (No. 51277060).

  19. Tuning the metal-insulator crossover and magnetism in SrRuO3 by ionic gating

    DOE PAGESBeta

    Yi, Hee Taek; Gao, Bin; Xie, Wei; Cheong, Sang -Wook; Podzorov, Vitaly

    2014-10-13

    Reversible control of charge transport and magnetic properties without degradation is a key for device applications of transition metal oxides. Chemical doping during the growth of transition metal oxides can result in large changes in physical properties, but in most of the cases irreversibility is an inevitable constraint. We report a reversible control of charge transport, metal-insulator crossover and magnetism in field-effect devices based on ionically gated archetypal oxide system - SrRuO3. In these thin-film devices, the metal-insulator crossover temperature and the onset of magnetoresistance can be continuously and reversibly tuned in the range 90–250 K and 70–100 K, respectively,more » by application of a small gate voltage. We infer that a reversible diffusion of oxygen ions in the oxide lattice dominates the response of these materials to the gate electric field. These findings provide critical insights into both the understanding of ionically gated oxides and the development of novel applications.« less

  20. Tuning the metal-insulator crossover and magnetism in SrRuO3 by ionic gating

    SciTech Connect

    Yi, Hee Taek; Gao, Bin; Xie, Wei; Cheong, Sang -Wook; Podzorov, Vitaly

    2014-10-13

    Reversible control of charge transport and magnetic properties without degradation is a key for device applications of transition metal oxides. Chemical doping during the growth of transition metal oxides can result in large changes in physical properties, but in most of the cases irreversibility is an inevitable constraint. We report a reversible control of charge transport, metal-insulator crossover and magnetism in field-effect devices based on ionically gated archetypal oxide system - SrRuO3. In these thin-film devices, the metal-insulator crossover temperature and the onset of magnetoresistance can be continuously and reversibly tuned in the range 90–250 K and 70–100 K, respectively, by application of a small gate voltage. We infer that a reversible diffusion of oxygen ions in the oxide lattice dominates the response of these materials to the gate electric field. These findings provide critical insights into both the understanding of ionically gated oxides and the development of novel applications.

  1. A Study on Metal-Insulator-Silicon Hydrogen Sensor with LaTiON as Gate Insulator

    NASA Astrophysics Data System (ADS)

    Chen, Gang; Yu, Jerry; Lai, P. T.

    Amongst the many types of semiconductor hydrogen sensors currently studied, Schottky-diodes are preferable as they are simple to fabricate and exhibit high sensitivities and fast response times. To enhance the sensor's performance, a gate insulator is deposited in order to minimize interfacial diffusion between the electrode and the substrate. In this work, we present a novel MIS Schottky-diode hydrogen sensor with LaTiON as gate insulator. The hydrogen-sensing properties (sensitivity, barrier height variation) were examined from room temperature (RT) to 150 °C and its sensitivity was found to reach 2.5 at 100 °C. Moreover, the hydrogen reaction kinetics were studied and these results showed that the sensor was very sensitive to hydrogen ambient.

  2. Combined gate-tunable Josephson junctions and normal state transport in Bi2Te3 topological insulator thin films

    NASA Astrophysics Data System (ADS)

    Ngabonziza, Prosper; Stehno, Martin, P.; Myoren, Hiroaki; Brinkman, Alexander

    In recent years, extensive efforts have been made to improve the coupling between topological insulators and s-wave superconductors in topological insulator Josephson devices (TIJDs). Despite significant progress, essential questions remain open such as the bulk contribution to the Josephson critical current or the existence (and number) of 4 π -periodic bound states (Majoranas) in TIJDs. To address these issues, we fabricated Nb/Bi2Te3/Nb Josephson junctions alongside Hall bar devices on MBE-grown Bi2Te3 topological insulator thin films. Using the SrTiO3 [111] substrate as a gate dielectric, we tuned the carrier density electrostatically and measured the Josephson supercurrent and the normal state transport properties of our thin film devices. We identify three gate voltage ranges with distinct behavior: A region of intermediate gate bias where the measured quantities change rapidly with the applied electric field, and two saturation regions for large bias of either polarity. We discuss carrier distribution and band alignment in the material as well as implications for the effective Josephson coupling in TIJDs. This work is financially supported by the Dutch Foundation for Fundamental Research on Matter (FOM), the Netherlands Organization for Scientific Research (NWO), and by the European Research Council (ERC).

  3. Controllable Hysteresis and Threshold Voltage of Single-Walled Carbon Nano-tube Transistors with Ferroelectric Polymer Top-Gate Insulators

    NASA Astrophysics Data System (ADS)

    Sun, Yi-Lin; Xie, Dan; Xu, Jian-Long; Zhang, Cheng; Dai, Rui-Xuan; Li, Xian; Meng, Xiang-Jian; Zhu, Hong-Wei

    2016-03-01

    Double-gated field effect transistors have been fabricated using the SWCNT networks as channel layer and the organic ferroelectric P(VDF-TrFE) film spin-coated as top gate insulators. Standard photolithography process has been adopted to achieve the patterning of organic P(VDF-TrFE) films and top-gate electrodes, which is compatible with conventional CMOS process technology. An effective way for modulating the threshold voltage in the channel of P(VDF-TrFE) top-gate transistors under polarization has been reported. The introduction of functional P(VDF-TrFE) gate dielectric also provides us an alternative method to suppress the initial hysteresis of SWCNT networks and obtain a controllable ferroelectric hysteresis behavior. Applied bottom gate voltage has been found to be another effective way to highly control the threshold voltage of the networked SWCNTs based FETs by electrostatic doping effect.

  4. Controllable Hysteresis and Threshold Voltage of Single-Walled Carbon Nano-tube Transistors with Ferroelectric Polymer Top-Gate Insulators.

    PubMed

    Sun, Yi-Lin; Xie, Dan; Xu, Jian-Long; Zhang, Cheng; Dai, Rui-Xuan; Li, Xian; Meng, Xiang-Jian; Zhu, Hong-Wei

    2016-01-01

    Double-gated field effect transistors have been fabricated using the SWCNT networks as channel layer and the organic ferroelectric P(VDF-TrFE) film spin-coated as top gate insulators. Standard photolithography process has been adopted to achieve the patterning of organic P(VDF-TrFE) films and top-gate electrodes, which is compatible with conventional CMOS process technology. An effective way for modulating the threshold voltage in the channel of P(VDF-TrFE) top-gate transistors under polarization has been reported. The introduction of functional P(VDF-TrFE) gate dielectric also provides us an alternative method to suppress the initial hysteresis of SWCNT networks and obtain a controllable ferroelectric hysteresis behavior. Applied bottom gate voltage has been found to be another effective way to highly control the threshold voltage of the networked SWCNTs based FETs by electrostatic doping effect. PMID:26980284

  5. Controllable Hysteresis and Threshold Voltage of Single-Walled Carbon Nano-tube Transistors with Ferroelectric Polymer Top-Gate Insulators

    PubMed Central

    Sun, Yi-Lin; Xie, Dan; Xu, Jian-Long; Zhang, Cheng; Dai, Rui-Xuan; Li, Xian; Meng, Xiang-Jian; Zhu, Hong-Wei

    2016-01-01

    Double-gated field effect transistors have been fabricated using the SWCNT networks as channel layer and the organic ferroelectric P(VDF-TrFE) film spin-coated as top gate insulators. Standard photolithography process has been adopted to achieve the patterning of organic P(VDF-TrFE) films and top-gate electrodes, which is compatible with conventional CMOS process technology. An effective way for modulating the threshold voltage in the channel of P(VDF-TrFE) top-gate transistors under polarization has been reported. The introduction of functional P(VDF-TrFE) gate dielectric also provides us an alternative method to suppress the initial hysteresis of SWCNT networks and obtain a controllable ferroelectric hysteresis behavior. Applied bottom gate voltage has been found to be another effective way to highly control the threshold voltage of the networked SWCNTs based FETs by electrostatic doping effect. PMID:26980284

  6. Radiation hardening of MOS devices by boron. [for stabilizing gate threshold potential of field effect device

    NASA Technical Reports Server (NTRS)

    Danchenko, V. (Inventor)

    1974-01-01

    A technique is described for radiation hardening of MOS devices and specifically for stabilizing the gate threshold potential at room temperature of a radiation subjected MOS field-effect device with a semiconductor substrate, an insulating layer of oxide on the substrate, and a gate electrode disposed on the insulating layer. The boron is introduced within a layer of the oxide of about 100 A-300 A thickness immediately adjacent the semiconductor-insulator interface. The concentration of boron in the oxide layer is preferably maintained on the order of 10 to the 18th power atoms/cu cm. The technique serves to reduce and substantially annihilate radiation induced positive gate charge accumulations.

  7. Giant reversible, facet-dependent, structural changes in a correlated-electron insulator induced by ionic liquid gating.

    PubMed

    Jeong, Jaewoo; Aetukuri, Nagaphani B; Passarello, Donata; Conradson, Steven D; Samant, Mahesh G; Parkin, Stuart S P

    2015-01-27

    The use of electric fields to alter the conductivity of correlated electron oxides is a powerful tool to probe their fundamental nature as well as for the possibility of developing novel electronic devices. Vanadium dioxide (VO2) is an archetypical correlated electron system that displays a temperature-controlled insulating to metal phase transition near room temperature. Recently, ionic liquid gating, which allows for very high electric fields, has been shown to induce a metallic state to low temperatures in the insulating phase of epitaxially grown thin films of VO2. Surprisingly, the entire film becomes electrically conducting. Here, we show, from in situ synchrotron X-ray diffraction and absorption experiments, that the whole film undergoes giant, structural changes on gating in which the lattice expands by up to ∼3% near room temperature, in contrast to the 10 times smaller (∼0.3%) contraction when the system is thermally metallized. Remarkably, these structural changes are fully reversible on reverse gating. Moreover, we find these structural changes and the concomitant metallization are highly dependent on the VO2 crystal facet, which we relate to the ease of electric-field-induced motion of oxygen ions along chains of edge-sharing VO6 octahedra that exist along the (rutile) c axis. PMID:25583517

  8. Giant reversible, facet-dependent, structural changes in a correlated-electron insulator induced by ionic liquid gating

    PubMed Central

    Jeong, Jaewoo; Aetukuri, Nagaphani B.; Passarello, Donata; Conradson, Steven D.; Samant, Mahesh G.; Parkin, Stuart S. P.

    2015-01-01

    The use of electric fields to alter the conductivity of correlated electron oxides is a powerful tool to probe their fundamental nature as well as for the possibility of developing novel electronic devices. Vanadium dioxide (VO2) is an archetypical correlated electron system that displays a temperature-controlled insulating to metal phase transition near room temperature. Recently, ionic liquid gating, which allows for very high electric fields, has been shown to induce a metallic state to low temperatures in the insulating phase of epitaxially grown thin films of VO2. Surprisingly, the entire film becomes electrically conducting. Here, we show, from in situ synchrotron X-ray diffraction and absorption experiments, that the whole film undergoes giant, structural changes on gating in which the lattice expands by up to ∼3% near room temperature, in contrast to the 10 times smaller (∼0.3%) contraction when the system is thermally metallized. Remarkably, these structural changes are fully reversible on reverse gating. Moreover, we find these structural changes and the concomitant metallization are highly dependent on the VO2 crystal facet, which we relate to the ease of electric-field–induced motion of oxygen ions along chains of edge-sharing VO6 octahedra that exist along the (rutile) c axis. PMID:25583517

  9. Quantum transport of two-species Dirac fermions in dual-gated three-dimensional topological insulators

    DOE PAGESBeta

    Xu, Yang; Miotkowski, Ireneusz; Chen, Yong P.

    2016-05-04

    Topological insulators are a novel class of quantum matter with a gapped insulating bulk, yet gapless spin-helical Dirac fermion conducting surface states. Here, we report local and non-local electrical and magneto transport measurements in dual-gated BiSbTeSe2 thin film topological insulator devices, with conduction dominated by the spatially separated top and bottom surfaces, each hosting a single species of Dirac fermions with independent gate control over the carrier type and density. We observe many intriguing quantum transport phenomena in such a fully tunable two-species topological Dirac gas, including a zero-magnetic-field minimum conductivity close to twice the conductance quantum at the doublemore » Dirac point, a series of ambipolar two-component half-integer Dirac quantum Hall states and an electron-hole total filling factor zero state (with a zero-Hall plateau), exhibiting dissipationless (chiral) and dissipative (non-chiral) edge conduction, respectively. As a result, such a system paves the way to explore rich physics, ranging from topological magnetoelectric effects to exciton condensation.« less

  10. Quantum transport of two-species Dirac fermions in dual-gated three-dimensional topological insulators.

    PubMed

    Xu, Yang; Miotkowski, Ireneusz; Chen, Yong P

    2016-01-01

    Topological insulators are a novel class of quantum matter with a gapped insulating bulk, yet gapless spin-helical Dirac fermion conducting surface states. Here, we report local and non-local electrical and magneto transport measurements in dual-gated BiSbTeSe2 thin film topological insulator devices, with conduction dominated by the spatially separated top and bottom surfaces, each hosting a single species of Dirac fermions with independent gate control over the carrier type and density. We observe many intriguing quantum transport phenomena in such a fully tunable two-species topological Dirac gas, including a zero-magnetic-field minimum conductivity close to twice the conductance quantum at the double Dirac point, a series of ambipolar two-component half-integer Dirac quantum Hall states and an electron-hole total filling factor zero state (with a zero-Hall plateau), exhibiting dissipationless (chiral) and dissipative (non-chiral) edge conduction, respectively. Such a system paves the way to explore rich physics, ranging from topological magnetoelectric effects to exciton condensation. PMID:27142344

  11. Quantum transport of two-species Dirac fermions in dual-gated three-dimensional topological insulators

    PubMed Central

    Xu, Yang; Miotkowski, Ireneusz; Chen, Yong P.

    2016-01-01

    Topological insulators are a novel class of quantum matter with a gapped insulating bulk, yet gapless spin-helical Dirac fermion conducting surface states. Here, we report local and non-local electrical and magneto transport measurements in dual-gated BiSbTeSe2 thin film topological insulator devices, with conduction dominated by the spatially separated top and bottom surfaces, each hosting a single species of Dirac fermions with independent gate control over the carrier type and density. We observe many intriguing quantum transport phenomena in such a fully tunable two-species topological Dirac gas, including a zero-magnetic-field minimum conductivity close to twice the conductance quantum at the double Dirac point, a series of ambipolar two-component half-integer Dirac quantum Hall states and an electron-hole total filling factor zero state (with a zero-Hall plateau), exhibiting dissipationless (chiral) and dissipative (non-chiral) edge conduction, respectively. Such a system paves the way to explore rich physics, ranging from topological magnetoelectric effects to exciton condensation. PMID:27142344

  12. Gate induced superconductivity in layered material based electronic double layer field effect transistors

    NASA Astrophysics Data System (ADS)

    Ye, J. T.; Inoue, S.; Kobayashi, K.; Kasahara, Y.; Yuan, H. T.; Shimotani, H.; Iwasa, Y.

    2010-12-01

    Applying the principle of field effect transistor to layered materials provides new opportunities to manipulate their electronic properties for interesting sciences and applications. Novel gate dielectrics like electronic double layer (EDL) formed by ionic liquids are demonstrated to achieve an electrostatic surface charge accumulation on the order of 1014 cm-2. To realize electric field-induced superconductivity, we chose a layered compound: ZrNCl, which is known to be superconducting by introducing electrons through intercalation of alkali metals into the van der Waals gaps. A ZrNCl-based EDL transistor was micro fabricated on a thin ZrNCl single crystal made by mechanical micro-cleavage. Accumulating charges using EDL gate dielectrics onto the channel surface of ZrNCl shows effective field effect modulation of its electronic properties. Sheet resistance of ZrNCl EDL transistor is reduced by applying a gate voltage from 0 to 4.5 V. Temperature dependence of sheet resistance showed clear evidence of metal-insulator transition upon gating, observed at a gate voltage higher than 3.5 V. Furthermore, gate-induced superconductivity took place after metal-insulator transition when the transistor is cooled down to about 15 K.

  13. Novel trench gate field stop IGBT with trench shorted anode

    NASA Astrophysics Data System (ADS)

    Xudong, Chen; Jianbing, Cheng; Guobing, Teng; Houdong, Guo

    2016-05-01

    A novel trench field stop (FS) insulated gate bipolar transistor (IGBT) with a trench shorted anode (TSA) is proposed. By introducing a trench shorted anode, the TSA-FS-IGBT can obviously improve the breakdown voltage. As the simulation results show, the breakdown voltage is improved by a factor of 19.5% with a lower leakage current compared with the conventional FS-IGBT. The turn off time of the proposed structure is 50% lower than the conventional one with less than 9% voltage drop increased at a current density of 150 A/cm2. Additionally, there is no snapback observed. As a result, the TSA-FS-IGBT has a better trade-off relationship between the turn off loss and forward drop. Project supported by the National Natural Science Foundation of China (No. 61274080) and the Postdoctoral Science Foundation of China (No. 2013M541585).

  14. High-Mobility Holes in Dual-Gated WSe2 Field-Effect Transistors.

    PubMed

    Movva, Hema C P; Rai, Amritesh; Kang, Sangwoo; Kim, Kyounghwan; Fallahazad, Babak; Taniguchi, Takashi; Watanabe, Kenji; Tutuc, Emanuel; Banerjee, Sanjay K

    2015-10-27

    We demonstrate dual-gated p-type field-effect transistors (FETs) based on few-layer tungsten diselenide (WSe2) using high work-function platinum source/drain contacts and a hexagonal boron nitride top-gate dielectric. A device topology with contacts underneath the WSe2 results in p-FETs with ION/IOFF ratios exceeding 10(7) and contacts that remain ohmic down to cryogenic temperatures. The output characteristics show current saturation and gate tunable negative differential resistance. The devices show intrinsic hole mobilities around 140 cm(2)/(V s) at room temperature and approaching 4000 cm(2)/(V s) at 2 K. Temperature-dependent transport measurements show a metal-insulator transition, with an insulating phase at low densities and a metallic phase at high densities. The mobility shows a strong temperature dependence consistent with phonon scattering, and saturates at low temperatures, possibly limited by Coulomb scattering or defects. PMID:26343531

  15. Extremely large, gate tunable spin Hall angle in 3D Topological Insulator pn junction

    NASA Astrophysics Data System (ADS)

    Habib, K. M. Masum; Sajjad, Redwan; Ghosh, Avik

    2015-03-01

    The band structure of the surface states of a three dimensional Topological Insulator (3D TI) is similar to that of graphene featuring massless Dirac Fermions. We show that due to this similarity, the chiral tunneling of electron in a graphene pn junction also appears in 3D TI. Electrons with very small incident angle (modes) are allowed to transmit through a TI pn junction (TIPNJ) due to the chiral tunneling. The rest of the electrons are reflected. As a result, the charge current in a TIPNJ is suppressed. Due to the spin momentum locking, all the small angle modes are spin-down states. Therefore, the transmitted end of the TIPNJ becomes highly spin polarized. On the other hand, the spin of the reflected electron is flipped due to spin momentum locking. This enhances the spin current at the injection end. Thus, the interplay between the chiral tunneling and spin momentum locking reduces the charge current but enhances the spin current at the same time, leading to an extremely large (~20) spin Hall angle. Since the chiral tunneling can be controlled by an external electric field, the spin Hall angle is gate tunable. The spin current generated by a TIPNJ can be used for energy-efficient switching of nanoscaled ferromagnets, which is an essential part of spintronic devices. This work is supported by the NRI INDEX center.

  16. Electric field-induced superconducting transition of insulating FeSe thin film at 35 K

    NASA Astrophysics Data System (ADS)

    Hanzawa, Kota; Sato, Hikaru; Hiramatsu, Hidenori; Kamiya, Toshio; Hosono, Hideo

    2016-04-01

    It is thought that strong electron correlation in an insulating parent phase would enhance a critical temperature (Tc) of superconductivity in a doped phase via enhancement of the binding energy of a Cooper pair as known in high-Tc cuprates. To induce a superconductor transition in an insulating phase, injection of a high density of carriers is needed (e.g., by impurity doping). An electric double-layer transistor (EDLT) with an ionic liquid gate insulator enables such a field-induced transition to be investigated and is expected to result in a high Tc because it is free from deterioration in structure and carrier transport that are in general caused by conventional carrier doping (e.g., chemical substitution). Here, for insulating epitaxial thin films (∼10 nm thick) of FeSe, we report a high Tc of 35 K, which is 4× higher than that of bulk FeSe, using an EDLT under application of a gate bias of +5.5 V. Hall effect measurements under the gate bias suggest that highly accumulated electron carrier in the channel, whose area density is estimated to be 1.4 × 1015 cm-2 (the average volume density of 1.7 × 1021 cm-3), is the origin of the high-Tc superconductivity. This result demonstrates that EDLTs are useful tools to explore the ultimate Tc for insulating parent materials.

  17. Electric field-induced superconducting transition of insulating FeSe thin film at 35 K.

    PubMed

    Hanzawa, Kota; Sato, Hikaru; Hiramatsu, Hidenori; Kamiya, Toshio; Hosono, Hideo

    2016-04-12

    It is thought that strong electron correlation in an insulating parent phase would enhance a critical temperature (Tc) of superconductivity in a doped phase via enhancement of the binding energy of a Cooper pair as known in high-Tc cuprates. To induce a superconductor transition in an insulating phase, injection of a high density of carriers is needed (e.g., by impurity doping). An electric double-layer transistor (EDLT) with an ionic liquid gate insulator enables such a field-induced transition to be investigated and is expected to result in a high Tc because it is free from deterioration in structure and carrier transport that are in general caused by conventional carrier doping (e.g., chemical substitution). Here, for insulating epitaxial thin films (∼10 nm thick) of FeSe, we report a high Tc of 35 K, which is 4× higher than that of bulk FeSe, using an EDLT under application of a gate bias of +5.5 V. Hall effect measurements under the gate bias suggest that highly accumulated electron carrier in the channel, whose area density is estimated to be 1.4 × 10(15) cm(-2) (the average volume density of 1.7 × 10(21) cm(-3)), is the origin of the high-Tc superconductivity. This result demonstrates that EDLTs are useful tools to explore the ultimate Tc for insulating parent materials. PMID:27035956

  18. Field calibration of submerged sluice gates in irrigation canals

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Four rectangular sluice gates were calibrated for submerged-flow conditions using nearly 16,000 field-measured data points on Canal B of the B-XII irrigation scheme in Lebrija, Spain. Water depth and gate opening values were measured using acoustic sensors at each of the gate structures, and the dat...

  19. Control of threshold voltage in E-mode and D-mode GaN-on-Si metal-insulator-semiconductor heterostructure field effect transistors by in-situ fluorine doping of atomic layer deposition Al2O3 gate dielectrics

    NASA Astrophysics Data System (ADS)

    Roberts, J. W.; Chalker, P. R.; Lee, K. B.; Houston, P. A.; Cho, S. J.; Thayne, I. G.; Guiney, I.; Wallis, D.; Humphreys, C. J.

    2016-02-01

    We report the modification and control of threshold voltage in enhancement and depletion mode AlGaN/GaN metal-insulator-semiconductor heterostructure field effect transistors through the use of in-situ fluorine doping of atomic layer deposition Al2O3. Uniform distribution of F ions throughout the oxide thickness are achievable, with a doping level of up to 5.5 × 1019 cm-3 as quantified by secondary ion mass spectrometry. This fluorine doping level reduces capacitive hysteretic effects when exploited in GaN metal-oxide-semiconductor capacitors. The fluorine doping and forming gas anneal also induces an average positive threshold voltage shift of between 0.75 and 1.36 V in both enhancement mode and depletion mode GaN-based transistors compared with the undoped gate oxide via a reduction of positive fixed charge in the gate oxide from +4.67 × 1012 cm-2 to -6.60 × 1012 cm-2. The application of this process in GaN based power transistors advances the realisation of normally off, high power, high speed devices.

  20. Demonstration of hetero-gate-dielectric tunneling field-effect transistors (HG TFETs)

    NASA Astrophysics Data System (ADS)

    Choi, Woo Young; Lee, Hyun Kook

    2016-06-01

    The steady scaling-down of semiconductor device for improving performance has been the most important issue among researchers. Recently, as low-power consumption becomes one of the most important requirements, there have been many researches about novel devices for low-power consumption. Though scaling supply voltage is the most effective way for low-power consumption, performance degradation is occurred for metal-oxide-semiconductor field-effect transistors (MOSFETs) when supply voltage is reduced because subthreshold swing (SS) of MOSFETs cannot be lower than 60 mV/dec. Thus, in this thesis, hetero-gate-dielectric tunneling field-effect transistors (HG TFETs) are investigated as one of the most promising alternatives to MOSFETs. By replacing source-side gate insulator with a high- k material, HG TFETs show higher on-current, suppressed ambipolar current and lower SS than conventional TFETs. Device design optimization through simulation was performed and fabrication based on simulation demonstrated that performance of HG TFETs were better than that of conventional TFETs. Especially, enlargement of gate insulator thickness while etching gate insulator at the source side was improved by introducing HF vapor etch process. In addition, the proposed HG TFETs showed higher performance than our previous results by changing structure of sidewall spacer by high- k etching process.

  1. Quantum and Classical Magnetoresistance in Ambipolar Topological Insulator Transistors with Gate-tunable Bulk and Surface Conduction

    PubMed Central

    Tian, Jifa; Chang, Cuizu; Cao, Helin; He, Ke; Ma, Xucun; Xue, Qikun; Chen, Yong P.

    2014-01-01

    Weak antilocalization (WAL) and linear magnetoresistance (LMR) are two most commonly observed magnetoresistance (MR) phenomena in topological insulators (TIs) and often attributed to the Dirac topological surface states (TSS). However, ambiguities exist because these phenomena could also come from bulk states (often carrying significant conduction in many TIs) and are observable even in non-TI materials. Here, we demonstrate back-gated ambipolar TI field-effect transistors in (Bi0.04Sb0.96)2Te3 thin films grown by molecular beam epitaxy on SrTiO3(111), exhibiting a large carrier density tunability (by nearly 2 orders of magnitude) and a metal-insulator transition in the bulk (allowing switching off the bulk conduction). Tuning the Fermi level from bulk band to TSS strongly enhances both the WAL (increasing the number of quantum coherent channels from one to peak around two) and LMR (increasing its slope by up to 10 times). The SS-enhanced LMR is accompanied by a strongly nonlinear Hall effect, suggesting important roles of charge inhomogeneity (and a related classical LMR), although existing models of LMR cannot capture all aspects of our data. Our systematic gate and temperature dependent magnetotransport studies provide deeper insights into the nature of both MR phenomena and reveal differences between bulk and TSS transport in TI related materials. PMID:24810663

  2. Structural and metal-insulator transitions in ionic liquid-gated Ca3Ru2O7 surface

    NASA Astrophysics Data System (ADS)

    Puls, Conor P.; Cai, Xinxin; Zhang, Yuhe; Peng, Jin; Mao, Zhiqiang; Liu, Ying

    2014-06-01

    We report the fabrication and measurements of ionic liquid gated Hall bar devices prepared on the ab face of a thin Ca3Ru2O7 flake exfoliated from bulk single crystals that were grown by a floating zone method. The devices were categorized into two types: those with their electrical transport properties dominated by c-axis transport in type A or that of the in-plane in type B devices. Bulk physical phenomena, including a magnetic transition near 56 K, a structural and metal-insulator transition at a slightly lower temperature, as well as the emergence of a highly unusual metallic state as the temperature is further lowered, were found in both types of devices. However, the Shubnikov-de Haas oscillations were found in type A but not type B devices, most likely due to enhanced disorder on the flake surface. Finally, the ionic liquid gating of a type B device revealed a shift in critical temperature of the structural and metal-insulator transition, suggesting that this transition is tunable by the electric field effect.

  3. Quantum transport of two-species Dirac fermions in dual-gated three-dimensional topological insulators

    NASA Astrophysics Data System (ADS)

    Xu, Yang; Miotkowski, Ireneusz; Chen, Yong P.

    Topological insulators (TI) are a novel class of quantum matter with a gapped insulating bulk yet gapless spin helical Dirac fermion conducting surface states. Here, we report local and non-local electrical and magneto transport measurements in dual-gated BiSbTeSe2 thin film TI devices, with conduction dominated by the spatially separated top and bottom surfaces, each hosting a single species of Dirac fermions with independent gate control over the carrier type and density. We observe many intriguing quantum transport phenomena in such a fully-tunable two-species topological Dirac gas, including a zero-magnetic-field minimum conductivity of 4e2 / h at the double Dirac point, a series of ambipolar two-component ''half-integer'' Dirac quantum Hall states and an electron-hole total filling factor ν=0 state (with a zero-Hall plateau), exhibiting dissipationless (chiral) and dissipative (non-chiral) edge conduction respectively. Such a system paves the way to explore rich physics ranging from topological magnetoelectric effects to exciton condensation. DARPA MESO program.

  4. Retention and Switching Kinetics of Protonated Gate Field Effect Transistors

    SciTech Connect

    DEVINE,R.A.B.; HERRERA,GILBERT V.

    2000-06-27

    The switching and memory retention time has been measured in 50 {micro}m gatelength pseudo-non-volatile memory MOSFETs containing, protonated 40 nm gate oxides. Times of the order of 3.3 seconds are observed for fields of 3 MV cm{sup {minus}1}. The retention time with protons placed either at the gate oxide/substrate or gate oxide/gate electrode interfaces is found to better than 96% after 5,000 seconds. Measurement of the time dependence of the source-drain current during switching provides clear evidence for the presence of dispersive proton transport through the gate oxide.

  5. Retention and switching kinetics of protonated gate field effect transistors

    SciTech Connect

    DEVINE,R.A.B.; HERRERA,GILBERT V.

    2000-05-23

    The switching and memory retention time has been measured in 50 {micro}m gatelength pseudo-non-volatile memory MOSFETS containing, protonated 40 nm gate oxides. Times of the order of 3.3 seconds are observed for fields of 3 MV cm{sup {minus}1}. The retention time with protons placed either at the gate oxide/substrate or gate oxide/gate electrode interfaces is found to better than 96{percent} after 5,000 seconds. Measurement of the time dependence of the source-drain current during switching provides clear evidence for the presence of dispersive proton transport through the gate oxide.

  6. Unconventional band structure for a periodically gated surface of a three dimensional Topological Insulator

    NASA Astrophysics Data System (ADS)

    Ghosh, Sankalpa; Mondal, Puja

    The surface states of the three dimensional (3D) Topological Insulators are described by two-dimensional (2D) massless dirac equation. A gate voltage induced one dimensional potential barrier on such surface creates a discrete bound state in the forbidden region outside the dirac cone. Even for a single barrier it is shown such bound state can create electrostatic analogue of Shubnikov de Haas oscillation which can be experimentally observed for relatively smaller size samples. However when these surface states are exposed to a periodic arrangement of such gate voltage induced potential barriers, the band structure of the same got nontrivially modified. This is expected to significantly alters the properties of macroscopic system. We also suggest that in suitable limit the system may offer ways to control electron spin electrostatically which may be practically useful Supported by UGC Fellowship (PM) and a UKIERI-UGC Thematic Partnership.

  7. Unconventional band structure for a periodically gated surface of a three-dimensional topological insulator

    NASA Astrophysics Data System (ADS)

    Mondal, Puja; Ghosh, Sankalpa

    2015-12-01

    The surface states of the three-dimensional (3D) topological insulators are described by a two-dimensional (2D) massless dirac equation. A gate-voltage-induced one-dimensional potential barrier on such surfaces creates a discrete bound state in the forbidden region outside the dirac cone. Even for a single barrier it is shown that such a bound state can create an electrostatic analogue of Shubnikov de Haas oscillation which can be experimentally observed for relatively smaller size samples. However, when these surface states are exposed to a periodic arrangement of such gate-voltage-induced potential barriers, the band structure of the same was significantly modified. This is expected to significantly alter the properties of the macroscopic system. We also suggest that, within suitable limits, the system may offer ways to control electron spin electrostatically, which may be practically useful.

  8. Gate-tuned Josephson effect on the surface of a topological insulator

    PubMed Central

    2014-01-01

    In the study, we investigate the Josephson supercurrent of a superconductor/normal metal/superconductor junction on the surface of a topological insulator, where a gate electrode is attached to the normal metal. It is shown that the Josephson supercurrent not only can be tuned largely by the temperature but also is related to the potential and the length of the weak-link region. Especially, the asymmetry excess critical supercurrent, oscillatory character, and plateau-like structure have been revealed. We except those phenomena that can be observed in the recent experiment. PMID:25249827

  9. Topological Insulator Bi2Se3 Nanowire High Performance Field-Effect Transistors

    PubMed Central

    Zhu, Hao; Richter, Curt A.; Zhao, Erhai; Bonevich, John E.; Kimes, William A.; Jang, Hyuk-Jae; Yuan, Hui; Li, Haitao; Arab, Abbas; Kirillov, Oleg; Maslar, James E.; Ioannou, Dimitris E.; Li, Qiliang

    2013-01-01

    Topological insulators are unique electronic materials with insulating interiors and robust metallic surfaces. Device applications exploiting their remarkable properties have so far been hampered by the difficulty to electrically tune the Fermi levels of both bulk and thin film samples. Here we show experimentally that single-crystal nanowires of the topological insulator Bi2Se3 can be used as the conduction channel in high-performance field effect transistor (FET), a basic circuit building block. Its current-voltage characteristics are superior to many of those reported for semiconductor nanowire transistors, including sharp turn-on, nearly zero cutoff current, very large On/Off current ratio, and well-saturated output current. The metallic electron transport at the surface with good FET effective mobility can be effectively separated from the conduction of bulk Bi2Se3 and adjusted by field effect at a small gate voltage. This opens up a suite of potential applications in nanoelectronics and spintronics.

  10. Ultra-High Voltage 4H-SiC Bi-Directional Insulated Gate Bipolar Transistors

    NASA Astrophysics Data System (ADS)

    Chowdhury, Sauvik

    4H- Silicon Carbide (4H-SiC) is an attractive material for power semiconductor devices due to its large bandgap, high critical electric field and high thermal conductivity compared to Silicon (Si). For ultra-high voltage applications (BV > 10 kV), 4H-SiC Insulated Gate Bipolar Transistors (IGBTs) are favored over unipolar transistors due to lower conduction losses. With improvements in SiC materials and processing technology, promising results have been demonstrated in the area of conventional unidirectional 4H-SiC IGBTs, with breakdown voltage ratings up to 27 kV. This research presents the experimental demonstration of the world's first high voltage bi-directional power transistors in 4H-SiC. Traditionally, four (two IGBTs and two diodes) or two (two reverse blocking IGBTs) semiconductor devices are necessary to yield a bidirectional switch. With a monolithically integrated bidirectional switch as presented here, the number of semiconductor devices is reduced to only one, which results in increased reliability and reduced cost of the overall system. Additionally, by using the unique dual gate operation of BD-IGBTs, switching losses can be reduced to a small fraction of that in conventional IGBTs, resulting in increased efficiency. First, the performance limits of SiC IGBTs are calculated by using analytical methods. The performance benefits of SiC IGBTs over SiC unipolar devices and Si IGBTs are quantified. Numerical simulations are used to optimize the unit cell and edge termination structures for a 15 kV SiC BD-IGBT. The effect of different device parameters on BD-IGBT static and switching performance are quantified. Second, the process technology necessary for the fabrication of high voltage SiC BD-IGBTs is optimized. The effect of different process steps on parameters such as breakdown voltage, carrier lifetime, gate oxide reliability, SiO2-SiC interface charge density is quantified. A carrier lifetime enhancement process has been optimized for lightly doped

  11. Reliability analysis of charge plasma based double material gate oxide (DMGO) SiGe-on-insulator (SGOI) MOSFET

    NASA Astrophysics Data System (ADS)

    Pradhan, K. P.; Sahu, P. K.; Singh, D.; Artola, L.; Mohapatra, S. K.

    2015-09-01

    A novel device named charge plasma based doping less double material gate oxide (DMGO) silicon-germanium on insulator (SGOI) double gate (DG) MOSFET is proposed for the first time. The fundamental objective in this work is to modify the channel potential, electric field and electron velocity for improving leakage current, transconductance (gm) and transconductance generation factor (TGF). Using 2-D simulation, we exhibit that the DMGO-SGOI MOSFET shows higher electron velocity at source side and lower electric field at drain side as compare to ultra-thin body (UTB) DG MOSFET. On the other hand DMGO-SGOI MOSFET demonstrates a significant improvement in gm and TGF in comparison to UTB-DG MOSFET. This work also evaluates the existence of a biasing point i.e. zero temperature coefficient (ZTC) bias point, where the device parameters become independent of temperature. The impact of operating temperature (T) on above said various performance metrics are also subjected to extensive analysis. This further validates the reliability of charge plasma DMGO SGOI MOSFET and its application opportunities involved in designing analog/RF circuits for a wide range of temperature applications.

  12. Electric-field control of spin-orbit torque in a magnetically doped topological insulator.

    PubMed

    Fan, Yabin; Kou, Xufeng; Upadhyaya, Pramey; Shao, Qiming; Pan, Lei; Lang, Murong; Che, Xiaoyu; Tang, Jianshi; Montazeri, Mohammad; Murata, Koichi; Chang, Li-Te; Akyol, Mustafa; Yu, Guoqiang; Nie, Tianxiao; Wong, Kin L; Liu, Jun; Wang, Yong; Tserkovnyak, Yaroslav; Wang, Kang L

    2016-04-01

    Electric-field manipulation of magnetic order has proved of both fundamental and technological importance in spintronic devices. So far, electric-field control of ferromagnetism, magnetization and magnetic anisotropy has been explored in various magnetic materials, but the efficient electric-field control of spin-orbit torque (SOT) still remains elusive. Here, we report the effective electric-field control of a giant SOT in a Cr-doped topological insulator (TI) thin film using a top-gate field-effect transistor structure. The SOT strength can be modulated by a factor of four within the accessible gate voltage range, and it shows strong correlation with the spin-polarized surface current in the film. Furthermore, we demonstrate the magnetization switching by scanning gate voltage with constant current and in-plane magnetic field applied in the film. The effective electric-field control of SOT and the giant spin-torque efficiency in Cr-doped TI may lead to the development of energy-efficient gate-controlled spin-torque devices compatible with modern field-effect semiconductor technologies. PMID:26727198

  13. Electric-field control of spin–orbit torque in a magnetically doped topological insulator

    NASA Astrophysics Data System (ADS)

    Fan, Yabin; Kou, Xufeng; Upadhyaya, Pramey; Shao, Qiming; Pan, Lei; Lang, Murong; Che, Xiaoyu; Tang, Jianshi; Montazeri, Mohammad; Murata, Koichi; Chang, Li-Te; Akyol, Mustafa; Yu, Guoqiang; Nie, Tianxiao; Wong, Kin L.; Liu, Jun; Wang, Yong; Tserkovnyak, Yaroslav; Wang, Kang L.

    2016-04-01

    Electric-field manipulation of magnetic order has proved of both fundamental and technological importance in spintronic devices. So far, electric-field control of ferromagnetism, magnetization and magnetic anisotropy has been explored in various magnetic materials, but the efficient electric-field control of spin–orbit torque (SOT) still remains elusive. Here, we report the effective electric-field control of a giant SOT in a Cr-doped topological insulator (TI) thin film using a top-gate field-effect transistor structure. The SOT strength can be modulated by a factor of four within the accessible gate voltage range, and it shows strong correlation with the spin-polarized surface current in the film. Furthermore, we demonstrate the magnetization switching by scanning gate voltage with constant current and in-plane magnetic field applied in the film. The effective electric-field control of SOT and the giant spin-torque efficiency in Cr-doped TI may lead to the development of energy-efficient gate-controlled spin-torque devices compatible with modern field-effect semiconductor technologies.

  14. Topological Field Theory of Time-Reversal Invariant Insulators

    SciTech Connect

    Qi, Xiao-Liang; Hughes, Taylor; Zhang, Shou-Cheng; /Stanford U., Phys. Dept.

    2010-03-19

    We show that the fundamental time reversal invariant (TRI) insulator exists in 4 + 1 dimensions, where the effective field theory is described by the 4 + 1 dimensional Chern-Simons theory and the topological properties of the electronic structure is classified by the second Chern number. These topological properties are the natural generalizations of the time reversal breaking (TRB) quantum Hall insulator in 2 + 1 dimensions. The TRI quantum spin Hall insulator in 2 + 1 dimensions and the topological insulator in 3 + 1 dimension can be obtained as descendants from the fundamental TRI insulator in 4 + 1 dimensions through a dimensional reduction procedure. The effective topological field theory, and the Z{sub 2} topological classification for the TRI insulators in 2+1 and 3+1 dimensions are naturally obtained from this procedure. All physically measurable topological response functions of the TRI insulators are completely described by the effective topological field theory. Our effective topological field theory predicts a number of novel and measurable phenomena, the most striking of which is the topological magneto-electric effect, where an electric field generates a magnetic field in the same direction, with an universal constant of proportionality quantized in odd multiples of the fine structure constant {alpha} = e{sup 2}/hc. Finally, we present a general classification of all topological insulators in various dimensions, and describe them in terms of a unified topological Chern-Simons field theory in phase space.

  15. Organic ferroelectric gate field-effect transistor memory using high-mobility rubrene thin film

    NASA Astrophysics Data System (ADS)

    Kanashima, Takeshi; Katsura, Yuu; Okuyama, Masanori

    2014-01-01

    An organic ferroelectric gate field-effect transistor (FET) memory has been fabricated using an organic semiconductor of rubrene thin film with a high mobility and a gate insulating layer of poly(vinylidene fluoride-tetrafluoroethylene) [P(VDF-TeFE)] thin film. A rubrene thin-film sheet was grown by physical vapor transport (PVT), and placed onto a spin-coated P(VDF-TeFE) thin-film layer, and Au source and drain electrodes were formed on this rubrene thin film. A hysteresis loop of the drain current-gate voltage (ID-VG) characteristic has been clearly observed in the ferroelectric gate FET, and is caused by the ferroelectricity. The maximum drain current is 1.5 × 10-6 A, which is about two orders of magnitude larger than that of the P(VDF-TeFE) gate FET using a pentacene thin film. Moreover, the mobility of this organic ferroelectric gate FET using rubrene thin film is 0.71 cm2 V-1 s-1, which is 35 times larger than that of the FET with pentacene thin film.

  16. Switching a normal insulator into a topological insulator via electric field with application to phosphorene.

    PubMed

    Liu, Qihang; Zhang, Xiuwen; Abdalla, L B; Fazzio, Adalberto; Zunger, Alex

    2015-02-11

    The study of topological insulators has generally involved search of materials that have this property as an innate quality, distinct from normal insulators. Here we focus on the possibility of converting a normal insulator into a topological one by application of an external electric field that shifts different bands by different energies and induces a specific band inversion, which leads to a topological state. Phosphorene is a two-dimensional (2D) material that can be isolated through mechanical exfoliation from layered black phosphorus, but unlike graphene and silicene, single-layer phosphorene has a large band gap (1.5-2.2 eV). Thus, it was unsuspected to exhibit band inversion and the ensuing topological insulator behavior. Using first-principles calculations with applied perpendicular electric field F⊥ on few-layer phosphorene we predict a continuous transition from the normal insulator to a topological insulator and eventually to a metal as a function of F⊥. The tuning of topological behavior with electric field would lead to spin-separated, gapless edge states, that is, quantum spin Hall effect. This finding opens the possibility of converting normal insulating materials into topological ones via electric field and making a multifunctional "field effect topological transistor" that could manipulate simultaneously both spin and charge carrier. We use our results to formulate some design principles for looking for other 2D materials that could have such an electrical-induced topological transition. PMID:25607525

  17. A novel 3D embedded gate field effect transistor - Screen-grid FET - Device concept and modelling

    NASA Astrophysics Data System (ADS)

    Fobelets, K.; Ding, P. W.; Velazquez-Perez, J. E.

    2007-05-01

    A novel 3D field effect transistor on SOI - screen-grid FET (SGrFET) - is proposed and an analysis of its DC behaviour is presented by means of 2D TCAD analysis. The novel feature of the SGrFET is the design of 3D insulated gate cylinders embedded in the SOI body. This novel gate topology improves efficiency and allows great flexibility in device and gate geometry to optimize DC performance. The floating body effect is avoided and the double gating row configuration controls short channel effects. The traditional intimate relationship between gate length and source-drain distance is removed, resulting in easy control of drain induced barrier lowering, improved output conductance and ideal sub-threshold slope. The separation between the gate fingers in each row is the key factor to optimize the performance, whilst downscaling of the source-drain distance and oxide thickness is not essential from an operational point of view. The device exhibits a huge potential in low power electronics as given by an efficiency of transconductance " gm/ Id" of 39 S/A at VDS = 100 mV over a large gate voltage range and at a source-drain distance of 825 nm. We present the modelling results of the influence of gate cylinder distribution in the channel, channel doping, gate oxide thickness, gate finger distance and source-drain distance on the characteristics of the device.

  18. Sandwich double gate vertical tunneling field-effect transistor

    NASA Astrophysics Data System (ADS)

    Wang, Ying; Zhang, Wen-hao; Yu, Cheng-hao; Cao, Fei

    2016-05-01

    In this work, a sandwich vertical tunnel field effect transistor (SDG-VTFET) is presented and studied. Since the dominant carrier tunneling of SDG-VFET occurs in a direction that is in line with the gate field, high ON-state current and steep subthreshold slope are observed. Comparisons between SDG-VFET and double gate tunnel field effect transistor are made to clarify advantages of SDG-VTFET. The simulation results of our work show that SDG-VTFET has stronger gate control, steeper subthreshold slope and higher ON-state current. The device plays a promising candidate for future low power circuit applications.

  19. Design and analysis of polarization independent all-optical logic gates in silicon-on-insulator photonic crystal

    NASA Astrophysics Data System (ADS)

    Rani, Preeti; Kalra, Yogita; Sinha, R. K.

    2016-09-01

    In this paper, we have reported design and analysis of polarization independent all optical logic gates in silicon-on-insulator photonic crystal consisting of two dimensional honeycomb lattices with two different air holes exhibiting photonic band gap for both TE and TM mode in the optical communication window. The proposed structures perform as an AND optical logic gate and all the optical logic gates based on the phenomenon of interference. The response period and bit rate for TE and TM polarizations at a wavelength of 1.55 μm show improved results as reported earlier.

  20. Excavationless Exterior Foundation Insulation Field Study

    SciTech Connect

    Schirber, T.; Mosiman, G.; Ojczyk, C.

    2014-10-01

    Building science research supports installing exterior (soil side) foundation insulation as the optimal method to enhance the hygrothermal performance of new homes. With exterior foundation insulation, water management strategies are maximized while insulating the basement space and ensuring a more even temperature at the foundation wall. However, such an approach can be very costly and disruptive when applied to an existing home, requiring deep excavation around the entire house. The NorthernSTAR Building America Partnership team implemented an innovative, minimally invasive foundation insulation upgrade technique on an existing home. The approach consisted of using hydrovac excavation technology combined with a liquid insulating foam. The team was able to excavate a continuous 4" wide by 4' to 5' deep trench around the entire house, 128 linear feet, except for one small part under the stoop that was obstructed with concrete debris. The combination pressure washer and vacuum extraction technology also enabled the elimination of large trenches and soil stockpiles normally produced by backhoe excavation. The resulting trench was filled with liquid insulating foam, which also served as a water-control layer of the assembly. The insulation was brought above grade using a liquid foam/rigid foam hybrid system and terminated at the top of the rim joist. Cost savings over the traditional excavation process ranged from 23% to 50%. The excavationless process could result in even greater savings since replacement of building structures, exterior features, utility meters, and landscaping would be minimal or non-existent in an excavationless process.

  1. Excavationless Exterior Foundation Insulation Field Study

    SciTech Connect

    Schirber, T.; Mosiman, G.; Ojczyk, C.

    2014-09-01

    Building science research supports installing exterior (soil side) foundation insulation as the optimal method to enhance the hygrothermal performance of new homes. With exterior foundation insulation, water management strategies are maximized while insulating the basement space and ensuring a more even temperature at the foundation wall. However, such an approach can be very costly and disruptive when applied to an existing home, requiring deep excavation around the entire house. The NorthernSTAR Building America Partnership team implemented an innovative, minimally invasive foundation insulation upgrade technique on an existing home. The approach consisted of using hydrovac excavation technology combined with liquid insulating foam. The team was able to excavate a continuous 4 inches wide by 4 feet to 5 feet deep trench around the entire house, 128 linear feet, except for one small part under the stoop that was obstructed with concrete debris. The combination pressure washer and vacuum extraction technology also enabled the elimination of large trenches and soil stockpiles normally produced by backhoe excavation. The resulting trench was filled with liquid insulating foam, which also served as a water-control layer of the assembly. The insulation was brought above grade using a liquid foam/rigid foam hybrid system and terminated at the top of the rim joist. Cost savings over the traditional excavation process ranged from 23% to 50%. The excavationless process could result in even greater savings since replacement of building structures, exterior features, utility meters, and landscaping would be minimal or non-existent in an excavationless process.

  2. Microscopic signature of insulator-to-metal transition in highly doped semicrystalline conducting polymers in ionic-liquid-gated transistors

    NASA Astrophysics Data System (ADS)

    Tanaka, Hisaaki; Nishio, Satoshi; Ito, Hiroshi; Kuroda, Shin-ichi

    2015-12-01

    Electronic state of charge carriers, in particular, in highly doped regions, in thin-film transistors of a semicrystalline conducting polymer poly(2,5-bis(3-alkylthiophene-2-yl)thieno[3,2-b]thiophene), has been studied by using field-induced electron spin resonance (ESR) spectroscopy. By adopting an ionic-liquid gate insulator, a gate-controlled reversible electrochemical hole-doping of the polymer backbone is achieved, as confirmed from the change of the optical absorption spectra. The edge-on molecular orientation in the pristine film is maintained even after the electrochemical doping, which is clarified from the angular dependence of the g value. As the doping level increases, spin 1/2 polarons transform into spinless bipolarons, which is demonstrated from the spin-charge relation showing a spin concentration peak around 1%, contrasting to the monotonic increase in the charge concentration. At high doping levels, a drastic change in the linewidth anisotropy due to the generation of conduction electrons is observed, indicating the onset of metallic state, which is also supported by the temperature dependence of the spin susceptibility and the ESR linewidth. Our results suggest that semicrystalline conducting polymers become metallic with retaining their molecular orientational order, when appropriate doping methods are chosen.

  3. Microscopic signature of insulator-to-metal transition in highly doped semicrystalline conducting polymers in ionic-liquid-gated transistors

    SciTech Connect

    Tanaka, Hisaaki Nishio, Satoshi; Ito, Hiroshi; Kuroda, Shin-ichi

    2015-12-14

    Electronic state of charge carriers, in particular, in highly doped regions, in thin-film transistors of a semicrystalline conducting polymer poly(2,5-bis(3-alkylthiophene-2-yl)thieno[3,2-b]thiophene), has been studied by using field-induced electron spin resonance (ESR) spectroscopy. By adopting an ionic-liquid gate insulator, a gate-controlled reversible electrochemical hole-doping of the polymer backbone is achieved, as confirmed from the change of the optical absorption spectra. The edge-on molecular orientation in the pristine film is maintained even after the electrochemical doping, which is clarified from the angular dependence of the g value. As the doping level increases, spin 1/2 polarons transform into spinless bipolarons, which is demonstrated from the spin-charge relation showing a spin concentration peak around 1%, contrasting to the monotonic increase in the charge concentration. At high doping levels, a drastic change in the linewidth anisotropy due to the generation of conduction electrons is observed, indicating the onset of metallic state, which is also supported by the temperature dependence of the spin susceptibility and the ESR linewidth. Our results suggest that semicrystalline conducting polymers become metallic with retaining their molecular orientational order, when appropriate doping methods are chosen.

  4. 14. IRRIGATION DITCH LEADING FROM GATE 5 TO HONDIUS' FIELDS. ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    14. IRRIGATION DITCH LEADING FROM GATE 5 TO HONDIUS' FIELDS. LOOKING NORTHWEST. - Hondius Water Line, 1.6 miles Northwest of Park headquarters building & 1 mile Northwest of Beaver Meadows entrance station, Estes Park, Larimer County, CO

  5. Nanodiamond vacuum field emission device with gate modulated triode characteristics

    NASA Astrophysics Data System (ADS)

    Hsu, S. H.; Kang, W. P.; Raina, S.; Huang, J. H.

    2013-05-01

    A three-electrode nanodiamond vacuum field emission (VFE) device with gate modulated triode characteristics is developed by integrating nanodiamond emitter with self-aligned silicon gate and anode, employing a mold transfer technique in conjunction with chemical vapor deposition of nanodiamond. Triode behavior showing emission current modulation with high current density at low operating voltages is achieved. A systematic analysis based on modified Fowler-Nordheim theory is used to analyze gate modulated VFE characteristics, confirming the triode field emission mechanism and operating principle. The realization of an efficient VFE microtriode has achieved the fundamental step for further development of vacuum integrated microelectronics.

  6. Colossal Magnetoresistance in a Mott Insulator via Magnetic Field-Driven Insulator-Metal Transition

    NASA Astrophysics Data System (ADS)

    Zhu, M.; Peng, J.; Zou, T.; Prokes, K.; Mahanti, S. D.; Hong, T.; Mao, Z. Q.; Liu, G. Q.; Ke, X.

    2016-05-01

    We present a new type of colossal magnetoresistance (CMR) arising from an anomalous collapse of the Mott insulating state via a modest magnetic field in a bilayer ruthenate, Ti-doped Ca3Ru2O7 . Such an insulator-metal transition is accompanied by changes in both lattice and magnetic structures. Our findings have important implications because a magnetic field usually stabilizes the insulating ground state in a Mott-Hubbard system, thus calling for a deeper theoretical study to reexamine the magnetic field tuning of Mott systems with magnetic and electronic instabilities and spin-lattice-charge coupling. This study further provides a model approach to search for CMR systems other than manganites, such as Mott insulators in the vicinity of the boundary between competing phases.

  7. Colossal Magnetoresistance in a Mott Insulator via Magnetic Field-Driven Insulator-Metal Transition.

    PubMed

    Zhu, M; Peng, J; Zou, T; Prokes, K; Mahanti, S D; Hong, T; Mao, Z Q; Liu, G Q; Ke, X

    2016-05-27

    We present a new type of colossal magnetoresistance (CMR) arising from an anomalous collapse of the Mott insulating state via a modest magnetic field in a bilayer ruthenate, Ti-doped Ca_{3}Ru_{2}O_{7}. Such an insulator-metal transition is accompanied by changes in both lattice and magnetic structures. Our findings have important implications because a magnetic field usually stabilizes the insulating ground state in a Mott-Hubbard system, thus calling for a deeper theoretical study to reexamine the magnetic field tuning of Mott systems with magnetic and electronic instabilities and spin-lattice-charge coupling. This study further provides a model approach to search for CMR systems other than manganites, such as Mott insulators in the vicinity of the boundary between competing phases. PMID:27284665

  8. Effective hydrodynamic field theory and condensation picture of topological insulators

    NASA Astrophysics Data System (ADS)

    Chan, AtMa P. O.; Kvorning, Thomas; Ryu, Shinsei; Fradkin, Eduardo

    2016-04-01

    While many features of topological band insulators are commonly discussed at the level of single-particle electron wave functions, such as the gapless Dirac boundary spectrum, it remains elusive to develop a hydrodynamic or collective description of fermionic topological band insulators in 3+1 dimensions. As the Chern-Simons theory for the 2+1-dimensional quantum Hall effect, such a hydrodynamic effective field theory provides a universal description of topological band insulators, even in the presence of interactions, and that of putative fractional topological insulators. In this paper, we undertake this task by using the functional bosonization. The effective field theory in the functional bosonization is written in terms of a two-form gauge field, which couples to a U (1 ) gauge field that arises by gauging the continuous symmetry of the target system [the U (1 ) particle number conservation]. Integrating over the U (1 ) gauge field by using the electromagnetic duality, the resulting theory describes topological band insulators as a condensation phase of the U (1 ) gauge theory (or as a monopole condensation phase of the dual gauge field). The hydrodynamic description of the surface of topological insulators and the implication of its duality are also discussed. We also touch upon the hydrodynamic theory of fractional topological insulators by using the parton construction.

  9. Protected gates for topological quantum field theories

    NASA Astrophysics Data System (ADS)

    Koenig, Robert

    2015-03-01

    We give restrictions on the locality-preserving unitary automorphisms U, which are protected gates, for topologically ordered systems. For arbitrary anyon models, we show that such unitaries only generate a finite group, and hence do not provide universality. For abelian anyon models, we find that the logical action of U is contained in a proper subgroup of the generalized Clifford group. In the case D(?2), which describes Kitaev's toric code, this represents a tightening of statement previously obtained within the stabilizer framework (PRL 110:170503). For non-abelian models, we find that such automorphisms are very limited: for example, there is no non-trivial gate for Fibonacci anyons. For Ising anyons, protected gates are elements of the Pauli group. These results are derived by relating such automorphisms to symmetries of the underlying anyon model: protected gates realize automorphisms of the Verlinde algebra. We additionally use the compatibility with basis changes to characterize the logical action. This is joint work with M. Beverland, F. Pastawski, J. Preskill and S. Sijher.

  10. High temperature study of flexible silicon-on-insulator fin field-effect transistors

    SciTech Connect

    Diab, Amer; Torres Sevilla, Galo A.; Ghoneim, Mohamed T.; Hussain, Muhammad M.

    2014-09-29

    We report high temperature electrical transport characteristics of a flexible version of the semiconductor industry's most advanced architecture: fin field-effect transistor on silicon-on-insulator with sub-20 nm fins and high-κ/metal gate stacks. Characterization from room to high temperature (150 °C) was completed to determine temperature dependence of drain current (I{sub ds}), gate leakage current (I{sub gs}), transconductance (g{sub m}), and extracted low-field mobility (μ{sub 0}). Mobility degradation with temperature is mainly caused by phonon scattering. The other device characteristics show insignificant difference at high temperature which proves the suitability of inorganic flexible electronics with advanced device architecture.

  11. Electron beam assisted field evaporation of insulating nanowires/tubes

    NASA Astrophysics Data System (ADS)

    Blanchard, N. P.; Niguès, A.; Choueib, M.; Perisanu, S.; Ayari, A.; Poncharal, P.; Purcell, S. T.; Siria, A.; Vincent, P.

    2015-05-01

    We demonstrate field evaporation of insulating materials, specifically BN nanotubes and undoped Si nanowires, assisted by a convergent electron beam. Electron irradiation leads to positive charging at the nano-object's apex and to an important increase of the local electric field thus inducing field evaporation. Experiments performed both in a transmission electron microscope and in a scanning electron microscope are presented. This technique permits the selective evaporation of individual nanowires in complex materials. Electron assisted field evaporation could be an interesting alternative or complementary to laser induced field desorption used in atom probe tomography of insulating materials.

  12. Electron beam assisted field evaporation of insulating nanowires/tubes

    SciTech Connect

    Blanchard, N. P. Niguès, A.; Choueib, M.; Perisanu, S.; Ayari, A.; Poncharal, P.; Purcell, S. T.; Siria, A.; Vincent, P.

    2015-05-11

    We demonstrate field evaporation of insulating materials, specifically BN nanotubes and undoped Si nanowires, assisted by a convergent electron beam. Electron irradiation leads to positive charging at the nano-object's apex and to an important increase of the local electric field thus inducing field evaporation. Experiments performed both in a transmission electron microscope and in a scanning electron microscope are presented. This technique permits the selective evaporation of individual nanowires in complex materials. Electron assisted field evaporation could be an interesting alternative or complementary to laser induced field desorption used in atom probe tomography of insulating materials.

  13. High-performance GaAs metal-insulator-semiconductor field-effect transistors enabled by self-assembled nanodielectrics

    NASA Astrophysics Data System (ADS)

    Lin, H. C.; Ye, P. D.; Xuan, Y.; Lu, G.; Facchetti, A.; Marks, T. J.

    2006-10-01

    High-performance GaAs metal-insulator-semiconductor field-effect-transistors (MISFETs) fabricated with very thin self-assembled organic nanodielectrics (SANDs), deposited from solution at room temperature, are demonstrated. A submicron gate-length depletion-mode n-channel GaAs MISFET with SAND thicknesses ranging from 5.5to16.5nm exhibit a gate leakage current density <10-5A/cm2 at a gate bias smaller than 3V, a maximum drain current of 370mA/mm at a forward gate bias of 2V, and a maximum intrinsic transconductance of 170mS/mm. The importance of appropriate GaAs surface chemistry treatments on SAND/GaAs interface properties is also presented. Application of SANDs to III-V compound semiconductors affords more opportunities to manipulate the complex III-V surface chemistry with broad materials options.

  14. Field-effect modulation of anomalous Hall effect in diluted ferromagnetic topological insulator epitaxial films

    NASA Astrophysics Data System (ADS)

    Chang, CuiZu; Liu, MinHao; Zhang, ZuoCheng; Wang, YaYu; He, Ke; Xue, QiKun

    2016-03-01

    High quality chromium (Cr) doped three-dimensional topological insulator (TI) Sb2Te3 films are grown via molecular beam epitaxy on heat-treated insulating SrTiO3 (111) substrates. We report that the Dirac surface states are insensitive to Cr doping, and a perfect robust long-range ferromagnetic order is unveiled in epitaxial Sb2- x Cr x Te3 films. The anomalous Hall effect is modulated by applying a bottom gate, contrary to the ferromagnetism in conventional diluted magnetic semiconductors (DMSs), here the coercivity field is not significantly changed with decreasing carrier density. Carrier-independent ferromagnetism heralds Sb2- x Cr x Te3 films as the base candidate TI material to realize the quantum anomalous Hall (QAH) effect. These results also indicate the potential of controlling anomalous Hall voltage in future TI-based magneto-electronics and spintronics.

