Thermal Trap Research Articles

Characteristics of Hot Hole Injection, Trapping, and Detrapping in Gate Oxide of Polycrystalline Silicon Thin-Film Transistors

The characterization and modeling of the hysteresis phenomenon observed in the off-state regime of n-channel polycrystalline thin-film transistors are presented. The shift in Id–Vg characteristics between upward and downward scan were measured under various bias conditions and ambient temperatures. The localized positive charge build-up induced by band-to-band hot hole injection is responsible for the mechanism for reducing the off-leakage current, and it is recovered through the thermal emission of trapped holes, which is enhanced by self-heating of the device during the on-current conduction. On the basis of this model, the internal device characteristics related to the thermal and oxide trap properties are analyzed.

Characterization of deep energy level defects in α-Al2O3:C using thermally assisted OSL

Abstract Commercially available α-Al2O3:C powder was studied for deep energy level defects by a newly suggested method using thermally assisted optically stimulated luminescence (TA-OSL) phenomenon. The method involves simultaneous application of continuous wave optically stimulated luminescence (CW-OSL) as well as thermal stimulation up to 400 °C, using a linear heating rate of 4 K/s. By using this method, two well-defined peaks at 121 °C and 232 °C were observed. These TA-OSL peaks have been correlated to two different types of deeper defects which can be bleached at 650 °C and 900 °C respectively on thermal treatment. These deeper defects, having larger thermal trap depth and relatively lower photoionization cross-section at room temperature for stimulation with blue LED (470 nm), are stable up to 500 °C, so they can store absorbed dose information even if the sample is inadvertently exposed to light or temperature. As only a fraction of signal is bleached during TA-OSL readout, multiple readouts could be performed on an exposed sample using this technique. The dose vs TA-OSL response from deep traps of α-Al2O3:C was found to be linear up to 10 kGy, thus extending its application for high dose dosimetry. The value of thermally assisted energy (EA) associated with these traps in α-Al2O3:C has been determined to be 0.268 eV and 0.485 eV respectively and the corresponding values of photoionization cross-section at room temperature (25 °C), for optical stimulation with blue light (470 nm), are 5.82 × 10−20 and 3.70 × 10−22 cm2, respectively. The process of thermally assisted OSL has been formulated analytically as well as theoretically for describing the temperature dependence of optical cross-section and evaluation of thermally assisted energy associated with deep traps.

Asymmetric current flow in a native oxide/indium selenide heterostructure

This paper examines for the first time the current-voltage behavior of native oxide/InSe heterostructures with the native oxide grown at room temperature on a cleaved (0001) InSe surface and analyzes the processes that determine the shape of their current-voltage curves. The native oxide is shown to be an insulator with an electric conductivity of ∼10–11 S/cm and a relative static dielectric permittivity of 10.37 at room temperature. Low bias voltages lead to monopolar carrier injection into the oxide layer. At sufficiently high bias voltages, thermal field trap ionization (Poole-Frenkel effect) and thermionic emission occur. The asymmetry of the current-voltage behavior of native oxide/InSe heterostructures may be due to different trap concentrations and the difference in the trap energy distribution between the near-surface region of the oxide film and the native oxide/semiconductor substrate interface.

Reliability characteristics of metal-oxide-semiconductor capacitors with 0.72 nm equivalent-oxide-thickness LaO/HfO 2 stacked gate dielectrics

La-incorporated HfO 2 could improve the thermal stability and interface trap quality. Laminated structures with different doping positions and thicknesses were fabricated by RF magnetron co-sputtering method. The physical and electrical properties of HfO 2/HfLaO/p-Si and HfLaO/HfO 2/p-Si structures after 850 °C postannealing were analyzed. And the time dependent dielectric breakdown (TDDB) characteristics were also analyzed for metal-oxide-semiconductor (MOS) capacitors with atomic-layer-deposited (ALD) HfLaO gate dielectrics. For TDDB characteristics, the Weibull slopes were independent of stress voltages and capacitor areas, but they were dependent on the stress temperatures. The electric-field acceleration parameter ( γ) is about 4.3–4.5 MV/cm. The maximum voltage ( V g) for 10-year TDDB lifetime under 85 °C operation is V g = 2.03 V, or equivalently 6.1 MV/cm.

