Low Leakage Levels Research Articles

Comparative Study on Schottky Contact Behaviors between Ga- and N-Polar GaN with SiNx Interlayer

We conducted a comparative study on the characterization of Ga-polar and N-polar GaN metal–insulator–semiconductor (MIS) Schottky contact with a SiNx gate dielectric. The correlation between the surface morphology and the current–voltage (I–V) characteristics of the Ga- and N-polar GaN Schottky contact with and without SiNx was established. The insertion of SiNx helps in reducing the reverse leakage current for both structures, even though the leakage is still higher for N-polar GaN, consistent with the Schottky barrier height calculated using X-ray photoelectron spectroscopy. To optimize the electric property of the N-polar device, various substrate misorientation angles were adopted. Among the different misorientation angles of the sapphire substrate, the GaN MIS Schottky barrier diode grown on 1° sapphire shows the lowest reverse leakage current, the smoothest surface morphology, and the best crystalline quality compared to N-polar GaN grown on 0.2° and 2° sapphire substrates. Furthermore, the mechanism of the reverse leakage current of the MIS-type N-polar GaN Schottky contact was investigated by temperature-dependent I–V characterization. FP emissions are thought to be the dominant reverse conduction mechanism for the N-polar GaN MIS diode. This work provides a promising approach towards the optimization of N-polar electronic devices with low levels of leakage and a favorable ideality factor.

Effect of wear-resistant coatings on the comprehensive performance of finger seal

Finger seals provide favourable flexible dynamic performance and a low level of leakage that is less than that of brush seals and graphite seals. However, the hysteresis caused by the friction between different finger slices or between the finger slice and the back plate strongly affects the working stability. In addition, the wear properties between the finger feet and rotor runway can adversely affect the working stability. Based on the tribological mechanism, wear-resistant coatings can provide a satisfactory solution to these problems. For this purpose, the simulations of finger seal are first performed in ANSYS to verify that good contact surface friction performance can effectively improve the efficiency of finger seal. Then we evaluated the friction performance of WC, Cr3C2, and PTFE coatings using a pin-on-disk tribometer. The results showed that the wear-resistant coatings generally exhibited better wear resistance than the substrate material under various load conditions (correspond to the bench test PV of finger seal). The friction coefficient of the 40CrNiMoA substrate was 0.65, while the friction coefficients of WC, Cr3C2, and PTFE coatings were 0.22, 0.27, and 0.13, respectively, corresponding to 33.8%, 41.5%, and 20% of the friction coefficient of the 40CrNiMoA substrate. The friction coefficient of the PTFE coating was the lowest due to its self-lubricating property and showed a long service life under low loads; thus, this coating offers a promising solution to reduce the friction-caused hysteresis on a finger seal. Under loads of 20 N and 30 N, the service life of the WC coating was much longer than that of the Cr3C2 coating. Even at a load of 50 N, the service life of the WC coating was 4.3 times that of the Cr3C2 coating. The wear-resistant WC coating has strong application prospects in improving the service life of finger seals.

Durability and Measurement Uncertainty of Airtightness in Extremely Airtight Dwellings

In this paper a series of leakage tests is presented on extremely airtight dwellings, studying the durability of the airtightness level and the measurement uncertainty involved. All houses subjected to testing are certificated passive houses, meaning the maximum air leakage rate upon completion was n50 < 0.6 h-1 air changes per hour at 50 Pa pressure difference.In the literature, repeatability and reproducibility issues have been discussed by several authors, along with influences of weather conditions. However, it remains unclear to what extent the available uncertainty intervals are relative or absolute. With the current tendency towards extremely low leakage levels and the introduction of airtightness requirements in building codes, the further exploration of this issue has become crucial.Four aspects concerning air leakage tests are examined: the repeatability and reproducibility of the fan pressurization results in extremely airtight houses, the impact of weather conditions on the measurement results, the impact of the age of the construction, and the reproducibility of the airtightness level in repeated construction of virtually identical houses. The latter is limited to short term effects since all dwellings (n = 15) were completed after 2010.The results show similar relative repeatability and reproducibility intervals to those found in the literature. The rather large effects of weather conditions reported in previous studies could not be reproduced. Normal wear and tear due to occupation of the dwelling proved to introduce substantial relative deterioration of the airtightness of the building shell (20–100% increase in leakage), although in absolute value, the additional leakage was modest and the buildings remained very airtight. In general, it is concluded that pressurization tests render robust results in extremely tight construction, but with respect to ambitious leakage limits, test conditions and small preparation details such as the locking of window hardware can easily determine whether the dwelling will pass or fail.