  15. Self-aligned graphene field-effect transistors on SiC (0001) substrates with self-oxidized gate dielectric

    NASA Astrophysics Data System (ADS)

    Jia, Li; Cui, Yu; Li, Wang; Qingbin, Liu; Zezhao, He; Shujun, Cai; Zhihong, Feng

    2014-07-01

    A scalable self-aligned approach is employed to fabricate monolayer graphene field-effect transistors on semi-insulated 4H-SiC (0001) substrates. The self-aligned process minimized access resistance and parasitic capacitance. Self-oxidized Al2O3, formed by deposition of 2 nm Al followed by exposure in air to be oxidized, is used as gate dielectric and shows excellent insulation. An intrinsic cutoff frequency of 34 GHz and maximum oscillation frequency of 36.4 GHz are realized for the monolayer graphene field-effect transistor with a gate length of 0.2 μm. These studies show a pathway to fabricate graphene transistors for future applications in ultra-high frequency circuits.

  16. Insulated-gate field-effect transistor strain sensor

    NASA Technical Reports Server (NTRS)

    Gross, C.

    1972-01-01

    Strain sensors that can be switched on and off were fabricated from p-channel IGFET on thin filament n-type silicon crystals with silicon dioxide layer sputtered over transistor for passivation. Applications include integration with microelectronic circuits for multiplexing.

  17. Gate control of ferromagnetic insulating phase in lightly-doped La0.875Sr0.125MnO3-δ film

    NASA Astrophysics Data System (ADS)

    Kuang, H.; Wang, J.; Hu, F. X.; Zhao, Y. Y.; Liu, Y.; Wu, R. R.; Sun, J. R.; Shen, B. G.

    2016-02-01

    The electric field effect on the lightly doped La0.875Sr0.125MnO3-δ (LSMO) thin film in electric double-layer transistors was investigated by measuring transport properties of the film under various gate voltages. It was found that the positive gate bias leads to an increase of the charge-orbital ordering (COO) transition temperature and a decrease of the Curie temperature TC, indicating the suppression of ferromagnetic metal (FMM) phases and preference of COO/ferromagnetic insulator (FMI) with the hole depletion by gate bias. Such different electric field effects can be ascribed to the weakening of the ferromagnetic interaction and enhancement of Jahn-Teller (JT) distortion caused by the transformation of JT inactive Mn4+-ions to JT active Mn3+-ions. Moreover, a step-like increase in the high temperature region of the ρ-T curve, which is related to the transition of cooperative JT distortion, was found to develop with increasing the positive bias, indicating that the cooperative JT distorted phase is stabilized by the depletion of holes in LSMO film. These results demonstrate that the modulation of holes via electric field strongly affects the balance between energy gains of different interactions and thus produce different effects on the competing FMI, FMM, and cooperative JT distorted phases in LSMO film.

  18. Compact Modeling of Floating-Base Effect in Injection-Enhanced Insulated-Gate Bipolar Transistor Based on Potential Modification by Accumulated Charge

    NASA Astrophysics Data System (ADS)

    Yamamoto, Takao; Miyake, Masataka; Miura-Mattausch, Mitiko

    2013-04-01

    We have developed a compact model of the injection-enhanced insulated-gate bipolar transistor (IGBT) applicable for circuit optimization. The main development is modeling the hole accumulation in the floating-base region. It is demonstrated that the observed negative gate capacitance is well reproduced with the developed model.

  19. Golden Gate Park, Chalet Recreation Field, Bounded by John F. ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    Golden Gate Park, Chalet Recreation Field, Bounded by John F. Kennedy Drive to the north and east, former Richmond-Sunset Sewage Treatment Plant to the south, and the Old Railroad Trail to the west, San Francisco, San Francisco County, CA

  20. Quantum transport in topological insulator nanoribbon field effect and Josephson devices

    NASA Astrophysics Data System (ADS)

    Kayyalha, Morteza; Jauregui, Luis; Kazakov, Aleksander; Pettes, Michael; Miotkowski, Ireneusz; Shi, Li; Rokhinson, Leonid; Chen, Yong

    The spin-helical topological surface states (TSS) of topological insulators have attracted great attention in the past few years as an excellent platform to study topological transport and other exotic physics such as Majorana fermions. Here we present experiments studying quantum transport of TSS in topological insulator nanoribbon (TINR) field effect devices with normal as well as superconducting contacts. In Bi2Te3 NRs with normal contacts, we observe that the conductance vs. axial magnetic field exhibits Aharonov-Bohm (AB) oscillations with an alternating phase of zero and π, depending periodically on the Fermi momentum kF tuned by an applied back-gate voltage, consistent with the 1D sub-band structure formed by circumferentially quantized TSS. We also investigated the Josephson effects in BiSbTeSe2 TINRs with superconducting Nb contacts. We measured the gate voltage and temperature dependence of the supercurrent and multiple Andreev reflections (MAR), to probe phase coherent transport via TSS

  1. Tuning Quantum Oscillations of Dirac Surface States on the Topological Insulator Bi2Te2Se by Ionic Liquid Gating

    NASA Astrophysics Data System (ADS)

    Xiong, Jun; Khoo, Yuehaw; Jia, Shuang; Cava, Robert J.; Phuan Ong, Nai

    2013-03-01

    An in-situ method to tune the chemical potential near the Dirac Point (DP) of a topological insulator (TI) would greatly facilitate several key experiments. However, in as-grown crystals of Bi-based TIs, the chemical potential μ lies high above the DP. Using liquid gating on 50- μm thick crystals of Bi2Te2Se, we demonstrate that μ can be tuned by a factor of 6 by observing changes to the Shubnikov-de Haas (SdH) period. A surprise is that the SdH amplitudes increase sharply with gating. Liquid gating allows the n=1 Landau level to be accessed, and the π-Berry phase to be determined with improved accuracy. We will discuss reversibility of liquid gating, and how we may distinguish the purely gating action from chemical reaction. Supported by NSF-MRSEC (DMR 0819860), Army Research Office (ARO W911NF-11- 1-0379) and DARPA under SPAWAR program (Grant N66001-11-1-4110).

  2. Evolution of Insulator-Metal Phase Transitions in Epitaxial Tungsten Oxide Films during Electrolyte-Gating.

    PubMed

    Nishihaya, Shinichi; Uchida, Masaki; Kozuka, Yusuke; Iwasa, Yoshihiro; Kawasaki, Masashi; Nishihaya, S; Uchida, M; Kozuka, Y; Iwasa, Y; Kawasaki, M; Iwasa, Y; Kawasaki, M

    2016-08-31

    An interface between an oxide and an electrolyte gives rise to various processes as exemplified by electrostatic charge accumulation/depletion and electrochemical reactions such as intercalation/decalation under electric field. Here we directly compare typical device operations of those in electric double layer transistor geometry by adopting A-site vacant perovskite WO3 epitaxial thin films as a channel material and two different electrolytes as gating agent. In situ measurements of X-ray diffraction and channel resistance performed during the gating revealed that in both the cases WO3 thin film reaches a new metallic state through multiple phase transitions, accompanied by the change in out-of-plane lattice constant. Electrons are electrostatically accumulated from the interface side with an ionic liquid, while alkaline metal ions are more uniformly intercalated into the film with a polymer electrolyte. We systematically demonstrate this difference in the electrostatic and electrochemical processes, by comparing doped carrier density, lattice deformation behavior, and time constant of the phase transitions. PMID:27502546

  3. Field-emission cathodes of glass-insulated microwire

    SciTech Connect

    Donika, F.G.; Miglei, D.F.; Smyslov, V.V.

    1987-08-01

    A method is described for fabricating field-emission cathodes in glass insulation. Cathodes with nickel and germanium emitters have packing densities of 10/sup 2/-10/sup 4/ pieces/mm/sup 2/ and point radii of curvature of 0.1-1 ..mu..m.

  4. Surface grafting of octylamine onto poly(ethylene-alt-maleic anhydride) gate insulators for low-voltage DNTT thin-film transistors.

    PubMed

    Choe, Yun-Seo; Yi, Mi Hye; Kim, Ji-Heung; Kim, Yun Ho; Jang, Kwang-Suk

    2016-03-28

    This study investigates a spin-coating method for modifying the surface properties of a poly(ethylene-alt-maleic anhydride) (PEMA) gate insulator. The 60 nm-thick PEMA thin film exhibits excellent electrical insulating properties, and its surface properties could be easily modified by surface grafting of octylamine. Due to surface treatment via spin-coating, the surface energy of the PEMA gate insulator decreased, the crystal quality of the organic semiconductor improved, and consequently the performance of low-voltage organic thin-film transistors (TFTs) was enhanced. Our results suggest that the surface treatment of the PEMA gate insulator could be a simple and effective method for enhancing the performance of organic TFTs. PMID:26940136

  5. Interface effects on the characteristics of metal-ferroelectric-insulator-semiconductor field-effect transistor

    NASA Astrophysics Data System (ADS)

    Sun, Jing; Zheng, Xue Jun; Cao, Juan; Li, Wen

    2011-09-01

    The interface effects on the electrical characteristics of metal-ferroelectric-insulator- semiconductor field-effect transistor (MFIS-FET) are studied using an improved model in which the expressions for interface and the mobility model are incorporated into Lue model. The interface layer between the ferroelectric and the electrode and the SiO2 layer between the insulator and the semiconductor have been investigated. Capacitance-gate voltage (C-VG) and drain current-gate voltage (ID-VGS) characteristics are modeled with fixed interface layer and SiO2 layer thicknesses and show good agreement with the experiments, verifying the validity of the improved model and the existence of the interface in the transistor. The characteristics, such as C-VG, ID-VGS and drain current-drain voltage (ID-VDS), are modeled respectively with various interface layer and SiO2 layer thicknesses. The thicker the interface layer and SiO2 layer are, the worse the transistor characteristics become. Similar characteristics can be observed at the specific thickness of the two layers, indicating that both interface layer and SiO2 layer should be considered when the characteristics of MFIS-FETs degrade. In addition, the type of the interfaces can be distinguished by comparing the capacitance in the accumulation region. It is expected that this work can offer some useful guidance to the design and performance improvement of MFIS structure devices.

  6. Magnetic field-induced helical mode and topological transitions in a topological insulator nanoribbon.

    PubMed

    Jauregui, Luis A; Pettes, Michael T; Rokhinson, Leonid P; Shi, Li; Chen, Yong P

    2016-04-01

    The spin-helical Dirac fermion topological surface states in a topological insulator nanowire or nanoribbon promise novel topological devices and exotic physics such as Majorana fermions. Here, we report local and non-local transport measurements in Bi2Te3 topological insulator nanoribbons that exhibit quasi-ballistic transport over ∼2 μm. The conductance versus axial magnetic flux Φ exhibits Aharonov-Bohm oscillations with maxima occurring alternately at half-integer or integer flux quanta (Φ0 = h/e, where h is Planck's constant and e is the electron charge) depending periodically on the gate-tuned Fermi wavevector (kF) with period 2π/C (where C is the nanoribbon circumference). The conductance versus gate voltage also exhibits kF-periodic oscillations, anti-correlated between Φ = 0 and Φ0/2. These oscillations enable us to probe the Bi2Te3 band structure, and are consistent with the circumferentially quantized topological surface states forming a series of one-dimensional subbands, which undergo periodic magnetic field-induced topological transitions with the disappearance/appearance of the gapless Dirac point with a one-dimensional spin helical mode. PMID:26780658

  7. Magnetic field-induced helical mode and topological transitions in a topological insulator nanoribbon

    NASA Astrophysics Data System (ADS)

    Jauregui, Luis A.; Pettes, Michael T.; Rokhinson, Leonid P.; Shi, Li; Chen, Yong P.

    2016-04-01

    The spin-helical Dirac fermion topological surface states in a topological insulator nanowire or nanoribbon promise novel topological devices and exotic physics such as Majorana fermions. Here, we report local and non-local transport measurements in Bi2Te3 topological insulator nanoribbons that exhibit quasi-ballistic transport over ∼2 μm. The conductance versus axial magnetic flux Φ exhibits Aharonov–Bohm oscillations with maxima occurring alternately at half-integer or integer flux quanta (Φ0 = h/e, where h is Planck's constant and e is the electron charge) depending periodically on the gate-tuned Fermi wavevector (kF) with period 2π/C (where C is the nanoribbon circumference). The conductance versus gate voltage also exhibits kF-periodic oscillations, anti-correlated between Φ = 0 and Φ0/2. These oscillations enable us to probe the Bi2Te3 band structure, and are consistent with the circumferentially quantized topological surface states forming a series of one-dimensional subbands, which undergo periodic magnetic field-induced topological transitions with the disappearance/appearance of the gapless Dirac point with a one-dimensional spin helical mode.

  8. Diamond logic inverter with enhancement-mode metal-insulator-semiconductor field effect transistor

    SciTech Connect

    Liu, J. W.; Liao, M. Y.; Imura, M.; Watanabe, E.; Oosato, H.; Koide, Y.

    2014-08-25

    A diamond logic inverter is demonstrated using an enhancement-mode hydrogenated-diamond metal-insulator-semiconductor field effect transistor (MISFET) coupled with a load resistor. The gate insulator has a bilayer structure of a sputtering-deposited LaAlO{sub 3} layer and a thin atomic-layer-deposited Al{sub 2}O{sub 3} buffer layer. The source-drain current maximum, extrinsic transconductance, and threshold voltage of the MISFET are measured to be −40.7 mA·mm{sup −1}, 13.2 ± 0.1 mS·mm{sup −1}, and −3.1 ± 0.1 V, respectively. The logic inverters show distinct inversion (NOT-gate) characteristics for input voltages ranging from 4.0 to −10.0 V. With increasing the load resistance, the gain of the logic inverter increases from 5.6 to as large as 19.4. The pulse response against the high and low input voltages shows the inversion response with the low and high output voltages.

  9. Dynamical Axion Field in a Magnetic Topological Insulator Superlattice

    NASA Astrophysics Data System (ADS)

    Wang, Jing; Lian, Biao; Zhang, Shou-Cheng

    We propose that the dynamical axion field can be realized in a magnetic topological insulator superlattice or a topological paramagnetic insulator. The magnetic fluctuations of these systems produce a pseudoscalar field which has an axionic coupling to the electromagnetic field, and thus it gives a condensed-matter realization of the axion electrodynamics. Compared to the previously proposed dynamical axion materials where a long range antiferromagnetic order is required, the systems proposed here have the advantage that only an uniform magnetization or a paramagnetic state is needed for the dynamic axion. We further propose several experiments to detect such a dynamical axion field. This work is supported by the US Department of Energy, Office of Basic Energy Sciences, Division of Materials Sciences and Engineering, under Contract No. DE-AC02-76SF00515.

  10. Model for the field effect from layers of biological macromolecules on the gates of metal-oxide-semiconductor transistors

    NASA Astrophysics Data System (ADS)

    Landheer, D.; Aers, G.; McKinnon, W. R.; Deen, M. J.; Ranuarez, J. C.

    2005-08-01

    The potential diagram for field-effect transistors used to detect charged biological macromolecules in an electrolyte is presented for the case where an insulating cover layer is used over a conventional eletrolyte-insulator metal-oxide-semiconductor (EIMOS) structure to tether or bind the biological molecules to a floating gate. The layer of macromolecules is modeled using the Poisson-Boltzmann equation for an ion-permeable membrane. Expressions are derived for the charges and potentials in the EIMOS and electrolyte-insulator-semiconductor structures, including the membrane and electrolyte. Exact solutions for the potentials and charges are calculated using numerical algorithms. Simple expressions for the response are presented for low solution potentials when the Donnan potential is approached in the bulk of the membrane. The implications of the model for the small-signal equivalent circuit and the noise analysis of these structures are discussed.

  11. Metrology solutions for high performance germanium multi-gate field-effect transistors using optical scatterometry

    NASA Astrophysics Data System (ADS)

    Chin, Hock-Chun; Ling, Moh-Lung; Liu, Bin; Zhang, Xingui; Li, Jie; Liu, Yongdong; Hu, Jiangtao; Yeo, Yee-Chia

    2013-04-01

    In this work, we report the first demonstration of scatterometry Optical Critical Dimension (OCD) characterization on advanced Ge Multi-Gate Field-Effect Transistor (MuGFET) or FinFET formed on a Germanium-on-Insulator (GeOI) substrate. Two critical process steps in the Ge MuGFET process flow were investigated, i.e. after Ge Fin formation, and after TaN gate stack etching process. All key process variations in the test structures were successfully monitored by the floating or fitting parameters in the OCD models. In addition, excellent static repeatability, with 3σ lower than 0.12 nm, was also achieved. The measurement results from OCD were also compared with both Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM) measurements. Excellent correlation with both SEM and TEM was achieved by employing OCD characterization, confirming scatterometry OCD as a promising metrology technique for next generation multi-gate transistor with an advanced channel material.

  12. Metallic 2D Surface State of Silicon by Ionic Liquid gating and observation of Reentrant Insulating behavior

    NASA Astrophysics Data System (ADS)

    Nelson, J. J.; Goldman, A. M.

    2015-03-01

    Metal insulator transitions are usually observed in high mobility and low carrier density 2D electron systems. There are several open questions regarding the metallic state including its existence in the limit of zero temperature. The current experimental focus is on the production of higher mobility samples to push the critical carrier density to even lower values, which will increase the effects of the Coulomb interaction. Here we report an unexpected result, the observation of the onset of a metallic state at high carrier densities in silicon gated with the ionic liquid DEME-TFSI. In addition we have observed a return to the insulating state as the carrier density was further increased. This reentrant insulting behavior is an effect that was recently predicted. Supported in part by NSF/DMR-1263316. Part of this work was carried out at the Minnesota Nanocenter.

  13. Open Heisenberg chain under boundary fields: A magnonic logic gate

    NASA Astrophysics Data System (ADS)

    Landi, Gabriel T.; Karevski, Dragi

    2015-05-01

    We study the spin transport in the quantum Heisenberg spin chain subject to boundary magnetic fields and driven out of equilibrium by Lindblad dissipators. An exact solution is given in terms of matrix product states, which allows us to calculate exactly the spin current for any chain size. It is found that the system undergoes a discontinuous spin-valve-like quantum phase transition from ballistic to subdiffusive spin current, depending on the value of the boundary fields. Thus, the chain behaves as an extremely sensitive magnonic logic gate operating with the boundary fields as the base element.

  14. Interfacial and electrical characteristics of Al2O3 gate dielectric on fully depleted SiGe on insulator

    NASA Astrophysics Data System (ADS)

    Di, Zengfeng; Zhang, Miao; Liu, Weili; Shen, Qinwo; Luo, Suhua; Song, Zhitang; Lin, Chenglu; Huang, Anping; Chu, Paul K.

    2005-06-01

    The interfacial and electrical characteristics of as-deposited or annealed A2O3 gate dielectric films grown on fully depleted SiGe-on-insulator are investigated. An interfacial layer composed of SiOx and GeOx is observed in the as-grown film. The interfacial silicate formation is effectively suppressed by GeOx formation. However, GeOx is reduced to Ge and extensive silicate formation occurs after annealing. The formation of silicate and disappearance of GeOx after annealing leads to a decrease in the density of the interfacial states.

  15. Oxygen Displacement in Cuprates under Ionic Liquid Field-Effect Gating.

    PubMed

    Dubuis, Guy; Yacoby, Yizhak; Zhou, Hua; He, Xi; Bollinger, Anthony T; Pavuna, Davor; Pindak, Ron; Božović, Ivan

    2016-01-01

    We studied structural changes in a 5 unit cell thick La1.96Sr0.04CuO4 film, epitaxially grown on a LaSrAlO4 substrate with a single unit cell buffer layer, when ultra-high electric fields were induced in the film by applying a gate voltage between the film (ground) and an ionic liquid in contact with it. Measuring the diffraction intensity along the substrate-defined Bragg rods and analyzing the results using a phase retrieval method we obtained the three-dimensional electron density in the film, buffer layer, and topmost atomic layers of the substrate under different applied gate voltages. The main structural observations were: (i) there were no structural changes when the voltage was negative, holes were injected into the film making it more metallic and screening the electric field; (ii) when the voltage was positive, the film was depleted of holes becoming more insulating, the electric field extended throughout the film, the partial surface monolayer became disordered, and equatorial oxygen atoms were displaced towards the surface; (iii) the changes in surface disorder and the oxygen displacements were both reversed when a negative voltage was applied; and (iv) the c-axis lattice constant of the film did not change in spite of the displacement of equatorial oxygen atoms. PMID:27578237

  16. Oxygen Displacement in Cuprates under Ionic Liquid Field-Effect Gating

    PubMed Central

    Dubuis, Guy; Yacoby, Yizhak; Zhou, Hua; He, Xi; Bollinger, Anthony T.; Pavuna, Davor; Pindak, Ron; Božović, Ivan

    2016-01-01

    We studied structural changes in a 5 unit cell thick La1.96Sr0.04CuO4 film, epitaxially grown on a LaSrAlO4 substrate with a single unit cell buffer layer, when ultra-high electric fields were induced in the film by applying a gate voltage between the film (ground) and an ionic liquid in contact with it. Measuring the diffraction intensity along the substrate-defined Bragg rods and analyzing the results using a phase retrieval method we obtained the three-dimensional electron density in the film, buffer layer, and topmost atomic layers of the substrate under different applied gate voltages. The main structural observations were: (i) there were no structural changes when the voltage was negative, holes were injected into the film making it more metallic and screening the electric field; (ii) when the voltage was positive, the film was depleted of holes becoming more insulating, the electric field extended throughout the film, the partial surface monolayer became disordered, and equatorial oxygen atoms were displaced towards the surface; (iii) the changes in surface disorder and the oxygen displacements were both reversed when a negative voltage was applied; and (iv) the c-axis lattice constant of the film did not change in spite of the displacement of equatorial oxygen atoms. PMID:27578237

  17. Oxygen Displacement in Cuprates under IonicLiquid Field-Effect Gating

    DOE PAGESBeta

    Dubuis, Guy; Yacoby, Yizhak; Zhou, Hua; He, Xi; Bollinger, Anthony T.; Pavuna, Davor; Pindak, Ron; Bozovic, Ivan

    2016-08-15

    We studied structural changes in a 5 unit cell thick La1.96Sr0.04CuO4 film, epitaxially grown on a LaSrAlO4 substrate with a single unit cell buffer layer, when ultra-high electric fields were induced in the film by applying a gate voltage between the film and an ionic liquid in contact with it. Measuring the diffraction intensity along the substrate-defined Bragg rods and analyzing the results using a phase retrieval method we obtained the three-dimensional electron density in the film, buffer layer, and topmost atomic layers of the substrate under different applied gate voltages. The main structural observations were: (i) there were nomore » structural changes when the voltage was negative, holes were injected into the film making it more metallic and screening the electric field; (ii) when the voltage was positive, the film was depleted of holes becoming more insulating, the electric field extended throughout the film, the partial surface monolayer became disordered, and planar oxygen atoms were displaced towards the sample surface; (iii) the changes in surface disorder and the oxygen displacements were both reversed when a negative voltage was applied; and (iv) the c-axis lattice constant of the film did not change in spite of the displacement of planar oxygen atoms.« less

  18. Topological BF field theory description of topological insulators

    SciTech Connect

    Cho, Gil Young; Moore, Joel E.

    2011-06-15

    Research Highlights: > We show that a BF theory is the effective theory of 2D and 3D topological insulators. > The non-gauge-invariance of the bulk theory yields surface terms for a bosonized Dirac fermion. > The 'axion' term in electromagnetism is correctly obtained from gapped surfaces. > Generalizations to possible fractional phases are discussed in closing. - Abstract: Topological phases of matter are described universally by topological field theories in the same way that symmetry-breaking phases of matter are described by Landau-Ginzburg field theories. We propose that topological insulators in two and three dimensions are described by a version of abelian BF theory. For the two-dimensional topological insulator or quantum spin Hall state, this description is essentially equivalent to a pair of Chern-Simons theories, consistent with the realization of this phase as paired integer quantum Hall effect states. The BF description can be motivated from the local excitations produced when a {pi} flux is threaded through this state. For the three-dimensional topological insulator, the BF description is less obvious but quite versatile: it contains a gapless surface Dirac fermion when time-reversal-symmetry is preserved and yields 'axion electrodynamics', i.e., an electromagnetic E . B term, when time-reversal symmetry is broken and the surfaces are gapped. Just as changing the coefficients and charges of 2D Chern-Simons theory allows one to obtain fractional quantum Hall states starting from integer states, BF theory could also describe (at a macroscopic level) fractional 3D topological insulators with fractional statistics of point-like and line-like objects.

  19. 5 V driving organic non-volatile memory transistors with poly(vinyl alcohol) gate insulator and poly(3-hexylthiophene) channel layers

    NASA Astrophysics Data System (ADS)

    Nam, Sungho; Seo, Jooyeok; Kim, Hwajeong; Kim, Youngkyoo

    2015-10-01

    Organic non-volatile memory devices were fabricated by employing organic field-effect transistors (OFETs) with poly(vinyl alcohol) (PVA) and poly(3-hexylthiophene) as a gate insulating layer and a channel layer, respectively. The 10-nm-thick nickel layers were inserted for better charge injection between the channel layer and the top source/drain electrodes. The fabricated PVA-OFET memory devices could be operated at low voltages (≤5 V) and showed pronounced hysteresis characteristics in the transfer curves, even though very small hysteresis was measured from the output curves. The degree of hysteresis was considerably dependent on the ratio of channel width (W) to channel length (L). The PVA-OFET memory device with the smaller W/L ratio (25) exhibited better retention characteristics upon 700 cycles of writing-reading-erasing-reading operations, which was assigned to the stability of charged states in devices.

  20. Ambipolar ballistic electron emission microscopy studies of gate-field modified Schottky barriers

    NASA Astrophysics Data System (ADS)

    Che, Y. L.; Pelz, J. P.

    2010-06-01

    Four-terminal ambipolar ballistic electron emission microscopy studies are conducted on Au/Si and Cu/Si Schottky contacts fabricated on back-gated silicon-on-insulator wafers, allowing the electric field to be varied so that both electron (n)- and hole (p)-Schottky barrier heights can be measured at the same sample location. While the individual n- and p-Schottky barrier heights varied by more than 200 meV between the Au/Si and Cu/Si contacts, for a given sample they sum to within 15 meV of the same value, indicating that the individual variations are due to variations in a local surface dipole as compared with tip effects or variations in local composition.

  1. Low-voltage pentacene thin-film transistors with Ta{sub 2}O{sub 5} gate insulators and their reversible light-induced threshold voltage shift

    SciTech Connect

    Liang Yan; Dong Guifang; Hu Yan; Wang Liduo; Qiu Yong

    2005-03-28

    We have fabricated pentacene thin-film transistors using Ta{sub 2}O{sub 5} films prepared by magnetron reactive sputtering as gate insulators. These transistors exhibit good electrical characteristics at an operating voltage as low as 5 V, with a field-effect mobility of 0.32 cm{sup 2}/Vs, an on/off ratio of 10{sup 4}, and a subthreshold slope of 0.5 V/decade. We have also investigated the optical properties of these transistors and observed a reversible light-induced threshold voltage shift. Under illumination, the threshold voltage shifts towards the positive direction while the field-effect mobility and on/off ratio remain almost unchanged. In the dark, however, the threshold voltage can slowly be restored to its original state. At a gate voltage of -5 V, the transistors show a broadband responsivity of 3.7 A/W after illumination at 60 {mu}W/cm{sup 2} for 10 min.

  2. Insulation.

    ERIC Educational Resources Information Center

    Rhea, Dennis

    This instructional unit is one of 10 developed by students on various energy-related areas that deals specifically with insulation. Its objective is for the student to be able to determine insulation needs of new or existing structures, select type to use, use installation techniques, calculate costs, and apply safety factors. Some topics covered…

  3. Investigation of negative bias temperature instability dependence on fin width of silicon-on-insulator-fin-based field effect transistors

    SciTech Connect

    Young, Chadwin D. Wang, Zhe; Neugroschel, Arnost; Majumdar, Kausik; Matthews, Ken; Hobbs, Chris

    2015-01-21

    The fin width dependence of negative bias temperature instability (NBTI) of double-gate, fin-based p-type Field Effect Transistors (FinFETs) fabricated on silicon-on-insulator (SOI) wafers was investigated. The NBTI degradation increased as the fin width narrowed. To investigate this phenomenon, simulations of pre-stress conditions were employed to determine any differences in gate oxide field, fin band bending, and electric field profile as a function of the fin width. The simulation results were similar at a given gate stress bias, regardless of the fin width, although the threshold voltage was found to increase with decreasing fin width. Thus, the NBTI fin width dependence could not be explained from the pre-stress conditions. Different physics-based degradation models were evaluated using specific fin-based device structures with different biasing schemes to ascertain an appropriate model that best explains the measured NBTI dependence. A plausible cause is an accumulation of electrons that tunnel from the gate during stress into the floating SOI fin body. As the fin narrows, the sidewall device channel moves in closer proximity to the stored electrons, thereby inducing more band bending at the fin/dielectric interface, resulting in a higher electric field and hole concentration in this region during stress, which leads to more degradation. The data obtained in this work provide direct experimental proof of the effect of electron accumulation on the threshold voltage stability in FinFETs.

  4. Improvement in performance of solution-processed indium-zinc-tin oxide thin-film transistors by UV/O3 treatment on zirconium oxide gate insulator

    NASA Astrophysics Data System (ADS)

    Naik, Bukke Ravindra; Avis, Christophe; Delwar Hossain Chowdhury, Md; Kim, Taehun; Lin, Tengda; Jang, Jin

    2016-03-01

    We studied solution-processed amorphous indium-zinc-tin oxide (a-IZTO) thin-film transistors (TFTs) with spin-coated zirconium oxide (ZrOx) as the gate insulator. The ZrOx gate insulator was used without and with UV/O3 treatment. The TFTs with an untreated ZrOx gate dielectric showed a saturation mobility (μsat) of 0.91 ± 0.29 cm2 V-1 s-1, a threshold voltage (Vth) of 0.28 ± 0.36 V, a subthreshold swing (SS) of 199 ± 37.17 mV/dec, and a current ratio (ION/IOFF) of ˜107. The TFTs with a UV/O3-treated ZrOx gate insulator exhibited μsat of 2.65 ± 0.43 cm2 V-1 s-1, Vth of 0.44 ± 0.35 V, SS of 133 ± 24.81 mV/dec, and ION/IOFF of ˜108. Hysteresis was 0.32 V in the untreated TFTs and was eliminated by UV/O3 treatment. Also, the leakage current decreased significantly when the IZTO TFT was coated onto a UV/O3-treated ZrOx gate insulator.

  5. Printable Top-Gate-Type Polymer Light-Emitting Transistors with Surfaces of Amorphous Fluoropolymer Insulators Modified by Vacuum Ultraviolet Light Treatment

    NASA Astrophysics Data System (ADS)

    Kajii, Hirotake; Terashima, Daiki; Kusumoto, Yusuke; Ikezoe, Ikuya; Ohmori, Yutaka

    2013-04-01

    We investigated the fabrication and electrical and optical properties of top-gate-type polymer light-emitting transistors with the surfaces of amorphous fluoropolymer insulators, CYTOP (Asahi Glass) modified by vacuum ultraviolet light (VUV) treatment. The surface energy of CYTOP, which has a good solution barrier property was increased by VUV irradiation, and the gate electrode was fabricated by solution processing on the CYTOP film using the Ag nano-ink. The influence of VUV irradiation on the optical properties of poly(9,9-dioctylfluorene-co-benzothiadiazole) (F8BT) films with various gate insulators was investigated to clarify the passivation effect of gate insulators. It was found that the poly(methyl methacrylate) (PMMA) film prevented the degradation of the F8BT layer under VUV irradiation because the PMMA film can absorb VUV. The solution-processed F8BT device with multilayer PMMA/CYTOP insulators utilizing a gate electrode fabricated using the Ag nano-ink exhibited both the ambipolar characteristics and yellow-green emission.

  6. Inversion gate capacitance of undoped single-gate and double-gate field-effect transistor geometries in the extreme quantum limit

    SciTech Connect

    Majumdar, Amlan

    2015-05-28

    We present first-principle analytical derivations and numerically modeled data to show that the gate capacitance per unit gate area C{sub G} of extremely thin undoped-channel single-gate and double-gate field-effect transistor geometries in the extreme quantum limit with single-subband occupancy can be written as 1/C{sub G} = 1/C{sub OX} + N{sub G}/C{sub DOS} + N{sub G}/ηC{sub WF}, where N{sub G} is the number of gates, C{sub OX} is the oxide capacitance per unit area, C{sub DOS} is the density-of-states capacitance per unit area, C{sub WF} is the wave function spreading capacitance per unit area, and η is a constant on the order of 1.

  7. A High Temperature Silicon Carbide mosfet Power Module With Integrated Silicon-On-Insulator-Based Gate Drive

    SciTech Connect

    Wang, Zhiqiang; Shi, Xiaojie; Tolbert, Leon M.; Wang, Fei Fred; Liang, Zhenxian; Costinett, Daniel; Blalock, Benjamin J.

    2014-04-30

    Here we present a board-level integrated silicon carbide (SiC) MOSFET power module for high temperature and high power density application. Specifically, a silicon-on-insulator (SOI)-based gate driver capable of operating at 200°C ambient temperature is designed and fabricated. The sourcing and sinking current capability of the gate driver are tested under various ambient temperatures. Also, a 1200 V/100 A SiC MOSFET phase-leg power module is developed utilizing high temperature packaging technologies. The static characteristics, switching performance, and short-circuit behavior of the fabricated power module are fully evaluated at different temperatures. Moreover, a buck converter prototype composed of the SOI gate driver and SiC power module is built for high temperature continuous operation. The converter is operated at different switching frequencies up to 100 kHz, with its junction temperature monitored by a thermosensitive electrical parameter and compared with thermal simulation results. The experimental results from the continuous operation demonstrate the high temperature capability of the power module at a junction temperature greater than 225°C.

  8. A High Temperature Silicon Carbide mosfet Power Module With Integrated Silicon-On-Insulator-Based Gate Drive

    DOE PAGESBeta

    Wang, Zhiqiang; Shi, Xiaojie; Tolbert, Leon M.; Wang, Fei Fred; Liang, Zhenxian; Costinett, Daniel; Blalock, Benjamin J.

    2014-04-30

    Here we present a board-level integrated silicon carbide (SiC) MOSFET power module for high temperature and high power density application. Specifically, a silicon-on-insulator (SOI)-based gate driver capable of operating at 200°C ambient temperature is designed and fabricated. The sourcing and sinking current capability of the gate driver are tested under various ambient temperatures. Also, a 1200 V/100 A SiC MOSFET phase-leg power module is developed utilizing high temperature packaging technologies. The static characteristics, switching performance, and short-circuit behavior of the fabricated power module are fully evaluated at different temperatures. Moreover, a buck converter prototype composed of the SOI gate drivermore » and SiC power module is built for high temperature continuous operation. The converter is operated at different switching frequencies up to 100 kHz, with its junction temperature monitored by a thermosensitive electrical parameter and compared with thermal simulation results. The experimental results from the continuous operation demonstrate the high temperature capability of the power module at a junction temperature greater than 225°C.« less

  9. Nanoscale thickness double-gated field effect silicon sensors for sensitive pH detection in fluid

    SciTech Connect

    Elibol, Oguz H.; Reddy, Bobby Jr.; Bashir, Rashid

    2008-05-12

    In this work, we report on the optimization of a double-gate silicon-on-insulator field effect device operation to maximize pH sensitivity. The operating point can be fine tuned by independently biasing the fluid and the back gate of the device. Choosing the bias points such that device is nearly depleted results in an exponential current response--in our case, 0.70 decade per unit change in pH. This value is comparable to results obtained with devices that have been further scaled in width, reported at the forefront of the field, and close to the ideal value of 1 decade/pH. By using a thin active area, sensitivity is increased due to increased coupling between the two conducting surfaces of the devices.

  10. Low-voltage operation of Si-based ferroelectric field effect transistors using organic ferroelectrics, poly(vinylidene fluoride-trifluoroethylene), as a gate dielectric

    NASA Astrophysics Data System (ADS)

    Miyata, Yusuke; Yoshimura, Takeshi; Ashida, Atsushi; Fujimura, Norifumi

    2016-04-01

    Si-based metal-ferroelectric-semiconductor (MFS) capacitors have been fabricated using poly(vinylidene fluoride-trifluoroethylene) [P(VDF-TrFE)] as a ferroelectric gate. The pinhole-free P(VDF-TrFE) thin films with high resistivity were able to be prepared by spin-coating directly onto hydrogen-terminated Si. The capacitance-voltage (C-V) characteristics of the ferroelectric gate field effect transistor (FeFET) using this MFS structure clearly show butterfly-shaped hysteresis originating from the ferroelectricity, indicating carrier modulation on the Si surface at gate voltages below 2 V. The drain current-gate voltage (I D-V G) characteristics also show counterclockwise hysteresis at gate voltages below 5 V. This is the first report on the low-voltage operation of a Si-based FeFET using P(VDF-TrFE) as a gate dielectric. This organic gate FeFET without any insulator layer at the ferroelectric/Si interface should be one of the promising devices for overcoming the critical issues of the FeFET, such as depolarization field and a decrease in the gate voltage.

  11. Self-aligned-gate AlGaN/GaN heterostructure field-effect transistor with titanium nitride gate

    NASA Astrophysics Data System (ADS)

    Zhang, Jia-Qi; Wang, Lei; Li, Liu-An; Wang, Qing-Peng; Jiang, Ying; Zhu, Hui-Chao; Ao, Jin-Ping

    2016-08-01

    Self-aligned-gate heterostructure field-effect transistor (HFET) is fabricated using a wet-etching method. Titanium nitride (TiN) is one kind of thermal stable material which can be used as the gate electrode. A Ti/Au cap layer is fixed on the gate and acts as an etching mask. Then the T-shaped gate is automatically formed through over-etching the TiN layer in 30% H2O2 solution at 95 °C. After treating the ohmic region with an inductively coupled plasma (ICP) method, an Al layer is sputtered as an ohmic electrode. The ohmic contact resistance is approximately 0.3 Ω·mm after annealing at a low-temperature of 575 °C in N2 ambient for 1 min. The TiN gate leakage current is only 10‑8 A after the low-temperature ohmic process. The access region length of the self-aligned-gate (SAG) HFET was reduced from 2 μm to 0.3 μm compared with that of the gate-first HFET. The output current density and transconductance of the device which has the same gate length and width are also increased.

  12. Electron mobility in extremely thin single-gate silicon-on-insulator inversion layers

    NASA Astrophysics Data System (ADS)

    Gámiz, F.; Roldán, J. B.; Cartujo-Cassinello, P.; Carceller, J. E.; López-Villanueva, J. A.; Rodriguez, S.

    1999-12-01

    Inversion-layer mobility has been investigated in extremely thin silicon-on-insulator metal-oxide-semiconductor field-effect transistors with a silicon film thickness as low as 5 nm. The Poisson and Schrœdinger equations have been self-consistently solved to take into account inversion layer quantization. To evaluate the electron mobility, the Boltzmann transport equation has been solved by the Monte Carlo method, simultaneously taking into account phonon, surface-roughness, and Coulomb scattering. We show that the reduction of the silicon layer has several effects on the electron mobility: (i) a greater confinement of the electrons in the thin silicon film, which implies an increase in the phonon-scattering rate and therefore a mobility decrease; (ii) a reduction in the conduction effective mass and the intervalley-scattering rate due to the redistribution of carriers in the two subband ladders as a consequence of size quantization resulting in a mobility increase; and (iii) an increase in Coulomb scattering because of a greater number of interface traps in the buried Si-SiO2 and to a closer approach of these charged centers to the mobile carriers. The dependence of these effects on the silicon-layer thickness and on the inversion-charge concentration causes the mobility to be a nontrivial function of these variables. A detailed explanation of the mobility behavior is provided. Mobility for samples with silicon thickness below 10 nm is shown to increase in an electric field range that depends on the charged center concentration, while for silicon layers over 10 nm mobility always decreases as the silicon-layer thickness is reduced.

  13. Low dielectric constant-based organic field-effect transistors and metal-insulator-semiconductor capacitors

    NASA Astrophysics Data System (ADS)

    Ukah, Ndubuisi Benjamin

    This thesis describes a study of PFB and pentacene-based organic field-effect transistors (OFET) and metal-insulator-semiconductor (MIS) capacitors with low dielectric constant (k) poly(methyl methacrylate) (PMMA), poly(4-vinyl phenol) (PVP) and cross-linked PVP (c-PVP) gate dielectrics. A physical method -- matrix assisted pulsed laser evaporation (MAPLE) -- of fabricating all-polymer field-effect transistors and MIS capacitors that circumvents inherent polymer dissolution and solvent-selectivity problems, is demonstrated. Pentacene-based OFETs incorporating PMMA and PVP gate dielectrics usually have high operating voltages related to the thickness of the dielectric layer. Reduced PMMA layer thickness (≤ 70 nm) was obtained by dissolving the PMMA in propylene carbonate (PC). The resulting pentacene-based transistors exhibited very low operating voltage (below -3 V), minimal hysteresis in their transfer characteristics, and decent electrical performance. Also low voltage (within -2 V) operation using thin (≤ 80 nm) low-k and hydrophilic PVP and c-PVP dielectric layers obtained via dissolution in high dipole moment and high-k solvents -- PC and dimethyl sulfoxide (DMSO), is demonstrated to be a robust means of achieving improved electrical characteristics and high operational stability in OFETs incorporating PVP and c-PVP dielectrics.

  14. Low-frequency noise in AlTiO/AlGaN/GaN metal-insulator-semiconductor heterojunction field-effect transistors

    NASA Astrophysics Data System (ADS)

    Le, Son Phuong; Ui, Toshimasa; Nguyen, Tuan Quy; Shih, Hong-An; Suzuki, Toshi-kazu

    2016-05-01

    Using aluminum titanium oxide (AlTiO, an alloy of Al2O3 and TiO2) as a high-k gate insulator, we fabricated and investigated AlTiO/AlGaN/GaN metal-insulator-semiconductor heterojunction field-effect transistors. From current low-frequency noise (LFN) characterization, we find Lorentzian spectra near the threshold voltage, in addition to 1/f spectra for the well-above-threshold regime. The Lorentzian spectra are attributed to electron trapping/detrapping with two specific time constants, ˜25 ms and ˜3 ms, which are independent of the gate length and the gate voltage, corresponding to two trap level depths of 0.5-0.7 eV with a 0.06 eV difference in the AlTiO insulator. In addition, gate leakage currents are analyzed and attributed to the Poole-Frenkel mechanism due to traps in the AlTiO insulator, where the extracted trap level depth is consistent with the Lorentzian LFN.

  15. Porous-Floating-Gate Field-Effect Transistor

    NASA Technical Reports Server (NTRS)

    Thakoor, Anilkumar P.; Moopenn, Alexander W.; Lambe, John J.

    1990-01-01

    Porous-floating-gate, "vertical" field-effect transistor proposed as programmable analog memory device especially suitable for use in electronic neural networks. Analog value of electrical conductance of device represents synaptic weight (strength of synaptic connection) repeatedly modified by application of suitable writing or erasing voltage. Suited for hardware implementations of massively parallel neural-network architectures for two important reasons: vertical transistor structure requires only two external electrodes, and use of tailored amorphous semiconductors provides choice of very wide range of low conductivity values, dictated by overall power dissipation requirements in massively parallel neural-network circuits.

  16. Radio interference and transient field from gas-insulated substations

    SciTech Connect

    Harvey, S.M.; Wong, P.S.; Balma, P.M.

    1995-01-01

    Gas-insulated substations (GIS), owing to their compact nature, offer an attractive alternative to conventional substations in areas where space is limited, such as in urban areas. Consequently, it is important to address the issue of environmental conditions within the substation and in the surrounding areas. This paper reports the result of radio interference (RI) and transient field measurements at two GIS in Ontario, Canada. For comparison with RI levels taken at the GIS, RI levels outside two hospitals in the Toronto area were also measured. The transient field study covers electromagnetic interference (EMI) levels generated during switching operations, and includes measurements inside and outside the GIS. Measurements show that RI levels from the GIS were either below background levels, or contributed little to the background. RI levels outside the GIS and the hospitals were similar. Peak transient field values up to 580 V/m were measured inside the station building, and dropped to background values of 10 V/m at about 120 m from the station. The transient field (E) dropped off at a rate of 3/2 power with distance (d) from the air-insulated 115 kV bus, i.e. E {proportional_to} d{sup {minus}1.5}.

  17. Improved double-gate armchair silicene nanoribbon field-effect-transistor at large transport bandgap

    NASA Astrophysics Data System (ADS)

    Mohsen, Mahmoudi; Zahra, Ahangari; Morteza, Fathipour

    2016-01-01

    The electrical characteristics of a double-gate armchair silicene nanoribbon field-effect-transistor (DG ASiNR FET) are thoroughly investigated by using a ballistic quantum transport model based on non-equilibrium Green’s function (NEGF) approach self-consistently coupled with a three-dimensional (3D) Poisson equation. We evaluate the influence of variation in uniaxial tensile strain, ribbon temperature and oxide thickness on the on-off current ratio, subthreshold swing, transconductance and the delay time of a 12-nm-length ultranarrow ASiNR FET. A novel two-parameter strain magnitude and temperature-dependent model is presented for designing an optimized device possessing balanced amelioration of all the electrical parameters. We demonstrate that employing HfO2 as the gate insulator can be a favorable choice and simultaneous use of it with proper combination of temperature and strain magnitude can achieve better device performance. Furthermore, a general model power (GMP) is derived which explicitly provides the electron effective mass as a function of the bandgap of a hydrogen passivated ASiNR under strain.

  18. Magnetic-field-induced localization in 2D topological insulators.

    PubMed

    Delplace, Pierre; Li, Jian; Büttiker, Markus

    2012-12-14

    Localization of the helical edge states in quantum spin Hall insulators requires breaking time-reversal invariance. In experiments, this is naturally implemented by applying a weak magnetic field B. We propose a model based on scattering theory that describes the localization of helical edge states due to coupling to random magnetic fluxes. We find that the localization length is proportional to B^{-2} when B is small and saturates to a constant when B is sufficiently large. We estimate especially the localization length for the HgTe/CdTe quantum wells with known experimental parameters. PMID:23368362

  19. A novel quantum field approach to photoexcited insulators

    NASA Astrophysics Data System (ADS)

    Klotins, E.

    2016-07-01

    In order to predict optical properties of insulating materials under intensive laser excitation, we generalized methods of quantum electrodynamics, allowing us to simulate excitation of electrons and holes, interacting with each other and acoustic phonons. The prototypical model considers a two-band dielectric material characterized by the dispersion relations for electron and hole states. We developed a universal description of excited electrons, holes and acoustic phonons within joint quantum kinetics formalism. Illustrative solutions for the quasiparticle birth-annihilation operators, applicable at short laser pulses at 0 K, are obtained by the transition from the macroscopic description to the quantum field formalism.

  20. Polymer electrolyte-gated organic field-effect transistors

    NASA Astrophysics Data System (ADS)

    Panzer, Matthew J.

    Contemporary interest in organic semiconductors is driven both by questions regarding the fundamentals of charge transport in these materials and by their potential for flexible, low-cost electronic applications. The key device utilized in these endeavors is the organic field-effect transistor (OFET). Attaining large charge carrier densities in OFETs is desirable for two main reasons. First, because the conductivity in an OFET is proportional to the product of carrier mobility and charge density, increasing charge density levels can boost transistor currents significantly and facilitate low-voltage operation. Additionally, the achievement of carrier densities approaching the twodimensional (2D) molecular density (˜5 x 1014 cm-2) in an organic semiconductor monolayer can enable a variety of fundamental transport experiments. The results summarized in this thesis illustrate that charge densities exceeding 1014 charges/cm2 can be attained in a variety of organic semiconductors by using a solid polymer electrolyte as an OFET dielectric. Polymer electrolytes can provide specific capacitances exceeding 10 muF/cm 2, resulting from the migration of ions within a polymer matrix. By measuring the transient gate displacement current caused by ionic motion in a polymer electrolyte-gated organic field-effect transistor (PEG-FET), large electrostatically-injected charge density values can be calculated; these are typically above 1014 charges/cm2 at gate voltages under 3 V. Negative transconductance at large carrier densities is observed in oligomeric, polymeric, and organic single-crystal semiconductors. This phenomenon is ascribed to charge correlations or a nearly complete filling of the semiconductor transport band with carriers. Polymer semiconductors exhibited the highest performance among PEG-FETs with a top gate architecture. Nearly metallic conductivities (˜1000 S/cm), weak ON current temperature dependences, and large linear mobility values (˜3 cm2/V·s) were

  1. Thermoelectric efficiency of topological insulators in a magnetic field

    NASA Astrophysics Data System (ADS)

    Tretiakov, O. A.; Abanov, Ar.; Sinova, Jairo

    2012-04-01

    We study the thermoelectric properties of three-dimensional topological insulators in magnetic fields with many holes (or pores) in the bulk. We find that at a high density of these holes in the transport direction the thermoelectric figure of merit, ZT, can be large due to the contribution of the topologically protected conducting surfaces and the suppressed phonon thermal conductivity. By applying an external magnetic field, a subgap can be induced in the surface states' spectrum. We show that the thermoelectric efficiency can be controlled by this tunable subgap leading to values of ZT much greater than 1. Such high values of ZT for reasonable system parameters and its tunability by a magnetic field make this system a strong candidate for applications in the heat management of nanodevices, especially at low temperatures.

  2. Electrical characteristics of MoS2 field-effect transistor with ferroelectric vinylidene fluoride-trifluoroethylene copolymer gate structure

    NASA Astrophysics Data System (ADS)

    Kobayashi, Takuhei; Hori, Naoki; Nakajima, Takashi; Kawae, Takeshi

    2016-03-01

    Ferroelectric field-effect transistors (FeFET) based on MoS2 have recently been shown to exhibit considerable potential for use in nano sized non-volatile memory devices. Here, we demonstrated fabrication and characterization of FeFET based on MoS2 channel with vinylidene fluoride (VDF)-trifluoroethylene (TrFE) copolymer as back-gate insulator. In this device, counterclockwise hysteresis behavior was observed in the drain current-gate voltage curve, which is indicative of interaction between MoS2 carrier modulation and ferroelectric polarization switching. Furthermore, our VDF-TrFE/MoS2 FeFET exhibited only n-type behavior, a maximum linear mobility of 625 cm2/V s, a large memory window width of 16 V, and a high on/off current ratio of 8 × 105.

  3. Controlling the metal insulator transition using the ferroelectric field effect in rare earth nickelates

    NASA Astrophysics Data System (ADS)

    Marshall, Matthew; Disa, Ankit; Kumah, Divine; Chen, Hanghui; Ismail-Beigi, Sohrab; Walker, Fred; Ahn, Charles

    2013-03-01

    A ferroelectric field effect transistor (FE-FET) modulates conductivity in a non-volatile manner by electrostatically accumulating and depleting charge carriers at the interface between a conducting channel and ferroelectric gate. The rare earth nickelate LaNiO3 is metallic in bulk, while other rare earth nickelates, such as NdNiO3, exhibit metal-insulator transitions and anti-ferromagnetic behavior in the bulk. Here, we show that by coupling the ferroelectric polarization of Pb0.8Zr0.2TiO3 (PZT) to the carriers in a nickelate, we can dynamically induce a metal- insulator transition in ultra-thin films of LaNiO3, and induce large changes in the MIT transition temperature in NdNiO3. Density functional theory is used to determine changes in the physical and electronic Ni-O-Ni bond angle of the nickelate at the interface between PZT and LaNiO3. The effect of the ferroelectric polarization is to decrease the Ni-O-Ni bond angle from 180 degrees and increase the carrier effective mass. Related to this change in electronic structure, we observe a change in resistivity of approximately 80% at room temperature for an ultra-thin 3 unit cell thick film of LaNiO3. Work supported by FENA and the NSF under MRSEC DMR 1119826.

  4. High-field response of gated graphene at terahertz frequencies

    NASA Astrophysics Data System (ADS)

    Razavipour, Hadi; Yang, Wayne; Guermoune, Abdeladim; Hilke, Michael; Cooke, David G.; Al-Naib, Ibraheem; Dignam, Marc M.; Blanchard, François; Hafez, Hassan A.; Chai, Xin; Ferachou, Denis; Ozaki, Tsuneyuki; Lévesque, Pierre L.; Martel, Richard

    2015-12-01

    We study the Fermi energy level dependence of the nonlinear terahertz (THz) transmission of gated multilayer and single-layer graphene transferred onto sapphire and quartz substrates. The two samples represent two limits of low-field impurity scattering: short-range neutral and long-range charged impurity scattering, respectively. We observe an increase in the transmission as the field amplitude is increased due to intraband absorption bleaching starting at THz fields above 8 kV/cm. This effect arises from a field-induced reduction in THz conductivity that depends strongly on the Fermi energy. We account for intraband absorption using a free carrier Drude model that includes neutral and charged impurity scattering as well as optical phonon scattering. We find that although the Fermi-level dependence in the monolayer and five-layer samples is quite different due to the dominance of long- and short-range momentum scattering, respectively, both exhibit a strong dependence on the field amplitude that cannot be explained on the basis of an increase in the lattice temperature alone. Our results provide a deeper understanding of transport in graphene devices operating at THz frequencies and in modest kV/cm field strengths where nonlinearities exist.

  5. Leakage and field emission in side-gate graphene field effect transistors

    NASA Astrophysics Data System (ADS)

    Di Bartolomeo, A.; Giubileo, F.; Iemmo, L.; Romeo, F.; Russo, S.; Unal, S.; Passacantando, M.; Grossi, V.; Cucolo, A. M.

    2016-07-01

    We fabricate planar graphene field-effect transistors with self-aligned side-gate at 100 nm from the 500 nm wide graphene conductive channel, using a single lithographic step. We demonstrate side-gating below 1 V with conductance modulation of 35% and transconductance up to 0.5 mS/mm at 10 mV drain bias. We measure the planar leakage along the SiO2/vacuum gate dielectric over a wide voltage range, reporting rapidly growing current above 15 V. We unveil the microscopic mechanisms driving the leakage, as Frenkel-Poole transport through SiO2 up to the activation of Fowler-Nordheim tunneling in vacuum, which becomes dominant at higher voltages. We report a field-emission current density as high as 1 μA/μm between graphene flakes. These findings are important for the miniaturization of atomically thin devices.

  6. A 65-kV insulated gate bipolar transistor switch applied in damped AC voltages partial discharge detection system.

    PubMed

    Jiang, J; Ma, G M; Luo, D P; Li, C R; Li, Q M; Wang, W

    2014-02-01

    Damped AC voltages detection system (DAC) is a productive way to detect the faults in power cables. To solve the problems of large volume, complicated structure and electromagnetic interference in existing switches, this paper developed a compact solid state switch based on electromagnetic trigger, which is suitable for DAC test system. Synchronous electromagnetic trigger of 32 Insulated Gate Bipolar Transistors (IGBTs) in series was realized by the topological structure of single line based on pulse width modulation control technology. In this way, external extension was easily achieved. Electromagnetic trigger and resistor-capacitor-diode snubber circuit were optimized to reduce the switch turn-on time and circular layout. Epoxy encapsulating was chosen to enhance the level of partial discharge initial voltage (PDIV). The combination of synchronous trigger and power supply is proposed to reduce the switch volume. Moreover, we have overcome the drawback of the electromagnetic interference and improved the detection sensitivity of DAC by using capacitor storage energy to maintain IGBT gate driving voltage. The experimental results demonstrated that the solid-state switch, with compact size, whose turn-on time was less than 400 ns and PDIV was more than 65 kV, was able to meet the actual demands of 35 kV DAC test system. PMID:24593382

  7. A 65-kV insulated gate bipolar transistor switch applied in damped AC voltages partial discharge detection system

    NASA Astrophysics Data System (ADS)

    Jiang, J.; Ma, G. M.; Luo, D. P.; Li, C. R.; Li, Q. M.; Wang, W.

    2014-02-01

    Damped AC voltages detection system (DAC) is a productive way to detect the faults in power cables. To solve the problems of large volume, complicated structure and electromagnetic interference in existing switches, this paper developed a compact solid state switch based on electromagnetic trigger, which is suitable for DAC test system. Synchronous electromagnetic trigger of 32 Insulated Gate Bipolar Transistors (IGBTs) in series was realized by the topological structure of single line based on pulse width modulation control technology. In this way, external extension was easily achieved. Electromagnetic trigger and resistor-capacitor-diode snubber circuit were optimized to reduce the switch turn-on time and circular layout. Epoxy encapsulating was chosen to enhance the level of partial discharge initial voltage (PDIV). The combination of synchronous trigger and power supply is proposed to reduce the switch volume. Moreover, we have overcome the drawback of the electromagnetic interference and improved the detection sensitivity of DAC by using capacitor storage energy to maintain IGBT gate driving voltage. The experimental results demonstrated that the solid-state switch, with compact size, whose turn-on time was less than 400 ns and PDIV was more than 65 kV, was able to meet the actual demands of 35 kV DAC test system.

  8. Electron transport in bulk-Si NMOSFETs in presence of high-kappa gate insulator: Charge trapping and mobility

    NASA Astrophysics Data System (ADS)

    Maitra, Kingsuk

    Recent advancements in gate stack engineering has led to the development of aggressively scaled, high mobility, high-kappa dielectric based NMOSFETs with metal gates. Most of the current literature on the subject also stressed on the need for a high temperature process step to attain the high mobility under minimal change of effective oxide thickness. However, the physical origin of high mobility is not well understood. In this work, fundamental insight into the necessity of the high temperature process step is provided. Novel experimental strategies are developed to understand the impact of interface states and bulk traps separately and exclusively on channel mobility. It is conjectured that the interface states at the SiO2/(100) bulk-Si interface are identical in nature (as far as coupling with the channel electrons is concerned) to those at the high-kappa/SiO2/(100) bulk-Si interface. Thus, the response of interface states on channel electrons in high-kappa insulator based NMOSFETs is properly calibrated by a novel thermal desorption of hydrogen experiment on SiO2/(100) bulk-Si NMOSFETs to yield a highly accurate parameterized equation. The value of interface state response parameter determined by the aforementioned experiment is compared with theoretical predictions, and independently determined projections from electrical stress measurements. The impact of transient charging on transport in the channel is investigated. It is conclusively shown that remote charge has minimal impact on mobility in the channel. The role of nitrogen induced fixed oxide charge is studied on a set of Hf-silicate samples. Role of soft optical phonon scattering and the beneficial impact of metal gates on soft optical phonon limited mobility are thoroughly investigated both theoretically and experimentally. Conclusions are drawn on the fundamental limit of mobility attainable in high-kappa dielectric based NMOSFETs.

  9. Electric field-induced transport modulation in VO2 FETs with high-k oxide/organic parylene-C hybrid gate dielectric

    NASA Astrophysics Data System (ADS)

    Wei, Tingting; Kanki, Teruo; Fujiwara, Kohei; Chikanari, Masashi; Tanaka, Hidekazu

    2016-02-01

    We report on the observation of reversible and immediate resistance switching by high-k oxide Ta2O5/organic parylene-C hybrid dielectric-gated VO2 thin films. Resistance change ratios at various temperatures in the insulating regime were demonstrated to occur in the vicinity of phase transition temperature. We also found an asymmetric hole-electron carrier modulation related to the suppression of phase transition temperature. The results in this research provide a possibility for clarifying the origin of metal-insulator transition in VO2 through the electrostatic field-induced transport modulation.

  10. Experimental Observation of a Metal-insulator Transition in 2D at Zero Magnetic Field

    NASA Astrophysics Data System (ADS)

    Kravchenko, S. V.

    1996-03-01

    The scaling theory of Abrahams et al. ^1 has had considerable success in describing many features of metal-insulator transitions. Within this theory, which was developed for non-interacting electrons, no such transition is possible in two-dimensional electron systems (2DES) in the absence of a magnetic field. However, we show experimentally that an ultra-high-mobility 2DES on the surface of silicon does exhibit the signature of a true metal-insulator phase transition at zero magnetic field at a critical electron density n_c ~10^11 cm-2. The energy of electron-electron interactions, ignored in the scaling theory,^1 is the dominant parameter in this 2DES. The resistivity, ρ, is empirically found to scale near the critical point both with temperature T and electric field E so that it can be represented by the form ρ(T,n_s)=ρ(T/T_0(n_s)) as Earrow0 or ρ(E,n_s)=ρ(E/E_0(n_s)) as Tarrow0. At the transition, the resistivity is close to 3h/e^2. Both scaling parameters, T0 and E_0, show power law behavior at the critical point. This is characteristic of a true phase transition and strongly resembles, in particular, the superconductor-insulator transition in disordered thin films,^2 as well as the transition between quantum Hall liquid and insulator.^3 Many high-mobility samples from two different sources (Institute for Metrological Service, Russia, and Siemens AG, Germany) with different oxide thicknesses and gate materials have been studied and similar results were found. Work done in collaboration with J. E. Furneaux, Whitney Mason, V. M. Pudalov, and M. D'Iorio, supported by NSF. ^1 E. Abrahams, P. W. Anderson, D. C. Licciardello, and T. V. Ramakrishnan, Phys. Rev. Lett. 42, 673 (1979). ^2 Y. Liu, K. A. McGreer, B. Nease, D. B. Haviland, G. Martinez, J. W. Halley, and A. M. Goldman, Phys. Rev. Lett. 67, 2068 (1991). ^3 T. Wang, K. P. Clark, G. F. Spencer, A. M. Mack, and W. P. Kirk, Phys. Rev. Lett. 72, 709 (1994).