Preparations and temperature‐ and pH‐dependent release property of ethylcellulose microcapsules containing N‐isopropylacrylamide copolymer

AbstractMicrocapsules composed of poly(N‐isopropylacrylamide‐co‐methacrylic acid) [P(NIPAM‐co‐MAA)] cores and ethylcellulose matrix were prepared by an emulsification and spray‐drying method. First, water‐in‐oil (W/O) emulsions were prepared using P(NIPAM‐co‐MAA) solution in distilled water (3%) as a water phase, and ethylcellulose solution in dichloromethane (8%) as an oil phase. The emulsion was spray‐dried around 50°C to evaporate dichloromethane, and then the resulting particle was air‐dried to remove residual water. Blue dextran loaded in the cores of microcapsules readily released below lower critical solution temperature (LCST) but the release was suppressed above the phase transition temperature. It is believed that the NIPAM copolymer acts as a thermal trap for blue dextran when temperature is above LCST. In addition, the microcapsules were also pH‐sensitive in terms of release, which could be explained by the pH‐dependent contraction and expansion of the copolymer. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

Thermal Trap for DNA Replication

The hallmark of living matter is the replication of genetic molecules and their active storage against diffusion. We implement both in the simple nonequilibrium environment of a temperature gradient. Convective flow both drives the DNA replicating polymerase chain reaction while concurrent thermophoresis accumulates the replicated 143 base pair DNA in bulk solution. The time constant for accumulation is 92 s while DNA is doubled every 50 s. The experiments explore conditions in pores of hydrothermal rock which can serve as a model environment for the origin of life.

VOLATILE CONSTITUENTS OF CHAROPHYTES AS OVIPOSITION DETERRENTS OFCULEX PIPIENS PALLENS(DIPTERA: CULICIDAE)

Four populations of charophytes (including three species), Chara inconnexa T. F. Allen (populations 1 and 2), C. vulgaris L., and Nitellopsis obtusa (Desv.) J. Groves, were studied for effective chemicals as oviposition deterrents of Culex pipiens pallens. The charophyte volatile organic compounds (VOCs) were retained in Tenax GR, subsequently desorbed using a thermal desorption cold trap injector (TCT), and analyzed by gas chromatography/mass spectrometry (GC/MS) to elucidate that charophytes have repellent properties. C. inconnexa (1) and C. inconnexa (2) exhibited strong repellent activities, and C. vulgaris showed some repellent activity against C. pipiens pallens with terpenes and benzothiazole playing major roles, while N. obtusa lacked those compounds and did not have an effect. These results suggest that charophytes have potential application as pesticides, but there are interspecific differences. In addition, benzene hydrocarbons were among the volatiles in Chara but not in N. obtusa, implying that some charophytes could be used to absorb these compounds.

Real-time trace detection of security-relevant compounds in complex sample matrices by thermal desorption–single photon ionization–ion trap mass spectrometry (TD-SPI-ITMS) Spectrometry (TD-SPI-ITMS)

For the detection of security-relevant substances at low concentrations in complex matrices, coupling of thermal desorption-single photon ionization-ion trap mass spectrometry (TD-SPI-ITMS) was successfully tested. The main advantage of taking solid samples with a wipe pad followed by thermal desorption is the low detection limit by enhanced vapor pressure. Single photon ionization is a soft ionization technique which reduces the target ion fragmentation and shields bulk components with high ionization energies (IE) like nitrogen yielding to clearly arranged mass spectra with significant high mass peaks. To obtain low false-positive and false-negative rates, especially necessary for security-relevant substances, the ion trap mass spectrometer allows identification of signals with MS/MS studies. In this concept, the soft ionization technique fits well with the MS/MS studies, as peaks with high masses are generated yielding significant MS/MS fragments. For the ionization, photon energies between about 8 eV (155 nm) and 12 eV (103 nm) were generated with electron-beam-pumped rare gas excimer lamps (EBEL). Depending on the rare gas used, light with different photon energy is generated, adapted to the substances of interest. So, even most narcotics, having relatively low IEs, can be ionized with 8.4 eV photons without massive fragmentation. For most explosives, photons with higher energy must be used as their IEs are higher. In this work, a mobile setup with a commercial ion trap mass spectrometer has been developed and tested. Even a first real-scenario measurement campaign was accomplished successfully proving the field-suitability of the system.

