Collapse of MOSFET drain current after soft breakdown

Gate-oxide soft breakdown (SB) can have a severe impact on MOSFET performance even when not producing any large increase of the gate leakage current. The SB effect on the MOSFET characteristics strongly depends on the channel width W: drain saturation current and MOSFET transconductance dramatically drop in transistors with small W after SB. As W increases, the SB effect on the drain current fades. The drain saturation current and transconductance collapse is due to the formation of an oxide defective region around the SB spot, whose area is much larger than the SB conductive path. Similar degradation can be observed even in heavy ion irradiated MOSFETs where localized damaged oxide regions are generated by the impinging ions without producing any increase of gate leakage current.     

Ionising radiation and electrical stress on nanocrystal memory cell array

In this work, we have investigated the effects of irradiation and electrical stress of nanocrystal memory cell arrays. Heavy ion irradiation has no or negligible immediate effects on the nanocrystal MOSFET characteristics, and on the programming window of the cells. By electrically stressing irradiated device, we see accelerated oxide breakdown similar to that previously observed on conventional thin gate oxide MOS capacitors, but no appreciable change of the degradation kinetics in terms of programming window closure and shift. The accelerated breakdown is ascribed to the degradation of the oxide–nitride–oxide (ONO) layer used as control oxide after exposure to ionising irradiation.     

Na+,K(+)-ATPase of human placenta during gestational hypertension: a biochemical-biophysical study

1. Na+,K(+)-ATPase is the membrane enzyme catalysing the active transport of Na+ and K+ across the plasma membrane of animal cells. A reduced activity of Na+,K(+)-ATPase has been described in gestational hypertension in a variety of cell types, in agreement with the hypothesis that gestational hypertension can induce membrane transport modifications similar to those reported for essential hypertension. The causes of the reduced Na+,K(+)-ATPase activity are still debated. 2. The aim of the present work was to investigate the molecular mechanism of the reduced enzymic activity in gestational hypertension using as a model Na+,K(+)-ATPase purified from human placenta. Na+,K(+)-ATPase obtained from term placentas of eight healthy pregnant women and eight age-matched women with gestational hypertension was purified as previously described. 3. We observed in gestational hypertension: (i) a significant increase in the activation energies above transition temperature; (ii) a significant decrease in the fluorescence polarization of 1-(4-trimethylaminophenyl)-6-phenyl-1,3,5-hexatriene (i.e. increased fluidity) and an increase in the mean lifetime (modified hydrophobicity); (iii) a lower Kq, suggesting an enzymic structural modification; and (iv) an increased mean lifetime and rotational relaxation time of pyrene isothiocyanate, indicating a modified ATP binding site.     

Lifetime estimation of analog circuits from the electrical characteristics of stressed MOSFETs

In this work, the impact of dielectric degradation in the MOSFET electrical characteristics after different levels of Fowler-Nordheim (FN) stress has been studied. A decrease in I_SAT and an increase of V_T have been observed. The interface trap density has been extracted from the sub-threshold slope of I_D–V_GS curves. The results show a direct relation between the generated interfacial traps and the observed changes in saturation current and threshold voltage. The wear out effects in the devices have been extrapolated to operation voltages, pointing out that the transistors can fulfill the reliability criteria, even when working in analog applications.     

Degradation of static and dynamic behavior of CMOS inverters during constant and pulsed voltage stress

We study the degradation of CMOS inverters under DC and pulsed stress conditions before the occurrence of the gate oxide breakdown. Our results show an overall speed reduction, caused by the transistor drain current drop, and a leftward shift of the inverter voltage transfer characteristics, due to a larger degradation of the PMOSFET as compared to the NMOSFET. We attribute this behavior to the build-up of defects/trapped charge featuring a different kinetics in P- and N-type MOSFETs.     