  11. Resistance modulation in VO2 nanowires induced by an electric field via air-gap gates

    NASA Astrophysics Data System (ADS)

    Kanki, Teruo; Chikanari, Masashi; Wei, Tingting; Tanaka, Hidekazu; The Institute of Scientific; Industrial Research Team

    Vanadium dioxide (VO2) shows huge resistance change with metal-insulator transition (MIT) at around room temperature. Controlling of the MIT by applying an electric field is a topical ongoing research toward the realization of Mott transistor. In this study, we have successfully switched channel resistance of VO2 nano-wire channels by a pure electrostatic field effect using a side-gate-type field-effect transistor (SG-FET) viaair gap and found that single crystalline VO2 nanowires and the channels with narrower width enhance transport modulation rate. The rate of change in resistance ((R0-R)/R, where R0 and R is the resistance of VO2 channel with off state and on state gate voltage (VG) , respectively) was 0.42 % at VG = 30 V in in-plane poly-crystalline VO2 channels on Al2O3(0001) substrates, while the rate in single crystalline channels on TiO2 (001) substrates was 3.84 %, which was 9 times higher than that using the poly-crystalline channels. With reducing wire width from 3000 nm to 400 nm of VO2 on TiO2 (001) substrate, furthermore, resistance modulation ratio enhanced from 0.67 % to 3.84 %. This change can not be explained by a simple free-electron model. In this presentation, we will compare the electronic properties between in-plane polycrystalline VO2 on Al2O3 (0001) and single crystalline VO2 on TiO2 (001) substrates, and show experimental data in detail..

  12. Evolutionary Based Techniques for Fault Tolerant Field Programmable Gate Arrays

    NASA Technical Reports Server (NTRS)

    Larchev, Gregory V.; Lohn, Jason D.

    2006-01-01

    The use of SRAM-based Field Programmable Gate Arrays (FPGAs) is becoming more and more prevalent in space applications. Commercial-grade FPGAs are potentially susceptible to permanently debilitating Single-Event Latchups (SELs). Repair methods based on Evolutionary Algorithms may be applied to FPGA circuits to enable successful fault recovery. This paper presents the experimental results of applying such methods to repair four commonly used circuits (quadrature decoder, 3-by-3-bit multiplier, 3-by-3-bit adder, 440-7 decoder) into which a number of simulated faults have been introduced. The results suggest that evolutionary repair techniques can improve the process of fault recovery when used instead of or as a supplement to Triple Modular Redundancy (TMR), which is currently the predominant method for mitigating FPGA faults.

  13. Peptide mass fingerprinting using field-programmable gate arrays.

    PubMed

    Bogdan, I A; Coca, D; Beynon, R J

    2009-06-01

    The reconfigurable computing paradigm, which exploits the flexibility and versatility of field-programmable gate arrays (FPGAs), has emerged as a powerful solution for speeding up time-critical algorithms. This paper describes a reconfigurable computing solution for processing raw mass spectrometric data generated by MALDI-TOF instruments. The hardware-implemented algorithms for denoising, baseline correction, peak identification, and deisotoping, running on a Xilinx Virtex-2 FPGA at 180 MHz, generate a mass fingerprint that is over 100 times faster than an equivalent algorithm written in C, running on a Dual 3-GHz Xeon server. The results obtained using the FPGA implementation are virtually identical to those generated by a commercial software package MassLynx. PMID:23853215

  14. Field Programmable Gate Arrays—Detecting Cosmic Rays

    NASA Astrophysics Data System (ADS)

    Dasgupta, S.; Cussans, D.

    2015-07-01

    Field Programmable Gate Arrays (FPGAs) are finding extensive application in instrumentation for particle physics experiments. A table-top framework is developed using FPGA-based hardware to detect the coincidence of signals produced by cosmic rays in multiple detectors. The rates of the detector signals and coincidence output are also measured. The logic is programmed inside an FPGA mounted on a Xilinx evaluation board. Control and data readout are carried out using IPbus, a gigabit Ethernet-based protocol developed as part of upgrading the Compact Muon Solenoid (CMS) experiment at the Large Hadron Collider (LHC) . The framework is appropriate for introducing students to FPGA-based instrumentation and providing them with a practical experience of working with such hardware.

  15. Evolution of Modes in Magnetically Insulated Crossed Field Diodes

    NASA Astrophysics Data System (ADS)

    Takeall, S.; Greenwood, A.; Cartwright, K.; Fleming, T.; Mardahl, P.; Lau, Y. Y.; Roderick, N.

    2006-10-01

    The time-dependent behavior of electron sheaths in a magnetically insulated B>BHull anode-cathode gap with crossed electric and magnetic fields is studied. The crossed-field, space-charge limited diode is modeled for various magnetic fields by means of multidimensional (1d and 2d), self consistent, electromagnetic, particle-in-cell (PIC) simulations in both cylindrical and planar geometries. The transient behavior of the system is examined in detail and is divided into three separate stages: cycloidal flow, collapse of cycloidal flow and sheared (near-Brillouin) flow. Our 2d electromagnetic PIC simulations (both planar and cylindrical) show that cycloidal flow also collapses into a perturbed flow that is dominated by the E cross B drift, but is neither steady nor stable. This observed cycloidal flow instability is a kinetic mode, not a fluid mode such as the magnetron or diocotron instability. The growth of the kinetic mode is faster than that of either of the above mentioned fluid instabilities. After the kinetic mode saturates, the fastest growing fluid mode grows to dominate the system. The SWS is added by three different methods to separate the RF effects from the DC electric field effects created by the SWS. The first method is to add a circuit to the anode that does not effect the DC electric fields, the second is to add the SWS by placing a thin dielectric (with and unphysical large dielectric constant), and last is to add the geometric SWS.

  16. Investigation of field induced trapping on floating gates

    NASA Technical Reports Server (NTRS)

    Gosney, W. M.

    1975-01-01

    The development of a technology for building electrically alterable read only memories (EAROMs) or reprogrammable read only memories (RPROMs) using a single level metal gate p channel MOS process with all conventional processing steps is outlined. Nonvolatile storage of data is achieved by the use of charged floating gate electrodes. The floating gates are charged by avalanche injection of hot electrodes through gate oxide, and discharged by avalanche injection of hot holes through gate oxide. Three extra diffusion and patterning steps are all that is required to convert a standard p channel MOS process into a nonvolatile memory process. For identification, this nonvolatile memory technology was given the descriptive acronym DIFMOS which stands for Dual Injector, Floating gate MOS.

  17. Field evaluation of 69-kV outdoor Polysil reg sign insulators

    SciTech Connect

    Richenbacher, A.G. )

    1990-03-01

    This report, together with previous interim reports, documents and summarizes the field performance of 69 kV Polysil{reg sign} insulators during the field trial period from January, 1983 to December, 1988. These insulators were manufactured for the Electric Power Research Institute by Lindsey Industries in 1979. A description of the insulator development and manufacturing process is contained in the EPRI Final Report EL1281-1. Following their manufacture, the insulators were delivered, in the form of test racks of 17 Polysil{reg sign} insulators and one porcelain insulator, to twelve United States utilities and the Instituto de Investigaciones Electricas (IIE) in Mexico. These racks were subsequently installed and energized at twenty-five test sites during the latter half of 1979 and early 1980 by the project participants for the purpose of analyzing the outdoor field performance of these insulators and comparing the relative effect on performance of variations in composition, coating, electrical grading method, and shape represented by individual insulators within the test racks. This report documents the effects of the various Polysil{reg sign} insulator parameters on electrical performance in the field over a specific period of 6 years. However, the insulators had been energized for approximately 3 years prior to the initiation of this project and, although specific performance data is not available for that time period, the overall effects of field exposure for that additional time period (total of 9 years) are seen in the results of this report. 3 refs., 23 figs., 9 tabs.

  18. Enhanced electrical properties of pentacene-based organic thin-film transistors by modifying the gate insulator surface

    NASA Astrophysics Data System (ADS)

    Tang, J. X.; Lee, C. S.; Chan, M. Y.; Lee, S. T.

    2008-09-01

    A reliable surface treatment for the pentacene/gate dielectric interface was developed to enhance the electrical transport properties of organic thin-film transistors (OTFTs). Plasma-polymerized fluorocarbon (CFx) film was deposited onto the SiO 2 gate dielectric prior to pentacene deposition, resulting in a dramatic increase of the field-effect mobility from 0.015 cm 2/(V s) to 0.22 cm 2/(V s), and a threshold voltage reduction from -14.0 V to -9.9 V. The observed carrier mobility increase by a factor of 10 in the resulting OTFTs is associated with various growth behaviors of polycrystalline pentacene thin films on different substrates, where a pronounced morphological change occurs in the first few molecular layers but the similar morphologies in the upper layers. The accompanying threshold voltage variation suggests that hole accumulation in the conduction channel-induced weak charge transfer between pentacene and CFx.

  19. Evolution of Modes in Magnetically Insulated Crossed-Field Diodes

    NASA Astrophysics Data System (ADS)

    Cartwright, Keith

    2005-10-01

    The time-dependent behavior of electron sheaths in a magnetically insulated B>BHull anode-cathode gap with crossed electric and magnetic fields is studied. The crossed-field, diode is modeled for various magnetic fields by means of multidimensional (1d and 2d), self-consistent, electromagnetic, particle-in-cell (PIC) simulations. The transient behavior of the system is examined in detail and is divided into three separate stages: cycloidal flow, collapse of cycloidal flow and sheared (near-Brillouin) flow. It has been shown in 1d planar geometry that the cycloidal flows collapse into a steady, near-Brillouin flow. Our 2d electromagnetic PIC simulations (both planar and cylindrical) show that cycloidal flows also collapses into a flow that is dominated by the E cross B drift, but is neither steady nor stable. The growth of the kinetic mode is faster than that of either magnetron or diocotron fluid instability. After the kinetic mode saturates, the fastest growing fluid mode grows to dominate the system. A slow wave structure (SWS) is added to the anode that matches the wavelength and frequency of the fastest growing fluid instability. The SWS is then perturbed so that wavelength and/or frequency does not match the smooth bore diode growth rate and the region of `lock-in' to the SWS is found. This work is supported by a grant from AFOSR.

  20. Range-gated imaging for near-field target identification

    SciTech Connect

    Yates, G.J.; Gallegos, R.A.; McDonald, T.E.

    1996-12-01

    The combination of two complementary technologies developed independently at Los Alamos National Laboratory (LANL) and Sandia National Laboratory (SNL) has demonstrated feasibility of target detection and image capture in a highly light-scattering, medium. The technique uses a compact SNL developed Photoconductive Semiconductor Switch/Laser Diode Array (PCSS/LDA) for short-range (distances of 8 to 10 m) large Field-Of-View (FOV) target illumination. Generation of a time-correlated echo signal is accomplished using a photodiode. The return image signal is recorded with a high-speed shuttered Micro-Channel-Plate Image Intensifier (MCPII), declined by LANL and manufactured by Philips Photonics. The MCPII is rated using a high-frequency impedance-matching microstrip design to produce 150 to 200 ps duration optical exposures. The ultra first shuttering producer depth resolution of a few inches along the optic axis between the MCPII and the target, producing enhanced target images effectively deconvolved from noise components from the scattering medium in the FOV. The images from the MCPII are recorded with an RS-170 Charge-Coupled-Device camera and a Big Sky, Beam Code, PC-based digitizer frame grabber and analysis package. Laser pulse data were obtained by the but jitter problems and spectral mismatches between diode spectral emission wavelength and MCPII photocathode spectral sensitivity prevented the capture of fast gating imaging with this demonstration system. Continued development of the system is underway.

  1. Start Up Application Concerns with Field Programmable Gate Arrays (FPGAs)

    NASA Technical Reports Server (NTRS)

    Katz, Richard B.

    1999-01-01

    This note is being published to improve the visibility of this subject, as we continue to see problems surface in designs, as well as to add additional information to the previously published note for design engineers. The original application note focused on designing systems with no single point failures using Actel Field Programmable Gate Arrays (FPGAs) for critical applications. Included in that note were the basic principles of operation of the Actel FPGA and a discussion of potential single-point failures. The note also discussed the issue of startup transients for that class of device. It is unfortunate that we continue to see some design problems using these devices. This note will focus on the startup properties of certain electronic components, in general, and current Actel FPGAs, in particular. Devices that are "power-on friendly" are currently being developed by Actel, as a variant of the new SX series of FPGAs. In the ideal world, electronic components would behave much differently than they do in the real world, The chain, of course, starts with the power supply. Ideally, the voltage will immediately rise to a stable V(sub cc) level, of course, it does not. Aside from practical design considerations, inrush current limits of certain capacitors must be observed and the power supply's output may be intentionally slew rate limited to prevent a large current spike on the system power bus. In any event, power supply rise time may range from less than I msec to 100 msec or more.

  2. Infrared light gated MoS₂ field effect transistor.

    PubMed

    Fang, Huajing; Lin, Ziyuan; Wang, Xinsheng; Tang, Chun-Yin; Chen, Yan; Zhang, Fan; Chai, Yang; Li, Qiang; Yan, Qingfeng; Chan, H L W; Dai, Ji-Yan

    2015-12-14

    Molybdenum disulfide (MoS₂) as a promising 2D material has attracted extensive attentions due to its unique physical, optical and electrical properties. In this work, we demonstrate an infrared (IR) light gated MoS₂ transistor through a device composed of MoS₂ monolayer and a ferroelectric single crystal Pb(Mg(1/3)Nb(2/3))O₃-PbTiO₃ (PMN-PT). With a monolayer MoS₂ onto the top surface of (111) PMN-PT crystal, the drain current of MoS₂ channel can be modulated with infrared illumination and this modulation process is reversible. Thus, the transistor can work as a new kind of IR photodetector with a high IR responsivity of 114%/Wcm⁻². The IR response of MoS₂ transistor is attributed to the polarization change of PMN-PT single crystal induced by the pyroelectric effect which results in a field effect. Our result promises the application of MoS₂ 2D material in infrared optoelectronic devices. Combining with the intrinsic photocurrent feature of MoS₂ in the visible range, the MoS₂ on ferroelectric single crystal may be sensitive to a broadband wavelength of light. PMID:26698982

  3. Critical regime for the insulator-metal transition in highly ordered conjugated polymers gated with ionic liquid

    NASA Astrophysics Data System (ADS)

    Ito, Hiroshi; Harada, Tomonori; Tanaka, Hisaaki; Kuroda, Shin-ichi

    2016-03-01

    We report the room-temperature and low-temperature transport properties of a poly(2,5-bis(3-hexadecylthiophene-2-yl)thieno[3,2-b]thiophene) (PBTTT) film gated with an ionic liquid based on 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide at different annealing temperatures of the PBTTT film. By annealing the film up to 235 °C and subsequently cooling it, we observed a ribbonlike structure, as reported. For the 235-°C-annealed (ribbon phase) film, we could apply a higher voltage without any decrease in the channel conductivity than for the 180-°C-annealed (terrace phase) film. As a result, a charge mobility as high as 10 cm2 V-1 s-1 was achieved for the ribbon-phase film. The power-law behavior of the temperature dependence of the electrical conductivity at low temperatures, indicating the critical regime for the insulator-metal transition, was observed. The ribbon-phase film exhibits an even weaker temperature dependence with a smaller exponent of β = 0.10 than the terrace-phase film.

  4. High-speed electro-thermal modelling of a three-phase insulated gate bipolar transistor inverter power module

    NASA Astrophysics Data System (ADS)

    Zhou, Zhongfu; Igic, Petar

    2010-02-01

    In this article, a high-speed electro-thermal (ET) modelling strategy to predict the junction temperature of insulated gate bipolar transistor (IGBT) devices of a three-phase inverter power module is presented. The temperature-dependent power loss characteristics of IGBT and diode devices are measured and stored in lookup tables, which replace the conventional complicated physics-based compact models. An inverter is modelled as a voltage controlled voltage source, which allows the inverter-based power train simulation to be carried out in the continuous time domain with a large simulation time-step (1 ms). Using the simulated sinusoidal voltage and current components of the inverter output, the given pulse width modulation mode, the conduction time (duty ratio) and the current of the devices are extracted. Based on the lookup tables, on-times and conduction currents of devices, the average power loss over each simulation time-step is calculated, which is then fed into the inverter thermal model to predict the devices' temperatures. The advantage of the proposed model is that an accurate ET simulation of inverter for long real-time (many minutes) operation can be carried out within an acceptable computational time using a standard modern personal computer. Both simulation and experimental validation have been carried out, and an excellent agreement has been achieved between the simulation and experimental data.

  5. Compact all-optical interferometric logic gates based on one-dimensional metal-insulator-metal structures

    NASA Astrophysics Data System (ADS)

    Bian, Yusheng; Gong, Qihuang

    2014-02-01

    The whole set of fundamental all-optical logic gates is realized theoretically using a multi-channel configuration based on one-dimensional (1D) metal-insulator-metal (MIM) structures by leveraging the linear interference between surface plasmon polariton modes. The working principle and conditions for different logic functions are analyzed and demonstrated numerically by means of the finite element method. In contrast to most of the previous studies that require more than one type of configuration to achieve different logic functions, a single geometry with fixed physical dimensions can realize all fundamental functions in our case studies. It is shown that by switching the optical signals to different input channels, the presented device can realize simple logic functions such as OR, AND and XOR. By adding signal in the control channel, more functions including NOT, XNOR, NAND and NOR can be implemented. For these considered logic functions, high intensity contrast ratios between Boolean logic states "1" and "0" can be achieved at the telecom wavelength. The presented all-optical logic device is simple, compact and efficient. Moreover, the proposed scheme can be applied to many other nano-photonic logic devices as well, thereby potentially offering useful guidelines for their designs and further applications in on-chip optical computing and optical interconnection networks.

  6. Threshold voltage model of junctionless cylindrical surrounding gate MOSFETs including fringing field effects

    NASA Astrophysics Data System (ADS)

    Gupta, Santosh Kumar

    2015-12-01

    2D Analytical model of the body center potential (BCP) in short channel junctionless Cylindrical Surrounding Gate (JLCSG) MOSFETs is developed using evanescent mode analysis (EMA). This model also incorporates the gate bias dependent inner and outer fringing capacitances due to the gate-source/drain fringing fields. The developed model provides results in good agreement with simulated results for variations of different physical parameters of JLCSG MOSFET viz. gate length, channel radius, doping concentration, and oxide thickness. Using the BCP, an analytical model for the threshold voltage has been derived and validated against results obtained from 3D device simulator.

  7. Analysis of DC Characteristics and Small Signal Equivalent Circuit Parameters of GaAs Metal-Semiconductor Field Effect Transistors with Different Gate Lengths and Different Gate Contours by Two-Dimensional Device Simulations

    NASA Astrophysics Data System (ADS)

    Meng, C. C.; Su, J. Y.; Yang, S. M.

    2005-09-01

    The gate length and gate contour of a GaAs metal-semiconductor field effect transistor (MESFET) device play important roles in determining the small signal circuit parameters and large signal breakdown voltage behavior. GaAs MESFETs with different gate lengths and gate contours were studied by the two-dimensional (2-D) semiconductor device simulations to investigate the dependence of small signal circuit parameters and breakdown voltage on gate length and gate contour. The results show that gate length affects small-signal circuit parameter Cgs while gate contour affects Cgd. The breakdown voltage has strong dependence on gate contour and little dependence on gate length.

  8. Use of a hard mask for formation of gate and dielectric via nanofilament field emission devices

    DOEpatents

    Morse, Jeffrey D.; Contolini, Robert J.

    2001-01-01

    A process for fabricating a nanofilament field emission device in which a via in a dielectric layer is self-aligned to gate metal via structure located on top of the dielectric layer. By the use of a hard mask layer located on top of the gate metal layer, inert to the etch chemistry for the gate metal layer, and in which a via is formed by the pattern from etched nuclear tracks in a trackable material, a via is formed by the hard mask will eliminate any erosion of the gate metal layer during the dielectric via etch. Also, the hard mask layer will protect the gate metal layer while the gate structure is etched back from the edge of the dielectric via, if such is desired. This method provides more tolerance for the electroplating of a nanofilament in the dielectric via and sharpening of the nanofilament.

  9. Gate dependent photo-responses of carbon nanotube field effect phototransistors.

    PubMed

    Chen, H Z; Xi, N; Lai, K W C; Chen, L L; Yang, R G; Song, B

    2012-09-28

    Gate dependent photoconductivity of carbon nanotube (CNT) field effect phototransistors (FEPs) was systematically investigated in this study. The photo-response comparisons of CNT FEPs with symmetric and asymmetric metal structures connecting to the same CNT revealed that the gate effect contributed to a sensitivity improvement with a lower dark current, a higher photocurrent, and an enhanced photovoltage. A functionalized asymmetric FEP, fabricated by partially doping the CNT utilizing a polyethylene imine (PEI) polymer, verified that FEPs delivered a better performance by using asymmetric structures. A multi-gate FEP, with three pairs of side-gates that can electrostatically dope different sections of a CNT independently, was fabricated to examine the gate structure dependent photo-responses. Experimental measurements showed an unconventional photocurrent improvement that was weakly dependent on the gate location, which was attributed to the unique charge distribution of one-dimensional semiconductors. PMID:22948041

  10. Assessment of performance potential of MoS{sub 2}-based topological insulator field-effect transistors

    SciTech Connect

    Liu, Leitao; Guo, Jing

    2015-09-28

    It was suggested that single-layer MoS{sub 2} at the 1T′ phase is a topological insulator whose electronic structure can be modulated by a vertical electric field for field-effect transistor (FET) applications [X. Qian, J. Liu, L. Fu, and J. Li, Science 346, 1344 (2014)]. In this work, performance potential of FETs based on vertical field modulation of the topological edge states is assessed by using quantum transport device simulations. To perform efficient device simulations, a phenomenological Hamiltonian is first proposed and validated to capture the effects of electric fields. Because the ON-state conductance is determined by transport through gapless edge states with a long scattering mean free path and the OFF-state conductance by transport through the gapped bulk states, the ON/OFF ratio is sensitive to the channel length, which is different from conventional FETs. Although a high vertical electric field is required to modulate the topological edge state, a reasonably small subthreshold swing of 131 mV/dec can still be achieved for a practical value of the gate insulator thickness.

  11. Switching characteristics of a 4H-SiC insulated-gate bipolar transistor with interface defects up to the nonquasi-static regime

    NASA Astrophysics Data System (ADS)

    Pesic, Iliya; Navarro, Dondee; Fujinaga, Masato; Furui, Yoshiharu; Miura-Mattausch, Mitiko

    2015-04-01

    The switching characteristics of a trench-type 4H-SiC insulated-gate bipolar transistor (IGBT) device with interface defects are analyzed up to the nonquasi-static (NQS) switching regime using reported interface density measurements and device simulation. Collector current degradation characterized by threshold voltage shift to higher gate voltages and reduction of current magnitude due to carrier trapping are observed under quasi-static (QS) simulation condition. At slow switching of the gate voltage, carrier trapping causes a hump in the transient current at the start of conduction. At very fast switching, the current hump is limited by the NQS effect which results to a reduced switching efficiency and increased on-resistance.

  12. A Ferroelectric Gate Field Effect Transistor with a ZnO/Pb(Zr,Ti)O3 Heterostructure Formed on a Silicon Substrate

    NASA Astrophysics Data System (ADS)

    Tanaka, Hiroyuki; Kaneko, Yukihiro; Kato, Yoshihisa

    2008-09-01

    We have developed a ferroelectric gate field effect transistor (FeFET) with a stacked oxide structure of ZnO/Pb(Zr,Ti)O3 (PZT)/SrRuO3 (SRO) on a Pt/SiO2-coated silicon substrate. The PZT film which acted as a ferroelectric gate insulator was completely oriented in the (111) direction. The well oriented PZT film was realized by the insertion of the SRO layer, which electrically acted, together with the bottom Pt layer as a bottom gate electrode. In order to realize a sharp heterointerface of ZnO/PZT, we applied chemical-mechanical-polishing (CMP) to the PZT surface giving rise to a minimized surface roughness of less than 0.65 nm (rms). The ZnO film stacked on the smooth PZT surface exhibited a c-axis orientation. Subsequently, the source and drain electrodes of Pt/Ti were formed on the ZnO surface. With a drain-to-source voltage of 0.1 V, the conduction current through the ZnO/PZT heterointerface was characterized. A large on/off current ratio (Ion/Ioff) higher than 105 was obtained between the gate voltage conditions of +10 and -10 V owing to the polarization reversal of the PZT gate. Notably, the on/off ratio was stable for more than 105 s without the application of gate bias.

  13. Direct-current and radio-frequency characterizations of GaAs metal-insulator-semiconductor field-effect transistors enabled by self-assembled nanodielectrics

    NASA Astrophysics Data System (ADS)

    Lin, H. C.; Kim, S. K.; Chang, D.; Xuan, Y.; Mohammadi, S.; Ye, P. D.; Lu, G.; Facchetti, A.; Marks, T. J.

    2007-08-01

    Direct-current and radio-frequency characterizations of GaAs metal-insulator-semiconductor field-effect transistors (MISFETs) with very thin self-assembled organic nanodielectrics (SANDs) are presented. The application of SAND on compound semiconductors offers unique opportunities for high-performance devices. Thus, 1μm gate-length depletion-mode n-channel SAND/GaAs MISFETs exhibit low gate leakage current densities of 10-2-10-5A/cm2, a maximum drain current of 260mA/mm at 2V forward gate bias, and a maximum intrinsic transconductance of 127mS/mm. These devices achieve a current cutoff frequency (fT) of 10.6GHz and a maximum oscillation frequency (fmax) of 6.9GHz. Nearly hysteresis-free Ids-Vgs characteristics and low flicker noise indicate that a high-quality SAND-GaAs interface is achieved.

  14. Sensing with Advanced Computing Technology: Fin Field-Effect Transistors with High-k Gate Stack on Bulk Silicon.

    PubMed

    Rigante, Sara; Scarbolo, Paolo; Wipf, Mathias; Stoop, Ralph L; Bedner, Kristine; Buitrago, Elizabeth; Bazigos, Antonios; Bouvet, Didier; Calame, Michel; Schönenberger, Christian; Ionescu, Adrian M

    2015-05-26

    Field-effect transistors (FETs) form an established technology for sensing applications. However, recent advancements and use of high-performance multigate metal-oxide semiconductor FETs (double-gate, FinFET, trigate, gate-all-around) in computing technology, instead of bulk MOSFETs, raise new opportunities and questions about the most suitable device architectures for sensing integrated circuits. In this work, we propose pH and ion sensors exploiting FinFETs fabricated on bulk silicon by a fully CMOS compatible approach, as an alternative to the widely investigated silicon nanowires on silicon-on-insulator substrates. We also provide an analytical insight of the concept of sensitivity for the electronic integration of sensors. N-channel fully depleted FinFETs with critical dimensions on the order of 20 nm and HfO2 as a high-k gate insulator have been developed and characterized, showing excellent electrical properties, subthreshold swing, SS ∼ 70 mV/dec, and on-to-off current ratio, Ion/Ioff ∼ 10(6), at room temperature. The same FinFET architecture is validated as a highly sensitive, stable, and reproducible pH sensor. An intrinsic sensitivity close to the Nernst limit, S = 57 mV/pH, is achieved. The pH response in terms of output current reaches Sout = 60%. Long-term measurements have been performed over 4.5 days with a resulting drift in time δVth/δt = 0.10 mV/h. Finally, we show the capability to reproduce experimental data with an extended three-dimensional commercial finite element analysis simulator, in both dry and wet environments, which is useful for future advanced sensor design and optimization. PMID:25817336

  15. Low field magnetoresistance in a 2D topological insulator based on wide HgTe quantum well.

    PubMed

    Olshanetsky, E B; Kvon, Z D; Gusev, G M; Mikhailov, N N; Dvoretsky, S A

    2016-09-01

    Low field magnetoresistance is experimentally studied in a two-dimensional topological insulator (TI) in both diffusive and quasiballistic samples fabricated on top of a wide (14 nm) HgTe quantum well. In all cases a pronounced quasi-linear positive magnetoresistance is observed similar to that found previously in diffusive samples based on a narrow (8 nm) HgTe well. The experimental results are compared with the main existing theoretical models based on different types of disorder: sample edge roughness, nonmagnetic disorder in an otherwise coherent TI and metallic puddles due to locally trapped charges that act like local gate on the sample. The quasiballistic samples with resistance close to the expected quantized values also show a positive low-field magnetoresistance but with a pronounced admixture of mesoscopic effects. PMID:27355623

  16. Low field magnetoresistance in a 2D topological insulator based on wide HgTe quantum well

    NASA Astrophysics Data System (ADS)

    Olshanetsky, E. B.; Kvon, Z. D.; Gusev, G. M.; Mikhailov, N. N.; Dvoretsky, S. A.

    2016-09-01

    Low field magnetoresistance is experimentally studied in a two-dimensional topological insulator (TI) in both diffusive and quasiballistic samples fabricated on top of a wide (14 nm) HgTe quantum well. In all cases a pronounced quasi-linear positive magnetoresistance is observed similar to that found previously in diffusive samples based on a narrow (8 nm) HgTe well. The experimental results are compared with the main existing theoretical models based on different types of disorder: sample edge roughness, nonmagnetic disorder in an otherwise coherent TI and metallic puddles due to locally trapped charges that act like local gate on the sample. The quasiballistic samples with resistance close to the expected quantized values also show a positive low-field magnetoresistance but with a pronounced admixture of mesoscopic effects.

  17. Electric-field control of spin-orbit torque in magnetically doped topological insulators

    NASA Astrophysics Data System (ADS)

    Fan, Yabin; Shao, Qiming; Kou, Xufeng; Upadhyaya, Pramey; Wang, Kang

    Recent advances of spin-orbit torques (SOTs) generated by topological insulators (TIs) have drawn increasing interest to the spin-momentum locking feature of TIs' surface states, which can potentially provide a very efficient means to generate SOTs for spintronic applications. In this presentation, we will show the magnetization switching through current-induced giant SOT in both TI/Cr-doped TI bilayer and uniformly Cr-doped TI films In particular, we show that the current-induced SOT has significant contribution from the spin-momentum locked surface states of TIs. We find that the spin torque efficiency is in general three orders of magnitude larger than those reported in heavy metal/ferromagnetic heterostructures. In the second part, we will present the electric-field control of the giant SOT in magnetically doped TIs, which suggests promising gate-controlled spin-torque device applications. The giant SOT and efficient current-induced magnetization switching exhibited by the magnetic TIs may lead to innovative spintronic applications such as ultralow power dissipation memory and logic devices. We acknowledge the supports from DARPA, FAME, SHINES and ARO programs.

  18. Comparison of electrical characteristics of back- and top-gate Si nanowire field-effect transistors

    NASA Astrophysics Data System (ADS)

    Yoon, Changjoon; Kang, Jeongmin; Yeom, Donghyuk; Jeong, Dong-Young; Kim, Sangsig

    2008-11-01

    Back- and top-gate field-effect transistors (FETs) with channels composed of p-type Si nanowires were fabricated by a conventional photolithographic process and their electrical properties were characterized by conventional current-voltage (I-V) measurements. For a representative top-gate FET, the peak transconductance was enhanced from 2.24 to 72.2 nS, the field-effect mobility from 1.7 to 3.1 cm 2/V s, and the I/I ratio from 2.21 to 2.49×10 6, compared with those of a representative back-gate FET. The observed improvement of the electrical characteristics is mostly attributed to both the top-gate geometry and the relatively thin gate layer.

  19. Organic gate dielectrics for tetracene field effect transistors

    NASA Astrophysics Data System (ADS)

    Bertolazzi, Simone

    Over the last three decades, thin films of organic semiconductors (OS) have been the object of intense research. These films can be used in a wide variety of new-generation optoelectronic devices, such as Organic Light Emitting Diodes (OLED), Organic Field Effect Transistors (OFET) and photovoltaic cells. Recently, vacuum sublimed tetracene films were used to realize the first Organic Light Emitting Field Effect Transistor (OLEFET), which integrates in a single device the current modulation function of a FET with the light generation capability of a LED. The demonstration of OLEFETs is not straightforward. First of all, an efficient integration of optical and electronic functionalities requires the use of a semiconductor with both efficient electroluminescence and good charge transport properties. Secondly, an ambipolar charge transport has to be achieved to produce high performance OLEFETs. Within this context, controlling the dielectric substrate surface chemistry has proven to be an efficient strategy, since it contributes to avoid the suppression of the electron transport induced by the electronic trap states at the dielectric/semiconductor interface. At the same time, the modification of the chemical and physical nature of the dielectric substrate influences the morphology/structure of the organic thin-films, in turn influencing the final device performance. In this work, polycrystalline tetracene thin films - to be incorporated in OLEFETs - were vacuum sublimed on different organic dielectric substrates, including polymers (parylene C, polymethylmethacrylate, polystyrene) and self-assembled monolayers of hexamethyldisilazane (HMDS) and octadecyltrichlorosilane (OTS). The scope of the work was indeed to shed light on the role of the organic dielectric surface in influencing the charge transport properties of tetracene OLEFETs. The tetracene deposition rate was 3.5 A/s, the substrates were kept at room temperature and the pressure inside the vacuum chamber was

  20. Field-Effect Birefringent Spin Lens in Ultrathin Film of Magnetically Doped Topological Insulators

    NASA Astrophysics Data System (ADS)

    Zhao, Lu; Tang, Peizhe; Gu, Bing-Lin; Duan, Wenhui

    2013-09-01

    We investigate the low-energy electron dynamics in two-dimensional ultrathin film of magnetically doped topological insulators in the context of gate-tuned coherent spin manipulation. Our first-principles calculations for such film unambiguously identify its spin-resolved topological band structure arising from spin-orbit coupling and time-reversal symmetry breaking. Exploiting this characteristic, we predict a negative birefraction for chiral electron tunneling through a gate-controlled p-n interface in the film, analogous to optical birefringence. By fine-tuning the gate voltage, a series of unusual phenomena, including electron double focusing, spatial modulation of spin polarizations, and quantum-interference-induced beating patterns, could be efficiently implemented, offering a powerful platform to establish spin-resolved electron optics by all-electrical means.

  1. Flat Panel Light Source with Lateral Gate Structure Based on SiC Nanowire Field Emitters

    NASA Astrophysics Data System (ADS)

    Youh, Meng-Jey; Tseng, Chun-Lung; Jhuang, Meng-Han; Chiu, Sheng-Cheng; Huang, Li-Hu; Gong, Jyun-An; Li, Yuan-Yao

    2015-06-01

    A field-emission light source with high luminance, excellent luminance uniformity, and tunable luminance characteristics with a novel lateral-gate structure is demonstrated. The lateral-gate triode structure comprises SiC nanowire emitters on a Ag cathode electrode and a pair of Ag gate electrodes placed laterally on both sides of the cathode. The simple and cost-effective screen printing technique is employed to pattern the lateral-gates and cathode structure on soda lime glass. The area coverage of the screen-printed cathode and gates on the glass substrate (area: 6 × 8 cm2) is in the range of 2.04% - 4.74% depending on the set of cathode-gate electrodes on the substrate. The lateral-gate structure with its small area coverage exhibits a two-dimensional luminance pattern with high brightness and good luminance uniformity. A maximum luminance of 10952 cd/cm2 and a luminance uniformity of >90% can be achieved with a gate voltage of 500 V and an anode voltage of 4000 V, with an anode current of 1.44 mA and current leakage to the gate from the cathode of about 10%.

  2. Flat Panel Light Source with Lateral Gate Structure Based on SiC Nanowire Field Emitters.

    PubMed

    Youh, Meng-Jey; Tseng, Chun-Lung; Jhuang, Meng-Han; Chiu, Sheng-Cheng; Huang, Li-Hu; Gong, Jyun-An; Li, Yuan-Yao

    2015-01-01

    A field-emission light source with high luminance, excellent luminance uniformity, and tunable luminance characteristics with a novel lateral-gate structure is demonstrated. The lateral-gate triode structure comprises SiC nanowire emitters on a Ag cathode electrode and a pair of Ag gate electrodes placed laterally on both sides of the cathode. The simple and cost-effective screen printing technique is employed to pattern the lateral-gates and cathode structure on soda lime glass. The area coverage of the screen-printed cathode and gates on the glass substrate (area: 6 × 8 cm(2)) is in the range of 2.04% - 4.74% depending on the set of cathode-gate electrodes on the substrate. The lateral-gate structure with its small area coverage exhibits a two-dimensional luminance pattern with high brightness and good luminance uniformity. A maximum luminance of 10,952 cd/cm(2) and a luminance uniformity of >90% can be achieved with a gate voltage of 500 V and an anode voltage of 4000 V, with an anode current of 1.44 mA and current leakage to the gate from the cathode of about 10%. PMID:26042359

  3. Flat Panel Light Source with Lateral Gate Structure Based on SiC Nanowire Field Emitters

    PubMed Central

    Youh, Meng-Jey; Tseng, Chun-Lung; Jhuang, Meng-Han; Chiu, Sheng-Cheng; Huang, Li-Hu; Gong, Jyun-An; Li, Yuan-Yao

    2015-01-01

    A field-emission light source with high luminance, excellent luminance uniformity, and tunable luminance characteristics with a novel lateral-gate structure is demonstrated. The lateral-gate triode structure comprises SiC nanowire emitters on a Ag cathode electrode and a pair of Ag gate electrodes placed laterally on both sides of the cathode. The simple and cost-effective screen printing technique is employed to pattern the lateral-gates and cathode structure on soda lime glass. The area coverage of the screen-printed cathode and gates on the glass substrate (area: 6 × 8 cm2) is in the range of 2.04% – 4.74% depending on the set of cathode-gate electrodes on the substrate. The lateral-gate structure with its small area coverage exhibits a two-dimensional luminance pattern with high brightness and good luminance uniformity. A maximum luminance of 10952 cd/cm2 and a luminance uniformity of >90% can be achieved with a gate voltage of 500 V and an anode voltage of 4000 V, with an anode current of 1.44 mA and current leakage to the gate from the cathode of about 10%. PMID:26042359

  4. Use of nonpolar BaHfO3 gate oxide for field effect on the high mobility BaSnO3

    NASA Astrophysics Data System (ADS)

    Park, Chulkwon; Kim, Useong; Kim, Young Mo; Ju, Chanjong; Char, Kookrin

    2015-03-01

    Recently, BaSnO3 (BSO) has attracted attentions as a transparent conducting oxide and/or a transparent oxide semiconductor due to its novel properties: the excellent oxygen stability even at high temperature and the high electrical mobility at room temperature. We fabricated field effect transistors using La-doped BSO as the semiconducting channel on undoped BSO buffer layers on SrTiO3 substrates. A non-polar perovskite BaHfO3 was used as the gate insulator, and 4% La-doped BSO as the source, the drain, and the gate electrodes grown by pulsed laser deposition. We have measured the optical and the dielectric properties of the epitaxial BaHfO3 gate oxide layer, namely the optical band gap, the dielectric constant, and the breakdown field. Using such BaHfO3 gate oxide, we observed carrier modulation in the active layer by field effect. In this presentation, we will report on the performance of such field effect transistors: the output and the transfer characteristics, the field effect mobility, the Ion/Ioff ratio, and the subthreshold swing.

  5. Organic field-effect transistor nonvolatile memories utilizing sputtered C nanoparticles as nano-floating-gate

    SciTech Connect

    Liu, Jie; Liu, Chang-Hai; She, Xiao-Jian; Sun, Qi-Jun; Gao, Xu; Wang, Sui-Dong

    2014-10-20

    High-performance organic field-effect transistor nonvolatile memories have been achieved using sputtered C nanoparticles as the nano-floating-gate. The sputtered C nano-floating-gate is prepared with low-cost material and simple process, forming uniform and discrete charge trapping sites covered by a smooth and complete polystyrene layer. The devices show large memory window, excellent retention capability, and programming/reading/erasing/reading endurance. The sputtered C nano-floating-gate can effectively trap both holes and electrons, and it is demonstrated to be suitable for not only p-type but also n-type organic field-effect transistor nonvolatile memories.

  6. Electric Properties and Interface Charge Trap Density of Ferroelectric Gate Thin Film Transistor Using (Bi,La)4Ti3O12/Pb(Zr,Ti)O3 Stacked Gate Insulator

    NASA Astrophysics Data System (ADS)

    Van Thanh, Pham; Trinh, Bui Nguyen Quoc; Miyasako, Takaaki; Trong Tue, Phan; Tokumitsu, Eisuke; Shimoda, Tatsuya

    2012-09-01

    We successfully fabricated ferroelectric gate thin film transistors (FGTs) using solution-processed (Bi,La)4Ti3O12 (BLT)/Pb(Zr,Ti)O3 (PZT) stacked films and an indium-tin oxide (ITO) film as ferroelectric gate insulators and an oxide channel, respectively. The typical n-type channel transistors were obtained with the counterclockwise hysteresis loop due to the ferroelectric property of the BLT/PZT stacked gate insulators. These FGTs exhibited good device performance characteristics, such as a high ON/OFF ratio of 106, a large memory window of 1.7-3.1 V, and a large ON current of 0.5-2.5 mA. In order to investigate interface charge trapping for these devices, we applied the conductance method to MFS capacitors, i.e., Pt/ITO/BLT/PZT/Pt capacitors. As a result, the interface charge trap density (Dit) between the ITO and BLT/PZT stacked films was estimated to be in the range of 10-11-10-12 eV-1 cm-2. The small Dit value suggested that good interfaces were achieved.

  7. Electric Properties and Interface Charge Trap Density of Ferroelectric Gate Thin Film Transistor Using (Bi,La)4Ti3O12/Pb(Zr,Ti)O3 Stacked Gate Insulator

    NASA Astrophysics Data System (ADS)

    Thanh, Pham Van; Trinh, Bui Nguyen Quoc; Miyasako, Takaaki; Tue, Phan Trong; Tokumitsu, Eisuke; Shimoda, Tatsuya

    2012-09-01

    We successfully fabricated ferroelectric gate thin film transistors (FGTs) using solution-processed (Bi,La)4Ti3O12 (BLT)/Pb(Zr,Ti)O3 (PZT) stacked films and an indium--tin oxide (ITO) film as ferroelectric gate insulators and an oxide channel, respectively. The typical n-type channel transistors were obtained with the counterclockwise hysteresis loop due to the ferroelectric property of the BLT/PZT stacked gate insulators. These FGTs exhibited good device performance characteristics, such as a high ON/OFF ratio of 106, a large memory window of 1.7--3.1 V, and a large ON current of 0.5--2.5 mA. In order to investigate interface charge trapping for these devices, we applied the conductance method to MFS capacitors, i.e., Pt/ITO/BLT/PZT/Pt capacitors. As a result, the interface charge trap density (Dit) between the ITO and BLT/PZT stacked films was estimated to be in the range of 10-11--10-12 eV-1 cm-2. The small Dit value suggested that good interfaces were achieved.

  8. Liquid crystal-gated-organic field-effect transistors with in-plane drain-source-gate electrode structure.

    PubMed

    Seo, Jooyeok; Nam, Sungho; Jeong, Jaehoon; Lee, Chulyeon; Kim, Hwajeong; Kim, Youngkyoo

    2015-01-14

    We report planar liquid crystal-gated-organic field-effect transistors (LC-g-OFETs) with a simple in-plane drain-source-gate electrode structure, which can be cost-effectively prepared by typical photolithography/etching processes. The LC-g-OFET devices were fabricated by forming the LC layer (4-cyano-4'-pentylbiphenyl, 5CB) on top of the channel layer (poly(3-hexylthiophene), P3HT) that was spin-coated on the patterned indium-tin oxide (ITO)-coated glass substrates. The LC-g-OFET devices showed p-type transistor characteristics, while a current saturation behavior in the output curves was achieved for the 50-150 nm-thick P3HT (channel) layers. A prospective on/off ratio (>1 × 10(3)) was obtained regardless of the P3HT thickness, whereas the resulting hole mobility (0.5-1.1 cm(2)/(V s)) at a linear regime was dependent on the P3HT thickness. The tilted ordering of 5CB at the LC-P3HT interfaces, which is induced by the gate electric field, has been proposed as a core point of working mechanism for the present LC-g-OFETs. PMID:25478816

  9. A carrier-based analytical theory for negative capacitance symmetric double-gate field effect transistors and its simulation verification

    NASA Astrophysics Data System (ADS)

    Jiang, Chunsheng; Liang, Renrong; Wang, Jing; Xu, Jun

    2015-09-01

    A carrier-based analytical drain current model for negative capacitance symmetric double-gate field effect transistors (NC-SDG FETs) is proposed by solving the differential equation of the carrier, the Pao-Sah current formulation, and the Landau-Khalatnikov equation. The carrier equation is derived from Poisson’s equation and the Boltzmann distribution law. According to the model, an amplified semiconductor surface potential and a steeper subthreshold slope could be obtained with suitable thicknesses of the ferroelectric film and insulator layer at room temperature. Results predicted by the analytical model agree well with those of the numerical simulation from a 2D simulator without any fitting parameters. The analytical model is valid for all operation regions and captures the transitions between them without any auxiliary variables or functions. This model can be used to explore the operating mechanisms of NC-SDG FETs and to optimize device performance.

  10. Enhanced CAD model for gate leakage current in heterostructure field effect transistors

    SciTech Connect

    Lee, K.Y. |; Lund, B.; Ytterdal, T.; Robertson, J.; Shur, M.S.; Robertson, P.; Martinez, E.J.

    1996-06-01

    A simple and accurate circuit model for Heterostructure Field Effect Transistors (HFET`s) is proposed to simulate both the gate and the drain current characteristics accounting for hot-electron effects on gate current and the effect of the gate current on the channel current. An analytical equation that describes the effective electron temperature is developed in a simple form. This equation is suitable for implementation in circuit simulators. The model describes both the drain and gate currents at high gate bias voltages. It has been implemented in the circuit simulator AIM-Spice, and good agreement between simulated and measured results is achieved for enhancement-mode HFET`s fabricated in different laboratories. The proposed equivalent circuit and model equations are applicable to other compound semiconductor FET`s, i.e., GaAs MESFET`s.

  11. Gate controlled electronic transport in monolayer MoS{sub 2} field effect transistor

    SciTech Connect

    Zhou, Y. F.; Wang, B.; Yu, Y. J.; Wei, Y. D. E-mail: jianwang@hku.hk; Xian, H. M.; Wang, J. E-mail: jianwang@hku.hk

    2015-03-14

    The electronic spin and valley transport properties of a monolayer MoS{sub 2} are investigated using the non-equilibrium Green's function formalism combined with density functional theory. Due to the presence of strong Rashba spin orbit interaction (RSOI), the electronic valence bands of monolayer MoS{sub 2} are split into spin up and spin down Zeeman-like texture near the two inequivalent vertices K and K′ of the first Brillouin zone. When the gate voltage is applied in the scattering region, an additional strong RSOI is induced which generates an effective magnetic field. As a result, electron spin precession occurs along the effective magnetic field, which is controlled by the gate voltage. This, in turn, causes the oscillation of conductance as a function of the magnitude of the gate voltage and the length of the gate region. This current modulation due to the spin precession shows the essential feature of the long sought Datta-Das field effect transistor (FET). From our results, the oscillation periods for the gate voltage and gate length are found to be approximately 2.2 V and 20.03a{sub B} (a{sub B} is Bohr radius), respectively. These observations can be understood by a simple spin precessing model and indicate that the electron behaviors in monolayer MoS{sub 2} FET are both spin and valley related and can easily be controlled by the gate.

  12. Nonvolatile memory thin-film transistors using biodegradable chicken albumen gate insulator and oxide semiconductor channel on eco-friendly paper substrate.

    PubMed

    Kim, So-Jung; Jeon, Da-Bin; Park, Jung-Ho; Ryu, Min-Ki; Yang, Jong-Heon; Hwang, Chi-Sun; Kim, Gi-Heon; Yoon, Sung-Min

    2015-03-01

    Nonvolatile memory thin-film transistors (TFTs) fabricated on paper substrates were proposed as one of the eco-friendly electronic devices. The gate stack was composed of chicken albumen gate insulator and In-Ga-Zn-O semiconducting channel layers. All the fabrication processes were performed below 120 °C. To improve the process compatibility of the synthethic paper substrate, an Al2O3 thin film was introduced as adhesion and barrier layers by atomic layer deposition. The dielectric properties of biomaterial albumen gate insulator were also enhanced by the preparation of Al2O3 capping layer. The nonvolatile bistabilities were realized by the switching phenomena of residual polarization within the albumen thin film. The fabricated device exhibited a counterclockwise hysteresis with a memory window of 11.8 V, high on/off ratio of approximately 1.1 × 10(6), and high saturation mobility (μsat) of 11.5 cm(2)/(V s). Furthermore, these device characteristics were not markedly degraded even after the delamination and under the bending situration. When the curvature radius was set as 5.3 cm, the ION/IOFF ratio and μsat were obtained to be 5.9 × 10(6) and 7.9 cm(2)/(V s), respectively. PMID:25679117

  13. Optimization of a Solution-Processed SiO2 Gate Insulator by Plasma Treatment for Zinc Oxide Thin Film Transistors.

    PubMed

    Jeong, Yesul; Pearson, Christopher; Kim, Hyun-Gwan; Park, Man-Young; Kim, Hongdoo; Do, Lee-Mi; Petty, Michael C

    2016-01-27

    We report on the optimization of the plasma treatment conditions for a solution-processed silicon dioxide gate insulator for application in zinc oxide thin film transistors (TFTs). The SiO2 layer was formed by spin coating a perhydropolysilazane (PHPS) precursor. This thin film was subsequently thermally annealed, followed by exposure to an oxygen plasma, to form an insulating (leakage current density of ∼10(-7) A/cm(2)) SiO2 layer. Optimized ZnO TFTs (40 W plasma treatment of the gate insulator for 10 s) possessed a carrier mobility of 3.2 cm(2)/(V s), an on/off ratio of ∼10(7), a threshold voltage of -1.3 V, and a subthreshold swing of 0.2 V/decade. In addition, long-term exposure (150 min) of the pre-annealed PHPS to the oxygen plasma enabled the maximum processing temperature to be reduced from 180 to 150 °C. The resulting ZnO TFT exhibited a carrier mobility of 1.3 cm(2)/(V s) and on/off ratio of ∼10(7). PMID:26704352

  14. An insulated gate bipolar transistor with surface n-type barrier

    NASA Astrophysics Data System (ADS)

    Mengxuan, Jiang; John, Shen Z.; Jun, Wang; Zhikang, Shuai; Xin, Yin; Bingbing, Sun; Linyuan, Liao

    2015-12-01

    This letter proposes a novel IGBT structure with an n-type barrier (NB-IGBT) formed on the silicon surface to enhance the conductivity modulation effect with a relatively simple fabrication process. TCAD simulation indicates that the NB-IGBT offers a current density 49% higher and turn-off losses 25% lower than a conventional field-stop IGBT (FS-IGBT) with a similar breakdown voltage, turn-off time and avalanche energy. Furthermore, the NB-IGBT exhibits extremely large transconductance, which is favorable to turn-on and turn-off. Therefore, the proposed IGBT offers an attractive option for high-voltage and large-power electronics applications. Project supported by the National High Technology Research and Development Program of China (No. 2014AA052601) and the National Natural Science Foundation of China (No. 51277060).

  15. High mobility field effect transistor based on BaSnO{sub 3} with Al{sub 2}O{sub 3} gate oxide

    SciTech Connect

    Park, Chulkwon; Kim, Useong; Ju, Chan Jong; Park, Ji Sung; Kim, Young Mo; Char, Kookrin

    2014-11-17

    We fabricated an n-type accumulation-mode field effect transistor based on BaSnO{sub 3} transparent perovskite semiconductor, taking advantage of its high mobility and oxygen stability. We used the conventional metal-insulator-semiconductor structures: (In,Sn){sub 2}O{sub 3} as the source, drain, and gate electrodes, Al{sub 2}O{sub 3} as the gate insulator, and La-doped BaSnO{sub 3} as the semiconducting channel. The Al{sub 2}O{sub 3} gate oxide was deposited by atomic layer deposition technique. At room temperature, we achieved the field effect mobility value of 17.8 cm{sup 2}/Vs and the I{sub on}/I{sub off} ratio value higher than 10{sup 5} for V{sub DS} = 1 V. These values are higher than those previously reported on other perovskite oxides, in spite of the large density of threading dislocations in the BaSnO{sub 3} on SrTiO{sub 3} substrates. However, a relatively large subthreshold swing value was found, which we attribute to the large density of charge traps in the Al{sub 2}O{sub 3} as well as the threading dislocations.

  16. Characterization of the pentacene thin-film transistors with an epoxy resin-based polymeric gate insulator

    NASA Astrophysics Data System (ADS)

    Kim, C. H.; Tondelier, D.; Geffroy, B.; Bonnassieux, Y.; Horowitz, G.

    2012-02-01

    The organic thin-film transistors (OTFTs) incorporating pentacene/SU-8 interface were fabricated and characterized. SU-8, a reliable epoxy-based photoresist, is tested as a potential highly-stable polymeric gate dielectric for OTFTs. The fabricated devices showed promising electrical performance with on-off ratio up to 107 and field-effect mobility up to 0.56 cm2/V s. Several device characteristics are further analyzed. There existed a leakage current path due to the uncontrolled pentacene coverage and we revealed that precise alignment of the evaporation mask of pentacene is critical for eliminating this problem. Pentacene grain formation largely depended on the growth condition on the SU-8 surface and small-grain films offered outstanding performance possibly owing to enhanced inter-domain connections. Natural degradation of the OTFTs is also discussed in terms of environmental stability and the pentacene/SU-8 transistor operated with noticeable air stability under ambient conditions.

  17. Moffett Field Funnel and Gate TCE Treatment System: Interpretation of Field Performance using Reactive Transport Modeling

    SciTech Connect

    Yabusaki, Steven B.; Cantrell, Kirk J.; Sass, B. M.

    2001-06-30

    A multicomponent reactive transport simulator was used to understand the behavior of chemical components, including TCE and cis-1,2-DCE, in groundwater transported through the pilot-scale funnel and gate chemical treatment system at Moffett Field, California. Field observations indicated that zero-valent iron emplaced in the gate to effect the destruction of chlorinated hydrocarbons also resulted in increases in pH and hydrocarbons, as well as decreases in EH, alkalinity, dissolved O2 and CO2, and major ions (i.e., Ca, Mg, Cl, sulfate, nitrate). Of concern are chemical transformations that may reduce the effectiveness or longevity of the iron cell and/or create secondary contaminants. A coupled model of transport and reaction processes was developed to account for mobile and immobile components undergoing equilibrium and kinetic reactions including TCE degradation, parallel iron dissolution reactions, precipitation of secondary minerals, and complexation reactions. The model reproduced solution chemistry observed in the iron cell using reaction parameters from the literature and laboratory studies. Mineral precipitation in the iron zone, which is critical to correctly predicting the aqueous concentrations, was predicted to account for up to 3 percent additional mineral volume annually. Interplay between rates of transport and rates of reaction in the field was key to understanding system behavior.

  18. O3-sourced atomic layer deposition of high quality Al2O3 gate dielectric for normally-off GaN metal-insulator-semiconductor high-electron-mobility transistors

    NASA Astrophysics Data System (ADS)

    Huang, Sen; Liu, Xinyu; Wei, Ke; Liu, Guoguo; Wang, Xinhua; Sun, Bing; Yang, Xuelin; Shen, Bo; Liu, Cheng; Liu, Shenghou; Hua, Mengyuan; Yang, Shu; Chen, Kevin J.

    2015-01-01

    High quality Al2O3 film grown by atomic layer deposition (ALD), with ozone (O3) as oxygen source, is demonstrated for fabrication of normally-off AlGaN/GaN metal-insulator-semiconductor high-electron-mobility transistors (MIS-HEMTs). Significant suppression of Al-O-H and Al-Al bonds in ALD-Al2O3 has been realized by substituting conventional H2O source with O3. A high dielectric breakdown E-field of 8.5 MV/cm and good TDDB behavior are achieved in a gate dielectric stack consisting of 13-nm O3-Al2O3 and 2-nm H2O-Al2O3 interfacial layer on recessed GaN. By using this 15-nm gate dielectric and a high-temperature gate-recess technique, the density of positive bulk/interface charges in normally-off AlGaN/GaN MIS-HEMTs is remarkably suppressed to as low as 0.9 × 1012 cm-2, contributing to the realization of normally-off operation with a high threshold voltage of +1.6 V and a low specific ON-resistance RON,sp of 0.49 mΩ cm2.

  19. Physical Modeling of Gate-Controlled Schottky Barrier Lowering of Metal-Graphene Contacts in Top-Gated Graphene Field-Effect Transistors

    PubMed Central

    Mao, Ling-Feng; Ning, Huansheng; Huo, Zong-Liang; Wang, Jin-Yan

    2015-01-01

    A new physical model of the gate controlled Schottky barrier height (SBH) lowering in top-gated graphene field-effect transistors (GFETs) under saturation bias condition is proposed based on the energy conservation equation with the balance assumption. The theoretical prediction of the SBH lowering agrees well with the experimental data reported in literatures. The reduction of the SBH increases with the increasing of gate voltage and relative dielectric constant of the gate oxide, while it decreases with the increasing of oxide thickness, channel length and acceptor density. The magnitude of the reduction is slightly enhanced under high drain voltage. Moreover, it is found that the gate oxide materials with large relative dielectric constant (>20) have a significant effect on the gate controlled SBH lowering, implying that the energy relaxation of channel electrons should be taken into account for modeling SBH in GFETs. PMID:26674338

  20. Stark shift and field ionization of arsenic donors in {sup 28}Si-silicon-on-insulator structures

    SciTech Connect

    Lo, C. C. Morton, J. J. L.; Simmons, S.; Lo Nardo, R.; Weis, C. D.; Schenkel, T.; Tyryshkin, A. M.; Lyon, S. A.; Meijer, J.; Rogalla, D.; Bokor, J.

    2014-05-12

    We develop an efficient back gate for silicon-on-insulator (SOI) devices operating at cryogenic temperatures and measure the quadratic hyperfine Stark shift parameter of arsenic donors in isotopically purified {sup 28}Si-SOI layers using such structures. The back gate is implemented using MeV ion implantation through the SOI layer forming a metallic electrode in the handle wafer, enabling large and uniform electric fields up to 2 V/μm to be applied across the SOI layer. Utilizing this structure, we measure the Stark shift parameters of arsenic donors embedded in the {sup 28}Si-SOI layer and find a contact hyperfine Stark parameter of η{sub a} = −1.9 ± 0.7 × 10{sup −3} μm{sup 2}/V{sup 2}. We also demonstrate electric-field driven dopant ionization in the SOI device layer, measured by electron spin resonance.

  1. Ultraviolet femtosecond Kerr-gated wide-field fluorescence microscopy.

    PubMed

    Blake, Jolie C; Nieto-Pescador, Jesus; Li, Zhengxin; Gundlach, Lars

    2016-06-01

    A Kerr-gated microscope capable of imaging ultraviolet luminescence with femtosecond time resolution has been developed. The system allows the spatial, spectral, and temporal measurement of UV-emitting samples. The instrumentation was optimized for emission collection in the UV, resulting in sub 90 fs time resolution of gated signals. ZnO nanowires were used to demonstrate the performance of the instrument. The evolution of the emission from a single nanowire was tracked via ultrafast transient spectroscopy and through sequential imaging. Transient dynamics were extracted from a region of intense emission on a single ZnO nanowire. This technique is a powerful tool capable of contactless ultrafast measurements of charge carrier dynamics in single nanoparticles. PMID:27244389

  2. Semi-flexible gas-insulated transmission line using electric field stress shields

    DOEpatents

    Cookson, Alan H.; Dale, Steinar J.; Bolin, Philip C.

    1982-12-28

    A gas-insulated transmission line includes an outer sheath, an inner conductor, an insulating gas electrically insulating the inner conductor from the outer sheath, and insulating supports insulatably supporting the inner conductor within the outer sheath. The inner conductor is provided with flexibility by use of main conductor sections which are joined together through a conductor hub section and flexible flexing elements. Stress shields are provided to control the electric field at the locations of the conductor hub sections where the insulating supports are contacting the inner conductor. The flexing elements and the stress shields may also be utilized in connection with a plug and socket arrangement for providing electrical connection between main conductor sections.

  3. Semi-flexible gas-insulated transmission line using electric field stress shields

    DOEpatents

    Cookson, A.H.; Dale, S.J.; Bolin, P.C.

    1982-12-28

    A gas-insulated transmission line includes an outer sheath, an inner conductor, an insulating gas electrically insulating the inner conductor from the outer sheath, and insulating supports insulatably supporting the inner conductor within the outer sheath. The inner conductor is provided with flexibility by use of main conductor sections which are joined together through a conductor hub section and flexible flexing elements. Stress shields are provided to control the electric field at the locations of the conductor hub sections where the insulating supports are contacting the inner conductor. The flexing elements and the stress shields may also be utilized in connection with a plug and socket arrangement for providing electrical connection between main conductor sections. 10 figs.

  4. Gate-control efficiency and interface state density evaluated from capacitance-frequency-temperature mapping for GaN-based metal-insulator-semiconductor devices

    SciTech Connect

    Shih, Hong-An; Kudo, Masahiro; Suzuki, Toshi-kazu

    2014-11-14

    We present an analysis method for GaN-based metal-insulator-semiconductor (MIS) devices by using capacitance-frequency-temperature (C-f-T) mapping to evaluate the gate-control efficiency and the interface state density, both exhibiting correlations with the linear-region intrinsic transconductance. The effectiveness of the method was exemplified by application to AlN/AlGaN/GaN MIS devices to elucidate the properties of AlN-AlGaN interfaces depending on their formation processes. Using the C-f-T mapping, we extract the gate-bias-dependent activation energy with its derivative giving the gate-control efficiency, from which we evaluate the AlN-AlGaN interface state density through the Lehovec equivalent circuit in the DC limit. It is shown that the gate-control efficiency and the interface state density have correlations with the linear-region intrinsic transconductance, all depending on the interface formation processes. In addition, we give characterization of the AlN-AlGaN interfaces by using X-ray photoelectron spectroscopy, in relation with the results of the analysis.

  5. Flexible gas insulated transmission line having regions of reduced electric field

    DOEpatents

    Cookson, Alan H.; Fischer, William H.; Yoon, Kue H.; Meyer, Jeffry R.