Charge transport mechanism in amorphous alumina

The charge transport mechanism in amorphous Al2O3 was examined both experimentally and theoretically. We have found that electrons are dominant charge carriers in Al2O3. A satisfactory agreement between the experimental and calculated data was obtained assuming the multiphonon ionization mechanism for deep traps in Al2O3. For the thermal and optical trap ionization energies in Al2O3, the values WT=1.5 eV and Wopt=3.0 eV were obtained.

Perylrene-based n-type field-effect transistors prepared by the neutral cluster beam deposition method

We present the first application of the neutral cluster beam deposition (NCBD) method to prepare n-type organic thin-film transistors with a top-contact structure based on N,N′-ditridecylperylene-3,4,9,10-tetracarboxylic diimide (P13). Systematic analysis was carried out to examine the effects of surface passivation and thermal post-treatment on the morphology and crystallinity of P13 active layers and device performance, together with operational stability as a function of time. The high room-temperature field-effect mobility of 0.58 cm 2/Vs for the thermally post-treated devices was obtained under ambient conditions. The comparative study of the transport mechanisms responsible for conduction of the electron carriers over a temperature range of 10–300 K indicated that surface modification and thermal post-treatment decrease total trap density and activation energy for carrier transport by reducing structural disorder.

A Thermal Desorption Chemical Ionization Ion Trap Mass Spectrometer for the Chemical Characterization of Ultrafine Aerosol Particles

The development of a thermal desorption chemical ionization ion trap mass spectrometer for the chemical characterization of ultrafine aerosol particles is reported and first experimental results are presented. Atmospheric particles are size-classified and collected using a unipolar charger, a radial differential mobility analyzer and an electrostatic precipitator, and analyzed after thermal desorption and chemical ionization using an ion trap mass spectrometer. Integration of an ion trap mass spectrometer allows for fast scans of the entire mass spectrum every 0.5 s and bears the potential to identify unknown particulate compounds by tandem mass spectrometry. Particle collection efficiencies range from 90–100% for 25 nm particles to about 50% for 40 nm particles. In the current configuration, the absolute sensitivity of the instrument with regard to ammonium is in the range of 10–100 pg NH + 4 . In ambient samples collected in the Colorado Front Range, NH + 4 was the major signal peak in the positive ion ...

Thermal Stability and Memory Characteristics of HfON Trapping Layer for Flash Memory Device Applications

We report on the thermal stability and trap characteristics of HfON as a trapping layer in charge trap flash memory device applications. Compared to HfO 2 , HfON prepared by NH 3 annealing of HfO 2 exhibits good interfacial quality, excellent memory properties, and superior thermal stability. The improvement in thermal stability can be explained by the lower interfacial reaction and amorphous state of HfON. The activation energy of a SiO 2 /HfON/Al 2 O 3 device and the trap level of the HfON trapping layer were found to be 1.08 and 1.04 eV, respectively.

Volatile flavour constituent patterns of Terras Madeirenses red wines extracted by dynamic headspace solid‐phase microextraction

A suitable analytical procedure based on static headspace solid-phase microextraction (SPME) followed by thermal desorption gas chromatography-ion trap mass spectrometry detection (GC-(ITD)MS), was developed and applied for the qualitative and semi-quantitative analysis of volatile components of Portuguese Terras Madeirenses red wines. The headspace SPME method was optimised in terms of fibre coating, extraction time, and extraction temperature. The performance of three commercially available SPME fibres, viz. 100 mum polydimethylsiloxane; 85 mum polyacrylate, PA; and 50/30 mum divinylbenzene/carboxen on polydimethylsiloxane, was evaluated and compared. The highest amounts extracted, in terms of the maximum signal recorded for the total volatile composition, were obtained with a PA coating fibre at 30 degrees C during an extraction time of 60 min with a constant stirring at 750 rpm, after saturation of the sample with NaCl (30%, w/v). More than sixty volatile compounds, belonging to different biosynthetic pathways, have been identified, including fatty acid ethyl esters, higher alcohols, fatty acids, higher alcohol acetates, isoamyl esters, carbonyl compounds, and monoterpenols/C(13)-norisoprenoids.