Quantitative microleakage analysis of root canal filling materials in single-rooted canals.

The purpose of this study was to analyze the sealing ability of different root canal filling materials over a 6-week period using a glucose penetration model. Forty-six recently extracted human premolars were used in this study. The root canals were enlarged to 40/0.06. Prepared canals were randomly assigned into four groups (n = 10) as follows: Group 1, Gutta-Percha (GP)/AH Plus with cold lateral compaction; Group 2, GP/AH Plus with continuous wave compaction; Group 3, RealSeal SE obturation system; and Group 4, OrthoMTA. The remaining specimens were used as positive and negative controls, and all specimens underwent thermocycling (10,000; 5-55 °C). The sealing ability of all samples was evaluated at 24 h, 1, 2, 4, and 6 weeks using a quantitative glucose leakage model, and scanning electron microscope (SEM) images were taken. A mixed effect analysis using R statistical language was performed. Groups 1, 2, and 4 showed low leakage levels during experimental periods. Group 3 showed low leakage levels for the first 2 weeks; however, the leakage level was significantly increased after 2 weeks compared to negative control group (p < 0.05). In the SEM results, Group 3 showed imperfect dentin bonding, whereas Group 4 showed calcium silicate hydrate short tags, which are formed at the access of the dentin tubules. GP/AH Plus and OrthoMTA showed less microleakage than RealSeal SE obturation system when used as root canal filling materials. Traditional GP/AH Plus sealer and the newly developed OrthoMTA are more appropriate for ideal sealing of the root canals.

Leaking Water Networks: An Economic and Environmental Disaster

Water is the world's most precious resource, yet it is also the one which is almost universally mismanaged. As a result, water shortages are becoming ever more common. In the case of water supply and distribution networks, these manifest themselves in the intermittent operation of the system. Not only is this detrimental to the structural condition of the pipes, but can adversely affect the quality of the water delivered to the customer's taps. The cause is invariably leakage which often exceeds 50% of the production. Not only does this have a significant economic impact, but an environmental one too. But to recover leakage has a cost to undertake a hydraulic study of the network, create a permanent monitoring system and eliminate the leaks. So how low should leakage go and how can a lower leakage level be maintained over time? This is the objective of the very innovative EU funded PALM project recently completed in central Italy.

Multifunctional Up‐Converting Nanocomposites with Smart Polymer Brushes Gated Mesopores for Cell Imaging and Thermo/pH Dual‐Responsive Drug Controlled Release