Gestational hypertension plasma and human umbilical vein endothelial cells: an in vitro study

A case of metastatic dermatofibrosarcoma protuberans (DFSP) in a 47-year-old woman is presented. Dermatofibrosarcoma protuberans occasionally recurs, but rarely metastasizes. The patient underwent local removal of the nuchal tumor by a general practitioner, followed by a rapid recurrence. She underwent total removal of the tumor and a diagnosis of spindle cell sarcoma was made after an incisional biopsy was performed. This lesion had both a typical DFSP-like area and a fibrosarcoma (FS)-like area. After 7 years, an abnormal lung shadow was observed and a segmental lung resection was performed. Histologically, the lung tumor was similar to the FS-like area in the nuchal tumor. Confirming CD34 expression in the tumor cells, this lung tumor was diagnosed as metastatic DFSP. Usually CD34 expression is unique to DFSP but almost negative in FS-like areas. In the present case, the FS-like area in the nuchal tumor showed decreased CD34 reactivity, as previously reported, but the FS-like area in the metastatic tumor still widely preserved CD34 expression. The presented case suggests that the FS-like area in DFSP is histogenetically different from typical FS or malignant fibrous histiocytoma.     

Ionising radiation effects on MOSFET drain current

We have investigated the radiation effect on MOSFET performances due to the incidence of a few ions in the gate area. We present new experimental evidence that a single ion may lead to the MOSFET drain current collapse, due to the formation of a localized oxide damaged region over a large portion of the channel width, well before the breakdown onset. We call these phenomena single event drain current collapse (SEDC²). This effect is evident in devices with small channel width (W), i.e., comparable to the size of damaged region, and fades as W increases over the size of the ion damaged region.     

Total dose dependence of radiation-induced leakage current in ultra-thin gate oxides

Radiation-induced leakage current (RILC) has been studied on ultra-thin gate oxides (4 and 6 nm) irradiated with 8 MeV electrons. Both RILC and stress-induced leakage current (SILC) have been fitted with the same Fowler–Nordheim law, suggesting that RILC and SILC have similar conduction mechanisms. The RILC dependence from total dose during irradiation has been analysed and compared with the SILC dependence from the cumulative injected charge. Different growth laws of RILC and SILC have been found in the two cases. The intensity of positive and negative RILC also depends on the applied gate bias voltage during irradiation, probably reflecting different distributions of the oxide traps mediating the trap assisted tunnelling. Finally, we have presented the first evidence of a quasi-breakdown phenomenon due to ionizing radiation.     

Biochemical-morphological modifications of platelet membranes during pregnancy-induced hypertension

Progesterone profiles were monitored in goats housed in single (n = 9) or group (n = 14) pens during winter (JJA) and spring (SON). Normal cycles (n = 97) were < or = 30 days. Extended cycles (n = 45) were > 30 days and, except for one cycle with a persistent corpus luteum, had periovulatory periods of 10 to 20 days (n = 29) or averaging 65.1 days in length (n = 15), mostly characterised by recurrent oestrus and/or occasional transient rises in progesterone. The proportion of normal cycles occurring in winter was 87.5% (28/32) and 77.7% (42/54) for goats in single and group pens respectively, falling to 62.5% (15/24) and 37.5% (12/32) respectively in spring. The distribution of normal vs extended cycles according to season was significant (P < 0.05, single; P < 0.001 group pens). Goats housed communally experienced a greater fall in the percentage of normal cycles in spring, possibly due to increased stress associated with group feeding. Within each season, however, housing per se did not influence the distribution of normal vs extended cycles. For normal cycles, Harvey's Analysis of Variance showed that season was significantly associated with length of the periovulatory period (3.99 days (JJA) vs 5.79 days (SON); P < 0.001), oestrus detection rate (87% (JJA) vs 55% (SON); P < 0.01) and oestrus duration (1.94 days (JJA) vs 1.13 days (SON); P < 0.05). In contrast, luteal phase length was not affected by season, but was significantly associated with housing (16.93 days (single pens) vs 18.32 days (group pens); P < 0.01). The reduction in ovarian activity observed in spring may reflect a seasonal reduction in fertility, possibly linked with increasing temperature and photoperiod.     

Thermal stress effects on Dye-Sensitized Solar Cells (DSSCs)

Since the DSSCs gain heat during exposure to sunlight increasing its own temperature, we have studied the role of temperature on the degradation of DSSCs. We have performed pure thermal stresses keeping the devices at a constant temperature inside a climatic chamber and monitoring the electrical parameters during stress. We found that temperature alone strongly impacts on the DSSC performances, enhancing the degradation of the sensitizer and then reducing the photo-generated current.