New insights in polarity-dependent oxide breakdown for ultrathin gate oxide

In this work, a quantitative analysis is applied to resolve the newly reported polarity-dependent charge-to-breakdown (Q/sub BD/) data from thick oxides of 6.8 nm down to ultrathin oxides of 1.9 nm. Three independent sets of Q/sub BD/ data, i.e., n/sup +/poly/NFET stressed under inversion and accumulation, and p/sup +/ poly/PFET under accumulation are carefully investigated. The Q/sub BD/ degradation observed for p-type anodes, either poly-Si or Si-substrate, can be nicely understood with the framework of maximum energy released by injected electrons. Thus, this work provides a universal and quantitative account for a variety of experimental observations in the time-to-breakdown (T/sub BD/) and Q/sub BD/ polarity-dependence of oxide breakdown.     

Influence of different carbon nanostructures on the electrocatalytic activity and stability of Pt supported electrocatalysts

Commercially available graphitized carbon nanofibers and multi-walled carbon nanotubes, two carbon materials with very different structure, have been functionalized in a nitric–sulfuric acid mixture. Further on, the materials have been platinized by a microwave assisted polyol method. The relative degree of graphitization has been estimated by means of Raman spectroscopy and X-ray diffraction while the relative concentration of oxygen containing groups has been estimated by X-ray photoelectron spectroscopy, which resulted in a graphitic character trend: Pt/GNF > Pt/F-GNF ? Pt/MWCNT > Pt/F-MWCNT. Transmission electron microscopy showed that the Pt particle size is around 3 nm for all samples, which was similar to the crystallite size obtained by X-ray diffraction. The activity towards electrochemical reduction of oxygen has been quantified using the thin-film rotating disk electrode, which has shown that all the samples have a better activity than the commercially available electrocatalysts. The trend obtained for the graphitic character maintained for the electrochemical activity, while the reverse trend has been obtained for the accelerated ageing test. Long-term potential cycling has demonstrated that the functionalization improves the stability for multi-walled carbon nanotubes, at the cost of decreased activity.     

VVBGC demonstration plant activities at Värnamo

The biomass-to-syngas demonstration activities of the EC Framework 6 CHRISGAS Project were originally one of the cornerstones of the project and planned to take place at the 18 MW (thermal) demonstration plant in Värnamo, Sweden. This plant was originally built by the Swedish utility, Sydkraft AB, in the first part of the 1990s as an IGCC combined heat and power plant. The plant was acquired by Växjö Värnamo Biomass Gasification Centre AB (VVBGC) from Sydkraft in 2004 for the purpose of performing the test work and demonstration activities within the CHRISGAS project after a rebuild to syngas version. The required funds for plant modifications to syngas version, as well as operation costs were not covered under the CHRISGAS project grants, but were to be applied for elsewhere.The company VVBGC AB, now owned by the holding company of Linnæus University, was founded during the course of the project and new staff were recruited to head the rebuild project and be responsible of the operation of the plant within the CHRISGAS demonstration program.After a thorough status review of the plant and any necessary repair work three hot test campaigns of the existing IGCC plant were carried out. The results of this testing is reported in this paper.     

A new approach to analyze the degradation and breakdown of thin SiO2 films under static and dynamic electrical stress

A test procedure, which provokes the oxide breakdown in two stages, is proposed to analyze the degradation and breakdown of thin SiO ₂ films. This procedure can partially overcome the problems associated with dynamic tests and allows a direct comparison of static and dynamic stresses. The analysis of the data obtained using the proposed method has allowed us to conclude that the oxide breakdown is strongly affected by the degradation induced at the beginning of the test. This result provides a high sensibility to the method, helping it to study the oxide degradation under tests closer to operation conditions keeping reasonable testing times     

Active feedback regulation of a Michelson interferometer to achieve zero-background absorption measurements

An active phase-controlling scheme based on a proportional-integral-derivative-controlled piezoelectric transducer is presented with the purpose of stabilizing a quasi-zero-background absorption spectrometer. A fiber-based balanced Michelson interferometer is used, and absorption due to a gas sample in one of its arms results in an increased light signal to a detector, which otherwise, thanks to destructive interference, experiences a very low light level. With the presented approach, the sensitivity of already potent absorption measurement techniques, e.g., based on modulation, could be improved even further.     

Successive oxide breakdown statistics: correlation effects, reliability methodologies, and their limits

This paper deals with the statistics of successive oxide breakdown (BD) events in MOS devices. Correlation effects between these successive events are experimentally related to the statistics of BD current jumps, thus suggesting that they are related to lateral propagation of the BD path. The application of the successive BD theory to chip reliability assessment is discussed. Several failure criteria and the related reliability methodologies are considered and some of their limits are established.     

The effects of device dimensions on the post-breakdown characteristics of ultrathin gate oxides

The effects of transistor channel length and width on post breakdown (BD) characteristics have been carefully investigated. As channel-length decreases, we have found that the probability of hard breakdown (HBD) increases and the soft breakdown (SBD) stability time decreases. However, these two quantities are found to be relatively insensitive to the channel width for long channel-length devices. Since SBD is unstable and finally causes the device failure, the so-called HBD prevalence ratio methodology has limitations which are particularly important in short-channel length devices. Our findings indicate that dimensional effects should be properly taken into account in the consideration of circuit reliability and for the application of any post-BD methodology.     

Least-squares support vector machines modelization for time-resolved spectroscopy

By use of time-resolved spectroscopy it is possible to separate light scattering effects from chemical absorption effects in samples. In the study of propagation of short light pulses in turbid samples the reduced scattering coefficient and the absorption coefficient are usually obtained by fitting diffusion or Monte Carlo models to the measured data by use of numerical optimization techniques. In this study we propose a prediction model obtained with a semiparametric modeling technique: the least-squares support vector machines. The main advantage of this technique is that it uses theoretical time dispersion curves during the calibration step. Predictions can then be performed by use of data measured on different kinds of sample, such as apples.     

Clinical system for interstitial photodynamic therapy with combined on-line dosimetry measurements

A system for interstitial photodynamic therapy with delta-aminolaevulinic acid and multiple optical fibers has been developed. The system enables photodynamic treatment of large embedded tumor volumes and utilizes real-time measurements to allow on-line dosimetry. Important parameters such as light fluence rate, sensitizer fluorescence intensity, and changes in local blood oxygen saturation are measured with the same fibers that deliver the therapeutic light. Data from the first clinical treatments on nodular basal cell carcinomas indicate a major treatment-induced light absorption increase, rapid sensitizer photobleaching, and a relatively constant global tissue oxygen saturation level during the treatment.     

On Voltage Acceleration Models of Time to Breakdown—Part II: Experimental Results and Voltage Dependence of Weibull Slope in the FN Regime

Based on the methodologies and experimental findings presented in Part I, we demonstrate the general applicability of the T _BD exponential law of reciprocal voltage, T _BD ~ exp(C/VG), in comparison with the T _BD power-law model for SiO₂-based dielectrics stressed in the FN regime. This is done for a wide range of oxide thicknesses and stressed in a wide range of stress voltages and temperatures. We also analyze the consistency of voltage acceleration models with the voltage dependence of the Weibull slope. This is done considering the failure percentile dependence of voltage acceleration and can explain the voltage-independent Weibull slopes reported for ultrathin oxides in the DT regime and the voltage-dependent Weibull slopes reported for thick oxides stressed in the FN regime. This paper demonstrates how the application of complementary analysis methodologies to a complete experimental database allows reaching sound conclusions about the voltage acceleration model of oxide breakdown, thus solving a long lasting controversy.