AbstractMultifunctional nanocarriers based on the up‐conversion luminescent nanoparticles of NaYF4:Yb3+/Er3+ core (UCNPs) and thermo/pH‐coupling sensitive polymer poly[(N‐isopropylacrylamide)‐co‐(methacrylic acid)] (P(NIPAm‐co‐MAA)) gated mesoporous silica shell are reported for cancer theranostics, including fluorescence imaging, and for controlled drug release for therapy. The as‐synthesized hybrid nanospheres UCNPs@mSiO2‐P(NIPAm‐co‐MAA) show bright green up‐conversion fluorescence under 980 nm laser excitation and the thermo/pH‐sensitive polymer is active as a “valve” to moderate the diffusion of the embedded drugs in‐and‐out of the pore channels of the silica container. The anticancer drug doxorubicin hydrochloride (DOX) can be absorbed into UCNPs@mSiO2‐P(NIPAm‐co‐MAA) nanospheres and the composite drug delivery system (DDS) shows a low level of leakage at low temperature/high pH values but significantly enhanced release at higher temperature/lower pH values, exhibiting an apparent thermo/pH controlled “on‐off” drug release pattern. The as‐prepared UCNPs@mSiO2‐P(NIPAm‐co‐MAA) hybrid nanospheres can be used as bioimaging agents and biomonitors to track the extent of drug release. The reported multifunctional nanocarriers represent a novel and versatile class of platform for simultaneous imaging and stimuli‐responsive controlled drug delivery.

GIDL in Doped and Undoped FinFET Devices for Low-Leakage Applications

Investigation of gate-induced drain leakage (GIDL) in thick-oxide dual-gate doped- and undoped-channel FinFET devices through 3-D process and device simulations is presented. For a given gate length (LG) and gate dielectric thickness, the placement and grading of the drain junction and the channel doping are shown to have a tremendous impact on GIDL. Suppression of GIDL by as much as two orders of magnitude can be realized by formation of steep underlapped junctions for both doped- and undoped-channel devices. The prospect of low leakage levels in doped-channel high- VT FinFETs makes them suitable for memory cell applications.

Response to “Comment on ‘Open-circuit voltage dependency on hole-extraction layers in planar heterojunction organic solar cells’” [Appl. Phys. Lett. 100, 266101 (2012)

Yow-Jon Lin 1 had commented that our explanation on Voc relationship as a function of leakage current density in our paper 2 is not completely accurate. In this paper, we have not fully described the tendency of Voc increase in relation to reduction of leakage current density. Seeing inset of Fig. 3 at a glance gives the feeling that there is some tendency of Voc increase with reduction of leakage current density. But, we believe that this is not accurate analysis. Inset of Fig. 3 shows that only two or three data points are closer to the slope. A large deviation on the Voc relationship had existed with leakage current density values using our hole extraction layers; and this was our research motivation. Then, we investigated what could be the other parameters showing such tendency. It can be seen in the inset of Fig. 3, TAPC and NPB have high leakage levels as 10 4 mA/cm 2 range, their devices have high Voc values upto 1.1V. As a comparison 2-TNATA has a bit lower leakage level than TAPC and NPB, however, its Voc is about 0.95V. Therefore, these data could not explain the exact relationship between Voc and leakage current levels. Then, it was difficult to say as results showed somewhat deviation from a real diode. So, we analyzed more sensitive parameters to explain Voc variation. Mobility values and HOMO levels of hole extraction layers were revealed as such parameters to explain more accurately about the variation of Voc values rather than leakage current in our devices. Hence, in our paper, we said about the little tendency of VOC increase with reduction of leakage current density. There may have a little contributions to Voc by leakage current levels, our experimental results showed that leakage current cannot be a significant factor to determine the Voc values in our devices. The other parameters such as mobility values and HOMO levels should be given important consideration in determining the Voc of the devices. 1 Y.-J. Lin, Appl. Phys. Lett. 100, 266101 (2012). 2 C. Kulshreshtha, J. W. Choi, J. Kim, W. S. Jeon, M. C. Suh, Y. Park, and J. H. Kwon, Appl. Phys. Lett. 99, 023308 (2011).