    1983-01-01

    A gas insulated transmission line having radially flexible field control means for reducing the electric field along the periphery of the inner conductor at predetermined locations wherein the support insulators are located. The radially flexible field control means of the invention includes several structural variations of the inner conductor, wherein careful controlling of the length to depth of surface depressions produces regions of reduced electric field. Several embodiments of the invention dispose a flexible connector at the predetermined location along the inner conductor where the surface depressions that control the reduced electric field are located.

  6. Field programmable gate arrays: Evaluation report for space-flight application

    NASA Technical Reports Server (NTRS)

    Sandoe, Mike; Davarpanah, Mike; Soliman, Kamal; Suszko, Steven; Mackey, Susan

    1992-01-01

    Field Programmable Gate Arrays commonly called FPGA's are the newer generation of field programmable devices and offer more flexibility in the logic modules they incorporate and in how they are interconnected. The flexibility, the number of logic building blocks available, and the high gate densities achievable are why users find FPGA's attractive. These attributes are important in reducing product development costs and shortening the development cycle. The aerospace community is interested in incorporating this new generation of field programmable technology in space applications. To this end, a consortium was formed to evaluate the quality, reliability, and radiation performance of FPGA's. This report presents the test results on FPGA parts provided by ACTEL Corporation.

  7. Thermoelectric Properties of Non-Metallic Topological Insulator Bi2 Te 3 at High Magnetic Fields

    NASA Astrophysics Data System (ADS)

    Qu, Dong-Xia; Hor, Yew San; Cava, Robert J.; Ong, N. Phuan; Princeton University Team

    2011-03-01

    Three-dimensional topological insulators are a new class of electronic systems characterized by a bulk insulating state and conducting surface states with Dirac-like energy-momentum dispersion [1, 2]. One of the interesting aspects of this material is how the surface states affect thermoelectric properties of the whole electronic system, given that the bismuth based topological insulators are also excellent thermoelectric materials. We studied the low-temperature thermoelectric transport properties of high-mobility bulk topological insulator Bi 2 Te 3 at high magnetic fields up to 35 T. We found remarkably large quantum oscillations in the thermopower of the surface states over a field range of 14 to 35 T. The existence of a non-zero Berry's phase in surface electrons is confirmed from the magneto-oscillations of both thermopower and magnetoresistance. Supported by NSF-MRSEC under Grant DMR 08-19860.

  8. Phase separation between conductive and insulative materials induced by the electric field.

    PubMed

    Nagamine, Yuko

    2016-07-01

    To demonstrate that phase separation is a main mechanism of pattern formation for one of the spatiotemporal patterns emerging in the Ag and Sb electrodeposition system, I performed numerical simulations to model the mixed system of conductive and insulative materials under a steady electric field. For such a dissipative system, I derived the extended Cahn-Hilliard equation using Onsager's variational principle. My results demonstrate that conductive and insulative materials phase separate spatially under the constant-current mode. PMID:27575064

  9. Phase separation between conductive and insulative materials induced by the electric field

    NASA Astrophysics Data System (ADS)

    Nagamine, Yuko

    2016-07-01

    To demonstrate that phase separation is a main mechanism of pattern formation for one of the spatiotemporal patterns emerging in the Ag and Sb electrodeposition system, I performed numerical simulations to model the mixed system of conductive and insulative materials under a steady electric field. For such a dissipative system, I derived the extended Cahn-Hilliard equation using Onsager's variational principle. My results demonstrate that conductive and insulative materials phase separate spatially under the constant-current mode.

  10. The Dilemma of Field Experience Assessment: Enhancing Professional Development or Fulfilling a Gate-Keeping Function?

    ERIC Educational Resources Information Center

    Cheng, May May-hung; Tang, Sylvia Yee-fan

    2008-01-01

    The field experience component in a teacher education programme serves both a gate-keeping function and a formative purpose that supports student teacher development. The authors were members of a research team which took care of the re-design of the assessment instrument for the field experience component of a teacher education programme, as well…

  11. Modeling of a Metal-Ferroelectric-Semiconductor Field-Effect Transistor NAND Gate

    NASA Technical Reports Server (NTRS)

    Phillips, Thomas A.; MacLeod, Todd C.; Ho, Fat Duen

    2005-01-01

    Considerable research has been performed by several organizations in the use of the Metal- Ferroelectric-Semiconductor Field-Effect Transistors (MFSFET) in memory circuits. However, research has been limited in expanding the use of the MFSFET to other electronic circuits. This research project investigates the modeling of a NAND gate constructed from MFSFETs. The NAND gate is one of the fundamental building blocks of digital electronic circuits. The first step in forming a NAND gate is to develop an inverter circuit. The inverter circuit was modeled similar to a standard CMOS inverter. A n-channel MFSFET with positive polarization was used for the n-channel transistor, and a n-channel MFSFET with negative polarization was used for the p-channel transistor. The MFSFETs were simulated by using a previously developed current model which utilized a partitioned ferroelectric layer. The inverter voltage transfer curve was obtained over a standard input of zero to five volts. Then a 2-input NAND gate was modeled similar to the inverter circuit. Voltage transfer curves were obtained for the NAND gate for various configurations of input voltages. The resultant data shows that it is feasible to construct a NAND gate with MFSFET transistors.

  12. Metal-Ferroelectric-Semiconductor Field-Effect Transistor NAND Gate Switching Time Analysis

    NASA Technical Reports Server (NTRS)

    Phillips, Thomas A.; Macleod, Todd C.; Ho, Fat D.

    2006-01-01

    Previous research investigated the modeling of a N Wga te constructed of Metal-Ferroelectric- Semiconductor Field-Effect Transistors (MFSFETs) to obtain voltage transfer curves. The NAND gate was modeled using n-channel MFSFETs with positive polarization for the standard CMOS n-channel transistors and n-channel MFSFETs with negative polarization for the standard CMOS p-channel transistors. This paper investigates the MFSFET NAND gate switching time propagation delay, which is one of the other important parameters required to characterize the performance of a logic gate. Initially, the switching time of an inverter circuit was analyzed. The low-to-high and high-to-low propagation time delays were calculated. During the low-to-high transition, the negatively polarized transistor pulls up the output voltage, and during the high-to-low transition, the positively polarized transistor pulls down the output voltage. The MFSFETs were simulated by using a previously developed model which utilized a partitioned ferroelectric layer. Then the switching time of a 2-input NAND gate was analyzed similarly to the inverter gate. Extension of this technique to more complicated logic gates using MFSFETs will be studied.

  13. Field Test of Fiber-Optic Voltage and Current Sensors Applied to Gas Insulated Substation

    NASA Astrophysics Data System (ADS)

    Kuroda, Y.; Abe, Y.; Kuwahara, H.; Yoshinaga, K.

    1986-08-01

    The fiber-optic voltage and current sensors applied for 84kV three phase type gas insulated substation (GIS) were tested in order to see the advantages of these sensors practically in adverse field condition. The application technologies and field endurance test results of the sensors are described in this paper.

  14. Modulation of Superconductor-Insulator Transition in NdBa2Cu3O7-x through Oxygen Migration by Electrolyte Gating

    NASA Astrophysics Data System (ADS)

    Zhang, Lingchao; Zeng, S. W.; Wan, D. Y.; Han, K.; Jian, L. K.; Ariando, A.; Venkatesan, T.; Nusnni-Nanocore Team

    The technique of electric double layer transistor (EDLT) has been applied to several HTS, such as LSCO and YBCO. The interpretation of SIT in all these studies are attributed to electrostatically induced carriers. However, in several electrolyte gating experiments recently, the effect is mainly attributed to oxygen vacancy formation, with migration of oxygen from the film into ionic liquid. In this study, the modulation of SIT is performed in a 7uc NBCO EDLT. By applying positive Vg, the SC NBCO gradually transits to insulating. When Vg changes back to 0V, it remains insulating. If the mechanism is electrostatically induced carriers, it should recover SC. However, it is only when applying a reverse negative Vg that it can gradually recover SC. Meanwhile, after SIT and Vg back to 0V, another sample is taken out from PPMS. After careful remove of ionic liquid, it remains insulating. After annealing at O2 atmosphere, it recovers SC. These strongly support the underlying mechanism is oxygen migration, instead of electrostatically induced carriers. The Rc is extracted to be about 5320 Ω, suggestive of quantum phase fluctuation.

  15. Electrically configurable graphene field-effect transistors with a graded-potential gate.

    PubMed

    Wang, Xiaowei; Jiang, Xingbin; Wang, Ting; Shi, Jia; Liu, Mingju; Zeng, Qibin; Cheng, Zhihai; Qiu, Xiaohui

    2015-05-13

    A device architecture for electrically configurable graphene field-effect transistor (GFET) using a graded-potential gate is present. The gating scheme enables a linearly varying electric field that modulates the electronic structure of graphene and causes a continuous shift of the Dirac points along the channel of GFET. This spatially varying electrostatic modulation produces a pseudobandgap observed as a suppressed conductance of graphene within a controllable energy range. By tuning the electrical gradient of the gate, a GFET device is reversibly transformed between ambipolar and n- and p-type unipolar characteristics. We further demonstrate an electrically programmable complementary inverter, showing the extensibility of the proposed architecture in constructing logic devices based on graphene and other Dirac materials. The electrical configurable GFET might be explored for novel functionalities in smart electronics. PMID:25897889

  16. A hydrogel capsule as gate dielectric in flexible organic field-effect transistors

    SciTech Connect

    Dumitru, L. M.; Manoli, K.; Magliulo, M.; Torsi, L.; Ligonzo, T.; Palazzo, G.

    2015-01-01

    A jellified alginate based capsule serves as biocompatible and biodegradable electrolyte system to gate an organic field-effect transistor fabricated on a flexible substrate. Such a system allows operating thiophene based polymer transistors below 0.5 V through an electrical double layer formed across an ion-permeable polymeric electrolyte. Moreover, biological macro-molecules such as glucose-oxidase and streptavidin can enter into the gating capsules that serve also as delivery system. An enzymatic bio-reaction is shown to take place in the capsule and preliminary results on the measurement of the electronic responses promise for low-cost, low-power, flexible electronic bio-sensing applications using capsule-gated organic field-effect transistors.

  17. Sub-10 nm transparent all-around-gated ambipolar ionic field effect transistor.

    PubMed

    Lee, Seung-Hyun; Lee, Hyomin; Jin, Tianguang; Park, Sungmin; Yoon, Byung Jun; Sung, Gun Yong; Kim, Ki-Bum; Kim, Sung Jae

    2015-01-21

    In this paper, we developed a versatile ionic field effect transistor (IFET) which has an ambipolar function for manipulating molecules regardless of their polarity and can be operated at a wide range of electrolytic concentrations (10(-5) M-1 M). The IFET has circular nanochannels radially covered by gate electrodes, called "all-around-gate", with an aluminum oxide (Al2O3) oxide layer of a near-zero surface charge. Experimental and numerical validations were conducted for characterizing the IFET. We found that the versatility originated from the zero-charge density of the oxide layer and all-around-gate structure which increased the efficiency of the gate effect 5 times higher than a previously developed planar-gate by capacitance calculations. Our numerical model adapted Poisson-Nernst-Planck-Stokes (PNPS) formulations with additional nonlinear constraints of a fringing field effect and a counter-ion condensation and the experimental and numerical results were well matched. The device can control the transportation of ions at concentrations up to 1 M electrolyte which resembles a backflow of a shale gas extraction process. Furthermore, while traditional IFETs can manipulate either positively or negatively charged species depending on the inherently large surface charge of oxide layer, the presenting device and mechanism provide effective means to control the motion of both negatively and positively charged molecules which is important in biomolecule transport through nanochannels, medical diagnosis system and point-of-care system, etc. PMID:25363392

  18. Utilizing self-assembled-monolayer-based gate dielectrics to fabricate molybdenum disulfide field-effect transistors

    NASA Astrophysics Data System (ADS)

    Kawanago, Takamasa; Oda, Shunri

    2016-01-01

    In this study, we apply self-assembled-monolayer (SAM)-based gate dielectrics to the fabrication of molybdenum disulfide (MoS2) field-effect transistors. A simple fabrication process involving the selective formation of a SAM on metal oxides in conjunction with the dry transfer of MoS2 flakes was established. A subthreshold slope (SS) of 69 mV/dec and no hysteresis were demonstrated with the ultrathin SAM-based gate dielectrics accompanied by a low gate leakage current. The small SS and no hysteresis indicate the superior interfacial properties of the MoS2/SAM structure. Cross-sectional transmission electron microscopy revealed a sharp and abrupt interface of the MoS2/SAM structure. The SAM-based gate dielectrics are found to be applicable to the fabrication of low-voltage MoS2 field-effect transistors and can also be extended to various layered semiconductor materials. This study opens up intriguing possibilities of SAM-based gate dielectrics in functional electronic devices.

  19. Gate dielectric surface treatments for performance improvement of poly(3-hexylthiophene-2,5-diyl) based organic field-effect transistors

    NASA Astrophysics Data System (ADS)

    Nawaz, Ali; de, Cristiane, , Col; Cruz-Cruz, Isidro; Kumar, Anshu; Kumar, Anil; Hümmelgen, Ivo A.

    2015-08-01

    We report on enhanced performance in poly(3-hexylthiophene-2,5-diyl) (P3HT) based organic field effect transistors (OFETs) achieved by improvement in hole transport along the channel near the insulator/semiconductor (I/S) interface. The improvement in hole transport is demonstrated to occur very close to the I/S interface, after treatment of the insulator layer with sodium dodecyl sulfate (SDS). SDS is an anionic surfactant, with negatively charged heads, known for formation of micelles above critical micelle concentration (CMC), which contribute to the passivation of positively charged traps. Investigation of field-effect mobility (μFET) as a function of channel bottleneck thickness in OFETs reveals the favorable gate voltage regime where mobility is the highest. In addition, it shows that the gate dielectric surface treatment not only leads to an increase in mobility in that regime, but also displaces charge transport closer to the interface, hence pointing toward passivation of the charge traps at I/S interface. OFETs with SDS treatment were compared with untreated and vitamin C or hexadecyltrimethylammonium bromide (CTAB) treated OFETs. All the treatments resulted in significant improvements in specific dielectric capacitance, μFET, on/off current ratio and transconductance.

  20. Field-Effect Birefringent Spin Lens in Ultrathin Film of Magnetically Doped Topological Insulators

    NASA Astrophysics Data System (ADS)

    Tang, Peizhe; Zhao, Lu; Gu, Bing-Lin; Duan, Wenhui

    2014-03-01

    We investigate the low-energy electron dynamics in two-dimensional ultrathin film of magnetically doped topological insulators in the context of gate-tuned coherent spin manipulation. Our first-principles calculations for such film unambiguously identify its spin-resolved topological band structure arising from spin-orbit coupling and time-reversal symmetry breaking. Exploiting this characteristic, we predict a negative birefraction for chiral electron tunneling through a gate-controlled p-n interface in the film, analogous to optical birefringence. By fine-tuning the gate voltage, a series of unusual phenomena, including electron double focusing, spatial modulation of spin polarizations, and quantum-interferenceinduced beating patterns, could be efficiently implemented, offering a powerful platform to establish spin-resolved electron optics by all-electrical means. L. Z. and P. T. contributed equally to this work. We acknowledge support from the National Natural Science Foundation of China (Grants No. 11204154 and No. 11074139) and the Ministry of Science and Technology of China (Grants No. 2011CB606405 and No. 2011CB921901).

  1. Thermal Performance of Cryogenic Piping Multilayer Insulation in Actual Field Installations

    NASA Technical Reports Server (NTRS)

    Fesmire, J.; Augustnynowicz, S.; Thompson, K. (Technical Monitor)

    2002-01-01

    A standardized way of comparing the thermal performance of different pipelines in different sizes is needed. Vendor data for vacuum-insulated piping are typically given in heat leak rate per unit length (W/m) for a specific diameter pipeline. An overall k-value for actual field installations (k(sub oafi)) is therefore proposed as a more generalized measure for thermal performance comparison and design calculation. The k(sub oafi) provides a direct correspondence to the k-values reported for insulation materials and illustrates the large difference between ideal multilayer insulation (MLI) and actual MLI performance. In this experimental research study, a section of insulated piping was tested under cryogenic vacuum conditions, including simulated spacers and bending. Several different insulation systems were tested using a 1-meter-long cylindrical cryostat test apparatus. The simulated spacers tests showed significant degradation in the thermal performance of a given insulation system. An 18-meter-long pipeline test apparatus is now in operation at the Cryogenics Test Laboratory, NASA Kennedy Space Center, for conducting liquid nitrogen thermal performance tests.

  2. Influence of the charge trap density distribution in a gate insulator on the positive-bias stress instability of amorphous indium-gallium-zinc oxide thin-film transistors

    NASA Astrophysics Data System (ADS)

    Kim, Eungtaek; Kim, Choong-Ki; Lee, Myung Keun; Bang, Tewook; Choi, Yang-Kyu; Park, Sang-Hee Ko; Choi, Kyung Cheol

    2016-05-01

    We investigated the positive-bias stress (PBS) instability of thin film transistors (TFTs) composed of different types of first-gate insulators, which serve as a protection layer of the active surface. Two different deposition methods, i.e., the thermal atomic layer deposition (THALD) and plasma-enhanced ALD (PEALD) of Al2O3, were applied for the deposition of the first GI. When THALD was used to deposit the GI, amorphous indium-gallium-zinc oxide (a-IGZO) TFTs showed superior stability characteristics under PBS. For example, the threshold voltage shift (ΔVth) was 0 V even after a PBS time (tstress) of 3000 s under a gate voltage (VG) condition of 5 V (with an electrical field of 1.25 MV/cm). On the other hand, when the first GI was deposited by PEALD, the ΔVth value of a-IGZO TFTs was 0.82 V after undergoing an identical amount of PBS. In order to interpret the disparate ΔVth values resulting from PBS quantitatively, the average oxide charge trap density (NT) in the GI and its spatial distribution were investigated through low-frequency noise characterizations. A higher NT resulted during in the PEALD type GI than in the THALD case. Specifically, the PEALD process on a-IGZO layer surface led to an increasing trend of NT near the GI/a-IGZO interface compared to bulk GI owing to oxygen plasma damage on the a-IGZO surface.

  3. Magneto-transport properties of the ternary topological insulator (Bi0.5Sb0.5)2 Te3 in the presence of electrostatic gating and magnetic impurity

    NASA Astrophysics Data System (ADS)

    Yu, Liuqi; Barreda, Jorge; Hu, Longqian; Xiong, P.; Guan, Tong; He, Xiaoyue; Wu, K.; Li, Y.

    2013-03-01

    A three-dimensional topological insulator, (Bi0.5Sb0.5)2 Te3, is used to characterize the electronic properties of the spin helical conducting surface state. Epitaxial films are grown via MBE on (111) SrTiO3 substrate, which serves as the gate dielectric. Magnetoresistance (MR) and Hall effect measurements have been performed at various back gate voltages. Ambipolar field effect has been observed, enabling effective tuning of the Fermi level across the band gap. Weak antilocalization effect is identified and used to differentiate the surface state. The Hikami-Larkin-Nagaoka (HLN) equation is used to analyze the MR data and the results show the top and bottom surfaces become decoupled when the Fermi level is in the bulk band gap. We also examine the effects of paramagnetic impurity (MI), which introduces time reversal symmetry breaking scattering, on the TI surface states. Taking advantage of the unique capability of in situ deposition in a customized dilution refrigerator, paramagnetic Cr atoms were incrementally quench-condensed onto the sample surface and transport measurements were performed at each MI density. The procedure eliminates any sample-to-sample variation and complications from air exposure. Pronounced changes in the weak antilocalization effect and the sample carrier density with increasing MI concentration were observed. Possible origins of these observations will be discussed.

  4. An Undergraduate Course and Laboratory in Digital Signal Processing with Field Programmable Gate Arrays

    ERIC Educational Resources Information Center

    Meyer-Base, U.; Vera, A.; Meyer-Base, A.; Pattichis, M. S.; Perry, R. J.

    2010-01-01

    In this paper, an innovative educational approach to introducing undergraduates to both digital signal processing (DSP) and field programmable gate array (FPGA)-based design in a one-semester course and laboratory is described. While both DSP and FPGA-based courses are currently present in different curricula, this integrated approach reduces the…

  5. Systems and methods for detecting a failure event in a field programmable gate array

    NASA Technical Reports Server (NTRS)

    Ng, Tak-Kwong (Inventor); Herath, Jeffrey A. (Inventor)

    2009-01-01

    An embodiment generally relates to a method of self-detecting an error in a field programmable gate array (FPGA). The method includes writing a signature value into a signature memory in the FPGA and determining a conclusion of a configuration refresh operation in the FPGA. The method also includes reading an outcome value from the signature memory.

  6. Vertical Ge and GeSn heterojunction gate-all-around tunneling field effect transistors

    NASA Astrophysics Data System (ADS)

    Schulze, Jörg; Blech, Andreas; Datta, Arnab; Fischer, Inga A.; Hähnel, Daniel; Naasz, Sandra; Rolseth, Erlend; Tropper, Eva-Maria

    2015-08-01

    We present experimental results on the fabrication and characterization of vertical Ge and GeSn heterojunction Tunneling Field Effect Transistors (TFETs). A gate-all-around process with mesa diameters down to 70 nm is used to reduce leakage currents and improve electrostatic control of the gate over the transistor channel. An ION = 88.4 μA/μm at VDS = VG = -2 V is obtained for a TFET with a 10 nm Ge0.92Sn0.08 layer at the source/channel junction. We discuss further possibilities for device improvements.

  7. Simulation of electrical characteristics in negative capacitance surrounding-gate ferroelectric field-effect transistors

    NASA Astrophysics Data System (ADS)

    Xiao, Y. G.; Chen, Z. J.; Tang, M. H.; Tang, Z. H.; Yan, S. A.; Li, J. C.; Gu, X. C.; Zhou, Y. C.; Ouyang, X. P.

    2012-12-01

    The electrical characteristics of surrounding-gate (SG) metal-ferroelectric-semiconductor (MFS) field-effect transistors (FETs) were theoretically investigated by considering the ferroelectric negative capacitance (NC) effect. The derived results demonstrated that the NC-SG-MFS-FET displays superior electrical properties compared with that of the traditional SG-MIS-FET, in terms of better electrostatic control of the gate electrode over the channel, smaller subthreshold swing (S < 60 mV/dec), and bigger value of ION. It is expected that this investigation may provide some insight into the design and performance improvement for the fast switching and low power dissipation applications of ferroelectric FETs.

  8. Extended-gate organic field-effect transistor for the detection of histamine in water

    NASA Astrophysics Data System (ADS)

    Minamiki, Tsukuru; Minami, Tsuyoshi; Yokoyama, Daisuke; Fukuda, Kenjiro; Kumaki, Daisuke; Tokito, Shizuo

    2015-04-01

    As part of our ongoing research program to develop health care sensors based on organic field-effect transistor (OFET) devices, we have attempted to detect histamine using an extended-gate OFET. Histamine is found in spoiled or decayed fish, and causes foodborne illness known as scombroid food poisoning. The new OFET device possesses an extended gate functionalized by carboxyalkanethiol that can interact with histamine. As a result, we have succeeded in detecting histamine in water through a shift in OFET threshold voltage. This result indicates the potential utility of the designed OFET devices in food freshness sensing.

  9. Organic field-effect transistor nonvolatile memories based on hybrid nano-floating-gate

    NASA Astrophysics Data System (ADS)

    Gao, Xu; She, Xiao-Jian; Liu, Chang-Hai; Sun, Qi-Jun; Liu, Jie; Wang, Sui-Dong

    2013-01-01

    High performance organic field-effect transistor nonvolatile memory is achieved by integrating gold nanoparticles and graphene oxide sheets as the hybrid nano-floating-gate. The device shows a large memory window of about 40 V, high ON/OFF ratio of reading current over 104, excellent programming/erasing endurance, and retention ability. The hybrid nano-floating-gate can increase the density of charge trapping sites, which are electrically separate from each other and thus suppress the stored charge leakage. The memory window is increased under illumination, and the results indicate that the photon-generated carriers facilitate the electron trapping but have almost no effect on the hole trapping.

  10. Control of Threshold Voltage for Top-Gated Ambipolar Field-Effect Transistor by Gate Buffer Layer.

    PubMed

    Khim, Dongyoon; Shin, Eul-Yong; Xu, Yong; Park, Won-Tae; Jin, Sung-Ho; Noh, Yong-Young

    2016-07-13

    The threshold voltage and onset voltage for p-channel and n-channel regimes of solution-processed ambipolar organic transistors with top-gate/bottom-contact (TG/BC) geometry were effectively tuned by gate buffer layers in between the gate electrode and the dielectric. The work function of a pristine Al gate electrode (-4.1 eV) was modified by cesium carbonate and vanadium oxide to -2.1 and -5.1 eV, respectively, which could control the flat-band voltage, leading to a remarkable shift of transfer curves in both negative and positive gate voltage directions without any side effects. One important feature is that the mobility of transistors is not very sensitive to the gate buffer layer. This method is simple but useful for electronic devices where the threshold voltage should be precisely controlled, such as ambipolar circuits, memory devices, and light-emitting device applications. PMID:27323003

  11. Ferroelectric/Dielectric Double Gate Insulator Spin-Coated Using Barium Titanate Nanocrystals for an Indium Oxide Nanocrystal-Based Thin-Film Transistor.

    PubMed

    Pham, Hien Thu; Yang, Jin Ho; Lee, Don-Sung; Lee, Byoung Hun; Jeong, Hyun-Dam

    2016-03-23

    Barium titanate nanocrystals (BT NCs) were prepared under solvothermal conditions at 200 °C for 24 h. The shape of the BT NCs was tuned from nanodot to nanocube upon changing the polarity of the alcohol solvent, varying the nanosize in the range of 14-22 nm. Oleic acid-passivated NCs showed good solubility in a nonpolar solvent. The effect of size and shape of the BT NCs on the ferroelectric properties was also studied. The maximum polarization value of 7.2 μC/cm(2) was obtained for the BT-5 NC thin film. Dielectric measurements of the films showed comparable dielectric constant values of BT NCs over 1-100 kHz without significant loss. Furthermore, the bottom gate In2O3 NC thin film transistors exhibited outstanding device performance with a field-effect mobility of 11.1 cm(2) V(-1) s(-1) at a low applied gate voltage with BT-5 NC/SiO2 as the gate dielectric. The low-density trapped state was observed at the interface between the In2O3 NC semiconductor and the BT-5 NCs/SiO2 dielectric film. Furthermore, compensation of the applied gate field by an electric dipole-induced dipole field within the BT-5 NC film was also observed. PMID:26927618

  12. High photosensitivity few-layered MoSe2 back-gated field-effect phototransistors

    NASA Astrophysics Data System (ADS)

    Abderrahmane, A.; Ko, P. J.; Thu, T. V.; Ishizawa, S.; Takamura, T.; Sandhu, A.

    2014-09-01

    In this paper, we report on the fabrication and optoelectronic properties of high sensitive phototransistors based on few-layered MoSe2 back-gated field-effect transistors, with a mobility of 19.7 cm2 V-1 s-1 at room temperature. We obtained an ultrahigh photoresponsivity of 97.1 AW-1 and an external quantum efficiency (EQE) of 22 666% using 532 nm laser excitation at room temperature. The photoresponsivity was improved near the threshold gate voltage; however, the selection of the silicon dioxide as a gate oxide represents a limiting factor in the ultimate performance. Thanks to their high photoresponsivity and external quantum efficiency, the few-layered MoSe2-based devices are promising for photoelectronic applications.

  13. Design Architecture of field-effect transistor with back gate electrode for biosensor application

    NASA Astrophysics Data System (ADS)

    Fathil, M. F. M.; Arshad, M. K. Md.; Hashim, U.; Ruslinda, A. R.; Gopinath, Subash C. B.; M. Nuzaihan M., N.; Ayub, R. M.; Adzhri, R.; Zaki, M.; Azman, A. H.

    2016-07-01

    This paper presents the preparation method of photolithography chrome mask design used in fabrication process of field-effect transistor with back gate biasing based biosensor. Initially, the chrome masks are designed by studying the process flow of the biosensor fabrication, followed by drawing of the actual chrome mask using the AutoCAD software. The overall width and length of the device is optimized at 16 mm and 16 mm, respectively. Fabrication processes of the biosensor required five chrome masks, which included source and drain formation mask, the back gate area formation mask, electrode formation mask, front gate area formation mask, and passivation area formation mask. The complete chrome masks design will be sent for chrome mask fabrication and for future use in biosensor fabrication.

  14. Organic Gate Silicon Field Effect Transistors with Poly Methylmethacrylate Films for Science Education

    NASA Astrophysics Data System (ADS)

    Hirose, Fumihiko; Miyagi, Tatsuro; Narita, Yuzuru

    We have developed an easy fabrication method of Si field effect transistors (FETs) with poly (methyl methacrylate) (PMMA) gate films for science education. In this process, we can easily fabricate the silicon FETs only by means of metal deposition and thermal diffusion without any lithography processes. The organic isolation films of PMMA can be deposited by casting or painting at room temperature in air. The metal-organic-semiconductor FETs with PMMA exhibited almost the same drain current — gate voltage characteristics as those of conventional Si metal-oxide-semiconductor FETs, which are suitable for the education material of semiconductor engineering. The organic gate Si FETs can be used not only for education but also as thin film transistors for active matrix displays.

  15. Measurement and Analysis of a Ferroelectric Field-Effect Transistor NAND Gate

    NASA Technical Reports Server (NTRS)

    Phillips, Thomas A.; MacLeond, Todd C.; Sayyah, Rana; Ho, Fat Duen

    2009-01-01

    Previous research investigated expanding the use of Ferroelectric Field-Effect Transistors (FFET) to other electronic devices beyond memory circuits. Ferroelectric based transistors possess unique characteris tics that give them interesting and useful properties in digital logic circuits. The NAND gate was chosen for investigation as it is one of the fundamental building blocks of digital electronic circuits. In t his paper, NAND gate circuits were constructed utilizing individual F FETs. N-channel FFETs with positive polarization were used for the standard CMOS NAND gate n-channel transistors and n-channel FFETs with n egative polarization were used for the standard CMOS NAND gate p-chan nel transistors. The voltage transfer curves were obtained for the NA ND gate. Comparisons were made between the actual device data and the previous modeled data. These results are compared to standard MOS logic circuits. The circuits analyzed are not intended to be fully opera tional circuits that would interface with existing logic circuits, bu t as a research tool to look into the possibility of using ferroelectric transistors in future logic circuits. Possible applications for th ese devices are presented, and their potential benefits and drawbacks are discussed.

  16. A CMOS-MEMS arrayed resonant-gate field effect transistor (RGFET) oscillator

    NASA Astrophysics Data System (ADS)

    Chin, Chi-Hang; Li, Ming-Huang; Chen, Chao-Yu; Wang, Yu-Lin; Li, Sheng-Shian

    2015-11-01

    A high-frequency CMOS-MEMS arrayed resonant-gate field effect transistor (RGFET) fabricated by a standard 0.35 μm 2-poly-4-metal CMOS-MEMS platform is implemented to enable a Pierce-type oscillator. The proposed arrayed RGFET exhibits low motional impedance of only 5 kΩ under a purely capacitive transduction and decent power handling capability. With such features, the implemented oscillator shows impressive phase noise of  -117 dBc Hz-1 at the far-from-carrier offset (1 MHz). In this work, we design a clamped-clamped beam (CCB) arrayed resonator utilizing a high-velocity mechanical coupling scheme to serve as the resonant-gate array. To achieve a functional arrayed RGFET, a corresponding FET array is directly placed underneath the resonant gate array to convert the motional current on the resonant-gate array into a voltage output with a tunable transconductance gain. To understand the behavior of the proposed device, an equivalent circuit model consisting of the resonant unit and FET is also provided. To verify the effects of the post-CMOS process on device performance, a conventional MOS I D current measurement is carried out. Finally, a CMOS-MEMS arrayed RGFET oscillator is realized by utilizing a Pierce oscillator architecture, showing decent phase noise performance that benefits from the array design to alleviate the nonlinear effect of the resonant gate.

  17. Graphene field-effect transistor array with integrated electrolytic gates scaled to 200 mm

    NASA Astrophysics Data System (ADS)

    Vieira, N. C. S.; Borme, J.; Machado, G., Jr.; Cerqueira, F.; Freitas, P. P.; Zucolotto, V.; Peres, N. M. R.; Alpuim, P.

    2016-03-01

    Ten years have passed since the beginning of graphene research. In this period we have witnessed breakthroughs both in fundamental and applied research. However, the development of graphene devices for mass production has not yet reached the same level of progress. The architecture of graphene field-effect transistors (FET) has not significantly changed, and the integration of devices at the wafer scale has generally not been sought. Currently, whenever an electrolyte-gated FET (EGFET) is used, an external, cumbersome, out-of-plane gate electrode is required. Here, an alternative architecture for graphene EGFET is presented. In this architecture, source, drain, and gate are in the same plane, eliminating the need for an external gate electrode and the use of an additional reservoir to confine the electrolyte inside the transistor active zone. This planar structure with an integrated gate allows for wafer-scale fabrication of high-performance graphene EGFETs, with carrier mobility up to 1800 cm2 V-1 s-1. As a proof-of principle, a chemical sensor was achieved. It is shown that the sensor can discriminate between saline solutions of different concentrations. The proposed architecture will facilitate the mass production of graphene sensors, materializing the potential of previous achievements in fundamental and applied graphene research.

  18. O{sub 3}-sourced atomic layer deposition of high quality Al{sub 2}O{sub 3} gate dielectric for normally-off GaN metal-insulator-semiconductor high-electron-mobility transistors

    SciTech Connect

    Huang, Sen; Liu, Xinyu Wei, Ke; Liu, Guoguo; Wang, Xinhua; Sun, Bing; Yang, Xuelin; Shen, Bo; Liu, Cheng; Liu, Shenghou; Hua, Mengyuan; Yang, Shu; Chen, Kevin J.

    2015-01-19

    High quality Al{sub 2}O{sub 3} film grown by atomic layer deposition (ALD), with ozone (O{sub 3}) as oxygen source, is demonstrated for fabrication of normally-off AlGaN/GaN metal-insulator-semiconductor high-electron-mobility transistors (MIS-HEMTs). Significant suppression of Al–O–H and Al–Al bonds in ALD-Al{sub 2}O{sub 3} has been realized by substituting conventional H{sub 2}O source with O{sub 3}. A high dielectric breakdown E-field of 8.5 MV/cm and good TDDB behavior are achieved in a gate dielectric stack consisting of 13-nm O{sub 3}-Al{sub 2}O{sub 3} and 2-nm H{sub 2}O-Al{sub 2}O{sub 3} interfacial layer on recessed GaN. By using this 15-nm gate dielectric and a high-temperature gate-recess technique, the density of positive bulk/interface charges in normally-off AlGaN/GaN MIS-HEMTs is remarkably suppressed to as low as 0.9 × 10{sup 12 }cm{sup −2}, contributing to the realization of normally-off operation with a high threshold voltage of +1.6 V and a low specific ON-resistance R{sub ON,sp} of 0.49 mΩ cm{sup 2}.

  19. A compact, short-pulse laser for near-field, range-gated imaging

    SciTech Connect

    Zutavern, F.J.; Helgeson, W.D.; Loubriel, G.M.; Yates, G.J.; Gallegos, R.A.; McDonald, T.E.

    1996-12-31

    This paper describes a compact laser, which produces high power, wide-angle emission for a near-field, range-gated, imaging system. The optical pulses are produced by a 100 element laser diode array (LDA) which is pulsed with a GaAs, photoconductive semiconductor switch (PCSS). The LDA generates 100 ps long, gain-switched, optical pulses at 904 nm when it is driven with 3 ns, 400 A, electrical pulses from a high gain PCSS. Gain switching is facilitated with this many lasers by using a low impedance circuit to drive an array of lasers, which are connected electrically in series. The total optical energy produced per pulse is 10 microjoules corresponding to a total peak power of 100 kW. The entire laser system, including prime power (a nine volt battery), pulse charging, PCSS, and LDA, is the size of a small, hand-held flashlight. System lifetime, which is presently limited by the high gain PCSS, is an active area of research and development. Present limitations and potential improvements will be discussed. The complete range-gated imaging system is based on complementary technologies: high speed optical gating with intensified charge coupled devices (ICCD) developed at Los Alamos National Laboratory (LANL) and high gain, PCSS-driven LDAs developed at Sandia National Laboratories (SNL). The system is designed for use in highly scattering media such as turbid water or extremely dense fog or smoke. The short optical pulses from the laser and high speed gating of the ICCD are synchronized to eliminate the back-scattered light from outside the depth of the field of view (FOV) which may be as short as a few centimeters. A high speed photodiode can be used to trigger the intensifier gate and set the range-gated FOV precisely on the target. The ICCD and other aspects of the imaging system are discussed in a separate paper.

  20. Investigation of 4H-SiC insulated-gate bipolar transistor turn-off performance for achieving low power loss

    NASA Astrophysics Data System (ADS)

    Navarro, Dondee; Pesic, Iliya; Morikawa, Yoji; Furui, Yoshiharu; Miura-Mattausch, Mitiko

    2016-04-01

    The dynamic characteristics of a 4H-SiC insulated-gate bipolar transistor (IGBT) at pulse switching is investigated by incorporating reported measurements of the interface defect density to device simulation. Different trap features such as energy states and trap time constants are investigated to determine the influence of traps on circuit performance. The capture cross-section parameter used in the simulation depicts the probability of traps to trap/detrap carriers which relates to the carrier trap time constant. It is demonstrated that trapped carriers from the on-state condition cause enhanced generation current during the off-state condition, which give rise to undesired leakage current in addition to the threshold voltage shift previously reported. The device power dissipation is increased by a factor of 100 due to the defects.

  1. Electric Field-Induced Skyrmion Crystals via Charged Monopoles in Insulating Helimagets

    NASA Astrophysics Data System (ADS)

    Watanabe, Haruki; Vishwanath, Ashvin

    2016-06-01

    Electrons propagating in a magnetically ordered medium experience an additional gauge field associated with the Berry phase of their spin following the local magnetic texture. In contrast to the usual electromagnetic field, this gauge field admits monopole excitations, corresponding to hedgehog defects of the magnetic order. In an insulator, these hedgehogs carry a well-defined electric charge allowing for them to be controlled by electric fields. One particularly robust mechanism that contributes to the charge is the orbital magnetoelectric effect, captured by a θ angle, which leads to a charge of eθ/2π on hedgehogs. This is a direct consequence of the Witten effect for magnetic monopoles in a θ medium. A physical consequence is that external electric fields can induce skyrmion crystal phases in insulating helimagnets.

  2. Supplement analysis for Greenville Gate access to Kirschbaum Field at Lawrence Livermore National Laboratory

    SciTech Connect

    1997-12-05

    The National Ignition Facility (NIF) Program proposes to provide additional access to the Kirschbaum Field construction laydown area. This additional access would alleviate traffic congestion at the East Gate entrance to Lawrence Livermore National Laboratory (LLNL) from Greenville Road during periods of heavy construction for the NIF. The new access would be located along the northeastern boundary of LLNL, about 305 m (1,000 ft) north of the East Gate entrance. The access road would extend from Greenville Road to the Kirschbaum Field construction laydown area and would traverse an existing storm water drainage channel. Two culverts, side by side, and a compacted road base would be installed across the channel. The security fence that runs parallel to Greenville Road would be modified to accommodate this new entrance and a vehicle gate would be installed at the entrance of Kirschbaum Field. The exiting shoulder along Greenville Road would be converted into a new turn lane for trucks entering the new gate. This analysis evaluates the impacts of constructing the Kirschbaum Field bridge and access gate at a different location than was analyzed in the NIF Project specific Analysis in the Final Programmatic environmental Impact Statement for Stockpile Stewardship and Management (SS and M PEIS) published in September 1996 (DOE/EIS-0236) and the Record of Decision published on December 19, 1996. Issues of concern addressed in this supplement analysis include potential impacts to wetlands downstream of the access bridge, potential impacts to the California red-legged frog (Rana aurora draytonii) listed as threatened on the federal listing pursuant to the Endangered Species Act of 1974, and potential impacts on the 100-yr floodplain along the Arroyo Las Positas.

  3. A 2-D semi-analytical model of double-gate tunnel field-effect transistor

    NASA Astrophysics Data System (ADS)

    Huifang, Xu; Yuehua, Dai; Ning, Li; Jianbin, Xu

    2015-05-01

    A 2-D semi-analytical model of double gate (DG) tunneling field-effect transistor (TFET) is proposed. By aid of introducing two rectangular sources located in the gate dielectric layer and the channel, the 2-D Poisson equation is solved by using a semi-analytical method combined with an eigenfunction expansion method. The expression of the surface potential is obtained, which is a special function for the infinite series expressions. The influence of the mobile charges on the potential profile is taken into account in the proposed model. On the basis of the potential profile, the shortest tunneling length and the average electrical field can be derived, and the drain current is then constructed by using Kane's model. In particular, the changes of the tunneling parameters Ak and Bk influenced by the drain—source voltage are also incorporated in the predicted model. The proposed model shows a good agreement with TCAD simulation results under different drain—source voltages, silicon film thicknesses, gate dielectric layer thicknesses, and gate dielectric layer constants. Therefore, it is useful to optimize the DG TFET and this provides a physical insight for circuit level design. Project supported by the National Natural Science Foundation of China (No. 61376106) and the Graduate Innovation Fund of Anhui University.

  4. Cellular defibrillation: interaction of micro-scale electric fields with voltage-gated ion channels.

    PubMed

    Kargol, Armin; Malkinski, Leszek; Eskandari, Rahmatollah; Carter, Maya; Livingston, Daniel

    2015-09-01

    We study the effect of micro-scale electric fields on voltage-gated ion channels in mammalian cell membranes. Such micro- and nano-scale electric fields mimic the effects of multiferroic nanoparticles that were recently proposed [1] as a novel way of controlling the function of voltage-sensing biomolecules such as ion channels. This article describes experimental procedures and initial results that reveal the effect of the electric field, in close proximity of cells, on the ion transport through voltage-gated ion channels. We present two configurations of the whole-cell patch-clamping apparatus that were used to detect the effect of external stimulation on ionic currents and discuss preliminary results that indicate modulation of the ionic currents consistent with the applied stimulus. PMID:26067055

  5. Attosecond x-ray source generation from two-color polarized gating plasmonic field enhancement

    SciTech Connect

    Feng, Liqiang; State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023 ; Yuan, Minghu; Chu, Tianshu; Institute for Computational Sciences and Engineering, Laboratory of New Fiber Materials and Modern Textile, The Growing Base for State Key Laboratory, Qingdao University, Qingdao 266071

    2013-12-15

    The plasmonic field enhancement from the vicinity of metallic nanostructures as well as the polarization gating technique has been utilized to the generation of the high order harmonic and the single attosecond x-ray source. Through numerical solution of the time-dependent Schrödinger equation, for moderate the inhomogeneity and the polarized angle of the two fields, we find that not only the harmonic plateau has been extended and enhanced but also the single short quantum path has been selected to contribute to the harmonic. As a result, a series of 50 as pulses around the extreme ultraviolet and the x-ray regions have been obtained. Furthermore, by investigating the other parameters effects on the harmonic emission, we find that this two-color polarized gating plasmonic field enhancement scheme can also be achieved by the multi-cycle pulses, which is much better for experimental realization.

  6. Sub-10 nm transparent all-around-gated ambipolar ionic field effect transistor

    NASA Astrophysics Data System (ADS)

    Lee, Seung-Hyun; Lee, Hyomin; Jin, Tianguang; Park, Sungmin; Yoon, Byung Jun; Sung, Gun Yong; Kim, Ki-Bum; Kim, Sung Jae

    2014-12-01

    In this paper, we developed a versatile ionic field effect transistor (IFET) which has an ambipolar function for manipulating molecules regardless of their polarity and can be operated at a wide range of electrolytic concentrations (10-5 M-1 M). The IFET has circular nanochannels radially covered by gate electrodes, called ``all-around-gate'', with an aluminum oxide (Al2O3) oxide layer of a near-zero surface charge. Experimental and numerical validations were conducted for characterizing the IFET. We found that the versatility originated from the zero-charge density of the oxide layer and all-around-gate structure which increased the efficiency of the gate effect 5 times higher than a previously developed planar-gate by capacitance calculations. Our numerical model adapted Poisson-Nernst-Planck-Stokes (PNPS) formulations with additional nonlinear constraints of a fringing field effect and a counter-ion condensation and the experimental and numerical results were well matched. The device can control the transportation of ions at concentrations up to 1 M electrolyte which resembles a backflow of a shale gas extraction process. Furthermore, while traditional IFETs can manipulate either positively or negatively charged species depending on the inherently large surface charge of oxide layer, the presenting device and mechanism provide effective means to control the motion of both negatively and positively charged molecules which is important in biomolecule transport through nanochannels, medical diagnosis system and point-of-care system, etc.In this paper, we developed a versatile ionic field effect transistor (IFET) which has an ambipolar function for manipulating molecules regardless of their polarity and can be operated at a wide range of electrolytic concentrations (10-5 M-1 M). The IFET has circular nanochannels radially covered by gate electrodes, called ``all-around-gate'', with an aluminum oxide (Al2O3) oxide layer of a near-zero surface charge. Experimental and

  7. The effect of the electric-field on the phase separation of semiconductor-insulator composite film.

    PubMed

    Wang, Shiwei; Chen, Zhuo; Wang, Yao

    2015-01-14

    An electric-field induced technique has been successfully utilized to control the phase separation and the interfaces of semiconductor-insulator composite film, which provided a new research approach for scientists working in related fields. PMID:25420635

  8. Electric Field-induced Resistance Switching in VO2 Channels using Hybrid Gate Dielectric of High- k Ta2O5/Organic material Parylene-C

    NASA Astrophysics Data System (ADS)

    Wei, Tingting; Kanki, Teruo; Fujiwara, Kohei; Chikanari, Masashi; Tanaka, Hidekazu

    Electrostatic approach utilizing field-effect transistor (FET) with correlated electron materials provides an avenue to realize the novel devices (Mott-transistor) and to clarify condensed matter physics. In this study, we have prepared Mott-transistors using vanadium dioxide (VO2) channels and employed hybrid gate dielectric consisted of high- k material Ta2O5 and organic polymer parylene-C to trigger carrier transport modulation in VO2. Obvious resistance modulations were observed in insulating regime through time-dependent resistance measurement at varied square-shaped gate bias (VG) . Contrasting to the hysteretic response in electric double layer transistor (EDLT), an abrupt resistance switching in less than of 2-second-interval enables us to attribute such immediate modulation to pure electrostatic effect. Moreover, the maximum of resistance change was identified to appear around phase transition temperature (TMI) , which confirmed the disordered heterogeneous regime at TMI. Taking advantage of systematic modulation using VO2-based devices, we demonstrated the pronounced shifts of TMI by gate bias. Another fascinating behavior on asymmetric drop in TMI by hole-electron carrier doping was observed.

  9. Giant frequency tunability enabled by external magnetic and a gate electric fields in graphene devices.

    PubMed

    Hu, Xiang; Huang, Qiuping; Zhao, Yi; Cai, Honglei; Knize, Randy J; Lu, Yalin

    2016-03-21

    Graphene possesses a unique Landau level system that is non-equidistantly spaced in energy, as thus a large amount of optical transitions may become possible. Here, by utilizing this unique feature, we propose a novel dual field method which combines both external magnetic field and gate electric field together to control the optical response of the graphene-based devices. The key principle of this method is to selectively allow different optical transitions in graphene among Landau levels via an electric gate tuning of the Fermi level. By applying this method to a graphene based amplitude modulator and through an implementation based on transfer matrix method, we numerically demonstrated the well characteristics of switchable modulation on four individual channels, a huge modulation depth up to 80 dB and an extremely low required energy of tuning Fermi level down to 10 meV. Such excellent frequency tunability and gate controlling ability of this dual field method may open up the potential for applications in active optoelectronics, spin optics, ultrafast optics and etc. PMID:27136850

  10. Space charge effects on the current-voltage characteristics of gated field emitter arrays

    NASA Astrophysics Data System (ADS)

    Jensen, K. L.; Kodis, M. A.; Murphy, R. A.; Zaidman, E. G.

    1997-07-01

    Microfabricated field emitter arrays (FEAs) can provide the very high electron current densities required for rf amplifier applications, typically on the order of 100 A/cm2. Determining the dependence of emission current on gate voltage is important for the prediction of emitter performance for device applications. Field emitters use high applied fields to extract current, and therefore, unlike thermionic emitters, the current densities can exceed 103A/cm2 when averaged over an array. At such high current densities, space charge effects (i.e., the influence of charge between cathode and collector on emission) affect the emission process or initiate conditions which can lead to failure mechanisms for field emitters. A simple model of a field emitter will be used to calculate the one-dimensional space charge effects on the emission characteristics by examining two components: charge between the gate and anode, which leads to Child's law, and charge within the FEA unit cell, which gives rise to a field suppression effect which can exist for a single field emitter. The predictions of the analytical model are compared with recent experimental measurements designed to assess space charge effects and predict the onset of gate current. It is shown that negative convexity on a Fowler-Nordheim plot of Ianode(Vgate) data can be explained in terms of field depression at the emitter tip in addition to reflection of electrons by a virtual cathode created when the anode field is insufficient to extract all of the current; in particular, the effects present within the unit cell constitute a newly described effect.

  11. Photoconductivity oscillations in surface state of three-dimensional topological insulator subjected to a magnetic field

    SciTech Connect

    Shao, J. M.; Yao, J. D.; Yang, G. W.

    2015-05-21

    We describe a theoretical study of the terahertz (THz) radiation field-induced dc transport response of the surface state of a 3D topological insulator that has been subjected to a perpendicular magnetic field. Using the Landau–Floquet state and linear response theory, we obtain the photoconductivity characteristics for various types of polarized THz field. The longitudinal photoconductivity shows a clear oscillatory dependence on ω/ω{sub B}, where ω{sub B}=v{sub F}√(2eB/ℏ). This oscillation occurs because of the oscillatory structure of the Landau density of states and occurs in agreement with the photon-assisted transitions between the different Landau levels. The THz field's polarization has a major influence on the photoconductivity. A linear transverse polarization will lead to the most obvious oscillation, while the circular polarization is next to it, but the longitudinal polarization has no influence. We also discuss the broadening effect on the impurity potential and its influence. The findings with regard to the interactions between topological insulators and THz fields actually open a path toward the development of THz device applications of topological insulators.

  12. Interdigitated gate electrode field effect transistor for the selective detection of nitrogen dioxide and diisopropyl methylphosphonate

    SciTech Connect

    Kolesar, E.S. Jr.; Wiseman, J.M. )

    1989-11-01

    An interdigitated gate electrode field effect transistor (IGE-FET) coupled to an electron beam evaporated copper phthalocyanine thin film was used to selectively detect part-per-billion concentration levels of nitrogen dioxide (NO{sub 2}) and diisopropyl methylphosphonate (DIMP). The sensor is excited with a voltage pulse, and the time- and frequency-domain responses are measured. The envelopes of the magnitude of the normalized difference frequency spectrums reveal features that unambiguously distinguish NO{sub 2} and DIMP exposures.

  13. Implementing a Microcontroller Watchdog with a Field-Programmable Gate Array (FPGA)

    NASA Technical Reports Server (NTRS)

    Straka, Bartholomew

    2013-01-01

    Reliability is crucial to safety. Redundancy of important system components greatly enhances reliability and hence safety. Field-Programmable Gate Arrays (FPGAs) are useful for monitoring systems and handling the logic necessary to keep them running with minimal interruption when individual components fail. A complete microcontroller watchdog with logic for failure handling can be implemented in a hardware description language (HDL.). HDL-based designs are vendor-independent and can be used on many FPGAs with low overhead.

  14. Synchronization in coupled Ikeda delay systems. Experimental observations using Field Programmable Gate Arrays

    NASA Astrophysics Data System (ADS)

    Valli, D.; Muthuswamy, B.; Banerjee, S.; Ariffin, M. R. K.; Wahab, A. W. A.; Ganesan, K.; Subramaniam, C. K.; Kurths, J.

    2014-06-01

    In this work, we demonstrate the use of a Field Programmable Gate Array (FPGA) as a physical platform for realizing chaotic delay differential equations (DDE). Moreover, using our platform, we also experimentally study the synchronization between two time delayed systems. We illustrate two different experimental approaches - one is hardware co-simulation (using a Digilent Atlys with a Xilinx Spartan-6 FPGA) and the other is analog output (using a Terasic DE2-115 with an Altera Cyclone IV E FPGA).

  15. Explicit drain current model of junctionless double-gate field-effect transistors

    NASA Astrophysics Data System (ADS)

    Yesayan, Ashkhen; Prégaldiny, Fabien; Sallese, Jean-Michel

    2013-11-01

    This paper presents an explicit drain current model for the junctionless double-gate metal-oxide-semiconductor field-effect transistor. Analytical relationships for the channel charge densities and for the drain current are derived as explicit functions of applied terminal voltages and structural parameters. The model is validated with 2D numerical simulations for a large range of channel thicknesses and is found to be very accurate for doping densities exceeding 1018 cm-3, which are actually used for such devices.

  16. A simple laser locking system based on a field-programmable gate array

    NASA Astrophysics Data System (ADS)

    Jørgensen, N. B.; Birkmose, D.; Trelborg, K.; Wacker, L.; Winter, N.; Hilliard, A. J.; Bason, M. G.; Arlt, J. J.

    2016-07-01

    Frequency stabilization of laser light is crucial in both scientific and industrial applications. Technological developments now allow analog laser stabilization systems to be replaced with digital electronics such as field-programmable gate arrays, which have recently been utilized to develop such locking systems. We have developed a frequency stabilization system based on a field-programmable gate array, with emphasis on hardware simplicity, which offers a user-friendly alternative to commercial and previous home-built solutions. Frequency modulation, lock-in detection, and a proportional-integral-derivative controller are programmed on the field-programmable gate array and only minimal additional components are required to frequency stabilize a laser. The locking system is administered from a host-computer which provides comprehensive, long-distance control through a versatile interface. Various measurements were performed to characterize the system. The linewidth of the locked laser was measured to be 0.7 ± 0.1 MHz with a settling time of 10 ms. The system can thus fully match laser systems currently in use for atom trapping and cooling applications.

  17. Neutron production using a pyroelectric driven target coupled with a gated field ionization source

    SciTech Connect

    Ellsworth, J. L.; Tang, V.; Falabella, S.; Naranjo, B.; Putterman, S.

    2013-04-19

    A palm sized, portable neutron source would be useful for widespread implementation of detection systems for shielded, special nuclear material. We present progress towards the development of the components for an ultracompact neutron generator using a pulsed, meso-scale field ionization source, a deuterated (or tritiated) titanium target driven by a negative high voltage lithium tantalate crystal. Neutron production from integrated tests using an ion source with a single, biased tungsten tip and a 3 Multiplication-Sign 1 cm, vacuum insulated crystal with a plastic deuterated target are presented. Component testing of the ion source with a single tip produces up to 3 nA of current. Dielectric insulation of the lithium tantalate crystals appears to reduce flashover, which should improve the robustness. The field emission losses from a 3 cm diameter crystal with a plastic target and 6 cm diameter crystal with a metal target are compared.

  18. Fabrication and characterization of a charge-biased CMOS-MEMS resonant gate field effect transistor

    NASA Astrophysics Data System (ADS)

    Chin, C. H.; Li, C. S.; Li, M. H.; Wang, Y. L.; Li, S. S.

    2014-09-01

    A high-frequency charge-biased CMOS-MEMS resonant gate field effect transistor (RGFET) composed of a metal-oxide composite resonant-gate structure and an FET transducer has been demonstrated utilizing the TSMC 0.35 μm CMOS technology with Q > 1700 and a signal-to-feedthrough ratio greater than 35 dB under a direct two-port measurement configuration. As compared to the conventional capacitive-type MEMS resonators, the proposed CMOS-MEMS RGFET features an inherent transconductance gain (gm) offered by the FET transduction capable of enhancing the motional signal of the resonator and relaxing the impedance mismatch issue to its succeeding electronics or 50 Ω-based test facilities. In this work, we design a clamped-clamped beam resonant-gate structure right above a floating gate FET transducer as a high-Q building block through a maskless post-CMOS process to combine merits from the large capacitive transduction areas of the large-width beam resonator and the high gain of the underneath FET. An analytical model is also provided to simulate the behavior of the charge-biased RGFET; the theoretical prediction is in good agreement with the experimental results. Thanks to the deep-submicrometer gap spacing enabled by the post-CMOS polysilicon release process, the proposed resonator under a purely capacitive transduction already attains motional impedance less than 10 kΩ, a record-low value among CMOS-MEMS capacitive resonators. To go one step further, the motional signal of the proposed RGFET is greatly enhanced through the FET transduction. Such a strong transmission and a sharp phase transition across 0° pave a way for future RGFET-type oscillators in RF and sensor applications. A time-elapsed characterization of the charge leakage rate for the floating gate is also carried out.

  19. Effective field theory of a topological insulator and the Foldy-Wouthuysen transformation

    NASA Astrophysics Data System (ADS)

    Dayi, Ömer F.; Elbistan, Mahmut; Yunt, Elif

    2012-03-01

    Employing the Foldy-Wouthuysen transformation, it is demonstrated straightforwardly that the first and second Chern numbers are equal to the coefficients of the 2+1 and 4+1 dimensional Chern-Simons actions which are generated by the massive Dirac fermions coupled to the Abelian gauge fields. A topological insulator model in 2+1 dimensions is discussed and by means of a dimensional reduction approach the 1+1 dimensional descendant of the 2+1 dimensional Chern-Simons theory is presented. Field strength of the Berry gauge field corresponding to the 4+1 dimensional Dirac theory is explicitly derived through the Foldy-Wouthuysen transformation. Acquainted with it, the second Chern numbers are calculated for specific choices of the integration domain. A method is proposed to obtain 3+1 and 2+1 dimensional descendants of the effective field theory of the 4+1 dimensional time reversal invariant topological insulator theory. Inspired by the spin Hall effect in graphene, a hypothetical model of the time reversal invariant spin Hall insulator in 3+1 dimensions is proposed.

  20. Dual field effects in electrolyte-gated spinel ferrite: electrostatic carrier doping and redox reactions

    PubMed Central

    Ichimura, Takashi; Fujiwara, Kohei; Tanaka, Hidekazu

    2014-01-01

    Controlling the electronic properties of functional oxide materials via external electric fields has attracted increasing attention as a key technology for next-generation electronics. For transition-metal oxides with metallic carrier densities, the electric-field effect with ionic liquid electrolytes has been widely used because of the enormous carrier doping capabilities. The gate-induced redox reactions revealed by recent investigations have, however, highlighted the complex nature of the electric-field effect. Here, we use the gate-induced conductance modulation of spinel ZnxFe3−xO4 to demonstrate the dual contributions of volatile and non-volatile field effects arising from electronic carrier doping and redox reactions. These two contributions are found to change in opposite senses depending on the Zn content x; virtual electronic and chemical field effects are observed at appropriate Zn compositions. The tuning of field-effect characteristics via composition engineering should be extremely useful for fabricating high-performance oxide field-effect devices. PMID:25056718

  1. Dual field effects in electrolyte-gated spinel ferrite: electrostatic carrier doping and redox reactions

    NASA Astrophysics Data System (ADS)

    Ichimura, Takashi; Fujiwara, Kohei; Tanaka, Hidekazu

    2014-07-01

    Controlling the electronic properties of functional oxide materials via external electric fields has attracted increasing attention as a key technology for next-generation electronics. For transition-metal oxides with metallic carrier densities, the electric-field effect with ionic liquid electrolytes has been widely used because of the enormous carrier doping capabilities. The gate-induced redox reactions revealed by recent investigations have, however, highlighted the complex nature of the electric-field effect. Here, we use the gate-induced conductance modulation of spinel ZnxFe3-xO4 to demonstrate the dual contributions of volatile and non-volatile field effects arising from electronic carrier doping and redox reactions. These two contributions are found to change in opposite senses depending on the Zn content x; virtual electronic and chemical field effects are observed at appropriate Zn compositions. The tuning of field-effect characteristics via composition engineering should be extremely useful for fabricating high-performance oxide field-effect devices.

  2. Novel process for widening memory window of sub-200 nm ferroelectric-gate field-effect transistor by ferroelectric coating the gate-stack sidewall

    NASA Astrophysics Data System (ADS)

    Van Hai, Le; Takahashi, Mitsue; Zhang, Wei; Sakai, Shigeki

    2015-01-01

    Ferroelectric-gate field-effect transistors (FeFETs) with metallurgical-gate lengths of 140 nm, 160 nm and 190 nm were successfully fabricated using a novel fabrication process. The gate stacks of the FeFETs were Pt/Sr0.8Ca0.2Bi2Ta2O9(SCBT)/HfO2/Si. Key to the process was covering the as-etched gate-stack sidewalls with SCBT precursor films and annealing altogether. The FeFETs which underwent the novel process showed larger memory windows than those without the process by about 0.5 V at scanned gate-voltages of 1 ± 5 V. Endurances of the FeFETs made by the novel process were measured up to 109 cycles with good separations of the on- and off-states. The endurance pulses were 1 ± 5 V with 2 μs period. Good data-retentions of them were also demonstrated which were measured for at least 6.5 days.

  3. Residential sidewall insulation case histories, including experiences and problems in the field application of loose fill

    SciTech Connect

    Infante, L.J.; Aller, P.F.; Fay, R.E.

    1983-01-01

    An unbonded fiberglass loose-fill insulation was selected for this sidewall application study. The insert tube technique is described and the parameters that affect pneumatic application of the product are identified. The initial evaluation was conducted in the laboratory and included density and thermal testing. The laboratory results were then utilized in field studies. Ten homes with no sidewall insulation were retrofitted. Thermographic scans of sidewalls before and after retrofit confirmed the predicted reductions in heat loss based on calculation techniques given in the ASHRAE Handbook of Fundamentals. The improvement was further confirmed by comparing utility bills. Typical problems that occur while preparing a house for sidewall retrofit are discussed. The simple payback for typical houses is presented. Good correlation is shown between laboratory test results and field performance. Test data indicate that the application procedure used gave an effective R-value per product claim.

