Experimental method for the determination of the energydistribution of stress-induced oxide traps

An experimental procedure for the determination of the energy distribution of oxide neutral traps is presented, showing the evolution of the stress-induced damage as a function of Fowler-Nordheim stress fluence and field. It is shown that the traps are mainly distributed around 2 eV from the oxide conduction band. Results are presented for different oxide technologies, investigating the effect of oxide nitridation and growth conditions on the trap energy distribution     

Small and large scale segmental motion in polymers: estimating cooperativity length by ordinary relaxation experiments

We derive a suitable expression for estimating the size of the cooperatively rearranging regions (CRRs) in supercooled polymer melts by fitting data worked out by ordinary relaxation experiments carried out in isothermal conditions. As an example, the average CRR size in poly(n‐butyl methacrylate) in proximity to the glass transition temperature is derived from a stress relaxation experiment performed by means of an atomic force microscopy setup. Good agreement is found with results in the literature derived from measurements of temperature fluctuations (the so‐called Donth method). The temperature dependence of the CRR size is explored for poly(butadiene); in this case the segmental relaxation function is derived through a novel method for the analysis of the efficiency with which free induction decay echoes are refocused in ¹H NMR experiments. It is found that the CRR size increases upon cooling. The results derived from the analysis of the NMR data are found to be in satisfactory agreement with those worked out from broadband dielectric spectroscopy data in the literature. © 2015 Society of Chemical Industry     

太阳广场——公共市场及中转枢纽

项目地点:委内瑞拉加拉卡斯项目类型:公共服务中心开工日期:未定该项目获2005年豪瑞可持续建筑大奖赛拉丁美洲地区提名奖     

LCA of domestic and centralized biomass combustion: The case of Lombardy (Italy)

This paper analyzes and compares the environmental impacts of biomass combustion in small appliances such as domestic open fireplaces and stoves, and in two types of centralized combined heat and power plants, feeding district heating networks. The analysis is carried out following a Life Cycle Assessment (LCA) approach. The expected savings of GHG (greenhouse gases) emissions due to the substitution of fossil fuels with biomass are quantified, as well as emissions of toxic pollutants and substances responsible for acidification and ozone formation.The LCA results show net savings of GHG emissions when using biomass instead of conventional fuels, varying from 0.08 to 1.08 t of CO₂ eq. per t of dry biomass in the different scenarios. Avoided GHG emissions thanks to biomass combustion in Lombardy are 1.32 Mt year^?1(1.5% of total regional GHG emissions). For the other impact categories, the use of biomass in district heating systems can again cause a consistent reduction of impacts, whereas biomass combustion in residential devices shows higher impacts than fossil fuels with a particular concern for PAH, VOC and particulate matter emissions. For example, in Lombardy, PM10 emissions from domestic devices are about 8100 t year^?1, corresponding to almost one third of the total particulate emissions in 2005.     

Superconducting Fluctuating Diamagnetism Versus Precursor Diamagnetism in Heterogeneous Superconductors

The fluctuation-induced diamagnetism (FD) above the transition temperature T _c is studied through the isothermal field-dependence of the diamagnetic magnetization M _dia. While for T ≈ T _c and H→0 one has –M _dia ∝ (H)^1/2,on increasing field an upturn occurs and begins to decrease, in correspondence to field-induced quenching of the fluctuating pairs. For BCS superconductors (SC) as MgB₂ the upturn field H _up is in the range 100–800 Oe, while in optimally doped high-temperature SC(HT _c SC) H _up is expected in the range of several Tesla, because of the small coherence length. At variance, in non-homogeneous HT _c SC (under- or overdoped) or in the presence of impurities causing diffuse transition, strong increase of M _dia and H _up reduced by order of magnitudes are observed. The reasons of these behaviors are discussed in the report. In particular the difference between the FD in heterogeneous HT _c SC (related to SF) and the precursor diamagnetism for diffuse transitions such as in Al-doped MgB₂ (unrelated to SF) is emphasized and it is shown how the temperature dependence of H _up discriminates between the two effects.     

Modeling of SILC based on electron and hole tunneling. I. Transienteffects

A detailed investigation of the steady-state and transient leakage currents in thin oxides is proposed. The experimental data are compared with numerical results obtained from a model based on an inelastic trap-assisted tunneling process, which includes both electron and hole contributions. In order to accurately reproduce the transient discharge currents, a continuous distribution of oxide traps was adopted. The energies of these levels can be either in correspondence of the conduction or valence band edges of the adjacent silicon/polysilicon layers. Both electrons and holes contribute to the transient stress-induced leakage current (SILC), but the extracted trap densities cannot account for the steady-state SILC. A different mechanism, involving trap levels with energy aligned to the energy gap of the silicon layers is proposed and is developed in the following paper. The model can be applied to any type of device and bias conditions and may be used to correctly recognize the role of electron and hole SILC and the spatial and energy distribution of defect states     

Modeling of SILC based on electron and hole tunneling. II.Steady-state

For pt. I see ibid., vol. 47, no. 6 (June 2000). A numerical model for the stationary stress-induced leakage current (SILC) is presented, accounting for both electron and hole tunneling. Detailed comparisons against experimental results on both n- and p-channel devices highlight that the steady-state SILC is due to positively charged centers, with an energy level located in correspondence of the silicon bandgap. Electron-hole recombination at these sites dominates normal trap-assisted tunneling at low oxide fields, and successfully accounts for recently observed hole steady-state leakage. The contribution from neutral traps seems instead marginal. Based on this new picture, the impact of the recombination process on the leakage properties of ultrathin gate is also discussed     

Extended Excentric Labeling

The paper presents an extension to the Excentric Labeling, a labeling technique to dynamically show labels around a movable lens. Each labels refers to one object within the lens and is connected to it through a line. The original implementation has several known limitations and potential improvements that we address in this work, like: high density areas, uneven density distributions, and summary statistics. We describe the implemented extensions and present a think-aloud user study. The study shows that users can naturally understand and easily operate the majority of the implemented function but label scrolling, which requires additional research. From the study we also gained unanticipated requirements and interesting directions for further research.