Ionizing radiation induced leakage current on ultra-thin gate oxides

MOS capacitors with a 4.4 nm thick gate oxide have been exposed to gamma radiation from a Co-60 source. As a result, we have measured a stable leakage current at fields lower than those required for Fowler-Nordheim tunneling. This Radiation Induced Leakage Current (RILC) is similar to the usual Stress Induced Leakage Currents (SILC) observed after electrical stresses of MOS devices. We have verified that these two currents share the same dependence on the oxide field, and the RILC contribution can be normalized to an equivalent injected charge for Constant Current Stresses. We have also considered the dependence of the RILC from the cumulative radiation dose, and from the applied bias during irradiation, suggesting a correlation between RILC and the distribution of trapped holes and neutral levels in the oxide layer

Forward and reverse characteristics of irradiated MOSFETs

pMOSFETs biased with Vgs<Vgd during Co60 \u3b3 irradiation have shown substantial differences between the forward and reverse subthreshold characteristics, induced by a non-uniform charge distribution in the gate oxide. Correspondingly, modest differences have been observed in the over-threshold I-V characteristics. After irradiation, the forward subthreshold curves can shift at higher or lower gate voltages than the reverse ones. The former behaviour has been observed in long-channel devices, in agreement with the classical MOS theory and numerical simulations. The latter result has been obtained in short-channel devices, and it has been correlated to a parasitic punch-through conduction mechanism

Negative media portrayals of immigrants increase ingroup favoritism and hostile physiological and emotional reactions

Anti-immigration rhetoric in the mass media has intensified over the last two decades, potentially decreasing prosocial behavior and increasing outgroup hostility toward immigrants, and fostering ingroup favoritism toward natives. We aim to understand the effects of negative and positive discourses about immigration on prosociality at different levels of societal ethnic diversity. In two studies (student sample, nationally representative sample), we conduct a survey and a 3X3 between-subject experiment, including money-incentivized behavioral games measuring prosociality. We manipulate media representations of immigrants and the probability of interacting with immigrants (the latter measuring diversity). Results show that negative news affects prosociality as a function of the probability of interacting with immigrants. Negative portrayals increase altruism and trustworthiness in ethnically homogenous settings relative to unknown and ethnically-mixed contexts. These results are stronger for right-wing and high-prejudice respondents. Moreover, negative media portrayals of immigrants increase the testosterone-cortisol ratio, which is a proxy for proneness to social aggression. Negative news also increases outgroup-related perceived health risk, outgroup anxiety and outgroup threat less in ethnically-homogeneous contexts. Overall, negative portrayals of immigrants generate physiological and emotional hostility toward the outgroup, and ingroup favoritism in economic transactions, possibly determining efficiency losses in ethnically-diverse markets, relative to ethnically-homogeneous markets

Radiation Effects On Ac-coupled Microstrip Silicon Detectors

The radiation hardness of FOXFET biased ac-coupled microstrip detectors, foreseen for the upgraded version of the vertex detectors (SVX') of the CDF experiment, has been studied. The detectors have been irradiated with Co-60 gamma rays with doses up to 1 Mrad. Two basic effects have been investigated: a variation of the switching voltage up to 100% due to oxide charge accumulation and Si/SiO2 interface trap formation, and a 12-fold increase of the total leakage current, likely to come from surface damage. Moreover, a 10-fold decrease of the FOXFET dynamic resistance is observed at low gate bias. Post-irradiation annealing effects at room temperature of the electrical detector parameters are currently under investigation, in particular on a single shot 1 Mrad irradiated device. Recovery phenomena toward the pre-irradiation values are observed only for the switching voltage due to the annealing of trapped oxide charge

Forward and reverse characteristics of irradiated MOSFET's

pMOSFETs biased with Vgs<Vgd during Co60 gamma irradiation have shown substantial differences between the forward and reverse subthreshold characteristics, induced by a non-uniform charge distribution in the gate oxide. Correspondingly, modest differences have been observed in the over-threshold I-V characteristics. After irradiation, the forward subthreshold curves can shift at higher or lower gate voltages than the reverse ones. The former behaviour has been observed in long-channel devices, in agreement with the classical MOS theory and numerical simulations. The latter result has been obtained in short-channel devices, and it has been correlated to a parasitic punch-through conduction mechanism

E-beam curing of epoxy based blends in order to produce high performance composites

In this work, blends of a difunctional epoxy monomer and a thermoplastic toughening agent are E-beam irradiated at two different dose rates and two different total absorbed doses. The influence of the processing conditions on the thermal properties and on the morphology of the obtained matrices has been investigated. In particular, it is shown how the increase of the dose rate causes an increase of the temperature during irradiation, thus inducing a simultaneous thermal and radiation curing. On the contrary, at low-dose rate the system mainly undergoes to radiation curing, thus making the cured material very sensible to a post-irradiation thermal treatment with a significant improvement of the thermal properties

Radiation-induced depassivation of latent plasma damage

Plasma treatments are widely used in microelectronic industry but they may leave some residual passivated damage in the gate oxides at the end of the processing. The plasma-induced damage can be amplified by metal interconnects (antenna) attached to the gate during the plasma treatments. Ionising radiation reactivates this latent damage, which produces enhanced oxide charge and Si/SiO2 interface state density. Two CMOS technologies have been investigated, with 5 and 7 nm gate oxides. Threshold voltage shifts, transconductance decrease, and interface traps build-up are always larger for plasma damaged devices than for reference devices