Micro gas chromatography sample injector for the analysis of natural gas

This paper reports on a gas sample injection system for gas chromatography, with the specificity of being potentially able to sustain the harsh environment of natural gas. This device integrates six low-leak microvalves made from polyetheretherketone (PEEK) membranes on silicon substrates. We report on the design, operation principle, fabrication, and intrinsic characteristics of the micro injector as well as its measured behavior in a compact gas chromatograph. The overall size of the micro injector - 7 mm × 3 mm × 1.2 mm - is among the smallest reported in the literature, and it permits the injection of a 250-nL sample volume. Characterization revealed a transition time of less than 35 ms between the sampling mode and the injection mode of the microinjector, with an expected potential of high precision on injection sample volume, owing to the very low leakage levels. Continuous operation and reproducible measurements are demonstrated when using the micro injector in a miniaturized chromatographic system. Comparison with commercially available injectors revealed similar quality of gas sample injection.

Thermo and pH dual responsive, polymer shell coated, magnetic mesoporous silica nanoparticles for controlled drug release

In this paper, a kind of core–shell composite microsphere was prepared based on poly(N-isopropylacrylamide-co-methacrylic acid) (P(NIPAM-co-MAA)) coated magnetic mesoporous silica nanoparticles (M-MSN) via precipitation polymerization. The composite microsphere presented a thermo/pH-coupling sensitivity and the volume phase transition could be precisely regulated by the molar ratio of MAA to NIPAM or the concentration of NaCl. At physiological conditions (37 °C, 0.15 M NaCl), the P(NIPAM-co-MAA) shell underwent a distinct transition from a swollen state in pH 7.4 to a collapsed state in pH 5.0, so that the polymer shell was active in moderating the diffusion of embedded drugs in-and-out of the pore channels of MSN. Doxorubicin hydrochloride (DOX) was applied as a model drug and the behaviors of drug storage/release were investigated. The drug loaded behavior was pH-dependent, and the composite microsphere had a drug embed efficiency of about 91.3% under alkaline conditions. The cumulative in vitro release of the DOX-loaded composite microsphere showed a low level of leakage below the volume phase transition temperature (VPTT) and was significantly enhanced above its VPTT, exhibiting an apparent thermo/pH-response controlled drug release. The cytotoxicity assay of a blank carrier to normal cells indicated that the composite microspheres were suitable as drug carriers, while the DOX-loaded composite microspheres had a similar cytotoxicity to HeLa cells compared with free DOX. Therefore, the thermo/pH-sensitive composite microsphere could, in principle, be used for in vivo cancer therapy with a low premature drug release during blood circulation whilst having a rapid release upon reaching tumor tissues.

Very low leakage InGaAs/InAlAs pHEMTs for broadband (300 MHz to 2 GHz) low-noise applications

This paper presents the design, fabrication and characterisation of InGaAs–InAlAs high electron mobility transistors (pHEMTs) suitable for low-frequency LNA designs. Very low levels of leakage, in the order of 0.05 A/cm 2, are demonstrated by the pHEMTs, which have enabled the implementation of large-geometry, low-noise devices. Transistors with gate widths ranging from 200 μm to 1.2 mm are demonstrated to operate up to frequencies of 30 GHz. These are extremely promising as LNA components for implementation in broadband low-frequency systems as the very low-noise resistance simplifies matching requirements. The levels of leakage observed in our transistors further support the potential of the InGaAs/InAlAs material system as an alternative to Si when the CMOS roadmap comes to an end.

Temperature-Controlled Uptake and Release in PNIPAM-Modified Porous Silica Nanoparticles

Temperature-dependent uptake and release of small molecules within porous silica nanoparticles has been achieved by treatment of preformed, thiol-functionalized micro-to-mesoporous silica nanoparticles (MSN) with pyridyl disulfide-terminated poly(N-isopropylacrylamide) (PNIPAM−S−S−Py). The resulting nanoparticle−polymer composites show uptake and release of fluorescein at room temperature (below the lower critical solution temperature, LCST, of the polymer) and a low level of leakage at 38 °C (above LCST, <2% after 2 h). The data are consistent with a mode of action in which fluorescein diffusion occurs readily when the polymer is in the random coil conformation but is significantly retarded when the polymer adopts the globule conformation. This mode of action is opposite to that observed for systems in which the PNIPAM is grown from the porous silica surface or co-condensed with silica and is accompanied by a greater than 10-fold improvement in fluorescein retention in the “pore-closed” conformation.