  4. Chiral magnetism and spin liquid Mott insulators induced by synthetic gauge fields

    NASA Astrophysics Data System (ADS)

    Paramekanti, Arun; Hickey, Ciaran; Cincio, Lukasz; Papic, Zlatko; Vellat-Sadashivan, Arun; Sohal, Ramanjit

    2016-05-01

    Recent experiments using Raman-assisted tunneling or lattice-shaking have realized synthetic gauge fields and optical lattice bands with nontrivial band topology. Here we examine the effect of particle interactions in such bands, focussing on two-component fermions with local Hubbard repulsion. We show that interactions can drive the integer quantum Hall insulator into Mott insulating states which possess noncoplanar chiral magnetic textures and even chiral spin liquids with many-body topological order. We establish our results using a combination of mean field theory, strong coupling expansions, numerical exact diagonalization and DMRG methods. We also discuss possible signatures of such non-coplanar orders in Bragg scattering and noise measurements.

  5. Thermal radiative near field transport between vanadium dioxide and silicon oxide across the metal insulator transition

    NASA Astrophysics Data System (ADS)

    Menges, F.; Dittberner, M.; Novotny, L.; Passarello, D.; Parkin, S. S. P.; Spieser, M.; Riel, H.; Gotsmann, B.

    2016-04-01

    The thermal radiative near field transport between vanadium dioxide and silicon oxide at submicron distances is expected to exhibit a strong dependence on the state of vanadium dioxide which undergoes a metal-insulator transition near room temperature. We report the measurement of near field thermal transport between a heated silicon oxide micro-sphere and a vanadium dioxide thin film on a titanium oxide (rutile) substrate. The temperatures of the 15 nm vanadium dioxide thin film varied to be below and above the metal-insulator-transition, and the sphere temperatures were varied in a range between 100 and 200 °C. The measurements were performed using a vacuum-based scanning thermal microscope with a cantilevered resistive thermal sensor. We observe a thermal conductivity per unit area between the sphere and the film with a distance dependence following a power law trend and a conductance contrast larger than 2 for the two different phase states of the film.

  6. Suspended InAs nanowire gate-all-around field-effect transistors

    SciTech Connect

    Li, Qiang; Huang, Shaoyun E-mail: hqxu@pku.edu.cn; Wang, Jingyun; Pan, Dong; Zhao, Jianhua; Xu, H. Q. E-mail: hqxu@pku.edu.cn

    2014-09-15

    Gate-all-around field-effect transistors are realized with thin, single-crystalline, pure-phase InAs nanowires grown by molecular beam epitaxy. At room temperature, the transistors show a desired high on-state current I{sub on} of ∼10 μA and an on-off current ratio I{sub on}/I{sub off} of as high as 10{sup 6} at source-drain bias voltage of 50 mV and gate length of 1 μm with a gate underlap spacing of 1 μm from the source and from the drain. At low temperatures, the on-state current I{sub on} is only slightly reduced, while the ratio I{sub on}/I{sub off} is increased to 10{sup 7}. The field-effect mobility in the nanowire channels is also investigated and found to be ∼1500 cm{sup 2}/V s at room temperature and ∼2000 cm{sup 2}/V s at low temperatures. The excellent performance of the transistors is explained in terms of strong electrostatic and quantum confinements of carriers in the nanowires.

  7. A novel Tunneling Graphene Nano Ribbon Field Effect Transistor with dual material gate: Numerical studies

    NASA Astrophysics Data System (ADS)

    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.

  8. Experimental Investigation on Liquid Metal Flow Distribution in Insulating Manifold under Uniform Magnetic Field

    NASA Astrophysics Data System (ADS)

    Miura, Masato; Ueki, Yoshitaka; Yokomine, Takehiko; Kunugi, Tomoaki

    2012-11-01

    Magnetohydrodynamics (MHD) problem which is caused by interaction between electrical conducting fluid flow and the magnetic field is one of the biggest problem in the liquid metal blanket of the fusion reactor. In the liquid metal blanket concept, it is necessary to distribute liquid metal flows uniformly in the manifold because imbalance of flow rates should affect the heat transfer performance directly, which leads to safety problem. While the manifold is insulated electrically as well as the flow duct, the 3D-MHD effect on the flowing liquid metal in the manifold is more apparent than that in straight duct. With reference to the flow distribution in this concept, the liquid metal flow in the electrical insulating manifold under the uniform transverse magnetic field is investigated experimentally. In this study, GaInSn is selected as working fluid. The experimental system includes the electrical magnet and the manifold test section which is made of acrylic resin for perfectly electrical insulation. The liquid metal flows in a non-symmetric 180°-turn with manifold, which consists of one upward channel and two downward channels. The flow rates in each channel are measured by electromagnetic flow meters for several combinations Reynolds number and Hartman number. The effects of magnetic field on the uniformity of flow distribution are cleared.

  9. Low voltage, high performance inkjet printed carbon nanotube transistors with solution processed ZrO2 gate insulator

    NASA Astrophysics Data System (ADS)

    Kim, Bongjun; Jang, Seonpil; Prabhumirashi, Pradyumna L.; Geier, Michael L.; Hersam, Mark C.; Dodabalapur, Ananth

    2013-08-01

    High-performance single-walled carbon nanotube (SWCNT) thin-film transistors are fabricated by single-pass inkjet printing of SWCNTs on high-κ solution-processed ZrO2 gate dielectric. We demonstrate that an ultraviolet ozone treatment of the ZrO2 substrate is critical in achieving a uniform dispersion of sorted SWCNTs in the semiconducting channel. The resulting devices exhibit excellent performance with mobility and on/off current ratio exceeding 30 cm2 V-1 s-1 and 105, respectively, at low operating voltages (<5 V). The single-pass inkjet printing process demonstrated in this letter shows great promise as a reliable and scalable method for SWCNT based high performance electronics.

  10. Characterization of SiO{sub 2}/SiN{sub x} gate insulators for graphene based nanoelectromechanical systems

    SciTech Connect

    Tóvári, E.; Csontos, M. Kriváchy, T.; Csonka, S.; Fürjes, P.

    2014-09-22

    The structural and magnetotransport characterization of graphene nanodevices exfoliated onto Si/SiO{sub 2}/SiN{sub x} heterostructures are presented. Improved visibility of the deposited flakes is achieved by optimal tuning of the dielectric film thicknesses. The conductance of single layer graphene Hall-bar nanostructures utilizing SiO{sub 2}/SiN{sub x} gate dielectrics were characterized in the quantum Hall regime. Our results highlight that, while exhibiting better mechanical and chemical stability, the effect of non-stoichiometric SiN{sub x} on the charge carrier mobility of graphene is comparable to that of SiO{sub 2}, demonstrating the merits of SiN{sub x} as an ideal material platform for graphene based nanoelectromechanical applications.

  11. Effect of annealing temperature of Bi1.5Zn1.0Nb1.5O7 gate insulator on performance of ZnO based thin film transistors

    NASA Astrophysics Data System (ADS)

    Wei, Ye; Wei, Ren; Peng, Shi; Zhuangde, Jiang

    2016-07-01

    The bottom-gate structure ZnO based thin film transistors (ZnO-TFTs) using Bi1.5Zn1.0Nb1.5O7 (BZN) thin films as gate insulator were fabricated on Pt/SiO2/Si substrate by radio frequency magnetic sputtering. We investigated the effect of annealing temperature at 300, 400, and 500 °C on the performance of BZN thin films and ZnO-TFTs. XRD measurement confirmed that BZN thin films were amorphous in nature. BZN thin films annealed at 400 °C obtain the high capacitance density of 249 nF/cm2, high dielectric constant of 71, and low leakage current density of 10‑7 A/cm2 on/off current ratio and field effect mobility of ZnO-TFTs annealed at 400 °C are approximately one order of magnitude and two times, respectively higher than that of ZnO-TFTs annealed at 300 °C. When the annealing temperature is 400 °C, the electrical performance of ZnO-TFTs is enhanced remarkably. Devices obtain a low sub-threshold swing of 470 mV/dec and surface states density of 3.21 × 1012cm‑2. Project supported by the National Natural Science Foundation of China (Nos. 51332003, 51202184), the International Science & Technology Cooperation Program of China (Nos. 2010DFB13640, 2011DFA51880), and the “111 Project” of China (No. B14040).

  12. Trap density probing on top-gate MoS2 nanosheet field-effect transistors by photo-excited charge collection spectroscopy

    NASA Astrophysics Data System (ADS)

    Choi, Kyunghee; Raza, Syed Raza Ali; Lee, Hee Sung; Jeon, Pyo Jin; Pezeshki, Atiye; Min, Sung-Wook; Kim, Jin Sung; Yoon, Woojin; Ju, Sang-Yong; Lee, Kimoon; Im, Seongil

    2015-03-01

    Two-dimensional (2D) molybdenum disulfide (MoS2) field-effect transistors (FETs) have been extensively studied, but most of the FETs with gate insulators have displayed negative threshold voltage values, which indicates the presence of interfacial traps both shallow and deep in energy level. Despite such interface trap issues, reports on trap densities in MoS2 are quite limited. Here, we probed top-gate MoS2 FETs with two- (2L), three- (3L), and four-layer (4L) MoS2/dielectric interfaces to quantify deep-level interface trap densities by photo-excited charge collection spectroscopy (PECCS), and reported the result that deep-level trap densities over 1012 cm-2 may exist in the interface and bulk MoS2 near the interface. Transfer curve hysteresis and PECCS measurements show that shallow traps and deep traps are not that different in density order from each other. We conclude that our PECCS analysis distinguishably provides valuable information on deep level interface/bulk trap densities in 2D-based FETs.Two-dimensional (2D) molybdenum disulfide (MoS2) field-effect transistors (FETs) have been extensively studied, but most of the FETs with gate insulators have displayed negative threshold voltage values, which indicates the presence of interfacial traps both shallow and deep in energy level. Despite such interface trap issues, reports on trap densities in MoS2 are quite limited. Here, we probed top-gate MoS2 FETs with two- (2L), three- (3L), and four-layer (4L) MoS2/dielectric interfaces to quantify deep-level interface trap densities by photo-excited charge collection spectroscopy (PECCS), and reported the result that deep-level trap densities over 1012 cm-2 may exist in the interface and bulk MoS2 near the interface. Transfer curve hysteresis and PECCS measurements show that shallow traps and deep traps are not that different in density order from each other. We conclude that our PECCS analysis distinguishably provides valuable information on deep level interface

  13. Physiologically gated microbeam radiation using a field emission x-ray source array

    SciTech Connect

    Chtcheprov, Pavel E-mail: zhou@email.unc.edu; Burk, Laurel; Inscoe, Christina; Ger, Rachel; Hadsell, Michael; Lu, Jianping; Yuan, Hong; Zhang, Lei; Chang, Sha; Zhou, Otto E-mail: zhou@email.unc.edu

    2014-08-15

    Purpose: Microbeam radiation therapy (MRT) uses narrow planes of high dose radiation beams to treat cancerous tumors. This experimental therapy method based on synchrotron radiation has been shown to spare normal tissue at up to 1000 Gy of peak entrance dose while still being effective in tumor eradication and extending the lifetime of tumor-bearing small animal models. Motion during treatment can lead to significant movement of microbeam positions resulting in broader beam width and lower peak to valley dose ratio (PVDR), which reduces the effectiveness of MRT. Recently, the authors have demonstrated the feasibility of generating microbeam radiation for small animal treatment using a carbon nanotube (CNT) x-ray source array. The purpose of this study is to incorporate physiological gating to the CNT microbeam irradiator to minimize motion-induced microbeam blurring. Methods: The CNT field emission x-ray source array with a narrow line focal track was operated at 160 kVp. The x-ray radiation was collimated to a single 280 μm wide microbeam at entrance. The microbeam beam pattern was recorded using EBT2 Gafchromic{sup ©} films. For the feasibility study, a strip of EBT2 film was attached to an oscillating mechanical phantom mimicking mouse chest respiratory motion. The servo arm was put against a pressure sensor to monitor the motion. The film was irradiated with three microbeams under gated and nongated conditions and the full width at half maximums and PVDRs were compared. An in vivo study was also performed with adult male athymic mice. The liver was chosen as the target organ for proof of concept due to its large motion during respiration compared to other organs. The mouse was immobilized in a specialized mouse bed and anesthetized using isoflurane. A pressure sensor was attached to a mouse's chest to monitor its respiration. The output signal triggered the electron extraction voltage of the field emission source such that x-ray was generated only during a

  14. Physiologically gated microbeam radiation using a field emission x-ray source array

    PubMed Central

    Chtcheprov, Pavel; Burk, Laurel; Yuan, Hong; Inscoe, Christina; Ger, Rachel; Hadsell, Michael; Lu, Jianping; Zhang, Lei; Chang, Sha; Zhou, Otto

    2014-01-01

    Purpose: Microbeam radiation therapy (MRT) uses narrow planes of high dose radiation beams to treat cancerous tumors. This experimental therapy method based on synchrotron radiation has been shown to spare normal tissue at up to 1000 Gy of peak entrance dose while still being effective in tumor eradication and extending the lifetime of tumor-bearing small animal models. Motion during treatment can lead to significant movement of microbeam positions resulting in broader beam width and lower peak to valley dose ratio (PVDR), which reduces the effectiveness of MRT. Recently, the authors have demonstrated the feasibility of generating microbeam radiation for small animal treatment using a carbon nanotube (CNT) x-ray source array. The purpose of this study is to incorporate physiological gating to the CNT microbeam irradiator to minimize motion-induced microbeam blurring. Methods: The CNT field emission x-ray source array with a narrow line focal track was operated at 160 kVp. The x-ray radiation was collimated to a single 280 μm wide microbeam at entrance. The microbeam beam pattern was recorded using EBT2 Gafchromic© films. For the feasibility study, a strip of EBT2 film was attached to an oscillating mechanical phantom mimicking mouse chest respiratory motion. The servo arm was put against a pressure sensor to monitor the motion. The film was irradiated with three microbeams under gated and nongated conditions and the full width at half maximums and PVDRs were compared. An in vivo study was also performed with adult male athymic mice. The liver was chosen as the target organ for proof of concept due to its large motion during respiration compared to other organs. The mouse was immobilized in a specialized mouse bed and anesthetized using isoflurane. A pressure sensor was attached to a mouse's chest to monitor its respiration. The output signal triggered the electron extraction voltage of the field emission source such that x-ray was generated only during a

  15. Side-by-Side Field Evaluation of Highly Insulating Windows in the PNNL Lab Homes

    SciTech Connect

    Widder, Sarah H.; Parker, Graham B.; Baechler, Michael C.; Bauman, Nathan N.

    2012-08-01

    To examine the energy, air leakage, and thermal performance of highly insulating windows, a field evaluation was undertaken in a matched pair of all-electric, factory-built “Lab Homes” located on the Pacific Northwest National Laboratory (PNNL) campus in Richland, Washington. The “baseline” Lab Home B was retrofitted with “standard” double-pane clear aluminum-frame slider windows and patio doors, while the “experimental” Lab Home A was retrofitted with Jeld-Wen® triple-pane vinyl-frame slider windows and patio doors with a U-factor of 0.2 and solar heat gain coefficient of 0.19. To assess the window, the building shell air leakage, energy use, and interior temperatures of each home were compared during the 2012 winter heating and summer cooling seasons. The measured energy savings in Lab Home B averaged 5,821 watt-hours per day (Wh/day) during the heating season and 6,518 Wh/day during the cooling season. The overall whole-house energy savings of Lab Home B compared to Lab Home A are 11.6% ± 1.53% for the heating season and 18.4 ± 2.06% for the cooling season for identical occupancy conditions with no window coverings deployed. Extrapolating these energy savings numbers based on typical average heating degree days and cooling degree days per year yields an estimated annual energy savings of 12.2%, or 1,784 kWh/yr. The data suggest that highly insulating windows are an effective energy-saving measure that should be considered for high-performance new homes and in existing retrofits. However, the cost effectiveness of the measure, as determined by the simple payback period, suggests that highly insulating window costs continue to make windows difficult to justify on a cost basis alone. Additional reductions in costs via improvements in manufacturing and/or market penetration that continue to drive down costs will make highly insulating windows much more viable as a cost-effective energy efficiency measure. This study also illustrates that highly

  16. Magnetic-Field-Induced Insulator-Conductor Transition in SU(2) Quenched Lattice Gauge Theory

    SciTech Connect

    Buividovich, P.V.; Kharzeev, D.; Chernodub, M.N., Kalaydzhyan, T., Luschevskaya, E.V., and M.I. Polikarpov

    2010-09-24

    We study the correlator of two vector currents in quenched SU(2) lattice gauge theory with a chirally invariant lattice Dirac operator with a constant external magnetic field. It is found that in the confinement phase the correlator of the components of the current parallel to the magnetic field decays much slower than in the absence of a magnetic field, while for other components the correlation length slightly decreases. We apply the maximal entropy method to extract the corresponding spectral function. In the limit of zero frequency this spectral function yields the electric conductivity of quenched theory. We find that in the confinement phase the external magnetic field induces nonzero electric conductivity along the direction of the field, transforming the system from an insulator into an anisotropic conductor. In the deconfinement phase the conductivity does not exhibit any sizable dependence on the magnetic field.

  17. Fabrication of high-k/metal-gate MoS2 field-effect transistor by device isolation process utilizing Ar-plasma etching

    NASA Astrophysics Data System (ADS)

    Ninomiya, Naruki; Mori, Takahiro; Uchida, Noriyuki; Watanabe, Eiichiro; Tsuya, Daiju; Moriyama, Satoshi; Tanaka, Masatoshi; Ando, Atsushi

    2015-04-01

    We investigated a device isolation process for MoS2-based devices and fabricated high-k/metal-gate MoS2 MOSFETs. An Ar-ion etching process was utilized for the device isolation process. It circumvents damage in the device channel, as confirmed by Raman spectroscopy. A top-gate MoS2 MOSFET was fabricated with a HfO2 thin film 16 nm thick as the gate insulator. Utilizing capacitance-voltage (C-V) measurements, the capacitance equivalent thickness (CET) was estimated to be 5.36 nm, which indicates that a gate stack with the sufficiently thin insulator was successfully realized. The device exhibited a mobility of 25.3 cm2/(V·s), a subthreshold swing (SS) of 86.0 mV/decade, and an ON/OFF ratio of 107. This satisfactory device performance demonstrates the feasibility of the proposed device isolation process.

  18. Superconducting proximity effect in three-dimensional topological insulators in the presence of a magnetic field

    NASA Astrophysics Data System (ADS)

    Burset, Pablo; Lu, Bo; Tkachov, Grigory; Tanaka, Yukio; Hankiewicz, Ewelina M.; Trauzettel, Björn

    2015-11-01

    The proximity-induced pair potential in a topological insulator-superconductor hybrid features an interesting superposition of a conventional spin-singlet component from the superconductor and a spin-triplet one induced by the surface state of the topological insulator. This singlet-triplet superposition can be altered by the presence of a magnetic field. We study the interplay between topological order and superconducting correlations performing a symmetry analysis of the induced pair potential, using Green functions techniques to theoretically describe ballistic junctions between superconductors and topological insulators under magnetic fields. We relate a change in the conductance from a gapped profile into one with a zero-energy peak with the transition into a topologically nontrivial regime where the odd-frequency triplet pairing becomes the dominant component in the pair potential. The nontrivial regime, which provides a signature of odd-frequency triplet superconductivity, is reached for an out-of-plane effective magnetization with strength comparable to the chemical potential of the superconductor or for an in-plane one, parallel to the normal-superconductor interface, with strength of the order of the superconducting gap. Strikingly, in the latter case, a misalignment with the interface yields an asymmetry with the energy in the conductance unless the total contribution of the topological surface state is considered.

  19. In-situ tuning threshold voltage of field-effect transistors based on blends of poly(3-hexylthiophene) with an insulator electret

    NASA Astrophysics Data System (ADS)

    Lu, Guanghao; Koch, Norbert; Neher, Dieter

    2015-08-01

    Blending the conjugated polymer poly(3-hexylthiophene) (P3HT) with the insulating electret polystyrene (PS), we show that the threshold voltage Vt of organic field-effect transistors (OFETs) can be easily and reversely tuned by applying a gate bias stress at 130 °C. It is proposed that this phenomenon is caused by thermally activated charge injection from P3HT into PS matrix, and that this charge is immobilized within the PS matrix after cooling down to room temperature. Therefore, room-temperature hysteresis-free FETs with desired Vt can be easily achieved. The approach is applied to reversely tune the OFET mode of operation from accumulation to depletion, and to build inverters.

  20. Gate-Induced Carrier Delocalization in Quantum Dot Field Effect Transistors

    NASA Astrophysics Data System (ADS)

    Turk, M. E.; Choi, J.-H.; Oh, S. J.; Fafarman, A. T.; Diroll, B. T.; Murray, C. B.; Kagan, C. R.; Kikkawa, J. M.

    2015-03-01

    We study the low temperature resistance and magnetotransport of high-mobility indium-doped CdSe quantum dot (QD) field effect transistors. Low temperature resistance measurements show a characteristic dependence of R (T) =R0 exp(T0 / T) p with p = 2 / 3 , consistent with a recent model based on Coulomb gap variable range hopping plus thermal broadening. We show that using the gate bias VG to accumulate electrons in the QD channel increases the ``localization product'' κa (localization length a, dielectric constant κ), as expected for Fermi level changes near an Anderson mobility edge. Under any reasonable assumptions, a increases significantly beyond the QD diameter as gate bias is applied. Magnetoresistance (MR) measurements display both positive and negative MR contributions that vary with VG and T. For each VG, we observe a universal negative MR lineshape for higher temperatures (T > 20 K) that scales as T - 4 / 3, consistent with Zeeman MR for p = 2 / 3 with a gate bias-modulated mobility gap (Δɛ). All aspects of this work supported by the U.S. Department of Energy Office of Basic Energy Sciences, Division of Materials Science and Engineering, under Award No. DE-SC0002158.

  1. Power and linearity comparisons of gate- and source-terminated field-plate pseudomorphic HEMTs

    NASA Astrophysics Data System (ADS)

    Chiu, Hsien-Chin; Cheng, Chia-Shih; Shih, Yuan-Jui

    2005-12-01

    GaAs-based pseudomorphic high electron mobility transistors (pHEMTs) in which the field-plate (FP) is connected to the gate terminal and the source terminal, were developed and evaluated experimentally to determine their microwave and power performance. The small gate-to-drain feedback capacitance (Cgd) and the stable FP-induced depletion region at high input power (Pin) of the source-terminated FP pHEMT (FP-S pHEMT) greatly improve the power and linearity of the FP-S pHEMT above those of the gate-terminated FP pHEMT (FP-G pHEMT). The power ratio of the fundamental to the third-order inter-modulation product (IM3) is 18.8 dBc for FP-S pHEMT for Pin = 0 dBm; the corresponding value for FP-G pHEMT is 12.4 dBc. These experimental results indicate that the FP architecture is more effective at high-power operation and exhibits high linearity in high-power pHEMT applications.

  2. N-Channel field-effect transistors with floating gates for extracellular recordings.

    PubMed

    Meyburg, Sven; Goryll, Michael; Moers, Jürgen; Ingebrandt, Sven; Böcker-Meffert, Simone; Lüth, Hans; Offenhäusser, Andreas

    2006-01-15

    A field-effect transistor (FET) for recording extracellular signals from electrogenic cells is presented. The so-called floating gate architecture combines a complementary metal oxide semiconductor (CMOS)-type n-channel transistor with an independent sensing area. This concept allows the transistor and sensing area to be optimised separately. The devices are robust and can be reused several times. The noise level of the devices was smaller than of comparable non-metallised gate FETs. In addition to the usual drift of FET devices, we observed a long-term drift that has to be controlled for future long-term measurements. The device performance for extracellular signal recording was tested using embryonic rat cardiac myocytes cultured on fibronectin-coated chips. The extracellular cell signals were recorded before and after the addition of the cardioactive isoproterenol. The signal shapes of the measured action potentials were comparable to the non-metallised gate FETs previously used in similar experiments. The fabrication of the devices involved the process steps of standard CMOS that were necessary to create n-channel transistors. The implementation of a complete CMOS process would facilitate the integration of the logical circuits necessary for signal pre-processing on a chip, which is a prerequisite for a greater number of sensor spots in future layouts. PMID:16029948

  3. Composite fermions and the field-tuned superconductor-insulator transition

    NASA Astrophysics Data System (ADS)

    Raghu, Srinivas; Mulligan, Michael

    In several two-dimensional films that exhibit a magnetic field-tuned superconductor to insulator transition (SIT), stable metallic phases have been observed. Building on the `dirty boson' description of the SIT, we suggest that the metallic region is analogous to the composite Fermi liquid observed about half-filled Landau levels of the two-dimensional electron gas. The composite fermions here are mobile vortices attached to one flux quantum of an emergent gauge field. The composite vortex liquid is a 2D non-Fermi liquid metal, which we argue is stable to weak quenched disorder. We describe several experimental consequences of the emergent composite vortex liquid.

  4. Experiences in the internal inspections and maintenance works on gas insulated equipment in the field

    SciTech Connect

    Kuwahara, H.; Nitta, T.; Ogawa, A.; Sasamoto, S.; Tanabe, T.

    1983-04-01

    Data have been collected through the internal inspections and maintenance works on the gas insulated equipment working in the field. Wearing of contact of circuit breakers by repetitive interruptions of current is the determining factor for internal maintenance. Factors like the quality of sealings, conditions of absorbent, deteriorative influence of arc decomposition products etc. are not the factors that require internal inspections. Practical problems in the works inside the enclosure while the neighboring part of the substation is in operation are discussed basing on the experiences in the field.

  5. Composite fermions and the field-tuned superconductor-insulator transition

    NASA Astrophysics Data System (ADS)

    Mulligan, Michael; Raghu, S.

    2016-05-01

    In several two-dimensional films that exhibit a magnetic field-tuned superconductor to insulator transition (SIT), stable metallic phases have been observed. Building on the `dirty boson' description of the SIT, we suggest that the metallic region is analogous to the composite Fermi liquid observed about half-filled Landau levels of the two-dimensional electron gas. The composite fermions here are mobile vortices attached to one flux quantum of an emergent gauge field. The composite vortex liquid is a 2D non-Fermi liquid metal, which we argue is stable to weak quenched disorder. We describe several experimental consequences of the emergent composite vortex liquid.

  6. Field-Induced Metal-Insulator Transition in a Two-Dimensional Organic Superconductor

    SciTech Connect

    Wosnitza, J.; Wanka, S.; Hagel, J.; Lo''hneysen, H. v.; Qualls, J. S.; Brooks, J. S.; Balthes, E.; Schlueter, J. A.; Geiser, U.; Mohtasham, J.

    2001-01-15

    The quasi-two-dimensional organic superconductor {beta}''-( BEDT-TTF){sub 2}SF{sub 5} CH{sub 2}CF {sub 2}SO{sub 3} (T{sub c}{approx}4.4 K) shows very strong Shubnikov--de Haas (SdH) oscillations which are superimposed on a highly anomalous steady background magnetoresistance, R{sub b} . Comparison with de Haas--van Alphen oscillations allows a reliable estimate of R{sub b} which is crucial for the correct extraction of the SdH signal. At low temperatures and high magnetic fields insulating behavior evolves. The magnetoresistance data violate Kohler's rule, i.e., cannot be described within the framework of semiclassical transport theory, but converge onto a universal curve appropriate for dynamical scaling at a metal-insulator transition.

  7. Cross-linking high-k fluoropolymer gate dielectrics enhances the charge mobility in rubrene field effect transistors

    NASA Astrophysics Data System (ADS)

    Adhikari, Jwala; Gadinski, Matthew; Wang, Qing; Gomez, Enrique

    2015-03-01

    Polymer dielectrics are promising materials where the chemical flexibility enables gate insulators with desired properties. For example, polar groups can be introduced to enhance the dielectric constant, although fluctuations in chain conformations at the semiconductor-dielectric interface can introduce energetic disorder and limit charge mobilities in thin-film transistors. Here, we demonstrate a photopatternable high-K fluoropolymer, poly(vinylidene fluoride-bromotrifluoroethylene) P(VDF-BTFE), with a dielectric constant between 8 and 11. The bromotrifluoroethylene moiety enables photo-crosslinking and stabilization of gate insulator films while also significantly enhancing the population of trans torsional conformations of the chains. Using rubrene single crystals as the active layer, charge mobilities exceeding 10 cm2/Vs are achieved in thin film transistors with cross-linked P(VDF-BTFE) gate dielectrics. We hypothesize that crosslinking reduces energetic disorder at the dielectric-semiconductor interface by suppressing segmental motion and controlling chain conformations of P(VDF-BTFE), thereby leading to approximately a three-fold enhancement in the charge mobility of rubrene thin-film transistors over devices incorporating uncross-linked dielectrics or silicon oxide. Center for Flexible Electronic, Penn State; The Dow Chemical Company.

  8. A Low Temperature, Solution-Processed Poly(4-vinylphenol), YO(x) Nanoparticle Composite/Polysilazane Bi-Layer Gate Insulator for ZnO Thin Film Transistor.

    PubMed

    Shin, Hyeonwoo; Kang, Chan-Mo; Chae, Hyunsik; Kim, Hyun-Gwan; Baek, Kyu-Ha; Choi, Hyoung Jin; Park, Man-Young; Do, Lee-Mi; Lee, Changhee

    2016-03-01

    Low temperature, solution-processed metal oxide thin film transistors (MEOTFTs) have been widely investigated for application in low-cost, transparent, and flexible electronics. To enlarge the application area, solution-processed gate insulators (GI) have been investigated in recent years. We investigated the effects of the organic/inorganic bi-layer GI to ZnO thin film transistors (TFTs). PVP, YO(x) nanoparticle composite, and polysilazane bi-layer showed low leakage current (-10(-8) A/cm2 in 2 MV), which are applicable in low temperature processed MEOTFTs. Polysilazane was used as an interlayer between ZnO and PVP, YO(x) nanoparticle composite as a good charge transport interface with ZnO. By applying the PVP, YO(x), nanoparticle composite/polysilazane bi-layer structure to ZnO TFTs, we successfully suppressed the off current (I(off)) to -10(-11) and fabricated good MEOTFTs in 180 degrees C. PMID:27455680

  9. Epitaxial growth and characterization of thick multi-layer 4H-SiC for very high-voltage insulated gate bipolar transistors

    NASA Astrophysics Data System (ADS)

    Miyazawa, Tetsuya; Nakayama, Koji; Tanaka, Atsushi; Asano, Katsunori; Ji, Shi-yang; Kojima, Kazutoshi; Ishida, Yuuki; Tsuchida, Hidekazu

    2015-08-01

    Techniques to fabricate thick multi-layer 4H-SiC epitaxial wafers were studied for very high-voltage p- and n-channel insulated gate bipolar transistors (IGBTs). Multi-layer epitaxial growth, including a thick p- drift layer (˜180 μm), was performed on a 4H-SiC n+ substrate to form a p-IGBT structure. For an n-IGBT structure, an inverted growth process was employed, in which a thick n- drift layer (˜180 μm) and a thick p++ injector layer (>55 μm) were epitaxially grown. The epitaxial growth conditions were modified to attain a low defect density, a low doping concentration, and a long carrier lifetime in the drift layers. Reduction of the forward voltage drop was attempted by using carrier lifetime enhancement processes, specifically, carbon ion implantation/annealing and thermal oxidation/annealing or hydrogen annealing. Simple PiN diodes were fabricated to demonstrate the effective conductivity modulation in the thick drift layers. The forward voltage drops of the PiN diodes with the p- and n-IGBT structures promise to obtain the extremely low-loss and very high-voltage IGBTs. The change in wafer shape during the processing of the very thick multi-layer 4H-SiC is also discussed.

  10. Floquet Topological Insulator in the BHZ Model with the Polarized Optical Field

    NASA Astrophysics Data System (ADS)

    Zhu, Hua-Xin; Wang, Tong-Tong; Gao, Jin-Song; Li, Shuai; Sun, Ya-Jun; Liu, Gui-Lin

    2014-03-01

    Topological phase of newly found matter has aroused wide interests, especially related with the external periodical modulating. With the help of the Floquet theory, we investigate the possibility of externally manipulating the topological property in a HgTe/CdTe quantum well system with the polarized optical field. We give the phase diagram, showing that by modulating the parameters of the polarized optical field, especially the phase, the topological phase transition can be realized in the QW and lead to the so-called Floquet topological insulator. When the optical field is weak, the driven QSH state of QW is robust with the optical field. However, when the optical field is relatively larger, the group velocity of edge states and the gap between the bulk states exhibit certain oscillations. The implications of our results are discussed.

  11. Effect of ZnO channel thickness on the device behaviour of nonvolatile memory thin film transistors with double-layered gate insulators of Al2O3 and ferroelectric polymer

    NASA Astrophysics Data System (ADS)

    Yoon, Sung-Min; Yang, Shin-Hyuk; Park, Sang-Hee Ko; Jung, Soon-Won; Cho, Doo-Hee; Byun, Chun-Won; Kang, Seung-Youl; Hwang, Chi-Sun; Yu, Byoung-Gon

    2009-12-01

    Poly(vinylidene fluoride trifluoroethylene) and ZnO were employed for nonvolatile memory thin film transistors as ferroelectric gate insulator and oxide semiconducting channel layers, respectively. It was proposed that the thickness of the ZnO layer be carefully controlled for realizing the lower programming voltage, because the serially connected capacitor by the formation of a fully depleted ZnO channel had a critical effect on the off programming voltage. The fabricated memory transistor with Al/P(VDF-TrFE) (80 nm)/Al2O3 (4 nm)/ZnO (5 nm) exhibits encouraging behaviour such as a memory window of 3.8 V at the gate voltage of -10 to 12 V, and 107 on/off ratio, and a gate leakage current of 10-11 A.

  12. Scanning gate study of organic thin-film field-effect transistor

    NASA Astrophysics Data System (ADS)

    Aoki, N.; Sudou, K.; Matsusaki, K.; Okamoto, K.; Ochiai, Y.

    2008-03-01

    Scanning gate microscopy (SGM) has been applied for a study of organic thin-film field effect transistor (OFET). In contrast to one-dimensional nano-material such a carbon nanonube or nano-structure such a quantum point contact, visualization a transport characteristic of OFET channel is basically rather difficult since the channel width is much larger than the size of the SGM tip. Nevertheless, Schottky barriers are successfully visualized at the boundary between the metal electrodes and the OFET channel at ambient atmosphere.

  13. Note: The design of thin gap chamber simulation signal source based on field programmable gate array

    SciTech Connect

    Hu, Kun; Wang, Xu; Li, Feng; Jin, Ge; Lu, Houbing; Liang, Futian

    2015-01-15

    The Thin Gap Chamber (TGC) is an important part of ATLAS detector and LHC accelerator. Targeting the feature of the output signal of TGC detector, we have designed a simulation signal source. The core of the design is based on field programmable gate array, randomly outputting 256-channel simulation signals. The signal is generated by true random number generator. The source of randomness originates from the timing jitter in ring oscillators. The experimental results show that the random number is uniform in histogram, and the whole system has high reliability.

  14. A control system based on field programmable gate array for papermaking sewage treatment

    NASA Astrophysics Data System (ADS)

    Zhang, Zi Sheng; Xie, Chang; Qing Xiong, Yan; Liu, Zhi Qiang; Li, Qing

    2013-03-01

    A sewage treatment control system is designed to improve the efficiency of papermaking wastewater treatment system. The automation control system is based on Field Programmable Gate Array (FPGA), coded with Very-High-Speed Integrate Circuit Hardware Description Language (VHDL), compiled and simulated with Quartus. In order to ensure the stability of the data used in FPGA, the data is collected through temperature sensors, water level sensor and online PH measurement system. The automatic control system is more sensitive, and both the treatment efficiency and processing power are increased. This work provides a new method for sewage treatment control.

  15. Reprogrammable field programmable gate array with integrated system for mitigating effects of single event upsets

    NASA Technical Reports Server (NTRS)

    Ng, Tak-kwong (Inventor); Herath, Jeffrey A. (Inventor)

    2010-01-01

    An integrated system mitigates the effects of a single event upset (SEU) on a reprogrammable field programmable gate array (RFPGA). The system includes (i) a RFPGA having an internal configuration memory, and (ii) a memory for storing a configuration associated with the RFPGA. Logic circuitry programmed into the RFPGA and coupled to the memory reloads a portion of the configuration from the memory into the RFPGA's internal configuration memory at predetermined times. Additional SEU mitigation can be provided by logic circuitry on the RFPGA that monitors and maintains synchronized operation of the RFPGA's digital clock managers.

  16. Hardware implementation of N-LUT method using field programmable gate array technology

    NASA Astrophysics Data System (ADS)

    Kwon, Do-woo; Kim, Seung-Cheol; Kim, Eun-Soo

    2011-02-01

    Hardware implementation for holographic 3D display application is researched by many researchers. Therefore, in this paper, we propose the hardware implementation method for novel look-up table (N-LUT) method using Field Programmable Gate Array (FPGA) technology. In the proposed method, calculation process is divided by some segment block for fast parallel processing of calculation of N-LUT method. That is, by using parallel processing by use of some segmented block based on FPGA technology, calculation speed of CGH can be increased

  17. Field programmable gate array-assigned complex-valued computation and its limits

    SciTech Connect

    Bernard-Schwarz, Maria; Zwick, Wolfgang; Klier, Jochen; Wenzel, Lothar; Gröschl, Martin

    2014-09-15

    We discuss how leveraging Field Programmable Gate Array (FPGA) technology as part of a high performance computing platform reduces latency to meet the demanding real time constraints of a quantum optics simulation. Implementations of complex-valued operations using fixed point numeric on a Virtex-5 FPGA compare favorably to more conventional solutions on a central processing unit. Our investigation explores the performance of multiple fixed point options along with a traditional 64 bits floating point version. With this information, the lowest execution times can be estimated. Relative error is examined to ensure simulation accuracy is maintained.

  18. Media processing with field-programmable gate arrays on a microprocessor's local bus

    NASA Astrophysics Data System (ADS)

    Bove, V. Michael, Jr.; Lee, Mark; Liu, Yuan-Min; McEniry, Christopher; Nwodoh, Thomas A.; Watlington, John A.

    1998-12-01

    The Chidi system is a PCI-bus media processor card which performs its processing tasks on a large field-programmable gate array (Altera 10K100) in conjunction with a general purpose CPU (PowerPC 604e). Special address-generation and buffering logic (also implemented on FPGAs) allows the reconfigurable processor to share a local bus with the CPU, turning burst accesses to memory into continuous streams and converting between the memory's 64-bit words and the media data types. In this paper we present the design requirements for the Chidi system, describe the hardware architecture, and discuss the software model for its use in media processing.

  19. Flexible MoS2 Field-Effect Transistors for Gate-Tunable Piezoresistive Strain Sensors.

    PubMed

    Tsai, Meng-Yen; Tarasov, Alexey; Hesabi, Zohreh R; Taghinejad, Hossein; Campbell, Philip M; Joiner, Corey A; Adibi, Ali; Vogel, Eric M

    2015-06-17

    Atomically thin molybdenum disulfide (MoS2) is a promising two-dimensional semiconductor for high-performance flexible electronics, sensors, transducers, and energy conversion. Here, piezoresistive strain sensing with flexible MoS2 field-effect transistors (FETs) made from highly uniform large-area films is demonstrated. The origin of the piezoresistivity in MoS2 is the strain-induced band gap change, which is confirmed by optical reflection spectroscopy. In addition, the sensitivity to strain can be tuned by more than 1 order of magnitude by adjusting the Fermi level via gate biasing. PMID:26010011

  20. Ferroelectric gate tunnel field-effect transistors with low-power steep turn-on

    NASA Astrophysics Data System (ADS)

    Lee, M. H.; Wei, Y.-T.; Lin, J.-C.; Chen, C.-W.; Tu, W.-H.; Tang, M.

    2014-10-01

    Using a ferroelectric PbZrTiO3 gate stack, the range of the steep subthreshold swing in tunnel field-effect transistors was extended by 3.5 orders of magnitude demonstrating an improvement in the swing (by approximately double the slope). The drain conductance (gd) shows only 16% enhancement with large V DS (˜-1.5V) indicates internal voltage amplification with ferroelectric negative capacitance effect beneficial to small lateral drain-source bias voltages (-0.1 V). The concept of coupling the ferroelectric polarization is proposed. The power consumption is also discussed in low-power applications of steep subthreshold slope devices.

  1. Hardware Implementation of a Lossless Image Compression Algorithm Using a Field Programmable Gate Array

    NASA Astrophysics Data System (ADS)

    Klimesh, M.; Stanton, V.; Watola, D.

    2000-10-01

    We describe a hardware implementation of a state-of-the-art lossless image compression algorithm. The algorithm is based on the LOCO-I (low complexity lossless compression for images) algorithm developed by Weinberger, Seroussi, and Sapiro, with modifications to lower the implementation complexity. In this setup, the compression itself is performed entirely in hardware using a field programmable gate array and a small amount of random access memory. The compression speed achieved is 1.33 Mpixels/second. Our algorithm yields about 15 percent better compression than the Rice algorithm.

  2. Design and test of field programmable gate arrays in space applications

    NASA Technical Reports Server (NTRS)

    Mckerracher, Priscilla L.; Cain, Russel P.; Barnett, Jon C.; Green, William S.; Kinnison, James D.

    1992-01-01

    Field Programmable Gate Arrays (FPGAU's) offer substantial benefits in terms of flexibility and design integration. In addition to qualifying this device for space applications by establishing its reliability and evaluating its sensitivity to radiation, screening the programmed devices with Automatic Test Equipment (ATE) and functional burn-in presents an interesting challenge. This paper presents a review of the design, qualification, and screening cycle employed for FPGA designs in a space program, and demonstrates the need for close interaction between design and test engineers.

  3. A new method to invert top-gate organic field-effect transistors for Kelvin probe investigations

    NASA Astrophysics Data System (ADS)

    Kehrer, L. A.; Feldmeier, E. J.; Siol, C.; Walker, D.; Melzer, C.; von Seggern, H.

    2013-08-01

    In this contribution, we present a technique which allows for the investigation of the local channel potentials of a poly(3-hexylthiophene) (P3HT)-based top-gate field-effect transistor. Usually it is impossible to measure the channel potentials of a top-gate transistor with a Kelvin probe force microscope (KPFM) due to the electrical shielding of the top-gate or the weak capacitive coupling of the tip through the thick substrate to the channel. However, by depositing the entire device on a water solvable polyvinyl alcohol layer, devices can be completely detached from the substrate, creating a free-standing functioning organic field-effect transistor (OFET). After detaching, it is possible to laminate the inverted device on another substrate. This method grants access to the usually hidden channel of the top-gate OFET, and therefore KPFM measurements can be performed.

  4. Fabrication of a liquid-gated enzyme field effect device for sensitive glucose detection.

    PubMed

    Fathollahzadeh, M; Hosseini, M; Haghighi, B; Kolahdouz, M; Fathipour, M

    2016-06-14

    This study presents fabrication of a liquid-gated enzyme field effect device and its implementation as a glucose biosensor. The device consisted of four electrodes on a glass substrate with a channel functionalized by carboxylated multi-walled carbon nanotubes-polyaniline nanocomposite (MWCNTCOOH/PAn) and glucose oxidase. The resistance of functionalized channel increased with increasing the concentration of glucose when an electric field was applied to the liquid gate. The most effective and stable performance was obtained at the applied electric field of 100 mV. The device resistance, R, exhibited a linear relationship with the logarithm of glucose concentration in the range between 0.005 and 500 mM glucose. The detection limit (S/N = 3) for glucose was about 0.5 μM. Large effective area and good conductivity properties of MWCNTCOOH/PAn nanocomposite were the key features of the fabricated sensitive and stable glucose biosensor. PMID:27181649

  5. Numerical Computation of Electric Field and Potential Along Silicone Rubber Insulators Under Contaminated and Dry Band Conditions

    NASA Astrophysics Data System (ADS)

    Arshad; Nekahi, A.; McMeekin, S. G.; Farzaneh, M.

    2016-09-01

    Electrical field distribution along the insulator surface is considered one of the important parameters for the performance evaluation of outdoor insulators. In this paper numerical simulations were carried out to investigate the electric field and potential distribution along silicone rubber insulators under various polluted and dry band conditions. Simulations were performed using commercially available simulation package Comsol Multiphysics based on the finite element method. Various pollution severity levels were simulated by changing the conductivity of pollution layer. Dry bands of 2 cm width were inserted at the high voltage end, ground end, middle part, shed, sheath, and at the junction of shed and sheath to investigate the effect of dry band location and width on electric field and potential distribution. Partial pollution conditions were simulated by applying pollution layer on the top and bottom surface respectively. It was observed from the simulation results that electric field intensity was higher at the metal electrode ends and at the junction of dry bands. Simulation results showed that potential distribution is nonlinear in the case of clean and partially polluted insulator and linear for uniform pollution layer. Dry band formation effect both potential and electric field distribution. Power dissipated along the insulator surface and the resultant heat generation was also studied. The results of this study could be useful in the selection of polymeric insulators for contaminated environments.

  6. Field Evaluation of Highly Insulating Windows in the Lab Homes: Winter Experiment

    SciTech Connect

    Parker, Graham B.; Widder, Sarah H.; Bauman, Nathan N.

    2012-06-01

    This field evaluation of highly insulating windows was undertaken in a matched pair of 'Lab Homes' located on the Pacific Northwest National Laboratory (PNNL) campus during the 2012 winter heating season. Improving the insulation and solar heat gain characteristics of a home's windows has the potential to significantly improve the home's building envelope and overall thermal performance by reducing heat loss (in the winter), and cooling loss and solar heat gain (in the summer) through the windows. A high quality installation and/or window retrofit will also minimize or reduce air leakage through the window cavity and thus also contribute to reduced heat loss in the winter and cooling loss in the summer. These improvements all contribute to decreasing overall annual home energy use. Occupant comfort (non-quantifiable) can also be increased by minimizing or eliminating the cold 'draft' (temperature) many residents experience at or near window surfaces that are at a noticeably lower temperature than the room air temperature. Lastly, although not measured in this experiment, highly insulating windows (triple-pane in this experiment) also have the potential to significantly reduce the noise transmittance through windows compared to standard double-pane windows. The metered data taken in the Lab Homes and data analysis presented here represent 70 days of data taken during the 2012 heating season. As such, the savings from highly insulating windows in the experimental home (Lab Home B) compared to the standard double-pane clear glass windows in the baseline home (Lab Home A) are only a portion of the energy savings expected from a year-long experiment that would include a cooling season. The cooling season experiment will take place in the homes in the summer of 2012, and results of that experiment will be reported in a subsequent report available to all stakeholders.

  7. Poly(methyl methacrylate) as a self-assembled gate dielectric for graphene field-effect transistors

    SciTech Connect

    Sanne, A.; Movva, H. C. P.; Kang, S.; McClellan, C.; Corbet, C. M.; Banerjee, S. K.

    2014-02-24

    We investigate poly(methyl methacrylate) (PMMA) as a low thermal budget organic gate dielectric for graphene field effect-transistors (GFETs) based on a simple process flow. We show that high temperature baking steps above the glass transition temperature (∼130 °C) can leave a self-assembled, thin PMMA film on graphene, where we get a gate dielectric almost for “free” without additional atomic layer deposition type steps. Electrical characterization of GFETs with PMMA as a gate dielectric yields a dielectric constant of k = 3.0. GFETs with thinner PMMA dielectrics have a lower dielectric constant due to decreased polarization arising from neutralization of dipoles and charged carriers as baking temperatures increase. The leakage through PMMA gate dielectric increases with decreasing dielectric thickness and increasing electric field. Unlike conventional high-k gate dielectrics, such low-k organic gate dielectrics are potentially attractive for devices such as the proposed Bilayer pseudoSpin Field-Effect Transistor or flexible high speed graphene electronics.

  8. G4-FETs as Universal and Programmable Logic Gates

    NASA Technical Reports Server (NTRS)

    Johnson, Travis; Fijany, Amir; Mojarradi, Mohammad; Vatan, Farrokh; Toomarian, Nikzad; Kolawa, Elizabeth; Cristoloveanu, Sorin; Blalock, Benjamin

    2007-01-01

    An analysis of a patented generic silicon- on-insulator (SOI) electronic device called a G4-FET has revealed that the device could be designed to function as a universal and programmable logic gate. The universality and programmability could be exploited to design logic circuits containing fewer discrete components than are required for conventional transistor-based circuits performing the same logic functions. A G4-FET is a combination of a junction field-effect transistor (JFET) and a metal oxide/semiconductor field-effect transistor (MOSFET) superimposed in a single silicon island and can therefore be regarded as two transistors sharing the same body. A G4-FET can also be regarded as a single transistor having four gates: two side junction-based gates, a top MOS gate, and a back gate activated by biasing of the SOI substrate. Each of these gates can be used to control the conduction characteristics of the transistor; this possibility creates new options for designing analog, radio-frequency, mixed-signal, and digital circuitry. With proper choice of the specific dimensions for the gates, channels, and ancillary features of the generic G4-FET, the device could be made to function as a three-input, one-output logic gate. As illustrated by the truth table in the top part of the figure, the behavior of this logic gate would be the inverse (the NOT) of that of a majority gate. In other words, the device would function as a NOT-majority gate. By simply adding an inverter, one could obtain a majority gate. In contrast, to construct a majority gate in conventional complementary metal oxide/semiconductor (CMOS) circuitry, one would need four three-input AND gates and a four-input OR gate, altogether containing 32 transistors.

  9. Effect of front and back gates on β-Ga2O3 nano-belt field-effect transistors

    NASA Astrophysics Data System (ADS)

    Ahn, Shihyun; Ren, Fan; Kim, Janghyuk; Oh, Sooyeoun; Kim, Jihyun; Mastro, Michael A.; Pearton, S. J.

    2016-08-01

    Field effect transistors (FETs) using SiO2 and Al2O3 as the gate oxides for the back and front sides, respectively, were fabricated on exfoliated two-dimensional (2D) β-Ga2O3 nano-belts transferred to a SiO2/Si substrate. The mechanical exfoliation and transfer process produced nano-belts with smooth surface morphologies and a uniform low defect density interface with the SiO2/Si substrate. The depletion mode nanobelt transistors exhibited better channel modulation with both front and back gates operational compared to either front or back-gating alone. The maximum transconductance was ˜4.4 mS mm-1 with front and back-gating and ˜3.7 mS mm-1 with front-gating only and a maximum drain source current density of 60 mA mm-1 was achieved at a drain-source voltage of 10 V. The FETs had on/off ratios of ˜105 at 25 °C with gate-source current densities of ˜2 × 10-3 mA mm-1 at a gate voltage of -30 V. The device characteristics were stable over more than a month for storage in air ambient and the results show the potential of 2D β-Ga2O3 for power nanoelectronics.

  10. Streamer initiation and propagation in insulating oil in weakly non-uniform fields under impulse conditions

    SciTech Connect

    Badent, R.; Kist, K.; Schwab, A.J.

    1996-12-31

    This paper deals with the investigation of prebreakdown phenomenon in insulating oil in weakly non-uniform fields of rod-plane geometries with gaps up to 100 mm under impulse voltages of both polarities up to 700 kV. As with the point-plane configuration, the rod-plane geometry shows a decrease of the time to breakdown with increasing voltage rate-of-rise. At a specific rate, a significantly shorter breakdown time is observed both for positive and negative polarities. Beyond this discontinuity range breakdown time decreases again but with lower rates.

  11. Local-field corrections to surface and interface core-level shifts in insulators

    SciTech Connect

    Rotenberg, E. ); Olmstead, M.A. )

    1992-11-15

    We present a model for the extra-atomic contributions to core-level shifts in insulating thin films on polarizable substrates. The final-state shift is calculated from the screening-dependent local fields at a photoemitting atom and shown to be comparable to the initial-state Madelung potential shift in polar crystals. For Xe(111) films, our model completely accounts for experimental results. For NaCl(100) and CaF{sub 2}(111) surfaces, we present predictions of surface core-level shifts for simple bulk terminations. We discuss corrections which can be incorporated into our model.

  12. Mobility overestimation due to gated contacts in organic field-effect transistors

    PubMed Central

    Bittle, Emily G.; Basham, James I.; Jackson, Thomas N.; Jurchescu, Oana D.; Gundlach, David J.

    2016-01-01

    Parameters used to describe the electrical properties of organic field-effect transistors, such as mobility and threshold voltage, are commonly extracted from measured current–voltage characteristics and interpreted by using the classical metal oxide–semiconductor field-effect transistor model. However, in recent reports of devices with ultra-high mobility (>40 cm2 V−1 s−1), the device characteristics deviate from this idealized model and show an abrupt turn-on in the drain current when measured as a function of gate voltage. In order to investigate this phenomenon, here we report on single crystal rubrene transistors intentionally fabricated to exhibit an abrupt turn-on. We disentangle the channel properties from the contact resistance by using impedance spectroscopy and show that the current in such devices is governed by a gate bias dependence of the contact resistance. As a result, extracted mobility values from d.c. current–voltage characterization are overestimated by one order of magnitude or more. PMID:26961271

  13. Mobility overestimation due to gated contacts in organic field-effect transistors.

    PubMed

    Bittle, Emily G; Basham, James I; Jackson, Thomas N; Jurchescu, Oana D; Gundlach, David J

    2016-01-01

    Parameters used to describe the electrical properties of organic field-effect transistors, such as mobility and threshold voltage, are commonly extracted from measured current-voltage characteristics and interpreted by using the classical metal oxide-semiconductor field-effect transistor model. However, in recent reports of devices with ultra-high mobility (>40 cm(2) V(-1) s(-1)), the device characteristics deviate from this idealized model and show an abrupt turn-on in the drain current when measured as a function of gate voltage. In order to investigate this phenomenon, here we report on single crystal rubrene transistors intentionally fabricated to exhibit an abrupt turn-on. We disentangle the channel properties from the contact resistance by using impedance spectroscopy and show that the current in such devices is governed by a gate bias dependence of the contact resistance. As a result, extracted mobility values from d.c. current-voltage characterization are overestimated by one order of magnitude or more. PMID:26961271

  14. Mobility overestimation due to gated contacts in organic field-effect transistors

    NASA Astrophysics Data System (ADS)

    Bittle, Emily G.; Basham, James I.; Jackson, Thomas N.; Jurchescu, Oana D.; Gundlach, David J.

    2016-03-01

    Parameters used to describe the electrical properties of organic field-effect transistors, such as mobility and threshold voltage, are commonly extracted from measured current-voltage characteristics and interpreted by using the classical metal oxide-semiconductor field-effect transistor model. However, in recent reports of devices with ultra-high mobility (>40 cm2 V-1 s-1), the device characteristics deviate from this idealized model and show an abrupt turn-on in the drain current when measured as a function of gate voltage. In order to investigate this phenomenon, here we report on single crystal rubrene transistors intentionally fabricated to exhibit an abrupt turn-on. We disentangle the channel properties from the contact resistance by using impedance spectroscopy and show that the current in such devices is governed by a gate bias dependence of the contact resistance. As a result, extracted mobility values from d.c. current-voltage characterization are overestimated by one order of magnitude or more.

  15. Mean-field dynamics of the superfluid-insulator phase transition in a gas of ultracold atoms

    NASA Astrophysics Data System (ADS)

    Zakrzewski, Jakub

    2005-04-01

    A large-scale dynamical simulation of the superfluid-Mott-insulator transition in a gas of ultracold atoms placed in an optical lattice is performed using the time-dependent Gutzwiller mean-field approach. This approximate treatment allows us to take into account most of the details of the recent experiment [Greiner , Nature (London) 415, 39 (2002)] where by changing the depth of the lattice potential an adiabatic transition from a superfluid to a Mott insulator state has been reported. Our simulations reveal a significant excitation of the system with a transition to insulator in restricted regions of the trap only.

  16. Bosonic Magnetic Field Driven Superconductor-Insulator Transitions in Amorphous Nano-honeycomb Films

    NASA Astrophysics Data System (ADS)

    Stewart, M. D., Jr.; Yin, Aijun; Xu, J. M.; Valles, James M., Jr.

    2008-03-01

    We have observed multiple magnetic field driven superconductor-insulator transitions (SIT) in amorphous Bi films perforated with a nano-honeycomb (NHC) array of holes. The magneto-resistance across the SITs is periodic, with a period H=HM=h/2eS, where S is the area of a unit cell of holes. These transitions are, therefore, boson dominated. In constant field the temperature dependence of the resistance can be parameterized by R(T)=R0(H)(T0(H)/T) on both sides of the transition so that the evolution between the superconducting and insulating states is controlled by the vanishing of T0->0. We compare these data to the thickness driven transition in NHC films and the field driven transitions in unpatterned Bi films, other materials, and Josephson junction arrays. Our results suggest a structural source for similar behavior found in some materials and that despite the clear bosonic nature of the SITs, quasiparticle degrees of freedom likely also play an important part in the evolution of the SIT.

  17. Power frequency electric and magnetic fields from a 230 kV gas-insulated substation

    SciTech Connect

    Wong, P.S.; Rind, T.M. ); Harvey, S.M.; Scheer, R.R. . Research Div.)

    1994-07-01

    Gas-insulated substations (GIS), owing to their compact nature, offer an attractive alternative to conventional substations where space is limited, such as in urban areas. Consequently, it is important to address the issue of environmental conditions in and around the GIS. This paper presents the results of a survey of power-frequency electric and magnetic fields in and around a 230 kV/28 kV GIS. The survey was designed to cover the electric and magnetic fields from the substation equipment and from the power lines and cables surrounding the substation. It also includes a determination of the shielding effect of the GIS bus sheath. The information provided should allow the prediction of electric and magnetic field levels from other GIS of similar design.

  18. Quantum capacitance of an ultrathin topological insulator film in a magnetic field

    PubMed Central

    Tahir, M.; Sabeeh, K.; Schwingenschlögl, U.

    2013-01-01

    We present a theoretical study of the quantum magnetocapacitance of an ultrathin topological insulator film in an external magnetic field. The study is undertaken to investigate the interplay of the Zeeman interaction with the hybridization between the upper and lower surfaces of the thin film. Determining the density of states, we find that the electron-hole symmetry is broken when the Zeeman and hybridization energies are varied relative to each other. This leads to a change in the character of the magnetocapacitance at the charge neutrality point. We further show that in the presence of both Zeeman interaction and hybridization the magnetocapacitance exhibits beating at low and splitting of the Shubnikov de Haas oscillations at high perpendicular magnetic field. In addition, we address the crossover from perpendicular to parallel magnetic field and find consistency with recent experimental data. PMID:23405275

  19. Dielectric interface-dependent spatial charge distribution in ambipolar polymer semiconductors embedded in dual-gate field-effect transistors

    NASA Astrophysics Data System (ADS)

    Lee, Jiyoul; Roelofs, W. S. Christian; Janssen, Rene A. J.; Gelinck, Gerwin H.

    2016-07-01

    The spatial charge distribution in diketopyrrolopyrrole-containing ambipolar polymeric semiconductors embedded in dual-gate field-effect transistors (DGFETs) was investigated. The DGFETs have identical active channel layers but two different channel/gate interfaces, with a CYTOP™ organic dielectric layer for the top-gate and an octadecyltrichlorosilane (ODTS) self-assembled monolayer-treated inorganic SiO2 dielectric for the bottom-gate, respectively. Temperature-dependent transfer measurements of the DGFETs were conducted to examine the charge transport at each interface. By fitting the temperature-dependent measurement results to the modified Vissenberg-Matters model, it can be inferred that the top-channel interfacing with the fluorinated organic dielectric layers has confined charge transport to two-dimensions, whereas the bottom-channel interfacing with the ODTS-treated SiO2 dielectric layers has three-dimensional charge transport.

  20. Realization of a quantum gate using gravitational search algorithm by perturbing three-dimensional harmonic oscillator with an electromagnetic field

    NASA Astrophysics Data System (ADS)

    Sharma, Navneet; Rawat, Tarun Kumar; Parthasarathy, Harish; Gautam, Kumar

    2016-06-01

    The aim of this paper is to design a current source obtained as a representation of p information symbols \\{I_k\\} so that the electromagnetic (EM) field generated interacts with a quantum atomic system producing after a fixed duration T a unitary gate U( T) that is as close as possible to a given unitary gate U_g. The design procedure involves calculating the EM field produced by \\{I_k\\} and hence the perturbing Hamiltonian produced by \\{I_k\\} finally resulting in the evolution operator produced by \\{I_k\\} up to cubic order based on the Dyson series expansion. The gate error energy is thus obtained as a cubic polynomial in \\{I_k\\} which is minimized using gravitational search algorithm. The signal to noise ratio (SNR) in the designed gate is higher as compared to that using quadratic Dyson series expansion. The SNR is calculated as the ratio of the Frobenius norm square of the desired gate to that of the desired gate error.

  1. Realization of a quantum gate using gravitational search algorithm by perturbing three-dimensional harmonic oscillator with an electromagnetic field

    NASA Astrophysics Data System (ADS)

    Sharma, Navneet; Rawat, Tarun Kumar; Parthasarathy, Harish; Gautam, Kumar

    2016-03-01

    The aim of this paper is to design a current source obtained as a representation of p information symbols {I_k} so that the electromagnetic (EM) field generated interacts with a quantum atomic system producing after a fixed duration T a unitary gate U(T) that is as close as possible to a given unitary gate U_g . The design procedure involves calculating the EM field produced by {I_k} and hence the perturbing Hamiltonian produced by {I_k} finally resulting in the evolution operator produced by {I_k} up to cubic order based on the Dyson series expansion. The gate error energy is thus obtained as a cubic polynomial in {I_k} which is minimized using gravitational search algorithm. The signal to noise ratio (SNR) in the designed gate is higher as compared to that using quadratic Dyson series expansion. The SNR is calculated as the ratio of the Frobenius norm square of the desired gate to that of the desired gate error.