Analysis of Volatile Organic Compounds (VOCs) in the Urban Atmosphere of Beijing

In order to understand the average concentrations of ambient volatile organic compounds (VOCs) in the urban atmosphere of Beijing, a diffusive sampling device (DSD-voc) was used to adsorb VOCs. The adsorbates were analyzed by gas chromatography/mass spectrometry (GC/MS) using a thermal desorption cold trap injector (TCT) and determined according to the EPA Method TO14. Sampling for 24 h a day was conducted at five sites continuously for one week from October 24 to 30, 2006. Sixteen VOCs were detected and the weekly average values were calculated for each site, with the maximum and minimum VOC concentration values of 135.1 and 77.3 μg/m3. Benzene, toluene, ethylbenzene, m,p-xylenes and o-xylene (BTEX) account for almost three quarters of the detected VOCs and these correlate well with each other among sites, suggesting the main emission sources are vehicular emissions.

A conceptual high flux reactor design with scope for use in ADS applications

A 100 MWt reactor design has been conceived to support flux level of the order of 1015 n/cm2/s in selected flux trap zones. The physics design considers high enriched metallic alloy fuel in the form of annular plates placed in a D2O moderator tank in a hexagonal lattice arrangement. By choosing a tight lattice pitch in the central region and double the lattice pitch in the outer region, it is possible to have both high fast flux and thermal flux trap zones. By design the flux level in the seed fuel has been kept lower than in the high flux trap zones so that the burning rate of the seed is reduced. Another important objective of the design is to maximize the time interval of refueling. As against a typical refueling interval of a few weeks in such high flux reactor cores, it is desired to maximize this period to as much as six months or even one year. This is possible to achieve by eliminating the conventional control absorbers and replacing them with a suitable amount of fertile material loading in the reactor. Requisite number of seedless thorium-aluminum alloy plates are placed at regular lattice locations vacated by seed fuel in alternate fuel layers. It is seen that these thorium plates are capable of acquiring asymptotic fissile content of 14 g/kg in about 100 days of irradiation at a flux level of 8 × 1014 n/cm2/s. In summary, the core has a relatively higher fast flux in the central region and high thermal flux in the outer region. The present physics design envisages a flat core excess reactivity for the longest possible cycle length of 6 months to one year. It is also possible to modify the design for constant subcriticality for about the same period or longer duration by considering neutron spallation source at the centre and curtailing the power density in the inner core region by shielding it with a layer of thoria fuel loading.

Preterm Birth: The Interaction of Traffic-related Air Pollution with Economic Hardship in Los Angeles Neighborhoods

Preterm birth may be affected by the interaction of residential air pollution with neighborhood economic hardship. The authors examined variations in traffic-related pollution exposure--measured by distance-weighted traffic density--using a framework reflecting the social and physical environments. An adverse social environment was conceptualized as low socioeconomic status (SES) neighborhoods--census tracts with concentrated poverty, unemployment, and dependence on public assistance. An adverse physical environment was depicted by the winter season, when thermal inversions trap motor vehicle pollutants, thereby increasing traffic-related air pollution. Los Angeles County, California, birth records from 1994 to 1996 were linked to traffic counts, census data, and ambient air pollution measures. The authors fit multivariate logistic models of preterm birth, stratified by neighborhood SES and third pregnancy trimester season. Traffic-related air pollution exposure disproportionately affected low SES neighborhoods in the winter. Further, in these poorer neighborhoods, the winter season evidenced increased susceptibility among women with known risk factors. Health insurance was most beneficial to women residing in neighborhoods exposed to economic hardship and an adverse physical environment. Reducing preterm births warrants a concerted effort of social, economic, and environmental policies, focused on not only individual risk factors but also the reduction of localized air pollution, expansion of health-care coverage, and improvement of neighborhood resources.

Speciation of Volatile Aromatic and Chlorinated Hydrocarbons in an Urban Atmosphere Using TCT-GC/MS

Several aromatic and chlorinated volatile hydrocarbons (VOCs) were measured in Vitoria-Gasteiz City (Spain) throughout the years 1999 and 2002 in order to find out the concentration of these pollutants in urban air. These VOCs were retained in Tenax TA, subsequently desorpted by using a thermal desorption cold trap injector (TCT), and thereafter analyzed by gas chromatography/mass spectrometry (GC/MS). This analytical methodology permits the determination of 42 VOCs at very low concentrations, although only 32 of them were found in the urban air of the city (ranging from 205.51 to 0.01 μg m−3), with high reproducibility (%RSD lower than 10%). Twenty-four-hour samples were taken each sampling day to ascertain their total daily concentration, and rigorous quality controls were carried out to check the representativeness of sampling. Results of this exhaustive study show that toluene (T), xylenes (X), ethylbenzene (E), and benzene (B) were, respectively, the most abundant of these VOCs in the urban area during that period. The total concentration of BTEX represented, on average, more than 72.6% of the VOC total concentration, with the highest concentrations being reached in autumn, except for benzene and derived compounds (in winter). Benzene was the minority BTEX pollutant, its yearly mean concentration being less than the maximum established by the European Directive 2000/69/CE (5 μg m−3).