Tunable electron-hole gases in gated InAs/GaSb/AlSb systems

Gated structures have been fabricated on the InAs/AlSb/GaSb system enabling the control of the relative electron and hole carrier densities in these type II crossed band gap structures. By using insulated gates, a wide gate voltage range, with very low leakage levels, is obtained, allowing the study of these systems from electron dominated transport through to hole dominated. Associated with this transition, a change from positive to negative transconductance is observed. Studies of the quantum Hall effect show features related to both electron and hole Landau level formation with the crossover from electron to hole dominated transport found to be a function of the perpendicular magnetic field.

The development of a new generation of split mechanical seals

Fully split seals are used for many purposes, such as to replace packings or to facilitate easy maintenance. A number of designs exist but are not convenient and do not reliably give the low levels of leakage required by the end user customer. Both of these issues were key considerations in the specification and development of a completely new range of split seals.

Avidin column as a highly efficient and stable alternative for immobilization of ligands for affinity chromatography

The avidin/biotin system was applied as a general mediator in the adsorption/desorption or immobilization of biologically active macromolecules to solid supports. In this context, model biotinylated proteins (lectins and antibodies) were attached to avidin-coupled Sepharose. As examples for affinity chromatography, peanut agglutinin and anti-transferrin antibody were used to isolate asialofetuin and transferrin, respectively. The capacity and product yields were significantly better than those achieved with conventional affinity chromatography on CNBr-activated Sepharose columns containing the same lectin or antibody. Moreover, the columns were characterized by improved stability properties exhibiting remarkably low levels of leakage.

Reduced renal reabsorption of 1,5-anhydro-D-glucitol in diabetic rats and mice.

A stable amount, approximately 60 micrograms, of 1,5-anhydro-D-glucitol (AG) was detected in the 24-h-urine of normal young rats fed ad libitum. Upon administration of streptozotocin (STZ), this amount was temporarily elevated to as much as 1.1 mg and AG was concomitantly removed from the circulation. The plasma AG level stayed almost null thereafter while the acutely elevated urinary AG excretion declined within 24 h to another stable excretion level that was three times as high as that of the untreated rats. In contrast, glucosuria developed much more slowly in the drug-treated rats. Normal rats and mice retained exogenous [14C]AG to a considerable extent and the radioactivity was distributed all over the body. Only a marginal fraction of the radioactivity was excreted as expired CO2. The radio-activities retained in the body and excreted into the urine were mostly attributed to unmetabolized AG. The observations of AG's metabolic stability and its relatively low level of leakage into urine suggested the concept of effective renal AG reabsorption. On the other hand, the rats with STZ-induced diabetes and NOD-mice with spontaneously developed diabetes retained little of the radioactive AG in their bodies; most of the injected radioactivity was recovered in the urine within 24 h. This observation was interpreted as due to reduced renal AG reabsorption in these animals. The concept of reduction in renal AG reabsorption in diabetes could account for the reduced plasma AG level generally observed in human diabetic cases.

Electrical Characteristics of Anodized Niobium Foil and Sintered Pellets

Anodized niobium foil and sintered pellets were evaluated in terms of capacitance, leakage, and dissipation factor. Calculated film thickness was shown to be proportional to forming voltage. Field strength in the oxide after anodization was an exponential function of reciprocal absolute temperature for films formed at 25 ma/in.2, but not at 2.5 ma/in.2. An average charge value of 82µf v/in.2 was found for foils anodized over a forming potential range of 50–250 v, and between temperatures of 25° and 100°C. Sintering pellets at 2100°C and using 0.01% electrolyte permits anodization to 200 v. Several solid electrolyte capacitors were prepared which had low leakage levels at 35 working volts.