286 research outputs found
Detrended fluctuation analysis of the soft breakdown current
No full textWe have addressed the problem of the gate current fluctuations after soft breakdown in thin gate oxides, mainly focused on the intrinsic instability of SB conductance. We found that heavily degraded oxides exhibit large instability and more complex fluctuations. Finally we have developed a model to describe the gate distribution of the gate current fluctuations by taking in account such conductance instability. (C) 2001 Elsevier Science B.V. All rights reserved
Wear-out and breakdown of ultra-thin oxides after exposure to ionising radiation
No full textIn this work we show that electrical stresses produce HB or Soft Breakdown (SB) in ion irradiated oxides in times much shorter than in unirradiated oxides. Hence, the device life-time is substantially reduced due to the formation of localized damaged regions by ion irradiation. Even though these weak regions may drive small or negligible currents just after irradiation, they can facilitate the onset of breakdown phenomena, which can be observed for a small stress voltage applied, down to 2V, which is close to the operating voltage
Soft Breakdown Current Noise in Ultra-thin Gate Oxides
No full textIn this work we studied the soft breakdown (SB) in ultra-thin gate oxides (<3 nm) subjected to constant current stress. SB current derives from the superposition of several random telegraph signals noises with different time constants and amplitudes. Such fluctuations derive from the conductance modulation of a damaged region inside the oxide layer, due to the electrical stress. We found that the current noise power density follows the 1/f(2) power law (with α between 1 and 2) over a wide range of frequency (1 Hz-100 kHz). Only at frequency smaller than 1-10 Hz a possible deviation from this low cannot be excluded. Moreover, the discrete fluctuations typical of SB are statistically independent events at least over time periods around hundreds of seconds, according to a Poisson process. This result suggest that electron trapping/detrapping in defect sites near or inside the SB conductive path can be claimed as responsible for such conductance modulation. (C) 2002 Elsevier Science Ltd. All rights reserved
Incidence of Oxide and Interface Degradation on MOSFET Performance
No full textIn this work we have studied how oxide and interface degradation affect the performance of MOSFETs with ultra-thin gate oxide, in terms of transconductance (gm), saturation drain current (Ids,SAT), and threshold voltage (Vth) before Soft Breakdown and Hard Breakdown. MOSFET transconductance and drain current decrease due to oxide traps which act as interface state reducing channel carrier mobility and enhancing the drain current noise. We found strong correlation between these traps and the well known Stress Induced Leakage Current (SILC) indicating that the same traps producing the degradation of MOSFET characteristics are those involved in SILC conductio
Il messaggio d'Enea (un momento alto della vita)
No full textLa prefazione presenta il volume in cui Filomena Giannotti, docente dell'Univ. di Siena, ha raccolto e commentato tutte le testimonianze del grande poeta italiano Giorgio Caproni relative al suo 'incontro' con la settecentesca statua di Enea in fuga da Troia con in spalla il padre Anchise, e per mano il figlioletto Ascanio (opera di Francesco Baratta). Tale incontro avvenne poco dopo la Seconda Guerra Mondiale, in Piazza Bandiera, a Genova, una delle piazze più bombardate d'Italia. Caproni fu sorpreso e commosso di trovarsi davanti proprio Enea, in quella raffigurazione, e in quel momento della Storia d'Italia. Enea divenne per lui il simbolo dell'uomo della sua generazione, solo, con sulle spalle una tradizione vecchia e consunta, e davanti un futuro tutto da costruire. L'incontro divenne così fondamentale, che Caproni continuò a ritornarvi sopra fino ai suoi ultimi giorni, con articoli, testimonianze, e - soprattutto - con il poemetto "Il passaggio d'Enea"
Logistic Modeling of Progressive Breakdown in Ultrathin Gate Oxides
No full textThe sigmoidal behavior exhibited by the current-time characteristics of constant voltage stressed MOS capacitors with ultrathin oxides is ascribed to a self-constrained increase of the leakage sites population that assist the conduction process between the electrodes. To analytically describe this dynamical process we consider a classical model of population growth theories such as the Verhulst differential equation. The role played by the background tunneling current in the detection of the breakdown event is also discussed
Reliable measurement of single cell fluorescence distribution using a standard microscope set-up
No full textBackground: Quantifying gene expression at single cell level is fundamental for the complete characterization of synthetic gene circuits, due to the significant impact of noise and inter-cellular variability on the system's functionality. Commercial set-ups that allow the acquisition of fluorescent signal at single cell level (flow cytometers or quantitative microscopes) are expensive apparatuses that are hardly affordable by small laboratories. Methods: A protocol that makes a standard optical microscope able to acquire quantitative, single cell, fluorescent data from a bacterial population transformed with synthetic gene circuitry is presented. Single cell fluorescence values, acquired with a microscope set-up and processed with custom-made software, are compared with results that were obtained with a flow cytometer in a bacterial population transformed with the same gene circuitry. Results: The high correlation between data from the two experimental set-ups, with a correlation coefficient computed over the tested dynamic range > 0.99, proves that a standard optical microscope- when coupled with appropriate software for image processing- might be used for quantitative single-cell fluorescence measurements. The calibration of the set-up, together with its validation, is described. Conclusions: The experimental protocol described in this paper makes quantitative measurement of single cell fluorescence accessible to laboratories equipped with standard optical microscope set-ups. Our method allows for an affordable measurement/quantification of intercellular variability, whose better understanding of this phenomenon will improve our comprehension of cellular behaviors and the design of synthetic gene circuits. All the required software is freely available to the synthetic biology community (MUSIQ Microscope flUorescence SIngle cell Quantification).</p
Nepal: monarchia, maoismo, questione agraria
No full textIl lavoro, facendo riferimento allo schema concettuale approntato da Samuel Huntington per l'analisi dei fenomeni di modernizzazione socio-politica di seconda generazione, ripercorre sinteticamente le principali fasi della storia del Nepal come stato unitario, facendo riferimento in particolare ai seguenti punti nevralgici: la monarchia assoluta e la sua scarsa capacità di assorbire le spinte partecipative, l'instabilità dei governi parlamentari e la guerra civile, da poco conclusa, portata avanti dai maoisti sotto la bandiera della redistribuzione delle terre ai contadini
- …