Optimization and validation of a method of analysis for fenitrothion and its main metabolites in forestry air samples using sorbent tubes with thermal desorption cold trap injection and gas chromatography–mass spectrometry

An analytical methodology using thermal-desorption cold trap (TCT) and GC–MS was developed for the determination of the insecticide fenitrothion and its main metabolites, 3-methyl-4-nitrophenol and fenitrooxon, in forestry atmospheres. The sampled atmosphere was pumped through a glass tube containing 100mg of Tenax adsorbent at a flow rate of 50mlmin−1. Adsorption/thermal desorption and breakthrough experiments were performed to test the ability to quantitatively trap the compounds. The detection limits of method for these compounds ranged between 1.6 and 2.1ngm−3. This methodology was developed to evaluate the persistence of fenitrothion in forest atmospheres after treatment. Spray application at 21.5mgactive ingredientm−2 resulted in atmosphere levels of the insecticide of 78.3ngm−3 (after 2h of application). Within 2–4 days following treatment, the presence of fenitrooxon fell to 50–55%. During this period residues of metabolites began to appear, disappearing 19 days later.

Multisorbent tubes sampling used in thermal desorption cold trap injection with gas chromatography-mass spectrometry for C2–C6 hydrocarbon measurements in an urban atmosphere

Three solid adsorbents (Carbotrap, Carbotrap C, and Carbosieve III) were evaluated for sampling trace non-methane hydrocarbons in urban atmospheres. The sampled atmosphere was pumped through a multisorbent tube containing the three sorbents separated by a small amount of silanized glass wool. The trapped compounds were recovered by thermal desorption and analysed by combining cryogenic enrichment with gas chromatography and mass spectrometry. Adsorption/thermal desorption and breakthrough experiments were performed to test their ability to quantitatively trap the light hydrocarbons. The technique was suitable for determination of low ppbv concentrations of these compounds. Ambient atmospheric sampling was conducted in Vitoria-Gasteiz (Basque Country, Spain), and the measurements cover a period of one year (2001–2002). Fifteen C2–C6 hydrocarbons are identified and quantified, and seasonal trends are discussed.

Temperature Preferences and Critical Thermal Limits of Burbot: Implications for Habitat Selection and Ontogenetic Habitat Shift

In large lakes, burbot Lota lota utilize several habitats during their ontogenesis. While juveniles are typically littoral dwellers, adults often prefer the cold profundal waters, especially during the summer months. Such distinct seasonal or ontogenetic habitat shifts are often induced by proximate abiotic factors that guide the fish toward another habitat in which either physiological performance is optimized or survival is increased. Temperature is often considered to be such a factor, especially in cold-stenothermal species. In thermal gradient experiments, the effects of the acclimation temperature (AT) on the preferred temperature (PT) and the critical thermal maximum and minimum of burbot were studied. A significant nonlinear relationship was found between PT and AT in small (10−20 cm total length) burbot (SEs in parentheses): PT = −2.1363 (±0.5455) AT + 0.0732 (±0.0207) AT2 + 26.2708 (±3.2075). The final temperature preferendum was 11.4°C. For large (20−30 cm) burbot, no such relationship between acclimation temperature and preferred temperature was found, and a final temperature preferendum of 14.2°C was calculated. Both size-classes showed a positive linear relationship between the critical thermal maximum (CTMa) and AT: CTMa = 0.3254 (±0.0198) AT + 25.1106 (±0.2676) (R2 = 0.94) for small burbot, and CTMa = 0.3688 (±0.0276) AT + 24.2986 (±0.3742) (R2 = 0.91) for large burbot. A critical thermal minimum of 3.3°C was found for small burbot acclimated to 19.6°C. The results show that even during summer the littoral water temperature in Lake Constance is very unlikely to force juvenile burbot towards the cold profundal zone. However, the data provide good evidence that changes in water temperature in spring do act as a trigger for the juveniles to leave the littoral to avoid a thermal trap during summer.