  2. Thin film three-dimensional topological insulator metal-oxide-semiconductor field-effect-transistors: A candidate for sub-10 nm devices

    SciTech Connect

    Akhavan, N. D. Jolley, G.; Umana-Membreno, G. A.; Antoszewski, J.; Faraone, L.

    2014-08-28

    Three-dimensional (3D) topological insulators (TI) are a new state of quantum matter in which surface states reside in the bulk insulating energy bandgap and are protected by time-reversal symmetry. It is possible to create an energy bandgap as a consequence of the interaction between the conduction band and valence band surface states from the opposite surfaces of a TI thin film, and the width of the bandgap can be controlled by the thin film thickness. The formation of an energy bandgap raises the possibility of thin-film TI-based metal-oxide-semiconductor field-effect-transistors (MOSFETs). In this paper, we explore the performance of MOSFETs based on thin film 3D-TI structures by employing quantum ballistic transport simulations using the effective continuous Hamiltonian with fitting parameters extracted from ab-initio calculations. We demonstrate that thin film transistors based on a 3D-TI structure provide similar electrical characteristics compared to a Si-MOSFET for gate lengths down to 10 nm. Thus, such a device can be a potential candidate to replace Si-based MOSFETs in the sub-10 nm regime.

  3. Electrically tuned magnetic order and magnetoresistance in a topological insulator.

    PubMed

    Zhang, Zuocheng; Feng, Xiao; Guo, Minghua; Li, Kang; Zhang, Jinsong; Ou, Yunbo; Feng, Yang; Wang, Lili; Chen, Xi; He, Ke; Ma, Xucun; Xue, Qikun; Wang, Yayu

    2014-01-01

    The interplay between topological protection and broken time reversal symmetry in topological insulators may lead to highly unconventional magnetoresistance behaviour that can find unique applications in magnetic sensing and data storage. However, the magnetoresistance of topological insulators with spontaneously broken time reversal symmetry is still poorly understood. In this work, we investigate the transport properties of a ferromagnetic topological insulator thin film fabricated into a field effect transistor device. We observe a complex evolution of gate-tuned magnetoresistance, which is positive when the Fermi level lies close to the Dirac point but becomes negative at higher energies. This trend is opposite to that expected from the Berry phase picture, but is intimately correlated with the gate-tuned magnetic order. The underlying physics is the competition between the topology-induced weak antilocalization and magnetism-induced negative magnetoresistance. The simultaneous electrical control of magnetic order and magnetoresistance facilitates future topological insulator based spintronic devices. PMID:25222696

  4. High-performance reconfigurable coincidence counting unit based on a field programmable gate array.

    PubMed

    Park, Byung Kwon; Kim, Yong-Su; Kwon, Osung; Han, Sang-Wook; Moon, Sung

    2015-05-20

    We present a high-performance reconfigurable coincidence counting unit (CCU) using a low-end field programmable gate array (FPGA) and peripheral circuits. Because of the flexibility guaranteed by the FPGA program, we can easily change system parameters, such as internal input delays, coincidence configurations, and the coincidence time window. In spite of a low-cost implementation, the proposed CCU architecture outperforms previous ones in many aspects: it has 8 logic inputs and 4 coincidence outputs that can measure up to eight-fold coincidences. The minimum coincidence time window and the maximum input frequency are 0.47 ns and 163 MHz, respectively. The CCU will be useful in various experimental research areas, including the field of quantum optics and quantum information. PMID:26192507

  5. Quantum logic gates from time-dependent global magnetic field in a system with constant exchange

    SciTech Connect

    Nenashev, A. V. Dvurechenskii, A. V.; Zinovieva, A. F.; Gornov, A. Yu.; Zarodnyuk, T. S.

    2015-03-21

    We propose a method that implements a universal set of one- and two-quantum-bit gates for quantum computation in a system of coupled electron pairs with constant non-diagonal exchange interaction. In our proposal, suppression of the exchange interaction is performed by the continual repetition of single-spin rotations. A small g-factor difference between the electrons allows for addressing qubits and avoiding strong magnetic field pulses. Numerical experiments were performed to show that, to implement the one- and two-qubit operations, it is sufficient to change the strength of the magnetic field by a few Gauss. This introduces one and then the other electron in a resonance. To determine the evolution of the two-qubit system, we use the algorithms of optimal control theory.

  6. Nanocrystalline cellulose applied simultaneously as the gate dielectric and the substrate in flexible field effect transistors

    NASA Astrophysics Data System (ADS)

    Gaspar, D.; Fernandes, S. N.; de Oliveira, A. G.; Fernandes, J. G.; Grey, P.; Pontes, R. V.; Pereira, L.; Martins, R.; Godinho, M. H.; Fortunato, E.

    2014-03-01

    Cotton-based nanocrystalline cellulose (NCC), also known as nanopaper, one of the major sources of renewable materials, is a promising substrate and component for producing low cost fully recyclable flexible paper electronic devices and systems due to its properties (lightweight, stiffness, non-toxicity, transparency, low thermal expansion, gas impermeability and improved mechanical properties). Here, we have demonstrated for the first time a thin transparent nanopaper-based field effect transistor (FET) where NCC is simultaneously used as the substrate and as the gate dielectric layer in an ‘interstrate’ structure, since the device is built on both sides of the NCC films; while the active channel layer is based on oxide amorphous semiconductors, the gate electrode is based on a transparent conductive oxide. Such hybrid FETs present excellent operating characteristics such as high channel saturation mobility (>7 cm2 V -1 s-1), drain-source current on/off modulation ratio higher than 105, enhancement n-type operation and subthreshold gate voltage swing of 2.11 V/decade. The NCC film FET characteristics have been measured in air ambient conditions and present good stability, after two weeks of being processed, without any type of encapsulation or passivation layer. The results obtained are comparable to ones produced for conventional cellulose paper, marking this out as a promising approach for attaining high-performance disposable electronics such as paper displays, smart labels, smart packaging, RFID (radio-frequency identification) and point-of-care systems for self-analysis in bioscience applications, among others.

  7. Touch sensors based on planar liquid crystal-gated-organic field-effect transistors

    SciTech Connect

    Seo, Jooyeok; Lee, Chulyeon; Han, Hyemi; Lee, Sooyong; Nam, Sungho; Kim, Youngkyoo; Kim, Hwajeong; Lee, Joon-Hyung; Park, Soo-Young; Kang, Inn-Kyu

    2014-09-15

    We report a tactile touch sensor based on a planar liquid crystal-gated-organic field-effect transistor (LC-g-OFET) structure. The LC-g-OFET touch sensors were fabricated by forming the 10 μm thick LC layer (4-cyano-4{sup ′}-pentylbiphenyl - 5CB) on top of the 50 nm thick channel layer (poly(3-hexylthiophene) - P3HT) that is coated on the in-plane aligned drain/source/gate electrodes (indium-tin oxide - ITO). As an external physical stimulation to examine the tactile touch performance, a weak nitrogen flow (83.3 μl/s) was employed to stimulate the LC layer of the touch device. The LC-g-OFET device exhibited p-type transistor characteristics with a hole mobility of 1.5 cm{sup 2}/Vs, but no sensing current by the nitrogen flow touch was measured at sufficiently high drain (V{sub D}) and gate (V{sub G}) voltages. However, a clear sensing current signal was detected at lower voltages, which was quite sensitive to the combination of V{sub D} and V{sub G}. The best voltage combination was V{sub D} = −0.2 V and V{sub G} = −1 V for the highest ratio of signal currents to base currents (i.e., signal-to-noise ratio). The change in the LC alignment upon the nitrogen flow touch was assigned as the mechanism for the present LC-g-OFET touch sensors.

  8. Nanocrystalline cellulose applied simultaneously as the gate dielectric and the substrate in flexible field effect transistors.

    PubMed

    Gaspar, D; Fernandes, S N; de Oliveira, A G; Fernandes, J G; Grey, P; Pontes, R V; Pereira, L; Martins, R; Godinho, M H; Fortunato, E

    2014-03-01

    Cotton-based nanocrystalline cellulose (NCC), also known as nanopaper, one of the major sources of renewable materials, is a promising substrate and component for producing low cost fully recyclable flexible paper electronic devices and systems due to its properties (lightweight, stiffness, non-toxicity, transparency, low thermal expansion, gas impermeability and improved mechanical properties).Here, we have demonstrated for the first time a thin transparent nanopaper-based field effect transistor (FET) where NCC is simultaneously used as the substrate and as the gate dielectric layer in an 'interstrate' structure, since the device is built on both sides of the NCC films; while the active channel layer is based on oxide amorphous semiconductors, the gate electrode is based on a transparent conductive oxide.Such hybrid FETs present excellent operating characteristics such as high channel saturation mobility (>7 cm(2) V (-1) s(-1)), drain-source current on/off modulation ratio higher than 10(5), enhancement n-type operation and subthreshold gate voltage swing of 2.11 V/decade. The NCC film FET characteristics have been measured in air ambient conditions and present good stability, after two weeks of being processed, without any type of encapsulation or passivation layer. The results obtained are comparable to ones produced for conventional cellulose paper, marking this out as a promising approach for attaining high-performance disposable electronics such as paper displays, smart labels, smart packaging, RFID (radio-frequency identification) and point-of-care systems for self-analysis in bioscience applications, among others. PMID:24522012

  9. High-Performance Wrap-Gated InGaAs Nanowire Field-Effect Transistors with Sputtered Dielectrics

    PubMed Central

    Shen, Li-Fan; Yip, SenPo; Yang, Zai-xing; Fang, Ming; Hung, TakFu; Pun, Edwin Y.B.; Ho, Johnny C.

    2015-01-01

    Although wrap-gated nanowire field-effect-transistors (NWFETs) have been explored as an ideal electronic device geometry for low-power and high-frequency applications, further performance enhancement and practical implementation are still suffering from electron scattering on nanowire surface/interface traps between the nanowire channel and gate dielectric as well as the complicated device fabrication scheme. Here, we report the development of high-performance wrap-gated InGaAs NWFETs using conventional sputtered Al2O3 layers as gate dielectrics, instead of the typically employed atomic layer deposited counterparts. Importantly, the surface chemical passivation of NW channels performed right before the dielectric deposition is found to significantly alleviate plasma induced defect traps on the NW channel. Utilizing this passivation, the wrap-gated device exhibits superior electrical performances: a high ION/IOFF ratio of ~2 × 106, an extremely low sub-threshold slope of 80 mV/decade and a peak field-effect electron mobility of ~1600 cm2/(Vs) at VDS = 0.1 V at room temperature, in which these values are even better than the ones of state-of-the-art NWFETs reported so far. By combining sputtering and pre-deposition chemical passivation to achieve high-quality gate dielectrics for wrap-gated NWFETs, the superior gate coupling and electrical performances have been achieved, confirming the effectiveness of our hybrid approach for future advanced electronic devices. PMID:26607169

  10. The understanding on the evolution of stress-induced gate leakage in high-k dielectric metal-oxide-field-effect transistor by random-telegraph-noise measurement

    NASA Astrophysics Data System (ADS)

    Hsieh, E. R.; Chung, Steve S.

    2015-12-01

    The evolution of gate-current leakage path has been observed and depicted by RTN signals on metal-oxide-silicon field effect transistor with high-k gate dielectric. An experimental method based on gate-current random telegraph noise (Ig-RTN) technique was developed to observe the formation of gate-leakage path for the device under certain electrical stress, such as Bias Temperature Instability. The results show that the evolution of gate-current path consists of three stages. In the beginning, only direct-tunnelling gate current and discrete traps inducing Ig-RTN are observed; in the middle stage, interaction between traps and the percolation paths presents a multi-level gate-current variation, and finally two different patterns of the hard or soft breakdown path can be identified. These observations provide us a better understanding of the gate-leakage and its impact on the device reliability.

  11. Human aquaporin 4 gating dynamics in dc and ac electric fields: A molecular dynamics study

    NASA Astrophysics Data System (ADS)

    Garate, J.-A.; English, Niall J.; MacElroy, J. M. D.

    2011-02-01

    Water self-diffusion within human aquaporin 4 has been studied using molecular dynamics (MD) simulations in the absence and presence of external ac and dc electric fields. The computed diffusive (pd) and osmotic (pf) permeabilities under zero-field conditions are (0.718 ± 0.24) × 10-14 cm3 s-1 and (2.94 ± 0.47) × 10-14 cm3 s-1, respectively; our pf agrees with the experimental value of (1.50 ± 0.6) × 10-14 cm3 s-1. A gating mechanism has been proposed in which side-chain dynamics of residue H201, located in the selectivity filter, play an essential role. In addition, for nonequilibrium MD in external fields, it was found that water dipole orientation within the constriction region of the channel is affected by electric fields (e-fields) and that this governs the permeability. It was also found that the rate of side-chain flipping motion of residue H201 is increased in the presence of e-fields, which influences water conductivity further.

  12. All-Graphene Planar Self-Switching MISFEDs, Metal-Insulator-Semiconductor Field-Effect Diodes

    PubMed Central

    Al-Dirini, Feras; Hossain, Faruque M.; Nirmalathas, Ampalavanapillai; Skafidas, Efstratios

    2014-01-01

    Graphene normally behaves as a semimetal because it lacks a bandgap, but when it is patterned into nanoribbons a bandgap can be introduced. By varying the width of these nanoribbons this band gap can be tuned from semiconducting to metallic. This property allows metallic and semiconducting regions within a single Graphene monolayer, which can be used in realising two-dimensional (2D) planar Metal-Insulator-Semiconductor field effect devices. Based on this concept, we present a new class of nano-scale planar devices named Graphene Self-Switching MISFEDs (Metal-Insulator-Semiconductor Field-Effect Diodes), in which Graphene is used as the metal and the semiconductor concurrently. The presented devices exhibit excellent current-voltage characteristics while occupying an ultra-small area with sub-10 nm dimensions and an ultimate thinness of a single atom. Quantum mechanical simulation results, based on the Extended Huckel method and Nonequilibrium Green's Function Formalism, show that a Graphene Self-Switching MISFED with a channel as short as 5 nm can achieve forward-to-reverse current rectification ratios exceeding 5000. PMID:24496307

  13. α,ω-dihexyl-sexithiophene thin films for solution-gated organic field-effect transistors

    NASA Astrophysics Data System (ADS)

    Schamoni, Hannah; Noever, Simon; Nickel, Bert; Stutzmann, Martin; Garrido, Jose A.

    2016-02-01

    While organic semiconductors are being widely investigated for chemical and biochemical sensing applications, major drawbacks such as the poor device stability and low charge carrier mobility in aqueous electrolytes have not yet been solved to complete satisfaction. In this work, solution-gated organic field-effect transistors (SGOFETs) based on the molecule α,ω-dihexyl-sexithiophene (DH6T) are presented as promising platforms for in-electrolyte sensing. Thin films of DH6T were investigated with regard to the influence of the substrate temperature during deposition on the grain size and structural order. The performance of SGOFETs can be improved by choosing suitable growth parameters that lead to a two-dimensional film morphology and a high degree of structural order. Furthermore, the capability of the SGOFETs to detect changes in the pH or ionic strength of the gate electrolyte is demonstrated and simulated. Finally, excellent transistor stability is confirmed by continuously operating the device over a period of several days, which is a consequence of the low threshold voltage of DH6T-based SGOFETs. Altogether, our results demonstrate the feasibility of high performance and highly stable organic semiconductor devices for chemical or biochemical applications.

  14. Single trap dynamics in electrolyte-gated Si-nanowire field effect transistors

    SciTech Connect

    Pud, S.; Li, J.; Offenhäusser, A.; Vitusevich, S. A.; Gasparyan, F.; Petrychuk, M.

    2014-06-21

    Liquid-gated silicon nanowire (NW) field effect transistors (FETs) are fabricated and their transport and dynamic properties are investigated experimentally and theoretically. Random telegraph signal (RTS) fluctuations were registered in the nanolength channel FETs and used for the experimental and theoretical analysis of transport properties. The drain current and the carrier interaction processes with a single trap are analyzed using a quantum-mechanical evaluation of carrier distribution in the channel and also a classical evaluation. Both approaches are applied to treat the experimental data and to define an appropriate solution for describing the drain current behavior influenced by single trap resulting in RTS fluctuations in the Si NW FETs. It is shown that quantization and tunneling effects explain the behavior of the electron capture time on the single trap. Based on the experimental data, parameters of the single trap were determined. The trap is located at a distance of about 2 nm from the interface Si/SiO{sub 2} and has a repulsive character. The theory of dynamic processes in liquid-gated Si NW FET put forward here is in good agreement with experimental observations of transport in the structures and highlights the importance of quantization in carrier distribution for analyzing dynamic processes in the nanostructures.

  15. Flexible terahertz modulator based on coplanar-gate graphene field-effect transistor structure.

    PubMed

    Liu, Jingbo; Li, Pingjian; Chen, Yuanfu; Song, Xinbo; Mao, Qi; Wu, Yang; Qi, Fei; Zheng, Binjie; He, Jiarui; Yang, Hyunsoo; Wen, Qiye; Zhang, Wanli

    2016-02-15

    The terahertz (THz) modulators, as an essential component of the THz system, have been developed by many efforts until now. However, the development of flexible THz modulators is hindered due to the lack of flexible THz modulating materials. Herein, for the first time to the best of our knowledge, we demonstrated the feasibility of flexible THz modulators based on the coplanar-gate field-effect transistor (FET) structure of ion-gel/graphene/polyethylene terephthalate. The THz transmittance through this THz graphene modulator can be well controlled with a modulation depth up to 22% by tuning the carrier concentration of graphene via electrical gating. Furthermore, because of the integration of high flexibilities of graphene, ion-gel, and polyethylene terephthalate (PET), the proposed THz graphene modulator shows superior flexible performance, where the modulation properties can be maintained almost unchanged, not only under bending deformations, but also before and after bending 1000 times. In addition, due to the unique structure of ion-gel/graphene/PET, the flexible THz graphene modulator has a low insertion loss (1.2 dB). Therefore, this Letter is expected to be beneficial for the potential applications, ranging from the traditional compact THz system to a new flexible THz technology. PMID:26872196

  16. Metal-insulator-transition in SrTiO3 induced by argon bombardment combined with field effect

    SciTech Connect

    Xu, Jie; Zhu, Zhengyong; Zhao, Hengliang; Luo, Zhijiong

    2014-12-15

    By fabricating the Field-Effect-Transistors on argon bombardment SrTiO3 substrates, not only we have achieved one of the best mobility for Field-Effect-Transistors fabricated on SrTiO3, but also realized strong field induced Metal-Insulator-Transition. The critical sheet resistance for the Metal-Insulator-Transition is only 1/7 of the value obtained in the former experiments, indicating a different mechanism. Further study shows that the Metal-Insulator-Transition can be attributed to the oxygen vacancies formed after the bombardment becoming the electron donor under the electric field modulation, increasing SrTiO3 surface electron density and transforming the substrate into metallic state.

  17. First-Principle Perturbative Computation of Phonon Properties of Insulators in Finite Electric Fields

    NASA Astrophysics Data System (ADS)

    Wang, Xinjie

    2005-03-01

    The methods of density-functional perturbation theory have been shown to provide a powerful tool for realistic calculations of lattice-vibrational, dielectric, elastic, and other response properties of crystals.ootnotetextS. Baroni et al., Rev. Mod. Phys. 73, 515 (2001). Recently, a total-energy method for insulators in nonzero electric fields was proposed.ootnotetextI. Souza, J. 'Iñiguez, and D. Vanderbilt, Phys. Rev. Lett. 89, 117602 (2002). However, the perturbative computation of phonon properties under a dc bias field has not previously been addressed. Here, we start from a variational total-energy functional with a field coupling term that represents the effect of the electric field on the crystal. The linear response of the field-polarized Bloch functions is obtained by minimizing the second-order derivative of the total-energy functional. Due to the presence of the electric field, the field-polarized Bloch functions at each k-point in the Brillouin zone are weakly coupled to those at the neighboring k-points. We implement the method in the ABINIT code and perform illustrative calculations of the phonon frequencies for III-V semicondutors.

  18. Modeling within-field gate length spatial variation for process-design co-optimization

    NASA Astrophysics Data System (ADS)

    Friedberg, Paul; Cao, Yu; Cain, Jason; Wang, Ruth; Rabaey, Jan; Spanos, Costas

    2005-05-01

    Pelgrom's model suggests that a spatial correlation structure is inherent in the physical properties of semiconductor devices; specifically, devices situated closely together will be subject to a higher degree of correlation than devices separated by larger distances. Since correlation of device gate length values caused by systematic variations in microlithographic processing is known to carry a significant impact on the variability of circuit performance, we attempt to extract and understand the nature of spatial correlation across an entire die. Based on exhaustive, full-wafer critical dimension measurements collected using electrical linewidth metrology for wafers processed in a standard 130nm lithography cell, we calculate a spatial correlation metric of gate length over a full-field range in both horizontal and vertical orientations. Using a rudimentary model fit to these results, we investigate the impact of correlation in the spatial distribution on the variability of circuit performance using a series of Monte Carlo analyses in HSPICE; it is confirmed that this correlation does indeed present a significant influence on performance variability. From the same dataset, we also extract both the across-wafer (AW) and within-field (WIF) contributions to systematic variation. We find that the spatial correlation model"s shape is strongly related to these two components of variation (both in magnitude as well as by spatial fingerprint). By artificially reducing each of these components of systematic variation-thereby simulating the effects of active, across-field process compensation-we show that spatial correlation is significantly reduced, nearly to zero. This implies that Pelgrom's model may not apply to die-scale separation distances, and that a more accurate correlation theory would combine Pelgrom's model over very short separation distances with a systematic variation model that captures variability over longer distances by means of non

  19. Transport behavior across the field-driven superconductor-insulator transition in amorphous indium oxide films

    NASA Astrophysics Data System (ADS)

    Kim, Min-Soo

    Superconductor-insulator transition (SIT) in two-dimensional (2D) thin films is a beautiful realization of a zero temperature quantum phase transition (QPT) and has been explored both theoretically and experimentally over the last two decades. In addition to the several intrinsic ways (such as thickness) of tuning the transition, external magnetic field has been used to tune from one ground state to another in various condensed matter systems. Amorphous indium oxide thin films, with their unique capability of tuning the disorder level in the system easily, have been proven to be an excellent model system to study the transport mechanisms near and across the SIT in 2D. In this thesis, magnetic field-driven SIT in 2D films of amorphous InO x is studied. The goal of this work is to understand the microscopic transport mechanisms responsible for driving the SIT when the magnetic field direction is continually varied from being perpendicular to the sample plane to parallel. Applying a perpendicular magnetic field resulting in a clear field-driven SIT and a magneto-resistance peak on the insulating side in InO x films have been previously understood in a bosonic picture put forward by M. P. A. Fisher and coworkers. However, this boson-vortex duality picture is expected to give rise to markedly different transport characteristics when the magnetic field is applied parallel to the sample plane. Features found in the parallel-field transport data however can also be explained by the bosonic picture, thereby questioning the applicability of the hitherto successful models to the physics of SIT. An isotropic magnetic field value, where the sample has the exact same resistance irrespective of the angle between the sample plane and magnetic field direction, is found. This isotropic point lies at field values above the critical field (Bc) of the SIT (in both perpendicular and parallel configurations) and above the magnetoresistance peak. The isotropic point is very weakly

  20. Magnetic-field-modulated resonant tunneling in ferromagnetic-insulator-nonmagnetic junctions.

    PubMed

    Song, Yang; Dery, Hanan

    2014-07-25

    We present a theory for resonance-tunneling magnetoresistance (MR) in ferromagnetic-insulator-nonmagnetic junctions. The theory sheds light on many of the recent electrical spin injection experiments, suggesting that this MR effect rather than spin accumulation in the nonmagnetic channel corresponds to the electrically detected signal. We quantify the dependence of the tunnel current on the magnetic field by quantum rate equations derived from the Anderson impurity model, with the important addition of impurity spin interactions. Considering the on-site Coulomb correlation, the MR effect is caused by competition between the field, spin interactions, and coupling to the magnetic lead. By extending the theory, we present a basis for operation of novel nanometer-size memories. PMID:25105652

  1. Simulation of Electric Field in Semi Insulating Au/CdTe/Au Detector under Flux

    SciTech Connect

    Franc, J.; James, R.; Grill, R.; Kubat, J.; Belas, E.; Hoschl, P.; Moravec, P.; Praus, P.

    2009-08-02

    We report our simulations on the profile of the electric field in semi insulating CdTe and CdZnTe with Au contacts under radiation flux. The type of the space charge and electric field distribution in the Au/CdTe/Au structure is at high fluxes result of a combined influence of charge formed due to band bending at the electrodes and from photo generated carriers, which are trapped at deep levels. Simultaneous solution of drift-diffusion and Poisson equations is used for the calculation. We show, that the space charge originating from trapped photo-carriers starts to dominate at fluxes 10{sup 15}-10{sup 16}cm{sup -2}s{sup -1}, when the influence of contacts starts to be negligible.

  2. Dual Gate Black Phosphorus Field Effect Transistors on Glass for NOR Logic and Organic Light Emitting Diode Switching.

    PubMed

    Kim, Jin Sung; Jeon, Pyo Jin; Lee, Junyeong; Choi, Kyunghee; Lee, Hee Sung; Cho, Youngsuk; Lee, Young Tack; Hwang, Do Kyung; Im, Seongil

    2015-09-01

    We have fabricated dual gate field effect transistors (FETs) with 12 nm-thin black phosphorus (BP) channel on glass substrate, where our BP FETs have a patterned-gate architecture with 30 nm-thick Al2O3 dielectrics on top and bottom of a BP channel. Top gate dielectric has simultaneously been used as device encapsulation layer, controlling the threshold voltage of FETs as well when FETs mainly operate under bottom gate bias. Bottom, top, and dual gate-controlling mobilities were estimated to be 277, 92, and 213 cm(2)/V s, respectively. Maximum ON-current was measured to be ∼5 μA at a drain voltage of -0.1 V but to be as high as ∼50 μA at -1 V, while ON/OFF current ratio appeared to be 3.6 × 10(3) V. As a result, our dual gate BP FETs demonstrate organic light emitting diode (OLED) switching for green and blue OLEDs, also demonstrating NOR logic functions by separately using top- and bottom-input. PMID:26274095

  3. Gate Modulation of Threshold Voltage Instability in Multilayer InSe Field Effect Transistors.

    PubMed

    Feng, Wei; Zheng, Wei; Chen, XiaoShuang; Liu, Guangbo; Hu, PingAn

    2015-12-01

    We report a modulation of threshold voltage instability of back-gated multilayer InSe FETs by gate bias stress. The performance stability of multilayer InSe FETs is affected by gate bias polar, gate bias stress time and gate bias sweep rate under ambient conditions. The on-current increases and threshold voltage shifts to negative gate bias stress direction with negative bias stress applied, which are opposite to that of positive bias stress. The intensity of gate bias stress effect is influenced by applied gate bias time and the sweep rate of gate bias stress. The behavior can be explained by the surface charge trapping model due to the adsorbing/desorbing oxygen and/or water molecules on the InSe surface. This study offers an opportunity to understand gate bias stress modulation of performance instability of back-gated multilayer InSe FETs and provides a clue for designing desirable InSe nanoelectronic and optoelectronic devices. PMID:26575205

  4. Electron beam collimation with a 40 000 tip metallic double-gate field emitter array and in-situ control of nanotip sharpness distribution

    NASA Astrophysics Data System (ADS)

    Helfenstein, P.; Guzenko, V. A.; Fink, H.-W.; Tsujino, S.

    2013-01-01

    The generation of highly collimated electron beams from a double-gate field emitter array with 40000 metallic tips and large collimation gate apertures is reported. Field emission beam measurements demonstrated the reduction of the beam envelope down to the array size by applying a negative potential to the on-chip gate electrode for the collimation of individual field emission beamlets. Owing to the optimized gate structure, the concomitant decrease of the emission current was minimal, leading to a net enhancement of the current density. Furthermore, a noble gas conditioning process was successfully applied to the double-gate device to improve the beam uniformity in-situ with orders of magnitude increase of the active emission area. The results show that the proposed double-gate field emission cathodes are promising for high current and high brightness electron beam applications such as free-electron lasers and THz power devices.

  5. Breakdown Characteristics of Gas Insulated Switchgears for Non-standard Lightning Impulse Waveforms under Non-uniform Electric Field

    NASA Astrophysics Data System (ADS)

    Ueta, Genyo; Kaneko, Shuhei; Okabe, Shigemitsu

    To improve insulation specification of a gas insulated switchgear (GIS), it is necessary to recognize the insulation characteristics of SF6 gas under actual surge (called non-standard lightning impulse waveform) occurring in the field substation. The authors had observed the insulation characteristics of SF6 gas gap under various types of non-standard lightning impulse waveforms and compared them with under standard lightning impulse waveform quantitatively. From the investigation of the experimental results, the evaluation method for real surges is shown and the method is applied to typical surges for various UHV and 500kV systems. In the proceeding study, therefore, only for the quasi-uniform electric field (with a typical range of the field utilization factors in the bus of a GIS) was investigated. In this paper, the insulation characteristics of SF6 gas gap for non-uniform electric field were observed experimentally and investigated about the evaluation method of converting non-standard lightning impulse waveforms equivalently to the standard lightning impulse waveform.

  6. Modeling of Gate Bias Modulation in Carbon Nanotube Field-Effect-Transistor

    NASA Technical Reports Server (NTRS)

    Toshishige, Yamada; Biegel, Bryan A. (Technical Monitor)

    2002-01-01

    The threshold voltages of a carbon-nanotube (CNT) field-effect transistor (FET) are studied. The CNT channel is so thin that there is no voltage drop perpendicular to the gate electrode plane, and this makes the device characteristics quite unique. The relation between the voltage and the electrochemical potentials, and the mass action law for electrons and holes are examined in the context of CNTs, and inversion and accumulation threshold voltages (V(sub Ti), and V(sub Ta)) are derived. V(sub Ti) of the CNTFETs has a much stronger doping dependence than that of the metal-oxide- semiconductor FETs, while V(sub Ta) of both devices depends weakly on doping with the same functional form.

  7. Calibration of a gated flat field spectrometer as a function of x-ray intensity

    SciTech Connect

    Xiong, Gang; Yang, Guohong; Li, Hang; Zhang, Jiyan Zhao, Yang; Hu, Zhimin; Wei, Minxi; Qing, Bo; Yang, Jiamin; Liu, Shenye; Jiang, Shaoen

    2014-04-15

    We present an experimental determination of the response of a gated flat-field spectrometer at the Shenguang-II laser facility. X-rays were emitted from a target that was heated by laser beams and then were divided into different intensities with a step aluminum filter and collected by a spectrometer. The transmission of the filter was calibrated using the Beijing Synchrotron Radiation Facility. The response characteristics of the spectrometer were determined by comparing the counts recorded by the spectrometer with the relative intensities of the x-rays transmitted through the step aluminum filter. The response characteristics were used to correct the transmission from two shots of an opacity experiment using the same samples. The transmissions from the two shots are consistent with corrections, but discrepant without corrections.

  8. Back gate induced breakdown mechanisms for thin layer SOI field P-channel LDMOS

    NASA Astrophysics Data System (ADS)

    Zhou, Xin; Qiao, Ming; He, Yitao; Yang, Wen; Li, Zhaoji; Zhang, Bo

    2016-01-01

    The back gate (BG) induced breakdown mechanisms for thin layer SOI Field P-channel LDMOS (FPLDMOS) are investigated in this paper. Surface breakdown, bulk breakdown and punch-through breakdown are discussed, revealing that the block capability depends on not drain voltage (Vd), but also BG voltage (VBG). For surface breakdown, the breakdown voltage (BVs) increases linearly with VBG increasing. An expression of BVs on VBG is given, providing a good fitting to measured and simulated results. Bulk breakdown with a low breakdown voltage is attributed to high VBG. VBG induces depletion in n-well, giving rise to punch-through breakdown. A design requirement for the thin layer SOI FPLDMOS is proposed that breakdown voltages for the three breakdown mechanisms are compelled to be higher than the supply voltage of switching IC.

  9. The impact of software and CAE tools on SEU in field programmable gate arrays

    SciTech Connect

    Katz, R.; Wang, J.; McCollum, J.; Cronquist, B.

    1999-12-01

    Field programmable gate array (FPGA) devices, heavily used in spacecraft electronics, have grown substantially in size over the past few years, causing designers to work at a higher conceptual level, with computer aided engineering (CAE) tools synthesizing and optimizing the logic from a description. It is shown that the use of commercial-off-the-shelf (COTS) CAE tools can produce unreliable circuit designs when the device is used in a radiation environment and a flip-flop is upset. At a lower level, software can be used to improve the SEU performance of a flip-flop, exploiting the configurable nature of FPGA technology and on-chip delay, parasitic resistive, and capacitive circuit elements.

  10. Field Programmable Gate Array for Implementation of Redundant Advanced Digital Feedback Control

    NASA Technical Reports Server (NTRS)

    King, K. D.

    2003-01-01

    The goal of this effort was to develop a digital motor controller using field programmable gate arrays (FPGAs). This is a more rugged approach than a conventional microprocessor digital controller. FPGAs typically have higher radiation (rad) tolerance than both the microprocessor and memory required for a conventional digital controller. Furthermore, FPGAs can typically operate at higher speeds. (While speed is usually not an issue for motor controllers, it can be for other system controllers.) Other than motor power, only a 3.3-V digital power supply was used in the controller; no analog bias supplies were used. Since most of the circuit was implemented in the FPGA, no additional parts were needed other than the power transistors to drive the motor. The benefits that FPGAs provide over conventional designs-lower power and fewer parts-allow for smaller packaging and reduced weight and cost.

  11. Gauss-Seidel Accelerated: Implementing Flow Solvers on Field Programmable Gate Arrays

    SciTech Connect

    Chassin, David P.; Armstrong, Peter R.; Chavarría-Miranda, Daniel; Guttromson, Ross T.

    2006-06-01

    Non-linear steady-state power flow solvers have typically relied on the Newton-Raphson method to efficiently compute solutions on today's computer systems. Field Programmable Gate Array (FPGA) devices, which have recently been integrated into high-performance computers by major computer system vendors, offer an opportunity to significantly increase the performance of power flow solvers. However, only some algorithms are suitable for an FPGA implementation. The Gauss-Seidel method of solving the AC power flow problem is an excellent example of such an opportunity. In this paper we discuss algorithmic design considerations, optimization, implementation, and performance results of the implementation of the Gauss-Seidel method running on a Silicon Graphics Inc. Altix-350 computer equipped with a Xilinx Virtex II 6000 FPGA.

  12. Giant plasmon instability in a dual-grating-gate graphene field-effect transistor

    NASA Astrophysics Data System (ADS)

    Koseki, Y.; Ryzhii, V.; Otsuji, T.; Popov, V. V.; Satou, A.

    2016-06-01

    We study the instability of plasmons in a dual-grating-gate graphene field-effect transistor induced by dc current injection using self-consistent simulations with the Boltzmann equation. With only acoustic-phonon-limited electron scattering, it is demonstrated that a total growth rate of the plasmon instability, with a terahertz/midinfrared range of the frequency, can exceed 4 ×1012s-1 at room temperature, which is an order of magnitude larger than in two-dimensional electron gases based on the usual semiconductors. By comparing the simulation results with existing theory, it is revealed that the giant total growth rate originates from a simultaneous occurrence of the so-called Dyakonov-Shur and Ryzhii-Satou-Shur instabilities.

  13. A digital optical phase-locked loop for diode lasers based on field programmable gate array

    SciTech Connect

    Xu Zhouxiang; Zhang Xian; Huang Kaikai; Lu Xuanhui

    2012-09-15

    We have designed and implemented a highly digital optical phase-locked loop (OPLL) for diode lasers in atom interferometry. The three parts of controlling circuit in this OPLL, including phase and frequency detector (PFD), loop filter and proportional integral derivative (PID) controller, are implemented in a single field programmable gate array chip. A structure type compatible with the model MAX9382/MCH12140 is chosen for PFD and pipeline and parallelism technology have been adapted in PID controller. Especially, high speed clock and twisted ring counter have been integrated in the most crucial part, the loop filter. This OPLL has the narrow beat note line width below 1 Hz, residual mean-square phase error of 0.14 rad{sup 2} and transition time of 100 {mu}s under 10 MHz frequency step. A main innovation of this design is the completely digitalization of the whole controlling circuit in OPLL for diode lasers.

  14. A digital optical phase-locked loop for diode lasers based on field programmable gate array.

    PubMed

    Xu, Zhouxiang; Zhang, Xian; Huang, Kaikai; Lu, Xuanhui

    2012-09-01

    We have designed and implemented a highly digital optical phase-locked loop (OPLL) for diode lasers in atom interferometry. The three parts of controlling circuit in this OPLL, including phase and frequency detector (PFD), loop filter and proportional integral derivative (PID) controller, are implemented in a single field programmable gate array chip. A structure type compatible with the model MAX9382∕MCH12140 is chosen for PFD and pipeline and parallelism technology have been adapted in PID controller. Especially, high speed clock and twisted ring counter have been integrated in the most crucial part, the loop filter. This OPLL has the narrow beat note line width below 1 Hz, residual mean-square phase error of 0.14 rad(2) and transition time of 100 μs under 10 MHz frequency step. A main innovation of this design is the completely digitalization of the whole controlling circuit in OPLL for diode lasers. PMID:23020359

  15. Self-Adaptive System based on Field Programmable Gate Array for Extreme Temperature Electronics

    NASA Technical Reports Server (NTRS)

    Keymeulen, Didier; Zebulum, Ricardo; Rajeshuni, Ramesham; Stoica, Adrian; Katkoori, Srinivas; Graves, Sharon; Novak, Frank; Antill, Charles

    2006-01-01

    In this work, we report the implementation of a self-adaptive system using a field programmable gate array (FPGA) and data converters. The self-adaptive system can autonomously recover the lost functionality of a reconfigurable analog array (RAA) integrated circuit (IC) [3]. Both the RAA IC and the self-adaptive system are operating in extreme temperatures (from 120 C down to -180 C). The RAA IC consists of reconfigurable analog blocks interconnected by several switches and programmable by bias voltages. It implements filters/amplifiers with bandwidth up to 20 MHz. The self-adaptive system controls the RAA IC and is realized on Commercial-Off-The-Shelf (COTS) parts. It implements a basic compensation algorithm that corrects a RAA IC in less than a few milliseconds. Experimental results for the cold temperature environment (down to -180 C) demonstrate the feasibility of this approach.

  16. Field evaluation of 69-kV outdoor Polysil insulators. Final report

    SciTech Connect

    Richenbacher, A.G.

    1985-03-01

    After three years of exposure to widely varying climates and environments, Polysil (polymer concrete) 69-kV post-type insulators are still performing satisfactorily. In all test situations, Polysil insulators performed as well as - sometimes even surpassed - their porcelain counterparts. They also demonstrated potential for substantially reducing insulator costs.

  17. Terahertz signal detection in a short gate length field-effect transistor with a two-dimensional electron gas

    SciTech Connect

    Vostokov, N. V. Shashkin, V. I.

    2015-11-28

    We consider the problem of non-resonant detection of terahertz signals in a short gate length field-effect transistor having a two-dimensional electron channel with zero external bias between the source and the drain. The channel resistance, gate-channel capacitance, and quadratic nonlinearity parameter of the transistor during detection as a function of the gate bias voltage are studied. Characteristics of detection of the transistor connected in an antenna with real impedance are analyzed. The consideration is based on both a simple one-dimensional model of the transistor and allowance for the two-dimensional distribution of the electric field in the transistor structure. The results given by the different models are discussed.

  18. Direct probing of electron and hole trapping into nano-floating-gate in organic field-effect transistor nonvolatile memories

    SciTech Connect

    Cui, Ze-Qun; Wang, Shun; Chen, Jian-Mei; Gao, Xu; Dong, Bin E-mail: chilf@suda.edu.cn Chi, Li-Feng E-mail: chilf@suda.edu.cn Wang, Sui-Dong E-mail: chilf@suda.edu.cn

    2015-03-23

    Electron and hole trapping into the nano-floating-gate of a pentacene-based organic field-effect transistor nonvolatile memory is directly probed by Kelvin probe force microscopy. The probing is straightforward and non-destructive. The measured surface potential change can quantitatively profile the charge trapping, and the surface characterization results are in good accord with the corresponding device behavior. Both electrons and holes can be trapped into the nano-floating-gate, with a preference of electron trapping than hole trapping. The trapped charge quantity has an approximately linear relation with the programming/erasing gate bias, indicating that the charge trapping in the device is a field-controlled process.

  19. Ferroelectric Single-Crystal Gated Graphene/Hexagonal-BN/Ferroelectric Field-Effect Transistor.

    PubMed

    Park, Nahee; Kang, Haeyong; Park, Jeongmin; Lee, Yourack; Yun, Yoojoo; Lee, Jeong-Ho; Lee, Sang-Goo; Lee, Young Hee; Suh, Dongseok

    2015-11-24

    The effect of a ferroelectric polarization field on the charge transport in a two-dimensional (2D) material was examined using a graphene monolayer on a hexagonal boron nitride (hBN) field-effect transistor (FET) fabricated using a ferroelectric single-crystal substrate, (1-x)[Pb(Mg1/3Nb2/3)O3]-x[PbTiO3] (PMN-PT). In this configuration, the intrinsic properties of graphene were preserved with the use of an hBN flake, and the influence of the polarization field from PMN-PT could be distinguished. During a wide-range gate-voltage (VG) sweep, a sharp inversion of the spontaneous polarization affected the graphene channel conductance asymmetrically as well as an antihysteretic behavior. Additionally, a transition from antihysteresis to normal ferroelectric hysteresis occurred, depending on the V(G) sweep range relative to the ferroelectric coercive field. We developed a model to interpret the complex coupling among antihysteresis, current saturation, and sudden conductance variation in relation with the ferroelectric switching and the polarization-assisted charge trapping, which can be generalized to explain the combination of 2D structured materials with ferroelectrics. PMID:26487348

  20. Fabrication of Gate-Electrode Integrated Carbon-Nanotube Bundle Field Emitters

    NASA Technical Reports Server (NTRS)

    Toda, Risaku; Bronikowski, Michael; Luong, Edward; Manohara, Harish

    2008-01-01

    A continuing effort to develop carbon-nanotube-based field emitters (cold cathodes) as high-current-density electron sources has yielded an optimized device design and a fabrication scheme to implement the design. One major element of the device design is to use a planar array of bundles of carbon nanotubes as the field-emission tips and to optimize the critical dimensions of the array (principally, heights of bundles and distances between them) to obtain high area-averaged current density and high reliability over a long operational lifetime a concept that was discussed in more detail in Arrays of Bundles of Carbon Nanotubes as Field Emitters (NPO-40817), NASA Tech Briefs, Vol. 31, No. 2 (February 2007), page 58. Another major element of the design is to configure the gate electrodes (anodes used to extract, accelerate, and/or focus electrons) as a ring that overhangs a recess wherein the bundles of nanotubes are located, such that by virtue of the proximity between the ring and the bundles, a relatively low applied potential suffices to generate the large electric field needed for emission of electrons.

  1. Low Temperature Solution-Processed Gate Dielectrics for Low-Voltage Organic Field-Effect Transistors.

    PubMed

    Ha, Young-Geun

    2015-09-01

    We report on the design, preparation, and electrical properties of novel solution-processed organic-inorganic hybrid dielectric films for the low-voltage operation of organic field-effect transistors (OFETs). Hybrid dielectric thin films (-20 nm thick) are easily fabricated by spin-coating a zirconium chloride precursor/organic additive reagent mixture, followed by annealing at low temperatures (-150 degrees C). The smooth and transparent hybrid dielectrics exhibit great insulating properties (leakage current densities -10(-7) A/cm2 at 2 MV/cm), high capacitance (170 nF/cm2). OFETs fabricated with hybrid dielectric and pentacene semiconductor function great at relatively low voltage (mobility: 1 cm2/V x s, on/off current ratio: 10(5)). PMID:26716219

  2. Gating capacitive field-effect sensors by the charge of nanoparticle/molecule hybrids.

    PubMed

    Poghossian, Arshak; Bäcker, Matthias; Mayer, Dirk; Schöning, Michael J

    2015-01-21

    The semiconductor field-effect platform is a powerful tool for chemical and biological sensing with direct electrical readout. In this work, the field-effect capacitive electrolyte-insulator-semiconductor (EIS) structure - the simplest field-effect (bio-)chemical sensor - modified with citrate-capped gold nanoparticles (AuNPs) has been applied for a label-free electrostatic detection of charged molecules by their intrinsic molecular charge. The EIS sensor detects the charge changes in AuNP/molecule inorganic/organic hybrids induced by the molecular adsorption or binding events. The feasibility of the proposed detection scheme has been exemplarily demonstrated by realizing capacitive EIS sensors consisting of an Al-p-Si-SiO2-silane-AuNP structure for the label-free detection of positively charged cytochrome c and poly-d-lysine molecules as well as for monitoring the layer-by-layer formation of polyelectrolyte multilayers of poly(allylamine hydrochloride)/poly(sodium 4-styrene sulfonate), representing typical model examples of detecting small proteins and macromolecules and the consecutive adsorption of positively/negatively charged polyelectrolytes, respectively. For comparison, EIS sensors without AuNPs have been investigated, too. The adsorption of molecules on the surface of AuNPs has been verified via the X-ray photoelectron spectroscopy method. In addition, a theoretical model of the functioning of the capacitive field-effect EIS sensor functionalized with AuNP/charged-molecule hybrids has been discussed. PMID:25470772

  3. SUPERGLASS. Engineering field tests - Phase 3. Production, market planning, and product evaluation for a high-thermal-performance insulating glass design utilizing HEAT MIRROR transparent insulation. Final report

    SciTech Connect

    Tilford, C L

    1982-11-01

    HEAT MIRROR transparent window insulation consists of a clear polyester film two mils (.002'') thick with a thin, clear low-emissivity (.15) coating deposited on one side by state-of-the-art vacuum deposition processes. This neutral-colored invisible coating reflects long-wave infrared energy (heat). When mounted by being stretched with a 1/2'' air-gap on each side of the film, the resulting unit reduces heat loss by 60% compared to dual insulating glass. Southwall Corporation produces HEAT MIRROR transparent insulation and markets it to manufacturers of sealed insulating glass (I.G.) units and window and building manufacturers who make their own I.G. These companies build and sell the SUPERGLASS sealed glazing units. Units made and installed in buildings by six customers were visited. These units were located in many geographic regions, including the Pacific Northwest, Rocky Mountains, New England, Southeast, and West Coast. As much as could be obtained of their history was recorded, as was their current condition and performance. These units had been in place from two weeks to over a year. All of the units were performing thermally very well, as measured by taking temperature profiles through them and through adjacent conventional I.G. units. Some units had minor visual defects (attributed to I.G. assembly techniques) which are discussed in detail. Overall occupant acceptance was enthusiastically positive. In addition to saving energy, without compromise of optical quality or appearance, the product makes rooms with large glazing areas comfortable to be in in cold weather. All defects observed were present when built; there appears to be no in-field degradation of quality at this time.

  4. Simulation-based study of negative-capacitance double-gate tunnel field-effect transistor with ferroelectric gate stack

    NASA Astrophysics Data System (ADS)

    Liu, Chien; Chen, Ping-Guang; Xie, Meng-Jie; Liu, Shao-Nong; Lee, Jun-Wei; Huang, Shao-Jia; Liu, Sally; Chen, Yu-Sheng; Lee, Heng-Yuan; Liao, Ming-Han; Chen, Pang-Shiu; Lee, Min-Hung

    2016-04-01

    The concept of ferroelectric (FE) negative capacitance (NC) may be a turning point in overcoming the physical limitations imposed by the Boltzmann tyranny to realize next-generation state-of-the-art devices. Both the body factor (m-factor) and the transport mechanism (n-factor) are simultaneously improved by integrating an NC with a tunnel FET (TFET). The modeling approach is discussed in this study as well as the NC physics. By optimizing the thicknesses of FE, semiconductor, and interfacial layers, the capacitance of the FE layers is modulated to match that of a MOS resulting in the smallest subthreshold swing that is also hysteresis-free. An ultrathin-body double gate tunnel FET (UTB-DG-TFET) exhibits a steep slope (a subthreshold swing below 10 mV/dec over more than 4 orders of magnitude) for low-power applications (<0.2 V switching voltage) to realize next-generation state-of-the-art devices.

  5. Misalignment-free signal propagation in nanomagnet arrays and logic gates with 45°-clocking field

    SciTech Connect

    Li, Zheng; Kwon, Byung Seok; Krishnan, Kannan M.

    2014-05-07

    A key obstacle for the application of Magnetic Quantum-dot Cellular Automata (MQCA) is the misalignment of clocking field, which results in low stability for both signal propagations within nanomagnet array and logic operation in majority gates. Here, we demonstrate that a reversal clocking field applied at 45° off the hard axis, with progressively reduced amplitude, applied to a shape-tuned nanomagnet array fabricated by e-beam lithography, helps intrinsically eliminate the misalignment sensitivity of the elements and results in correct signal propagation. Further, least reversal steps and reduced field amplitude was required owing to the 45°-clocking field. This clocking field was also tested for majority gates (OR function) and characterized by Magnetic Force Microscopy demonstrating correct output. This novel design provides high stability for signal propagation and logic operation of MQCA and potentially paves way for its application.

  6. Silicon-on-insulator field effect transistor with improved body ties for rad-hard applications

    DOEpatents

    Schwank, James R.; Shaneyfelt, Marty R.; Draper, Bruce L.; Dodd, Paul E.

    2001-01-01

    A silicon-on-insulator (SOI) field-effect transistor (FET) and a method for making the same are disclosed. The SOI FET is characterized by a source which extends only partially (e.g. about half-way) through the active layer wherein the transistor is formed. Additionally, a minimal-area body tie contact is provided with a short-circuit electrical connection to the source for reducing floating body effects. The body tie contact improves the electrical characteristics of the transistor and also provides an improved single-event-upset (SEU) radiation hardness of the device for terrestrial and space applications. The SOI FET also provides an improvement in total-dose radiation hardness as compared to conventional SOI transistors fabricated without a specially prepared hardened buried oxide layer. Complementary n-channel and p-channel SOI FETs can be fabricated according to the present invention to form integrated circuits (ICs) for commercial and military applications.

  7. Giant Electroresistance in Edge Metal-Insulator-Metal Tunnel Junctions Induced by Ferroelectric Fringe Fields

    NASA Astrophysics Data System (ADS)

    Jung, Sungchul; Jeon, Youngeun; Jin, Hanbyul; Lee, Jung-Yong; Ko, Jae-Hyeon; Kim, Nam; Eom, Daejin; Park, Kibog

    2016-08-01

    An enormous amount of research activities has been devoted to developing new types of non-volatile memory devices as the potential replacements of current flash memory devices. Theoretical device modeling was performed to demonstrate that a huge change of tunnel resistance in an Edge Metal-Insulator-Metal (EMIM) junction of metal crossbar structure can be induced by the modulation of electric fringe field, associated with the polarization reversal of an underlying ferroelectric layer. It is demonstrated that single three-terminal EMIM/Ferroelectric structure could form an active memory cell without any additional selection devices. This new structure can open up a way of fabricating all-thin-film-based, high-density, high-speed, and low-power non-volatile memory devices that are stackable to realize 3D memory architecture.

  8. Giant Electroresistance in Edge Metal-Insulator-Metal Tunnel Junctions Induced by Ferroelectric Fringe Fields.

    PubMed

    Jung, Sungchul; Jeon, Youngeun; Jin, Hanbyul; Lee, Jung-Yong; Ko, Jae-Hyeon; Kim, Nam; Eom, Daejin; Park, Kibog

    2016-01-01

    An enormous amount of research activities has been devoted to developing new types of non-volatile memory devices as the potential replacements of current flash memory devices. Theoretical device modeling was performed to demonstrate that a huge change of tunnel resistance in an Edge Metal-Insulator-Metal (EMIM) junction of metal crossbar structure can be induced by the modulation of electric fringe field, associated with the polarization reversal of an underlying ferroelectric layer. It is demonstrated that single three-terminal EMIM/Ferroelectric structure could form an active memory cell without any additional selection devices. This new structure can open up a way of fabricating all-thin-film-based, high-density, high-speed, and low-power non-volatile memory devices that are stackable to realize 3D memory architecture. PMID:27476475

  9. Giant Electroresistance in Edge Metal-Insulator-Metal Tunnel Junctions Induced by Ferroelectric Fringe Fields

    PubMed Central

    Jung, Sungchul; Jeon, Youngeun; Jin, Hanbyul; Lee, Jung-Yong; Ko, Jae-Hyeon; Kim, Nam; Eom, Daejin; Park, Kibog

    2016-01-01

    An enormous amount of research activities has been devoted to developing new types of non-volatile memory devices as the potential replacements of current flash memory devices. Theoretical device modeling was performed to demonstrate that a huge change of tunnel resistance in an Edge Metal-Insulator-Metal (EMIM) junction of metal crossbar structure can be induced by the modulation of electric fringe field, associated with the polarization reversal of an underlying ferroelectric layer. It is demonstrated that single three-terminal EMIM/Ferroelectric structure could form an active memory cell without any additional selection devices. This new structure can open up a way of fabricating all-thin-film-based, high-density, high-speed, and low-power non-volatile memory devices that are stackable to realize 3D memory architecture. PMID:27476475

  10. Field programmable gate array based reconfigurable scanning probe/optical microscope.

    PubMed

    Nowak, Derek B; Lawrence, A J; Dzegede, Zechariah K; Hiester, Justin C; Kim, Cliff; Sánchez, Erik J

    2011-10-01

    The increasing popularity of nanometrology and nanospectroscopy has pushed researchers to develop complex new analytical systems. This paper describes the development of a platform on which to build a microscopy tool that will allow for flexibility of customization to suit research needs. The novelty of the described system lies in its versatility of capabilities. So far, one version of this microscope has allowed for successful near-field and far-field fluorescence imaging with single molecule detection sensitivity. This system is easily adapted for reflection, polarization (Kerr magneto-optical (MO)), Raman, super-resolution techniques, and other novel scanning probe imaging and spectroscopic designs. While collecting a variety of forms of optical images, the system can simultaneously monitor topographic information of a sample with an integrated tuning fork based shear force system. The instrument has the ability to image at room temperature and atmospheric pressure or under liquid. The core of the design is a field programmable gate array (FPGA) data acquisition card and a single, low cost computer to control the microscope with analog control circuitry using off-the-shelf available components. A detailed description of electronics, mechanical requirements, and software algorithms as well as examples of some different forms of the microscope developed so far are discussed. PMID:22047297

  11. Field programmable gate array based reconfigurable scanning probe/optical microscope

    NASA Astrophysics Data System (ADS)

    Nowak, Derek B.; Lawrence, A. J.; Dzegede, Zechariah K.; Hiester, Justin C.; Kim, Cliff; Sánchez, Erik J.

    2011-10-01

    The increasing popularity of nanometrology and nanospectroscopy has pushed researchers to develop complex new analytical systems. This paper describes the development of a platform on which to build a microscopy tool that will allow for flexibility of customization to suit research needs. The novelty of the described system lies in its versatility of capabilities. So far, one version of this microscope has allowed for successful near-field and far-field fluorescence imaging with single molecule detection sensitivity. This system is easily adapted for reflection, polarization (Kerr magneto-optical (MO)), Raman, super-resolution techniques, and other novel scanning probe imaging and spectroscopic designs. While collecting a variety of forms of optical images, the system can simultaneously monitor topographic information of a sample with an integrated tuning fork based shear force system. The instrument has the ability to image at room temperature and atmospheric pressure or under liquid. The core of the design is a field programmable gate array (FPGA) data acquisition card and a single, low cost computer to control the microscope with analog control circuitry using off-the-shelf available components. A detailed description of electronics, mechanical requirements, and software algorithms as well as examples of some different forms of the microscope developed so far are discussed.

  12. Reliability tests of gated silicon field emitters for use in space

    NASA Astrophysics Data System (ADS)

    Aplin, K. L.; Collingwood, C. M.; Kent, B. J.

    2004-07-01

    Neutralizers are required to prevent spacecraft charging from satellite ion propulsion. This paper discusses the development of a gated silicon tip field emitter (FE) neutralizer, specified to deliver 6 mA, with each tip emitting a mean current of 7 nA. It is important to investigate factors affecting the lifetime of field emitter arrays for a space application, as longevity and reliability are both critical requirements. Semi-automated procedures to prepare 400 arrays, each consisting of 765 FEs, for life tests are described with failure conditions strictly defined by mission constraints. Results of 25 life tests on 72 arrays driven to failure at constant emission current are summarized, and a case study of one test is presented. Two of the three failure mechanisms identified are consistent with thermal failure and damage by ion bombardment. Reduced field enhancement from tip erosion caused by ion bombardment is a common explanation for FE failure. However, scanning electron microscope examination of tip apex diameters showed no significant relationship between array failure and apex geometry. The third failure mechanism was associated with short-lived arrays and may be caused by manufacturing defects. Substantial intrinsic variability was observed in the arrays tested, even with the rigorous production standards required for space applications. Arrays without manufacturing defects had lifetimes of thousands of hours.

  13. A digital magnetic resonance imaging spectrometer using digital signal processor and field programmable gate array

    NASA Astrophysics Data System (ADS)

    Liang, Xiao; Binghe, Sun; Yueping, Ma; Ruyan, Zhao

    2013-05-01

    A digital spectrometer for low-field magnetic resonance imaging is described. A digital signal processor (DSP) is utilized as the pulse programmer on which a pulse sequence is executed as a subroutine. Field programmable gate array (FPGA) devices that are logically mapped into the external addressing space of the DSP work as auxiliary controllers of gradient control, radio frequency (rf) generation, and rf receiving separately. The pulse programmer triggers an event by setting the 32-bit control register of the corresponding FPGA, and then the FPGA automatically carries out the event function according to preset configurations in cooperation with other devices; accordingly, event control of the spectrometer is flexible and efficient. Digital techniques are in widespread use: gradient control is implemented in real-time by a FPGA; rf source is constructed using direct digital synthesis technique, and rf receiver is constructed using digital quadrature detection technique. Well-designed performance is achieved, including 1 μs time resolution of the gradient waveform, 1 μs time resolution of the soft pulse, and 2 MHz signal receiving bandwidth. Both rf synthesis and rf digitalization operate at the same 60 MHz clock, therefore, the frequency range of transmitting and receiving is from DC to ˜27 MHz. A majority of pulse sequences have been developed, and the imaging performance of the spectrometer has been validated through a large number of experiments. Furthermore, the spectrometer is also suitable for relaxation measurement in nuclear magnetic resonance field.

  14. A digital magnetic resonance imaging spectrometer using digital signal processor and field programmable gate array.

    PubMed

    Liang, Xiao; Binghe, Sun; Yueping, Ma; Ruyan, Zhao

    2013-05-01

    A digital spectrometer for low-field magnetic resonance imaging is described. A digital signal processor (DSP) is utilized as the pulse programmer on which a pulse sequence is executed as a subroutine. Field programmable gate array (FPGA) devices that are logically mapped into the external addressing space of the DSP work as auxiliary controllers of gradient control, radio frequency (rf) generation, and rf receiving separately. The pulse programmer triggers an event by setting the 32-bit control register of the corresponding FPGA, and then the FPGA automatically carries out the event function according to preset configurations in cooperation with other devices; accordingly, event control of the spectrometer is flexible and efficient. Digital techniques are in widespread use: gradient control is implemented in real-time by a FPGA; rf source is constructed using direct digital synthesis technique, and rf receiver is constructed using digital quadrature detection technique. Well-designed performance is achieved, including 1 μs time resolution of the gradient waveform, 1 μs time resolution of the soft pulse, and 2 MHz signal receiving bandwidth. Both rf synthesis and rf digitalization operate at the same 60 MHz clock, therefore, the frequency range of transmitting and receiving is from DC to ~27 MHz. A majority of pulse sequences have been developed, and the imaging performance of the spectrometer has been validated through a large number of experiments. Furthermore, the spectrometer is also suitable for relaxation measurement in nuclear magnetic resonance field. PMID:23742570

  15. An extended-gate type organic field effect transistor functionalised by phenylboronic acid for saccharide detection in water.

    PubMed

    Minami, Tsuyoshi; Minamiki, Tsukuru; Hashima, Yuki; Yokoyama, Daisuke; Sekine, Tomohito; Fukuda, Kenjiro; Kumaki, Daisuke; Tokito, Shizuo

    2014-12-21

    Saccharides in water are detected electrically using an extended-gate type organic field effect transistor (OFET) functionalised by a phenylboronic acid monolayer. The response patterns of the monosaccharides are significantly different, suggesting that OFET devices can successfully read out the saccharide recognition behaviour of boronic acids and be potentially applied to healthcare devices modified with supramolecular receptors. PMID:25360460

  16. Transient changes in electric fields induced by interaction of ultraintense laser pulses with insulator and metal foils: Sustainable fields spanning several millimeters

    NASA Astrophysics Data System (ADS)

    Inoue, Shunsuke; Tokita, Shigeki; Hashida, Masaki; Sakabe, Shuji

    2015-04-01

    The temporal evolutions of electromagnetic fields generated by the interaction between ultraintense lasers (1.3 ×1018 and 8.2 ×1018W /c m2 ) and solid targets at a distance of several millimeters from the laser-irradiated region have been investigated by electron deflectometry. For three types of foil targets (insulating foil, conductive foil, and insulating foil onto which a metal disk was deposited), transient changes in the fields were observed. We found that the direction, strength, and temporal evolution of the generated fields differ markedly for these three types of targets. The results provide an insight for studying the emission dynamics of laser-accelerated fast electrons.

