In the context of an assessment of the physical mechanisms governing thin oxide degradation, this paper reports an experimental investigation of anode hole injection (AHI) at low gate voltages (
V
G) ...and of its correlation to SILC generation. A new technique based on carrier separation measurements is introduced to interpret the behavior of the gate current (
I
G) during constant
V
G stress experiments. Our results indicate that AHI is still operative at lower |
V
G| than previously thought.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
We present density-functional theory calculations of the optical absorption spectra of silica glass for temperatures up to 2400 K. The calculated spectra exhibit exponential tails near the ...fundamental absorption edge that follow the Urbach rule in good agreement with experiments. We discuss the accuracy of our results by comparing to hybrid exchange correlation functionals. We show that the Urbach rule holds in a frequency interval where optical absorption is Poisson distributed with very large statistical fluctuations. In this regime, a direct relation between the optical absorption coefficient and electronic density of states is derived, which provides a link between photoemission and absorption spectra and is used to determine the lower bound to the Urbach frequency regime.
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CMK, CTK, FMFMET, IJS, NUK, PNG, UM
The effect of various HF-based etching processes on the laser damage resistance of scratched fused silica surfaces has been investigated. Conventionally polished and subsequently scratched fused ...silica plates were treated by submerging in various HF-based etchants (HF or NH{sub 4}F:HF at various ratios and concentrations) under different process conditions (e.g., agitation frequencies, etch times, rinse conditions, and environmental cleanliness). Subsequently, the laser damage resistance (at 351 or 355 nm) of the treated surface was measured. The laser damage resistance was found to be strongly process dependent and scaled inversely with scratch width. The etching process was optimized to remove or prevent the presence of identified precursors (chemical impurities, fracture surfaces, and silica-based redeposit) known to lead to laser damage initiation. The redeposit precursor was reduced (and hence the damage threshold was increased) by: (1) increasing the SiF{sub 6}{sup 2-} solubility through reduction in the NH4F concentration and impurity cation impurities, and (2) improving the mass transport of reaction product (SiF{sub 6}{sup 2-}) (using high frequency ultrasonic agitation and excessive spray rinsing) away from the etched surface. A 2D finite element crack-etching and rinsing mass transport model (incorporating diffusion and advection) was used to predict reaction product concentration. The predictions are consistent with the experimentally observed process trends. The laser damage thresholds also increased with etched amount (up to {approx}30 {micro}m), which has been attributed to: (1) etching through lateral cracks where there is poor acid penetration, and (2) increasing the crack opening resulting in increased mass transport rates. With the optimized etch process, laser damage resistance increased dramatically; the average threshold fluence for damage initiation for 30 {micro}m wide scratches increased from 7 to 41 J/cm{sup 2}, and the statistical probability of damage initiation at 12 J/cm{sup 2} of an ensemble of scratches decreased from {approx}100 mm{sup -1} of scratch length to {approx}0.001 mm{sup -1}.
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BFBNIB, DOBA, FZAB, GIS, IJS, IZUM, KILJ, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBMB, UILJ, UKNU, UL, UM, UPUK
Objective
To assess the impact of obesity on the likelihood of remaining in midwife‐led care throughout pregnancy and childbirth.
Design
Secondary analysis of data from a prospective cohort study.
...Setting
Dutch midwife‐led practices.
Population
A cohort of 1369 women eligible for midwife‐led care after their first antenatal visit.
Methods
First‐trimester body mass index (BMI) was calculated as weight measured at booking divided by height squared. Obstetric data were retrieved from medical records. Multiple logistic regressions were performed to examine the effects of BMI classification on midwife‐led pregnancies and childbirths.
Main outcome measures
Percentages of women remaining in midwife‐led care throughout pregnancy and throughout childbirth.
Results
Of women in obesity classes II and III, 55% remained in midwife‐led care throughout pregnancy and 30% remained in midwife‐led care throughout birth. Compared with women of normal weight, women in obesity classes II and III had fewer midwife‐led pregnancies (OR 0.38, 95% CI 0.21–0.69), and women who were overweight or in obesity class I had fewer midwife‐led childbirths (OR 0.63, 95% CI 0.44–0.90; OR 0.49, 95% CI 0.29–0.84, respectively). Compared with women of normal weight, women who were obese had higher referral rates for hypertensive disorders (4 versus 14%), prolonged labour (4.6 versus 10.4%), and intrapartum pain relief (4 versus 10.4%). The women who were eligible for midwife‐led birth and who were overweight or obese, had no more urgent referrals than women of normal weight. Women who were obese and who completed a midwife‐led birth had no more adverse outcomes than women of normal weight, with the exception of higher rates of large for gestational age (LGA) babies (>97.7 centile; 12.1%, versus 1.9% in normal weight and versus 3.3% in overweight women).
Conclusions
Although fewer women who were obese remain in midwife‐led care during pregnancy and childbirth, there was no increased risk of unfavourable birth outcomes for women who were obese and eligible for a midwife‐led birth when compared with women of normal weight. This indicates that when primary care midwives use a risk assessment tool throughout pregnancy and childbirth they are able to safely assign women who are obese to either midwife‐led or obstetrician‐led care.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
The physics of impact ionization generated substrate current in 0.1 μm nMOSFET's technologies is clarified by comparison of experiment and full-band Monte Carlo (MC) simulation for a wide range of ...biases. Quasiballistic transport is confirmed. It is shown for the first time that these devices allow extraction of ionization probabilities near threshold from substrate current measurements.
This paper analyzes in detail the generation of interface states (N/sub it/) and stress-induced leakage current (SILC) during channel hot electron (CHE) stress experiments in the context of a ...possible hydrogen/deuterium (H/D) isotope effect. Our results show that N/sub it/ generation is related to the hydrogen release (HR) at the Si-SiO/sub 2/ interface at relatively high V/sub G/ where a large isotope effect is found. Instead, for gate voltages (V/sub G/) favorable for hot hole injection (HHI) the N/sub it/ creation becomes a unique function of hole fluence and the isotope effect disappears. In the studied stress conditions, we found no experimental evidence supporting a causal relation between SILC generation and HR because no isotope effect is observed even when the corresponding N/sub it/ measurements reveal a very different D/H release rate. Similar to N/sub it/ generation, we found that SILC becomes a unique function of hole fluence at low stress V/sub G/. Relevant implications and extensions of these results to the Fowler-Nordheim (FN) tunneling stress conditions are discussed in Pt. II.
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