  17. Field-Programmable Gate Array Computer in Structural Analysis: An Initial Exploration

    NASA Technical Reports Server (NTRS)

    Singleterry, Robert C., Jr.; Sobieszczanski-Sobieski, Jaroslaw; Brown, Samuel

    2002-01-01

    This paper reports on an initial assessment of using a Field-Programmable Gate Array (FPGA) computational device as a new tool for solving structural mechanics problems. A FPGA is an assemblage of binary gates arranged in logical blocks that are interconnected via software in a manner dependent on the algorithm being implemented and can be reprogrammed thousands of times per second. In effect, this creates a computer specialized for the problem that automatically exploits all the potential for parallel computing intrinsic in an algorithm. This inherent parallelism is the most important feature of the FPGA computational environment. It is therefore important that if a problem offers a choice of different solution algorithms, an algorithm of a higher degree of inherent parallelism should be selected. It is found that in structural analysis, an 'analog computer' style of programming, which solves problems by direct simulation of the terms in the governing differential equations, yields a more favorable solution algorithm than current solution methods. This style of programming is facilitated by a 'drag-and-drop' graphic programming language that is supplied with the particular type of FPGA computer reported in this paper. Simple examples in structural dynamics and statics illustrate the solution approach used. The FPGA system also allows linear scalability in computing capability. As the problem grows, the number of FPGA chips can be increased with no loss of computing efficiency due to data flow or algorithmic latency that occurs when a single problem is distributed among many conventional processors that operate in parallel. This initial assessment finds the FPGA hardware and software to be in their infancy in regard to the user conveniences; however, they have enormous potential for shrinking the elapsed time of structural analysis solutions if programmed with algorithms that exhibit inherent parallelism and linear scalability. This potential warrants further

  18. Silicon on ferroelectic insulator field effect transistor (SOF-FET) a new device for the next generation ultra low power circuits

    NASA Astrophysics Data System (ADS)

    Es-Sakhi, Azzedin D.

    Field effect transistors (FETs) are the foundation for all electronic circuits and processors. These devices have progressed massively to touch its final steps in sub-nanometer level. Left and right proposals are coming to rescue this progress. Emerging nano-electronic devices (resonant tunneling devices, single-atom transistors, spin devices, Heterojunction Transistors rapid flux quantum devices, carbon nanotubes, and nanowire devices) took a vast share of current scientific research. Non-Si electronic materials like III-V heterostructure, ferroelectric, carbon nanotubes (CNTs), and other nanowire based designs are in developing stage to become the core technology of non-classical CMOS structures. FinFET present the current feasible commercial nanotechnology. The scalability and low power dissipation of this device allowed for an extension of silicon based devices. High short channel effect (SCE) immunity presents its major advantage. Multi-gate structure comes to light to improve the gate electrostatic over the channel. The new structure shows a higher performance that made it the first candidate to substitute the conventional MOSFET. The device also shows a future scalability to continue Moor's Law. Furthermore, the device is compatible with silicon fabrication process. Moreover, the ultra-low-power (ULP) design required a subthreshold slope lower than the thermionic-emission limit of 60mV/ decade (KT/q). This value was unbreakable by the new structure (SOI-FinFET). On the other hand most of the previews proposals show the ability to go beyond this limit. However, those pre-mentioned schemes have publicized a very complicated physics, design difficulties, and process non-compatibility. The objective of this research is to discuss various emerging nano-devices proposed for ultra-low-power designs and their possibilities to replace the silicon devices as the core technology in the future integrated circuit. This thesis proposes a novel design that exploits the

  19. Electric-field-induced spin resonance in antiferromagnetic insulators: Inverse process of the dynamical chiral magnetic effect

    NASA Astrophysics Data System (ADS)

    Sekine, Akihiko; Chiba, Takahiro

    2016-06-01

    We propose a realization of the electric-field-induced antiferromagnetic resonance. We consider three-dimensional antiferromagnetic insulators with spin-orbit coupling characterized by the existence of a topological term called the θ term. By solving the Landau-Lifshitz-Gilbert equation in the presence of the θ term, we show that, in contrast to conventional methods using ac magnetic fields, the antiferromagnetic resonance state is realized by ac electric fields along with static magnetic fields. This mechanism can be understood as the inverse process of the dynamical chiral magnetic effect, an alternating current generation by magnetic fields. In other words, we propose a way to electrically induce the dynamical axion field in condensed matter. We discuss a possible experiment to observe our proposal, which utilizes the spin pumping from the antiferromagnetic insulator into a heavy metal contact.

  20. Electric-field-induced metal maintained by current of the Mott insulator Ca2RuO4

    PubMed Central

    Nakamura, Fumihiko; Sakaki, Mariko; Yamanaka, Yuya; Tamaru, Sho; Suzuki, Takashi; Maeno, Yoshiteru

    2013-01-01

    Recently, “application of electric field (E-field)” has received considerable attention as a new method to induce novel quantum phenomena since application of E-field can tune the electronic states directly with obvious scientific and industrial advantages over other turning methods. However, E-field-induced Mott transitions are rare and typically require high E-field and low temperature. Here we report that the multiband Mott insulator Ca2RuO4 shows unique insulator-metal switching induced by applying a dry-battery level voltage at room temperature. The threshold field Eth ~40 V/cm is much weaker than the Mott gap energy. Moreover, the switching is accompanied by a bulk structural transition. Perhaps the most peculiar of the present findings is that the induced metal can be maintained to low temperature by a weak current. PMID:23985626

  1. Radiation-Insensitive Inverse Majority Gates

    NASA Technical Reports Server (NTRS)

    Manohara, Harish; Mojarradi, Mohammad

    2008-01-01

    To help satisfy a need for high-density logic circuits insensitive to radiation, it has been proposed to realize inverse majority gates as microscopic vacuum electronic devices. In comparison with solid-state electronic devices ordinarily used in logic circuits, vacuum electronic devices are inherently much less adversely affected by radiation and extreme temperatures. The proposed development would involve state-of-the-art micromachining and recent advances in the fabrication of carbon-nanotube-based field emitters. A representative three-input inverse majority gate would be a monolithic, integrated structure that would include three gate electrodes, six bundles of carbon nanotubes (serving as electron emitters) at suitable positions between the gate electrodes, and an overhanging anode. The bundles of carbon nanotubes would be grown on degenerately doped silicon substrates that would be parts of the monolithic structure. The gate electrodes would be fabricated as parts of the monolithic structure by means of a double-silicon-on-insulator process developed at NASA's Jet Propulsion Laboratory. The tops of the bundles of carbon nanotubes would lie below the plane of the tops of the gate electrodes. The particular choice of shapes, dimensions, and relative positions of the electrodes and bundles of carbon nanotubes would provide for both field emission of electrons from the bundles of carbon nanotubes and control of the electron current to obtain the inverse majority function, which is described in the paper.

  2. Field application of smart SHM using field programmable gate array technology to monitor an RC bridge in New Mexico

    NASA Astrophysics Data System (ADS)

    Azarbayejani, M.; Jalalpour, M.; El-Osery, A. I.; Reda Taha, M. M.

    2011-08-01

    In this paper, an innovative field application of a structural health monitoring (SHM) system using field programmable gate array (FPGA) technology and wireless communication is presented. The new SHM system was installed to monitor a reinforced concrete (RC) bridge on Interstate 40 (I-40) in Tucumcari, New Mexico. This newly installed system allows continuous remote monitoring of this bridge using solar power. Details of the SHM component design and installation are discussed. The integration of FPGA and solar power technologies make it possible to remotely monitor infrastructure with limited access to power. Furthermore, the use of FPGA technology enables smart monitoring where data communication takes place on-need (when damage warning signs are met) and on-demand for periodic monitoring of the bridge. Such a system enables a significant cut in communication cost and power demands which are two challenges during SHM operation. Finally, a three-dimensional finite element (FE) model of the bridge was developed and calibrated using a static loading field test. This model is then used for simulating damage occurrence on the bridge. Using the proposed automation process for SHM will reduce human intervention significantly and can save millions of dollars currently spent on prescheduled inspection of critical infrastructure worldwide.

  3. Hydrogen ion-selective electrolyte-gated organic field-effect transistor for pH sensing

    NASA Astrophysics Data System (ADS)

    Kofler, Johannes; Schmoltner, Kerstin; Klug, Andreas; List-Kratochvil, Emil J. W.

    2014-05-01

    A H+ ion-selective electrolyte-gated organic field-effect transistor (IS-EGOFET) with a broad detection range between pH 3 and pH 12, is presented. This pH sensor relies on an integrated EGOFET used as a transducer in combination with an ionophore-doped polymeric ion-selective membrane serving as a sensing element. The broad detection range was possible through a dynamic measurement protocol comprising a readjustment of the gate voltage, which ensures a stable device operation at a constant working point. The effectiveness of this dynamic approach is confirmed by stability investigations. On the basis of this pH sensor concept, the importance of an appropriate gating electrolyte is highlighted, giving insights into the working mechanism of EGOFETs.

  4. Physics of gate leakage current in N-polar InAlN/GaN heterojunction field effect transistors

    SciTech Connect

    Goswami, Arunesh; Trew, Robert J.; Bilbro, Griff L.

    2014-10-28

    A physics based model of the gate leakage current in N-polar InAlN/GaN heterojunction field effect transistors is demonstrated. The model is based on the space charge limited current flow dominated by the effects of deep traps in the InAlN surface layer. The model predicts accurately the gate-leakage measurement data of the N-polar InAlN/GaN device with InAlN cap layer. In the pinch-off state, the gate leakage current conduction through the surface of the device in the drain access region dominates the current flow through the two dimensional electron gas channel. One deep trap level and two levels of shallow traps are extracted by fitting the model results with measurement data.

  5. A bottom-gate silicon nanowire field-effect transistor with functionalized palladium nanoparticles for hydrogen gas sensors

    NASA Astrophysics Data System (ADS)

    Choi, Bongsik; Ahn, Jae-Hyuk; Lee, Jieun; Yoon, Jinsu; Lee, Juhee; Jeon, Minsu; Kim, Dong Myong; Kim, Dae Hwan; Park, Inkyu; Choi, Sung-Jin

    2015-12-01

    The highly sensitive operation of a bottom-gate silicon nanowire (SiNW) field-effect transistor (FET)-based hydrogen (H2) sensor is demonstrated by controlling the working regime of the sensor. It is observed that the deposition of palladium (Pd) nanoparticles on the SiNW surface for the selective absorption of H2 can result in a significant enhancement of the electrostatic properties, such as the subthreshold swing and on-current, of the SiNW FET-based H2 sensor. By comparing the experimental results with the numerical simulation, we conclude that the improvement of the electrostatic properties of the sensor is due to the coupling effect between the electrostatic potentials in the Pd nanoparticle and bottom gate. Based on these results, highly sensitive detection of H2 gas could be achieved in the subthreshold regime where the gating effect induced by absorbed H2 gas is the most effective.

  6. Electron Transport Behavior on Gate Length Scaling in Sub-50 nm GaAs Metal Semiconductor Field Effect Transistors

    NASA Astrophysics Data System (ADS)

    Han, Jaeheon

    2011-12-01

    Short channel GaAs Metal Semiconductor Field Effect Transistors (MESFETs) have been fabricated with gate length to 20 nm, in order to examine the characteristics of sub-50 nm MESFET scaling. Here the rise in the measured transconductance is mainly attributed to electron velocity overshoot. For gate lengths below 40 nm, however, the transconductance drops suddenly. The behavior of velocity overshoot and its degradation is investigated and simulated by using a transport model based on the retarded Langevin equation (RLE). This indicates the existence of a minimum acceleration length needed for the carriers to reach the overshoot velocity. The argument shows that the source resistance must be included as an internal element, or appropriate boundary condition, of relative importance in any model where the gate length is comparable to the inelastic mean free path of the carriers.

  7. GaN-Based Trench Gate Metal Oxide Semiconductor Field-Effect Transistor Fabricated with Novel Wet Etching

    NASA Astrophysics Data System (ADS)

    Kodama, Masahito; Sugimoto, Masahiro; Hayashi, Eiko; Soejima, Narumasa; Ishiguro, Osamu; Kanechika, Masakazu; Itoh, Kenji; Ueda, Hiroyuki; Uesugi, Tsutomu; Kachi, Tetsu

    2008-02-01

    A novel method for fabricating trench structures on GaN was developed. A smooth non-polar (1100) plane was obtained by wet etching using tetramethylammonium hydroxide (TMAH) as the etchant. A U-shape trench with the (1100) plane side walls was formed with dry etching and the TMAH wet etching. A U-shape trench gate metal oxide semiconductor field-effect transistor (MOSFET) was also fabricated using the novel etching technology. This device has the excellent normally-off operation of drain current-gate voltage characteristics with the threshold voltage of 10 V. The drain breakdown voltage of 180 V was obtained. The results indicate that the trench gate structure can be applied to GaN-based transistors.

  8. Field Effect Modulation of Outer-Sphere Electrochemistry at Back-Gated, Ultrathin ZnO Electrodes.

    PubMed

    Kim, Chang-Hyun; Frisbie, C Daniel

    2016-06-15

    Here we report field-effect modulation of solution electrochemistry at 5 nm thick ZnO working electrodes prepared on SiO2/degenerately doped Si gates. We find that ultrathin ZnO behaves like a 2D semiconductor, in which charge carriers electrostatically induced by the back gate lead to band edge shift at the front electrode/electrolyte interface. This, in turn, manipulates the charge transfer kinetics on the electrode at a given electrode potential. Experimental results and the proposed model indicate that band edge alignment can be effectively modulated by 0.1-0.4 eV depending on the density of states in the semiconductor and the capacitance of the gate/dielectric stack. PMID:27249050

  9. Hydrogen-terminated diamond vertical-type metal oxide semiconductor field-effect transistors with a trench gate

    NASA Astrophysics Data System (ADS)

    Inaba, Masafumi; Muta, Tsubasa; Kobayashi, Mikinori; Saito, Toshiki; Shibata, Masanobu; Matsumura, Daisuke; Kudo, Takuya; Hiraiwa, Atsushi; Kawarada, Hiroshi

    2016-07-01

    The hydrogen-terminated diamond surface (C-H diamond) has a two-dimensional hole gas (2DHG) layer independent of the crystal orientation. A 2DHG layer is ubiquitously formed on the C-H diamond surface covered by atomic-layer-deposited-Al2O3. Using Al2O3 as a gate oxide, C-H diamond metal oxide semiconductor field-effect transistors (MOSFETs) operate in a trench gate structure where the diamond side-wall acts as a channel. MOSFETs with a side-wall channel exhibit equivalent performance to the lateral C-H diamond MOSFET without a side-wall channel. Here, a vertical-type MOSFET with a drain on the bottom is demonstrated in diamond with channel current modulation by the gate and pinch off.

  10. Electron Transport in Graphene Nanoribbon Field-Effect Transistor under Bias and Gate Voltages: Isochemical Potential Approach.

    PubMed

    Yun, Jeonghun; Lee, Geunsik; Kim, Kwang S

    2016-07-01

    Zigzag graphene nanoribbon (zGNR) of narrow width has a moderate energy gap in its antiferromagnetic ground state. So far, first-principles electron transport calculations have been performed using nonequilibrium Green function (NEGF) method combined with density functional theory (DFT). However, the commonly practiced bottom-gate control has not been studied computationally due to the need to simulate an electron reservoir that fixes the chemical potential of electrons in the zGNR and electrodes. Here, we present the isochemical potential scheme to describe the top/back-gate effect using external potential. Then, we examine the change in electronic state under the modulation of chemical potential and the subsequent electron transport phenomena in zGNR transistor under substantial top-/back-gate and bias voltages. The gate potential can activate the device states resulting in a boosted current. This gate-controlled current-boosting could be utilized for designing novel zGNR field effect transistors (FETs). PMID:27299184

  11. Physiologically gated micro-beam radiation therapy using electronically controlled field emission x-ray source array

    NASA Astrophysics Data System (ADS)

    Chtcheprov, Pavel; Hadsell, Michael; Burk, Laurel; Ger, Rachel; Zhang, Lei; Yuan, Hong; Lee, Yueh Z.; Chang, Sha; Lu, Jianping; Zhou, Otto

    2013-03-01

    Micro-beam radiation therapy (MRT) uses parallel planes of high dose narrow (10-100 um in width) radiation beams separated by a fraction of a millimeter to treat cancerous tumors. This experimental therapy method based on synchrotron radiation has been shown to spare normal tissue at up to 1000Gy of entrance dose while still being effective in tumor eradication and extending the lifetime of tumor-bearing small animal models. Motion during the treatment can result in significant movement of micro beam positions resulting in broader beam width and lower peak to valley dose ratio (PVDR), and thus can reduce the effectiveness of the MRT. Recently we have developed the first bench-top image guided MRT system for small animal treatment using a high powered carbon nanotube (CNT) x-ray source array. The CNT field emission x-ray source can be electronically synchronized to an external triggering signal to enable physiologically gated firing of x-ray radiation to minimize motion blurring. Here we report the results of phantom study of respiratory gated MRT. A simulation of mouse breathing was performed using a servo motor. Preliminary results show that without gating the micro beam full width at tenth maximum (FWTM) can increase by 70% and PVDR can decrease up to 50%. But with proper gating, both the beam width and PVDR changes can be negligible. Future experiments will involve irradiation of mouse models and comparing histology stains between the controls and the gated irradiation.

  12. Evaluation of a Gate-First Process for AlGaN/GaN Heterostructure Field-Effect Transistors

    NASA Astrophysics Data System (ADS)

    Li, Liuan; Kishi, Akinori; Shiraishi, Takayuki; Jiang, Ying; Wang, Qingpeng; Ao, Jin-Ping; Ohno, Yasuo

    2013-11-01

    In this study, we evaluated the annealing temperature and time-dependent electrical properties of AlGaN/GaN heterostructure field-effect transistors (HFETs) utilizing TiN/W/Au as the gate electrode. With the annealing temperature increasing from 750 to 900 °C for the annealing time of 1 min, the sheet resistance of TiN/W/Au films increased gradually while that of the ohmic contact was minimum (0.66 Ω mm) at 800 °C. From the current-voltage characteristics of the Schottky diode and HFETs, it is demonstrated that annealing at 800 °C showed the lowest on-resistance and highest maximum drain current. By prolonging the annealing from 0.5 to 10 min at 800 °C, good device performance was achieved when the annealing time was 1 and 3 min, while the device performance degraded showing an increased gate leakage current and gate resistance with increasing annealing time. These results demonstrated that the TiN/W/Au gate, which can withstand 800 °C annealing for a short time, is suitable for application in the gate-first process for AlGaN/GaN HFETs.

  13. Real Time Sound Field Simulator Using Field Programmable Gate Array Device

    NASA Astrophysics Data System (ADS)

    Tsuchiya, T.; Sugawara, E.; Inoguchi, Y.

    Possibility of real time simulator of three-dimensional acoustic field in the time domain is discussed. Based on the discrete Huygens' model (DHM), a digital equivalent circuit is developed. DHM elements are described by hardware description language (HDL) in the fixed-point arithmetic. It is estimated that the real time simulation of 1 m3 sound field is possible using ten-odd FPGA chips, while the CPU speed of 52 TFLOPS is required using the high performance computer. It is shown that data length of 28 bits is required for the practical accuracy. Based on FPGA-DHM, the real time simulator named "Silicon Concert Hall" may come true in the near future.

  14. Field-induced quantum metal-insulator transition in the pyrochlore iridate Nd2Ir2O7

    NASA Astrophysics Data System (ADS)

    Tian, Zhaoming; Kohama, Yoshimitsu; Tomita, Takahiro; Ishizuka, Hiroaki; Hsieh, Timothy H.; Ishikawa, Jun J.; Kindo, Koichi; Balents, Leon; Nakatsuji, Satoru

    2016-02-01

    The metal-insulator transition (MIT) is a hallmark of strong correlation in solids. Quantum MITs at zero temperature have been observed in various systems tuned by either carrier doping or bandwidth. However, such transitions have rarely been induced by application of magnetic field, as normally the field scale is too small in comparison with the charge gap, whose size is a fraction of the Coulomb repulsion energy (~1 eV). Here we report the discovery of a quantum MIT tuned by a field of ~10 T, whose magnetoresistance exceeds 60,000%. In particular, our anisotropic magnetotransport measurements on the cubic insulator Nd2Ir2O7 (ref. ) reveal that the insulating state can be suppressed by such a field to a zero-temperature quantum MIT, but only for fields near the [001] axis. The strong sensitivity to the field direction is remarkable for a cubic crystal, as is the fact that the MIT can be driven by such a small magnetic field, given the 45 meV gap energy, which is of order of 50 times the Zeeman energy for an Ir4+ spin. The systematic change in the MIT from continuous near zero field to first order under fields indicates the existence of a tricritical point proximate to the quantum MIT. We argue that these phenomena imply both strong correlation effects on the Ir electrons and an active role for the Nd spins.

  15. Electrical and chemical characterization of FIB-deposited insulators

    SciTech Connect

    Campbell, A.N.; Tanner, D.M.; Soden, J.M.; Adams, E.; Gibson, M.; Abramo, M.; Doyle, A.; Stewart, D.K.

    1997-10-01

    The electrical and chemical properties of insulators produced by codeposition of siloxane compounds or TEOS with oxygen in a focused ion beam (FIB) system were investigated. Metal-insulator-metal capacitor structures were fabricated and tested. Specifically, leakage current and breakdown voltage were measured and used to calculate the effective resistance and breakdown field. Capacitance measurements were performed on a subset of the structures. It was found that the siloxane-based FIB-insulators had superior electrical properties to those based on TEOS. Microbeam Rutherford backscattering spectrometry analysis and Fourier transform infrared spectroscopy were used to characterize the films and to help understand the differences in electrical behavior as a function of gas chemistry and deposition conditions. Finally, a comparison is made between the results presented here, previous results for FIB-deposited insulators, and typical thermally-grown gate oxides and interlevel dielectric SiO{sub 2} insulators.

  16. T-gate geometric (solution for submicrometer gate length) HEMT: Physical analysis, modeling and implementation as parasitic elements and its usage as dual gate for variable gain amplifiers

    NASA Astrophysics Data System (ADS)

    Gupta, Ritesh; Rathi, Servin; Kaur, Ravneet; Gupta, Mridula; Gupta, R. S.

    2009-03-01

    In order to achieve superior RF performance, short gate length is required for the compound semiconductor field effect transistors, but the limitation in lithography for submicrometer gate lengths leads to the formation of various metal-insulator geometries like T-gate [Sandeep R. Bahl, Jesus A. del Alamo, Physics of breakdown in InAlAs/ n +-InGaAs heterostructure field-effect transistors, IEEE Trans. Electron Devices 41 (12) (1994) 2268-2275]. These geometries are the combination of various Metal-Semiconductor (MS)/Metal-Air-Semiconductor (MAS) contacts. Moreover, field plates [S. Karmalkar, M.S. Shur, G. Simin, M. Asif Khan, Field-plate engineering for HFETs, IEEE Trans. Electron Devices 52 (2005) 2534-2540] are also being fabricated these days, mainly at the drain end ( Γ-gate) having Metal-Insulator-Semiconductor (MIS) instead of MAS contact with the intention of increasing the breakdown voltage of the device. To realize the effect of upper gate electrode in the T-gate structure and field plates, an analytical model has been proposed in the present article by dividing the whole structure into MS/MIS contact regions, applying current continuity among them and solving iteratively. The model proposed for Metal-Insulator Semiconductor High Electron Mobility Transistor (MISHEMT) [R. Gupta, S.K. Aggarwal, M. Gupta, R.S. Gupta, Analytical model for metal insulator semiconductor high electron mobility transistor (MISHEMT) for its high frequency and high power applications, J. Semicond. Technol. Sci. 6 (3) (2006) 189-198], is equally applicable to High Electron Mobility Transistors (HEMT) and has been used to formulate this model. In this paper, various structures and geometries have been compared to anticipate the need of T-gate modeling. The effect of MIS contacts has been implemented as parasitic resistance and capacitance and has also been studied to control the middle conventional gate as in dual gate technology by applying separate voltages across it. The results

  17. Building America Case Study: Field Testing an Unvented Roof with Fibrous Insulation and Tiles, Orlando, Florida

    SciTech Connect

    2015-11-01

    This research is a test implementation of an unvented tile roof assembly in a hot-humid climate (Orlando, FL; Zone 2A), insulated with air permeable insulation (netted and blown fiberglass). Given the localized moisture accumulation and failures seen in previous unvented roof field work, it was theorized that a 'diffusion vent' (water vapor open, but air barrier 'closed') at the highest points in the roof assembly might allow for the wintertime release of moisture, to safe levels. The 'diffusion vent' is an open slot at the ridge and hips, covered with a water-resistant but vapor open (500+ perm) air barrier membrane. As a control comparison, one portion of the roof was constructed as a typical unvented roof (self-adhered membrane at ridge). The data collected to date indicate that the diffusion vent roof shows greater moisture safety than the conventional, unvented roof design. The unvented roof had extended winter periods of 95-100% RH, and wafer (wood surrogate RH sensor) measurements indicating possible condensation; high moisture levels were concentrated at the roof ridge. In contrast, the diffusion vent roofs had drier conditions, with most peak MCs (sheathing) below 20%. In the spring, as outdoor temperatures warmed, all roofs dried well into the safe range (10% MC or less). Some roof-wall interfaces showed moderately high MCs; this might be due to moisture accumulation at the highest point in the lower attic, and/or shading of the roof by the adjacent second story. Monitoring will be continued at least through spring 2016 (another winter and spring).

  18. Gating capacitive field-effect sensors by the charge of nanoparticle/molecule hybrids

    NASA Astrophysics Data System (ADS)

    Poghossian, Arshak; Bäcker, Matthias; Mayer, Dirk; Schöning, Michael J.

    2014-12-01

    The semiconductor field-effect platform is a powerful tool for chemical and biological sensing with direct electrical readout. In this work, the field-effect capacitive electrolyte-insulator-semiconductor (EIS) structure - the simplest field-effect (bio-)chemical sensor - modified with citrate-capped gold nanoparticles (AuNPs) has been applied for a label-free electrostatic detection of charged molecules by their intrinsic molecular charge. The EIS sensor detects the charge changes in AuNP/molecule inorganic/organic hybrids induced by the molecular adsorption or binding events. The feasibility of the proposed detection scheme has been exemplarily demonstrated by realizing capacitive EIS sensors consisting of an Al-p-Si-SiO2-silane-AuNP structure for the label-free detection of positively charged cytochrome c and poly-d-lysine molecules as well as for monitoring the layer-by-layer formation of polyelectrolyte multilayers of poly(allylamine hydrochloride)/poly(sodium 4-styrene sulfonate), representing typical model examples of detecting small proteins and macromolecules and the consecutive adsorption of positively/negatively charged polyelectrolytes, respectively. For comparison, EIS sensors without AuNPs have been investigated, too. The adsorption of molecules on the surface of AuNPs has been verified via the X-ray photoelectron spectroscopy method. In addition, a theoretical model of the functioning of the capacitive field-effect EIS sensor functionalized with AuNP/charged-molecule hybrids has been discussed.The semiconductor field-effect platform is a powerful tool for chemical and biological sensing with direct electrical readout. In this work, the field-effect capacitive electrolyte-insulator-semiconductor (EIS) structure - the simplest field-effect (bio-)chemical sensor - modified with citrate-capped gold nanoparticles (AuNPs) has been applied for a label-free electrostatic detection of charged molecules by their intrinsic molecular charge. The EIS sensor

  19. Metrology solutions using optical scatterometry for advanced CMOS: III-V and Germanium multi-gate field-effect transistors

    NASA Astrophysics Data System (ADS)

    Chin, Hock-Chun; Liu, Bin; Zhang, Xingui; Ling, Moh-Lung; Yip, Chan-Hoe; Liu, Yongdong; Hu, Jiangtao; Yeo, Yee-Chia

    2013-04-01

    In this work, we report metrology solutions using scatterometry Optical Critical Dimension (OCD) characterization on two advanced CMOS devices: novel n-channel gate-last In0.53Ga0.47As FinFET with self-aligned Molybdenum (Mo) contacts and p-channel Ge FinFET formed on Germanium-on-Insulator (GOI) substrate. Key critical process steps during the fabrication of these advanced transistors were identified for process monitor using scatterometry OCD measurement to improve final yield. Excellent correlation with reference metrology and high measurement precision were achieved by using OCD characterization, confirming scatterometry OCD as a promising metrology technique for next generation device applications. In addition, we also further explore OCD characterization using normal incidence spectroscopic reflectometry (SR), oblique incidence spectroscopic ellipsometry (SE), and combined SR+SE technologies. The combined SR+SE approach was found to provide better precision.

  20. Role of the dielectric for the charging dynamics of the dielectric/barrier interface in AlGaN/GaN based metal-insulator-semiconductor structures under forward gate bias stress

    SciTech Connect

    Lagger, P.; Steinschifter, P.; Reiner, M.; Stadtmüller, M.; Denifl, G.; Ostermaier, C.; Naumann, A.; Müller, J.; Wilde, L.; Sundqvist, J.; Pogany, D.

    2014-07-21

    The high density of defect states at the dielectric/III-N interface in GaN based metal-insulator-semiconductor structures causes tremendous threshold voltage drifts, ΔV{sub th}, under forward gate bias conditions. A comprehensive study on different dielectric materials, as well as varying dielectric thickness t{sub D} and barrier thickness t{sub B}, is performed using capacitance-voltage analysis. It is revealed that the density of trapped electrons, ΔN{sub it}, scales with the dielectric capacitance under spill-over conditions, i.e., the accumulation of a second electron channel at the dielectric/AlGaN barrier interface. Hence, the density of trapped electrons is defined by the charging of the dielectric capacitance. The scaling behavior of ΔN{sub it} is explained universally by the density of accumulated electrons at the dielectric/III-N interface under spill-over conditions. We conclude that the overall density of interface defects is higher than what can be electrically measured, due to limits set by dielectric breakdown. These findings have a significant impact on the correct interpretation of threshold voltage drift data and are of relevance for the development of normally off and normally on III-N/GaN high electron mobility transistors with gate insulation.

  1. Wide-field time-gated photoluminescence microscopy for fast ultrahigh-sensitivity imaging of photoluminescent probes.

    PubMed

    Razali, Wan A W; Sreenivasan, Varun K A; Bradac, Carlo; Connor, Mark; Goldys, Ewa M; Zvyagin, Andrei V

    2016-08-01

    Fluorescence microscopy is a fundamental technique for the life sciences, where biocompatible and photostable photoluminescence probes in combination with fast and sensitive imaging systems are continually transforming this field. A wide-field time-gated photoluminescence microscopy system customised for ultrasensitive imaging of unique nanoruby probes with long photoluminescence lifetime is described. The detection sensitivity derived from the long photoluminescence lifetime of the nanoruby makes it possible to discriminate signals from unwanted autofluorescence background and laser backscatter by employing a time-gated image acquisition mode. This mode enabled several-fold improvement of the photoluminescence imaging contrast of discrete nanorubies dispersed on a coverslip. It enabled recovery of the photoluminescence signal emanating from discrete nanorubies when covered by a layer of an organic fluorescent dye, which were otherwise invisible without the use of spectral filtering approaches. Time-gated imaging also facilitated high sensitivity detection of nanorubies in a biological environment of cultured cells. Finally, we monitor the binding kinetics of nanorubies to a functionalised substrate, which exemplified a real-time assay in biological fluids. 3D-pseudo colour images of nanorubies immersed in a highly fluorescent dye solution. Nanoruby photoluminescence is subdued by that of the dye in continuous excitation/imaging (left), however it can be recovered by time-gated imaging (right). At the bottom is schematic diagram of nanoruby assay in a biological fluid. PMID:27264934

  2. Hysteresis behaviour of low-voltage organic field-effect transistors employing high dielectric constant polymer gate dielectrics

    NASA Astrophysics Data System (ADS)

    Kim, Se Hyun; Yun, Won Min; Kwon, Oh-Kwan; Hong, Kipyo; Yang, Chanwoo; Choi, Woon-Seop; Eon Park, Chan

    2010-11-01

    Here, we report on the fabrication of low-voltage-operating pentacene-based organic field-effect transistors (OFETs) that utilize crosslinked cyanoethylated poly(vinyl alcohol) (CR-V) gate dielectrics. The crosslinked CR-V-based OFET could be operated successfully at low voltages (below 4 V), but abnormal behaviour during device operation, such as uncertainty in the field-effect mobility (μ) and hysteresis, was induced by the slow polarization of moieties embedded in the gate dielectric (e.g. polar functionalities, ionic impurities, water and solvent molecules). In an effort to improve the stability of OFET operation, we measured the dependence of μ and hysteresis on dielectric thickness, CR-V crosslinking conditions and sweep rate of the gate bias. The influence of the CR-V surface properties on μ, hysteresis, and the structural and morphological features of the pentacene layer grown on the gate dielectric was characterized and compared with the properties of pentacene grown on a polystyrene surface.

  3. Dielectric strength, swelling and weight loss of the ITER Toroidal Field Model Coil insulation after low temperature reactor irradiation

    NASA Astrophysics Data System (ADS)

    Humer, K.; Weber, H. W.; Hastik, R.; Hauser, H.; Gerstenberg, H.

    2000-04-01

    The insulation system for the Toroidal Field Model Coil of ITER is a fiber reinforced plastic (FRP) laminate, which consists of a combined Kapton/R-glass-fiber reinforcement tape, vacuum-impregnated with an epoxy DGEBA system. Pure disk shaped laminates, FRP/stainless-steel sandwiches, and conductor insulation prototypes were irradiated at 5 K in a fission reactor up to a fast neutron fluence of 10 22 m -2 ( E>0.1 MeV) to investigate the radiation induced degradation of the dielectric strength of the insulation system. After warm-up to room temperature, swelling, weight loss, and the breakdown strength were measured at 77 K. The sandwich swells by 4% at a fluence of 5×10 21 m-2 and by 9% at 1×10 22 m-2. The weight loss of the FRP is 2% at 1×10 22 m-2. The dielectric strength remained unchanged over the whole dose range.

  4. Electronic Excitations and Metal-Insulator Transition inPoly(3-hexylthiophene) Organic Field-Effect Transistors

    SciTech Connect

    Sai, N.; Li, Z.Q.; Martin, M.C.; Basov, D.N.; Di Ventra, M.

    2006-11-07

    We carry out a comprehensive theoretical and experimentalstudy of charge injection in poly(3-hexylthiophene) (P3HT) to determinethe most likely scenario for metal-insulator transition in this system.Wecalculate the optical-absorption frequencies corresponding to a polaronand a bipolaron lattice in P3HT. We also analyze the electronicexcitations for three possible scenarios under which a first- or asecond-order metal-insulator transition can occur in doped P3HT. Thesetheoretical scenarios are compared with data from infrared absorptionspectroscopy on P3HT thin-film field-effect transistors (FETs). Ourmeasurements and theoretical predictions suggest that charge-inducedlocalized states in P3HT FETs are bipolarons and that the highest dopinglevel achieved in our experiments approaches that required for afirst-order metal-insulator transition.

  5. On Field-Effect Photovoltaics: Gate Enhancement of the Power Conversion Efficiency in a Nanotube/Silicon-Nanowire Solar Cell.

    PubMed

    Petterson, Maureen K; Lemaitre, Maxime G; Shen, Yu; Wadhwa, Pooja; Hou, Jie; Vasilyeva, Svetlana V; Kravchenko, Ivan I; Rinzler, Andrew G

    2015-09-30

    Recent years have seen a resurgence of interest in crystalline silicon Schottky junction solar cells distinguished by the use of low density of electronic states (DOS) nanocarbons (nanotubes, graphene) as the metal contacting the Si. Recently, unprecedented modulation of the power conversion efficiency in a single material system has been demonstrated in such cells by the use of electronic gating. The gate field induced Fermi level shift in the low-DOS carbon serves to enhance the junction built-in potential, while a gate field induced inversion layer at the Si surface, in regions remote from the junction, keeps the photocarriers well separated there, avoiding recombination at surface traps and defects (a key loss mechanism). Here, we extend these results into the third dimension of a vertical Si nanowire array solar cell. A single wall carbon nanotube layer engineered to contact virtually each n-Si nanowire tip extracts the minority carriers, while an ionic liquid electrolytic gate drives the nanowire body into inversion. The enhanced light absorption of the vertical forest cell, at 100 mW/cm(2) AM1.5G illumination, results in a short-circuit current density of 35 mA/cm(2) and associated power conversion efficiency of 15%. These results highlight the use of local fields as opposed to surface passivation as a means of avoiding front surface recombination. A deleterious electrochemical reaction of the silicon due to the electrolyte gating is shown to be caused by oxygen/water entrained in the ionic liquid electrolyte. While encapsulation can avoid the issue, a nonencapsulation-based approach is also implemented. PMID:26352052

  6. On Field-Effect Photovoltaics: Gate Enhancement of the Power Conversion Efficiency in a Nanotube/Silicon-Nanowire Solar Cell

    DOE PAGESBeta

    Petterson, Maureen K.; Lemaitre, Maxime G.; Shen, Yu; Wadhwa, Pooja; Hou, Jie; Vasilyeva, Svetlana V.; Kravchenko, Ivan I.; Rinzler, Andrew G.

    2015-09-09

    Recent years have seen a resurgence of interest in crystalline silicon Schottky junction solar cells distinguished by the use of low density of electronic states (DOS) nanocarbons (nanotubes, graphene) as the metal contacting the Si. Recently, unprecedented modulation of the power conversion efficiency in a single material system has been demonstrated in such cells by the use of electronic gating. The gate field induced Fermi level shift in the low-DOS carbon serves to enhance the junction built-in potential, while a gate field induced inversion layer at the Si surface, in regions remote from the junction, keeps the photocarriers well separatedmore » there, avoiding recombination at surface traps and defects (a key loss mechanism). Here, we extend these results into the third dimension of a vertical Si nanowire array solar cell. A single wall carbon nanotube layer engineered to contact virtually each n-Si nanowire tip extracts the minority carriers, while an ionic liquid electrolytic gate drives the nanowire body into inversion. The enhanced light absorption of the vertical forest cell, at 100 mW/cm2 AM1.5G illumination, results in a short-circuit current density of 35 mA/cm2 and associated power conversion efficiency of 15%. These results highlight the use of local fields as opposed to surface passivation as a means of avoiding front surface recombination. Finally, a deleterious electrochemical reaction of the silicon due to the electrolyte gating is shown to be caused by oxygen/water entrained in the ionic liquid electrolyte. While encapsulation can avoid the issue, a nonencapsulation-based approach is also implemented.« less

  7. On Field-Effect Photovoltaics: Gate Enhancement of the Power Conversion Efficiency in a Nanotube/Silicon-Nanowire Solar Cell

    SciTech Connect

    Petterson, Maureen K.; Lemaitre, Maxime G.; Shen, Yu; Wadhwa, Pooja; Hou, Jie; Vasilyeva, Svetlana V.; Kravchenko, Ivan I.; Rinzler, Andrew G.

    2015-09-09

    Recent years have seen a resurgence of interest in crystalline silicon Schottky junction solar cells distinguished by the use of low density of electronic states (DOS) nanocarbons (nanotubes, graphene) as the metal contacting the Si. Recently, unprecedented modulation of the power conversion efficiency in a single material system has been demonstrated in such cells by the use of electronic gating. The gate field induced Fermi level shift in the low-DOS carbon serves to enhance the junction built-in potential, while a gate field induced inversion layer at the Si surface, in regions remote from the junction, keeps the photocarriers well separated there, avoiding recombination at surface traps and defects (a key loss mechanism). Here, we extend these results into the third dimension of a vertical Si nanowire array solar cell. A single wall carbon nanotube layer engineered to contact virtually each n-Si nanowire tip extracts the minority carriers, while an ionic liquid electrolytic gate drives the nanowire body into inversion. The enhanced light absorption of the vertical forest cell, at 100 mW/cm2 AM1.5G illumination, results in a short-circuit current density of 35 mA/cm2 and associated power conversion efficiency of 15%. These results highlight the use of local fields as opposed to surface passivation as a means of avoiding front surface recombination. Finally, a deleterious electrochemical reaction of the silicon due to the electrolyte gating is shown to be caused by oxygen/water entrained in the ionic liquid electrolyte. While encapsulation can avoid the issue, a nonencapsulation-based approach is also implemented.

  8. A new analytical threshold voltage model for symmetrical double-gate MOSFETs with high- k gate dielectrics

    NASA Astrophysics Data System (ADS)

    Chiang, T. K.; Chen, M. L.

    2007-03-01

    Based on the fully two-dimensional (2D) Poisson's solution in both silicon film and insulator layer, a compact and analytical threshold voltage model, which accounts for the fringing field effect of the short channel symmetrical double-gate (SDG) MOSFETs, has been developed. Exploiting the new model, a concerned analysis combining FIBL-enhanced short-channel effects and high- k gate dielectrics assess their overall impact on SDG MOSFET's scaling. It is found that for the same equivalent oxide thickness, the gate insulator with high- k dielectric constant which keeps a great characteristic length allows less design space than SiO 2 to sustain the same FIBL induced threshold voltage degradation.

  9. Technology Solutions Case Study: Field Testing an Unvented Roof with Fibrous Insulation and Tiles

    SciTech Connect

    2015-11-01

    This case study by the U.S. Department of Energy’s Building America research team Building Science Corporation is a test implementation of an unvented tile roof assembly in a hot-humid climate (Orlando, Florida; zone 2A), insulated with air-permeable insulation (netted and blown fiberglass).

  10. Modeling of Gate Bias Modulation in Carbon Nanotube Field-Effect-Transistors

    NASA Technical Reports Server (NTRS)

    Yamada, Toshishige; Biegel, Bryan (Technical Monitor)

    2002-01-01

    The threshold voltages of a carbon nanotube (CNT) field-effect transistor (FET) are derived and compared with those of the metal oxide-semiconductor (MOS) FETs. The CNT channel is so thin that there is no voltage drop perpendicular to the gate electrode plane, which is the CNT diameter direction, and this makes the CNTFET characteristics quite different from those in MOSFETs. The relation between the voltage and the electrochemical potentials, and the mass action law for electrons and holes are examined in the context of CNTs, and it is shown that the familiar relations are still valid because of the macroscopic number of states available in the CNTs. This is in sharp contrast to the cases of quantum dots. Using these relations, we derive an inversion threshold voltage V(sub Ti) and an accumulation threshold voltage V(sub Ta) as a function of the Fermi level E(sub F) in the channel, where E(sub F) is a measure of channel doping. V(sub Ti) of the CNTFETs has a much stronger dependence than that of MOSFETs, while V(sub Ta)s of both CNTFETs and MOSFETs depend quite weakly on E(sub F) with the same functional form. This means the transition from normally-off mode to normally-on mode is much sharper in CNTFETs as the doping increases, and this property has to be taken into account in circuit design.

  11. A Self-Timed Multipurpose Delay Sensor for Field Programmable Gate Arrays (FPGAs)

    PubMed Central

    Osuna, Carlos Gómez; Ituero, Pablo; López-Vallejo, Marisa

    2014-01-01

    This paper presents a novel self-timed multi-purpose sensor especially conceived for Field Programmable Gate Arrays (FPGAs). The aim of the sensor is to measure performance variations during the life-cycle of the device, such as process variability, critical path timing and temperature variations. The proposed topology, through the use of both combinational and sequential FPGA elements, amplifies the time of a signal traversing a delay chain to produce a pulse whose width is the sensor's measurement. The sensor is fully self-timed, avoiding the need for clock distribution networks and eliminating the limitations imposed by the system clock. One single off- or on-chip time-to-digital converter is able to perform digitization of several sensors in a single operation. These features allow for a simplified approach for designers wanting to intertwine a multi-purpose sensor network with their application logic. Employed as a temperature sensor, it has been measured to have an error of ±0.67 °C, over the range of 20–100 °C, employing 20 logic elements with a 2-point calibration. PMID:24361927

  12. A self-timed multipurpose delay sensor for Field Programmable Gate Arrays (FPGAs).

    PubMed

    Osuna, Carlos Gómez; Ituero, Pablo; López-Vallejo, Marisa

    2013-01-01

    This paper presents a novel self-timed multi-purpose sensor especially conceived for Field Programmable Gate Arrays (FPGAs). The aim of the sensor is to measure performance variations during the life-cycle of the device, such as process variability, critical path timing and temperature variations. The proposed topology, through the use of both combinational and sequential FPGA elements, amplifies the time of a signal traversing a delay chain to produce a pulse whose width is the sensor's measurement. The sensor is fully self-timed, avoiding the need for clock distribution networks and eliminating the limitations imposed by the system clock. One single off- or on-chip time-to-digital converter is able to perform digitization of several sensors in a single operation. These features allow for a simplified approach for designers wanting to intertwine a multi-purpose sensor network with their application logic. Employed as a temperature sensor, it has been measured to have an error of  ±0.67 °C, over the range of 20-100 °C, employing 20 logic elements with a 2-point calibration. PMID:24361927

  13. Single Event Effects Test Results for Advanced Field Programmable Gate Arrays

    NASA Technical Reports Server (NTRS)

    Allen, Gregory R.; Swift, Gary M.

    2006-01-01

    Reconfigurable Field Programmable Gate Arrays (FPGAs) from Altera and Actel and an FPGA-based quick-turnApplication Specific Integrated Circuit (ASIC) from Altera were subjected to single-event testing using heavy ions. Both Altera devices (Stratix II and HardCopy II) exhibited a low latchup threshold (below an LET of 3 MeV-cm2/mg) and thus are not recommended for applications in the space radiation environment. The flash-based Actel ProASIC Plus device did not exhibit latchup to an effective LET of 75 MeV-cm2/mg at room temperature. In addition, these tests did not show flash cell charge loss (upset) or retention damage. Upset characterization of the design-level flip-flops yielded an LET threshold below 10 MeV-cm2/mg and a high LET cross section of about lxlO-6 cm2/bit for storing ones and about lxl0-7 cm2/bit for storing zeros . Thus, the ProASIC device may be suitable for critical flight applications with appropriate triple modular redundancy mitigation techniques.

  14. Real-time processing for Fourier domain optical coherence tomography using a field programmable gate array

    PubMed Central

    Ustun, Teoman E.; Iftimia, Nicusor V.; Ferguson, R. Daniel; Hammer, Daniel X.

    2008-01-01

    Real-time display of processed Fourier domain optical coherence tomography (FDOCT) images is important for applications that require instant feedback of image information, for example, systems developed for rapid screening or image-guided surgery. However, the computational requirements for high-speed FDOCT image processing usually exceeds the capabilities of most computers and therefore display rates rarely match acquisition rates for most devices. We have designed and developed an image processing system, including hardware based upon a field programmable gated array, firmware, and software that enables real-time display of processed images at rapid line rates. The system was designed to be extremely flexible and inserted in-line between any FDOCT detector and any Camera Link frame grabber. Two versions were developed for spectrometer-based and swept source-based FDOCT systems, the latter having an additional custom high-speed digitizer on the front end but using all the capabilities and features of the former. The system was tested in humans and monkeys using an adaptive optics retinal imager, in zebrafish using a dual-beam Doppler instrument, and in human tissue using a swept source microscope. A display frame rate of 27 fps for fully processed FDOCT images (1024 axial pixels×512 lateral A-scans) was achieved in the spectrometer-based systems. PMID:19045902

  15. Evaluation of an interdigitated gate electrode field-effect transistor for detecting organophosphorus compounds

    NASA Astrophysics Data System (ADS)

    Brothers, Charles P., Jr.

    1990-12-01

    This study used integrated circuit microsensors to detect organophosphorus compounds. Chemically-sensitive thin films, copper phthalocyanine, DFPase, succinyl chloride, succinylcholine chloride, 2-naphthol(B), and L-histidine dihydrochloride, were deposited on interdigitated gate electrode (IGE) structures, with an average thickness of 2000 A. Thin film electrical performance characteristics were measured for several parameters, including: dc resistance, ac impedance, time-domain, and spectral responses from 10 Hz to 1 MHz. Each microsensor contained nine IGEs; each IGE possessed an in situ field-effect transistor amplifier. After purging each sensor with filtered air, it was exposed to one or two of the following gases: diisopropyl fluorophosphate (DFP), diisopropyl methylphosphonate, and dimethyl methylphosphonate at concentrations spanning 100 ppb to 10 ppm (at 90 percent relative humidity and 23 C). Testing was conducted with microsensors heated to 30, 50, and 70 C. All six candidate films, demonstrated various degrees of sensitivity to the challenge gases at 30 C. DFPase was especially sensitive to the challenge gases at 100 ppb. Only copper phthalocyanine and L-histidine dihydrochloride demonstrated sensitivity above 30 C. In particular, 2-naphthol(beta) showed complete reversibility and succinyl chloride demonstrated partial reversibility at 30 C. Copper phthalocyanine was reversible only at 70 C. Succinylcholine chloride demonstrated a unique band-reject filter response to the presence of DFP in any challenge gas sample presented to the sensor.

  16. Configuration and debug of field programmable gate arrays using MATLAB®/SIMULINK®

    NASA Astrophysics Data System (ADS)

    Grout, I.; Ryan, J.; O'Shea, T.

    2005-01-01

    Increasingly, the need to seamlessly link high-level behavioural descriptions of electronic hardware for modelling and simulation purposes to the final application hardware highlights the gap between the high-level behavioural descriptions of the required circuit functionality (considering here digital logic) in commonly used mathematical modelling tools, and the hardware description languages such as VHDL and Verilog-HDL. In this paper, the linking of a MATLAB® model for digital algorithm for implementation on a programmable logic device for design synthesis from the MATLAB® model into VHDL is discussed. This VHDL model is itself synthesised and downloaded to the target Field Programmable Gate Array, for normal operation and also for design debug purposes. To demonstrate this, a circuit architecture mapped from a SIMULINK® model is presented. The rationale is for a seamless interface between the initial algorithm development and the target hardware, enabling the hardware to be debugged and compared to the simulated model from a single interface for use with by a non-expert in the programmable logic and hardware description language use.

  17. Evaluation of soft-core processors on a Xilinx Virtex-5 field programmable gate array.

    SciTech Connect

    Learn, Mark Walter

    2011-04-01

    Node-based architecture (NBA) designs for future satellite projects hold the promise of decreasing system development time and costs, size, weight, and power and positioning the laboratory to address other emerging mission opportunities quickly. Reconfigurable field programmable gate array (FPGA)-based modules will comprise the core of several of the NBA nodes. Microprocessing capabilities will be necessary with varying degrees of mission-specific performance requirements on these nodes. To enable the flexibility of these reconfigurable nodes, it is advantageous to incorporate the microprocessor into the FPGA itself, either as a hard-core processor built into the FPGA or as a soft-core processor built out of FPGA elements. This document describes the evaluation of three reconfigurable FPGA-based soft-core processors for use in future NBA systems: the MicroBlaze (uB), the open-source Leon3, and the licensed Leon3. Two standard performance benchmark applications were developed for each processor. The first, Dhrystone, is a fixed-point operation metric. The second, Whetstone, is a floating-point operation metric. Several trials were run at varying code locations, loop counts, processor speeds, and cache configurations. FPGA resource utilization was recorded for each configuration.

  18. Modular design and implementation of field-programmable-gate-array-based Gaussian noise generator

    NASA Astrophysics Data System (ADS)

    Li, Yuan-Ping; Lee, Ta-Sung; Hwang, Jeng-Kuang

    2016-05-01

    The modular design of a Gaussian noise generator (GNG) based on field-programmable gate array (FPGA) technology was studied. A new range reduction architecture was included in a series of elementary function evaluation modules and was integrated into the GNG system. The approximation and quantisation errors for the square root module with a first polynomial approximation were high; therefore, we used the central limit theorem (CLT) to improve the noise quality. This resulted in an output rate of one sample per clock cycle. We subsequently applied Newton's method for the square root module, thus eliminating the need for the use of the CLT because applying the CLT resulted in an output rate of two samples per clock cycle (>200 million samples per second). Two statistical tests confirmed that our GNG is of high quality. Furthermore, the range reduction, which is used to solve a limited interval of the function approximation algorithms of the System Generator platform using Xilinx FPGAs, appeared to have a higher numerical accuracy, was operated at >350 MHz, and can be suitably applied for any function evaluation.

  19. Double gate graphene nanoribbon field effect transistor with single halo pocket in channel region

    NASA Astrophysics Data System (ADS)

    Naderi, Ali

    2016-01-01

    A new structure for graphene nanoribbon field-effect transistors (GNRFETs) is proposed and investigated using quantum simulation with a nonequilibrium Green's function (NEGF) method. Tunneling leakage current and ambipolar conduction are known effects for MOSFET-like GNRFETs. To minimize these issues a novel structure with a simple change of the GNRFETs by using single halo pocket in the intrinsic channel region, "Single Halo GNRFET (SH-GNRFET)", is proposed. An appropriate halo pocket at source side of channel is used to modify potential distribution of the gate region and weaken band to band tunneling (BTBT). In devices with materials like Si in channel region, doping type of halo and source/drain regions are different. But, here, due to the smaller bandgap of graphene, the mentioned doping types should be the same to reduce BTBT. Simulations have shown that in comparison with conventional GNRFET (C-GNRFET), an SH-GNRFET with appropriately halo doping results in a larger ON current (Ion), smaller OFF current (Ioff), a larger ON-OFF current ratio (Ion/Ioff), superior ambipolar characteristics, a reduced power-delay product and lower delay time.

  20. Large-scale sensor systems based on graphene electrolyte-gated field-effect transistors.

    PubMed

    Mackin, Charles; Palacios, Tomás

    2016-04-25

    This work reports a novel graphene electrolyte-gated field-effect transistor (EGFET) array architecture along with a compact, self-contained, and inexpensive measurement system that allows DC characterization of hundreds of graphene EGFETs as a function of VDS and VGS within a matter of minutes. We develop a reliable graphene EGFET fabrication process capable of producing 100% yield for a sample size of 256 devices. Large sample size statistical analysis of graphene EGFET electrical performance is performed for the first time. This work develops a compact piecewise DC model for graphene EGFETs that is shown capable of fitting 87% of IDSvs. VGS curves with a mean percent error of 7% or less. The model is used to extract variations in device parameters such as mobility, contact resistance, minimum carrier concentration, and Dirac point. Correlations in variations are presented. Lastly, this work presents a framework for application-specific optimization of large-scale sensor designs based on graphene EGFETs. PMID:26788552

  1. Development and simulation of soft morphological operators for a field programmable gate array

    NASA Astrophysics Data System (ADS)

    Tickle, Andrew J.; Harvey, Paul K.; Smith, Jeremy S.; Wu, Q. Henry

    2013-04-01

    In image processing applications, soft mathematical morphology (MM) can be employed for both binary and grayscale systems and is derived from set theory. Soft MM techniques have improved behavior over standard morphological operations in noisy environments, as they can preserve small details within an image. This makes them suitable for use in image processing applications on portable field programmable gate arrays for tasks such as robotics and security. We explain how the systems were developed using Altera's DSP Builder in order to provide optimized code for the many different devices currently on the market. Also included is how the circuits can be inserted and combined with previously developed work in order to increase their functionality. The testing procedures involved loading different images into these systems and analyzing the outputs against MATLAB-generated validation images. A set of soft morphological operations are described, which can then be applied to various tasks and easily modified in size via altering the line buffer settings inside the system to accommodate a range of image attributes ranging from image sizes such as 320×240 pixels for basic webcam imagery up to high quality 4000×4000 pixel images for military applications.

  2. Measurements of the velocity fields by PIV method round about titling gate

    NASA Astrophysics Data System (ADS)

    Mistrová, Ivana; Zubík, Pavel

    2012-04-01

    The article deals with problems of using of measurement method Particle Image Velocimetry (PIV) to measure velocity fields in the flowing water in front, above and behind drowned titling weir gate. The aim was to obtain information about the distribution of speed in the area of interest for the verification or calibration of the numerical model. Experiments were carried out in inclinable channel connected to the hydraulic circuit with a pump and storage tank at the Water Management Research Laboratory (LVV) of Institute of Water Structures at the Faculty of Civil Engineering in Brno University of Technology. Hydraulic inclinable channel has cross-section with dimensions of 0.4×0.4m and length of 12.5m. The measured area has cross-section approximately 0.2m wide and 0.4m high and its length is 1m. The results of physical modelling allowed a comparison of experimental data with numerical simulation results of this type of flow in the commercial software ANSYS CFX-12.0.

  3. Gate-Sensing Coherent Charge Oscillations in a Silicon Field-Effect Transistor.

    PubMed

    Gonzalez-Zalba, M Fernando; Shevchenko, Sergey N; Barraud, Sylvain; Johansson, J Robert; Ferguson, Andrew J; Nori, Franco; Betz, Andreas C

    2016-03-01

    Quantum mechanical effects induced by the miniaturization of complementary metal-oxide-semiconductor (CMOS) technology hamper the performance and scalability prospects of field-effect transistors. However, those quantum effects, such as tunneling and coherence, can be harnessed to use existing CMOS technology for quantum information processing. Here, we report the observation of coherent charge oscillations in a double quantum dot formed in a silicon nanowire transistor detected via its dispersive interaction with a radio frequency resonant circuit coupled via the gate. Differential capacitance changes at the interdot charge transitions allow us to monitor the state of the system in the strong-driving regime where we observe the emergence of Landau-Zener-Stückelberg-Majorana interference on the phase response of the resonator. A theoretical analysis of the dispersive signal demonstrates that quantum and tunneling capacitance changes must be included to describe the qubit-resonator interaction. Furthermore, a Fourier analysis of the interference pattern reveals a charge coherence time, T2 ≈ 100 ps. Our results demonstrate charge coherent control and readout in a simple silicon transistor and open up the possibility to implement charge and spin qubits in existing CMOS technology. PMID:26866446

  4. Solution-deposited sodium beta-alumina gate dielectrics for low-voltage and transparent field-effect transistors.

    PubMed

    Pal, Bhola N; Dhar, Bal Mukund; See, Kevin C; Katz, Howard E

    2009-11-01

    Sodium beta-alumina (SBA) has high two-dimensional conductivity, owing to mobile sodium ions in lattice planes, between which are insulating AlO(x) layers. SBA can provide high capacitance perpendicular to the planes, while causing negligible leakage current owing to the lack of electron carriers and limited mobility of sodium ions through the aluminium oxide layers. Here, we describe sol-gel-beta-alumina films as transistor gate dielectrics with solution-deposited zinc-oxide-based semiconductors and indium tin oxide (ITO) gate electrodes. The transistors operate in air with a few volts input. The highest electron mobility, 28.0 cm2 V(-1) s(-1), was from zinc tin oxide (ZTO), with an on/off ratio of 2 x 10(4). ZTO over a lower-temperature, amorphous dielectric, had a mobility of 10 cm2 V(-1) s(-1). We also used silicon wafer and flexible polyimide-aluminium foil substrates for solution-processed n-type oxide and organic transistors. Using poly(3,4-ethylenedioxythiophene) poly(styrenesulphonate) conducting polymer electrodes, we prepared an all-solution-processed, low-voltage transparent oxide transistor on an ITO glass substrate. PMID:19838183

  5. A facile route for the fabrication of large-scale gate-all-around nanofluidic field-effect transistors with low leakage current.

    PubMed

    Shin, Sangwoo; Kim, Beom Seok; Song, Jiwoon; Lee, Hwanseong; Cho, Hyung Hee

    2012-07-21

    Active modulation of ions and molecules via field-effect gating in nanofluidic channels is a crucial technology for various promising applications such as DNA sequencing, drug delivery, desalination, and energy conversion. Developing a rapid and facile fabrication method for ionic field-effect transistors (FET) over a large area may offer exciting opportunities for both fundamental research and innovative applications. Here, we report a rapid, cost-effective route for the fabrication of large-scale nanofluidic field-effect transistors using a simple, lithography-free two-step fabrication process that consists of sputtering and barrier-type anodization. A robust alumina gate dielectric layer, which is formed by anodizing sputtered aluminium, can be rapidly fabricated in the order of minutes. When anodizing aluminium, we employ a hemispherical counter electrode in order to give a uniform electric field that encompasses the whole sputtered aluminium layer which has high surface roughness. In consequence, a well-defined thin layer of alumina with perfect step coverage is formed on a highly rough aluminium surface. A gate-all-around nanofluidic FET with a leak-free gate dielectric exhibits outstanding gating performance despite a large channel size. The thin and robust anodized alumina gate dielectric plays a crucial role in achieving such excellent capacitive coupling. The combination of a gate-all-around structure with a leak-free gate dielectric over a large area could yield breakthroughs in areas ranging from biotechnology to energy and environmental applications. PMID:22584915

  6. Complementary GaAs junction-gated heterostructure field effect transistor technology

    SciTech Connect

    Baca, A.G.; Zolper, J.C.; Sherwin, M.E.; Robertson, P.J.; Shul, R.J.; Howard, A.J.; Rieger, D.J.; Klem, J.F.

    1994-09-01

    The first circuit results for a new GaAs complementary logic technology are presented. The technology allows for Independently optimizable p- and n- channel transistors with junction gates. Excellent loaded gate delays of 179 ps at 1.2 V and 319 ps at 0.8 V have been demonstrated at low power supply voltages. A power-delay product of 8.9 fJ was obtained at 0.8 V.

  7. Four allotropes of semiconducting layered arsenic that switch into a topological insulator via an electric field: Computational study

    NASA Astrophysics Data System (ADS)

    Mardanya, Sougata; Thakur, Vinay Kumar; Bhowmick, Somnath; Agarwal, Amit

    2016-07-01

    We propose four different thermodynamically stable structural phases of arsenic monolayers based on ab initio density functional theory calculations, all of which undergo a topological phase transition on application of a perpendicular electric field. All four arsenic monolayer allotropes have a wide band gap, varying from 1.21 to 3.0 eV (based on GW calculations), and in general they undergo a metal-insulator quantum phase transition on application of uniaxial in-layer strain. Additionally, an increasing transverse electric field induces band inversion at the Γ point in all four monolayer allotropes, leading to a nontrivial topological phase (insulating for three allotropes and metallic for one allotrope), characterized by the switching of the Z2 index from 0 (before band inversion) to 1 (after band inversion). The topological phase tuned by the transverse electric field should support spin-separated gapless edge states which should manifest in the quantum spin Hall effect.

  8. A color graphics display of the field intensity around the insulator on 13. 2 kv distribution lines

    SciTech Connect

    Yamashita, H.; Nakamae, E. ); Okano, T. ); Hammam, M.S.A.A. ); Burns, C.; Adams, G. )

    1993-10-01

    Covered conductors have been used, especially in wooded areas on low as well as high voltage overhead distribution lines for preventing brush contact and short circuit faults between conductors. Burndown on covered conductors has become a significant problem. The burndown mechanism is complicated since it is determined by combinations of the various types of insulators, ties, and conductors. In order to investigate the burndown mechanism for this paper a finite element analysis has been carried out to identify the electric field around the insulator. In this paper a newly developed electric field simulation system is reported; the finite element analysis method considering isoparametric triangular and line elements has been developed and a new color display method for electric potential and electric field distributions with lines of electric force has also been developed in order to easily observe the results.

  9. Dirac point and transconductance of top-gated graphene field-effect transistors operating at elevated temperature

    SciTech Connect

    Hopf, T.; Vassilevski, K. V. Escobedo-Cousin, E.; King, P. J.; Wright, N. G.; O'Neill, A. G.; Horsfall, A. B.; Goss, J. P.; Wells, G. H.; Hunt, M. R. C.

    2014-10-21

    Top-gated graphene field-effect transistors (GFETs) have been fabricated using bilayer epitaxial graphene grown on the Si-face of 4H-SiC substrates by thermal decomposition of silicon carbide in high vacuum. Graphene films were characterized by Raman spectroscopy, Atomic Force Microscopy, Scanning Tunnelling Microscopy, and Hall measurements to estimate graphene thickness, morphology, and charge transport properties. A 27 nm thick Al₂O₃ gate dielectric was grown by atomic layer deposition with an e-beam evaporated Al seed layer. Electrical characterization of the GFETs has been performed at operating temperatures up to 100 °C limited by deterioration of the gate dielectric performance at higher temperatures. Devices displayed stable operation with the gate oxide dielectric strength exceeding 4.5 MV/cm at 100 °C. Significant shifting of the charge neutrality point and an increase of the peak transconductance were observed in the GFETs as the operating temperature was elevated from room temperature to 100 °C.

  10. Low operating voltage n-channel organic field effect transistors using lithium fluoride/PMMA bilayer gate dielectric

    SciTech Connect

    Kumar, S.; Dhar, A.

    2015-10-15

    Highlights: • Alternative to chemically crosslinking of PMMA to achieve low leakage in provided. • Effect of LiF in reducing gate leakage through the OFET device is studied. • Effect of gate leakage on transistor performance has been investigated. • Low voltage operable and low temperature processed n-channel OFETs were fabricated. - Abstract: We report low temperature processed, low voltage operable n-channel organic field effect transistors (OFETs) using N,N′-Dioctyl-3,4,9,10-perylenedicarboximide (PTCDI-C{sub 8}) organic semiconductor and poly(methylmethacrylate) (PMMA)/lithium fluoride (LiF) bilayer gate dielectric. We have studied the role of LiF buffer dielectric in effectively reducing the gate leakage through the device and thus obtaining superior performance in contrast to the single layer PMMA dielectric devices. The bilayer OFET devices had a low threshold voltage (V{sub t}) of the order of 5.3 V. The typical values of saturation electron mobility (μ{sub s}), on/off ratio and inverse sub-threshold slope (S) for the range of devices made were estimated to be 2.8 × 10{sup −3} cm{sup 2}/V s, 385, and 3.8 V/decade respectively. Our work thus provides a potential substitution for much complicated process of chemically crosslinking PMMA to achieve low leakage, high capacitance, and thus low operating voltage OFETs.

  11. High carrier mobility of CoPc wires based field-effect transistors using bi-layer gate dielectric

    SciTech Connect

    Gedda, Murali; Obaidulla, Sk. Md.; Subbarao, Nimmakayala V. V.; Goswami, Dipak K.

    2013-11-15

    Polyvinyl alcohol (PVA) and anodized Al{sub 2}O{sub 3} layers were used as bi-layer gate for the fabrication of cobalt phthalocyanine (CoPc) wire base field-effect transistors (OFETs). CoPc wires were grown on SiO{sub 2} surfaces by organic vapor phase deposition method. These devices exhibit a field-effect carrier mobility (μ{sub EF}) value of 1.11 cm{sup 2}/Vs. The high carrier mobility for CoPc molecules is attributed to the better capacitive coupling between the channel of CoPc wires and the gate through organic-inorganic dielectric layer. Our measurements also demonstrated the way to determine the thicknesses of the dielectric layers for a better process condition of OFETs.

  12. The Helium Field Effect Transistor (II): Gated Transport of Surface-State Electrons Through Micro-constrictions

    NASA Astrophysics Data System (ADS)

    Shaban, F.; Ashari, M.; Lorenz, T.; Rau, R.; Scheer, E.; Kono, K.; Rees, D. G.; Leiderer, P.

    2016-06-01

    We present transport measurements of surface-state electrons on liquid helium films in confined geometry. The measurements are taken using split-gate devices similar to a field effect transistor. The number of electrons passing between the source and drain areas of the device can be precisely controlled by changing the length of the voltage pulse applied to the gate electrode. We find evidence that the effective driving potential depends on electron-electron interactions, as well as the electric field applied to the substrate. Our measurements indicate that the mobility of electrons on helium films can be high and that microfabricated transistor devices allow electron manipulation on length scales close to the interelectron separation. Our experiment is an important step toward investigations of surface-state electron properties at much higher densities, for which the quantum melting of the system to a degenerate Fermi gas should be observed.

  13. Efficient parametric excitation of silicon-on-insulator microcantilever beams by fringing electrostatic fields

    NASA Astrophysics Data System (ADS)

    Linzon, Yoav; Ilic, Bojan; Lulinsky, Stella; Krylov, Slava

    2013-04-01

    Large amplitude flexural vibrations have been excited in single layer silicon-on-insulator micromechanical cantilever beams in ambient air environment. Our driving approach relies on a single co-planar electrode located symmetrically around the actuated grounded cantilever. Electrostatic forces are created via tailored asymmetries in the fringing fields of deformed mechanical states during their electric actuation, with strong restoring forces acting in a direction opposite to the deflection. This results in an effective increase in the structure stiffness in its elastic regime. The devices had been fabricated using deep reactive ion etching based process and their responses were characterized in a laser Doppler vibrometer under ambient conditions. Harmonic voltages applied to the electrode result in the periodic modulation of the effective stiffness and lead to strong parametric excitation of the structure. As opposed to close gap actuators, where high-amplitude drives are severely limited by pull-in instabilities, squeezed gas damping, and stiction, our resonators exhibit very large vibration amplitudes (up to 8 in terms of the amplitude to thickness ratio in the strong parametric regime), with no apparent damage, via the application of highly tunable distributed forces. A reduced order model, based on the Galerkin decomposition, captures the main dynamical features of the system, and is consistent with the observed beam characteristics.

  14. 2006/07 Field Testing of Cellulose Fiber Insulation Enhanced with Phase Change Material

    SciTech Connect

    Kosny, Jan; Yarbrough, David W; Miller, William A; Petrie, Thomas; Childs, Phillip W; Syed, Azam M

    2008-12-01

    Most recent improvements in building envelope technologies suggest that in the near future, residences will be routinely constructed to operate with very low heating and cooling loads. In that light, the application of novel building materials containing active thermal components (e.g., phase change materials [PCMs,] sub-venting, radiant barriers, and integrated hydronic systems) is like a final step in achieving relatively significant heating and cooling energy savings from technological improvements in the building envelope. It is expected that optimized building envelope designs using PCMs for energy storage can effectively bring notable savings in energy consumption and reductions in peak hour power loads. During 2006/07, a research team at Oak Ridge National Laboratory (ORNL) performed a series of laboratory and field tests of several wall and roof assemblies using PCM-enhanced cellulose insulation. This report summarizes the test results from the perspective of energy performance. The ORNL team is working on both inorganic and organic PCMs; this report discusses only paraffinic PCMs. A limited economical analysis also is presented. PCMs have been tested as a thermal mass component in buildings for at least 40 years. Most of the research studies found that PCMs enhanced building energy performance. In the case of the application of organic PCMs, problems such as high initial cost and PCM leaking (surface sweating) have hampered widespread adoption. Paraffinic hydrocarbon PCMs generally performed well, with the exception that they increased the flammability of the building envelope.

  15. Field study of moisture damage in walls insulated without a vapor barrier. Final report for the Oregon Department of Energy

    SciTech Connect

    Tsongas, G.A.

    1980-05-01

    Considerable uncertainty has existed over whether or not wall insulation installed without a vapor barrier causes an increased risk of moisture damage (wood decay) within walls. This report describes the results of one of the first major studies in the country aimed at finding out if such a moisture problem really exists. The exterior walls of a total of 96 homes in Portland, Oregon were opened, of which 70 had retrofitted insulation and 26 were uninsulated and were a control group. The types of insulation included urea-formaldehyde foam (44), mineral wool (16), and cellulose (10). In each opened wall cavity the moisture content of wood was measured and insulation and wood samples were taken for laboratory analysis of moisture content and for the determination of the presence of absence of decay fungi. Foam shrinkage was also measured. To evaluate the possible influence of the relative air tightness of the homes, fan depressurization tests were run using a door blower unit. The field and laboratory test results indicating the lack of a moisture damage problem in existing homes with wood siding in climates similar to that of western Oregon are described along with results of a statistical analysis of the data. Related problems of interest to homeowners and insulation installers are noted. The standard operating procedures used throughout the study are discussed, including the home selection process, quantitative and qualitative techniques used to identify wall locations with the highest moisture content, wall opening and data/sample collection methodology, laboratory analysis of samples, data processing and analysis, and applicability of the results. Recommendations for furutre tests are made. Finally, the potential and desirability for future retrofitting of wall insulation is explored.

  16. Tracing the interwell plasmon in a grid-gated double-quantum-well field-effect transistor

    NASA Astrophysics Data System (ADS)

    Popov, Vyacheslav V.; Teperik, Tatiana V.; Zayko, Yuriy N.; Horing, Norman J. M.; Fateev, Denis V.

    2005-06-01

    The terahertz (THz) absorption spectra of plasmon modes in a grid-gated double-quantum-well (DQW) field-effect transistor (FET) structute is analyzed theoretically and numerically using the scattering matrix approach and is shown to faithfully reproduce strong resonant features of recent experimental observations of THz photoconductivity in such a structure. No traces ofthe interwell plasmon is found in THz absorption spectra.

  17. Real-time implementation of frequency-modulated continuous-wave synthetic aperture radar imaging using field programmable gate array

    NASA Astrophysics Data System (ADS)

    Quan, Yinghui; Li, Yachao; Hu, Guibin; Xing, Mengdao

    2015-06-01

    A new miniature linear frequency-modulated continuous-wave radar which mounted on an unmanned aerial vehicle is presented. It allows the accomplishment of high resolution synthetic aperture radar imaging in real-time. Only a Kintex-7 field programmable gate array from Xilinx is utilized for whole signal processing of sophisticated radar imaging algorithms. The proposed hardware architecture achieves remarkable improvement in integration, power consumption, volume, and computing performance over its predecessor designs. The realized design is verified by flight campaigns.

  18. Single Event Test Methodologies and System Error Rate Analysis for Triple Modular Redundant Field Programmable Gate Arrays

    NASA Technical Reports Server (NTRS)

    Allen, Gregory; Edmonds, Larry D.; Swift, Gary; Carmichael, Carl; Tseng, Chen Wei; Heldt, Kevin; Anderson, Scott Arlo; Coe, Michael

    2010-01-01

    We present a test methodology for estimating system error rates of Field Programmable Gate Arrays (FPGAs) mitigated with Triple Modular Redundancy (TMR). The test methodology is founded in a mathematical model, which is also presented. Accelerator data from 90 nm Xilins Military/Aerospace grade FPGA are shown to fit the model. Fault injection (FI) results are discussed and related to the test data. Design implementation and the corresponding impact of multiple bit upset (MBU) are also discussed.

  19. Modeling small-signal response of GaN-based metal-insulator-semiconductor high electron mobility transistor gate stack in spill-over regime: Effect of barrier resistance and interface states

    NASA Astrophysics Data System (ADS)

    Capriotti, M.; Lagger, P.; Fleury, C.; Oposich, M.; Bethge, O.; Ostermaier, C.; Strasser, G.; Pogany, D.

    2015-01-01

    We provide theoretical and simulation analysis of the small signal response of SiO2/AlGaN/GaN metal insulator semiconductor (MIS) capacitors from depletion to spill over region, where the AlGaN/SiO2 interface is accumulated with free electrons. A lumped element model of the gate stack, including the response of traps at the III-N/dielectric interface, is proposed and represented in terms of equivalent parallel capacitance, Cp, and conductance, Gp. Cp -voltage and Gp -voltage dependences are modelled taking into account bias dependent AlGaN barrier dynamic resistance Rbr and the effective channel resistance. In particular, in the spill-over region, the drop of Cp with the frequency increase can be explained even without taking into account the response of interface traps, solely by considering the intrinsic response of the gate stack (i.e., no trap effects) and the decrease of Rbr with the applied forward bias. Furthermore, we show the limitations of the conductance method for the evaluation of the density of interface traps, Dit, from the Gp/ω vs. angular frequency ω curves. A peak in Gp/ω vs. ω occurs even without traps, merely due to the intrinsic frequency response of gate stack. Moreover, the amplitude of the Gp/ω vs. ω peak saturates at high Dit, which can lead to underestimation of Dit. Understanding the complex interplay between the intrinsic gate stack response and the effect of interface traps is relevant for the development of normally on and normally off MIS high electron mobility transistors with stable threshold voltage.

  20. Modeling small-signal response of GaN-based metal-insulator-semiconductor high electron mobility transistor gate stack in spill-over regime: Effect of barrier resistance and interface states

    SciTech Connect

    Capriotti, M. E-mail: dionyz.pogany@tuwien.ac.at; Fleury, C.; Oposich, M.; Bethge, O.; Strasser, G.; Pogany, D. E-mail: dionyz.pogany@tuwien.ac.at; Lagger, P.; Ostermaier, C.

    2015-01-14

    We provide theoretical and simulation analysis of the small signal response of SiO{sub 2}/AlGaN/GaN metal insulator semiconductor (MIS) capacitors from depletion to spill over region, where the AlGaN/SiO{sub 2} interface is accumulated with free electrons. A lumped element model of the gate stack, including the response of traps at the III-N/dielectric interface, is proposed and represented in terms of equivalent parallel capacitance, C{sub p}, and conductance, G{sub p}. C{sub p} -voltage and G{sub p} -voltage dependences are modelled taking into account bias dependent AlGaN barrier dynamic resistance R{sub br} and the effective channel resistance. In particular, in the spill-over region, the drop of C{sub p} with the frequency increase can be explained even without taking into account the response of interface traps, solely by considering the intrinsic response of the gate stack (i.e., no trap effects) and the decrease of R{sub br} with the applied forward bias. Furthermore, we show the limitations of the conductance method for the evaluation of the density of interface traps, D{sub it}, from the G{sub p}/ω vs. angular frequency ω curves. A peak in G{sub p}/ω vs. ω occurs even without traps, merely due to the intrinsic frequency response of gate stack. Moreover, the amplitude of the G{sub p}/ω vs. ω peak saturates at high D{sub it}, which can lead to underestimation of D{sub it}. Understanding the complex interplay between the intrinsic gate stack response and the effect of interface traps is relevant for the development of normally on and normally off MIS high electron mobility transistors with stable threshold voltage.

  1. Analytical Model for Direct Tunneling Gate Current in Long-Channel Undoped Cylindrical Surrounding Gate Metal-Oxide-Semiconductor Field Effect Transistors

    NASA Astrophysics Data System (ADS)

    Han, Ru; Li, Cong

    2013-02-01

    In this study, an analytical direct tunneling gate current model for long-channel undoped cylindrical surrounding gate (CSG) MOSFETs is developed. On the basis of an analytical model, the direct tunneling gate current in CSG MOSFETs is investigated. It is found that direct tunneling gate current is a strong function of gate oxide thickness, but less affected by the change in channel radius. It is also revealed that considering the influence of the source and drain, as the length of the underlap region decreases to zero, the direct tunneling gate current drastically increases. The accuracy of the analytical model is verified by the good agreement of its results with those obtained by the three-dimensional numerical device simulator ISE.

  2. Monte Carlo Simulation of a 6 MV X-Ray Beam for Open and Wedge Radiation Fields, Using GATE Code

    PubMed Central

    Bahreyni-Toosi, Mohammad-Taghi; Nasseri, Shahrokh; Momennezhad, Mahdi; Hasanabadi, Fatemeh; Gholamhosseinian, Hamid

    2014-01-01

    The aim of this study is to provide a control software system, based on Monte Carlo simulation, and calculations of dosimetric parameters of standard and wedge radiation fields, using a Monte Carlo method. GATE version 6.1 (OpenGATE Collaboration), was used to simulate a compact 6 MV linear accelerator system. In order to accelerate the calculations, the phase-space technique and cluster computing (Condor version 7.2.4, Condor Team, University of Wisconsin–Madison) were used. Dosimetric parameters used in treatment planning systems for the standard and wedge radiation fields (10 cm × 10 cm to 30 cm × 30 cm and a 60° wedge), including the percentage depth dose and dose profiles, were measured by both computational and experimental methods. Gamma index was applied to compare calculated and measured results with 3%/3 mm criteria. Gamma index was applied to compare calculated and measured results. Almost all calculated data points have satisfied gamma index criteria of 3% to 3 mm. Based on the good agreement between calculated and measured results obtained for various radiation fields in this study, GATE may be used as a useful tool for quality control or pretreatment verification procedures in radiotherapy. PMID:25426430

  3. Performance enhancement of multiple-gate ZnO metal-oxide-semiconductor field-effect transistors fabricated using self-aligned and laser interference photolithography techniques

    PubMed Central

    2014-01-01

    The simple self-aligned photolithography technique and laser interference photolithography technique were proposed and utilized to fabricate multiple-gate ZnO metal-oxide-semiconductor field-effect transistors (MOSFETs). Since the multiple-gate structure could improve the electrical field distribution along the ZnO channel, the performance of the ZnO MOSFETs could be enhanced. The performance of the multiple-gate ZnO MOSFETs was better than that of the conventional single-gate ZnO MOSFETs. The higher the drain-source saturation current (12.41 mA/mm), the higher the transconductance (5.35 mS/mm) and the lower the anomalous off-current (5.7 μA/mm) for the multiple-gate ZnO MOSFETs were obtained. PMID:24948884

  4. The Use of Field Programmable Gate Arrays (FPGA) in Small Satellite Communication Systems

    NASA Technical Reports Server (NTRS)

    Varnavas, Kosta; Sims, William Herbert; Casas, Joseph

    2015-01-01

    This paper will describe the use of digital Field Programmable Gate Arrays (FPGA) to contribute to advancing the state-of-the-art in software defined radio (SDR) transponder design for the emerging SmallSat and CubeSat industry and to provide advances for NASA as described in the TAO5 Communication and Navigation Roadmap (Ref 4). The use of software defined radios (SDR) has been around for a long time. A typical implementation of the SDR is to use a processor and write software to implement all the functions of filtering, carrier recovery, error correction, framing etc. Even with modern high speed and low power digital signal processors, high speed memories, and efficient coding, the compute intensive nature of digital filters, error correcting and other algorithms is too much for modern processors to get efficient use of the available bandwidth to the ground. By using FPGAs, these compute intensive tasks can be done in parallel, pipelined fashion and more efficiently use every clock cycle to significantly increase throughput while maintaining low power. These methods will implement digital radios with significant data rates in the X and Ka bands. Using these state-of-the-art technologies, unprecedented uplink and downlink capabilities can be achieved in a 1/2 U sized telemetry system. Additionally, modern FPGAs have embedded processing systems, such as ARM cores, integrated inside the FPGA allowing mundane tasks such as parameter commanding to occur easily and flexibly. Potential partners include other NASA centers, industry and the DOD. These assets are associated with small satellite demonstration flights, LEO and deep space applications. MSFC currently has an SDR transponder test-bed using Hardware-in-the-Loop techniques to evaluate and improve SDR technologies.

  5. A time digitizer for space instrumentation using a field programmable gate array

    NASA Astrophysics Data System (ADS)

    Rogacki, S.; Zurbuchen, T. H.

    2013-08-01

    Space instruments such as time-of-flight (TOF) mass spectrometers and altimeters rely on time-to-digital converters (TDCs) to measure accurately times in the picosecond to microsecond range. Time-to-digital conversion is often implemented with analog circuitry or more recently with custom ASIC (Application Specific Integrated Circuit) devices. The analog approach may be costly in terms of circuit board area and parts count, while ASIC development is risky and costly when system requirements may change. Here, we present a highly flexible, accurate, and low-cost field-programmable gate array (FPGA) implementation of such TDC functionality. Compared with other technologies, this method reduces the parts count in TOF-supporting circuits and provides design flexibility in TOF instrumentation, especially for use in space or for applications with a number of sensors too small to warrant the development of a dedicated ASIC. Our technique can accommodate one or more STOP pulse measurements for each START pulse as signal reference, effectively providing measurements of multiple times-of-flight with the same start trigger. Alternatively, all pulse event edges can receive an absolute time stamp, enabling a broad set of new sensor applications. This novel design is based on the construction of a delay-line internal to the FPGA. Propagation variations due to temperature and supply voltage, which typically limit FPGA-based timing designs, are automatically compensated, allowing active signal processing 100% of the time. A methodology for the characterization of internal delay-line timing and nonlinearity has also been developed and is not specific to a particular FPGA architecture. We describe the design of this FPGA-based TDC and also describe detailed tests with a Xilinx XC2V1000. For single non-repetitive events, this design achieves 60 ps accuracy (standard deviation of error); a simplified implementation is suitable for non-reprogrammable FPGAs.

  6. Development and modeling of a stereo vision focusing system for a field programmable gate array robot

    NASA Astrophysics Data System (ADS)

    Tickle, Andrew J.; Buckle, James; Grindley, Josef E.; Smith, Jeremy S.

    2010-10-01

    Stereo vision is a situation where an imaging system has two or more cameras in order to make it more robust by mimicking the human vision system. By using two inputs, knowledge of their own relative geometry can be exploited to derive depth information from the two views they receive. 3D co-ordinates of an object in an observed scene can be computed from the intersection of the two sets of rays. Presented here is the development of a stereo vision system to focus on an object at the centre of a baseline between two cameras at varying distances. This has been developed primarily for use on a Field Programmable Gate Array (FPGA) but an adaptation of this developed methodology is also presented for use with a PUMA 560 Robotic Manipulator with a single camera attachment. The two main vision systems considered here are a fixed baseline with an object moving at varying distances from this baseline, and a system with a fixed distance and a varying baseline. These two differing situations provide enough data so that the co-efficient variables that determine the system operation can be calibrated automatically with only the baseline value needing to be entered, the system performs all the required calculations for the user for use with a baseline of any distance. The limits of system with regards to the focusing accuracy obtained are also presented along with how the PUMA 560 controls its joints for the stereo vision and how it moves from one position to another to attend stereo vision compared to the two camera system for the FPGA. The benefits of such a system for range finding in mobile robotics are discussed and how this approach is more advantageous when compared against laser range finders or echolocation using ultrasonics.

  7. Optical multi-token-ring networking using smart pixels with field programmable gate arrays (FPGAs)

    NASA Astrophysics Data System (ADS)

    Zhang, Liping; Hong, Sunkwang; Min, Changki; Alpaslan, Zahir Y.; Sawchuk, Alexander A.

    2001-12-01

    This research explores architectures and design principles for monolithic optoelectronic integrated circuits (OEICs) through the implementation of an optical multi-token-ring network testbed system. Monolithic smart pixel CMOS OEICs are of paramount importance to high performance networks, communication switches, computer interfaces, and parallel signal processing for demanding future multimedia applications. The general testbed system is called Reconfigurable Translucent Smart Pixel Array (R-Transpar) and includes a field programmable gate array (FPGA), a transimpedance receiver array, and an optoelectronic very large-scale integrated (OE-VLSI) smart pixel array. The FPGA is an Altera FLEX10K100E chip that performs logic functions and receives inputs from the transimpedance receiver array. A monolithic (OE-VLSI) smart pixel device containing an array of 4 X 4 vertical-cavity surface-emitting lasers (VCSELs) spatially interlaced with an array of 4 X 4 metal- semiconductor-metal (MSM) detectors connects to these devices and performs optical input-output functions. These components are mounted on a printed circuit board for testing and evaluation of integrated monolithic OEIC designs and various optical interconnection techniques. The system moves information between nodes by transferring 3-D optical packets in free space or through fiber image guides. The R-Transpar system is reconfigurable to test different network protocols and signal processing functions. In its operation as a 3-D multi-token-ring network, we use a specific version of the system called Transpar-Token-Ring (Transpar-TR) that uses novel time-division multiplexed (TDM) network node addressing to enhance channel utilization and throughput. Host computers interface with the system via a high-speed digital I/O board that sends commands for networking and application algorithm operations. We describe the system operation and experimental results in detail.

  8. Continuous, high-speed, volumetric photoacoustic microscopy via a field programmable gate array

    NASA Astrophysics Data System (ADS)

    Mattison, Scott P.; Shelton, Ryan L.; Maxson, Ryan T.; Applegate, Brian E.

    2013-03-01

    The ability to collect data in real time is important in all biological imaging modalities that aim to image dynamic processes. Photoacoustic Microscopy (PAM) is a rapidly growing biomedical imaging technique that is often used to image microvasculature and melanoma, and is capable of fully rendering three-dimensional images. However, due to the bi-polar nature of the PAM signal, post processing through demodulation is required to accurately display morphological data. Typically, demodulation requires post processing of the data, limiting its use in real-time applications. This results in many PAM systems displaying data through maximum amplitude projection (MAP) images, completely ignoring the axial dimension of their scans and throwing away useful data. We overcome this processing limit by utilizing a configurable integrated circuit known as a Field Programmable Gate Array (FPGA). The FPGA allows us to perform quadrature demodulation of the photoacoustic signal as it is being collected. The result is a PAM system capable of producing continuous, morphologically accurate B-scans and volumes at a rate limited only by the repetition rate of the laser. This allows us to generate accurately rendered volumes at the same speed as MAP images. With a 100 KHz actively q-switched laser we are able to generate 200 by 200 pixel b-scans at a rate of 500 Hz. The imaging potential of the system has been demonstrated in volumes of human hair phantoms and chick embryo vasculature. This system is capable of 50 x 50 x 50 volume stacks processed and displayed at better than video rate.

  9. Enzyme-modified electrolyte-gated organic field-effect transistors

    NASA Astrophysics Data System (ADS)

    Buth, Felix; Donner, Andreas; Stutzmann, Martin; Garrido, Jose A.

    2012-10-01

    Organic solution-gated field-effect transistors (SGFETs) can be operated at low voltages in aqueous environments, paving the way to the use of organic semiconductors in bio-sensing applications. However, it has been shown that these devices exhibit only a rather weak sensitivity to standard electrolyte parameters such as pH and ionic strength. In order to increase the sensitivity and to add specificity towards a given analyte, the covalent attachment of functional groups and enzymes to the device surface would be desirable. In this contribution we demonstrate that enzyme modified organic SGFETs can be used for the in-situ detection of penicillin in the low μM regime. In a first step, silane molecules with amine terminal groups are grafted to α-sexithiophene-based thin film transistors. Surface characterization techniques like X-ray photoemission confirm the modification of the surface with these functional groups, which are stable in standard aqueous electrolytes. We show that the presence of surface-bound amphoteric groups (e.g. amino or carboxylic moieties) increases the pH-sensitivity of the organic SGFETs. In addition, these groups serve as anchoring sites for the attachment of the enzyme penicillinase. The resulting enzyme-FETs are used for the detection of penicillin, enabling the study of the influence of the buffer strength and the pH of the electrolyte on the enzyme kinetics. The functionalization of the organic FETs shown here can be extended to a large variety of enzymes, allowing the specific detection of different chemical and biochemical analytes.

  10. A time digitizer for space instrumentation using a field programmable gate array.

    PubMed

    Rogacki, S; Zurbuchen, T H

    2013-08-01

    Space instruments such as time-of-flight (TOF) mass spectrometers and altimeters rely on time-to-digital converters (TDCs) to measure accurately times in the picosecond to microsecond range. Time-to-digital conversion is often implemented with analog circuitry or more recently with custom ASIC (Application Specific Integrated Circuit) devices. The analog approach may be costly in terms of circuit board area and parts count, while ASIC development is risky and costly when system requirements may change. Here, we present a highly flexible, accurate, and low-cost field-programmable gate array (FPGA) implementation of such TDC functionality. Compared with other technologies, this method reduces the parts count in TOF-supporting circuits and provides design flexibility in TOF instrumentation, especially for use in space or for applications with a number of sensors too small to warrant the development of a dedicated ASIC. Our technique can accommodate one or more STOP pulse measurements for each START pulse as signal reference, effectively providing measurements of multiple times-of-flight with the same start trigger. Alternatively, all pulse event edges can receive an absolute time stamp, enabling a broad set of new sensor applications. This novel design is based on the construction of a delay-line internal to the FPGA. Propagation variations due to temperature and supply voltage, which typically limit FPGA-based timing designs, are automatically compensated, allowing active signal processing 100% of the time. A methodology for the characterization of internal delay-line timing and nonlinearity has also been developed and is not specific to a particular FPGA architecture. We describe the design of this FPGA-based TDC and also describe detailed tests with a Xilinx XC2V1000. For single non-repetitive events, this design achieves 60 ps accuracy (standard deviation of error); a simplified implementation is suitable for non-reprogrammable FPGAs. PMID:24007053

  11. Use of Field Programmable Gate Array Technology in Future Space Avionics

    NASA Technical Reports Server (NTRS)

    Ferguson, Roscoe C.; Tate, Robert

    2005-01-01

    Fulfilling NASA's new vision for space exploration requires the development of sustainable, flexible and fault tolerant spacecraft control systems. The traditional development paradigm consists of the purchase or fabrication of hardware boards with fixed processor and/or Digital Signal Processing (DSP) components interconnected via a standardized bus system. This is followed by the purchase and/or development of software. This paradigm has several disadvantages for the development of systems to support NASA's new vision. Building a system to be fault tolerant increases the complexity and decreases the performance of included software. Standard bus design and conventional implementation produces natural bottlenecks. Configuring hardware components in systems containing common processors and DSPs is difficult initially and expensive or impossible to change later. The existence of Hardware Description Languages (HDLs), the recent increase in performance, density and radiation tolerance of Field Programmable Gate Arrays (FPGAs), and Intellectual Property (IP) Cores provides the technology for reprogrammable Systems on a Chip (SOC). This technology supports a paradigm better suited for NASA's vision. Hardware and software production are melded for more effective development; they can both evolve together over time. Designers incorporating this technology into future avionics can benefit from its flexibility. Systems can be designed with improved fault isolation and tolerance using hardware instead of software. Also, these designs can be protected from obsolescence problems where maintenance is compromised via component and vendor availability.To investigate the flexibility of this technology, the core of the Central Processing Unit and Input/Output Processor of the Space Shuttle AP101S Computer were prototyped in Verilog HDL and synthesized into an Altera Stratix FPGA.

  12. A novel low specific on-resistance double-gate LDMOS with multiple buried p-layers in the drift region based on the Silicon-On-Insulator substrate

    NASA Astrophysics Data System (ADS)

    Chen, Yinhui; Hu, Shengdong; Cheng, Kun; Jiang, YuYu; Luo, Jun; Wang, Jian'an; Tang, Fang; Zhou, Xichuan; Zhou, Jianlin; Gan, Ping

    2016-01-01

    A novel double-gate SOI LDMOS with multiple buried p-layers in the drift region (MBP SOI LDMOS) is proposed in this paper. MBP SOI LDMOS has two gates, the planar gate and the trench gate. The big feature of MBP LDMOS is the multiple buried p-layers with intervals in the drift region which is an arithmetic progression and decreases successively. Firstly, double gates of the structure form dual current conduction channels, leading to a low specific on-resistance (Ron,sp). Secondly, the multiple buried p-layers form a more significant triple RESURF effect, which not only increases the drift doping concentration but also modulates the electric field of the drift region, resulting in a low Ron,sp and a high breakdown voltage (BV). MBP SOI LDMOS is thus owning a reduced Ron,sp and an improved BV. The effects of structure parameters on the device performances are investigated. Compared with the conventional SOI LDMOS, the Ron,sp of MBP SOI LDMOS is reduced by 52.5% with BV increasing by 36.4% at the same 16-μm-drift region.

  13. High quality PECVD SiO2 process for recessed MOS-gate of AlGaN/GaN-on-Si metal–oxide–semiconductor heterostructure field-effect transistors

    NASA Astrophysics Data System (ADS)

    Lee, Jae-Gil; Kim, Hyun-Seop; Seo, Kwang-Seok; Cho, Chun-Hyung; Cha, Ho-Young

    2016-08-01

    A high quality SiO2 deposition process using a plasma enhanced chemical vapor deposition system has been developed for the gate insulator process of normally-off recessed-gate AlGaN/GaN metal-oxide-semiconductor-heterostructure field-effect transistors (MOS-HFETs). SiO2 films were deposited by using SiH4 and N2O mixtures as reactant gases. The breakdown field increased with increasing the N2O flow rate. The optimum SiH4/N2O ratio was 0.05, which resulted in a maximum breakdown field of 11 MV/cm for the SiO2 film deposited on recessed GaN surface. The deposition conditions were optimized as follows; a gas flow rate of SiH4/N2O (=27/540 sccm), a source RF power of 100 W, a pressure of 2 Torr, and a deposition temperature of 350 °C. A fabricated normally-off MOS-HFET exhibited a threshold voltage of 3.2 V, a specific on-resistance of 4.46 mΩ cm2, and a breakdown voltage of 810 V.

  14. Role of the resistivity of insulating field emitters on the energy of field-ionised and field-evaporated atoms.

    PubMed

    Arnoldi, L; Silaeva, E P; Vurpillot, F; Deconihout, B; Cadel, E; Blum, I; Vella, A

    2015-12-01

    In order to improve the accuracy of laser atom probe analyses, it is important to understand all the physical processes induced by the combination of the high electrical field and the femtosecond laser beam during field evaporation. New information can be accessed from the energy of evaporated surface atoms or field-ionised atoms of an imaging gas. In order to study the ions energy, we combine La-APT and FIM analyses in a new experimental setup equipped with electrostatic lenses. We report measurements for semiconductors and oxides and we study the influence of the illumination conditions (laser power and wavelength), the evaporation rate, the sample geometry and the tip preparation processes. The results are discussed taking into account the resistive properties of non-metallic samples and the photo-stimulated conductivity. This work clarifies the role of the laser and DC field in the energy deficit of field evaporated ions. PMID:25484362

  15. Comparison of Focused and Near-Field Imaging of Spray on Foam Insulation (SOFI) at Millimeter Wave Frequencies

    NASA Technical Reports Server (NTRS)

    Kharkovshy, S.; Zoughi, R.; Hepburn, F. L.

    2007-01-01

    Millimeter wave imaging techniques can provide high spatial-resolution images of various composites. Lens antennas may be incorporated into the imaging system to provide a small incident beam footprint. Another approach may involve the use of horn antennas, which if operating in their near-fields, images with reasonably high spatial-resolutions may also be obtained. This paper gives a comparison between such near-field and focused far-field imaging of the Space Shuttle Spray on Foam Insulation (SOFI) used in its external fuel tank at millimeter wave frequencies. Small horn antennas and lens antennas with relatively long depth of focus were used in this investigation.

  16. Room temperature on-wafer ballistic graphene field-effect-transistor with oblique double-gate

    NASA Astrophysics Data System (ADS)

    Dragoman, Mircea; Dinescu, Adrian; Dragoman, Daniela

    2016-06-01

    We have fabricated and measured ballistic graphene transistors with two oblique gates that can be independently biased. The gates, with lengths of about 30 nm and separated by a distance of about 40 nm, are tilted at 45° with respect to the source and drain electrodes, which are distanced at 190 nm. Electric measurements reveal specific properties of ballistic carrier transport, i.e., nonlinear drain voltage-drain current dependences with saturation regions and negative differential resistance at certain bias voltages. Tens of ballistic transistors with very large transconductances were fabricated on a chip cut from a 4 in. graphene wafer. Such double-gate transistor configurations can be used also as extremely efficient, state-of-the-art photodetectors.

  17. Comparison of Focused and Near-Field Imaging of Spray on Foam Insulation (SOFI) at Millimeter Wave Frequencies

    NASA Technical Reports Server (NTRS)

    Kharkovsky, S.; Zoughi, R.; Hepburn, F. L.

    2007-01-01

    The Space Shuttle Columbia's catastrophic accident was due to a piece of Spray on Foam Insulation (SOFI) that broke off from the external tank and damaged the leading edge of the orbiter's left wing. Millimeter wave focused and near-field imaging methods have been suessfully used for inspecting of the SOFI samples. Comparison between these methods for the purpose of detection and evaluation of flaws in the SOFI is provided using examples of images of SOFI samples.

  18. The n-type metal-oxide semiconductor field-effect transistor bias impact on the modelling of the gate-induced drain leakage current

    NASA Astrophysics Data System (ADS)

    Touhami, A.; Bouhdada, A.

    2002-12-01

    The band-to-band tunnelling (BBT) effect in an n-type metal-oxide semiconductor field-effect transistor (n-MOSFET) is attributed not only to the transverse electric field ET but also to the lateral electric field EL in the gate-to-drain overlap region. The main sources of these electric fields are the gate-source (Vgs) and drain-source (Vds) voltages. The modelling of the gate-induced drain leakage current, Igidl, associated with BBT remains always dependent on the drain-gate voltage, Vdg, whatever the applied values of Vgs and Vds, which cannot describe accurately the evolution of the Igidl current according to biases. Therefore, it is necessary to clarify the impact of Vgs and Vds separately. In this paper, we propose a new model of the Igidl current, which can describe the BBT effect in n-MOSFETs under various Vgs and Vds biases.

  19. Au-gated SrTiO{sub 3} field-effect transistors with large electron concentration and current modulation

    SciTech Connect

    Verma, Amit Jena, Debdeep; Raghavan, Santosh; Stemmer, Susanne

    2014-09-15

    We report the fabrication of low-leakage rectifying Pt and Au Schottky diodes and Au-gated metal-semiconductor field effect transistors (MESFETs) on n-type SrTiO{sub 3} thin films grown by hybrid molecular beam epitaxy. In agreement with previous studies, we find that compared to Pt, Au provides a higher Schottky barrier height with SrTiO{sub 3}. As a result of the large dielectric constant of SrTiO{sub 3} and the large Schottky barrier height of Au, the Au-gated MESFETs are able to modulate ∼1.6 × 10{sup 14 }cm{sup −2} electron density, the highest modulation yet achieved using metal gates in any material system. These MESFETs modulate current densities up to ∼68 mA/mm, ∼20× times larger than the best demonstrated SrTiO{sub 3} MESFETs. We also discuss the roles of the interfacial layer, and the field-dependent dielectric constant of SrTiO{sub 3} in increasing the pinch off voltage of the MESFET.

  20. Gas Sensors Characterization and Multilayer Perceptron (MLP) Hardware Implementation for Gas Identification Using a Field Programmable Gate Array (FPGA)

    PubMed Central

    Benrekia, Fayçal; Attari, Mokhtar; Bouhedda, Mounir

    2013-01-01

    This paper develops a primitive gas recognition system for discriminating between industrial gas species. The system under investigation consists of an array of eight micro-hotplate-based SnO2 thin film gas sensors with different selectivity patterns. The output signals are processed through a signal conditioning and analyzing system. These signals feed a decision-making classifier, which is obtained via a Field Programmable Gate Array (FPGA) with Very High-Speed Integrated Circuit Hardware Description Language. The classifier relies on a multilayer neural network based on a back propagation algorithm with one hidden layer of four neurons and eight neurons at the input and five neurons at the output. The neural network designed after implementation consists of twenty thousand gates. The achieved experimental results seem to show the effectiveness of the proposed classifier, which can discriminate between five industrial gases. PMID:23529119

  1. Gas sensors characterization and multilayer perceptron (MLP) hardware implementation for gas identification using a Field Programmable Gate Array (FPGA).

    PubMed

    Benrekia, Fayçal; Attari, Mokhtar; Bouhedda, Mounir

    2013-01-01

    This paper develops a primitive gas recognition system for discriminating between industrial gas species. The system under investigation consists of an array of eight micro-hotplate-based SnO2 thin film gas sensors with different selectivity patterns. The output signals are processed through a signal conditioning and analyzing system. These signals feed a decision-making classifier, which is obtained via a Field Programmable Gate Array (FPGA) with Very High-Speed Integrated Circuit Hardware Description Language. The classifier relies on a multilayer neural network based on a back propagation algorithm with one hidden layer of four neurons and eight neurons at the input and five neurons at the output. The neural network designed after implementation consists of twenty thousand gates. The achieved experimental results seem to show the effectiveness of the proposed classifier, which can discriminate between five industrial gases. PMID:23529119

  2. A compact quantum correction model for symmetric double gate metal-oxide-semiconductor field-effect transistor

    SciTech Connect

    Cho, Edward Namkyu; Shin, Yong Hyeon; Yun, Ilgu

    2014-11-07

    A compact quantum correction model for a symmetric double gate (DG) metal-oxide-semiconductor field-effect transistor (MOSFET) is investigated. The compact quantum correction model is proposed from the concepts of the threshold voltage shift (ΔV{sub TH}{sup QM}) and the gate capacitance (C{sub g}) degradation. First of all, ΔV{sub TH}{sup QM} induced by quantum mechanical (QM) effects is modeled. The C{sub g} degradation is then modeled by introducing the inversion layer centroid. With ΔV{sub TH}{sup QM} and the C{sub g} degradation, the QM effects are implemented in previously reported classical model and a comparison between the proposed quantum correction model and numerical simulation results is presented. Based on the results, the proposed quantum correction model can be applicable to the compact model of DG MOSFET.

  3. Palladium nanoparticle decorated silicon nanowire field-effect transistor with side-gates for hydrogen gas detection

    SciTech Connect

    Ahn, Jae-Hyuk; Yun, Jeonghoon; Park, Inkyu; Choi, Yang-Kyu

    2014-01-06

    A silicon nanowire field-effect transistor (SiNW FET) with local side-gates and Pd surface decoration is demonstrated for hydrogen (H{sub 2}) detection. The SiNW FETs are fabricated by top-down method and functionalized with palladium nanoparticles (PdNPs) through electron beam evaporation for H{sub 2} detection. The drain current of the PdNP-decorated device reversibly responds to H{sub 2} at different concentrations. The local side-gates allow individual addressing of each sensor and enhance the sensitivity by adjusting the working region to the subthreshold regime. A control experiment using a non-functionalized device verifies that the hydrogen-sensitivity is originated from the PdNPs functionalized on the SiNW surface.

  4. Transparent field-effect transistors based on AlN-gate dielectric and IGZO-channel semiconductor

    NASA Astrophysics Data System (ADS)

    Besleaga, C.; Stan, G. E.; Pintilie, I.; Barquinha, P.; Fortunato, E.; Martins, R.

    2016-08-01

    The degradation of thin-film transistors (TFTs) caused by the self-heating effect constitutes a problem to be solved for the next generation of displays. Aluminum nitride (AlN) is a viable alternative for gate dielectric of TFTs due to its good thermal conductivity, matching coefficient of thermal expansion to indium-gallium-zinc-oxide, and excellent stability at high temperatures. Here, AlN thin films of different thicknesses were fabricated by a low temperature reactive radio-frequency magnetron sputtering process, using a low cost, metallic Al target. Their electrical properties have been thoroughly assessed. Furthermore, the 200 nm and 500 nm thick AlN layers have been integrated as gate-dielectric in transparent TFTs with indium-gallium-zinc-oxide as channel semiconductor. Our study emphasizes the potential of AlN thin films for transparent electronics, whilst the functionality of the fabricated field-effect transistors is explored and discussed.

  5. Transient changes in electric fields induced by interaction of ultraintense laser pulses with insulator and metal foils: Sustainable fields spanning several millimeters.

    PubMed

    Inoue, Shunsuke; Tokita, Shigeki; Hashida, Masaki; Sakabe, Shuji

    2015-04-01

    The temporal evolutions of electromagnetic fields generated by the interaction between ultraintense lasers (1.3×10(18) and 8.2×10(18)W/cm(2)) and solid targets at a distance of several millimeters from the laser-irradiated region have been investigated by electron deflectometry. For three types of foil targets (insulating foil, conductive foil, and insulating foil onto which a metal disk was deposited), transient changes in the fields were observed. We found that the direction, strength, and temporal evolution of the generated fields differ markedly for these three types of targets. The results provide an insight for studying the emission dynamics of laser-accelerated fast electrons. PMID:25974596

  6. Buckley Prize Talk: Bosons on the Boundaries: The magnetic field driven superconductor-insulator quantum phase transition

    NASA Astrophysics Data System (ADS)

    Hebard, Arthur

    2015-03-01

    Experiments probing the competition between superconductivity and disorder in two-dimensional (2D) thin-film systems have provided fascinating glimpses into the physics of superconductor-insulator (S-I) quantum phase transitions (QPTs). This talk will address the use of externally applied magnetic fields to tune through the S-I transition of amorphous composite indium oxide (α-InOx) thin films prepared at different stages of disorder. Air-stable α-InOx films are particularly advantageous for these studies: the disorder parameter as measured by the sheet resistance can be reproducibly controlled during deposition and the films are uniformly homogeneous out to macroscopic length scales. Temperature-dependent resistance and current-voltage measurements confirm the power-law decay of the order-parameter correlation function appropriate to a Kosterlitz-Thouless description of phase transitions in 2D systems. Accordingly, the superconducting phase transition temperature Tc is related to the unbinding of vortex-antivortex pairs either by temperature and/or disorder. The application of magnetic fields unveils fundamentally different physics in which, rather than a vortex unbinding transition, a field-tuned QPT emerges with the signature of a disorder-dependent critical field Bc that identifies the delocalization and Bose condensation of field-induced vortices. The concomitant pronounced divergence in resistance, which becomes increasing sharp as the temperature is lowered, marks the boundary between a superconductor harboring both Bose condensed Cooper pairs and localized vortices and an insulator harboring both Bose condensed vortices and localized Cooper pairs. The data for this putative QPT are well described by finite temperature scaling theory with critical exponent values accurately determined. At higher fields there is a second critical field where the transverse resistance appears to diverge, signaling the unbinding of pairs with the superconducting energy gap

  7. Silicon Carbide Junction Field Effect Transistor Digital Logic Gates Demonstrated at 600 deg. C

    NASA Technical Reports Server (NTRS)

    Neudeck, Philip G.

    1998-01-01

    The High Temperature Integrated Electronics and Sensors (HTIES) Program at the NASA Lewis Research Center is currently developing silicon carbide (SiC) for use in harsh conditions where silicon, the semiconductor used in nearly all of today's electronics, cannot function. The HTIES team recently fabricated and demonstrated the first semiconductor digital logic gates ever to function at 600 C.

  8. Highly Oriented Polymer Field-Effect Transistors with High Electrical Stability

    NASA Astrophysics Data System (ADS)

    Endo, Toshiyuki; Nagase, Takashi; Kobayashi, Takashi; Naito, Hiroyoshi

    2013-12-01

    Oriented polymer field-effect transistors (FETs) with a top-gate configuration have been fabricated using amorphous fluoropolymers as gate insulators. The oriented poly(9,9-dioctylfluorene-co-bithiophene) (F8T2) FETs exhibit a high mobility anisotropy of 13 and a high mobility of 0.043 cm2.V-1.s-1 for charge transport parallel to the alignment direction. The temperature dependence of the mobility reveals small disorder in the oriented F8T2 microstructure at the interface with the fluoropolymer gate insulator. The transfer characteristics show no hysteresis or threshold voltage shift after applying a gate bias stress.

  9. High-performance CdS:P nanoribbon field-effect transistors constructed with high-κ dielectric and top-gate geometry

    NASA Astrophysics Data System (ADS)

    Wu, Di; Jiang, Yang; Wang, Li; Li, Shanying; Wu, Bo; Lan, Xinzheng; Yu, Yongqiang; Wu, Chunyan; Wang, Zhuangbing; Jie, Jiansheng

    2010-03-01

    High-performance field-effect transistors (FETs) based on single phosphorus-doped n-type CdS nanoribbon with high-κ HfO2 dielectric and top-gate geometry were constructed. In contrast to the nano-FETs that were fabricated on SiO2/Si substrate with back-gate device configuration, the top-gate FETs exhibit a substantial improvement in performances, i.e., work voltage was reduced to a small value of within ±5 V, the subthreshold swing was reduced to 200 mV/dec and the Ion/Ioff ratio was increased by about six orders of magnitude. The top-gate CdS:P nano-FET shows high sensitivity upon light irradiation, revealing that the top-gate FETs are promising candidates for nanoelectronic and optoelectronic applications.

  10. Simulation of dual-gate SOI MOSFET with different dielectric layers

    NASA Astrophysics Data System (ADS)

    Yadav, Jyoti; Chaudhary, R.; Mukhiya, R.; Sharma, R.; Khanna, V. K.

    2016-04-01

    The paper presents the process design and simulation of silicon-on-insulator (SOI)-based dual-gate metal oxide field-effect transistor (DG-MOSFET) stacked with different dielectric layers on the top of gate oxide. A detailed 2D process simulation of SOI-MOSFETs and its electrical characterization has been done using SILVACO® TCAD tool. A variation in transconductance was observed with different dielectric layers, AlN-gate MOSFET having the highest tranconductance value as compared to other three dielectric layers (SiO2, Si3N4 and Al2O3).

  11. Metallic monoclinic phase in VO2 induced by electrochemical gating: In situ Raman study

    NASA Astrophysics Data System (ADS)

    Nath Gupta, Satyendra; Pal, Anand; Muthu, D. V. S.; Kumar, P. S. Anil; Sood, A. K.

    2016-07-01

    We report in situ Raman scattering studies of electrochemically top gated VO2 thin film to address metal-insulator transition (MIT) under gating. The room temperature monoclinic insulating phase goes to metallic state at a gate voltage of 2.6 V. However, the number of Raman modes do not change with electrolyte gating showing that the metallic phase is still monoclinic. The high-frequency Raman mode A g (7) near 616 cm‑1 ascribed to V-O vibration of bond length 2.06 Å in VO6 octahedra hardens with increasing gate voltage and the B g (3) mode near 654 cm‑1 softens. This shows that the distortion of the VO6 octahedra in the monoclinic phase decreases with gating. The time-dependent Raman data at fixed gate voltages of 1 V (for 50 minutes, showing enhancement of conductivity by a factor of 50) and 2 V (for 130 minutes, showing further increase in conductivity by a factor of 5) show similar changes in high-frequency Raman modes A g (7) and B g (3) as observed in gating. This slow change in conductance together with Raman frequency changes show that the governing mechanism for metalization is more likely due to the diffusion-controlled oxygen vacancy formation due to the applied electric field.

  12. Effect of electric field configuration on streamer and partial discharge phenomena in a hydrocarbon insulating liquid under AC stress

    NASA Astrophysics Data System (ADS)

    Liu, Z.; Liu, Q.; Wang, Z. D.

    2016-05-01

    This paper concerns pre-breakdown phenomena, including streamer characteristics from a fundamental perspective and partial discharge (PD) measurements from an industrial perspective, in a hydrocarbon insulating liquid. The aim was to investigate the possible changes of the liquid’s streamer and PD characteristics and their correlations when the uniformity of the AC electric field varies. In the experiments, a plane-to-plane electrode system incorporating a needle protrusion was used in addition to a needle-to-plane electrode system. When the applied electric field became more uniform, fewer radial branches occurred and streamer propagation towards the ground electrode was enhanced. The transition from streamer propagation dominated breakdown in divergent fields to streamer initiation dominated breakdown in uniform fields was evidenced. Relationships between streamer and PD characteristics were established, which were found to be electric field dependent. PD of the same apparent charge would indicate longer streamers if the electric field is more uniform.

  13. Semiconducting properties of bilayer graphene modulated by an electric field for next-generation atomic-film electronics

    NASA Astrophysics Data System (ADS)

    Tsukagoshi, K.; Li, S.-L.; Miyazaki, H.; Aparecido-Ferreira, A.; Nakaharai, S.

    2014-03-01

    A practical wide bandgap was induced in bilayer graphene using a perpendicular electric field. A self-assembled gate insulator was used to apply a large electric field. The wide bandgap allows the operation of fundamental logic gates composed of bilayer graphene transistors. The results reviewed here indicate the potential for graphene electronics to be realized as emerging transistors with an atomically thin semiconductor.

  14. Short-Channel Tunneling Field-Effect Transistor with Drain-Overlap and Dual-Metal Gate Structure for Low-Power and High-Speed Operations.

    PubMed

    Yoon, Young Jun; Eun, Hye Rim; Seo, Jae Hwa; Kang, Hee-Sung; Lee, Seong Min; Lee, Jeongmin; Cho, Seongjae; Tae, Heung-Sik; Lee, Jung-Hee; Kang, In Man

    2015-10-01

    We have investigated and proposed a highly scaled tunneling field-effect transistor (TFET) based on Ge/GaAs heterojunction with a drain overlap to suppress drain-induced barrier thinning (DIBT) and improve low-power (LP) performance. The highly scaled TFET with a drain overlap achieves lower leakage tunneling current because of the decrease in tunneling events between the source and drain, whereas a typical short-channel TFET suffers from a great deal of tunneling leakage current due to the DIBT at the off-state. However, the drain overlap inevitably increases the gate-to-drain capacitance (Cgd) because of the increase in the overlap capacitance (Cov) and inversion capacitance (Cinv). Thus, in this work, a dual-metal gate structure is additionally applied along with the drain overlap. The current performance and the total gate capacitance (Cgg) of the device with a dual-metal gate can be possibly controlled by adjusting the metal gate workfunction (φgate) and φoverlap-gate in the overlapping regions. As a result, the intrinsic delay time (τ) is greatly reduced by obtaining lower Cgg divided by the on-state current (Ion), i.e., Cgg/Ion. We have successfully demonstrated excellent LP and high-speed performance of a highly scaled TFET by adopting both drain overlap and dual-metal gate with DIBT minimization. PMID:26726346

  15. On the origin of the two-dimensional electron gas at AlGaN/GaN heterojunctions and its influence on recessed-gate metal-insulator-semiconductor high electron mobility transistors

    NASA Astrophysics Data System (ADS)

    Bakeroot, B.; You, S.; Wu, T.-L.; Hu, J.; Van Hove, M.; De Jaeger, B.; Geens, K.; Stoffels, S.; Decoutere, S.

    2014-10-01

    It is commonly accepted that interface states at the passivation surface of AlGaN/GaN heterostructures play an important role in the formation of the 2DEG density. Several interface state models are cited throughout literature, some with discrete levels, others with different kinds of distributions, or a combination of both. The purpose of this article is to compare the existing interface state models with both direct and indirect measurements of these interface states from literature (e.g., through the hysteresis of transfer characteristics of Metal-Insulator-Semiconductor High Electron Mobility Transistors (MISHEMTs) employing such an interface in the gate region) and Technology Computer Aided Design (TCAD) simulations of 2DEG densities as a function of the AlGaN thickness. The discrepancies between those measurements and TCAD simulations (also those commonly found in literature) are discussed. Then, an alternative model inspired by the Disorder Induced Gap State model for compound semiconductors is proposed. It is shown that defining a deep border trap inside the insulator can solve these discrepancies and that this alternative model can explain the origin of the two dimensional electron gas in combination with a high-quality interface that, by definition, has a low interface state density.

  16. On the origin of the two-dimensional electron gas at AlGaN/GaN heterojunctions and its influence on recessed-gate metal-insulator-semiconductor high electron mobility transistors

    SciTech Connect

    Bakeroot, B.; You, S.; Van Hove, M.; De Jaeger, B.; Geens, K.; Stoffels, S.; Decoutere, S.; Wu, T.-L.; Hu, J.

    2014-10-07

    It is commonly accepted that interface states at the passivation surface of AlGaN/GaN heterostructures play an important role in the formation of the 2DEG density. Several interface state models are cited throughout literature, some with discrete levels, others with different kinds of distributions, or a combination of both. The purpose of this article is to compare the existing interface state models with both direct and indirect measurements of these interface states from literature (e.g., through the hysteresis of transfer characteristics of Metal-Insulator-Semiconductor High Electron Mobility Transistors (MISHEMTs) employing such an interface in the gate region) and Technology Computer Aided Design (TCAD) simulations of 2DEG densities as a function of the AlGaN thickness. The discrepancies between those measurements and TCAD simulations (also those commonly found in literature) are discussed. Then, an alternative model inspired by the Disorder Induced Gap State model for compound semiconductors is proposed. It is shown that defining a deep border trap inside the insulator can solve these discrepancies and that this alternative model can explain the origin of the two dimensional electron gas in combination with a high-quality interface that, by definition, has a low interface state density.

  17. Standard CMOS Fabrication of a Sensitive Fully Depleted Electrolyte-Insulator-Semiconductor Field Effect Transistor for Biosensor Applications

    PubMed Central

    Shalev, Gil; Cohen, Ariel; Doron, Amihood; Machauf, Andrew; Horesh, Moran; Virobnik, Udi; Ullien, Daniela; Levy, Ilan

    2009-01-01

    Microfabricated semiconductor devices are becoming increasingly relevant for detection of biological and chemical components. The integration of active biological materials together with sensitive transducers offers the possibility of generating highly sensitive, specific, selective and reliable biosensors. This paper presents the fabrication of a sensitive, fully depleted (FD), electrolyte-insulator-semiconductor field-effect transistor (EISFET) made with a silicon-on-insulator (SOI) wafer of a thin 10-30 nm active SOI layer. Initial results are presented for device operation in solutions and for bio-sensing. Here we report the first step towards a high volume manufacturing of a CMOS-based biosensor that will enable various types of applications including medical and environmental sensing. PMID:22408530

  18. Selective nitrate detection by an enzymatic sensor based on an extended-gate type organic field-effect transistor.

    PubMed

    Minami, Tsuyoshi; Sasaki, Yui; Minamiki, Tsukuru; Wakida, Shin-Ichi; Kurita, Ryoji; Niwa, Osamu; Tokito, Shizuo

    2016-07-15

    First selective nitrate biosensor device based on an extended-gate type organic field-effect transistor (OFET) is reported. The fabricated sensor device consists of the extended-gate electrode functionalized by a nitrate reductase with a mediator (=a bipyridinium derivative) and an OFET-based transducer. The mechanism of the nitrate detection can be explained by an electron-relay on the extended-gate electrode, resulting in changes of the electric properties of the OFET. The detection limit of nitrate in water is estimated to be 45 ppb, which suggests that the sensitivity of our fabricated sensor is comparable to those of some conventional detection methods. As a practical application of the OFET sensor, the nitrate detection in diluted human saliva has been successfully demonstrated; the results agreed well with those by conventional colorimetric measurement. The advantages of OFETs are printability, mechanical flexibility, stretchability and disposability, meaning that the fabricated OFET could open up a new approach for low-cost electronic devices toward on-site detection of nitrate in aqueous media. PMID:26921557

  19. Performance of Gate-All-Around Tunneling Field-Effect Transistors Based on Si1-x Gex Layer

    NASA Astrophysics Data System (ADS)

    Lee, Jae Sung; Kang, In Man

    Electrical performances of gate-all-around (GAA) tunneling field-effect transistors (TFETs) based on a silicon germanium (Si1-xGex) layer have been investigated in terms of subthreshold swing (SS), on/off current ratio, on-state current (Ion). Cut-off frequency (fT) and maximum oscillation frequency (fmax) were demonstrated from small-signal parameters such as effective gate resistance (Rg), gate-drain capacitance (Cgd), and transconductance (gm). According to the technology computer-aided design (TCAD) simulation results, the current drivability, fT, and fmax of GAA TFETs based on Si1-xGex layer were higher than those of GAA TFETs based on silicon. The simulated devices had 60nm channel length and 10nm channel radius. A GAA TFET with x =0.4 had maximum Ion of 51.4µA/µm, maximum fT of 72GHz, and maximum fmax of 610GHz. Additionally, improvements of performance at the presented device with PNPN junctions were demonstrated in terms of Ion, SS, fT, and fmax. When the device was designed with x =0.4 and n+ layer width (Wn) =6nm, it shows Ion of 271µA/µm, fT of 245GHz, and fmax of 1.49THz at an operating bias (VGS=VDS=1.0V).

  20. Carbon nanotube feedback-gate field-effect transistor: suppressing current leakage and increasing on/off ratio.

    PubMed

    Qiu, Chenguang; Zhang, Zhiyong; Zhong, Donglai; Si, Jia; Yang, Yingjun; Peng, Lian-Mao

    2015-01-27

    Field-effect transistors (FETs) based on moderate or large diameter carbon nanotubes (CNTs) usually suffer from ambipolar behavior, large off-state current and small current on/off ratio, which are highly undesirable for digital electronics. To overcome these problems, a feedback-gate (FBG) FET structure is designed and tested. This FBG FET differs from normal top-gate FET by an extra feedback-gate, which is connected directly to the drain electrode of the FET. It is demonstrated that a FBG FET based on a semiconducting CNT with a diameter of 1.5 nm may exhibit low off-state current of about 1 × 10(-13) A, high current on/off ratio of larger than 1 × 10(8), negligible drain-induced off-state leakage current, and good subthreshold swing of 75 mV/DEC even at large source-drain bias and room temperature. The FBG structure is promising for CNT FETs to meet the standard for low-static-power logic electronics applications, and could also be utilized for building FETs using other small band gap semiconductors to suppress leakage current. PMID:25545108